Environmentally friendly spinning polymer solution and nanofiber nonwoven textile based on it

Abstract

The environmentally friendly spinning polymer solution for generating a nanofibrous structure in an electrostatic field includes a polymer, a solvent system, and possibly other additives to modify the conductivity of the solution. The polymer at a concentration of 10 to 20 wt% is at least one polymer from the group consisting of polylactic acid (PLA), polysulfone (PSU), polyurethane (PU), and cellulose acetate (CA). The solvent system is a green solvent system comprising at least two of the green solvents selected from the group consisting of cyclopentanone (CPO), ethyl lactate (EL), methyl lactate (ML), and acetone. The nanofibrous nonwoven fabric, which can be prepared by spinning the mentioned spinning polymer solution, contains nanofibers with an average diameter of 100 to 500 nm.

Description

[0001] ENVIRONMENTALLY FRIENDLY SPINNING POLYMER SOLUTION AND NANOFIBRE NONWOVEN TEXTILE BASED ON IT

[0002] Field of the invention

[0003] The technical solution relates to an environmentally friendly spinning polymer solution and a nanofibrous nonwoven textile based on this solution.

[0004] State-of-the-art

[0005] The main component of polymer solutions for the fabrication of nanofibres in an electrostatic field are solvents, which usually contribute to the solution by more than 70% relative to the polymer. Toxic organic solvents are generally used, the most common ones being dimethylformamide (DMF), chloroform, dimethylacetamide (DMAc), dichloromethane (DCM), tetrahydrofiiran (THF), hexafluoro-2-propanol (HFIP) or N-methyl-2-pyrrolidone (NMP).

[0006] These are highly volatile solvents, which is an advantageous property for use in spinning solutions, but on the other hand, their toxicity to human health (especially carcinogenic and mutagenic effects) and the environment presents a risk, especially for workers preparing and handling these solutions. Therefore, there are efforts to reduce the use of these hazardous solvents and replace them with solvents that are more acceptable to the environment and human health, referred to as green solvents.

[0007] The green, environmentally acceptable solvents being considered as possible substituents for DMF and the other solvents mentioned above include, for example Cyrene (dihydrolevoglucosenone), y-valerolactone (GVL), Rhodiasolv Polarclean (methyl 5- (dimethylamino)-2-methyl-5-oxopentanoate), N-butylpyrrolidinone (NBP), cyclopentanone (CPO), ethyl lactate (EL) or methyl lactate (ML). The environmental acceptability of solvents can be evaluated by a GSK score that considers several categories, including human health, reactivity, VOC (volatile compounds) emissions, impact on air quality, recyclability, etc.

[0008] Although these green solvents are well suited for the preparation of solutions of many polymers, including polylactic acid (PL A), poly sulfone (PSU), or polyurethanes (PU), solutions prepared using them are unsuitable for electrospinning. A balanced solvent system comprising at least one, but usually at least two, green solvents should be used to prepare a spinning polymer solution processable into a nanofibrous material with a minimum of defects and a mean nano fibres diameter of up to 500 nm. The most attention is paid to the biopolymer PLA. This polymer is well spinnable to fine nanofibres with a minimum of defects using solutions based on DMF, which is classified as a toxic solvent. To reduce toxicity, some portion of the DMF in the solutions has been substituted with other solvents, such as acetone. However, as the ratio of acetone in the combined acetone / DMF solvent system increases, the nanofibres' diameter also increases. The diameter of PL A nanofibres is already around 750 nm when pure acetone is used.

[0009] Also, the Chinese patent CN116240677 describes the preparation of PLA-based composite nanofibres generated from a spinning solution of reduced toxicity, where the solvent system contains DMF and the green solvent ethyl acetate (EA) in a ratio of 9-49 / 21 (DMF / EA). EA has a better environmental acceptability score than acetone, but it again replaces only part of the toxic DMF.

[0010] Principle of the technical solution

[0011] The environmentally friendly spinning polymer solution, according to the presented technical solution, contributes to eliminating the shortcomings mentioned above. The objective of the invention is based on a spinning solution comprising, in addition to the polymer from the group containing polylactide (PLA), poly sulfone (PSU), polyurethane (PU) and cellulose acetate (CA) at a concentration of 10 to 20 wt%, a green solvent system. The solvent system comprises at least two of the green solvents selected from the group consisting of cyclopentanone (CPO), ethyl lactate (EL), methyl lactate (ML), and acetone.

[0012] Preferably, the main solvent of the green solvent system with a proportion of more than 50 wt% is one of the solvents from the group comprising cyclopentanone (CPO), ethyl lactate (EL) and methyl lactate (ML).

[0013] The green solvent system preferably comprises one or a mixture of conductivity-modifying additives from the group consisting of tetraethylammonium bromide, citric acid and sodium tetraborate decahydrate. This conductivity-modifying additive or mixture of additives is present in the solvent system at a concentration of 0.3 to 3 wt %.

[0014] The nanofibrous nonwoven textile, according to the present invention, comprises nanofibres with a mean diameter of 100 to 500 nm, based on an environmentally friendly spinning polymer solution which, in addition to at least one polymer selected from the group consisting of polylactide (PLA), polysulfone (PSU), polyurethane (PU), and cellulose acetate (CA) at a concentration of 10 to 20 wt%, includes a green solvent system comprising at least two of the green solvents selected from the group consisting of cyclopentanone (CPO), ethyl lactate (EL), methyl lactate (ML), and acetone. The main benefit of the disclosed invention is that the environmentally friendly spinning polymer solutions for preparing nanofibres in the electrostatic field, according to the invention, are based on solvent systems containing neither DMF nor any of the other toxic solvents mentioned above. The fundamental (majority) component of the solvent system is always a green solvent from the group, including cyclopentanone (CPO), ethyl lactate (EL), methyl lactate (ML), which is combined with another solvent from the aforementioned group of green solvents, possibly also with acetone.

[0015] Specifically, a polysulfone spinning solution can be prepared using a solvent system based on a combination of CPOZEL at a weight ratio of 65 to 95 / 35 to 5, ideally 70 / 30, which is spinnable in an electrostatic field to nano fibres having a mean diameter of 100 to 300 nm after conductivity modification by the addition of a quaternary ammonium salt - tetraethylammonium bromide.

[0016] The same CPOZEL solvent system with a component weight ratio of 70 to 90 / 30 to 10, ideally 80 / 20, can be used for polyurethane solutions spinnable to nanofibres with a mean fibre diameter of 100 to 300 nm. The conductivity of both types of polymer solutions (PSU and PU) can be modified not only with tetraethylammonium bromide but also with a combination of citric acid and sodium tetraborate decahydrate at a weight ratio 3 / 1.

[0017] The two-component solvent system CPO / ML can also be used to prepare solutions spinnable in the electrostatic field to polymer nanofibres based on PSU or PU. For PSU, the CPO / ML combination can be used at a component weight ratio of 70 to 90 / 30 to 10, ideally 80 / 20. The solution, conductivity modified by adding a quaternary ammonium salt - tetraethylammonium bromide, can be spun to nano fibres with a mean diameter of 150 to 300 nm. The same CPO / ML solvent system at a component weight ratio of 70 to 90 / 30 to 10, ideally 80 / 20, can be used for polyurethane spinning solutions spinnable to nanofibres with a mean fibre diameter of 100 to 300 nm. The conductivity of both types of polymer solutions (PSU and PU) can be modified not only with quaternary ammonium salt but also with a combination of citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1.

[0018] The three-component solvent system CPO / acetone / EL can be used to prepare polymer solutions spinnable in an electrostatic field based on PLA. The conductivity of such solutions is modified by a combination of citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1 or by adding a quaternary ammonium salt, tetraethylammonium bromide. Using solutions with a solvent system component ratio (CPO / acetone / EL) of 50 to 70 / 35 to 20 / 15 to 10, ideally 58 / 30 / 12, a nano fibrous structure with a mean fibre diameter of 100 to 300 nm can be obtained. A PL A solution with a three-component solvent system CPO / acetone / ML in a ratio of 50 to 70 / 35 to 20 / 15 to 10, ideally 58 / 30 / 12, which conductivity is enhanced by a combination of citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1 or by the addition of a quaternary ammonium salt - tetraethylammonium bromide, is spinnable in an electrostatic field to very fine nanofibers with a mean diameter of 90 to 250 nm.

[0019] Applying a two-component solvent system based on an EL / acetone combination at a weight ratio of 60 to 90 / 40 to 10, ideally 70 / 30, a spinning solution of polylactic acid can be prepared which, after conductivity modification by the addition of a combination of citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1, is spinnable in an electrostatic field to nanofibers having a mean fibre diameter of 150 to 450 nm.

[0020] Similarly, a PLA-based polymer solution spinnable in an electrostatic field to a nanofibrous material with a mean fibre diameter of 200 to 500 nm can be prepared from a two-component ML / acetone solvent system at a component weight ratio of 60 to 90 / 40 to 10, ideally 70 / 30. The conductivity of the solutions is again adjusted by the combination of citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1 or by adding a quaternary ammonium salt - tetraethylammonium bromide.

[0021] Green solvent-based solutions spinnable in an electrostatic field can also be prepared from a combination of polymers, such as a mixture of PLA and cellulose acetate (CA) at a weight ratio of 1 / 1. The solution's conductivity is modified by adding a quaternary ammonium salt - tetraethylammonium bromide or a combined conductive additive based on citric acid and sodium tetraborate decahydrate at a weight ratio of 3 / 1. The solution is spinnable in an electrostatic field to nanofibrous textile having a fibre diameter of 150 to 300 nm.

[0022] Examples of technical solution implementation

[0023] Example 1

[0024] Fourteen per cent (by weight) polymer solution prepared from Ultrason S 6010 poly sulfone (BASF) dissolved in the cyclopentanone / ethyl lactate solvent combination at the weight ratio of 70 / 30, which conductivity is adjusted to an optimum value of 110 pS / cm by the addition of 0.8 wt% of tetraethylammonium bromide, is processable in an electrostatic field to a nanofibrous nonwoven textile with minimum defects and a mean fibre diameter of 225±85 nm. Example 2

[0025] Twelve per cent (by weight) polymer solution prepared from Desmopan 2590A polyurethane (Bayer) dissolved in a combined solvent of cyclopentanone / ethyl lactate at a weight ratio of 80 / 20, which conductivity is adjusted to an optimum value of 130 pS / cm by the addition of 0.8 wt% of tetraethylammonium bromide, is processable in an electrostatic field to a nanofibrous nonwoven textile with a minimum of defects and a mean fibre diameter of 220±90 nm.

[0026] Example 3

[0027] Fourteen per cent (by weight) polymer solution prepared from Ultrason S 6010 poly sulfone (BASF) dissolved in the cyclopentanone / methyl lactate solvent combination at the weight ratio of 70 / 30, which conductivity is adjusted to an optimum value of 110 pS / cm by the addition of 3 wt% of the combination of citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1, is processable in an electrostatic field to a nanofibrous nonwoven textile with minimum defects and a mean fibre diameter of 210±70 nm.

[0028] Example 4

[0029] Ten per cent (by weight) polymer solution prepared from Desmopan 2590A polyurethane (Bayer) dissolved in a combined solvent of cyclopentanone / methyl lactate at a weight ratio of 80 / 20, which conductivity is adjusted to an optimum value of 130 pS / cm by the addition of 0.8 wt% of tetraethylammonium bromide, is processable in an electrostatic field to a nanofibrous nonwoven textile with a minimum of defects and a mean fibre diameter of 200±80 nm.

[0030] Example 5

[0031] Twelve and a half per cent (by weight) polymer solution prepared from Ingeo 4060D polylactic acid (NatureWorks) dissolved in a combined solvent of cyclopentanone / acetone / ethyl lactate at the weight ratio of 58 / 30 / 12, which conductivity is adjusted to an optimum value of 90 pS / cm by the addition of 1.6 wt% of the combined conductive additive based on citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1, is processable in the electrostatic field to a nanofibrous nonwoven textile with minimal defects and a mean fibre diameter of 155±40 nm.

[0032] Example 6

[0033] Twelve and a half per cent (by weight) polymer solution prepared from Ingeo 4060D polylactic acid (NatureWorks) dissolved in a combined solvent of cyclopentanone / acetone / methyl lactate at the weight ratio of 58 / 30 / 12, which conductivity is adjusted to an optimum value of 100 pS / cm by the addition of 1.6 wt% of the combined conductive additive based on citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1, is processable in the electrostatic field to a nanofibrous nonwoven textile with minimal defects and a mean fibre diameter of 125±35 nm.

[0034] Example 7

[0035] Twelve per cent (by weight) polymer solution prepared from Ingeo 4060D polylactic acid (NatureWorks) dissolved in a combined solvent of ethyl lactate / acetone at the weight ratio of 70 / 30, which conductivity is adjusted to an optimum value of 70 pS / cm by the addition of 0.45 wt% of the combined conductive additive based on citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1, is processable in the electrostatic field to a nanofibrous nonwoven textile with minimal defects and a mean fibre diameter of 265±100 nm.

[0036] Example 8

[0037] Twelve and a half per cent (by weight) polymer solution prepared from Ingeo 4060D polylactic acid (NatureWorks) dissolved in a combined solvent of methyl lactate / acetone at the weight ratio of 70 / 30, which conductivity is adjusted to an optimum value of 95 pS / cm by the addition of 0.3 wt% of the combined conductive additive based on citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1, is processable in the electrostatic field to a nanofibrous nonwoven textile with minimal defects and a mean fibre diameter of 365±220 nm.

[0038] Example 9

[0039] Twelve and a half per cent (by weight) polymer solution prepared from Ingeo 4060D polylactic acid (NatureWorks) and cellulose acetate with Mn~30,000 and degree of acetylation ~ 40% (Sigma Aldrich) in a 1 / 1 ratio dissolved in a combined solvent of cyclopentanone / acetone / ethyl lactate at the weight ratio of 55 / 30 / 15, which conductivity is adjusted to an optimum value of 135 pS / cm by the addition of 2.3 wt% of the combined conductive additive based on citric acid and sodium tetraborate decahydrate at the weight ratio of 3 / 1, is processable in the electrostatic field to a nanofibrous nonwoven textile with minimal defects and a mean fibre diameter of 210±80 nm. Industrial applicability

[0040] Nanofibrous nonwovens are currently used in many applications where human or environmental toxicity may be of significant concern. Such applications may include air and water filtration or medical applications such as wound dressings. Therefore, efforts are made to prepare spinning solutions with zero content of toxic organic solvents such as DMF, DMAc, DCM, THF, HFIP, or NMP. The presented technical solution contributes significantly to this effort.

Claims

CLAIMS1. Environmentally friendly spinning polymer solution for the generation of a nanofibrous structure in an electrostatic field, comprising a polymer, a solvent system, and possibly other additives to modify the conductivity of the solution, characterised in that it contains, in addition to the polymer having a concentration of 10 to 20 wt%, which is at least one polymer selected from the group consisting of polylactic acid (PL A), poly sulfone (PSU), polyurethane (PU), and cellulose acetate (CA), a green solvent system comprising at least two of the green solvents selected from the group consisting of cyclopentanone (CPO), ethyl lactate (EL), methyl lactate (ML), and acetone.

2. Environmentally friendly spinning polymer solution, according to claim 1, characterised in that the main solvent of the green solvent system with a concentration in the solvent system of more than 50 wt% is any one of the solvents from the group consisting of cyclopentanone (CPO), ethyl lactate (EL) and methyl lactate (ML).

3. Environmentally friendly spinning polymer solution, according to claim 1, characterised in that, as part of the green solvent system, it further comprises one or a mixture of conductivity modifying additives at a concentration in the solvent system of 0.3 to 3 wt% from the group consisting of tetraethylammonium bromide, citric acid and sodium tetraborate decahydrate.

4. Nanofibrous nonwoven textile, characterised in that it contains nanofibres with a mean diameter of 100 to 500 nm, being a product based on an environmentally friendly spinning polymer solution, which, in addition to a polymer at a concentration of 10 to 20 wt%, that is at least one polymer selected from the group consisting of polylactic acid (PLA), polysulfone (PSU), polyurethane (PU), and cellulose acetate (CA), comprises a green solvent system comprising at least two of the green solvents selected from the group consisting of cyclopentanone (CPO), ethyl lactate (EL), methyl lactate (ML), and acetone.