RU2447207C1 - Method of producing nanofibres from aliphatic copolyamides - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: solution with 15-30 wt % concentration of polyhexamethylene adipine amide and polyhexamethylene sebacinamide copolymer with ratio 60:40 wt % in an alcohol-water mixture with 45-97 vol. % ethanol content is obtained. The solution is filtered and deaerated. The solution is fed through a die hole-electrode in an electric field with strength E=1.5 10⁴-4.0 10⁵ V/m and distance between electrodes of 0.1-0.5 m. Nanofibres are deposited on an oppositely charged electrode with diameter d=50-4500 nm. The fibres form material having high porosity, vapour- and water-permeability, high hydrophilic behaviour and bioinertness.

EFFECT: obtained material can be used to make wound covers, filters for cleaning liquid and gaseous media, matrices for proliferation of stem cells.

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Description

The invention relates to processes for producing nanofibers by electrospinning, in particular nanofibres with a diameter of d = 50-4500 nm from aliphatic copolyamides.

The electroforming method allows to obtain polymer fibers with a diameter of 50 nm to 4500 nm. The high-voltage electric field E, where the jet of solution or melt enters, leads to the polarization of the polymer, the deposition of nanofibers on the opposite electrode (figure 1).

It is known to obtain nanofibers in this way from PVA, PEO, PVP, cellulose derivatives and other polymers. Materials from such fibers are characterized by low density, high porosity, moisture and gas permeability (1, 2, 3).

Patent (4) describes a method for producing porous nanofibers from PE, PP, PS, PA, PVA, PVP, PEO, PMMA, polylactide, polysaccharides. On the example of polylactide it is shown that the distinctive feature of the proposed method is the formation of longitudinal pores in the fibers.

Known methods for producing nanofibers from water-soluble polymers (4); such fibers have low water resistance, high swelling or solubility in aqueous media.

Aliphatic copolyamides consisting of poly-ε-caprolactam and polyhexamethylene adipinamide or poly-ε-caprolactam and polyhexamethylene adipinamide and polyhexamethylene sebacinamide or polyhexamethylene adipinamide and polyhexamethylene sebacinamide are of interest for the preparation of nanofibers by electrospinning, since they dissolve in alcohol-water mixtures.

These polymers are used to produce porous film materials by coagulating the polymer in a “hard” precipitation bath. When molding a copolyamide solution through a slotted die, holding the molded solution on a substrate for the time required for gelation of the polymer, and then precipitating it into water, a film material with pore sizes of 1.0-10.0 μm is obtained (2).

Alcohol-soluble copolyamides are used as adhesives for producing fibers from melts and solutions, for surface treatment of suture threads, etc. (3).

The most interesting for the formation of fibers and films is the copolymer of polyhexamethylene adipinamide and polyhexamethylene sebacinamide (SPA), it has the best film and fiber-forming properties (6).

The solvent for this SPA is an alcohol-water mixture, which makes the molding process environmentally friendly. Materials from this polymer do not contain solvent residues that are harmful to health, retain their performance in aqueous media for a long time.

The production of fibers by electrospinning from a solution of polyamide-6 is described in patent (5), where concentrated (88%) formic acid was used as a solvent [US No. 7618702].

In the above method of producing nanofibers from solutions and, in particular, polyamide solutions, concentrated acids or volatile organic solvents are used, which significantly complicates the process of electrospinning, carries a large environmental load. The specified method is the closest in essence and the achieved result.

An object of the invention and a positive result is the production of nanofibers from an aliphatic SPA by electrospinning, establishing the dependence of the structure of nanofibers on the concentration of the SPA solution and electric field strength, and the production of water-resistant fibers using an environmentally friendly solvent.

This is achieved by obtaining a solution with a concentration of 15-30 wt.% Of a copolymer of polyhexamethylene adipinamide and polyhexamethylene sebacinamide with a ratio of 60:40 wt.% In an alcohol-water mixture with an ethanol content of 45-97 vol.%, Filtering the solution, dehydrating it and feeding it through a die plate into an electric field with a strength of E = 1.5 × 10 ⁴ -4.0 × 10 ⁵ V / m with a distance between the electrodes of 0.1-0.5 m; deposition on the electrode of the opposite sign of nanofibers with a diameter of d = 50-4500 nm.

The optimal ethanol content in the alcohol-water solvent of the copolymer of polyhexamethylene adipinamide and polyhexamethylene sebacinamide is 80 vol.% (Figure 2).

The concentration of the SPA solution, providing the rheological properties necessary for forming the fibers, does not exceed 30 wt.% (Figure 3).

The concentration of SPA in an alcohol-water mixture with an ethanol content of 80 vol.%, Providing stable solutions over time, is 15-25 wt.% (Figure 4).

Forming from SPA solutions with a concentration of 20-30 wt.% Allows you to get fibers that are uniform in cross section and uniform in length (figure 5, 6, 7, 8).

The diameter of the fibers obtained by electrospinning depends on the concentration of the SPA solution and is 50-4500 nm (Fig. 9).

The molding from solutions with a concentration of 20-30 wt.% In an electric field with a strength of E = 1.5 × 10 ⁴ ÷ 4.0 × 10 ⁵ V / m allows you to get fibers that are uniform in cross section and uniform in length (figure 10, eleven).

The method is illustrated in graphic material, where

figure 1 - block diagram of the installation of electrospinning fibers;

1 - high voltage block; 2 - dosing device; 3 - die-electrode; 4 - precipitating electrode; E is the electric field strength; I is the distance between the electrodes;

figure 2 is a diagram of the liquid - solid body solutions of SPA concentration of 15 wt.%; t is the exposure time of the solution at T = 20 ° C, C is the ethanol content in the alcohol-water mixture;

figure 3 - dependence of the viscosity of the solution SPA η from the concentration C; solvent ethanol / water = 80/20;

figure 4 is a diagram of a liquid - solid body of solutions of SPA in a solvent ethanol / water = 80/20; t is the exposure time of the solution at T = 20 ° C, C is the concentration of the SPA solution;

figure 5 - micrographs of SPA fibers obtained from solutions of various concentrations of 10%;

figure 6 - micrographs of SPA fibers obtained from solutions of various concentrations of 20%;

7 is a micrograph of SPA fibers obtained from solutions of various concentrations of 25%;

on Fig - micrographs of SPA fibers obtained from solutions of various concentrations of 30%;

figure 9 - dependence of the diameter of the fiber d from C is the concentration of the SPA solution;

figure 10 is a micrograph of SPA fibers obtained in an electric field with a strength of E = 2.0 × 10 ⁵ V / m;

11 - micrographs of SPA fibers obtained in an electric field with a strength of E = 1.0 × 10 ⁵ V / m

The method is more fully disclosed by examples of its implementation.

Example 1. A copolymer of polyhexamethylene adipinamide and polyhexamethylene sebacinamide (viscosity of a 10% solution in an 80/20 alcohol-water mixture at T = 20 ° C, η = 10 ^-1 Pa ∙ s) is dissolved in an alcohol-water solvent containing 80 vol.% Ethanol, with constant stirring for 1 hour, T = 80 C, the concentration of the solution is 20 wt.%. The solution is filtered through two layers of calico at a pressure of 1 atm, then dehydrated at a pressure of 0.1 atm for 1 hour. The resulting solution is placed in a syringe dispenser equipped with a metal die 20 mm long and 0.6 mm in diameter. The polymer feed rate is 0.2 ml / min. A voltage of 16 kV is applied to the die connected to the cathode of the high voltage generator. The deposition of fibers occurs at the anode. The distance between the cathode and anode is l = 0.16 m. The fibers have an average diameter of 500 nm.

Example 2. A copolymer of polyhexamethylene adipinamide and polyhexamethylene sebacinamide (viscosity of a 10% solution in an 80/20 alcohol-water mixture at T = 20 ° C, η = 10 ^-1 Pa ∙ s) is dissolved in an alcohol-water solvent containing 80 vol.% Ethanol, with constant stirring for 1 hour, T = 80 C, the solution concentration of 15 wt.%. The solution is filtered through two layers of calico at a pressure of 1 atm, then dehydrated at a pressure of 0.1 atm for 1 hour. The resulting solution is placed in a syringe dispenser equipped with a metal die 20 mm long and 0.6 mm in diameter. The polymer feed rate is 0.2 ml / min. A voltage of 16 kV is applied to the die connected to the cathode of the high voltage generator. The deposition of fibers occurs at the anode. The distance between the cathode and anode is l = 0.08 m. The fibers have an average diameter of 200 nm.

Example 3. The copolymer of poly-ε-caprolactam and polyhexamethylene adipinamide polyhexamethylene adipinamide (viscosity of a 10% solution in an alcohol-water mixture 80/20 at T = 20 ° C, η = 10 ^-2 Pa ∙ s) is dissolved in an alcohol-water solvent containing 80 vol.% ethanol, with constant stirring for 1 hour, T = 80 C, a solution concentration of 15 wt.%. The solution is filtered through two layers of calico at a pressure of 1 atm, then dehydrated at a pressure of 0.1 atm for 1 hour. The resulting solution is placed in a syringe dispenser equipped with a metal die 20 mm long and 0.6 mm in diameter. The polymer feed rate is 0.2 ml / min. A voltage of 16 kV is applied to the die connected to the cathode of the high voltage generator. The deposition of fibers occurs at the anode. The distance between the cathode and anode is l = 0.08 m. The fibers have longitudinal defects in the form of droplets.

Thus, as shown above, the effectiveness of the method consists in the selection of an alcohol-soluble aliphatic copolyamide containing polyhexamethylene adipinamide and polyhexamethylene sebacinamide, dissolving it in an alcohol-water mixture containing 80 vol.% Ethanol, feeding a solution containing 20-30 wt.% SPA in an electric field with an intensity E = 1.5 × 10 ⁴ -4.0 × 10 ⁵ V / m.

Literature

1. J. D. Schiffman, C. L. Schauer. Review: Electrospinning of biopolymer Nanofibers and their Applications, Polymer Reviews, v. 48 pp. 317-352, 2008.

2. M. Mulder. Introduction to membrane technology M .: Mir, 1999.

3. RF patent 2039535.

4. US 6,790,528, 2004.

5. US 7,618,702, 2009.

6. O.I. Nachinkin. Polymer microfilters, M., Chemistry, 1985.

Claims (1)

A method of producing nanofibers from aliphatic copolyamides by electrospinning, characterized in that the copolymer of polyhexamethylene adipinamide and polyhexamethylene sebacinamide with a ratio of 60:40 wt.% Is dissolved in an alcohol-water mixture with an ethanol content of 45-97 vol.%; a solution with a concentration of 15-30 wt.% is filtered, dehumidified and fed through a die to an electric field with a strength of E = 1.5 × 10 ⁴ - 4.0 × 10 ⁵ V / m with a distance between the electrodes of 0.1-0, 5 m; by deposition on an electrode of opposite sign, fibers with a diameter of d = 50-4500 nm are obtained.

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