RU2676066C1 - Method of producing filter material and filter material - Google Patents

Abstract

FIELD: manufacturing technology.SUBSTANCE: invention relates to the field of producing high-performance fibrous filter materials. Filter material is a three-layer composition in which one of the layers is made of polymer (polyacrylonitrile) nanofibers obtained by electroforming, and is placed between two reinforcing layers of polymer textiles. Nanofibres, obtained by electrospinning according to the Nanospider technology from a solution of polyacrylonitrile with a concentration of 12.5–13.0 wt. % in dimethylformamide, have a diameter of from 100 to 150 nm. Mass of a unit area of a nanofibrous layer is 4–6 g/m, a filtering material is 134–136 g/m. Resulting material can be used directly, as well as the main filter layer of a set of protective materials for the manufacture of protective clothing.EFFECT: high filtration efficiency of aerosols and comfortable physical and hygienic properties.5 cl, 1 tbl, 2 ex

Description

The invention relates to the field of production of highly efficient nanofibrous filter materials, preferably used for ultrafine air purification from highly dispersed aerosols, and which can be used as the main material and / or as part of a set of protective materials for the manufacture of filtering personal skin protection equipment (protective suits, protective gloves safety shoes).

Currently, there are two scientifically based approaches to the creation of protective filtering clothing based on the use of new materials of the adsorption or membrane type. Obtaining such materials belongs to the field of nanotechnology. In adsorption materials, the working component is a developed bulk porous structure and / or surface of a sorbent in a nanodispersed state. In membrane materials - nanofiber polymer structure. However, at present there are very few such compositions, and there is an urgent need to find new reliable protective filter materials that combine high aerosol filtration efficiency and fairly high physical and hygienic characteristics.

Most existing filtering materials for protective clothing have low air and vapor permeability. So, for example, it is known (patent of the Russian Federation for utility model No. 97375, 09/10/2010) a protective fabric for special-purpose clothing, consisting of interweaving warp and weft threads made of aramid fibers, coated with a polymer composition, characterized in that it is impregnated with a polymer emulsion. The polymer coating composition is based on chlorosulfonated polyethylene, or polychloroprene and butadiene - nitrile rubber, fluororubber, low molecular weight siloxane rubber. The utility model relates to fabrics with high fire resistance and heat resistance, increased water resistance and is intended for the manufacture of clothing to protect against the effects of high temperature, water and other harmful factors when extinguishing fires and conducting rescue operations.

The main disadvantage of this fabric is that clothing made from it and similar fabrics is uncomfortable, since the level of its physical and hygienic characteristics is very low; it has a negative (debilitating) effect on a person with a long stay in it.

Known filtering and sorbing self-degassing material for personal protective equipment against the effects of organophosphorus compounds (RF patent No. 2330717, 08/10/2008), which contains the top layer is a polyurethane or fluoroolefin membrane component, the middle layer comprising an enzyme with the properties of organophosphate hydrolase, immobilized in a buffer acrylate as an sorbent and an antimicrobial substance, and a lower layer made of woven or non-woven cellulose-containing material intended for contact with ozhnym cover, wherein all the layers are glued in binder, which is used as the polymeric solutions (gelatin, starch, polyvinyl alcohol, polyethylene glycol, etc.).

However, the use of chemical catalysts with enzymatic activity in the composition of protective materials leads to a tremendous increase in the cost of the materials themselves, since high concentration of enzymes is required for efficient hydrolysis, and the technology for producing this material, which involves the manufacture and combination of three layers of different nature in one package, is quite complex and highly laborious, requiring the use of specific technological equipment. In addition, this material, in which the top layer is moisture-, air-, and vapor-tight, will not provide sufficient physical and hygienic indicators of personal protective skin products made from it. The developers of the material do not provide these indicators.

In the patent of the Russian Federation No. 2446875 (04/10/2012) for adsorption of hazardous chemical and / or biological materials and chemical and / or biological weapons to increase the filtration efficiency, an adsorption type filter material is proposed. The patent contains a detailed description of the problem of filtering air from hazardous substances and a method for manufacturing the described material. It is indicated that the technical result achieved is to increase the filtration efficiency while providing a high degree of comfort for the user. However, the developers of this material do not provide actual data characterizing the material with respect to its ability to retain any toxic chemicals and no information confirming the high efficiency of aerosol filtration.

Known (RF patent No. 2469866, 12/20/2013) composite laminated rubber-fabric protective material based on nitrile butadiene rubber with a barrier layer, made of a three-layer and consisting of a middle reinforcing layer, on the two sides of which are the outer covering layers, while the middle reinforcing layer is made in the form of a fabric of high strength polyester fiber with thread. The invention is claimed to provide reliable protection of human skin from aerosol and drip penetration of liquid chemical and harmful substances while maintaining increased incombustibility and low surface density. However, information about the efficiency of aerosol filtration and physico-hygienic characteristics are not given in the description either. Obviously, this rubberized material (based on nitrile butadiene rubber) will not provide the required indicators of physical and hygienic properties.

Known (patent of the Russian Federation No. 2390592, 05/27/2010) a protective material that consists of inner layers of non-woven material made of fibers based on polyacrylonitrile filled with solid sorption particles or its mixture with polyurethane and an outer covering and outer underlying reinforcing layers located on both sides of the sorption layers fibrous material. Solid particles of activated carbon, cation exchange resin or anion exchange resin with particle sizes less than 6 microns in the amount of 38-64 wt.% Are used as a filler of sorption layers of nonwoven material. % The sorption layers of the material are reinforced by gluing the outer cover layer and the second outer underlying layer made of viscose-lavsan warp knitted material based on high-strength polyester fiber containing 25-35 wt. % viscose fiber.

It is stated that the technical result of the invention is to provide high vapor and air permeability of the material to remove excess moisture from the surface of the human skin, increasing its hygroscopicity. However, the real vapor permeability given in the description does not exceed 2000 g / m ² for 24 hours, the efficiency of aerosol filtration is not shown.

It should be noted that regardless of the method for producing protective materials based on carbon (activated carbon) and non-carbon (silica gels, zeolites, etc.) sorbents, their common significant disadvantage remains the possibility of desorption of toxic substances, as well as the limited time of protective action (no more than 24 hours) due to the dynamic activity (sorption capacity) of the sorbent.

Known membrane materials obtained using electrospinning methods (electrocapillary or free surface), in which the nanofibrous polymer layer is the filtering component, are more commonly used in the creation of anti-aerosol filters for personal respiratory protection and air and gas purification filters from aerosols of various nature. A common drawback of such materials, limiting the possibility of their wider use, for example, to create personal protective equipment for the skin, is the low mechanical strength.

The proposed technical solution is close in technical essence to the filtering polymeric material and the method for its production (RF patent No. 2492912, 09/20/2013), including electrostatic molding by capillary technology on a grounded metal electrode made in the form of a cylinder, from two working solutions of polysulfone in dichloroethane. The material consists of polysulfone fibers with a diameter of 2.5-4.6 microns and 0.08-0.17 microns with a ratio of the lengths of micron and submicron fibers 1: (17-25) and has a hydrodynamic resistance at a filtration rate of 1 cm / s about 30 Pa The surface density of the material is 27-29 g / m ² . The filtration efficiency for particles with a diameter of 0.3 μm is more than 99.999%. The invention is recommended to be used when creating anti-aerosol filters for personal and collective respiratory protection. The material can also be used in combination with other materials as a topcoat.

In addition to low mechanical strength, the disadvantages of this material and the method of its production include insufficient filtration efficiency during ultrafine air purification from the most dangerous pollutants, which corresponds only to filters of class U15 (according to GOST R 51251-99); the need for the use of toxic dichloroethane and the use of two spinning solutions in a relatively unstable capillary molding technology, which determines the technological and technical complexity of introducing the method into production. In addition, the possibility of using the material as a finishing layer as part of a kit with other materials for the manufacture of personal protective skin products is very doubtful due to the relatively high rates of its surface density (up to 29 g / m ² ) and resistance to air flow (30 Pa), causing insufficient air and vapor permeability of the combined set.

The closest in technical essence, the achieved result and the production method (prototype), is a filtering heat-resistant nanofiber material (RF patent No. 2524936, 08/10/2014), containing an inner working layer and two external protective layers placed on both sides of the working layer, and the working one the layer contains polydiphenylenephthalide fibers with a diameter of 200-400 nm, is made by electrospinning, and has a unit mass of 0.5-3.5 g / m ² , and the protective layers are made of non-woven quartz material. The material is intended for use in high temperature filters.

The disadvantages of this nanofiber material obtained by electroforming from a solution of polydiphenylenephthalide in cyclohexanone are the low level of filtering properties (filtration efficiency not more than 99.93%) and physical and hygienic indicators (unstable to moisture, unpleasant to the touch due to its texture with quartz sand), as well as in insufficient mechanical strength (density of quartz material 6-8 g / m ² ). These shortcomings do not allow its use for the manufacture of filtering means for individual skin protection.

An object of the present invention is to provide a nanofiber nonwoven material having a high filtration efficiency of finely divided aerosols and comfortable physical and hygienic characteristics suitable for the manufacture of protective filtering clothing.

The stated technical problem is solved by using the described filter material, namely: the filter material for protective clothing contains a middle filter layer made of polyacrylonitrile nanofibers and providing the role of a filter component, the upper and lower layers made of non-woven polymer textiles with low surface density, designed to protect the middle filter layer from the negative effects of moisture, providing the material with comfortable physical and hygienic and physical ical properties. This nanofiber filter layer is obtained by electrospinning under specific technological conditions and process parameters, and subsequently subjected to double-sided reinforcement with polymeric textile by lamination, subject to the specified parameters and modes.

The technical result obtained during the implementation of the invention consists in obtaining a highly effective filter material with an aerosol filtration efficiency of at least 99.998% and high physical and hygienic characteristics.

Such values of the indicators ensure the achievement of the necessary and sufficient level of protective and physico-hygienic properties in the material suitable for the manufacture of filtering protective clothing that provides comfortable conditions for humans.

The technical result is achieved by using filter material obtained by the method consisting in the fact that the polyacrylonitrile nanofibers are electrostatically molded in a high voltage electric field of 80 kV created due to the potential difference between the forming and precipitation electrodes, and at the same time the resulting nanofiber is laid on a moving interelectrode space non-woven substrate followed by double-sided reinforcement, characterized in that it is electroformed e is carried out from a solution of polyacrylonitrile in dimethylformamide at a polymer concentration 12,5-13,0 wt. %, a solution viscosity of 1.2-1.4 Pa s, a temperature of 25-30 ° C, a relative humidity of 18-20% and a distance between the forming and precipitation electrodes of 160-180 mm.

The resulting filter material is a three-layer composition in which one of the layers is made of polymer nanofibers, and is placed between two reinforcing layers and characterized in that the layer of the polymer layer is made of polyacrylonitrile fibers with a diameter of 100-150 nm with a density of 4-6 g / m ² .

The resulting filter material has the following characteristics:

- the efficiency of filtering particles with a diameter of 0.3 μm is not less than 99.998%;

- resistance to air flow at a linear speed of 1 cm / s, equal to 280-300 Pa;

- the mass of a unit area of the material, equal to 134-136 g / m ² ;

- vapor permeability equal to 7.0-7.5 kg / m ² day .;

- total thermal resistance in calm air, equal to 0.135-0.140 m ² ° C / W.

If necessary, the filter material of the present invention can be used in combination with other filter materials or supplemented with other coatings or layers, for example, an internal sorption layer.

A method of obtaining the described filter material consists in the fact that the Nanospider NS 4S1000U installation conducts the electroforming of polymer nanofibers in a high voltage electric field created by the potential difference between the forming and precipitation electrodes, and at the same time, the resulting nanofiber is laid on a nonwoven substrate moving in the interelectrode space from spunbond. Polyacrylonitrile is used as a polymer, molding is carried out from a solution of polyacrylonitrile in dimethylformamide at certain values of the polymer concentration in the solution and the viscosity of the solution, the voltage of the electric field in the molding zone and the distance between the forming and precipitation electrodes, as well as temperature and relative humidity. The nanofiber filter layer thus produced is reinforced (laminated) on both sides alternately with Danelli doubler, art. D1VP65, white, with a knitted brushed base and spot application of polyamide glue with a surface density of 65 g / m ² on a Reliant Machinery Powerbond industrial laminator Ltd. ”, Czech Republic. At the same time, the nonwoven substrate is removed from the spunbond. The resulting material was kept in air (dried) at room temperature for 24 hours.

The following are specific examples of the implementation of the claimed method of the invention.

Example 1

Prepare a 12.5% solution of polyacrylonitrile in dimethylformamide with a viscosity of 1.2 Pa s (at 30 ° C) to obtain a nanofiber layer of material with a mass per unit layer area of 4.5 g / m ² .

The resulting solution is applied to the surface of a charged electrode at a carriage speed of 1.2 m / s according to Nanospider technology at a temperature in the molding zone of 25 ° C and a relative humidity of 20%. Electroforming is carried out at an electric field voltage of 80 kV, while the distance between the forming and settling electrodes is 170 mm. Polyacrylonitrile nanofibers formed in the high-voltage field are laid on a non-woven spunbond substrate with a surface density of 90 g / m ² moving at a speed of 0.1 m / min in the interelectrode space at a distance of 0.2 cm from the precipitation electrode. After completion of the electrospinning, the nanofiber polymer layer is coated on top with a light spanbond with a surface density of 15 g / m ² .

Two-stage non-woven material is reinforced on both sides on a Powerbond industrial laminator manufactured by Reliant Machinery Ltd., Czech Republic, with Danelli double layer layers, art. D1VP65, with a knitted brushed base and spot application of polyamide glue, with a surface density of 65 g / m ² , at a temperature of 125 ° C, while carefully removing the layers of spunbond.

The resulting material was kept in air at room temperature for 24 hours.

Example 2

Prepare a 13% solution of polyacrylonitrile in dimethylformamide with a viscosity of 1.4 Pa s (at 30 ° C) to obtain a nanofiber layer of material with a mass per unit layer area of 5.0 g / m ² .

To this end, in contrast to Example 1, the resulting solution is applied to the surface of a charged electrode at a temperature in the molding zone of 30 ° C, a relative humidity of 18% and a distance between the forming and precipitation electrodes of 180 mm. Then, the processes of electroforming, reinforcing and drying are carried out similarly to those described in example 1.

The main results of experimental studies on the substantiation of the technological process modes of the production method and the properties of the proposed filter material are shown in table 1.

Analysis of the experimental results shows that the highest filtration efficiency indicators, combining with the comfortable physical and hygienic characteristics of the nonwoven nanofiber material and meeting the requirements of the task of the present invention, are observed in a series of experiments No. 3 and No. 4.

The obtained experimental data also indicate that:

- molding is carried out from a solution of polyacrylonitrile in dimethylformamide, with a polymer concentration in the solution of 12.5 ... 13.0 wt. % and solution viscosity 1.2-1.4 Pa s (at 30 ° C). When using solutions with a concentration below 12.5 wt. % thinner fibers are formed, however, the thickness and surface density of the layer decrease, which leads to some decrease in the filtration efficiency. At a concentration above 13.0 wt. % sharply increases the viscosity of the molding solution, which leads to the formation of various defects in the structure of the fiber, causing a decrease in filtration efficiency;

- preferably molding is carried out at an electric field voltage of 80 kV, a temperature in the molding zone of 25-30 ° C and a relative humidity of 18-20%. At lower voltage values, a material is formed with a too low surface density, and, consequently, with insufficient filtration efficiency. Deviation from the indicated values of temperature and humidity leads to instability of the process of forming the filter layer;

- during molding, the distance between the forming and precipitation electrodes can be from 160 mm to 180 mm. At shorter distances, fibers of larger diameter are formed, and filtering efficiency is reduced. At distances above 180 mm, a material is obtained that has greater breathability, but this reduces the efficiency of aerosol filtration;

- the resulting filter layer is reinforced on both sides alternately (in two stages) by lamination with doublerin, preferably on a knitted basis, at a temperature of 125 ° C and spot application of polyamide glue, with a surface density of 65 g / m ² ;

- the resulting filter material is aged in air (dried) at room temperature for 24 hours.

The filter material has the following characteristics:

- the average diameter of the nanofibers, equal to 100-150 nm;

- mass per unit area of the filter layer equal to 4-6 g / m ² ;

- the mass of a unit area of the material is 134-136 g / m ² ;

- resistance to air flow of the filter layer at a linear speed of 1 cm / s is 7 ... 10 Pa;

- resistance to material air flow at a linear speed of 1 cm / s is equal to 280-300 Pa;

- vapor permeability is 7.0 ... 7.5 kg / m ² day .;

- total thermal resistance in calm air - 0.135-0.140 m ² ° C / W;

- the efficiency of aerosol filtration of dioctyl phthalate with a particle diameter of 0.3 μm is at least 99.998%.

The above data confirm that the claimed technical result is achieved by the combination of all the features of the invention: a new filtering high-performance non-woven non-woven nanofiber material having comfortable physical and hygienic properties is obtained.

Claims (5)

1. The method of obtaining filter material, which consists in the fact that electrostatic molding of polyacrylonitrile nanofibers is carried out in a high voltage electric field of 80 kV created due to the potential difference between the forming and precipitation electrodes, and at the same time the formed nanofiber is laid on a nonwoven substrate moving in the interelectrode space followed by double-sided reinforcement, characterized in that the electroforming is carried out from a solution of polyacrylonitrile in dimethylfor mamide at a polymer concentration of 12.5-13.0 wt. %, solution viscosity 1.2-1.4 Pa,4s, temperature 25-30 ° С, relative humidity 18-20% and the distance between the forming and precipitation electrodes 160-180 mm. 2. The method according to p. 1, characterized in that the reinforcement is carried out in two stages on both sides alternately at a temperature of 125 ° C with doubler layers of knitted brushed base and spot application of polyamide adhesive with a surface density of 65 g / m ² while removing the non-woven substrate . 3. The filter material made according to claim 1 or 2, which is a three-layer composition in which one of the layers is made of polymer nanofibers and is placed between two reinforcing layers, characterized in that the layer of polymer nanofibers is made of polyacrylonitrile fibers with a diameter of 100-150 nm with a density of 4-6 g / m ² . 4. The filter material according to claim 3, characterized by the following parameters: filtering efficiency of particles with a diameter of 0.3 μm not less than 99.998%, resistance to air flow at a linear velocity of 1 cm / s, equal to 280-300 Pa, mass per unit area of the material, equal to 134 -136 g / m ² , vapor permeability equal to 7.0 ... 7.5 kg / m ² per day, total thermal resistance in calm air, equal to 0.135-0.140 m ² ⋅ ° С / W. 5. The filter material according to claim 3, in which the reinforcing layers are made of doubler.