RU2624189C1 - Method for obtaining fibrous material containing oxide nanoparticles from thermoplast melt - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method, like the prototype, involves forming a fibrous material by laminating a melt of a thermoplastic polymer by the action of a gas stream containing solid particles. Particles penetrate into the surface layer of the softened material, and particle consolidation occurs, when the material passes into a solid aggregate state. New is that the formation of fibers occurs under the influence of an unheated gas stream containing oxide nanoparticles or small droplets of liquid, in which such nanoparticles having an ambient temperature are dispersed. Gas ejection is provided, in which an additional flow of unheated gas is generated around the jet of molten polymer fed. The particle size is less than 100 nm.

EFFECT: production of fibrous material with oxide nanoparticles fixed on its surface with one or, at least, two kinds, with minimal energy costs and simplification of the technological process.

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Description

The invention relates to the production of fibrous synthetic materials from thermoplastic substances with catalytic, antistatic and heat-insulating properties, and can be used to obtain porous heat-insulating materials, filtering and catalytic elements in the cleaning processes of liquid and gas environments, as well as in the manufacture of protective clothing used in industry.

A known method of obtaining filter material (RF patent No. 2401153). The production method consists in applying and fixing metal-containing nanoparticles based on a polymer fibrous material. Nanosized particles of tin dioxide are used as metal-containing nanoparticles, which are fixed on the surface of the substrate using microwave heating, while nanosized particles of tin dioxide are formed during heating from tin hydroxide particles obtained by hydrolysis of tin (II) salts from aqueous solutions, and as the basis non-woven polymeric fibrous material obtained by melt blowing of thermoplastic polymers was used. The basis of the method is the preparation and simultaneous fixing of semiconductor nanosized particles, such as tin dioxide, on the surface of the frame (base) of a polymer fine-fibrous material with minimal time and energy costs. The disadvantage of this method of producing fibrous synthetic materials coated with oxide nanoparticles is the limited choice of oxides, the complexity of the hydrolysis process and the use of expensive special equipment.

A known method of producing a polymeric fibrous material (Japan patent No. 2008-095266) containing silver nanoparticles by electrospinning. The polymer resin solution contains self-dispersing silver nanoparticles in an amount of 0.1-1.0 wt.%, Calculated on the weight of the polymer resin. Silver nanoparticles are introduced into the polymer melt until the stage of formation of the fibrous material. The fibrous material obtained by this method contains a sufficiently large number of silver nanoparticles (0.1-1 wt.% By weight of the polymer), which are fixed not only on the surface of the material, but also distributed in its entire volume, which leads to additional consumption of an expensive component.

Also known is a method (application JP 05204, D01D 1/02) for producing from a melt polyester fibers containing 0.4% titanium dioxide and Bactekiller (type A zeolite). The particles of titanium dioxide and zeolite are mixed with granules of polyethylene terephthalate in a twin-screw extruder of the Vent type to form a melt, from which fibers with antibacterial properties are formed. The disadvantage of these methods is that particles that are introduced at the stage of obtaining the melt or directly into the melt are agglomerated and unevenly distributed in the volume of fibrous materials, concentrating mainly to the center of the fibers, as a result of which their functional properties are lost. In addition, this method requires the use of special extrusion equipment.

In preparing a fibrous material containing nanoparticles, it is generally desirable to obtain a significant open surface area of the particles available for interaction with any medium to which the fiber may be exposed.

Closest to the technical nature of the claimed method (prototype) is a method of producing a fibrous material containing particles, according to US patent No. 6494974. The method includes extruding a melt of thermoplastic polymers through the holes of the die of the extrusion head with its subsequent spraying with converging flows of heated working gas (usually air) under the influence of which the forming fibers stretch and thin. Thermostable particles are heated to a temperature close to the extrusion temperature of the polymer melt. A stream of working (fiber-forming) air containing unhardened fibers is connected to a high-speed heated air stream containing particles. The heated particles penetrate the surface layer of the softened material of the polymer fibers. Then the fibrous material hardens in the streams of ambient air and particles are fixed on it. The fibrous material obtained by this method contains particles ranging in size from 5 to 300 microns, which are incorporated into the polymer to a depth greater than just point contact without the addition of expensive adhesive adhesive polymers. Most of the surface of the particles remains open for interaction with the environment, giving the resulting material new functional properties, for example, sorption.

However, using this method, it is impossible to obtain a material containing nanoparticles of metal oxides and their compounds, since they are unstable due to their inherent high surface energy, their heating leads to a thermodynamic beneficial aggregation process, in which micro-sized agglomerates are formed, and most of the functional properties that inherent in nanoscale particles of metals and their oxides. It is also impossible to spray dissimilar particles, for example, antimony and indium tin oxide materials, since mechanical mixing of dissimilar nanosized particles is a difficult process.

In addition, as follows from the description, the production of material requires heating both air flows, under the influence of which fibers are formed, and a stream containing thermostable particles to a temperature of about 265-296 ° C, and also the particles themselves from 50 to 200 ° C , depending on the type of polymer used. Thus, this method is complex, associated with significant energy costs and does not allow to obtain a fibrous material containing nanoscale particles of metal oxides.

The technical task of the invention is to reduce energy costs and the complexity of the process for producing a fibrous material containing oxide nanoparticles from molten thermoplastics.

The problem is solved in that the fibers of the material are formed by delaminating the melt of the thermoplastic polymer with a working gas stream, then they are exposed to the fiber by a gas stream containing solid particles, and the particles are fixed in the material due to the transition of the thermoplastic material to a solid state of aggregation. In this case, the polymer melt stream is fed into a larger diameter pipe, providing an annular gap between the stream and the pipe, unheated gas containing unheated oxide nanoparticles less than 100 nm in size or small drops of liquid containing such nanoparticles is supplied under pressure at an angle to the polymer stream, providing ejection of unheated gas through the annular gap between the melt stream and the nozzle, while oxide nanoparticles, the same as in the flow of the working gas, or nanoparticles of oxide of another metal, are introduced into the ejected gas rum less than 100 nm having an ambient temperature. The term "unheated" means that both the gas and the particles have approximately room temperature, for example, 20 ° C.

The claimed method for producing a fibrous material containing oxide nanoparticles from a melt of thermoplastics, as well as a prototype, involves the formation of a fibrous material by delamination of a melt of a thermoplastic polymer by the action of a gas stream containing solid particles, the particles penetrate the surface layer of the softened material, and the particles are fixed during the transition material in a solid state of aggregation.

What is new is that the formation of fibers occurs under the influence of an unheated gas stream containing oxide nanoparticles, or small liquid droplets in which such nanoparticles are dispersed at ambient temperature, and provide gas ejection, in which an additional unheated stream arises around the supplied stream of molten polymer gas, while the particle size is less than 100 nm, mainly from 25 to 80 nm.

The thermoplastic polymer is fed into the delamination zone through a nozzle of a larger diameter than the diameter of the melt jet, forming an annular gap between the jet and nozzle, and sprayed with a stream of unheated working gas containing oxide nanoparticles smaller than 100 nm, which is directed at an angle to the polymer melt jet so that transported nanoparticles acquire a radial velocity component. At the same time, gas ejection is provided in which a vacuum is created in the annular gap and an additional flow of unheated gas occurs. Nanoparticles less than 100 nm in size are also added to the ejected gas and two-phase flows in the separation zone are mixed. Nanoparticles less than 100 nm in size have a small mass, their presence in the gas stream does not violate the process of fiber formation. This allows the formation of fibrous material from the polymer melt by an unheated gas stream with the simultaneous creation of an ejected stream of unheated gas in the presence of oxide nanoparticles or small droplets of liquid in which the nanoparticles are dispersed, and the particles in the working gas stream and in the ejected gas can be of different types and have a temperature the environment. The absence of contact of the melt with the nozzle eliminates premature cooling of the melt and an increase in its viscosity. Thus, there is no need to heat the nanoparticles and the gaseous medium to a high melting point of the polymer, which simplifies the process and significantly reduces energy costs.

When implementing the proposed method, solid nanoparticles or small droplets of liquid in which the nanoparticles are dispersed are evenly distributed in the carrier gas phase due to turbulence of the flow, and can be transported to the separation zone either by the flow of the working gas, or by the ejected gas stream, or both at the same time. In this case, an option is not excluded in which a gas with particles is additionally injected into the ejected gas under pressure. When the polymer melt is stratified, the flow of the working gas is directed at an angle to the melt jet, so that the nanoparticles have a velocity whose vector is directed to the melt jet and the corresponding kinetic energy. In addition, during transportation, the oxide nanoparticles are electrified. Under the action of inertia and electrostatic forces, oxide nanoparticles are attracted to the melt and deposited on its surface. The uniformity of the fiber coating is provided by the turbulent nature of the flow of the conveying gas. In the process of polymer solidification, the nanoparticles are firmly fixed on the surface of the formed fibers. Due to the shallow penetration into the melt due to the small mass of nanoparticles, most of the surface of the particles remains open, which is important for technical applications.

The applicant does not know how to obtain fibrous materials from molten thermoplastics with an unheated gas stream, which allows uniformly deposited heterogeneous oxide nanoparticles on the fiber, so the claimed solution meets the criterion of novelty. The resulting technical result is not obvious. In assessing the compliance of the new method for producing fibrous materials containing oxide nanoparticles with the criterion of "inventive step" in the information sources available to the applicant, technical solutions were not found in which nanoparticles aggregating during heating are transported to the polymer by an unheated ejection stream and introduced into the polymer fibers using an unheated working gas directed at an angle to the resulting polymer fibers.

The inventive method is illustrated using graphic materials.

In FIG. 1 is a diagram of the implementation of the proposed method, where 1 is a melt stream of a thermoplastic fiber-forming polymer, 2 is a pipe, 3 is a separation zone in which fiber formation occurs, 4 is a stream of unheated gas under pressure, 5 is an elementary fiber, 6 is a satellite ejected gas stream, preventing contact of the jet with the nozzle.

In FIG. Figure 2 shows a fiber fragment with a surface coated with oxide nanoparticles.

To implement the inventive method, a simple device can be used in which the melt stream of a thermoplastic fiber-forming polymer 1 is extruded through a nozzle 2 into a separation zone 3. The diameter of the nozzle 2 must exceed the diameter of the jet of polymer 1 so that their mutual contact is guaranteed to be absent. At the same time, an unheated gas stream 4 is supplied under pressure to the stratification zone 3 at an angle to the jet 1, which crushes the melt stream 1 into elementary fibers 5 and also forms a tangential ejected gas stream 6. in the gap between the melt stream and the nozzle 6. Into the working gas stream and oxide nanoparticles with a size of less than 100 nm are added to the satellite ejected stream by known methods.

There are several possible implementations of the method for producing a fibrous material containing oxide nanoparticles from molten thermoplastics. Options differ in the methods of feeding oxide nanoparticles.

In the main embodiment, oxide nanoparticles are introduced into the unheated working gas stream 4, which is supplied under pressure to the separation zone 3, and simultaneously introduced into the ejected gas stream 6, and the nanoparticles can be of different types. In zone 3, under the action of a gas stream, the polymer melt is separated and the fibrous material 5 is formed in the presence of oxide nanoparticles, which are deposited on the surface of the fibers. Then the fibrous material solidifies in the streams of the surrounding gas and the particles are firmly fixed to the fibers.

In other embodiments, particles are introduced into only one of the gas streams, either into the working gas or into the ejected one. Finally, an additional pressurized gas containing oxide nanoparticles can be added to the ejected gas stream. In all cases, the particles do not heat up and have an ambient temperature. Technological modes of the process vary depending on the types of feedstock (type of polymer and types of nanoparticles) and on the intended intended use of the resulting fibrous materials.

An example of obtaining a fibrous material containing oxide nanoparticles from molten thermoplastic according to the claimed method.

As raw materials were used:

- polymer - commercial polypropylene grade 21080-16, produced according to TU 2211-016-05796653-95, rev. 3;

- nanoparticles - antimony, indole and bismuth oxide materials (ATO, ITO and BTO, respectively), manufactured by solid-phase synthesis in the temperature range 300-1473 K, in a highly dispersed state with an average particle size of 25 to 80 nm.

Polypropylene granules (grade 21080) were heated to a temperature of 265 ° C, corresponding to the homogenization of the melt. Then the melt 1 was fed into the pipe 2 at a speed of 16.2 ° kg / h. At the same time, a gas stream 4 containing ATO nanoparticles was supplied at a pressure of 2 atm at a gas and particle temperature of about 20 atm through an annular convergent nozzle with a cross-sectional area of 31 mm ² to the separation zone 3. In this case, an annular gap between the polymer stream and nozzle 2 was created rarefaction, and an ejected gas stream 6 containing ITO or BTO nanoparticles arose at a gas and particle temperature of about 20 ° C. Further, in zone 3, the melt was stratified and the fibrous material 5 was formed in the presence of oxide nanoparticles, which were deposited on the surface of the melt. Then, the fibrous material solidified in the flows of the surrounding gas, ATO nanoparticles and ITO or BTO nanoparticles were uniformly and firmly fixed on it.

The fibrous material obtained in this way has on its surface nanoparticles with a size of 25-80 nm, which cover from 10 to 25% of the surface area of the fibers. Pictures of the fibers were obtained using transmission electron microscopy using a JEM-100CXII electron microscope (Fig. 2). The strong attachment of ATO, ITO, BTO nanoparticles to the fibrous material was confirmed by the results of atomic emission spectrometry with inductively coupled plasma on an ICAP 6300 Duo Thermo spectrometer. This method showed that the content of the tin contained in the nanoparticles on the polypropylene fiber does not change after intensive washing with running water.

The use of oxide nanoparticles with a size of less than 100 nm, a significant part of each of which protrudes from the polymer, makes it possible to impart new functional properties to the fibrous material, for example, catalytic, antistatic, and thermal insulation, since it is known that oxide nanoparticles have low resistivity and optical transparency in visible areas of the electromagnetic spectrum, high reflectivity for infrared radiation, as well as high chemical activity.

The technical result is to obtain a fibrous material with oxide nanoparticles of one or at least two types fixed on its surface, with minimal energy costs and simplifying the process.

The method according to the invention can be used to obtain fibrous materials with desired properties from a melt of thermoplastics of both industrial and secondary raw materials, as well as from mixtures thereof, which differ in flow rate and have, for example, catalytic, antistatic and / or thermal insulation properties.

Information sources

1. RF patent No. 2401153, IPC B01D39 / 16, IPC B82B3 / 00, publ. 10/10/2010.

2. Patent JP2008-095266, publ. 04/24/2008.

3. Application JP 05204, D01D 1/02, publ. 1993.

4. Pinchuk, L. S., Goldade, V. A., Makarevich, A. V., & Kestelman, V. N. Melt Blowing: Equipment, Technology, and Polymer Fibrous Materials. Springer Science & Business Media, (2012).

5. Patent US6494974 B2, publ. 11/17/2002 (prototype).

Claims (1)

A method of producing a fibrous material containing oxide nanoparticles from a melt of thermoplastics, including the formation of fibers of a material by delaminating a melt of a thermoplastic polymer with a working gas stream, exposing the fibers to a gas stream containing solid particles, and fixing the particles in the material due to the transition of the thermoplastic material to a solid state of aggregation characterized in that the polymer melt stream is fed into a pipe of a larger diameter, providing an annular gap between the stream and the pipe, at an angle ohm, an unheated gas containing unheated oxide nanoparticles with a size of less than 100 nm, preferably from 25 to 80 nm, or small drops of a liquid containing such nanoparticles, providing ejection of unheated gas through the annular gap between the melt stream and the nozzle, are supplied under pressure to the polymer stream under pressure oxide nanoparticles, the same as in the working gas stream, or other metal oxide nanoparticles with a size less than 100 nm, having an ambient temperature, are introduced into the ejected gas.

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