Patent Description:
Polyacrylonitrile fiber, commonly known as acrylic fiber or artificial wool, is a commonly used artificial fiber that can be used to replace or blended with wool to make wool fabrics. It has a good effect of warmth retention, and it also has excellent weather resistance and light resistance, after one year of open-air exposure, the intensity only decreases by <NUM>%, so it is often used to make curtains, tarpaulins, etc..

Electrospinning is a special fiber manufacturing process, and has been used more and more in the past ten years to prepare nanofiber materials. Its working method is as follows: the polymer solution or the melt is jetted out in a high-voltage electric field, solidified in a running distance, and finally the spinning is received by a receiving device. Due to the process of electrostatic spinning is simple, and various forms of fibers can also be produced according to demand, such as solid fibers, hollow fibers, core-shell structure fibers, etc., it has broad prospects in many fields. <CIT> discloses a film-slitting electrostatic spinning continuous nanofiber yarn device and a method for preparing continuous nanofiber yarns by this device.

However, the current electrostatic spinning technology is only used to manufacture a non-woven fabric or spray a thin layer of nano-cobweb on industrial non-woven fabrics (generally with an areal density of about <NUM>/m<NUM>), which can also manufacture discontinuous and higher linear density of thick yarn, and there is no technology in the world that can continuously manufacture ultra-small linear density or ultra-high count yarn of electrospun nanofibers. The linear density of conventional fiber yarns is above <NUM> Tex, and the counts of the yarns are generally less than <NUM> counts, and most of them are below <NUM> counts.

To solve the above technical problems, the first aspect of the present invention provides a method for preparing a continuous filament yarn of electrospun polyacrylonitrile nanofibers, wherein the continuous filament yarn has a length of no less than <NUM> meters and a metric count of more than <NUM>, the method comprising the following steps:.

According to a preferred embodiment, the polar solvent in the step a is one or more selected from the group consisting of N, N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and N, N-dimethylacetamide.

According to another preferred embodiment, the water bath draft and air draft in the step d are <NUM>-roll drafts.

According to another yet preferred embodiment, the unwinding speed of the water bath draft in the step d is <NUM> to <NUM>/min.

According to another yet preferred embodiment, the unwinding speed of the air draft in the step d is <NUM> to <NUM>/min.

According to another yet preferred embodiment, the fiber orientation degree of the fiber bundle in the step d is <NUM>% to <NUM>%.

According to another yet preferred embodiment, the unwinding speed of twisting in the step e is <NUM> to <NUM>/min.

According to another yet preferred embodiment, the twist degree of twisting in the step e is <NUM> to <NUM> twist/m.

The second aspect of the present invention provides a continuous filament yarn of electrospun polyacrylonitrile nanofibers, which is prepared by the above method for preparing a continuous filament yarn of electrospun polyacrylonitrile nanofibers.

The continuous filament yarn of electrospun polyacrylonitrile nanofibers may be used for pure or blended spinning to weave a light-weight and warm high-grade fabric.

Beneficial effects: the present invention provides a method for preparing a continuous filament yarn of electrospun polyacrylonitrile nanofibers, which enhance the mechanical properties of polyacrylonitrile fibers through draft operation and can produce continuously, and the produced filament yarns have a length of not less than <NUM> meters and a metric count of more than <NUM>, which can be used for pure or blended spinning to obtain a light-weight, warm and durable high-grade fabric.

The content of the present invention can be further understood in conjunction with the following detailed description of the preferred implementation methods of the present invention and the included embodiments. Unless otherwise stated, all the technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the application belongs. If the definition of a specific term disclosed in the prior art is inconsistent with any definition provided in this application, the definition of the term provided in this application shall prevail.

As used herein, unless the context clearly indicates otherwise, features that do not define singular and plural forms are also intended to include features of the plural form. It should also be understood that, as used herein, the term "prepared from" is synonymous with "comprise", "include", "including", "having", " comprise" and/or "comprising", when used in this specification, they mean the stated composition, step, method, article or device, but do not exclude the presence or addition of one or more other compositions, steps, methods, articles or devices. In addition, when describing the embodiments of the present application, the use of "preferred", "preferably", "more preferably", etc. refers to an embodiment of the present invention that can provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. In addition, the expression of one or more preferred embodiments does not imply that other embodiments are not available, nor is it intended to exclude other embodiments from the scope of the present invention.

In order to solve the above technical problems, the present invention provides a method wherein for preparing a continuous filament yarn of electrospun polyacrylonitrile nanofibers, the continuous filament yarn has a length of no less than <NUM> meters and a metric count of more than <NUM>, comprising the following steps:.

The objective of step a is to prepare a polymer solution suitable for electrostatic spinning, and because there are a large number of polar cyano groups in polyacrylonitrile, selecting a suitable polar solvent helps to prepare a spinning solution with suitable concentration and adjustable viscosity.

dissolving a polyacrylonitrile raw material in a polar solvent under mechanical stirring to obtain a uniform spinning solution.

In some preferred embodiments, the polyacrylonitrile raw material and the polar solvent are added together in a stainless steel reactor and dissolved under mechanical stirring to obtain a uniform polyacrylonitrile solution for spinning.

The polyacrylonitrile raw material in the present invention is not particularly limited, and may be commercially available, and the <NPL>.

In some embodiments, the polar solvent in step a is selected from one or more of N, N-dimethylformamide (<NPL>), N-methylpyrrolidone (<NPL>), dimethyl sulfoxide (<NPL>) and N, N-dimethylacetamide (<NPL>).

Both dimethyl sulfoxide and N-methylpyrrolidone are good solvents for dissolving polyacrylonitrile, and dimethyl sulfoxide is non-toxic, but both have boiling points above <NUM>, and the spun yarns are not easy to dry and have serious adhesion to each other. N, N-dimethylformamide has the lowest boiling point among several listed solvents and has the best solubility, while N, N-dimethylacetamide has relatively low solubility, but has the advantage of low toxicity which can be compounded with N, N-dimethylformamide to make a mixed solvent for spinning.

In some preferred embodiments, the polar solvent in the step a is N, N-dimethylformamide and/or N, N-dimethylacetamide; further preferably, the N, N-Dimethylformamide and N, N-dimethylacetamide; further, the mass ratio of N, N-dimethylformamide and N, N-dimethylacetamide is <NUM>: <NUM>.

The concentration of the spinning solution determines the viscosity of the solution, if the viscosity is too large, the electrostatic force needs to overcome a greater surface tension, making the spinning diameter too large or even impossible to spin; and too small viscosity will make the spinning too thin, insufficient strength, or beads may appear on the spinning. The mass concentration of the solution in the step a is <NUM> to <NUM>%; preferably, the mass concentration of the solution in the step a is <NUM> to <NUM>%,.

In some preferred embodiments, the absolute viscosity of the solution in the step a is <NUM> to <NUM> Pa. S; further preferably, the absolute viscosity of the solution in the step a is <NUM> to <NUM> Pa.

On the one hand, appropriate dissolution temperature can speed up the dissolution rate and improve the processing efficiency, on the other hand can reduce the solubility of the gas in the solution, and remove the gas from the solution. In some preferred embodiments, the dissolution temperature in the step a is <NUM> to <NUM>, and the stirring time is <NUM> to <NUM> hours; further preferably, the dissolution temperature in the step a is <NUM> to <NUM>, and the stirring time is <NUM> to <NUM> hours.

The objective of the step b is to make polyacrylonitrile from solution into a nonwoven fabric, in this process, the polymer solution is sprayed into a strong electric field. Under the action of the electric field, the sprayed droplets change from spherical to Taylor cone, from the tip of which a tiny jet is extended, and after running for a certain distance, the jet is solidified into fiber filaments, which are collected by a stainless steel mesh belt to obtain a nonwoven fabric.

making the polyacrylonitrile solution in the step a into a polyacrylonitrile nonwoven fabric in an electrospinning machine.

The polyacrylonitrile solution is injected into the spinning device of an electrospinning machine, spraying spun in a high-voltage electric field, and collected with a stainless steel mesh belt to obtain an electrospun polyacrylonitrile nonwoven fabric.

The magnitude of the voltage of the electric field will affect the shape of the sprayed droplets. Too small voltage cannot make the spherical droplets of the spinneret form a Taylor cone, and too large voltage will cause the formed Taylor cone to retreat or even back into the spinneret, resulting a large number of beads appeared in the spinning fibers. The DC voltage of the high-voltage electric field in the step b is <NUM> to <NUM> kV; preferably, the DC voltage of the high-voltage electric field in the step b is <NUM> to <NUM> kV,.

The distance between the spinneret and the stainless steel mesh belt collector requires to ensure that the jet can be solidified during running without adhesion, and improper receiving distance will cause beads appeared in the spinning fibers. In some preferred embodiments, the distance between the spinneret and the stainless steel mesh belt collector in the step b is <NUM> to <NUM>; further preferably, the distance between the spinneret and the stainless steel mesh belt collector is <NUM> to <NUM>.

The travel speed of the stainless steel mesh belt can affect the pore size and thickness of the nonwoven fabric, which in turn affects the strength of the filament yarn processed from the nonwoven fabric. In some preferred embodiments, the travel speed of the stainless steel mesh belt in the step b is <NUM> to <NUM>/min; further preferably, the travel speed of the stainless steel mesh belt is <NUM> to <NUM>/min.

In some preferred embodiments, the diameter of the spinning in step b is <NUM>-<NUM>; further preferably, the diameter of the spinning in the step b is <NUM> to <NUM>.

The objective of the step c is to pretreat the polyacrylonitrile nonwoven fabric into a form suitable for further processing.

Step c: cutting the nonwoven fabric in the step b into slender strips with a width of <NUM> to <NUM>.

The width of the cut strip will affect the subsequent further processing, and too narrow cut strip is not conducive to continuous production, making the resulting yarn easily broken, and it is impossible to achieve the ideal length to obtain a filament yarn; while too wide cut strip is difficult to process to obtain a fiber bundle with highly oriented internal fibers. The width of the slender strip in the step c is <NUM> to <NUM>; preferably, the width of the slender strip is <NUM> to <NUM>.

The objective of the step d is, on the one hand, to obtain a fiber bundle length sufficient to produce continuous filament yarns through drafting, and on the other hand, to change the degree of orientation of the internal fibers, making the strength of the fiber bundle in the orientation direction increased greatly-.

Step d: drafting the slender strips in the step c in a water bath at <NUM> to <NUM> with a draft ratio of <NUM> to <NUM> times, then drafting in air at <NUM> to <NUM> with a draft ratio of <NUM> to <NUM> times to obtain a fiber bundle with highly oriented internal fibers.

In some preferred embodiments, the water bath draft and air draft in the step d are <NUM>-roll drafts.

In some preferred embodiments, the unwinding speed of the water bath draft is <NUM> to <NUM>/min; further preferably, the unwinding speed of the water bath draft is <NUM> to <NUM>/min.

In some preferred embodiments, the unwinding speed of the air draft is <NUM> to <NUM>/min; further preferably, the unwinding speed of the air draft is <NUM> to <NUM>/min.

In some preferred embodiments, the fiber orientation degree of the fiber bundle in the step d is <NUM>% to <NUM>%.

The objective of the step e is to twist the fiber bundle into a filament yarn. After twisting, the outer fiber and the inner fiber squeeze each other to generate pressure, making the yarn obtain frictional force along the fiber length, and the fiber strip is longitudinally fixed, and the fiber after yarn formation has improved properties such as strength, elongation, gloss, and feel.

Step e: twisting the fiber bundle in the step d to obtain a continuous filament yarn of electrospun polyacrylonitrile nanofibers with a length of not less than <NUM> meters.

The unwinding speed of twisting in the step e is <NUM> to <NUM>/min; preferably, the unwinding speed of twisting is <NUM> to <NUM>/min,.

In some preferred embodiments, the twist degree of twisting in the step e is <NUM> to <NUM> twist/m; further preferably, the twist degree of twisting in the step e is <NUM> to <NUM> twist/m.

Compared with other fibers, the strength of polyacrylonitrile nanofibers is lower. In terms of the original excellent properties of polyacrylonitrile such as weather resistance and warmth retention, the strength of polyacrylonitrile fiber after high drafting is further improved, which broadens its range of application. After the fiber is drafted and twisted, filament yarn can be produced continuously, which in turn can be used for pure or blended with other fibers to weave alight-weight, warm, soft, and comfortable high-grade fabric.

The technical solutions of the present invention will be described in detail below through the examples, but the protection scope of the present invention is not limited to the examples.

Example <NUM> provided a method for preparing a continuous filament yarn of electrospun polyacrylonitrile nanofibers, comprising the following steps:.

The continuous filament yarns of electrospun polyacrylonitrile nanofibers obtained in examples <NUM> to <NUM> were tested for metric count, tensile strength, Young's modulus, and elongation at break.

Metric count,: <NUM> meters of yarn was weighed its gram weight, and the metric count = <NUM>/gram weight. The results were shown in Table <NUM>.

Tensile strength, Young's modulus, elongation at break: tested with an electronic universal tensile machine. The results were shown in Table <NUM>.

Claim 1:
A method for preparing a continuous filament yarn of electrospun polyacrylonitrile nanofibers, wherein the continuous filament yarn has a length of no less than <NUM> meters and a metric count of more than <NUM>, the method comprising the following steps:
a. dissolving a polyacrylonitrile raw material in a polar solvent under mechanical stirring to obtain a uniform spinning solution, wherein a mass concentration of the spinning solution is <NUM> to <NUM>% (w/w);
b. making the polyacrylonitrile solution in the step a into a polyacrylonitrile nonwoven fabric in an electrospinning machine, wherein the polyacrylonitrile solution is spraying spun in a high-voltage electric field, and DC voltage of the high-voltage electric field in the step b is <NUM> to <NUM> kV;
c. cutting the nonwoven fabric in the step b into slender strips with a width of <NUM> to <NUM>;
d. drafting the slender strips in the step c in a water bath at <NUM> to <NUM> with a draft ratio of <NUM> to <NUM> times, then drafting in air at <NUM> to <NUM> with a draft ratio of <NUM> to <NUM> times to obtain a fiber bundle with highly oriented internal fibers;
e. twisting the fiber bundle in the step d to obtain a continuous filament yarn of electrospun polyacrylonitrile nanofibers with a length of not less than <NUM> meters, and the unwinding speed of the twisting is <NUM> to <NUM>/min.