US20170204540A1

US20170204540A1 - Highly absorbent, super-soft and functionalized composite yarn, textile and related manufacturing method

Info

Publication number: US20170204540A1
Application number: US15/083,973
Authority: US
Inventors: Hongwei Duan
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-01-20
Filing date: 2016-03-29
Publication date: 2017-07-20

Abstract

A highly absorbent, super-soft composite yarn includes a core formed of microfibers and a covering layer formed of natural fibers which are twisted and surround the microfibers. The microfiber is a composite fiber having two or more components. In one structure, the two components are held together in an interleaved structure resembling an orange in cross-section. In another structure, the microfibers have undergone a splitting process and the two components are separated from each other, where the single filaments of the two components have a linear mass density below 0.55 dtex. The natural fibers of the covering layer cotton fibers, hemp fibers, wool fibers, bamboo fibers, silk fibers, or soybean fibers. The microfibers are functionalized with one or more additives, such as antibacterial, aromatic, and UV-blocking additives. A method for manufacturing the composite yarn and related textile is also described.

Description

BACKGROUND OF THE INVENTION

Field of the Invention
This invention relates to super-fine functionalized yarns, and in particular, it relates to highly absorbent, super-soft, functionalized composite yarns, textile made from the yarn, and related manufacturing methods.
Description of Related Art
Natural fibers are preferred fabric materials for garments and other products such as towels, because they are soft to the touch, comfortable and safe to use on the skin. But due to various inherent limitations, the absorbance, quick-drying properties and softness of such textile are not ideal. For example towels made of cotton do no try quickly, and tend to become hard and less absorbent after a period of use. Although various properties of such fabrics can be improved by using certain functional additives to treatment the fabrics, the desirable properties are often lost after repeated washing, and some additives may irritate the skin. Also, with the increased living standards, more and more demands are placed on useful functions of fabrics, such as antibacterial properties, UV-blocking properties, cool or warm feel to the touch, etc.
Composite yarns typically use a high strength, high elasticity, long synthetic fiber as the core, which is covered with relatively short fibers such as cotton, wool, viscose fiber etc. and form into a yarn. Composite yarn combines the desirable properties of the long filament of the core and the outer short fibers. One commonly known composite yarns is polyester-cotton composite yarn, which is formed of polyester fiber as the core and covered with cotton fibers. Another commonly known composite yarn is spandex composite yarns, which are formed of spandex fibers as the core and covered with other fibers. Textile and clothing made of spandex composite yarns have desired elasticity and can stretch, making it comfortable to wear. The main advantages of composite yarns are the improved properties over single fiber yarns.

SUMMARY

Although the known composite yarns combine the advantages of cotton and synthetic fibers, certain shortcomings remain. While textile made of natural fibers feels soft, are comfortable and safe to use, their absorbance, quick-drying properties and strengths are weak. When natural fibers form composite yarns with polyesters and polyamides, although the strength of the yarns is improved, they still do not have desired absorbance, quick-drying property and sufficiently soft feel.
Accordingly, the present invention is directed to a composite yarn, textile made of the yarn, and related manufacturing method that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a composite yarn and fabrics made of such yarn, that are highly absorbent, quick-drying, super-soft, have a natural feel and are functionalized. Such yarn and fabrics combine the desirable properties of natural fibers and synthetic fibers, and have UV-blocking, antibacterial and other desirable properties. Moreover, such desirable properties are long-lasting.
Another object of the present invention is to provide various products such as clothes for garment, towels, etc. that have desirable properties such as high absorbance, quick-drying, soft, comfortable, antibacterial, odor prevention, aromatic, etc.
Another object of the present invention is to provide manufacturing methods for the above composite yarn and fabrics.
Additional features and advantages of the invention will be set forth in the descriptions that follow and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings.
To achieve these and/or other objects, as embodied and broadly described, the present invention provides a composite yarn which includes: a core formed of microfibers which have two or more components; and a covering layer formed of natural fibers which are twisted and surround the core.
In one embodiment, each microfiber has two components held together in an interleaved arrangement in a cross-sectional view.
In one embodiment, the two components are polyamide 6 and polyester.
In one embodiment, either the polyamide 6 component or the polyester component or both are functionalized with a functional material.
In one embodiment, the functional material is selected from a group consisting of antibacterial materials, aromatic materials, and UV-blocking materials.
In one embodiment, the microfibers are separate filaments of polyamide 6 and polyester which have a linear mass density of less than or equal to 0.55 dtex.
In one embodiment, either the polyamide 6 filaments or the polyester filaments or both are functionalized with a functional material.
In one embodiment, the functional material is selected from a group consisting of antibacterial materials, aromatic materials, and UV-blocking materials.
In one embodiment, the natural fibers of the covering layer are selected from a group consisting of cotton fibers, hemp fibers, wool fibers, bamboo fibers, silk fibers, and soybean fibers.
In another aspect, the present invention provides a fabric made of the composite yarn described above.
In another aspect, the present invention provides a method of making a fabric, which includes: forming microfibers, each microfiber having two components held together in an interleaved arrangement in a cross-sectional view; covering a core containing the microfibers with a covering layer of natural fibers to form a composite yarn; forming a grey fabric by weaving the composite yarn; and treating the grey fabric with a causticization process to cause the two components of the microfibers of the core to separate from each other to form separate filaments, wherein the filaments have a linear mass density of less than or equal to 0.55 dtex.
In one embodiment, the causticization process uses a solution with an alkaline concentration is about 4-8 g/L at a temperature of 100-130° C.
In one embodiment, the step of forming the microfibers includes: melting polyamide 6 (PA6) granules in a screw extruder at a temperature of 255-270° C. and a pressure of 9-10 MPa; melting polyethylene terephthalate (PET) granules in another screw extruder at a temperature of 280-288° C. and a pressure of 9-10 MPa; feeding the melted PA6 and PET to a spinning manifold and co-spinning them at a temperature of 140-250 MPa and a spinning speed of 2800-3200 m/min, to form a microfiber structure having PA6 and PET components held together in an interleaved arrangement in a cross-sectional view; and pulling the microfibers and cooling them, wherein the cooling is by air cooling with an air speed of 0.3 to −0.5 m/min, a relative humidity of 70-80% and a temperature of 18-23° C.
In one embodiment, a weight ratio of the PET and PA6 granules is 50-85: 50-15.
In one embodiment, the step of melting the PA6 granules includes adding a functional masterbatch to the PA6 granules, an amount of the functional masterbatch being 1-4 wt % of the PA6 granules, and/or the step of melting the PET granules includes adding a functional masterbatch to the PET granules, an amount of the functional masterbatch being 1-4 wt % of the PET granules.
In one embodiment, the functional masterbatch is selected from a group consisting of antibacterial materials, aromatic materials, and UV-blocking materials.
In one embodiment, the natural fibers of the covering layer are selected from a group consisting of cotton fibers, hemp fibers, wool fibers, bamboo fibers, silk fibers, and soybean fibers.
In one embodiment, in the covering step, a tension in the microfibers is greater than a tension in the natural fibers.
In one embodiment, the method further includes dyeing and drying the fabric after the causticization process.
In one embodiment, the grey fabric is a towel, which includes a ground fabric and terry which are both formed of the composite yarn. In another embodiment, the grey fabric is used for home textiles such as bedding sheets, covers, duvets, etc.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates the cross-section of a composite yarn according to a first embodiment of the present invention.

FIG. 2 schematically illustrates the cross-section of the microfiber of the core of the composite yarn in the first embodiment.

FIG. 3 schematically illustrates the cross-section of a composite yarn according to a second embodiment of the present invention.

FIG. 4 schematically illustrates the cross-section of the microfiber of the core of the composite yarn in the second embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention are described with reference to the drawings. It should be understood that these embodiments are used to illustrate the invention, and the invention is not limited to the embodiments. Those skilled in the art will appreciate that various modification and variations can be made in the composite yarn and its manufacturing method of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations that come within the scope of the appended claims and their equivalents.
As shown in FIGS. 1-4, the highly absorbent, super-soft composite yarn includes a core 2 and a covering layer 3. The core is formed of one or more microfibers 1, and the covering layer 3 is formed of natural fibers which are twisted and surround the microfibers 1. The microfiber 1 is formed from a composite fiber having two or more components.
The natural fibers of the covering layer 3 are preferably selected from cotton fibers, hemp fibers, wool fibers, bamboo fibers, silk fibers and soybean fibers, or combinations thereof.
In some embodiments, the composite yarn is a functionalized composite yarn, where the microfibers are functionalized with one or more additives, such as antibacterial, aromatic, and UV-blocking additives.
In a first embodiment of the invention, shown in FIGS. 1 and 2, the microfiber 1 is formed of two components, which are polyester and polyamide 6 in one particular implementation, the two components being held together in an interleaved arrangement that resembles an orange in the cross-section, as shown in FIG. 2.
FIG. 2 shows the cross-section of one microfiber 1, where the two components 4 and 5 are interleaved in the manner as illustrated, i.e., the two components 4 and 5 together form a structure which has a round cross-sectional shape where the component resemble sections of an orange. In this example, the component 5 is polyamide 6 and the component 4 is polyester.
In a second embodiment of the invention, shown in FIGS. 3 and 4, the core 2 of the yarn is formed of microfibers 1 having the structure shown in FIG. 2, but it has undergone a process of splitting treatment, so that the two components 4 and 5 of the microfibers 1 are separated from each other, as shown in FIG. 4, where each piece of the separated component forms a fine filament with spaces 6 between the filaments.
In FIG. 3, the core 2 is depicted as containing filaments of the separated components, rather than the microfibers 1 where the two components are held together in the orange-shaped structure shown in FIGS. 1 and 2. Preferably, after the splitting process, the single filaments in the core 2 have a linear mass density of less than or equal to 0.55 dtex. The fine spaces 6 between the filaments can create a capillary effect, so fabric products made of the resulting yarn have superior absorbing properties and quick-drying properties. The fabric products also are soft to the touch because of the natural fiber covering 3.
In embodiments of the present invention, the fiber splitting treatment is a causticization process (also referred to as alkali deweighting treatment), which is performed after the yarn in the form shown in FIGS. 1 and 2 are made (e.g. woven) into a fabric.
In the microfiber 1, either the component 5 (e.g. polyamide 6) or the component 4 (e.g. polyester) or both may be functionalized, i.e., made to contain one or more functional components. The functional components may be antibacterial materials, aromatic materials, UV-blocking materials, etc. The resulting microfibers are referred to as functionalized microfiber.
The composite yarn according to embodiments of the present invention not only combines the advantages of natural fibers and synthetic fibers, but also has superior absorbance and quick-drying properties due to the use of microfibers. It is soft, and can be made to have antibacterial, flame retardant, aromatic and/or UV-blocking properties.
A composite yarn and fabric described above may be manufactured as follows. The microfiber 1 is formed by melting PA6 (polyamide 6, or Nylon 6) and PET (polyethylene terephthalate, a material in the polyester family) granules, and co-spinning them to form a composite fiber structure having a cross-section that resembles an orange as described earlier (see FIG. 2). Functional masterbatchs are optionally added to the PA6 and/or PET granules. The functional masterbatchs may include one or more of antibacterial masterbatch, aromatic masterbatch, UV-blocking masterbatch, etc.
In one example, the natural fiber 3 is bamboo fiber, and antibacterial masterbatch is added to the PET granules.
In another example, the natural fiber 3 is cotton fiber, and aromatic masterbatch is added to the PA6 granules. In this example, the amount of the aromatic masterbatch is about 2.0 wt % of the total granules, and the weight ratio of the PET and PA6 granules is about 70:30.
More specifically, a manufacturing process according to embodiments of the present invention included the following steps.
(1) The PA6 and PET granules are separately dried. One or more types of functional masterbatchs, such as antibacterial masterbatch, aromatic masterbatch, UV-blocking masterbatch, etc., are dried in a separately drying tower, where the drying temperature is about 100-120° C. and the drying time is about 8-10 hours.
(2) The dried PA6 and PET granules are separately fed into two screw extruders to be melted. The functional masterbatch is accurately measured with a dosing pump, and fed together with one or both of the PA6 granules and the PET granules into the respective screw extruders, and melted together with the PA6 and/or PET. The melting temperature applied to the PA6 granules is about 255-270° C., and the melting temperature applied to the PET granules is about 280-288° C. The pressure of the screw extruders is about 9-10 MPa.
(3) The two melted materials are respectively measured with melt dosing pumps and then fed to a spinning manifold, and co-spun using an orange-shape type spinning pack to form the microfibers having the structure shown in FIG. 2. The pressure of the melt materials in the spinning pack is about 140-250 MPa. The spinning speed is about 2800-3200 m/min.
(4) The spun fibers are then pulled and cooled to obtain the functionalized microfibers. Cooling is done by air cooling, where the air speed is about 0.3 to −0.5 m/min; the relative humidity of the air is about 70-80% and the temperature is about 18-23° C.
Preferably, the amount of the functional masterbatch is about 1-4 wt % of the total granules, and the weight ratio of the PET granules and PA6 granules is about 50-85: 50-15.
The process may further include steps for making highly absorbent, quick-drying, super soft, natural feeling fabrics, which include the following steps.
(5) Using the functionalized microfibers as the core, and using natural fibers as covering fibers, the core is covered with natural fibers to form the composite yarn. When forming the cover, the tension in the core fibers is greater than the tension in the covering fibers.
(6) The composite yarn is woven into a grey fabric. To make towels, the composite yarn is woven to form the ground fabric and the terry of the grey fabric for the towels.
(7) The grey fabric is treated with an alkaline reduction treatment (causticization), dyed, and dried to obtain the highly absorbent, quick-drying, super-soft and natural-feeling functionalized fabric. The temperature of the solution for the alkaline reduction treatment is about 100-130° C. and the alkaline concentration is about 4-8 g/L. During the alkaline reduction treatment before dyeing, the microfibers undergo splitting, i.e. the two components of the microfibers 1 (see FIGS. 1 and 2) are separated from each other to form the structure described earlier (see FIGS. 3 and 4). As a result, spaces are formed between the separated filaments to improve capillary effect of the fabric.
Preferably, in the above process, the natural fiber is selected from cotton fibers, wool fibers, hemp fibers, silk fibers, soybean fibers and bamboo fibers.
Preferably, in the covering step (5) described above, low hardness, high elasticity rubber rollers are used to improve the covering effect. Press bar clamp and collector are used to ensure that the core is located at optimum positions.
In the process examples described below, specific values of various process parameters are given.

Process Example 1

(1) The PA6 and PET granules are separately dried. The antibacterial masterbatch is dried in a separately drying tower, where the drying temperature is about 108° C. and the drying time is about 10 hours.
(2) The dried PA6 granules are fed into a screw extruder to be melted. The antibacterial masterbatch is accurately measured with a dosing pump, and fed together with dried PET granules into another screw extruder to be melted. The melting temperature applied for the PA6 granules is about 260° C., and the melting temperature applied for the antibacterial masterbatch and PET granules is about 285° C. The pressure of the screw extruders is 9.5 MPa. The amount of the antibacterial masterbatch is about 1.5 wt % of the total granules, and the weight ratio of the PET granules and PA6 granules is 50:50.
(3) The two melted materials are respectively measured with melt dosing pumps and then fed to a spinning manifold, and co-spun using an orange-shape type spinning pack to form the microfibers. The pressure of the melt material in the spinning pack is about 180 MPa. The spinning speed is about 3000 m/min.
(4) The spun fibers are then pulled and cooled to obtain the functionalized microfibers. Cooling is done by air cooling, where the air speed is about 0.35 m/min; the relative humidity of the air is about 72% and the temperature is about 20° C.
(5) The microfiber obtained above is used as the core and covered with soybean fibers to form the composite yarn, and the yarn is woven into a highly absorbent, quick-drying, super-soft, and natural-feeling fabric.

Process Example 2

(1) The PA6 and PET granules are separately dried. The aromatic masterbatch is dried in a separately drying tower, where the drying temperature is about 115° C. and the drying time is about 9 hours.
(2) The dried PA6 and PET granules are separately fed into two screw extruders to be melted. The aromatic masterbatch is accurately measured with a dosing pump, and respectively fed together with the PA6 granules and the PET granules into the screw extruders. The melting temperature applied for the PA6 granules is about 265° C., and the melting temperature applied for the PET granules is about 286° C. The pressure of the screw extruders is about 10 MPa. The weight ratio of the PET granules and PA6 granules is about 60:40; the amount of the aromatic masterbatch is about 2 wt % of the total granules and divided for the PET granules and PA6 granules according to their weight ratio.
(3) The two melted materials are respectively measured with melt dosing pumps and then fed to a spinning manifold, and co-spun using an orange-shape type spinning pack to form the microfibers. The pressure of the melt material in the spinning pack is about 220 MPa. The spinning speed is about 3100 m/min.
(4) The spun fibers are then pulled and cooled to obtain the functionalized microfibers. Cooling is done by air cooling, where the air speed is about 0.35 m/min; the relative humidity of the air is about 76% and the temperature is about 22° C.
(5) The microfiber obtained above is used as the core and covered with soybean fibers to form the composite yarn, and the yarn is woven into a highly absorbent, quick-drying, super-soft, and natural-feeling fabric.

Process Example 3

(1) The functionalized microfiber obtained in Process Example 1, step (4) is used as the core, and covered with cotton fibers to form the composite yarn. When forming the cover, the tension in the core fibers is greater than the tension in the covering fibers. Low hardness, high elasticity rubber rollers are used in the covering step to improve the covering effect. Press bar clamp and collector are used to ensure that the core is located at optimum positions.
(2) The composite yarn is woven into a grey fabric. To make towels, the composite yarn is woven to form the ground fabric and the terry of the grey fabric of the towel.
(3) The grey fabric is dyed, dried, and sewed to obtain the highly absorbent, quick-drying, super-soft and natural-feeling functionalized fabric. Before the dyeing process, the grey fabric undergoes an alkaline reduction treatment (causticization). The temperature for the alkaline reduction treatment is about 105° C. and the alkaline concentration is about 6.5 g/L.

Process Example 4

(1) The PA6 and PET granules are separately dried. The antibacterial masterbatch is dried in a separately drying tower, where the drying temperature is about 112° C. and the drying time is about 9.5 hours.
(2) The dried PA6 granules are fed into a screw extruder to be melted. The antibacterial masterbatch is accurately measured with a dosing pump, and fed together with dried PET granules into another screw extruder to be melted. The melting temperature applied for the PA6 granules is about 262° C., and the melting temperature applied for the antibacterial masterbatch and PET granules is about 288° C. The pressure of the screw extruders is about 9 MPa. The amount of the antibacterial masterbatch is about 2 wt % of the total granules, and the weight ratio of the PET granules and PA6 granules is about 70:30.
(3) The two melted materials are respectively measured with a melt dosing pump and then fed to a spinning manifold, and co-spun using an orange-shape type spinning pack to form the microfibers. The pressure of the melt material in the spinning pack is about 215 MPa. The spinning speed is about 3050 m/min.
(4) The spun fibers are then pulled and cooled to obtain the functionalized microfibers. Cooling is done by air cooling, where the air speed is about 0.45 m/min; the relative humidity of the air is about 75% and the temperature is about 22° C.
(5) The microfiber obtained above is used as the core and covered with soybean fibers to form the composite yarn. When forming the cover, the tension in the core fibers is greater than the tension in the covering fibers. Low hardness, high elasticity rubber rollers are used in the covering step to improve the covering effect. Press bar clamp and collector are used to ensure that the core is located at optimum positions.
(6) The composite yarn is woven into a grey fabric. The grey fabric may be a flat fabric or towel. To make towels, the composite yarn is woven to form the ground fabric and the terry of the grey fabric of the towel.
(7) The grey fabric is dyed, dried, and sewed to obtain the highly absorbent, quick-drying, super soft and natural-feel functionalized fabric. Before the dyeing process, the grey fabric undergoes an alkaline reduction treatment (causticization). The temperature for the alkaline reduction treatment is about 115° C. and the alkaline concentration is about 5.5 g/L.
In another process example, the amount of the antibacterial masterbatch is about 3 wt % of the total granules, and the weight ratio of the PET granules and PA6 granules is about 55:45.
Properties of some fabric products made using the above exemplary manufacturing processes are summarized in the table below:

TABLE 1

	absorption	Absorbing
Product	ratio	speed	antibacterial effect

Process	374%	3 s	Staphylococcus aureus
Example 1			(MRSA) > 99.9%;
			E. coli > 99.9
Process	395%	3 s
Example 2
Process	390%	3 s	Staphylococcus aureus
Example 3			(MRSA) > 99.9%;
			E. coli > 99.9
Process	384%	3 s
Example 4

Properties of some towel products made using the above exemplary manufacturing processes are summarized in the table below:

TABLE 2

	absorption	Absorbing
Product	ratio	speed	antibacterial effect

Process	740%	4 s	Staphylococcus aureus
Example 3			(MRSA) > 99.9%
(Towel)
Process	725%	4 s	Staphylococcus aureus
Example 4			(MRSA) > 99.9%
(Towel)

The composite yarns and fabrics made from such yarns have the desirable properties of both polyester fibers and polyamide fibers. Moreover, because after the splitting process the linear mass density of the filaments of the microfiber core is less than or equal to 0.55 dtex, the fabric is super soft and has high absorbance due to capillary effect; there absorbance can be as high as 4 to 5 times that of similar cotton products. Meanwhile, because of the natural fibers that form the cover layer, the fabrics have the soft feel of natural fibers, and are comfortable to wear. Further, the functional materials added in the microfiber core give the fabrics special properties such as antibacterial, UV-blocking and aromatic properties. Cloths made of such fabrics are safe for skin contact and can also prevent bacterial growth and undesirable odor generated by bacterial growth.
It will be apparent to those skilled in the art that various modification and variations can be made in the composite yarns, textile and related manufacturing methods of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. (canceled)

2. A composite yarn comprising:

a core formed of microfibers, wherein each microfiber has two components which are different materials, the two components being held together in an interleaved arrangement in a cross-sectional view; and

a covering layer formed of natural fibers which are twisted and surround and cover the core.

3. The composite yarn of claim 2, wherein the two components are polyamide 6 and polyester.

4. The composite yarn of claim 3, wherein either the polyamide 6 component or the polyester component or both are functionalized with a functional material.

5. The composite yarn of claim 4, wherein the functional material is selected from a group consisting of antibacterial materials, aromatic materials, and UV-blocking materials.

6. The composite yarn of claim 21, wherein the microfibers are separate filaments of polyamide 6 and polyester which have a linear mass density of less than or equal to 0.55 dtex.

7. The composite yarn of claim 6, wherein either the polyamide 6 filaments or the polyester filaments or both are functionalized with the functional material.

8. The composite yarn of claim 21, wherein the functional material is selected from a group consisting of antibacterial materials, aromatic materials, and UV-blocking materials.

9. The composite yarn of claim 2, wherein the natural fibers of the covering layer are selected from a group consisting of cotton fibers, hemp fibers, wool fibers, bamboo fibers, silk fibers, and soybean fibers.

10. A fabric made of the composite yarn of claim 2.

11.-20. (canceled)

21. A composite yarn comprising:

a core formed of microfibers, wherein at least some of the microfibers are functionalized with a functional material; and

22. The composite yarn of claim 21, wherein the at least some of the microfibers contain the functional material melted therein.

23. The composite yarn of claim 21, wherein the natural fibers of the covering layer are selected from a group consisting of cotton fibers, hemp fibers, wool fibers, bamboo fibers, silk fibers, and soybean fibers.

24. A fabric made of the composite yarn of claim 21.

25. A composite yarn comprising:

a core formed of microfibers which include separate filaments of polyamide 6 and filaments of polyester, the filaments having a linear mass density of less than or equal to 0.55 dtex, wherein either the polyamide 6 filaments or the polyester filaments or both are functionalized with a functional material selected from a group consisting of antibacterial materials, aromatic materials, and UV-blocking materials; and

26. The composite yarn of claim 25, wherein either the polyamide 6 or the polyester or both contains the functional material melted therein.

27. The composite yarn of claim 25, wherein the natural fibers of the covering layer are selected from a group consisting of cotton fibers, hemp fibers, wool fibers, bamboo fibers, silk fibers, and soybean fibers.

28. A fabric made of the composite yarn of claim 25.