Polylactic acid composite yarn and preparation method and application thereof

Abstract

The invention discloses a polylactic acid composite yarn and a preparation method and application thereof. The polylactic acid composite yarn comprises two kinds of polylactic acid short fibers with different fineness and / or lengths, on one hand, the natural characteristics of biodegradability, reproducibility, skin-friendly bacteriostasis and ecological environmental protection of polylactic acid are kept, and on the other hand, the moisture absorption and quick drying performance is improved. The method for preparing the composite yarn is simple and convenient to operate, easy to implement and suitable for large-scale industrial application.

Description

[0001] This application is a divisional application of the patent application with application number 202110555748.8, application date May 21, 2021, and invention name “A polylactic acid composite yarn, preparation method and application thereof”. Technical Field

[0002] The invention relates to a moisture-absorbing and quick-drying polylactic acid composite yarn, a method for preparing the composite yarn and application of the composite yarn, and belongs to the technical field of textile product manufacturing. Background Art

[0003] As fitness awareness has become more popular, exercise has become a hot topic. When people exercise vigorously, they secrete a lot of sweat. If the sweat and moisture cannot diffuse quickly, it will cause uncomfortable dampness and stickiness to the human body. Therefore, people have higher and higher requirements for the comfort of clothing, especially thermal and wet comfort. In recent years, textiles with moisture absorption and quick drying properties have been loved and sought after by the world for their excellent properties such as moisture conduction, quick drying and comfort. At the same time, the commercial demand for moisture absorption and quick drying yarns has also increased sharply.

[0004] In addition to the moisture absorption and quick-drying function, consumers are also paying more and more attention to the environmental protection and safety of clothing fabrics. The market is in urgent need of an eco-friendly moisture absorption and quick-drying yarn. Traditional yarn production processes can no longer meet market demand, but some biodegradable and environmentally friendly fibers such as polylactic acid staple fibers can well increase the added value of products. Polylactic acid (PLA) fiber is a new type of green fiber made from starch-containing agricultural products such as corn, wheat, and beets, which is fermented to produce lactic acid, then polymerized to form polylactic acid, and made by melt spinning. Polylactic acid staple fibers not only have the advantages of biodegradability, renewability, abundant raw material sources, low energy consumption, and environmental compatibility, but also have excellent wearing characteristics such as skin-friendly antibacterial and comfortable and smooth, and have high economic value. However, although polylactic acid staple fibers have excellent moisture conduction properties, their hygroscopicity is poor, and it is difficult for a single component to achieve the performance requirements of moisture absorption and quick drying. One solution is to use polylactic acid staple fibers and other hydrophilic fibers blended to improve moisture absorption and quick drying performance, such as cotton fibers and viscose fibers. However, since these fibers are prone to mold and fungus after absorbing moisture, the blended yarn formed loses its antibacterial properties, so that the original excellent antibacterial properties of polylactic acid cannot be fully utilized and cannot meet the multifunctional requirements of the yarn.

[0005] At present, there is no patent technology or related report on the preparation of eco-friendly polylactic acid moisture-absorbing and quick-drying yarn using two groups of pure polylactic acid staple fibers as raw materials. The relevant patents of moisture-absorbing and quick-drying yarn generally improve the moisture-absorbing and quick-drying performance of the yarn by adopting physical or chemical modification methods, or blending hygroscopic fibers with hydrophobic moisture-conducting fibers. The yarn involved in the Chinese patent (publication number CN107858778A) "A method for preparing moisture-absorbing and perspiration-wicking yarn" is first modified by plasma surface treatment of wool and chemical methods to modify polyester fibers, and then wool fibers and modified polyester are combed by combing machines and drawn by spinning machines to form yarns with moisture-absorbing and perspiration-wicking functions. The yarn involved in the Chinese patent (publication number CN110373769A) "A method for preparing moisture-absorbing and perspiration-wicking blended yarn" is blended by using moisture-absorbing and perspiration-wicking polyester shaped fibers and modal fibers to achieve moisture-absorbing and perspiration-wicking functions and skin-friendly and comfortable performance. The Chinese patent (publication number CN110257986A) "A kind of axial non-uniform structure moisture-absorbing and quick-drying yarn" provides a structure in which the fiber components are non-uniformly distributed along the axial direction of the yarn. By using hydrophilic fibers and hydrophobic fibers to be distributed alternately along the axial direction of the yarn, the size of the capillaries inside the yarn is different, thereby generating a differential capillary effect, so as to give the yarn moisture-absorbing and quick-drying properties.

[0006] It can be seen from the above-mentioned related patents that the existing moisture-absorbing and quick-drying yarns have very complicated processes such as chemical modification and finishing of fibers, and are also contrary to the concept of environmental protection, and may even reduce the air permeability of the fabric during the finishing process; and the use of hydrophilic fibers and hydrophobic fibers blended to form moisture-absorbing and quick-drying yarns will inevitably destroy the original excellent properties of the fibers during the spinning process, such as antibacterial properties, air permeability, comfort, etc., and the scope of use is limited; the process design of the existing multi-layer structure moisture-absorbing and quick-drying yarns is very complex, the spinning method is special, and the production difficulty is high, making it difficult to achieve large-scale production. Summary of the invention

[0007] The purpose of the present invention is to provide a polylactic acid composite yarn, a method for preparing the composite yarn, and an application of the composite yarn in view of one or more problems existing in the prior art. The polylactic acid composite yarn of the present invention maintains the natural characteristics of polylactic acid, which is biodegradable, renewable, skin-friendly, antibacterial, and eco-friendly, on the one hand, and improves the moisture absorption and quick-drying performance on the other hand. The method for preparing the composite yarn provided by the present invention is simple to operate, easy to implement, and suitable for large-scale industrial applications.

[0008] According to a first aspect of the present invention, a polylactic acid composite yarn is provided, which comprises a core layer and an outer layer covering the core layer, wherein the core layer comprises a first polylactic acid staple fiber, and the outer layer comprises a second polylactic acid staple fiber; and preferably, the first polylactic acid staple fiber and the second polylactic acid staple fiber have different fineness and / or length.

[0009] According to a second aspect of the present invention, there is provided a method for preparing the composite yarn according to the first aspect of the present invention, comprising the following steps:

[0010] (1) providing a first polylactic acid short fiber raw material and a second polylactic acid short fiber raw material;

[0011] (2) preparing the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material into a first polylactic acid roving and a second polylactic acid roving respectively;

[0012] (3) The first polylactic acid roving and the second polylactic acid roving are combined and subjected to drawing and twisting treatment to obtain a polylactic acid composite yarn including a core layer and an outer layer covering the core layer, wherein the core layer includes the first polylactic acid staple fiber, and the outer layer includes the second polylactic acid staple fiber.

[0013] According to a third aspect of the present invention, there is provided use of the composite yarn according to the first aspect of the present invention or the composite yarn prepared by the method according to the second aspect of the present invention in the field of textile product manufacturing.

[0014] According to a fourth aspect of the present invention, there is provided a fabric, which is prepared by the composite yarn according to the first aspect of the present invention or the composite yarn prepared by the method according to the second aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the accompanying drawings, like reference numerals refer to the same or functionally similar elements, and the accompanying drawings contain graphics of certain embodiments to further illustrate and clarify the above and other aspects, advantages and features of the present disclosure. It should be understood that these drawings depict exemplary embodiments and are not intended to limit the scope of the present disclosure. Through the use of the accompanying drawings, the present disclosure will be described and explained with additional specificity and detail.

[0016] Figure 1 A schematic diagram of the structure of a polylactic acid composite yarn provided according to some embodiments of the present invention;

[0017] Figure 2 A schematic diagram of a cross-sectional structure of a polylactic acid composite yarn provided according to some embodiments of the present invention;

[0018] exist Figure 1 and Figure 2 , 1 represents the first polylactic acid short fiber, and 2 represents the second polylactic acid short fiber;

[0019] Figure 3 Schematic diagram of the spinning process of the polylactic acid composite yarn provided according to some embodiments of the present invention, wherein a represents the first polylactic acid roving, b represents the second polylactic acid roving, 3 represents the back roller, 4 represents the middle roller, and 5 represents the front roller;

[0020] Figure 4 The present invention provides a curve chart of the wicking height test results of the polylactic acid composite yarn provided according to some embodiments of the present invention, wherein Curve 1, Curve 2 and Curve 3 are respectively curves showing the wicking height changes over time of the composite yarns prepared in Example 1, Example 2 and Example 3, Curve 4 is a curve showing the wicking height changes over time of the polylactic acid yarn prepared in Comparative Example 1, and Curve 5 is a curve showing the wicking height changes over time of the polylactic acid yarn prepared in Comparative Example 2. DETAILED DESCRIPTION

[0021] The present invention is described in more detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and should not be construed as limiting the present invention.

[0022] definition

[0023] References in the specification to "one embodiment", "preferred embodiment", "exemplary embodiment", etc., mean that the described embodiment may include specific features, structures, or characteristics, but not every embodiment may include specific features, structures, or characteristics. Moreover, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure, or characteristic is described in conjunction with an embodiment, whether or not it is explicitly described, it is deemed that the effect of applying the feature, structure, or characteristic to other embodiments is within the knowledge of those skilled in the art.

[0024] When mentioned in the specification, "plurality", "multiple roots" and the like refer to at least two or two roots, for example, three or three roots, four or four roots, five or no roots, six or six roots... and the like.

[0025] Any numerical value mentioned in the present invention, if there is only an interval of two units between any minimum value and any maximum value, includes all values ​​from the minimum value to the maximum value each time increasing by one unit. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is declared to be 50-90, in this specification it means that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as a unit. These are just some specially specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0026] As used herein, unless otherwise specified, the term "a / kind" is used to include one / kind or more / kinds, and the term "or" is used to represent a non-exclusive "or". In addition, when the terms used herein are not otherwise defined, they should be understood to be used for descriptive purposes only and not for limiting purposes. In addition, all publications, patents, and patent documents mentioned in the specification are incorporated herein by reference in their entirety, just as if they were separately incorporated by reference. If there is a discrepancy between the usage of this document and those documents incorporated by reference, the usage in the cited references should be considered to supplement this document. For irreconcilable inconsistencies, the usage in this article shall prevail.

[0027] In the manufacturing method described in the specification, except for the explicit description of the time or operation sequence, the steps can be implemented in any order without departing from the principles of the present invention. The claim indicates that one step is implemented first, and then several other steps are implemented. It should be considered that the first step is implemented before any other step, and the other steps can be performed in any other step unless the order is further listed in the step in the other step. For example, a claim stating "step A, step B, step C, step D, and step E" should be interpreted to mean that step A is implemented first, step E is implemented last, and steps B, C, and D are implemented in steps A and E. They can be performed in any order, and these orders still fall within the literal scope of the process claimed for protection by the claims. Similarly, given steps or sub-steps can be repeated.

[0028] Polylactic acid composite yarn

[0029] According to some embodiments of the present invention, there is provided a polylactic acid composite yarn, comprising a core layer and an outer layer covering the core layer, wherein the core layer comprises a first polylactic acid staple fiber or is substantially composed of the first polylactic acid staple fiber, and the outer layer comprises a second polylactic acid staple fiber or is substantially composed of the second polylactic acid staple fiber; and preferably, the first polylactic acid staple fiber and the second polylactic acid staple fiber have different fineness and / or length. In some embodiments, the polylactic acid composite yarn of the present invention consists of a core layer and an outer layer covering the core layer.

[0030] The present invention does not specifically limit the source of the polylactic acid staple fibers. Various commercially available or self-synthesized polylactic acid staple fibers are suitable for the present invention. For example, polylactic acid can be prepared by ring-opening polymerization of lactide (cyclic dimer of lactic acid) or direct polymerization of lactic acid, and then prepared into polylactic acid staple fibers by a spinning process known in the art. In some embodiments, the polylactic acid composite yarn of the present invention does not contain raw materials other than polylactic acid staple fibers.

[0031] In some embodiments, the first polylactic acid staple fibers and the second polylactic acid staple fibers have different finenesses.

[0032] In some embodiments, the fineness of the first polylactic acid staple fibers is smaller than the fineness of the second polylactic acid staple fibers.

[0033] In some embodiments, the fineness of the first polylactic acid staple fibers is smaller than that of the second polylactic acid staple fibers, and the first polylactic acid staple fibers and the second polylactic acid staple fibers are the same in length.

[0034] In some embodiments, the first polylactic acid staple fibers and the second polylactic acid staple fibers have different lengths.

[0035] In some embodiments, the length of the first polylactic acid staple fiber is greater than the length of the second polylactic acid staple fiber.

[0036] In some embodiments, the length of the first polylactic acid staple fibers is greater than that of the second polylactic acid staple fibers, and the first polylactic acid staple fibers and the second polylactic acid staple fibers have the same fineness.

[0037] In some embodiments, the first polylactic acid staple fibers and the second polylactic acid staple fibers are different in fineness and length.

[0038] In some embodiments, the fineness of the first polylactic acid staple fibers is smaller than the fineness of the second polylactic acid staple fibers, and the length of the first polylactic acid staple fibers is greater than the length of the second polylactic acid staple fibers.

[0039] In some embodiments, the content of the first polylactic acid staple fibers in the core layer is greater than 50%, for example, greater than 60%, greater than 70%, greater than 80%, greater than 90%, greater than 95%, greater than 98% or greater than 99%.

[0040] In some embodiments, the content of the second polylactic acid staple fibers in the outer layer is greater than 50%, for example, greater than 60%, greater than 70%, greater than 80%, greater than 90%, greater than 95%, greater than 98% or greater than 99%.

[0041] In some embodiments, the second polylactic acid staple fibers partially or completely cover the first polylactic acid staple fibers in a spiral shape.

[0042] In some embodiments, the second polylactic acid staple fiber partially covers the first polylactic acid staple fiber in a spiral shape along the axial direction of the yarn core, thereby forming a covered yarn with an incomplete covering structure.

[0043] In some embodiments, the second polylactic acid staple fibers wrap around the first polylactic acid staple fibers in a parallel spiral shape along the axial direction of the yarn core.

[0044] In some embodiments, the second polylactic acid staple fibers do not completely cover the first polylactic acid staple fibers.

[0045] In some embodiments, the coverage rate of the second polylactic acid staple fibers on the first polylactic acid staple fibers is 50% or more, for example, 55% or more, 60% or more, or 65% or more.

[0046] In some embodiments, the mass ratio of the first polylactic acid staple fiber to the second polylactic acid staple fiber is (20-80): (80-20).

[0047] In some embodiments, the mass ratio of the first polylactic acid staple fiber to the second polylactic acid staple fiber is (35-65): (65-35).

[0048] In some embodiments, the mass ratio of the first polylactic acid staple fiber to the second polylactic acid staple fiber is (45-55):(55-45).

[0049] In some embodiments, the first polylactic acid staple fiber and the second polylactic acid staple fiber are polylactic acid staple fibers that have undergone a roving preparation process and a drafting process. For example, the polylactic acid staple fibers that have undergone a roving preparation process and a drafting process can be in the form of whiskers, which are, for example, roughly parallel.

[0050] In some further embodiments, the first polylactic acid staple fibers and the second polylactic acid staple fibers that have been stretched are combined and twisted to form the core layer and the outer layer covering the core layer.

[0051] In some embodiments, the cross-sections of the first polylactic acid staple fiber and the second polylactic acid staple fiber are independently selected from circular and irregular cross-sections, preferably selected from circular, Y-shaped, and cross-shaped cross-sections.

[0052] Figure 1 and Figure 2 The structure diagram of the polylactic acid composite yarn provided according to some embodiments of the present invention is schematically given. As shown in the figure, the composite yarn includes a core layer and an outer layer covering the core layer, wherein the core layer includes a first polylactic acid staple fiber 1, and the outer layer includes a second polylactic acid staple fiber 2, wherein the fineness of the first polylactic acid staple fiber 1 is less than that of the second polylactic acid staple fiber 2, and the second polylactic acid staple fiber 2 partially covers the first polylactic acid staple fiber 1 in a spiral shape, thereby forming an incompletely covered structure; wherein, most, for example, more than 50%, of the first polylactic acid staple fibers 1 are located in the core layer, and most, for example, more than 50% of the second polylactic acid staple fibers 2 are located in the outer layer.

[0053] Without intending to be limited by the constraints of theory, in the polylactic acid composite yarn of the preferred embodiment of the present invention, the thinner and longer fibers are located in the yarn core layer, and the thicker and shorter fibers are concentrated in the yarn outer layer, then the capillary diameter of the yarn core layer is smaller than the capillary diameter of the yarn outer layer. According to the differential capillary effect mechanism, liquid is more likely to enter the yarn core layer from the yarn outer layer. At the same time, polylactic acid staple fibers have excellent moisture conductivity, and the polar oxygen bonds in the fiber molecules are connected with water molecules to accelerate the transfer of water vapor in the fiber, so that the liquid diffuses rapidly along the inner layer of the yarn, and further transports and evaporates rapidly to the outer surface of the yarn. At the same time, the incomplete coating structure enhances the capillary effect of the fiber in the fabric, making up for the relatively weak hygroscopic performance of polylactic acid staple fibers, so that pure polylactic acid staple fiber yarns can also achieve efficient moisture absorption and quick drying effects.

[0054] Preparation method of polylactic acid composite yarn

[0055] According to some embodiments of the present invention, there is provided a method for preparing the aforementioned polylactic acid composite yarn of the present invention, comprising the following steps:

[0056] (1) providing a first polylactic acid short fiber raw material and a second polylactic acid short fiber raw material;

[0057] (2) preparing a first polylactic acid roving and a second polylactic acid roving from the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material respectively;

[0058] (3) The first polylactic acid roving and the second polylactic acid roving are combined and subjected to drawing and twisting treatment to obtain a polylactic acid composite yarn including a core layer and an outer layer covering the core layer, wherein the core layer includes the first polylactic acid staple fiber, and the outer layer includes the second polylactic acid staple fiber.

[0059] In some embodiments, the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material have different fineness and / or length.

[0060] In some embodiments, the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material have different finenesses.

[0061] In some embodiments, the fineness of the first polylactic acid staple fiber raw material is smaller than the fineness of the second polylactic acid staple fiber raw material.

[0062] In some embodiments, the fineness of the first polylactic acid staple fiber raw material is smaller than the fineness of the second polylactic acid staple fiber raw material, and the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material have the same length.

[0063] In some embodiments, the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material have different lengths.

[0064] In some embodiments, the length of the first polylactic acid staple fiber raw material is greater than the length of the second polylactic acid staple fiber raw material.

[0065] In some embodiments, the length of the first polylactic acid staple fiber raw material is greater than the length of the second polylactic acid staple fiber raw material, and the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material have the same fineness.

[0066] In some embodiments, the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material have different fineness and length.

[0067] In some embodiments, the fineness of the first polylactic acid staple fiber raw material is smaller than the fineness of the second polylactic acid staple fiber raw material, and the length of the first polylactic acid staple fiber raw material is greater than the length of the second polylactic acid staple fiber raw material.

[0068] In some embodiments, the length of the first polylactic acid staple fiber raw material is 30-70 mm, for example, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm and any value therebetween, preferably 35-45 mm.

[0069] In some embodiments, the fineness of the first polylactic acid staple fiber raw material is 1.0-3.0 denier, for example, 1.0 denier, 1.5 denier, 2.0 denier, 2.5 denier, 3.0 denier and any value therebetween, preferably 1.5-2.5 denier.

[0070] In some embodiments, the length of the second polylactic acid staple fiber raw material is 20-60 mm, for example, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm and any value therebetween, preferably 30-40 mm.

[0071] In some embodiments, the fineness of the second polylactic acid staple fiber raw material as raw material is 1.5-4.5 denier, for example, 1.5 denier, 2.0 denier, 2.5 denier, 3.0 denier, 3.5 denier, 4.0 denier, 4.5 denier and any value therebetween, preferably 2-3.5 denier.

[0072] According to the composite yarn of the present invention, the dosage of the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material can be adjusted to prepare composite yarns with different coating degrees and properties.

[0073] In some embodiments, the mass ratio of the first polylactic acid staple fiber raw material to the second polylactic acid staple fiber raw material is (20-80):(80-20), for example, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, 80:20 and any value therebetween, preferably (35-65):(65-35), and more preferably (45-55):(55-45).

[0074] According to some embodiments of the present invention, the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material are independently selected from circular and irregular cross-section polylactic acid staple fibers, preferably selected from circular, Y-shaped, and cross-shaped cross-section polylactic acid staple fibers.

[0075] The method for preparing roving from short fiber raw materials in step (2) of the present invention is not particularly limited and can be carried out by methods well known to those skilled in the art.

[0076] In some exemplary embodiments, the step (2) comprises:

[0077] The first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material are respectively subjected to the processes of opening, removing impurities, combing and drawing to prepare the first polylactic acid roving and the second polylactic acid roving.

[0078] In some preferred embodiments, the fineness of the first polylactic acid roving and the second polylactic acid roving may be the same or different.

[0079] In some embodiments, the fineness of the first polylactic acid roving is 250-350 tex, for example, 250 tex, 260 tex, 270 tex, 280 tex, 290 tex, 300 tex, 310 tex, 320 tex, 330 tex, 340 tex, 350 tex and any value therebetween, preferably 260-310 tex.

[0080] In some embodiments, the fineness of the second polylactic acid staple fiber roving is 250-350 tex, for example, 250 tex, 260 tex, 270 tex, 280 tex, 290 tex, 300 tex, 310 tex, 320 tex, 330 tex, 340 tex, 350 tex and any value therebetween, preferably 260-310 tex.

[0081] In some preferred embodiments, the roving preparation parameters in step (2) are as follows:

[0082] The quantitative weight of the first polylactic acid roving and the second polylactic acid roving is 2.6 g / 10 m; and / or the twist coefficient is 104; and / or the twist is 6.5 twists / 10 cm; and / or the roller gauge is 11 mm × 29.5 mm × 46.5 mm; and / or the mechanical drafting is 11.45 times; and / or the rear zone drafting is 1.21 times.

[0083] According to the preparation method of the present invention, the method of spinning the two rovings into the composite yarn in step (3) is not particularly limited and can be carried out by methods well known to those skilled in the art, such as ring spinning, compact spinning, solo spinning, air spinning and the like.

[0084] In some preferred embodiments, the first polylactic acid roving and the second polylactic acid roving are spun into the polylactic acid composite yarn using a ring spinning process.

[0085] Ring spinning is the most widely used and common spinning method in the current market. Ring spinning refers to the process in which the fiber strips after drafting of the sliver or roving are introduced through the rotating ring wire ring. The winding speed of the bobbin is faster than that of the wire ring. The cotton yarn is twisted into fine yarn and is widely used in various short fiber spinning projects. For example, in carding, combing and blending, the wire ring is driven by the bobbin through the yarn strip to rotate around the steel collar for twisting. At the same time, the friction of the steel collar makes its speed slightly lower than that of the bobbin to be wound. The spinning speed is high, and the shape of the ring yarn is a conical spiral line with most of the fibers transferring inside and outside, so that the fibers are entangled and connected inside and outside in the yarn. The yarn has a compact structure and high strength, which is suitable for various products such as thread making, weaving and knitting.

[0086] In some specific embodiments, in step (3), the first polylactic acid roving and the second polylactic acid roving are stretched and twisted in the same channel to obtain the composite yarn.

[0087] In some specific embodiments, the step (3) is performed as follows:

[0088] The first polylactic acid roving and the second polylactic acid roving are simultaneously fed into the same channel of the bell mouth in front of the rear roller of the spinning frame, and then spun into the polylactic acid composite yarn through drawing and twisting treatment.

[0089] In some preferred embodiments, in step (3), a Zinser 351 spinning frame is used to prepare the polylactic acid composite yarn.

[0090] In some preferred embodiments, the spinning parameters in step (3) are as follows: the fine yarn linear density is 14.8 tex; and / or the twist is 3.6 twists / 10 cm; and / or the spindle speed is 8000 rpm.

[0091] In some embodiments, the method further comprises selectively adding a bundling or covering aid treatment in step (3) to promote the formation of an incomplete covering structure of the composite yarn.

[0092] Figure 3 A schematic diagram of the spinning process (step (3)) of the polylactic acid composite yarn provided according to some embodiments of the present invention is schematically given, wherein the first polylactic acid roving a and the second polylactic acid roving b are simultaneously fed into the same channel of the bell-shaped mouth in front of the rear roller 3 of the spinning frame, and after being combined, they are successively stretched by the middle roller 4 and the front roller 5, and then spun into the polylactic acid composite yarn through a twisting process.

[0093] Without intending to be limited by the constraints of theory, in the method for preparing polylactic acid composite yarn of the preferred embodiment of the present invention, in the spinning process (especially spinning roving into spun yarn, for example, using a ring spinning process), thinner and longer fibers are easily transferred to the yarn core layer, and thicker and shorter fibers are easily concentrated in the outer layer of the yarn. The core layer of the composite yarn obtained thereby mainly includes thinner and longer fibers, while the outer layer mainly includes thicker and shorter fibers, and therefore the capillary diameter of the yarn core layer is smaller than the capillary diameter of the yarn surface layer. According to the differential capillary effect mechanism, liquid is more likely to enter the yarn core layer from the outer layer of the yarn. At the same time, polylactic acid staple fibers have excellent moisture conductivity, and the polar oxygen bonds in the fiber molecules are connected to water molecules to accelerate the transfer of water vapor in the fiber, so that the liquid diffuses rapidly along the inner layer of the yarn, and is further rapidly transported and evaporated to the outer surface of the yarn. At the same time, the incomplete covering structure improves the capillary effect of the fiber in the fabric, making up for the defect of poor moisture absorption performance of polylactic acid staple fiber, so that pure polylactic acid staple fiber yarn can also achieve efficient moisture absorption and quick drying effect.

[0094] As used herein, the term "essentially composed of..." or "mainly includes" means including the listed ingredients, but may also include other components that are not listed and do not affect the properties of the yarn or are necessarily present. In some embodiments, the content of these other components is less than 50wt%, for example, less than 40wt%, 30wt%, 20wt%, 10wt%, 5wt%, 2wt%, 1wt%, 0.5wt%, etc.

[0095] As used herein, the term "essentially composed of first polylactic acid staple fibers" means that the core layer includes the first polylactic acid staple fibers as the main component in an amount of 50wt% or more (for example, 60wt%, 70wt%, 80wt%, 90wt% or more), and may also include a small amount (less than 50wt%, for example, less than 40wt%, 30wt%, 20wt%, 10wt%, 5wt%, 2wt%, 1wt%, 0.5wt%, etc.) of second polylactic acid staple fibers, which can be incorporated into the core layer during the twisting process.

[0096] As used herein, the term "essentially composed of second polylactic acid staple fibers" means that the outer layer includes the second polylactic acid staple fibers as the main component in an amount of 50wt% or more (for example, 60wt%, 70wt%, 80wt%, 90wt% or more), and may also include a small amount (less than 50wt%, for example, less than 40wt%, 30wt%, 20wt%, 10wt%, 5wt%, 2wt%, 1wt%, 0.5wt%, etc.) of the first polylactic acid staple fibers, which can be incorporated into the outer layer during the twisting process.

[0097] Application of polylactic acid composite yarn

[0098] According to some embodiments of the present invention, there is provided application of the polylactic acid composite yarn of the present invention or the composite yarn prepared according to the method of the present invention in the field of textile product manufacturing.

[0099] The polylactic acid composite yarn of the present invention has obvious moisture absorption and quick drying effect, and also has the natural characteristics of polylactic acid short fibers, such as biodegradability, renewability, skin-friendly and antibacterial, soft touch, comfortable and smooth, and environmental compatibility. It can meet the market's multifunctional demand for yarn and has broad development prospects.

[0100] Moisture wicking, quick-drying fabric

[0101] According to some embodiments of the present invention, there is provided a fabric, which is prepared by the aforementioned polylactic acid composite yarn of the present invention or the composite yarn prepared by the aforementioned method of the present invention.

[0102] In some embodiments, the fabric is a moisture wicking quick drying fabric.

[0103] Example

[0104] Example 1

[0105] (1) providing a first polylactic acid staple fiber raw material having a fineness of 1.5 denier and a length of 38 mm and a second polylactic acid staple fiber raw material having a fineness of 2.0 denier and a length of 32 mm;

[0106] (2) preparing a first polylactic acid roving with a tex of 310 tex and a second polylactic acid roving with a tex of 260 tex from the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material provided in step (1), respectively;

[0107] (3) The first polylactic acid roving and the second polylactic acid roving were ring spun at a mass ratio of 55:45 to form a 40-count polylactic acid composite yarn-1 with an incompletely covered structure.

[0108] Example 2

[0109] (1) providing a first polylactic acid staple fiber raw material having a fineness of 1.5 denier and a length of 38 mm and a second polylactic acid staple fiber raw material having a fineness of 2.0 denier and a length of 32 mm;

[0110] (2) preparing a first polylactic acid roving with a tex of 260 tex and a second polylactic acid roving with a tex of 260 tex from the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material provided in step (1), respectively;

[0111] (3) The first polylactic acid roving and the second polylactic acid roving are ring-spun at a mass ratio of 50:50 to form a polylactic acid composite yarn-2 with a 40-count incompletely covered structure.

[0112] Example 3

[0113] (1) providing a first polylactic acid staple fiber raw material having a fineness of 1.5 denier and a length of 38 mm and a second polylactic acid staple fiber raw material having a fineness of 2.0 denier and a length of 32 mm;

[0114] (2) preparing a first polylactic acid roving having a tex of 260 tex and a second polylactic acid roving having a tex of 310 tex from the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material provided in step (1), respectively;

[0115] (3) The first polylactic acid roving and the second polylactic acid roving are ring spun at a mass ratio of 45:55 to form a 40-count polylactic acid composite yarn-3 with an incompletely covered structure.

[0116] Comparative Example 1

[0117] (1) Providing a polylactic acid staple fiber raw material with a fineness of 1.5 denier and a length of 38 mm;

[0118] (2) preparing a polylactic acid roving having a tex of 310 tex from the polylactic acid staple fiber raw material provided in step (1);

[0119] (3) Ring spinning a polylactic acid yarn obtained in step (2) to prepare a 40-count polylactic acid yarn-4.

[0120] Comparative Example 2

[0121] (1) Providing a polylactic acid staple fiber raw material with a fineness of 1.5 denier and a length of 38 mm;

[0122] (2) preparing a polylactic acid roving having a tex of 310 tex from the polylactic acid staple fiber raw material provided in step (1);

[0123] (3) Two polylactic acid rovings of step (2) are ring spun into 40-count polylactic acid yarn-5.

[0124] According to the wicking height test method specified in the standard FZ / T 01071-2008 "Test method for capillary effect of textiles", the wicking height of the five polylactic acid composite yarns described in the above embodiments and comparative examples was tested to confirm that the polylactic acid composite yarn of the present invention has the effect of moisture absorption and quick drying. The specific test results are as follows: Figure 4 As shown. Figure 4 In the figure, Curve 1, Curve 2, and Curve 3 are curves showing the variation of the wicking height of the yarns prepared in Example 1, Example 2, and Example 3 respectively over time, Curve 4 is a curve showing the variation of the wicking height of a yarn made of a single polylactic acid roving by ordinary ring spinning (the yarn prepared in Comparative Example 1) over time. Curve 5 is a curve showing the variation of the wicking height of a yarn made of two identical polylactic acid rovings by ordinary ring spinning (the yarn prepared in Comparative Example 2) over time. Figure 4 It can be seen that the liquid rises to a height of 26 mm along the yarn prepared in Example 1 at 10 minutes, 29 mm along the yarn prepared in Example 2 at 10 minutes, and 29 mm along the yarn prepared in Example 3 at 10 minutes through capillary action, while the height of the polylactic acid yarn along the comparative example 1 is only 9 mm, and the height of the polylactic acid yarn along the comparative example 2 is only 15 mm, indicating that the polylactic acid composite yarn of the present invention has good hygroscopicity. At the same time, the polylactic acid staple fiber has excellent moisture conductivity, and the polar oxygen bonds in its fiber molecules are connected to water molecules to accelerate the transfer of water vapor in the fiber, so that the liquid diffuses rapidly along the inner layer of the yarn, and further rapidly transports and evaporates to the outer surface of the yarn, that is, the incompletely coated pure polylactic acid yarn has good moisture absorption and quick drying performance.

[0125] In practical application, the present invention can be designed to change the thickness, length, mass ratio, yarn density, twist and other parameters of the two polylactic acid staple fiber components according to specific needs, or polylactic acid staple fibers with special cross-sections can be used to optimize the moisture absorption and quick-drying effect of the final incompletely coated polylactic acid moisture-absorbing and quick-drying yarn.

[0126] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A polylactic acid composite yarn, comprising a core layer and an outer layer covering the core layer, wherein the core layer comprises a first polylactic acid staple fiber, and the outer layer comprises a second polylactic acid staple fiber; and preferably, the first polylactic acid staple fiber and the second polylactic acid staple fiber have different fineness and / or length.

2. The composite yarn according to claim 1, characterized in that The fineness of the first polylactic acid short fibers is smaller than the fineness of the second polylactic acid short fibers.

3. The composite yarn according to claim 1 or 2, characterized in that: The length of the first polylactic acid short fibers is greater than the length of the second polylactic acid short fibers.

4. The composite yarn according to any one of claims 1 to 3, characterized in that The fineness of the first polylactic acid staple fibers is smaller than that of the second polylactic acid staple fibers, and the length of the first polylactic acid staple fibers is greater than that of the second polylactic acid staple fibers.

5. The composite yarn according to any one of claims 1 to 4, characterized in that The second polylactic acid short fibers partially or completely cover the first polylactic acid short fibers in a spiral shape.

6. The composite yarn according to any one of claims 1 to 5, characterized in that The mass ratio of the first polylactic acid staple fibers to the second polylactic acid staple fibers is (20-80):(80-20), preferably (35-65):(65-35), and more preferably (45-55):(55-45).

7. The composite yarn according to any one of claims 1 to 6, characterized in that The cross-sections of the first polylactic acid staple fibers and the second polylactic acid staple fibers are independently selected from circular and irregular cross-sections, preferably selected from circular, Y-shaped, and cross-shaped cross-sections.

8. A method for preparing a composite yarn according to any one of claims 1 to 7, comprising the following steps: (1) providing a first polylactic acid short fiber raw material and a second polylactic acid short fiber raw material; (2) preparing the first polylactic acid staple fiber raw material and the second polylactic acid staple fiber raw material into a first polylactic acid roving and a second polylactic acid roving respectively; (3) The first polylactic acid roving and the second polylactic acid roving are combined and subjected to drawing and twisting treatment to obtain a polylactic acid composite yarn including a core layer and an outer layer covering the core layer, wherein the core layer includes the first polylactic acid staple fiber, and the outer layer includes the second polylactic acid staple fiber.

9. Use of the composite yarn according to any one of claims 1 to 7 or the composite yarn prepared by the method according to claim 8 in the field of textile product manufacturing.

10. A fabric, which is prepared by the composite yarn according to any one of claims 1 to 7 or the composite yarn prepared by the method according to claim 8; Preferably, the fabric is a moisture wicking quick drying fabric.

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