Recycled yarn made from waste separation membranes used in secondary batteries.

Abstract

This invention relates to yarn made from recycled waste separation membranes used in secondary batteries. [Solution] The present invention provides an environmentally friendly yarn by recycling a heat-resistant material-coated separation membrane for secondary batteries as a raw material, thereby reducing the enormous costs associated with the separate disposal process.

Description

Technical Field

[0001] The present invention relates to a raw yarn obtained by recycling a separator membrane for a secondary battery.

[0002] The present invention is the research result of the project "Commercialization of Raw Yarn Products for Automobile Interior Materials Recycled from Waste Separator Membranes (CCS) of Secondary Batteries", which was carried out as a research project (Green New Industry) supported by the Ministry of Environment's Small and Medium-sized Environmental Enterprise Commercialization Support Project in Korea. The project number is RQ2024010559, the project implementing agency is RightRoute Inc., and the research period is from April 1, 2024 to December 31, 2024.

Background Art

[0003] Lithium secondary batteries (hereinafter referred to as "secondary batteries") are based on high energy density, discharge voltage, and output stability, and their demand is increasing rapidly not only as a power source for mobile electronic devices but also for various immobility (E-mobility). Such secondary batteries are composed of a positive electrode material, a negative electrode material, an electrolyte, and a separator membrane that separates the positive electrode material and the negative electrode material.

[0004] The separator membrane is a film or sheet-like thin membrane made of an insulating material and has a thickness of about 5 to 15 μm. The separator membrane has a microporous structure containing a large number of fine pores that block the physical contact between the positive electrode material and the negative electrode material and serve as a passage for lithium ions to move between the two electrodes.

[0005] The separator membrane with such a structure has the same structure as Gore-Tex (registered trademark), a functional material, and can realize a moisture permeable and waterproof function and can be utilized as a functional material.

[0006] The separator membrane is defectively processed due to defects such as fine scratches in the production process for manufacturing secondary batteries or discarded due to overproduction. The amount of such separator membranes in the form of waste is gradually increasing with the explosive growth of secondary batteries.

[0007] Nevertheless, since the separation membranes are not recycled and are simply disposed of by incineration or crushing, it leads to resource waste and environmental pollution.

[0008] To address this issue, the applicant disclosed Korean Registered Patent No. 10-2406934 (Functional fabric made from recycled separation membranes for secondary batteries and method for manufacturing the same).

[0009] The present invention discloses a method for manufacturing upcycled functional fabrics, comprising the steps of (a) preparing a separation membrane sheet of a microporous structure that has been discarded due to defective processing or overproduction in the production process for secondary battery manufacturing, (b) supplying each sheet such that an adhesive sheet is interposed between the separation membrane sheet and a woven sheet to be layered on top of the separation membrane sheet, and (c) laminating the separation membrane sheet and the woven sheet so that they are bonded together by the melting of the adhesive sheet, wherein in step (b), each sheet is supplied while maintaining a constant tension, but the separation membrane sheet, adhesive sheet and woven sheet are all supplied at the same rate, and in step (c), the laminated structure, in which the separation membrane sheet, adhesive sheet and woven sheet are stacked in that order, is laminated under pressure in a predetermined temperature atmosphere.

[0010] However, the above technology is applicable to LiBS (Lithium Battery Separator) among the waste separation membranes of secondary batteries, and is not applicable to other types of waste separation membranes such as CCS (Ceramic Coated Separator) or other heat-resistant coated separation membranes.

[0011] In the case of CCS film, it cannot be recycled due to the ceramic components it contains, so not only is it completely discarded, but even downcycling has not been attempted. Therefore, there is a growing need for technology that can recycle it. If recycling of such coated separation membranes becomes possible, it is expected to make a significant contribution to the treatment of separation membrane waste. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Korean Registered Patent No. 10-2406934 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The present invention aims to provide yarn made from recycled waste separation membranes used in secondary batteries. [Means for solving the problem]

[0014] In this invention, one or more covering threads are covered around a core thread. The core yarn is a slit yarn comprising an ultrahigh molecular weight polyethylene (UHMWPE) layer and a heat-resistant coating layer formed on one surface of the UHMWPE layer. The present invention provides a composite yarn having a core thread width of 0.5 to 3 mm.

[0015] Furthermore, the present invention provides a step of S1) a core yarn which is a slit yarn including an ultra-high molecular weight polyethylene (UHMWPE) layer and a heat-resistant coating layer formed on one surface of the UHMWPE layer, and a step of applying twisting to the core yarn through a drawing process. S2) A step of joining the core thread of step S1) with the first covering thread while applying a twist, and S3) Includes the step of plying the ply yarn from step S2) while twisting the second covering yarn, The present invention provides a method for manufacturing a composite yarn in which the second covering yarn is joined to the first covering yarn in the opposite direction. [Effects of the Invention]

[0016] The present invention can provide an environmentally friendly functional raw yarn by recycling a separator for secondary batteries coated with a heat-resistant substance, and has the effect of reducing the huge cost in the process of separately disposing of it.

[0017] In addition, in the present invention, since the separator for secondary batteries has a low specific gravity and thus has the characteristic of light weight, various recycled products requiring light weight can be produced using the produced raw yarn.

[0018] Moreover, the composite yarn produced according to the present invention is excellent in strength due to the core yarn and has a low dimensional change rate, so there is almost no deformation in the form of the final fabric product. In addition, since the functional covering yarn is composite with the core yarn in the composite yarn, flame retardancy, water repellency, stain resistance, heat retention functionality, etc. can be realized, and various designs can be realized by composite with the design covering yarn.

Brief Description of the Drawings

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Modes for Carrying Out the Invention

[0020] The present invention relates to a raw yarn obtained by recycling a waste separation membrane for a secondary battery and a composite yarn using the same.

[0021] Hereinafter, the raw yarn and the composite yarn obtained by recycling the waste separation membrane according to the present invention will be described more specifically.

[0022] In the present invention, the raw yarn obtained by recycling the waste separation membrane is a slit yarn produced by recycling a separation membrane for a secondary battery. Therefore, the raw yarn recycled in the present invention may be used interchangeably with the slit yarn.

[0023] In the present invention, the separation membrane for a secondary battery is a heat-resistant coated separation membrane (Coated Separator) film, and may have a structure in which a heat-resistant coating layer is coated on one surface of an ultrahigh molecular weight polyethylene (UHMWPE) membrane.

[0024] Therefore, the slit yarn according to the present invention includes ultrahigh molecular weight polyethylene (UHMWPE) and a heat-resistant coating layer formed on one surface of the UHMWPE.

[0025] In one embodiment, the weight average molecular weight of the ultrahigh molecular weight polyethylene (UHMWPE) may be 1,000,000 to 9,000,000 g / mol.

[0026] In one embodiment, the heat-resistant coating layer may include inorganic particles selected from the group consisting of ceramics, aluminum hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, alumina, boehmite, aluminum hydroxide, titanium dioxide, silica, zinc oxide, and clay, and a heat-resistant polymer resin selected from the group consisting of polyacrylonitrile, polysulfone, polyamide, polytetrafluoroethylene, polyurethane, polyaramid, and cellulose acetate, or two or more combinations thereof. Specifically, the heat-resistant coating layer may include ceramics.

[0027] In one embodiment, the content of the heat-resistant coating layer in the slit yarn may be 20 to 50 parts by weight, or 30 to 40 parts by weight, per 100 parts by weight of the UHMWPE layer.

[0028] In the present invention, the slit yarn can be manufactured by slitting a separation membrane for secondary batteries.

[0029] In one embodiment, the slit yarn can be manufactured by slitting it with a slit cutter specifically designed for separation membranes. Generally, the harder the film, the easier it is to cut it evenly and thinly, while flexible vinyl is difficult to cut at regular intervals. Therefore, micro-slitting technology is applied to products with thickness and rigidity, such as metallic yarn. The waste separation membrane film used in this invention has a thickness of approximately 12 μm, which is an extremely thin film compared to the typical film thickness (approximately 50 μm or more) handled by conventional slitting machines. Consequently, when using conventional technology, problems such as damage to the separation membrane due to slitting tension and uneven slitting intervals due to slippage may occur.

[0030] This invention utilizes a slit cutter made of a high-strength material compared to conventional slit cutters, enabling the slitting of secondary battery separation membrane films to fine specifications and at consistent intervals. In particular, a uniquely designed slitter FIX device has been created, allowing for zero error in the spacing of the slit threads, making it suitable for use as specialized equipment exclusively for secondary battery separation membranes.

[0031] Specifically, the slit cutter of the present invention can use a method in which the separation membrane is slit by an active rotating module of a blade with a fine cutter, rather than the conventional passive type in which the separation membrane passes through a fixed cutter.

[0032] In one embodiment, the width of the slit yarn may be adjusted to 0.5-3 mm, 1-2.5 mm, 1.5-2.5 mm, or within 2 mm.

[0033] In one embodiment, the thickness of the slit yarn may be 5 to 30 μm, 10 to 20 μm, or within 15 μm. The slit yarn having the aforementioned width and thickness can be firmly wound with a constant tension by a fine tension controller, thereby maintaining a stable yarn layer.

[0034] The slit yarn according to the present invention is used as a core yarn for composite yarns.

[0035] In this invention, the composite yarn includes a core yarn and one or more covering yarns that cover the core yarn.

[0036] In this invention, the core yarn is the original yarn located at the center of the composite yarn, providing strength to the composite yarn and enabling it to maintain its shape stably.

[0037] In one embodiment, the thickness of the core thread may be 100 to 400 denier.

[0038] In one embodiment, the core thread may be lead-free (TPM 0) and may have a twisted structure. If it has a twisted structure, it may have a twist of 50 to 300 TPM or 80 to 150 TPM per meter. In the present invention, by imparting a twisted structure to the core thread, the strength and uniformity of the composite yarn can be improved, and the resistance to friction can be increased.

[0039] In this invention, the covering yarn is a raw yarn that encases the core yarn. The covering yarn can impart functionality to the composite yarn, or it can impart design during the manufacturing of future fabrics.

[0040] In one embodiment, there may be one or more covering threads, specifically two or more, preferably two covering threads. When two or more covering threads are used, they may be referred to as the first covering thread and the second covering thread, etc., for distinction.

[0041] In one embodiment, the covering yarn may be a synthetic fiber yarn or a natural fiber yarn. The synthetic fiber may be one or more composite materials selected from the group consisting of polyester, nylon, acrylic, rayon, and polyethylene including UHMWPE, and the natural fiber may be one or more composite materials selected from the group consisting of cotton, wool, and silk.

[0042] In one embodiment, two covering threads may be used, and the covering thread that first covers the core thread can be referred to as the first covering thread. In this case, the first and second covering threads may be made of the same material or of different materials.

[0043] In one embodiment, the thickness of the first covering yarn and the second covering yarn may be 50 to 300 denier, respectively.

[0044] In one embodiment, the twist count of the first covering yarn may be 200 to 800 TPM based on 50 to 300 denier, and the twist count of the second covering yarn may be 300 to 1,000 TPM based on 50 to 300 denier. Specifically, the standard twist count of the first and second covering yarns may be 150 denier.

[0045] In one embodiment, the first covering yarn may have a twist in the S direction or the Z direction, and the second covering yarn may also have a twist in the S direction or the Z direction. In this case, the first covering yarn and the second covering yarn may have different twist directions. By having the first covering yarn and the second covering yarn twist in different directions, the occurrence of snaling (a phenomenon in which curling occurs due to twisting) can be prevented by the dispersion of torque caused by the twisting.

[0046] In this invention, the weight ratio of the core thread to the covering thread may be 90:10 to 30:70, or 70:30 to 50:50, or 60:40 to 50:50.

[0047] Furthermore, the weight ratio of the first covering yarn to the second covering yarn may be 50:50 to 30:70. If the weight ratio deviates from this range, problems may arise such as reduced uniformity and twisting due to imbalances caused by denier deviations between the raw yarns.

[0048] In this invention, the thickness of the composite yarn may be 150 to 700 denier.

[0049] Furthermore, in this invention, the strength of the composite yarn may be 1 to 30 g / d or 1 to 10 g / d. Within this strength range, the composite yarn does not experience breakage, and stable weaving properties can be provided. The strength can be measured by the method of examining the strength of the raw yarn according to the KSK 0412:2022 test method.

[0050] In this invention, the elongation of the composite yarn may be 10-30% or 20-25%. Within this elongation range, drape can be imparted to the woven fabric. The elongation can be measured by the method of considering the elongation (%) of the raw yarn according to the KSK 0412:2022 test method.

[0051] In the present invention, the dimensional change rate of the composite yarn may be 0.5 to 10%. A stable washing shrinkage rate can be provided with the above dimensional change rate. The above dimensional change rate can be measured by the KSK ISO 6330:2012,5B test method, which involves drying a product woven with separation membrane yarn at a washing temperature of around 41°C.

[0052] Furthermore, the present invention relates to a method for manufacturing the composite yarn.

[0053] The method for producing a composite yarn according to the present invention is a step of S1) imparting twist to a core yarn, which is a slit yarn containing an ultra-high molecular weight polyethylene (UHMWPE) layer and a heat-resistant coating layer formed on one surface of the UHMWPE layer, through a drawing process. S2) A step of joining the core thread of step S1) with the first covering thread while applying a twist, and S3) The step of plying the ply yarn from step S2) while twisting the second covering yarn may be included.

[0054] In the present invention, step S1) is a step of twisting a core yarn, which is a slit yarn containing an ultra-high molecular weight polyethylene (UHMWPE) layer and a heat-resistant coating layer formed on one surface of the UHMWPE layer, through a stretching process. In this step, the flat slit yarn can form the central axis of the composite yarn in a stable shape and position.

[0055] In one embodiment, the stretching ratio during the stretching process may be 1.0 to 1.4 DR, or 1.1 to 1.2 DR.

[0056] In one embodiment, the core thread is lead-free (TPM 0) or can be stretched to have a twist count of 50 to 300 TPM per meter.

[0057] In one embodiment, a heat treatment process at 100-120°C or 100-110°C can be further performed after stretching. This heat treatment process can fix the shape of the core thread.

[0058] In the present invention, step S2) is a step in which the first covering thread is combined with the core thread of step S1) while twisting it. In this step, the covering thread can be introduced while applying an optimal TPM in one direction so as not to cause snalling (SNARL).

[0059] In one embodiment, the first covering yarn is a raw yarn of a chemical fiber or a natural fiber, and the aforementioned materials can be used.

[0060] In one embodiment, the first covering yarn can be covered with a thickness of 200-800 TPM or 250-500 TPM based on a 50-300 denier standard. Specifically, the twist count standard may be 150 denier.

[0061] In one embodiment, step S2) can be performed at 90-140°C or 100-120°C.

[0062] In the present invention, step S3) is a step in which the second covering yarn is twisted while the plied yarn of step S2) is plied. In this step, the covering yarn can be supplied while applying an optimal TPM in a certain direction in order to balance with the first twisting step.

[0063] In one embodiment, the second covering yarn is a raw yarn of a chemical fiber or a natural fiber, and the aforementioned materials can be used.

[0064] In one embodiment, the second covering yarn can be joined to the first covering yarn in the opposite direction.

[0065] In one embodiment, the second covering yarn can be covered with a TPM of 200-1,000 or 250-800 based on 50-300 denier. This step can impart a higher TPM compared to the first twisting step of the covering yarn. Specifically, the reference number of twists may be 150 denier.

[0066] In one embodiment, the number of twists in the second covering yarn may be greater than the number of twists in the first covering yarn.

[0067] In one embodiment, step S3) can be performed at 90-140°C or 100-120°C.

[0068] In the present invention, Figures 4(a) to 4(c) show a composite yarn (100) of a waste separation membrane slit yarn and a covering yarn. As shown in (a), the first covering yarn (20) can be joined to the core yarn (10), and the second covering yarn (30) can be joined after the covering with the first covering yarn.

[0069] The present invention will now be described in detail with reference to examples. The following examples are illustrative of the present invention and the scope of the present invention is not limited to these examples. These examples are provided to complete the disclosure of the present invention and to fully inform those who are ordinary skill in the art to which the present invention pertains, and the present invention is defined only by the scope of the claims.

[0070] Example Example 1. Production of Composite Fiber (1) Core Fiber Preparation We prepared SKIET ceramic-coated separation membranes (thickness: approximately 15 μm), which were excess production and discarded during the manufacturing process for secondary batteries.

[0071] The separation membrane was cut into 2mm strips using a slit cutter (Slitter FIX device) specifically designed for separation membranes to produce slit yarn, which was then used as the core yarn.

[0072] The core yarn can be manufactured in the same manner as the yarn manufacturing method described in Korean Registered Patent No. 10-2607185 (Title of Invention: Yarn Manufacturing System Using Recycling Separation Membrane for Secondary Batteries and Method Using the Same).

[0073] (2) Covering Fiber Preparation 150 denier polyester was used as the first covering yarn.

[0074] 150 denier polyester was used as the second covering yarn.

[0075] (3) Production of Composite Fiber The core yarn prepared in (1) was subjected to a stretching process to impart a twist of 100 TPM. The core yarn was stretched to 1.1-1.2 DR. Subsequently, it was heat-treated at a temperature of 100-110°C for 0.2-0.3 hours.

[0076] The first covering yarn was plied to the aforementioned core yarn while applying a twist of 300 TPM. This plied yarn was plied at a temperature of 100-120°C.

[0077] Subsequently, the second covering yarn was plied with the other yarn while applying a twist of 300 TPM. This plied yarn was plied at a temperature of 100-120°C.

[0078] Through the aforementioned steps, a composite yarn with an overall fineness of approximately 680 denier was produced.

[0079] In this case, the composition ratio of the core yarn to the covering yarn was 55:45 by weight, and the first covering yarn had an S-twist, while the second covering yarn had a Z-twist, resulting in a double covering.

[0080] Figure 1 is a photograph of the composite yarn produced by Example 1.

[0081] Comparative Example 1 Slit yarn was manufactured using a conventional slit cutter.

[0082] Experimental Example 1. Evaluation of Slit Fiber Depending on the Type of Slitter The slit yarns produced in Example 1(1) and Comparative Example 1 were evaluated.

[0083] Figure 2 shows photographs of the conventional slit cutter (a) used in Comparative Example 1 and the slit cutter for separation membranes used in Example 1.

[0084] Figure 3 shows a photograph of the slit yarn, i.e., the core yarn, manufactured in Example 1.

[0085] As shown in Figure 2a, when using a conventional slit cutter, it can be confirmed that the separation membrane is damaged by the slit tension and the slit spacing is uneven due to slippage.

[0086] In contrast, it can be confirmed that the separation membrane according to Example 1 can be slit at regular intervals without error (Figures 2b and 3).

[0087] The slit cutter used in the embodiment does not employ a conventional passive type in which the separation membrane passes through a fixed cutter, but rather a system in which the separation membrane is slit by an actively rotating module of a blade with a fine cutter, thus enabling error-free slitting at regular intervals.

[0088] Experimental Example 2. Measurement of Strength The strength was measured using the method for examining the strength of the raw yarn according to the KSK 0412:2022 test method.

[0089] The strength of the composite yarn produced in Example 1 is 1.58 (g / d).

[0090] Within the aforementioned strength range, the composite yarn does not exhibit the phenomenon of yarn breakage, and has the effect of providing stable weaving properties.

[0091] Experimental Example 3. Measurement of Elongation Elongation was measured using the method for determining the elongation (%) of the raw yarn according to the KSK 0412:2022 test method.

[0092] The elongation of the composite yarn produced in Example 1 is 22.5%.

[0093] By imparting appropriate elongation to the woven fabric within the aforementioned elongation range, it has the effect of providing drape.

[0094] Experimental Example 4. Measurement of Dimensional Change Rate The dimensional change rate was measured using the KSK ISO 6330:2012,5B test method, by washing the resulting product with separated membrane yarn before and after washing at a temperature of 41°C and then hanging it to dry.

[0095] The dimensional change rate of the composite yarn produced in Example 1 is 0.5.

[0096] This has the effect of providing a stable washing shrinkage rate within the aforementioned range of dimensional change rates. [Explanation of Symbols]

[0097] 100: Composite yarn 10: Core yarn 20: First covering thread 30: Second covering thread

Claims

1. One or more covering threads cover the core thread, The core yarn is a slit yarn comprising an ultra-high molecular weight polyethylene (UHMWPE) layer and a heat-resistant coating layer formed on one surface of the UHMWPE layer. The aforementioned core thread is a composite thread with a width of 0.5 to 3 mm.

2. The composite yarn according to claim 1, characterized in that the heat-resistant coating layer comprises inorganic particles selected from the group consisting of ceramic, aluminum hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, alumina, boehmite, aluminum hydroxide, titanium dioxide, silica, zinc oxide, and clay, and a heat-resistant polymer resin selected from the group consisting of polyacrylonitrile, polysulfone, polyamide, polytetrafluoroethylene, polyurethane, polyaramid, and cellulose acetate, or two or more combinations thereof.

3. The composite yarn according to claim 1, characterized in that the content of the heat-resistant coating layer in the core yarn is 20 to 50 parts by weight per 100 parts by weight of the UHMWPE layer.

4. The composite yarn according to claim 1, characterized in that the core thread is made from waste separation film discarded during the manufacturing process of secondary batteries, cut into widths of 0.5 to 3 mm.

5. The composite yarn according to claim 1, characterized in that the thickness of the core thread is 5 to 30 μm.

6. The core thread is 100-400 denier. The composite yarn according to claim 1, characterized in that it is lead-free or has 50 to 300 TPM per meter.

7. Covering yarn is a raw material made from synthetic or natural fibers. The aforementioned chemical fiber is one or more composite materials selected from the group consisting of polyester, nylon, acrylic, rayon, and polyethylene including UHMWPE. The composite yarn according to claim 1, characterized in that the natural fiber is one or more composite materials selected from the group consisting of cotton, wool, and silk.

8. The composite yarn according to claim 1, characterized in that the covering yarn has a denier of 50 to 300.

9. The core thread is covered with two covering threads. The twist count of the first covering yarn is 200 to 800 TPM based on 50 to 300 denier. The composite yarn according to claim 1, characterized in that the twist count of the second covering yarn is 200 to 1,000 TPM based on 50 to 300 denier.

10. The first covering thread has a twist in the S direction or the Z direction. The second covering thread has a twist in the S direction or the Z direction. The composite yarn according to claim 1, characterized in that the first covering yarn and the second covering yarn have different twist directions.

11. The thickness of the composite yarn is 150 to 700 denier. The strength is 1 to 30 g / d. The growth rate is 10-30%. The composite yarn according to claim 1, characterized in that the dimensional change rate is 0.5 to 10%.

12. S1) A step of twisting a core yarn, which is a slit yarn containing an ultra-high molecular weight polyethylene (UHMWPE) layer and a heat-resistant coating layer formed on one surface of the UHMWPE layer, through a drawing process. S2) A step of joining the core thread of step S1) with the first covering thread while applying a twist, and S3) The process includes a step of plying the ply yarn from step S2) with the second covering yarn while applying a twist to it, A method for manufacturing a composite yarn in which the second covering yarn is joined to the first covering yarn in the opposite direction.

13. In step S1), the draw ratio is 1.0 to 1.4 DR, and the slit yarn is lead-free or drawn to have a twist of 50 to 300 TPM per meter. A method for producing a composite yarn according to claim 12, characterized in that after stretching, a heat treatment step of 90 to 120°C is further performed.

14. The method for producing a composite yarn according to claim 12, characterized in that in step S2), the first covering yarn is covered at 200 to 800 TPM on a basis of 50 to 300 denier, and the step is carried out at 90 to 140°C.

15. The method for manufacturing a composite yarn according to claim 12, characterized in that in step S3), the second covering yarn is covered at 200 to 1,000 TPM on a basis of 50 to 300 denier, and the step is carried out at 90 to 140°C.

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