A qualitative detection method for cuproammonia fiber, lyocell fiber and modal fiber

Abstract

The present invention provides a qualitative detection method for cupra-ammonia fiber, lyocell fiber, and modal fiber. After soaking a fiber sample in an alkaline solution, the changes in the fiber sample's diameter and cross-section are observed under a microscope to determine the type of the fiber sample. Based on the principle that regenerated cellulose fibers are alkali-resistant but acid-resistant and expand in diameter in concentrated alkaline solutions, the method amplifies the differences in microscopic properties by soaking the fiber sample in the alkaline solution, revealing them in the form of size, thereby achieving the purpose of qualitative identification. The method is simple to operate, low-cost, and rapid, and has good application prospects.

Description

Technical Field

[0001] The invention belongs to the field of textile detection, and in particular relates to a qualitative detection method for cupra fiber, lyocell fiber and modal fiber. Background Art

[0002] Regenerated cellulose fiber boasts inherent advantages such as environmental friendliness and recyclability, and some of its properties surpass those of natural fibers like cotton and linen, making it popular among consumers. To date, the development of regenerated cellulose fiber can be generally divided into three stages, resulting in three generations of products. The first generation is conventional viscose fiber, introduced in the early 20th century to address cotton shortages. The second generation is high-wet modulus viscose fiber, which began industrial production in the 1950s. Products primarily include Polynosic (developed in Japan), HWM (a modified high-wet modulus viscose fiber developed in the United States), and Modal fiber produced using a new process by Lenzing in Austria in the late 1980s. The third generation is represented by the short-fiber Tencel and long-fiber Newcell products launched in the 1990s. Influenced by environmental awareness and a love for nature, people have developed a new understanding of regenerated cellulose fiber. Furthermore, with improvements in production processes, the physical and chemical properties of each generation of regenerated cellulose fiber have significantly improved, further reducing environmental pollution during production. Consequently, the application of regenerated cellulose fiber has grown rapidly.

[0003] The qualitative standards for regenerated cellulose fiber include FZ / T 01057-2007, AATCC 20-2011, ASTM D 276, and JIS L 1030-1-2005. These standards rely on confirming the fiber's identity as cellulose fiber through combustion, dissolution, and infrared spectroscopy. Microscopy is then used to determine the fiber's type based on its morphology. However, regenerated cellulose fiber is a man-made fiber, and its transverse and longitudinal morphology varies with the production process. Modal fiber is produced by improving upon the viscose fiber production process. Therefore, when the production process is not properly controlled or when different manufacturers are involved, the morphology of viscose and modal fibers can vary. For example, the commonly seen "doll-head" modal fiber and regenerated cellulose fibers with a small amount of modal morphology within viscose fibers, or modal fibers with a small amount of viscose fibers within modal fibers, often encountered in testing, create uncertainty in the final qualitative analysis. Lyocell fibers, cupro fibers, and modal fibers produced by Taiwan's Formosa Chemicals and Plastics Corporation all have circular cross-sections, and currently, no reliable qualitative differentiation method exists. Therefore, the main problems with current testing are: (1) Differences in production processes among different manufacturers lead to changes in the morphology of viscose and modal, which are between the two or include each other, making it impossible to conduct accurate qualitative analysis; (2) For regenerated cellulose fibers with circular or nearly circular cross-sections, such as lyocell fibers, cuproammonia fibers, and circular modal fibers produced by Taiwan Formosa Plastics Group, this is a difficult problem faced by many testing institutions.

[0004] Modal, Lyocell, and Cupro are all made from natural cellulose fibers. Their physical and chemical properties are very similar, with only minor differences in crystallinity, degree of polymerization, orientation, and skin-core structure. Existing qualitative methods for regenerated cellulose fibers are insufficient for practical testing, making the development of a suitable identification method particularly important. Summary of the Invention

[0005] The purpose of the present invention is to provide a qualitative detection method for cupra-ammonia fiber, lyocell fiber and modal fiber, so as to solve the problem that there is no relevant detection means in the prior art.

[0006] A qualitative detection method for cupra fiber, lyocell fiber and modal fiber is characterized in that after the fiber sample is immersed in an alkaline solution, the changes in the diameter and cross-section of the fiber sample are observed under a microscope to determine the type of the fiber sample.

[0007] The qualitative detection principle of the present invention is: since there are slight differences in crystallinity, polymerization degree, orientation degree and skin-core structure among cupra-ammonia fiber, lyocell fiber and modal fiber, and according to the principle that regenerated cellulose fiber is alkali-resistant but not acid-resistant and its diameter will expand in concentrated alkali solution, the fiber sample can be immersed in alkali solution to expand the difference in microscopic properties, so that it can be displayed in the form of size, thereby achieving the purpose of qualitative identification.

[0008] More specifically, a qualitative detection method for cuproammonia fiber, lyocell fiber and modal fiber is characterized by mainly comprising the following steps:

[0009] (1) Use a slicer to cut 0.01-1 g of fiber sample into fiber samples with a length of 0.1-1 mm;

[0010] (2) Place 1-100 mg of fiber sample on a glass slide, cover with a cover glass, and use a fiber fineness meter microscope to measure the average fiber diameter D0 (usually 5-20 μm) and record it;

[0011] (3) Drip 0.01-2 ml of alkali solution from one end where the slide and cover glass overlap, immerse the fiber sample in the alkali solution for 1-15 minutes, and then measure the average diameter D1 of the fiber (generally 30-100 μm) and record it;

[0012] (4) Calculate the expansion rate P of the fiber sample diameter according to formula (1), and determine the type of the fiber sample based on the expansion rate P and the cross-sectional morphology of the fiber sample;

[0013] The alkali solution is a sodium hydroxide solution with a concentration of 50 to 200 g / L, preferably a sodium hydroxide solution with a concentration of (70 ± 2) g / L or a sodium hydroxide solution with a concentration of (100 ± 2) g / L;

[0014] The calculation formula of the expansion rate in step (4) is:

[0015]

[0016] Preferably, the slicer is a Hastelloy slicer.

[0017] Preferably, the number of fibers tested in step (2) and step (3) is ≥200.

[0018] Preferably, the qualitative detection method of cupra fiber, lyocell fiber and modal fiber of the present invention qualitatively detects the fiber samples by detecting the change in the expansion rate of 2 to 10 groups of parallel fiber samples.

[0019] According to a large number of studies conducted by researchers of the present invention, after being soaked in a sodium hydroxide solution with an alkali content of 70 g / L, the expansion rates of cuprammonium fiber and modal fiber are ≥350%; the expansion rate of lyocell fiber is ≤250%; after being soaked in a sodium hydroxide solution with an alkali content of 100 g / L, the expansion rate of cuprammonium fiber is ≥550%; the expansion rates of modal fiber and lyocell fiber are ≤450%, and the edges of modal fiber are blurred and partially cracked in the alkali solution, while the edges of lyocell fiber are clear and the fibers are intact. In both cases, the expansion rate of modal fiber is similar to that of the other one, with no significant difference, and needs to be distinguished through two experiments: first, through the first step (after soaking in a sodium hydroxide solution with an alkali liquid of 70g / L, the expansion rate of cuprammonium fiber and modal fiber is ≥350%; the expansion rate of lyocell fiber is ≤250%) to distinguish cuprammonium fiber (modal fiber) from lyocell, and then through the second step (after soaking in a sodium hydroxide solution with an alkali liquid of 100g / L, the expansion rate of cuprammonium fiber is ≥550%; the expansion rate of modal fiber is ≤450%) to further distinguish cuprammonium fiber from modal fiber.

[0020] Regenerated cellulose fiber is a type of cellulose fiber that is alkali-resistant but not acid-resistant. In the method of the present invention, since the sodium ions in the caustic soda solution are small in size, they can enter the interior of the cellulose fiber. At the same time, Na + It is an ion with strong hydration ability, surrounding a Na + There are as many as 66 water molecules around, forming a hydration layer. + When entering the fiber and combining with the fiber, a large amount of water is also brought in. The fiber absorbs a large amount of water molecules, and the cross section changes from kidney to waist or even round, thus causing a sharp increase in the fiber diameter. + Entering the crystalline zone, the fiber's crystallinity decreases, while the amorphous zone increases. Different types of regenerated cellulose fibers have varying microstructures, including varying degrees of crystallinity, polymerization, and orientation. Consequently, different types of fibers swell to varying degrees. Therefore, the fiber's expansion rate in alkaline solution can be used as a basis for identification. This method is simple to operate, low-cost, and rapid, offering promising application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the operations of step (2) and step (3) of the present invention.

[0022] Figure 2 This is an image of the fibrils of cupra-ammonia fibers under a microscope.

[0023] Figure 3 This is an image of cuprammonium fiber after being immersed in 100g / L sodium hydroxide solution under a microscope.

[0024] Figure 4This is an image of the fibrils of Lyocell fiber under a microscope.

[0025] Figure 5 This is an image of Lyocell fiber after being immersed in 100g / L sodium hydroxide solution under a microscope.

[0026] Figure 6 This is an image of the fibrils of Modal fiber under a microscope.

[0027] Figure 7 This is an image of Modal fiber after being immersed in 100g / L sodium hydroxide solution under a microscope. DETAILED DESCRIPTION

[0028] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0029] Example 1

[0030] (1) Use a Hastelloy slicer to cut 10 mg of modal fiber, 10 mg of lyocell fiber, and 10 mg of cuprammonium fiber into fiber samples with a length of 0.4 mm respectively; (2) Place the fiber sample on a glass slide, cover it with a cover glass, and place it on the stage of a fiber fineness meter microscope, and measure the average fiber diameter D0 (9.7 μm for cuprammonium fiber, 9.6 μm for modal fiber, and 7.9 μm for lyocell fiber) and record it; (3) Use a dropper to drip 0.05 ml of a 70 g / L sodium hydroxide solution from one end of the overlapped portion of the glass slide and the cover glass, and immerse the fiber sample in the alkali solution for 3 minutes, and then measure the average fiber diameter D1 (45.0 μm for cuprammonium fiber, 43.6 μm for modal fiber, and 26.2 μm for lyocell fiber) and record it; The operation diagram of steps (2) and (3) is as follows: Figure 1 (4) The change of fiber diameter is shown in Figures 2 to 7 As shown, according to formula (1), the expansion rate P of the fiber sample diameter is calculated. The expansion rate of cuproammonia fiber is 364%, and the expansion rate of modal fiber is 354%, both of which are greater than 350%. The expansion rate of lyocell fiber is 230% < 250%. According to the expansion rate P and the cross-sectional morphology of the fiber sample, the type of the fiber sample is determined, thereby distinguishing cuproammonia fiber (modal fiber) from lyocell fiber in a simple and quick manner.

[0031] (5) Use a Hastelloy slicer to cut 10 mg of modal fiber and 10 mg of cuprammonium fiber into fiber samples with a length of 0.4 mm respectively; (6) Place the fiber sample on a glass slide, cover it with a cover glass, and place it on the stage of a fiber fineness meter microscope. Test the average diameter D0 of the fiber (10.6 μm for cuprammonium fiber and 10.3 μm for modal fiber) and record it; (7) Use a dropper to drip 0.05 ml of 100 g / L hydrogen peroxide from one end of the overlapped part of the glass slide and the cover glass. Sodium oxide solution, immerse the fiber sample in the alkali solution for 3 minutes, then measure the average fiber diameter D1 (cuprammonium fiber 74.1μm, modal fiber 55.0μm) and record it; (8) calculate the expansion rate P of the fiber sample diameter according to formula (1), the expansion rate of cuprammonium fiber = 599%>550%, the expansion rate of modal fiber = 434%<450%, and determine the type of fiber sample based on the expansion rate P, so as to easily and quickly identify and distinguish cuprammonium fiber from modal fiber.

[0032] Example 2

[0033] (1) Use a Hastelloy slicer to cut 15 mg of modal fiber, 15 mg of lyocell fiber, and 15 mg of cuprammonium fiber into fiber samples with a length of 0.7 mm respectively; (2) Place the fiber sample on a glass slide, cover it with a cover glass, and place it on the stage of a fiber fineness meter microscope, and measure the average fiber diameter D0 (10.6 μm for cuprammonium fiber, 10.4 μm for modal fiber, and 9.5 μm for lyocell fiber) and record it; (3) Use a dropper to drip 0.12 ml of a 101 g / L sodium hydroxide solution from one end of the overlapping portion of the glass slide and the cover glass, and immerse the fiber sample in the alkali solution for 5 minutes, and then measure the average fiber diameter D1 (74.6 μm for cuprammonium fiber, 55.9 μm for modal fiber, and 48.7 μm for lyocell fiber) and record it; The operation diagram of steps (2) and (3) is as follows: Figure 1 (4) The change of fiber diameter is shown in Figures 2 to 7 As shown, according to formula (1), the expansion rate P of the fiber sample diameter is calculated, the expansion rate of cuproammonia fiber = 603%> 550%, the expansion rate of modal fiber = 438%, and the expansion rate of lyocell fiber = 413%. In addition, the edge of modal fiber is fuzzy and there are some cracks in the alkali solution, while the edge of lyocell fiber is clear and the fiber is intact. According to the expansion rate P and the cross-sectional morphology of the fiber sample, the type of the fiber sample is determined, thereby quickly and easily identifying and distinguishing cuproammonia fiber, lyocell fiber and modal fiber.

[0034] Example 3

[0035] (1) Using a Hastelloy slicer, 20 mg of modal fiber, 20 mg of lyocell fiber, and 20 mg of cuprammonium fiber were cut into fiber samples with a length of 0.5 mm respectively; (2) The fiber sample was placed on a glass slide, covered with a cover glass, and placed on the stage of a fiber fineness meter microscope, and the average diameter D0 of the fiber was measured (10.0 μm for cuprammonium fiber, 9.7 μm for modal fiber, and 7.7 μm for lyocell fiber) and recorded; (3) 0.15 ml of a sodium hydroxide solution with a concentration of 71 g / L was dripped into one end of the overlapped portion of the glass slide and the cover glass using a dropper, and the fiber sample was immersed in the alkali solution for 5 minutes, and then the average diameter D1 of the fiber was measured (45.5 μm for cuprammonium fiber, 44.0 μm for modal fiber, and 26.9 μm for lyocell fiber) and recorded; the operation schematic diagram of steps (2) and (3) is shown as follows: Figure 1 As shown; (4) According to formula (1), the expansion rate P of the fiber sample diameter is calculated. The expansion rate of cuproammonia fiber = 355%, the expansion rate of modal fiber = 353%, both of which are greater than 350%, and the expansion rate of lyocell fiber = 249% < 250%; thus, cuproammonia fiber (modal fiber) and lyocell fiber can be easily and quickly identified.

[0036] Example 4

[0037] 12 mg of modal fiber, 12 mg of lyocell fiber, and 12 mg of cuprammonium fiber were cut into fiber samples of 0.5 mm in length using a Hastelloy slicer; (2) the fiber sample was placed on a glass slide, covered with a cover glass, and placed on the stage of a fiber fineness meter microscope, and the average fiber diameter D0 (modal fiber = 10.3 μm, lyocell fiber = 8.8 μm, cuprammonium fiber = 10.7 μm) was measured and recorded; (3) 0.2 ml of 99 g / L sodium hydroxide solution was dripped into one end of the overlapped portion of the glass slide and the cover glass using a dropper, and the fiber sample was immersed in the alkali solution for 4 minutes, and then the average fiber diameter D1 (modal fiber = 54.9 μm, lyocell fiber = 46.1 μm, cuprammonium fiber = 73.8 μm) was measured and recorded; the operation schematic diagram of steps (2) and (3) is shown as follows: Figure 1 (4) The change of fiber diameter is shown in Figures 2 to 7 As shown, according to formula (1), the expansion rate P of the fiber sample diameter is calculated, the expansion rate of cuproammonia fiber = 590%> 550%, the expansion rate of modal fiber = 435%, and the expansion rate of lyocell fiber = 419, all of which are less than 450%. In addition, the edge of modal fiber is fuzzy and there are some cracks in the alkali solution, while the edge of lyocell fiber is clear and the fiber is intact, so that cuproammonia fiber, lyocell fiber and modal fiber can be identified and distinguished easily and quickly.

Claims

1. A qualitative detection method for cupra-ammonia fiber, lyocell fiber and modal fiber, characterized in that: After soaking the fiber sample in alkali solution, the type of the fiber sample is determined by observing the changes in the diameter and cross-section of the fiber sample under a microscope. The method mainly includes the following steps: (1) Use a slicer to cut 0.01-1 g of fiber sample into fiber samples with a length of 0.1-1 mm; (2) Place 1-100 mg of fiber sample on a glass slide, cover with a cover glass, and use a fiber fineness meter microscope to measure the average fiber diameter D0 and record it; (3) Drip 0.01-2 ml of alkali solution from one end where the slide and cover glass overlap, immerse the fiber sample in the alkali solution for 1-15 minutes, and then measure and record the average diameter D1 of the fiber; (4) Calculate the expansion rate P of the fiber sample diameter according to the formula, and determine the type of the fiber sample based on the expansion rate P and the cross-sectional morphology of the fiber sample; Two experiments were conducted to distinguish the fibers: the first experiment used a sodium hydroxide solution with a concentration of (70±2) g / L. The expansion rates of cuproammonia fiber and modal fiber were ≥350%, while the expansion rate of lyocell fiber was ≤250%, thus distinguishing lyocell fiber. The second experiment used an alkali solution with a concentration of (100±2) g / L. The expansion rates of cuproammonia fiber were ≥550%, while the expansion rates of modal fiber and lyocell fiber were ≤450%. In addition, the edges of modal fiber were blurred and partially cracked in the alkali solution, while the edges of lyocell fiber were clear and the fibers were intact, thus distinguishing cuproammonia fiber from modal fiber. The calculation formula of the expansion rate in step (4) is: ; The slicer is a Hastelloy slicer; The number of fibers tested in step (2) and step (3) is ≥200; The fiber samples are qualitatively evaluated by detecting the changes in the expansion rates of 2 to 10 groups of parallel fiber samples.

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