A method for determining the oil content of hydrophobic fibers

Abstract

The present application belongs to the technical field of fiber detection, and discloses a method for determining the oil content of hydrophobic fibers. The hydrophobic fibers are placed in water in the form of a catenary, and the dispersibility index is used to represent the dispersibility of the hydrophobic fibers in water. The dispersibility index of the hydrophobic fibers with unknown oil content is compared with the dispersibility index of the hydrophobic fibers with known oil content, and the oil content of the hydrophobic fibers with unknown oil content is determined according to the similarity. The length of the hydrophobic fibers in water is greater than or equal to 1 m. The specifications and varieties of the hydrophobic fibers with unknown oil content are the same as those of the hydrophobic fibers with known oil content. The present application can quickly, simply and at low cost determine whether the oil content is within the qualified range, so as to timely check the silk road and stabilize the product quality.

Description

Technical Field

[0001] This invention belongs to the field of fiber testing technology and relates to a method for determining the oil content of hydrophobic fibers. Background Technology

[0002] In the production of synthetic fibers (such as polyester and nylon), the application of spinning oil is an essential and crucial step. The oil plays a vital role in lubrication, antistatic properties, and fiber bundling. Precise control of the oil content (oil percentage) directly affects the efficiency of subsequent textile processing and product quality. Too low an oil content leads to a high coefficient of friction, increased fuzzing and breakage, and poor spinnability; too high an oil content easily causes problems such as needle contamination, dye spots, and yarn bundling.

[0003] Currently, the detection of oil content in fibers mainly relies on traditional laboratory methods, including Soxhlet extraction (solvent extraction), nuclear magnetic resonance (NMR), and neutral soap washing. However, these methods all have drawbacks:

[0004] Extraction method: The testing process relies on toxic organic solvents and complex experimental equipment, and the detection speed is slow.

[0005] Nuclear magnetic resonance (NMR) detection method: The equipment is expensive and the operation is complicated. It requires a special NMR instrument for measuring oil content. In addition, before the detection, 100m of hydrophobic fiber needs to be wound on a yarn length measuring instrument, weighed, and then measured, which is complicated.

[0006] Neutral soap solution washing: Strict control of soap solution concentration, temperature and washing time is required. It also involves multiple steps such as sample weighing, repeated washing, washing and drying, and secondary weighing. The whole process takes several hours, which is not only inefficient, but may also affect the accuracy of the results due to incomplete washing or fiber damage. At the same time, it consumes soap solution and other reagents, which has a certain testing cost. Moreover, it is only suitable for accurate laboratory testing and cannot meet the needs of timely feedback from the production line.

[0007] In addition, those skilled in the art have developed other methods and devices, such as the patent application with publication number CN120651298A and the patents with authorization announcement numbers CN118604099B and CN111595906B, but they all rely on complex equipment or special instruments, are cumbersome to operate and have high maintenance costs.

[0008] Therefore, chemical fiber manufacturers urgently need a method that can quickly, easily, and at low cost determine whether the oil content is within the acceptable range, so as to promptly inspect the yarn and stabilize product quality. Summary of the Invention

[0009] The purpose of this invention is to solve the problems existing in the prior art and to provide a method for determining the oil content of hydrophobic fibers.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for determining the oil content of hydrophobic fibers involves placing the hydrophobic fibers in water in the form of a catenary, using a dispersibility index to characterize the degree of dispersion of the hydrophobic fibers in water, comparing the dispersibility index of hydrophobic fibers with unknown oil content with the dispersibility index of hydrophobic fibers with known oil content, and determining the oil content of the hydrophobic fibers with unknown oil content based on the similarity. The length of the hydrophobic fibers in water is ≥1m; and the specifications and varieties of the hydrophobic fibers with unknown oil content are the same as those with known oil content.

[0012] The attraction between monofilaments in hydrophobic fibers is essentially a water-dominated indirect force known as hydrophobic interaction. Its mechanism stems from the polar nature of water molecules: when a hydrophobic fiber is immersed in water, the monofilament surface cannot form hydrogen bonds with water molecules. To minimize contact with the "unpleasant" hydrophobic surface, the water molecules surrounding the fiber are forced to rearrange into a more ordered "cage-like" structure than free water, leading to a decrease in the system's entropy (disorder) and a thermodynamically unstable state. To restore entropy, water molecules will push the hydrophobic surfaces together as much as possible. When two monofilaments in a hydrophobic fiber approach each other, the ordered water layer between them is disrupted, and the bound water molecules are released back into the disordered bulk water, thus increasing the entropy of the entire system. Therefore, this "attraction" between monofilaments in hydrophobic fibers does not originate from a direct preference between the monofilaments, but rather from the repulsion effect of water on hydrophobic materials; that is, water compresses the fiber to aggregate the monofilaments, reducing the energy cost required to maintain its ordered structure.

[0013] When hydrophobic fibers are coated with spinning auxiliaries (oils), they disperse upon contact with water, and the more oil applied, the more dispersed they become. This is because the oil fundamentally alters the physicochemical properties of the monofilament surface within the fiber. First, the oil forms a barrier on the monofilament surface, covering the originally hydrophobic polyester surface and disrupting the "hydrophobic interactions" that water molecules generate by avoiding the hydrophobic surface. This eliminates the primary thermodynamic driving force that causes monofilament aggregation. Second, the spinning oil contains amphiphilic surfactants, whose lipophilic ends adsorb onto the monofilaments, while their hydrophilic ends extend outwards. This transforms the monofilament surface from hydrophobic to hydrophilic, allowing water molecules to adhere stably and preventing them from being forced to form a low-entropy ordered structure. Simultaneously, the more oil agent used, the thicker the hydration or adsorption layer on the surface of the monofilaments, resulting in a steric hindrance repulsion effect (the core principle of steric hindrance is "physical occupancy"; a thicker oil film on the surface of the monofilaments forms a physical barrier layer between them, preventing further contact. This physical barrier effect caused by the thickness of the oil film is steric hindrance repulsion. The thicker the oil film, the greater the barrier distance, and the better the dispersion effect). Therefore, through the dual effects of hydrophilic modification and steric hindrance, the oil agent transforms the monofilaments in the fiber from "mutual attraction" to "mutual repulsion," and the greater the amount of oil, the stronger this repulsion effect, and the better the dispersibility in water.

[0014] Hydrophobic fibers are divided into non-networked hydrophobic fibers and networked hydrophobic fibers. For non-networked hydrophobic fibers, the length of the hydrophobic fiber has no effect on the degree of dispersion. For networked hydrophobic fibers, the presence of network points affects the degree of dispersion. If the length of the hydrophobic fiber in water is too short, the selected networked hydrophobic fiber will have no network. Therefore, the length of the hydrophobic fiber in water is set to ≥1m to ensure that the selected networked hydrophobic fiber has at least 2 network points, thereby standardizing and unifying the method.

[0015] As a preferred technical solution:

[0016] The method for determining the oil content of hydrophobic fibers as described above has three oil content conditions: low oil content, normal oil content, and high oil content.

[0017] The dispersibility index of hydrophobic fibers with unknown oil content is compared with that of hydrophobic fibers with known oil content. Based on the similarity, the oil content of the hydrophobic fibers with unknown oil content is determined. Specifically, this means:

[0018] Obtain the maximum and minimum values ​​of the dispersibility index of hydrophobic fibers with normal oil content, and compare them with the dispersibility index of hydrophobic fibers with unknown oil content. If the value is less than the minimum value, the oil content of the hydrophobic fiber with unknown oil content is low; if the value is greater than the maximum value, the oil content of the hydrophobic fiber with unknown oil content is high; otherwise, the oil content of the hydrophobic fiber with unknown oil content is normal.

[0019] As described above, a method for determining the oil content of hydrophobic fibers is used. The hydrophobic fibers have network points. Two adjacent network points in water are randomly selected and denoted as network point A and network point B. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fibers between network point A and network point B are denoted as points C and D, respectively. The angle between line segments AC and AD is denoted as θ, and the dispersion index is θ.

[0020] In the method for determining the oil content of hydrophobic fibers as described above, θ is obtained using a transparent comparison card;

[0021] The transparent comparison card includes a transparent plate with a pattern on it. The pattern includes a ring, four line segments, and one dashed line. One end of each line segment is at the center of the ring, and the other end is on the outer edge of the ring. The four line segments divide the ring into four regions, which are labeled as the oil-rich region (P), the normal region (P), the oil-poor region (Q), and the normal region (Q) in a clockwise or counterclockwise direction along the ring. The oil-rich region is symmetrical about the dashed line, and the oil-poor region is symmetrical about the line containing the dashed line.

[0022] Let β and α be the maximum and minimum values ​​of the dispersibility index of hydrophobic fibers with normal oil content, respectively. Let α be the fan angle corresponding to the low oil region and 360°-β be the fan angle corresponding to the high oil region.

[0023] During acquisition, place the transparent comparison card horizontally above the hydrophobic fiber, and make the projection of network point A on the transparent comparison card coincide with the center of the circle. The projection of the line connecting network point A and network point B on the transparent comparison card passes through the low-oil area and is on the same straight line as the dashed line. The angle between the projection of the line connecting point C and network point A on the transparent comparison card and the projection of the line connecting point D and network point A on the transparent comparison card is θ.

[0024] When using a transparent comparison card, a simpler method can be used to determine the oil content of hydrophobic fibers. The specific process is as follows: Place the transparent comparison card horizontally above the hydrophobic fiber, ensuring that the projection of network point A on the card coincides with the center of the circle. The projection of the line connecting network points A and B on the card passes through the low-oil zone and is on the same straight line as the dashed line. If points C and D are both located in the low-oil zone (not falling on the boundary between the low-oil zone and normal zones P and Q), then the oil content of the hydrophobic fiber with unknown oil content is low. If points C and D are both located in the high-oil zone (not falling on the boundary between the high-oil zone and normal zones P and Q), then the oil content of the hydrophobic fiber with unknown oil content is high. In other cases, the oil content of the hydrophobic fiber with unknown oil content is normal.

[0025] As described above, in a method for determining the oil content of hydrophobic fibers, the hydrophobic fibers do not have network points. The two points where the hydrophobic fibers intersect with the water surface are denoted as points E and F. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fibers between points E and F are denoted as points G and H, respectively. The angle between line segments EG and EH is denoted as γ, and the dispersion index is γ.

[0026] In the method for determining the oil content of hydrophobic fibers as described above, γ is obtained through a transparent comparison card;

[0027] The transparent comparison card includes a transparent plate with a pattern on it. The pattern includes a ring, four line segments, and one dashed line. One end of each line segment is at the center of the ring, and the other end is on the outer edge of the ring. The four line segments divide the ring into four regions, which are labeled as the oil-rich region (P), the normal region (P), the oil-poor region (Q), and the normal region (Q) in a clockwise or counterclockwise direction along the ring. The oil-rich region is symmetrical about the dashed line, and the oil-poor region is symmetrical about the line containing the dashed line.

[0028] Let β and α be the maximum and minimum values ​​of the dispersibility index of hydrophobic fibers with normal oil content, respectively. Let α be the fan angle corresponding to the low oil region and 360°-β be the fan angle corresponding to the high oil region.

[0029] When obtaining the image, place the transparent comparison card horizontally above the hydrophobic fiber, and make the projection of point E on the transparent comparison card coincide with the center of the circle. The projection of the line connecting points E and F on the transparent comparison card passes through the low-oil area and is on the same straight line as the dashed line. The angle between the projection of the line connecting points G and E on the transparent comparison card and the projection of the line connecting points H and E on the transparent comparison card is γ.

[0030] When using a transparent comparison card, a simpler method can be used to determine the oil content of hydrophobic fibers. The specific process is as follows: Place the transparent comparison card horizontally above the hydrophobic fiber, ensuring that the projection of point E on the transparent comparison card coincides with the center of the circle. The projection of the line connecting points E and F on the transparent comparison card passes through the low-oil area and is on the same straight line as the dashed line. If both points E and F are located in the low-oil area (not falling on the boundary line between the low-oil area and the normal areas P and Q), then the oil content of the hydrophobic fiber with unknown oil content is low. If both points E and F are located in the high-oil area (not falling on the boundary line between the high-oil area and the normal areas P and Q), then the oil content of the hydrophobic fiber with unknown oil content is high. In other cases, the oil content of the hydrophobic fiber with unknown oil content is normal.

[0031] As described above, in a method for determining the oil content of hydrophobic fibers, an angle scale is provided on the ring.

[0032] As described above, the method for determining the oil content of hydrophobic fibers uses deionized or distilled water to eliminate interference from water quality. The water temperature is 20±5℃. The surface tension, viscosity, and wetting speed of water are all closely related to temperature: if the temperature is too high, the surface tension of the water decreases, wetting occurs too quickly, and the hydrophobic fibers spread excessively at a large angle, leading to misjudgment; if the temperature is too low, the viscosity of the water increases, wetting slows down, and the hydrophobic fibers spread insufficiently at a small angle, also affecting the accuracy of the determination. Controlling the water temperature at 20±5℃ is a commonly used standard room temperature range for chemical fiber testing, ensuring stable and consistent surface tension and wetting properties of the water, eliminating the interference of water temperature on the spreading angle of hydrophobic fibers, and ensuring the comparability and repeatability of test results under different times and environments.

[0033] The method for determining the oil content of hydrophobic fibers as described above uses fibers with a length of 1 to 1.5 meters in water. This range facilitates horizontal placement on the water surface for quick observation, ensuring both accuracy and ease of operation. It also guarantees that, when network points exist in the fiber, at least two network points will be present on the cut hydrophobic fiber.

[0034] As described above, in one method for determining the oil content of fibers, the hydrophobic fiber is placed in water and left to sit for 4 to 15 seconds. This setting is because the hydrophobic fiber undergoes a morphological change after being placed in water, and this process takes time. Setting the time within this range ensures that the hydrophobic fiber is fully stretched and the angle is stable, while preventing excessive settling and deformation due to excessive time. This ensures that the measurement angle accurately reflects the oil content of the hydrophobic fiber.

[0035] Beneficial effects:

[0036] (1) This invention does not rely on toxic organic solvents and complex experimental equipment. It only requires water, transparent containers and simple comparison tools. The detection cost is almost negligible. Moreover, the operation does not require a professional chemical analysis background. Ordinary operators can master it after a short training. The entire judgment process only takes 30 seconds to 1 minute, achieving "second-level" on-site feedback. It completely solves the efficiency shortcomings of Soxhlet extraction method, which is cumbersome and takes several hours. At the same time, it avoids the safety risks and environmental pressure caused by solvent use. The detection process does not damage the fiber. Compared with the sample loss and troublesome subsequent processing of Soxhlet extraction method, it is more suitable for rapid quality screening in the front line of chemical fiber production.

[0037] (2) This invention can accurately cover all states of oil content, including low oil content, normal oil content, and high oil content. It is also compatible with a variety of chemical fiber materials. The detection process is non-destructive and not limited by the site. It can better meet the production quality monitoring needs. Moreover, this invention is based on clear physical and chemical principles, with significant differences in phenomena and clear and reliable results. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the transparent comparison card used in this invention;

[0039] Figure 2 This is a schematic diagram illustrating the degree of dispersion of hydrophobic fibers in water when the oil content is normal, as determined in Embodiment 1 of the present invention.

[0040] Figure 3 This is a schematic diagram illustrating the degree of dispersion of hydrophobic fibers in water when the oil content is low, as determined in Embodiment 3 of the present invention.

[0041] Figure 4 This is a schematic diagram illustrating the degree of dispersion of hydrophobic fibers in water when the oil content is high, as determined in Example 4 of the present invention. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0043] Example 1

[0044] A method for determining the oil content of hydrophobic fibers (normal oil content range is 0.4%-1.5%), comprising the following steps:

[0045] (1) Obtain the maximum value β of the dispersibility index of hydrophobic fibers with normal oil content;

[0046] (1.1) Hydrophobic fiber A (polyester, specification 73dtex / 24f, oil content 1.5%) was placed in deionized water at 20°C in the form of a catenary and waited for 4 seconds; wherein, the hydrophobic fiber has network points and the length in the water is 1m;

[0047] (1.2) Select two adjacent network points of hydrophobic fiber A in water and denot them as network point one and network point two. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point one and network point two are denoted as point three and point four, respectively. The included angle between line segment one three and line segment one four is the maximum value β of the dispersibility index of the hydrophobic fiber, where β is 90°.

[0048] (2) Obtain the minimum value α of the dispersibility index of hydrophobic fibers with normal oil content;

[0049] (2.1) Hydrophobic fiber B (with the same specifications and type as hydrophobic fiber A, and an oil content of 0.4%) is placed in deionized water at a temperature of 20°C in the form of a catenary and waited for 4 seconds; wherein, the hydrophobic fiber has network points and a length of 1m in the water;

[0050] (2.2) Select two adjacent network points of hydrophobic fiber B in water and denot them as network point a and network point b. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point a and network point b are denoted as point c and point d, respectively. The angle between line segments ac and ad is the minimum value α of the dispersion index of hydrophobic fiber, where α is 30°.

[0051] (3) Determine the oil content of hydrophobic fibers whose oil content is unknown;

[0052] (3.1) A hydrophobic fiber with unknown oil content (with the same specifications and type as hydrophobic fiber A) is placed in deionized water at 20°C in the form of a catenary and waited for 4 seconds; wherein the hydrophobic fiber has network points and a length of 1m in the water;

[0053] (3.2) Select two adjacent network points in water for the hydrophobic fiber with unknown oil content and denot them as network point A and network point B. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point A and network point B are denoted as points C and D, respectively. The angle between line segments AC and AD is denoted as θ, that is, the dispersibility index of the hydrophobic fiber with unknown oil content is θ.

[0054] Wherein, θ is obtained through a transparent comparison card; such as Figure 1As shown, the transparent comparison card includes a transparent plate with a pattern on it. The pattern includes a ring, four line segments, and one dashed line. The ring has angle markings. One end of each line segment is at the center of the ring, and the other end is on the outer edge of the ring. The four line segments divide the ring into four regions, which are labeled as the oil-rich region (P), the normal region (P), the oil-poor region (Q), and the normal region (Q) in a clockwise direction. The oil-rich region is symmetrical about the dashed line, and the oil-poor region is symmetrical about the line containing the dashed line. The fan angle corresponding to the oil-poor region is α, and the fan angle corresponding to the oil-rich region is 360° - β.

[0055] Place the transparent reference card horizontally above the hydrophobic fiber with unknown oil content, so that the projection of network point A on the transparent reference card coincides with the center of the circle. The projection of the line connecting network points A and B on the transparent reference card passes through the low-oil area and is on the same straight line as the dashed line. The angle between the projection of the line connecting point C and network point A on the transparent reference card and the projection of the line connecting point D and network point A on the transparent reference card is the dispersibility index θ of the hydrophobic fiber with unknown oil content, where θ is 40°.

[0056] The dispersibility index θ of the hydrophobic fiber with unknown oil content was compared with the maximum and minimum values ​​of the dispersibility index of the hydrophobic fiber with normal oil content (the degree of dispersion of the hydrophobic fiber with unknown oil content in water is as follows). Figure 2 As shown in the figure, the hydrophobic fiber with unknown oil content quickly disperses after being placed in water, with obvious monofilament separation, forming a uniform and fluffy fan-shaped stable morphology in the water. The dispersibility index θ is between the minimum and maximum values. Therefore, the oil content of the hydrophobic fiber with unknown oil content is judged to be normal.

[0057] To verify the accuracy of the above-mentioned determination of oil content, the following reference is made to GB / T The nuclear magnetic resonance (NMR) method in 6504-2017 "Test Method for Oil Content of Chemical Fibers" was used to test the same hydrophobic fibers with unknown oil content. The test procedure was as follows: First, two parallel samples of 2g each were weighed using an analytical balance with a graduation of 0.1mg, and the readings were accurate to 0.1mg. The corresponding pure oil was dried in an oven at 105℃ for 2 hours. A working curve was plotted evenly at five points according to the standard range of polyester drawn yarn: 0.6%, 0.7%, 0.8%, 0.9%, and 1.0%. The sealed sample tubes were placed in the instrument's detection area to complete the test. Data were read according to the working curve. The relative difference between the parallel sample tests was controlled within 10%. The final result was the arithmetic mean and three decimal places were retained. The test used a nuclear magnetic resonance spectrometer with a permanent magnet and automatic temperature control, a field strength of 0.5T, and a coil diameter of 22mm. A spin echo sequence was used, with a sampling frequency of 150KHz, a waiting time of 750ms, an echo time of 7ms, and 64 accumulations. The instrument was calibrated in advance.

[0058] The oil content of the hydrophobic fiber with unknown oil content was measured to be 0.583% using the above method. This is within the normal oil content range for this type of hydrophobic fiber. Therefore, the oil content of the hydrophobic fiber with unknown oil content is determined to be normal. Moreover, this oil content is consistent with the result of the method for determining the oil content of hydrophobic fibers described above, which verifies that the determination result of the oil content of hydrophobic fibers by the present invention is accurate and reliable.

[0059] Example 2

[0060] A method for determining the oil content of hydrophobic fibers (normal oil content range is 0.5%-2.0%), comprising the following steps:

[0061] (1) Obtain the maximum value β of the dispersibility index of hydrophobic fibers with normal oil content;

[0062] (1.1) Hydrophobic fiber A (nylon, specification 83dtex / 36f, oil content 2.0%) was placed in distilled water at 25°C in the form of a catenary and waited for 15 seconds; wherein, the hydrophobic fiber has network points and the length in the water is 1.5m;

[0063] (1.2) Select two adjacent network points of hydrophobic fiber A in water and denot them as network point one and network point two. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point one and network point two are denoted as point three and point four, respectively. The included angle between line segment one three and line segment one four is the maximum value β of the dispersibility index of the hydrophobic fiber, and β is 110°.

[0064] (2) Obtain the minimum value α of the dispersibility index of hydrophobic fibers with normal oil content;

[0065] (2.1) Hydrophobic fiber B (with the same specifications and type as hydrophobic fiber A, and an oil content of 0.5%) is placed in distilled water at 25°C in the form of a catenary and waited for 15 seconds; wherein the hydrophobic fiber has network points and a length of 1.5m in the water;

[0066] (2.2) Select two adjacent network points of hydrophobic fiber B in water and denot them as network point a and network point b. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point a and network point b are denoted as point c and point d, respectively. The angle between line segments ac and ad is the minimum value α of the dispersion index of hydrophobic fiber, where α is 25°.

[0067] (3) Determine the oil content of hydrophobic fibers whose oil content is unknown;

[0068] (3.1) A hydrophobic fiber with unknown oil content (same specifications and type as hydrophobic fiber A) is placed in distilled water at 25°C in the form of a catenary and waited for 15 seconds; wherein the hydrophobic fiber has network points and a length of 1.5m in the water;

[0069] (3.2) Select two adjacent network points in water for the hydrophobic fiber with unknown oil content and denot them as network point A and network point B. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point A and network point B are denoted as points C and D, respectively. The angle between line segments AC and AD is denoted as θ, that is, the dispersibility index of the hydrophobic fiber with unknown oil content is θ.

[0070] θ is obtained through a transparent comparison card; the transparent comparison card includes a transparent plate with a pattern on it; the pattern includes a ring, four line segments, and one dashed line; the ring has angle markings; one end of each line segment is at the center of the ring, and the other end is on the outer edge of the ring; the four line segments divide the ring into four regions, which are labeled as the oil-rich region, normal region P, oil-poor region, and normal region Q, respectively, along the clockwise direction of the ring; the oil-rich region is symmetrical about the dashed line, and the oil-poor region is symmetrical about the line containing the dashed line; the fan angle corresponding to the oil-poor region is α, and the fan angle corresponding to the oil-rich region is 360°-β;

[0071] Place the transparent reference card horizontally above the hydrophobic fiber with unknown oil content, so that the projection of network point A on the transparent reference card coincides with the center of the circle. The projection of the line connecting network points A and B on the transparent reference card passes through the low-oil area and is on the same straight line as the dashed line. The angle between the projection of the line connecting point C and network point A on the transparent reference card and the projection of the line connecting point D and network point A on the transparent reference card is the dispersibility index θ of the hydrophobic fiber with unknown oil content, where θ is 60°.

[0072] The dispersibility index θ of the hydrophobic fiber with unknown oil content is compared with the maximum and minimum values ​​of the dispersibility index of the hydrophobic fiber with normal oil content. The dispersibility index θ is between the minimum and maximum values. Therefore, the oil content of the hydrophobic fiber with unknown oil content is determined to be normal.

[0073] To verify the accuracy of the above-mentioned determination of oil content, the following reference is made to GB / T The nuclear magnetic resonance (NMR) method in 6504-2017 "Test Method for Oil Content of Chemical Fibers" was used to test the same hydrophobic fibers with unknown oil content. The test procedure was as follows: First, two 2g parallel samples were weighed using an analytical balance with a graduation of 0.1mg, and the readings were accurate to 0.1mg. The corresponding pure oil was dried in an oven at 105℃ for 2 hours. A working curve was plotted evenly at five points according to the standard range of polyester drawn yarn: 0.4%, 0.8%, 1.2%, 1.6%, and 2.0%. The sealed sample tubes were placed in the instrument's detection area to complete the test. Data were read according to the working curve. The relative difference between parallel sample tests was controlled within 10%. The final result was the arithmetic mean and retained to three decimal places. The test used a nuclear magnetic resonance spectrometer with a permanent magnet and automatic temperature control, a field strength of 0.5T, and a coil diameter of 22mm. A spin echo sequence was used, with a sampling frequency of 150KHz, a waiting time of 750ms, an echo time of 7ms, and 64 accumulations. The instrument was calibrated in advance.

[0074] The oil content of the hydrophobic fiber with unknown oil content was measured to be 1.062% using the above method. This is within the normal oil content range for this type of hydrophobic fiber. Therefore, the oil content of the hydrophobic fiber with unknown oil content is determined to be normal. Moreover, this oil content is consistent with the result of the method for determining the oil content of hydrophobic fibers described above, which verifies that the determination result of the oil content of hydrophobic fibers by the present invention is accurate and reliable.

[0075] Example 3

[0076] A method for determining the oil content of hydrophobic fibers (normal oil content range is 0.4%-1.5%), comprising the following steps:

[0077] (1) Obtain the maximum value β of the dispersibility index of hydrophobic fibers with normal oil content;

[0078] (1.1) Hydrophobic fiber A (polyester, specification 73dtex / 24f, oil content 1.5%) was placed in distilled water at 22°C in the form of a catenary and waited for 10s; wherein, the hydrophobic fiber has network points and the length in the water is 1.2m;

[0079] (1.2) Select two adjacent network points of hydrophobic fiber A in water and denot them as network point one and network point two. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point one and network point two are denoted as point three and point four, respectively. The included angle between line segment one three and line segment one four is the maximum value β of the dispersibility index of the hydrophobic fiber, where β is 90°.

[0080] (2) Obtain the minimum value α of the dispersibility index of hydrophobic fibers with normal oil content;

[0081] (2.1) Hydrophobic fiber B (with the same specifications and type as hydrophobic fiber A, and an oil content of 0.4%) is placed in distilled water at 22°C in the form of a catenary and waited for 10 seconds; wherein, the hydrophobic fiber has network points and a length of 1.2m in the water;

[0082] (2.2) Select two adjacent network points of hydrophobic fiber B in water and denot them as network point a and network point b. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point a and network point b are denoted as point c and point d, respectively. The angle between line segments ac and ad is the minimum value α of the dispersion index of hydrophobic fiber, where α is 30°.

[0083] (3) Determine the oil content of hydrophobic fibers whose oil content is unknown;

[0084] (3.1) A hydrophobic fiber with unknown oil content (with the same specifications and type as hydrophobic fiber A) is placed in distilled water at 22°C in the form of a catenary and waited for 10 seconds; wherein the hydrophobic fiber has network points and a length of 1.2m in the water;

[0085] (3.2) Select two adjacent network points in water for the hydrophobic fiber with unknown oil content and denot them as network point A and network point B. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point A and network point B are denoted as points C and D, respectively. The angle between line segments AC and AD is denoted as θ, that is, the dispersibility index of the hydrophobic fiber with unknown oil content is θ.

[0086] θ is obtained through a transparent comparison card; the transparent comparison card includes a transparent plate with a pattern on it; the pattern includes a ring, four line segments, and one dashed line; the ring has angle markings; one end of each line segment is at the center of the ring, and the other end is on the outer edge of the ring; the four line segments divide the ring into four regions, which are labeled as the oil-rich region, normal region P, oil-poor region, and normal region Q, respectively, along the clockwise direction of the ring; the oil-rich region is symmetrical about the dashed line, and the oil-poor region is symmetrical about the line containing the dashed line; the fan angle corresponding to the oil-poor region is α, and the fan angle corresponding to the oil-rich region is 360°-β;

[0087] Place the transparent reference card horizontally above the hydrophobic fiber with unknown oil content, so that the projection of network point A on the transparent reference card coincides with the center of the circle. The projection of the line connecting network points A and B on the transparent reference card passes through the low-oil area and is on the same straight line as the dashed line. The angle between the projection of the line connecting point C and network point A on the transparent reference card and the projection of the line connecting point D and network point A on the transparent reference card is the dispersibility index θ of the hydrophobic fiber with unknown oil content, where θ is 15°.

[0088] The dispersibility index θ of the hydrophobic fiber with unknown oil content was compared with the maximum and minimum values ​​of the dispersibility index of the hydrophobic fiber with normal oil content (the degree of dispersion of the hydrophobic fiber with unknown oil content in water is as follows). Figure 3 As shown in the figure, it can be seen that when the hydrophobic fiber with unknown oil content is placed in water, the angle of dispersion of the hydrophobic fiber is small (the dispersion index θ is less than the minimum value). Therefore, it is determined that the oil content of the hydrophobic fiber with unknown oil content is low.

[0089] To verify the accuracy of the above-mentioned determination of oil content, the following reference is made to GB / T The nuclear magnetic resonance (NMR) method in 6504-2017 "Test Method for Oil Content of Chemical Fibers" was used to test the same hydrophobic fibers with unknown oil content. The test procedure was as follows: First, two parallel samples of 2g each were weighed using an analytical balance with a graduation of 0.1mg, and the readings were accurate to 0.1mg. The corresponding pure oil was dried in an oven at 105℃ for 2 hours. A working curve was plotted evenly at five points according to the standard range of polyester drawn yarn: 0.6%, 0.7%, 0.8%, 0.9%, and 1.0%. The sealed sample tubes were placed in the instrument's detection area to complete the test. Data were read according to the working curve. The relative difference between the parallel sample tests was controlled within 10%. The final result was the arithmetic mean and three decimal places were retained. The test used a nuclear magnetic resonance spectrometer with a permanent magnet and automatic temperature control, a field strength of 0.5T, and a coil diameter of 22mm. A spin echo sequence was used, with a sampling frequency of 150KHz, a waiting time of 750ms, an echo time of 7ms, and 64 accumulations. The instrument was calibrated in advance.

[0090] The oil content of the hydrophobic fiber with unknown oil content was measured to be 0.133% using the above method. This is lower than the normal oil content range for this type of hydrophobic fiber. Therefore, the oil content of the hydrophobic fiber with unknown oil content is determined to be low. This oil content is consistent with the result of the method for determining the oil content of hydrophobic fibers described above, verifying that the determination result of the oil content of hydrophobic fibers by this invention is accurate and reliable.

[0091] Example 4

[0092] A method for determining the oil content of hydrophobic fibers (normal oil content range is 0.4%-1.5%), comprising the following steps:

[0093] (1) Obtain the maximum value β of the dispersibility index of hydrophobic fibers with normal oil content;

[0094] (1.1) Hydrophobic fiber A (polyester, specification 83dtex / 24f, oil content 1.5%) was placed in deionized water at 23°C in the form of a catenary and waited for 5 seconds; wherein, the hydrophobic fiber has network points and the length in the water is 1m;

[0095] (1.2) Select two adjacent network points of hydrophobic fiber A in water and denot them as network point one and network point two. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point one and network point two are denoted as point three and point four, respectively. The included angle between line segment one three and line segment one four is the maximum value β of the dispersibility index of the hydrophobic fiber, where β is 90°.

[0096] (2) Obtain the minimum value α of the dispersibility index of hydrophobic fibers with normal oil content;

[0097] (2.1) Hydrophobic fiber B (with the same specifications and type as hydrophobic fiber A, and an oil content of 0.4%) is placed in deionized water at a temperature of 23°C in the form of a catenary and waited for 5 seconds; wherein, the hydrophobic fiber has network points and a length of 1m in the water;

[0098] (2.2) Select two adjacent network points of hydrophobic fiber B in water and denot them as network point a and network point b. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point a and network point b are denoted as point c and point d, respectively. The angle between line segments ac and ad is the minimum value α of the dispersion index of hydrophobic fiber, where α is 30°.

[0099] (3) Determine the oil content of hydrophobic fibers whose oil content is unknown;

[0100] (3.1) A hydrophobic fiber with unknown oil content (same specifications and type as hydrophobic fiber A) is placed in deionized water at 23°C in the form of a catenary and waited for 5 seconds; wherein the hydrophobic fiber has network points and a length of 1m in the water;

[0101] (3.2) Select two adjacent network points in water for the hydrophobic fiber with unknown oil content and denot them as network point A and network point B. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point A and network point B are denoted as points C and D, respectively. The angle between line segments AC and AD is denoted as θ, that is, the dispersibility index of the hydrophobic fiber with unknown oil content is θ.

[0102] θ is obtained through a transparent comparison card; the transparent comparison card includes a transparent plate with a pattern on it; the pattern includes a ring, four line segments, and one dashed line; the ring has angle markings; one end of each line segment is at the center of the ring, and the other end is on the outer edge of the ring; the four line segments divide the ring into four regions, which are labeled as the oil-rich region, normal region P, oil-poor region, and normal region Q, respectively, along the clockwise direction of the ring; the oil-rich region is symmetrical about the dashed line, and the oil-poor region is symmetrical about the line containing the dashed line; the fan angle corresponding to the oil-poor region is α, and the fan angle corresponding to the oil-rich region is 360°-β;

[0103] Place the transparent reference card horizontally above the hydrophobic fiber with unknown oil content, so that the projection of network point A on the transparent reference card coincides with the center of the circle. The projection of the line connecting network points A and B on the transparent reference card passes through the low-oil area and is on the same straight line as the dashed line. The angle between the projection of the line connecting point C and network point A on the transparent reference card and the projection of the line connecting point D and network point A on the transparent reference card is the dispersibility index θ of the hydrophobic fiber with unknown oil content, where θ is 130°.

[0104] The dispersibility index θ of the hydrophobic fiber with unknown oil content was compared with the maximum and minimum values ​​of the dispersibility index of the hydrophobic fiber with normal oil content (the degree of dispersion of the hydrophobic fiber with unknown oil content in water is as follows). Figure 4 As shown in the figure, it can be seen from the figure that after the hydrophobic fiber with unknown oil content is placed in water, the hydrophobic fiber spreads at a significant angle (and after standing, the dispersion angle of the hydrophobic fiber is very large), and the dispersion index θ is greater than the maximum value. Therefore, it is determined that the hydrophobic fiber with unknown oil content has a high oil content.

[0105] To verify the accuracy of the above-mentioned determination of oil content, the following reference is made to GB / T The nuclear magnetic resonance (NMR) method in 6504-2017 "Test Method for Oil Content of Chemical Fibers" was used to test the same hydrophobic fibers with unknown oil content. The test procedure was as follows: First, two parallel samples of 2g each were weighed using an analytical balance with a graduation of 0.1mg, and the readings were accurate to 0.1mg. The corresponding pure oil was dried in an oven at 105℃ for 2 hours. A working curve was plotted evenly at five points according to the standard range of polyester drawn yarn: 0.6%, 0.7%, 0.8%, 0.9%, and 1.0%. The sealed sample tubes were placed in the instrument's detection area to complete the test. Data were read according to the working curve. The relative difference between the parallel sample tests was controlled within 10%. The final result was the arithmetic mean and three decimal places were retained. The test used a nuclear magnetic resonance spectrometer with a permanent magnet and automatic temperature control, a field strength of 0.5T, and a coil diameter of 22mm. A spin echo sequence was used, with a sampling frequency of 150KHz, a waiting time of 750ms, an echo time of 7ms, and 64 accumulations. The instrument was calibrated in advance.

[0106] The oil content of the hydrophobic fiber with unknown oil content was measured to be 2.238% using the above method. This is higher than the normal oil content range for this type of hydrophobic fiber. Therefore, the oil content of the hydrophobic fiber with unknown oil content is determined to be high. This oil content is consistent with the result of the method for determining the oil content of hydrophobic fibers described above, verifying that the determination result of the oil content of hydrophobic fibers by this invention is accurate and reliable.

[0107] Example 5

[0108] A method for determining the oil content of hydrophobic fibers (normal oil content range is 0.4~1.5%), comprising the following steps:

[0109] (1) Obtain the maximum value β of the dispersibility index of hydrophobic fibers with normal oil content;

[0110] (1.1) Hydrophobic fiber A (polyester, specification 75dtex / 24f, oil content 1.5%) was placed in deionized water at 21°C in the form of a catenary and waited for 5 seconds; wherein, the hydrophobic fiber has no network points and its length in the water is 1m;

[0111] (1.2) Select two points where the hydrophobic fiber A intersects the water surface and denote them as point E and point F respectively. The endpoints of the line segment corresponding to the maximum width of the hydrophobic fiber between point E and point F are denoteed as point G and point H respectively. The angle between line segment EG and line segment EH is the maximum value β of the dispersibility index of the hydrophobic fiber, where β is 80°.

[0112] (2) Obtain the minimum value α of the dispersibility index of hydrophobic fibers with normal oil content;

[0113] (2.1) Hydrophobic fiber B (with the same specifications and type as hydrophobic fiber A, and an oil content of 0.4%) is placed in deionized water at a temperature of 21°C in the form of a catenary and waited for 5 seconds; wherein the hydrophobic fiber has no network points and its length in the water is 1m;

[0114] (2.2) Select two points where the hydrophobic fiber B intersects the water surface and denote them as point e and point f respectively. The endpoints of the line segment corresponding to the maximum width of the hydrophobic fiber between point e and point f are denoteed as point g and point h respectively. The angle between line segment eg and line segment eh is the minimum value α of the dispersibility index of the hydrophobic fiber, and α is 25°.

[0115] (3) Determine the oil content of hydrophobic fibers whose oil content is unknown;

[0116] (3.1) A hydrophobic fiber with unknown oil content (same specifications and type as hydrophobic fiber A) is placed in deionized water at 21°C in the form of a catenary and waited for 5 seconds; wherein the hydrophobic fiber has no network points and its length in the water is 1m.

[0117] (3.2) The two points where the hydrophobic fiber with unknown oil content intersects the water surface are denoted as point E and point F, respectively. The endpoints of the line segment corresponding to the maximum width of the hydrophobic fiber between point E and point F are denoted as point G and point H, respectively. The angle between line segment EG and line segment EH is denoted as γ, that is, the dispersibility index of the hydrophobic fiber with unknown oil content is γ.

[0118] γ is obtained through a transparent comparison card; the transparent comparison card includes a transparent plate with a pattern on it; the pattern includes a ring, four line segments, and one dashed line; the ring has angle markings; one end of each line segment is at the center of the ring, and the other end is on the outer edge of the ring; the four line segments divide the ring into four regions, which are labeled as the oil-rich region, normal region P, oil-poor region, and normal region Q, respectively, along the clockwise direction of the ring; the oil-rich region is symmetrical about the dashed line, and the oil-poor region is symmetrical about the line containing the dashed line; the fan angle corresponding to the oil-poor region is α, and the fan angle corresponding to the oil-rich region is 360°-β;

[0119] Place the transparent reference card horizontally above the hydrophobic fiber with unknown oil content, so that the projection of point E on the transparent reference card coincides with the center of the circle. The projection of the line connecting points E and F on the transparent reference card passes through the low-oil area and is on the same straight line as the dashed line. The angle between the projection of the line connecting points G and E on the transparent reference card and the projection of the line connecting points H and E on the transparent reference card is the dispersibility index γ of the hydrophobic fiber with unknown oil content, where γ is 65°.

[0120] The dispersibility index γ of the hydrophobic fiber with unknown oil content was compared with the maximum and minimum values ​​of the dispersibility index of the hydrophobic fiber with normal oil content. The dispersibility index γ was between the minimum and maximum values. Therefore, the oil content of the hydrophobic fiber with unknown oil content was determined to be normal.

[0121] To verify the accuracy of the above-mentioned determination of oil content, the following reference is made to GB / T The nuclear magnetic resonance (NMR) method in 6504-2017 "Test Method for Oil Content of Chemical Fibers" was used to test the same hydrophobic fibers with unknown oil content. The test procedure was as follows: First, two parallel samples of 2g each were weighed using an analytical balance with a graduation of 0.1mg, and the readings were accurate to 0.1mg. The corresponding pure oil was dried in an oven at 105℃ for 2 hours. A working curve was plotted evenly at five points according to the standard range of polyester drawn yarn: 0.6%, 0.7%, 0.8%, 0.9%, and 1.0%. The sealed sample tubes were placed in the instrument's detection area to complete the test. Data were read according to the working curve. The relative difference between the parallel sample tests was controlled within 10%. The final result was the arithmetic mean and three decimal places were retained. The test used a nuclear magnetic resonance spectrometer with a permanent magnet and automatic temperature control, a field strength of 0.5T, and a coil diameter of 22mm. A spin echo sequence was used, with a sampling frequency of 150KHz, a waiting time of 750ms, an echo time of 7ms, and 64 accumulations. The instrument was calibrated in advance.

[0122] The oil content of the hydrophobic fiber with unknown oil content was measured to be 1.211% using the above method. This is within the normal oil content range for this type of hydrophobic fiber. Therefore, the oil content of the hydrophobic fiber with unknown oil content is determined to be normal. Moreover, this oil content is consistent with the result of the method for determining the oil content of hydrophobic fibers described above, which verifies that the determination result of the oil content of hydrophobic fibers by the present invention is accurate and reliable.

Claims

1. A method for determining the oil content of hydrophobic fibers, characterized in that, Hydrophobic fibers were placed in water in the form of catenary strands. The degree of dispersion of the hydrophobic fibers in water was characterized by a dispersibility index. The dispersibility index of hydrophobic fibers with unknown oil content was compared with that of hydrophobic fibers with known oil content. The oil content of the hydrophobic fibers with unknown oil content was determined based on the similarity. The length of the hydrophobic fibers in water was ≥1m. The specifications and varieties of the hydrophobic fibers with unknown oil content were the same as those with known oil content. There are three oil content levels: low oil content, normal oil content, and high oil content. The dispersibility index of hydrophobic fibers with unknown oil content is compared with that of hydrophobic fibers with known oil content. Based on the similarity, the oil content of the hydrophobic fibers with unknown oil content is determined. Specifically, this means: Obtain the maximum and minimum values ​​of the dispersibility index of hydrophobic fibers with normal oil content, and compare them with the dispersibility index of hydrophobic fibers with unknown oil content. If the value is less than the minimum value, the oil content of the hydrophobic fibers with unknown oil content is low. If the value is greater than the maximum value, the oil content of the hydrophobic fibers with unknown oil content is high. Otherwise, the oil content of the hydrophobic fibers with unknown oil content is normal. If the hydrophobic fiber has network points, then any two adjacent network points in the water are denoted as network point A and network point B. The endpoints of the line segments corresponding to the maximum width of the hydrophobic fiber between network point A and network point B are denoted as points C and D, respectively. Let the angle between line segments AC and AD be θ, then the dispersion index is θ. If the hydrophobic fiber does not have network points, then the two points where the hydrophobic fiber intersects the water surface are denoted as points E and F. The endpoints of the line segment corresponding to the maximum width of the hydrophobic fiber between points E and F are denoted as points G and H, respectively. Let the angle between line segments EG and EH be γ, then the dispersion index is γ.

2. The method for determining the oil content of hydrophobic fibers according to claim 1, characterized in that, θ was obtained using a transparent comparison card; The transparent comparison card includes a transparent plate with a pattern on it. The pattern includes a ring, four line segments, and one dashed line. One end of each line segment is at the center of the ring, and the other end is on the outer edge of the ring. The four line segments divide the ring into four regions, which are labeled as the oil-rich region (P), the normal region (P), the oil-poor region (Q), and the normal region (Q) in a clockwise or counterclockwise direction along the ring. The oil-rich region is symmetrical about the dashed line, and the oil-poor region is symmetrical about the line containing the dashed line. Let β and α be the maximum and minimum values ​​of the dispersibility index of hydrophobic fibers with normal oil content, respectively. Let α be the fan angle corresponding to the low oil region and 360°-β be the fan angle corresponding to the high oil region. During acquisition, place the transparent comparison card horizontally above the hydrophobic fiber, ensuring that the projection of network point A on the transparent comparison card coincides with the center of the circle. The projection of the line connecting network point A and network point B on the transparent comparison card passes through the low-oil area and is on the same straight line as the dashed line. The angle between the projection of the line connecting point C and network point A on the transparent comparison card and the projection of the line connecting point D and network point A on the transparent comparison card is θ.

3. The method for determining the oil content of hydrophobic fibers according to claim 1, characterized in that, γ was obtained through a transparent comparison card; The transparent comparison card includes a transparent plate with a pattern on it. The pattern includes a ring, four line segments, and one dashed line. One end of each line segment is at the center of the ring, and the other end is on the outer edge of the ring. The four line segments divide the ring into four regions, which are labeled as the oil-rich region (P), the normal region (P), the oil-poor region (Q), and the normal region (Q) in a clockwise or counterclockwise direction along the ring. The oil-rich region is symmetrical about the dashed line, and the oil-poor region is symmetrical about the line containing the dashed line. Let β and α be the maximum and minimum values ​​of the dispersibility index of hydrophobic fibers with normal oil content, respectively. Let α be the fan angle corresponding to the low oil region and 360°-β be the fan angle corresponding to the high oil region. During acquisition, place the transparent comparison card horizontally above the hydrophobic fiber, ensuring that the projection of point E on the transparent comparison card coincides with the center of the circle. The projection of the line connecting points E and F on the transparent comparison card passes through the low-oil area and is on the same straight line as the dashed line. The angle between the projection of the line connecting points G and E on the transparent comparison card and the projection of the line connecting points H and E on the transparent comparison card is γ.

4. A method for determining the oil content of hydrophobic fibers according to claim 2 or 3, characterized in that, The ring has angular markings.

5. The method for determining the oil content of hydrophobic fibers according to claim 1, characterized in that, The water is deionized or distilled, and the water temperature is 20±5℃.

6. The method for determining the oil content of hydrophobic fibers according to claim 1, characterized in that, The length of hydrophobic fibers in water is 1~1.5m.

7. The method for determining the oil content of hydrophobic fibers according to claim 1, characterized in that, After placing the hydrophobic fiber in water, wait 4-15 seconds.

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