A method for testing the spinnability and uniformity of spandex spinning solution

Abstract

This invention provides a method for detecting the spinnability and uniformity of spandex spinning dope. The method involves performing steady-state and dynamic tests on the spandex spinning dope to obtain its non-Newtonian index, viscosity coefficient, yield stress, maximum stress in the linear viscoelastic region, and maximum strain. Analysis of these test results yields a determination of whether the spandex spinning dope possesses excellent spinnability and uniformity. This method offers the advantages of rapid detection and accurate results. Spandex spinning dopes that pass this method exhibit minimal gelation during storage and excellent fluidity. During spinning, they show minimal yarn breakage and snagging, and a low probability of malfunctions, demonstrating excellent spinnability and uniformity.

Description

Technical Field

[0001] This invention belongs to the field of instrument testing technology, specifically relating to a method for testing the spinnability and uniformity of spandex spinning solution. Background Technology

[0002] With the continuous improvement of people's living standards, spandex, initially used as a yarn in high-end fabrics, is now widely used in various covered yarns, circular knitting machines, webbing, and warp-knitted fabrics. A variety of differentiated and multifunctional spandex products are constantly being introduced to the market, and the market's quality requirements for spandex textiles are also increasing. Market feedback indicates that both differentiated spandex for special applications and traditional warp-knitted products are placing higher demands on the surface dryness, smoothness, and uniformity of spandex-containing fabrics. With the continuous development of spandex technology, uniform spandex will no longer be a high-end, differentiated variety, but rather a fundamental property that spandex fibers should possess.

[0003] Currently, domestic and international spandex researchers have conducted extensive research on key technologies for high-uniformity spandex. The main methods include: improving the uniformity of the raw solution by using special amine chain extenders or process control to prepare high-uniformity spandex. CN105624822A discloses a dry-process spandex fiber suitable for high-uniformity spandex yarn and its preparation method, including the following steps: (1) selecting different solvents and reducing solvent impurities in the polymerization solvent stage to improve the uniformity of the spandex product; (2) selecting different raw materials and ratios in the polymerization prepolymerization stage to reduce small molecule impurities and improve the uniformity of the spandex product; (3) selecting different chain extenders and ratios in the polymerization chain extender stage to improve the molecular weight and distribution of the polymer to improve the uniformity of the spandex product; (4) selecting different spinning processes in the spinning process stage to improve the uniformity of the spandex product. Compared with conventional spandex fibers, the spandex fiber obtained by this invention has a significantly reduced coefficient of variation (CV) value of dynamic unwinding stress data, and its spandex yarn roll uniformity is significantly improved. CN112281247A discloses a method for preparing highly uniform spandex through continuous polymerization: Prepolymerization: Polytetramethylene ether glycol, diphenylmethane diisocyanate, and a polymerization inhibitor are continuously added to a tubular static mixer for mixing, reaction, and cooling to obtain a prepolymer with an NCO mass percentage of 1.0–4.0%; Polymerization: The above prepolymer and dimethylacetamide solvent are continuously added to a dynamic mixer A for uniform mixing and dispersion to obtain a prepolymer solution with a mass concentration of 30–70%; The prepolymer solution and a mixed amine solution are continuously added to a dynamic mixer B for chain extension reaction; Curing and spinning: A degelatinizing agent is added to a polyurethane urea solution, and the mixture is thoroughly stirred; After curing, the polyurethane solution is sprayed and stretched into filaments using a dry spinning system, accompanied by solvent evaporation and drying to obtain highly uniform spandex. CN101096782A discloses a method for preparing polyurethane elastic fibers via solution polymerization. The polyurethane elastic fibers comprise polyether diol, diisocyanate, n-butanol, mixed amines, additives, and the solvent dimethylacetamide. The preparation method includes two steps: polymerization and spinning. A monomolecular prepolymer solution is obtained through a prepolymerization reaction in the solvent dimethylacetamide, followed by a continuous chain extension reaction to obtain a high-molecular polymer. Various auxiliaries are then added to form a spinning solution. Finally, the solution is dry-spun through a circular channel and wound to obtain polyurethane elastic fiber filaments. This invention changes the existing bulk polymerization method by performing solution polymerization in a low-temperature solvent, improving the uniformity of the prepolymer intermediate and the polymerization solution, resulting in a uniform and pure prepolymer. The high-quality polyurethane elastic fibers produced have advantages such as good shape retention and excellent yarn uniformity, and simplify production control.

[0004] However, most of the existing technologies mentioned above are aimed at preparing special formulations or using expensive equipment, lacking universality, and the resulting spandex spinning solutions also have insufficient uniformity. At the same time, the production process of dry-spinning spandex is quite complex, and its spinnability is affected by many factors, such as gel in the solution leading to poor flowability and thus reducing spinnability. However, there is currently little research on the rheological properties of dry-spinned spandex, and the existing research only focuses on the impact of process conditions on spinnability, without in-depth research on the fundamental reasons affecting the flowability and processability of spandex solutions, thus failing to provide guidance for controlling process conditions.

[0005] Therefore, developing a detection method that can directly determine whether spandex spinning solution has excellent spinnability and uniformity, and can provide guidance for controlling the process conditions of spandex spinning solution, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for detecting the spinnability and uniformity of spandex spinning dopes. This method can directly determine whether the target spandex spinning dope has excellent spinnability and uniformity, thereby providing guidance for controlling the process conditions of spandex spinning. Furthermore, the detection method is simple and yields accurate results, providing a new approach for testing spandex spinning dopes.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for detecting the spinnability and uniformity of spandex spinning solutions, the method comprising the following steps:

[0009] (1) Steady-state test of spandex spinning solution to obtain non-Newtonian index, viscosity coefficient and yield stress of spandex spinning solution; dynamic test of spandex spinning solution to obtain maximum stress and maximum strain in the linear viscoelastic region of spandex spinning solution.

[0010] (2) Analyze the non-Newtonian index, viscosity coefficient, yield stress, maximum stress and maximum strain in the linear viscoelastic region of the spandex spinning solution obtained in step (1) to obtain the test results of the spinnability and uniformity of the spandex spinning solution.

[0011] The method for detecting the spinnability and uniformity of spandex spinning solution provided by this invention involves performing steady-state tests (steady-state tests refer to tests where the applied stress direction remains unchanged during rotation) and dynamic tests (dynamic tests refer to tests where the applied stress direction oscillates and changes during rotation) on the spandex spinning solution. This yields the non-Newtonian index, viscosity coefficient, yield stress, maximum stress in the linear viscoelastic region, and maximum strain of the spandex spinning solution. These results characterize the rheological properties of the spandex spinning solution. Furthermore, by analyzing these results, it can be directly determined whether the spandex spinning solution possesses excellent spinnability and uniformity.

[0012] The detection method provided by this invention is based on the current continuous polymerization production conditions and processes of dry-spun spandex. It innovatively combines steady-state testing and dynamic testing and applies it to dry-spun spandex production. By analyzing the flow equation and processable range of the spandex spinning solution, and using various characteristic indicators of the fluid as a basis, the polymerization process of spandex production is controlled. The entire testing and control process is rapid and accurate, and can provide guidance for controlling the process conditions of spandex spinning solution. This ensures that spandex spinning solution that passes the test by the aforementioned detection method does not produce gel during storage and has excellent fluidity. During spinning, it has less yarn doubling and yarn hanging, and no regular dark stripes on the circular knitting machine surface, resulting in a low probability of failure.

[0013] The spandex spinning solution in step (1) of the detection method provided by the present invention is applicable to all spandex spinning solutions provided in the prior art.

[0014] Preferably, the raw materials for preparing the spandex spinning solution in step (1) of the detection method provided by the present invention include a combination of isocyanate, polymer polyol and polyamine.

[0015] Specifically, the spandex spinning solution can be prepared by the following method, which includes the following steps:

[0016] (A1) Prepolymerization reaction: Polyether diol and diisocyanate are continuously added to a static mixer to react and obtain NCO-terminated polyurethane prepolymer;

[0017] (A2) Chain extension reaction: The NCO-terminated polyurethane prepolymer obtained in step (A1) is continuously added to a solvent and mixed to obtain a prepolymer solution with a concentration of 30-70%; the prepolymer solution and the mixed amine solution are continuously added to a dynamic mixer to react and obtain polyurethane urea stock solution;

[0018] (A3) Curing: The polyurethane urea stock solution obtained in step (A2) is cured to obtain the spandex spinning stock solution.

[0019] Wherein, the diisocyanate in step (A1) includes one or more combinations of diphenylmethane diisocyanate, hexamethylene diisocyanate, cyclohexanedimethylene diisocyanate or dicyclohexylmethane diisocyanate.

[0020] Preferably, the polyether glycol in step (A1) includes one or more combinations of polytetramethylene ether glycol, polyethylene glycol, polypropylene glycol, or poly2-methyltetrahydrofuran.

[0021] Preferably, the polyether diol in step (A1) has a molecular weight of 1500 to 4000, such as 2000, 2300, 2600, 2900, 3200, 3500 or 3800.

[0022] Preferably, the molar ratio of the diisocyanate to the polyether diol is (1.56 to 2):1, for example, 1.6:1, 1.65:1, 1.7:1, 1.75:1, 1.8:1, 1.85:1, 1.9:1 or 1.95:1, etc.

[0023] Preferably, the reaction time in step (A1) is 1.5 to 4 hours, for example, 2 hours, 2.5 hours, 3 hours or 3.5 hours.

[0024] Preferably, the reaction temperature in step (A1) is 70 to 90°C, such as 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, or 88°C.

[0025] Preferably, the solvent in step (A2) is N,N-dimethylacetamide (MDAC). More preferably, the N,N-dimethylacetamide is a solvent purified by distillation and ion exchange resin, with a water content ≤50ppm, conductivity ≤0.05μS, pH value of 6.3~7.3, and purity ≥99.95%.

[0026] Preferably, the molar ratio of the terminal amine in the mixed amine solution to the NCO groups in the prepolymer solution in step (A2) is (1.02 to 1.08):1, for example, 1.03:1, 1.04:1, 1.05:1, 1.06:1 or 1.07:1, etc.

[0027] Preferably, the mixed amine solution in step (A2) includes any one or a combination of at least two of chain extenders, terminators, or crosslinking agents.

[0028] Preferably, the chain extender comprises any one or a combination of at least two of 1,2-propanediamine, 2-methyl-1,5-pentanediamine, or ethylenediamine.

[0029] Preferably, the terminating agent comprises diethylamine.

[0030] Preferably, the crosslinking agent comprises diethyltriamine.

[0031] Preferably, commonly used functional additives may be selectively added to the polyurethane urea stock solution, including but not limited to any one or a combination of at least two of antioxidants, ultraviolet absorbers, lubricants, dyeing auxiliaries or stabilizers.

[0032] Preferably, the functional auxiliary agent comprises: 0.1-15% oxidant, 0.1-0.5% ultraviolet absorber, 0.1-1.0% lubricant, 0.1-1.0% dyeing auxiliary agent, and 0.01-0.1% stabilizer.

[0033] Preferably, the spandex spinning solution is a spandex dry spinning solution.

[0034] Preferably, the steady-state test in step (1) is performed using a rotational rheometer.

[0035] Preferably, the temperature for the steady-state test in step (1) is 30 to 60°C, such as 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C.

[0036] Preferably, the steady-state test in step (1) includes a combination of steady-state test under linear variable shear conditions and steady-state test under constant shear conditions.

[0037] Preferably, the linear variable shear rate increases from 0 to 100 s. -1 The linear range of change.

[0038] Preferably, the non-Newtonian index and viscosity coefficient of the spandex spinning solution are obtained by steady-state testing under the linear variable shear conditions.

[0039] Preferably, the shear rate under the constant shear condition is greater than 0 s. -1 and no more than 1 second -1 .

[0040] Preferably, the yield stress of the spandex spinning solution is obtained by steady-state testing under constant shear conditions.

[0041] Preferably, the dynamic test in step (1) is performed using a rotational rheometer.

[0042] Preferably, the temperature of the dynamic test in step (1) is 30 to 60°C, such as 35°C, 40°C, 45°C, 50°C, 55°C or 60°C.

[0043] Preferably, the dynamic test in step (1) is performed at a constant shear frequency.

[0044] Preferably, the constant shear frequency is greater than 0 rad / s and not greater than 20 rad / s.

[0045] Preferably, the raw materials for preparing the spandex spinning solution in step (1) include a combination of isocyanate, polymer polyol and polyamine.

[0046] Preferably, the non-Newtonian index of the spandex spinning solution is 0.86 to 0.96, the viscosity coefficient is 350 to 550, the yield stress is 400 to 700 Pa, the maximum stress in the linear viscoelastic region is ≥1200 Pa and the maximum strain in the linear viscoelastic region is ≥20%, and the test result in step (2) is qualified; if any one of them is not within the above range, the test result is unqualified.

[0047] It should be noted that if the above test results are qualified, the next spinning step can be carried out directly; if the test results are unqualified, the ratio of polyether glycol to diisocyanate in the raw materials for preparing the spandex spinning solution, the ratio of terminal amine in the mixed amine solution to NCO groups in the prepolymer solution, the concentration of polyurethane urea solution, the reaction temperature and time can be adjusted until the test results of the spandex spinning solution are qualified.

[0048] As a preferred technical solution, the detection method includes the following steps:

[0049] (1) At 30–60°C, a rotational rheometer was used to test the shear rate of the spandex dry spinning solution as it increased from 0 to 100 s. -1 Steady-state tests were conducted under linear variable shear conditions to obtain the non-Newtonian index and viscosity coefficient of the spandex spinning solution. At 30–60°C, a rotational rheometer was used to test the spandex dry spinning solution at shear rates greater than 0 s⁻¹. -1 and no more than 1 second -1 Steady-state tests were conducted under constant shear conditions within the range to obtain the yield stress of the spandex spinning solution; dynamic tests were conducted on the spandex dry spinning solution under constant shear conditions within the range of shear frequency greater than 0 rad / s and not greater than 20 rad / s using a rotational rheometer at 30–60°C to obtain the maximum stress and maximum strain in the linear viscoelastic region of the spandex spinning solution.

[0050] (2) The non-Newtonian index of the spandex spinning solution in step (1) is 0.86 to 0.96, the viscosity coefficient is 350 to 550, the yield stress is 400 to 700 Pa, the maximum stress in the linear viscoelastic region is ≥1200 Pa and the maximum strain in the linear viscoelastic region is ≥20%, and the test results of the spinnability and uniformity of the spandex spinning solution are qualified.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] This invention provides a method for detecting the spinnability and uniformity of spandex spinning dope. The method involves performing steady-state and dynamic tests on the spandex spinning dope to obtain its non-Newtonian index, viscosity coefficient, yield stress, maximum stress in the linear viscoelastic region, and maximum strain. Analysis of these test results allows direct determination of whether the spandex spinning dope possesses excellent spinnability and uniformity. This detection method offers the advantages of rapid detection and accurate results. Spandex spinning dopes that pass this method exhibit minimal gel formation during storage and excellent fluidity. During spinning, they show less yarn bundling and snagging, and fewer malfunctions, thus demonstrating excellent spinnability and uniformity. Attached Figure Description

[0053] Figure 1 Steady-state rheological test curves of the spandex spinning solution provided in Example 1 under linear variable shear rate conditions;

[0054] Figure 2 Steady-state rheological test curves of the spandex spinning solution provided in Example 1 under constant shear rate conditions;

[0055] Figure 3 Dynamic rheological tests were conducted on the spandex spinning solution provided in Example 1 under constant shear frequency conditions, where 1-G' is the pre-degradation plateau line, 2-marking line, and 3-test line. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0057] Preparation Example 1

[0058] A spandex spinning solution, the preparation method of which includes the following steps:

[0059] (1) Prepolymerization reaction: 4,4'-diphenylmethane diisocyanate and polytetramethylene ether glycol were added to a static mixer at a flow rate of 110 g / min and mixed to carry out the reaction, resulting in NCO-terminated polyurethane prepolymer.

[0060] (2) Chain extension reaction: The NCO-terminated polyurethane prepolymer obtained in step (1) was added to a dissolving machine at a flow rate of 689 g / min and dimethylacetamide at a flow rate of 1060 g / min for mixing and dispersion to obtain a prepolymer solution; the prepolymer solution was added to a dynamic mixer at a flow rate of 1749 g / min and a mixed amine solution at a flow rate of 212 g / min for chain extension reaction, and the molar ratio of ethylenediamine, 1,2-propanediamine and diethylamine in the mixed amine solution was 100:0:1.5; the amount of excess amine added was controlled to obtain a polyurethane urea stock solution with an apparent viscosity of 1200 poise at 40℃;

[0061] (3) Curing: The polyurethane urea stock solution obtained in step (2) is cured in a curing tank at 30-50°C for 24 hours to obtain the spandex spinning stock solution.

[0062] Preparation Example 2

[0063] A spandex spinning solution, the preparation method of which includes the following steps:

[0064] (1) Prepolymerization reaction: 4,4'-diphenylmethane diisocyanate and polytetramethylene ether glycol are added to a static mixer at a flow rate of 90 g / min and reacted to obtain NCO-terminated polyurethane prepolymer.

[0065] (2) Chain extension reaction: The prepolymer obtained in step (1) was added to a dissolving machine at a flow rate of 464 g / min and dimethylacetamide at a flow rate of 714 g / min for mixing and dispersion to obtain a prepolymer solution; the prepolymer solution was added to a dynamic mixer at a flow rate of 1178 g / min and a mixed amine solution at a flow rate of 160 g / min for chain extension reaction. The molar ratio of ethylenediamine, 1,2-propanediamine and diethylamine in the mixed amine solution was 19:1:0.57; the amount of excess amine added was controlled to obtain a polyurethane urea stock solution with an apparent viscosity of 1600 poise at 40℃;

[0066] (3) Curing: The polyurethane urea stock solution obtained in step (2) is cured in a curing tank at 30-50°C for 30 hours to obtain the spandex spinning stock solution.

[0067] Preparation Example 3

[0068] A spandex spinning solution, the preparation method of which includes the following steps:

[0069] (1) Prepolymerization reaction: 4,4'-diphenylmethane diisocyanate and polytetramethylene ether glycol are added to a static mixer at a flow rate of 90 g / min and mixed and reacted to obtain NCO-terminated polyurethane prepolymer.

[0070] (2) Chain extension reaction: The prepolymer obtained in step (1) was added to a dissolving machine at a flow rate of 571 g / min and dimethylacetamide at a flow rate of 878 g / min for mixing and dispersion to obtain a prepolymer solution; the prepolymer solution was added to a dynamic mixer at a flow rate of 1449 g / min and a mixed amine solution at a flow rate of 186 g / min for chain extension reaction. The molar ratio of ethylenediamine, 2-methyl-1,5-pentanediamine and diethylamine in the mixed amine solution was 19:1:0.3; the amount of excess amine added was controlled to obtain a polyurethane urea stock solution with an apparent viscosity of 1300 poise at 40℃;

[0071] (3) Curing: The polyurethane urea stock solution obtained in step (2) is cured in a curing tank at 30-50°C for 38 hours to obtain the spandex spinning stock solution.

[0072] Preparation Example 4

[0073] A spandex spinning solution, the preparation method of which includes the following steps:

[0074] (1) Prepolymerization reaction: 4,4'-diphenylmethane diisocyanate and polytetramethylene ether glycol are added to a static mixer at a flow rate of 110 g / min and reacted to obtain NCO-terminated polyurethane prepolymer.

[0075] (2) Chain extension reaction: The prepolymer obtained in step (1) was added to a dissolving machine at a flow rate of 689 g / min and dimethylacetamide at a flow rate of 1060 g / min for mixing and dispersion to obtain a prepolymer solution; the prepolymer solution was added to a dynamic mixer at a flow rate of 1749 g / min and a mixed amine solution at a flow rate of 212 g / min for chain extension reaction. The molar ratio of ethylenediamine, 1,2-propanediamine and diethylamine in the mixed amine solution was 19:1:0.77; the amount of excess amine added was controlled to obtain a polyurethane urea stock solution with an apparent viscosity of 1500 poise at 40℃;

[0076] (3) Curing: The polyurethane urea stock solution obtained in step (2) is cured in a curing tank at 30-50°C for 35 hours to obtain the spandex spinning stock solution.

[0077] Preparation Example 5

[0078] A spandex spinning solution, the preparation method of which includes the following steps:

[0079] (1) Prepolymerization reaction: 4,4'-diphenylmethane diisocyanate and polytetramethylene ether glycol are added to a static mixer at a flow rate of 90 g / min and reacted to obtain NCO-terminated polyurethane prepolymer.

[0080] (2) Chain extension reaction: The prepolymer obtained in step (1) was added to a dissolving machine at a flow rate of 464 g / min and dimethylacetamide at a flow rate of 714 g / min for mixing and dispersion to obtain a prepolymer solution; the prepolymer solution was added to a dynamic mixer at a flow rate of 1178 g / min and a mixed amine solution at a flow rate of 160 g / min for chain extension reaction, and the molar ratio of ethylenediamine, 1,2-propanediamine and diethylamine in the mixed amine solution was 100:0:1.5; the amount of excess amine added was controlled to obtain a polyurethane urea stock solution with an apparent viscosity of 1500 poise at 40℃;

[0081] (3) Curing: The polyurethane urea stock solution obtained in step (2) is cured in a curing tank at 30-50°C for 26 hours to obtain the spandex spinning stock solution.

[0082] Preparation Example 6

[0083] A spandex spinning solution, the preparation method of which includes the following steps:

[0084] (1) Prepolymerization reaction: 4,4'-diphenylmethane diisocyanate and polytetramethylene ether glycol are added to a static mixer at a flow rate of 90 g / min and mixed and reacted to obtain NCO-terminated polyurethane prepolymer.

[0085] (2) Chain extension reaction: The prepolymer obtained in step (1) was added to a dissolving machine at a flow rate of 571 g / min and dimethylacetamide at a flow rate of 878 g / min for mixing and dispersion to obtain a prepolymer solution; the prepolymer solution was added to a dynamic mixer at a flow rate of 1449 g / min and a mixed amine solution at a flow rate of 186 g / min for chain extension reaction. The molar ratio of ethylenediamine, 2-methyl-1,5-pentanediamine and diethylamine in the mixed amine solution was 19:1:1.5; the amount of excess amine added was controlled to obtain a polyurethane urea stock solution with an apparent viscosity of 1400 poise at 40℃;

[0086] (3) Curing: The polyurethane urea stock solution obtained in step (2) is cured in a curing tank at 30-50°C for 32 hours to obtain the spandex spinning stock solution.

[0087] Preparation Example 7

[0088] A spandex spinning solution, the preparation method of which includes the following steps:

[0089] (1) Prepolymerization reaction: 4,4'-diphenylmethane diisocyanate and polytetramethylene ether glycol are added to a static mixer at a flow rate of 106 g / min and mixed and reacted to obtain NCO-terminated polyurethane prepolymer.

[0090] (2) Chain extension reaction: The prepolymer obtained in step (1) was added to a dissolving machine at a flow rate of 624 g / min and dimethylacetamide at a flow rate of 960 g / min for mixing and dispersion to obtain a prepolymer solution; the prepolymer solution was added to a dynamic mixer at a flow rate of 1584 g / min and a mixed amine solution at a flow rate of 213 g / min for chain extension reaction. The molar ratio of ethylenediamine, 2-methyl-1,5-pentanediamine and diethylamine in the mixed amine solution was 19:1:0.8; the amount of excess amine added was controlled to obtain a polyurethane urea stock solution with an apparent viscosity of 1500 poise at 40℃;

[0091] (3) Curing: The polyurethane urea stock solution obtained in step (2) is cured in a curing tank at 30-50°C for 28 hours to obtain the spandex spinning stock solution.

[0092] Example 1

[0093] A method for detecting the spinnability and uniformity of spandex spinning solutions, the method comprising the following steps:

[0094] (1) At 40°C, a rotational rheometer (manufacturer: Thermo Fisher, model: HAAKE Mars40) was used to first test the spandex spinning solution obtained in Example 1 at a shear rate increasing from 0 to 100 s. -1 Steady-state tests were conducted under linear variable shear conditions to obtain the non-Newtonian index and viscosity coefficient of the spandex spinning solution; then, a rotational rheometer was used to test the spandex spinning solution obtained in Example 1 under a shear rate of 1 s⁻¹. -1 Steady-state tests were conducted under constant shear conditions to obtain the yield stress of the spandex spinning solution. Finally, a rotational rheometer was used to conduct dynamic tests on the spandex spinning solution obtained in Example 1 under constant shear conditions with a shear frequency of 18 rad / s to obtain the maximum stress and maximum strain of the spandex spinning solution in the linear viscoelastic region.

[0095] (2) Analyze whether the non-Newtonian index of the spandex spinning solution obtained in step (1) is in the range of 0.86 to 0.96, whether the viscosity coefficient is in the range of 350 to 550, whether the yield stress is in the range of 400 to 700 Pa, whether the maximum stress in the linear viscoelastic region is not less than 1244 Pa, and whether the maximum strain is not less than 20%, and obtain the test results of the spandex spinning solution provided in Preparation Example 1.

[0096] The detection results obtained in this embodiment are as follows: Figures 1-3 As shown, the spandex spinning solution provided in Preparation Example 1 was prepared at a shear rate increasing from 0 to 100 s. -1 The steady-state test curve under linear variable shear conditions is as follows: Figure 1 As shown, by analyzing Figure 1Software simulation calculations of the test curves show that the non-Newtonian index of the spandex spinning solution provided in Example 1 is 0.899 and the viscosity coefficient is 511.

[0097] The spandex spinning solution provided in Example 1 was prepared at a shear rate of 1 s. -1 The steady-state test curve obtained under constant shear conditions is shown in the figure below. Figure 2 As shown, the maximum value during the stress rise process is the yield stress, from Figure 2 It can be seen that the yield stress of the spandex spinning solution provided in Preparation Example 1 is 476 Pa.

[0098] The dynamic test curve of the spandex spinning solution provided in Example 1 under constant shear frequency conditions is shown in the figure below. Figure 3 As shown, Figure 3 In the diagram, 1 represents the plateau line before G' decreases, 2 represents the marker line, and 3 represents the test line. The intersection of marker line 2 and test line 3 is the inflection point of the G' curve, and the abscissa of this point is the maximum strain. The plateau line 1 before G' decreases represents the maximum stress. Therefore, the maximum stress in the linear viscoelastic region of the spandex spinning solution provided in Example 1 is 1244 Pa, and the maximum strain in the linear viscoelastic region is 32%, both of which meet the requirements. Therefore, the spinnability and uniformity test results of the spandex spinning solution provided in Example 1 are qualified.

[0099] Example 2

[0100] A method for testing the spinnability and uniformity of spandex spinning solution, which differs from Example 1 only in that the spandex spinning solution obtained in Preparation Example 2 is used instead of the spandex spinning solution obtained in Preparation Example 1, while other conditions and quantities are the same as in Example 1.

[0101] The detection results obtained in Example 2 are as follows:

[0102] The non-Newtonian index of the spandex spinning solution provided in Preparation Example 2 is 0.905, the viscosity coefficient is 500, the yield stress is 677 Pa, the maximum stress in the linear viscoelastic region is 1323 Pa, and the maximum strain is 25%, all of which meet the requirements. Therefore, the test results of the spandex spinning solution provided in Preparation Example 2 are qualified.

[0103] Example 3

[0104] A method for testing the spinnability and uniformity of spandex spinning solution, which differs from Example 1 only in that the spandex spinning solution obtained in Preparation Example 3 is used instead of the spandex spinning solution obtained in Preparation Example 1, while other conditions and quantities are the same as in Example 1.

[0105] The detection results obtained in Example 3 are as follows:

[0106] The non-Newtonian index of the spandex spinning solution provided in Preparation Example 3 is 0.903, the viscosity coefficient is 402, the yield stress is 468 Pa, the maximum stress in the linear viscoelastic region is 1400 Pa, and the maximum strain is 29%, all of which meet the requirements. Therefore, the test results of the spandex spinning solution provided in Preparation Example 3 are qualified.

[0107] Example 4

[0108] A method for testing the spinnability and uniformity of spandex spinning solution, which differs from Example 1 only in that the spandex spinning solution obtained in Preparation Example 4 is used instead of the spandex spinning solution obtained in Preparation Example 1, while other conditions and quantities are the same as in Example 1.

[0109] The detection results obtained in Example 4 are as follows:

[0110] The non-Newtonian index of the spandex spinning solution provided in Preparation Example 4 was 0.832, the viscosity coefficient was 746, the yield stress was 683 Pa, the maximum stress in the linear viscoelastic region was 600 Pa, and the maximum strain was 11%. It can be seen that the non-Newtonian index, viscosity coefficient, maximum stress and maximum strain in the linear viscoelastic region of the spandex spinning solution obtained in Preparation Example 4 do not meet the requirements. Therefore, the test results of the spandex spinning solution provided in Preparation Example 4 are unqualified, and the spinnability and uniformity are poor.

[0111] Example 5

[0112] A method for testing the spinnability and uniformity of spandex spinning solution, which differs from Example 1 only in that the spandex spinning solution obtained in Preparation Example 5 is used instead of the spandex spinning solution obtained in Preparation Example 1, while other conditions and quantities are the same as in Example 1.

[0113] The detection results obtained in Example 5 are as follows:

[0114] The non-Newtonian index of the spandex spinning solution provided in Preparation Example 5 was 0.899, the viscosity coefficient was 610, the yield stress was 711 Pa, the maximum stress in the linear viscoelastic region was 1000 Pa, and the maximum strain was 15%. It can be seen that the yield stress, as well as the maximum stress and maximum strain in the linear viscoelastic region, of the spandex spinning solution obtained in Preparation Example 5 do not meet the requirements. Therefore, the test results of the spandex spinning solution provided in Preparation Example 5 are unqualified, and the spinnability and uniformity are poor.

[0115] Example 6

[0116] A method for testing the spinnability and uniformity of spandex spinning solution, which differs from Example 1 only in that the spandex spinning solution obtained in Preparation Example 6 is used instead of the spandex spinning solution obtained in Preparation Example 1, while other conditions and quantities are the same as in Example 1.

[0117] The detection results obtained in Example 6 are as follows:

[0118] The non-Newtonian index of the spandex spinning solution provided in Preparation Example 6 was 0.918, the viscosity coefficient was 532, the yield stress was 822 Pa, the maximum stress in the linear viscoelastic region was 1400 Pa, and the maximum strain was 14%. It can be seen that the yield stress and the maximum strain in the linear viscoelastic region of the spandex spinning solution obtained in Preparation Example 6 do not meet the requirements. Therefore, the test results of the spandex spinning solution provided in Preparation Example 6 are unqualified, and the spinnability and uniformity are poor.

[0119] Example 7

[0120] A method for testing the spinnability and uniformity of spandex spinning solution, which differs from Example 1 only in that the spandex spinning solution obtained in Preparation Example 7 is used instead of the spandex spinning solution obtained in Preparation Example 1, while other conditions and quantities are the same as in Example 1.

[0121] The detection results obtained in Example 7 are as follows:

[0122] The non-Newtonian index of the spandex spinning solution provided in Preparation Example 7 was 0.871, the viscosity coefficient was 547, the yield stress was 689 Pa, the maximum stress in the linear viscoelastic region was 800 Pa, and the maximum strain was 17%. It can be seen that the maximum stress and strain in the linear viscoelastic region of the spandex spinning solution obtained in Preparation Example 7 do not meet the requirements. Therefore, the test results of the spandex spinning solution provided in Preparation Example 7 are unqualified, and the spinnability and uniformity are poor.

[0123] Performance testing:

[0124] (1) Spinability test: Record the average number of non-human-caused faults per position number per day, with 15 days as a cycle. The fewer the number of faults, the better the fiber spinnability.

[0125] (2) CV variation test: Using an electronic constant tension transmission unwinding machine, under fixed input and output speed conditions, the coefficient of variation of the tension of the spandex yarn under a fixed draw ratio is detected. The lower the coefficient of variation of the unwinding stress, the better the fiber uniformity.

[0126] The spandex spinning solution obtained in the preparation example was tested according to the above test method during the spinning process. The test results are shown in Table 1.

[0127] Table 1

[0128]

[0129]

[0130] As can be seen from the data in Table 1, the spandex spinning solutions obtained in Preparation Examples 1 to 3, which were qualified by the detection method provided by the present invention, showed that the probability of failure was very small, indicating that the spandex spinning solutions provided in Preparation Examples 1 to 3 had excellent spinnability; and the variation CV test results showed that the coefficient of variation was very small, indicating that the uniformity of the spandex spinning solutions provided in Preparation Examples 1 to 3 was good.

[0131] The spandex spinning solutions provided in Preparation Examples 4 to 7, which were found to be substandard using the detection method provided by this invention, showed a significant increase in the number of defects in the spinnability test results and a large coefficient of variation in the CV test results. This indicates that the spandex spinning solutions provided in Preparation Examples 4 to 7 do not have excellent spinnability and uniformity.

[0132] In summary, it can be seen that the spandex spinning solution that is qualified by the detection method provided by the present invention has excellent spinnability and uniformity, while the spandex spinning solution that is unqualified by the detection method provided by the present invention has poor spinnability and uniformity, indicating that the detection method provided by the present invention is accurate.

[0133] The applicant declares that this invention illustrates a method for testing the spinnability and uniformity of spandex spinning solutions through the above embodiments. However, this invention is not limited to the above process steps, meaning that this invention does not necessarily rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used in this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A method for detecting the spinnability and uniformity of spandex spinning solution, characterized in that, The detection method includes the following steps: (1) At 30~60℃, the shear rate of the spandex spinning solution was increased from 0 to 100 s using a rotational rheometer. -1 Steady-state tests were conducted under linear variable shear conditions to obtain the non-Newtonian index and viscosity coefficient of the spandex spinning solution. At 30–60°C, a rotational rheometer was used to analyze the spandex spinning solution at shear rates greater than 0 s⁻¹. -1 And no more than 1 s -1 Steady-state tests were conducted under constant shear conditions within a certain range to obtain the yield stress of the spandex spinning solution. Dynamic tests were conducted on the spandex spinning solution under constant shear conditions within a shear frequency range of 30~60℃ using a rotational rheometer to obtain the maximum stress and maximum strain in the linear viscoelastic region of the spandex spinning solution. (2) The non-Newtonian index of the spandex spinning solution obtained in step (1) is 0.86~0.96, the viscosity coefficient is 350~550, the yield stress is 400~700 Pa, the maximum stress in the linear viscoelastic region is ≥1200 Pa and the maximum strain in the linear viscoelastic region is ≥20%, and the test results of the spinnability and uniformity of the spandex spinning solution are qualified.

2. The detection method according to claim 1, characterized in that, The spandex spinning solution is a dry-spinning solution for spandex.

3. The detection method according to claim 1, characterized in that, The raw materials for preparing the spandex spinning solution in step (1) include a combination of isocyanate, polymer polyol and polyamine.

Images