Method for testing the viscosity of polyacrylonitrile spinning dope

Abstract

The present application belongs to the technical field of detection methods, and particularly relates to a polyacrylonitrile spinning dope viscosity testing method. The polyacrylonitrile spinning dope viscosity testing method comprises the following steps: container pretreatment: drying and cooling the preparation container to room temperature; spinning solution preparation: respectively taking polyacrylonitrile dry powder and solvent and adding them into the container; dissolving: dissolving under the dissolving condition to obtain the dope; dope pretreatment: removing the'skin' on the surface layer of the dope; viscosity testing preparation: selecting a rotor, inserting the rotor into the dope, and connecting the hook with the testing instrument; pretreatment before testing: after the rotor is embedded in the dope, adding solvent; viscosity testing: starting the testing instrument to test the viscosity, and recording the test result. The polyacrylonitrile spinning dope viscosity testing method provided by the present application reduces the influence of human factors, prevents the'skin' phenomenon of the dope, and has good test result repeatability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of detection methods, and particularly relates to a testing method for the viscosity of polyacrylonitrile spinning dope. BACKGROUND

[0002] Fiber is a general term for a class of substances, a form of appearance of material existence, which includes natural fibers, chemically synthesized fibers (synthetic polymer fibers), and inorganic fibers and metal fibers, etc. Among them, chemically synthesized fibers have many changes in performance according to the difference in raw materials and preparation methods, and organic synthetic fibers can introduce a variety of active functional groups through chemical modification methods. Synthetic fibers are linear organic polymers obtained by polyaddition or polycondensation reaction of organic small molecules as monomers, and are prepared by solvent or melt spinning process. Synthetic fibers are polymer fiber materials. Traditional varieties are mainly divided into the following types according to the difference in skeleton material: (1) polyester fiber (polyester), (2) polyamide fiber (nylon), (3) polyvinyl alcohol fiber (vinylon), (4) polyacrylonitrile (acrylic), (5) polypropylene fiber (polypropylene), (6) polyvinyl chloride fiber (chlorofiber). Synthetic fiber materials not only meet the needs of various basic industries such as textiles, construction, plastics and other national economies, but also are widely used in many fields such as material science, life science, medicine and health, environmental technology, aerospace technology, etc. Synthetic fibers are various in type, excellent in performance, and strong in plasticity. Among them, polyacrylonitrile fibers are used as base materials to prepare special functional fibers with excellent performance and specific functions, and the reports are increasing.

[0003] In the production of dry acrylic fiber, polyacrylonitrile dry powder needs to be dissolved in a solvent in advance. After the polyacrylonitrile is fully dissolved with the solvent in the dope preparation kettle and exhaust, filtration and pressurization are performed, and then the polyacrylonitrile enters the spinning duct, and after spinning and washing, the nascent fiber is obtained. The solid content of the spinning dope has a great influence on the subsequent spinning. If the solid content of the dope is high, the flowability of the dope is affected, the filtration difficulty is large, and the spinnability of the spinning line is affected. If the solid content of the dope is low, the nascent fiber after spinning of the spinneret is difficult to form, the amount of drying gas is large, the energy consumption is high, the fiber yield is affected, and the higher the solid content of the dope, the greater the viscosity. Usually, the viscosity of the dope is tested in advance to provide guidance for the adjustment of the spinning process parameters. However, in the viscosity test process of the polyacrylonitrile dope, the position of the dope surface in contact with air is prone to "skin" phenomenon, that is, a skin film with certain strength and not easy to flow is formed. Especially, the increase of humidity in the air will accelerate the generation of "skin" phenomenon. That is, after the removal of the "skin" of the dope, water cannot be added again, and the skin film generated by the skin needs to be removed in time before testing, which causes great influence of human factors and poor stability of the test results.

[0004] CN107402167A discloses a polyacrylonitrile-based polymer solution, a method for measuring the intrinsic viscosity of the original fiber, configuring different concentrations of high molecular polymer solution, measuring the relative viscosity, measuring the relative viscosity of the polymer solution to be measured, and calculating the intrinsic viscosity of the polymer solution; a series of polymer concentration solutions are used, and for polymers with high molecular weight and long molecular chain, more dilute solutions are prepared, and for polymers with low molecular weight and short molecular chain, more concentrated solutions are prepared for measurement, thereby expanding the practical applicability of the method. The Ubbelohde viscometer method requires low sample concentration.

[0005] CN113740285A discloses a method for testing the solid content of polyacrylonitrile spinning solution, the mass fraction of polyacrylonitrile in the polyacrylonitrile spinning solution is diluted to 0.30% to 2.00% by using dimethyl sulfoxide, then the absorbance at the maximum absorption wavelength of the diluted polyacrylonitrile spinning solution is detected by using ultraviolet-visible spectrophotometry, the maximum absorption wavelength does not change with the change of the mass fraction of polyacrylonitrile, and the absorbance at the maximum absorption wavelength of the diluted polyacrylonitrile spinning solution has a good linear relationship with the mass fraction of polyacrylonitrile, and the linear correlation coefficient is greater than 0.999. This requires a dilute solution, that is, a low sample concentration, and the solid content is calculated without detecting the viscosity.

[0006] In the published paper "Polyacrylonitrile aqueous phase precipitation polymerization and its spinning solution viscosity characteristics research Wujiwei 20090420 Shandong University", the influence of molecular weight on viscosity is measured by using a rotary viscometer to measure the viscosity of the solution, and the temperature is increased by 10℃ every 20 minutes. The viscosity at different temperatures is tested by using the heating method, but the problem of skinning in actual application is not eliminated. SUMMARY

[0007] The technical problem to be solved by the present application is to overcome the above-mentioned defects existing in the prior art, and to provide a method for testing the viscosity of polyacrylonitrile spinning solution, which reduces the influence of human factors, prevents the occurrence of "skinning" of the original solution, and has good repeatability of test results.

[0008] The polyacrylonitrile spinning solution viscosity test method of the present application comprises the following steps:

[0009] (1) Container pretreatment: dry the preparation container and cool it to room temperature;

[0010] (2) Spinning solution preparation: respectively take polyacrylonitrile dry powder and solvent and add them into the container;

[0011] (3) Dissolution: dissolve according to the temperature, and obtain the original solution after dissolution;

[0012] (4) Original solution pretreatment: remove the "skin" on the surface of the original solution;

[0013] (5) Viscosity test preparation: Select a rotor, insert the rotor into the original liquid, and connect it to the test instrument with a hook;

[0014] (6) Pretreatment before testing: After the original solution has encapsulated the rotor, add solvent;

[0015] (7) Viscosity test: Start the testing instrument to perform the viscosity test and record the test results.

[0016] The drying temperature in step (1) is 100-120℃ and the drying time is 1-2h. The preferred drying temperature is 100℃ and the preferred drying time is 2h.

[0017] The mass ratio of polyacrylonitrile dry powder to solvent in step (2) is 1:2.05 to 1:3.0, preferably 1:2.3 to 1:2.4.

[0018] The solvent used in steps (2) and (6) is dimethylacetamide.

[0019] Step (5) Select a rotor model of 29# with a viscosity range of 50000-100000mPa·s and a rotation speed of 10 rpm.

[0020] The temperature of the solvent added in step (6) is 25°C to 50°C lower than the dissolution temperature in step (3), that is, the temperature is 65°C to 40°C.

[0021] In step (7), the viscosity test temperature is kept consistent with the solvent temperature.

[0022] In step (6), the mass of the solvent added is 2.0% to 10.0% of the total mass of the original solution, preferably 2.5% to 5.0%.

[0023] The dissolution temperature in step (3) is 90℃, the dissolution time is 4h, and the preferred dissolution method is water bath heating.

[0024] The testing instrument is an NDJ-1C rotational viscometer.

[0025] Specifically, the method for testing the viscosity of the polyacrylonitrile spinning solution includes the following steps:

[0026] (1) Container pretreatment: Dry the preparation container in a 100℃ oven for 2 hours and cool it to room temperature;

[0027] (2) Preparation of spinning solution: Weigh out polyacrylonitrile dry powder and solvent dimethylacetamide in a mass ratio of 1:2.3 to 1:2.4 and add them to a container;

[0028] (3) Dissolution: Heat in a water bath to 90°C and dissolve for 4 hours to obtain the stock solution;

[0029] Slowly add the polyacrylonitrile powder to the solvent and stir thoroughly until there are no obvious white particles. Seal the container and dissolve it at 90°C for 4 hours without stirring.

[0030] (4) Pretreatment of the original solution: Use tweezers to peel off and remove the "skin" on the surface of the original solution;

[0031] (5) Viscosity test preparation: Select 29# rotor, insert the rotor into the original liquid, and make sure that the rotor is inserted into the center of the original liquid, and connect it to the test instrument with a hook;

[0032] (6) Pretreatment before testing: After the original solution has encapsulated the rotor, add 2.0% to 10.0% of the solvent dimethylacetamide;

[0033] (7) Viscosity test: When the relative humidity of the air is 30-40% or 70-80%, start the test instrument and complete the test within 1 minute. Record the results of multiple experiments.

[0034] In this invention, the solvent in step (2) is the same as the solvent in step (6). After the polyacrylonitrile stock solution is prepared, it forms a colloidal state. The solvent added later will not dissolve immediately and will not affect the viscosity test of the stock solution center in a short time. After adding the solvent, the viscosity test needs to be performed immediately (2-10s). The viscosity test temperature is the same as the dissolution temperature. In addition, step (5) requires an estimate of the stock solution viscosity. Based on the viscosity range of the stock solution, a suitable rotor and rotation speed are selected. In this invention, a 29# rotor with a rotation speed of 10 rpm is used, which is suitable for a viscosity range of 50,000-100,000 mPa·s.

[0035] In the pretreatment process before testing, the addition of solvent in this invention effectively isolates the stock solution from the air, preventing the formation of a "skin" and objectively improving test stability. However, the addition of solvent will inevitably affect the properties of the stock solution. Within the allowable testing time, as long as the solvent's main influence does not affect the properties of the stock solution around the rotor, the reliability of the viscosity test results can be guaranteed. Therefore, the temperature and dosage of the added solvent are important. Higher temperatures and larger dosages of the added solvent will cause a faster decrease in the solid content of the stock solution, affecting the viscosity test results; lower temperatures will cause the stock solution temperature to drop, leading to an increase in viscosity; insufficient solvent will not provide adequate isolation.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] The method for testing the viscosity of polyacrylonitrile spinning solution of the present invention, compared with the traditional viscometer detection method, solves the problem of "skinning" affecting the test results during the test process by removing "skin". After removing "skin", adding solvent at a specific temperature makes it less likely to form skin again. It has good adaptability to the humidity of the environment and good stability and repeatability of the test results. Detailed Implementation

[0038] The present invention will be further illustrated below with specific embodiments, but the embodiments do not represent limitations on the present invention.

[0039] The viscosity of the stock solution in the examples in this specification is the rotational viscosity. The instrument used for testing was an NDJ-1C rotational viscometer manufactured by Shanghai Changji Geological Instrument Co., Ltd., using a 29# rotor, and the test was performed three times consecutively. The density of dimethylacetamide is 0.937 g / cm³. 3 .

[0040] The polyacrylonitrile dry powder is a copolymer of acrylonitrile and methyl acrylate, wherein the mass content of acrylonitrile is 93.95% and the mass content of methyl acrylate is 6.05%. The number average molecular weight of the copolymer is 32919 and the molecular weight distribution width is 2.88.

[0041] Example 1

[0042] The method for testing the viscosity of the polyacrylonitrile spinning solution includes the following steps:

[0043] (1) Container pretreatment: Dry the preparation container in a 100℃ oven for 2 hours and cool it to room temperature;

[0044] (2) Preparation of spinning solution: Weigh 61g of polyacrylonitrile dry powder and 139g of dimethylacetamide solvent and add them to the container;

[0045] (3) Dissolution: Place the glass beaker containing the spinning solution in a water bath and heat it to 90°C to obtain the original solution;

[0046] (4) Pretreatment of raw liquid: Remove the "skin" on the surface of the raw pulp liquid;

[0047] (5) Viscosity test preparation: Select 29# rotor, insert the rotor into the original liquid, and connect it to the test instrument with a hook;

[0048] (6) Pretreatment before testing: After the rotor is embedded in the original solution, add 5 mL of 60℃ dimethylacetamide solvent;

[0049] (7) Viscosity test: At a relative humidity of 30-40%, start the test instrument and record the results of three experiments.

[0050] Example 2

[0051] The method for testing the viscosity of the polyacrylonitrile spinning solution includes the following steps:

[0052] (1) Container pretreatment: Dry the preparation container in a 100℃ oven for 2 hours and cool it to room temperature;

[0053] (2) Preparation of spinning solution: Weigh 61g of polyacrylonitrile dry powder and 139g of dimethylacetamide solvent and add them to the container;

[0054] (3) Dissolution: Place the glass beaker containing the spinning solution in a water bath and heat it to 90°C to obtain the original solution;

[0055] (4) Pretreatment of raw liquid: Remove the "skin" on the surface of the raw pulp liquid;

[0056] (5) Viscosity test preparation: Select 29# rotor, insert the rotor into the original liquid, and connect it to the test instrument with a hook;

[0057] (6) Pretreatment before testing: After the rotor is embedded in the original solution, add 5 mL of 60℃ dimethylacetamide solvent;

[0058] (7) Viscosity test: At a relative humidity of 30-40%, start the test instrument and record the results of three experiments.

[0059] Example 3

[0060] The method for testing the viscosity of the polyacrylonitrile spinning solution includes the following steps:

[0061] (1) Container pretreatment: Dry the preparation container in a 100℃ oven for 2 hours and cool it to room temperature;

[0062] (2) Preparation of spinning solution: Weigh 61g of polyacrylonitrile dry powder and 139g of dimethylacetamide solvent and add them to the container;

[0063] (3) Dissolution: Place the glass beaker containing the spinning solution in a water bath and heat it to 90°C to obtain the original solution;

[0064] (4) Pretreatment of raw liquid: Remove the "skin" on the surface of the raw pulp liquid;

[0065] (5) Viscosity test preparation: Select 29# rotor, insert the rotor into the original liquid, and connect it to the test instrument with a hook;

[0066] (6) Pretreatment before testing: After the rotor is embedded in the original solution, add 5 mL of 60℃ dimethylacetamide solvent;

[0067] (7) Viscosity test: At a relative humidity of 30-40%, start the test instrument and record the results of three experiments.

[0068] Example 4

[0069] The method for testing the viscosity of the polyacrylonitrile spinning solution includes the following steps:

[0070] (1) Container pretreatment: Dry the preparation container in a 100℃ oven for 2 hours and cool it to room temperature;

[0071] (2) Preparation of spinning solution: Weigh 61g of polyacrylonitrile dry powder and 139g of dimethylacetamide solvent and add them to the container;

[0072] (3) Dissolution: Place the glass beaker containing the spinning solution in a water bath and heat it to 90°C to obtain the original solution;

[0073] (4) Pretreatment of raw liquid: Remove the "skin" on the surface of the raw pulp liquid;

[0074] (5) Viscosity test preparation: Select 29# rotor, insert the rotor into the original liquid, and connect it to the test instrument with a hook; (6) Pretreatment before test: After the original liquid has embedded the rotor, add 5 mL of 60℃ solvent dimethylacetamide; (7) Viscosity test: At an air relative humidity of 30-40%, start the test instrument and record the experimental results three times.

[0075] Example 5

[0076] The method for testing the viscosity of the polyacrylonitrile spinning solution includes the following steps:

[0077] (1) Container pretreatment: Dry the preparation container in a 100℃ oven for 2 hours and cool it to room temperature;

[0078] (2) Preparation of spinning solution: Weigh 61g of polyacrylonitrile dry powder and 139g of dimethylacetamide solvent and add them to the container;

[0079] (3) Dissolution: Place the glass beaker containing the spinning solution in a water bath and heat it to 90°C to obtain the original solution;

[0080] (4) Pretreatment of raw liquid: Remove the "skin" on the surface of the raw pulp liquid;

[0081] (5) Viscosity test preparation: Select 29# rotor, insert the rotor into the original liquid, and connect it to the test instrument with a hook; (6) Pretreatment before test: After the original liquid has embedded the rotor, add 5 mL of 60℃ solvent dimethylacetamide; (7) Viscosity test: At an air relative humidity of 30-40%, start the test instrument and record the experimental results three times.

[0082] Example 6

[0083] The method for testing the viscosity of the polyacrylonitrile spinning solution includes the following steps:

[0084] (1) Container pretreatment: Dry the preparation container in a 100℃ oven for 2 hours and cool it to room temperature;

[0085] (2) Preparation of spinning solution: Weigh 61g of polyacrylonitrile dry powder and 139g of dimethylacetamide solvent and add them to the container;

[0086] (3) Dissolution: Place the glass beaker containing the spinning solution in a water bath and heat it to 90°C to obtain the original solution;

[0087] (4) Pretreatment of raw liquid: Remove the "skin" on the surface of the raw pulp liquid;

[0088] (5) Viscosity test preparation: Select 29# rotor, insert the rotor into the original liquid, and connect it to the test instrument with a hook; (6) Pretreatment before test: After the original liquid has embedded the rotor, add 5 mL of 60℃ solvent dimethylacetamide; (7) Viscosity test: At an air relative humidity of 30-40%, start the test instrument and record the experimental results three times.

[0089] Example 7

[0090] The method for testing the viscosity of the polyacrylonitrile spinning solution includes the following steps:

[0091] (1) Container pretreatment: Dry the preparation container in a 100℃ oven for 2 hours and cool it to room temperature;

[0092] (2) Preparation of spinning solution: Weigh 61g of polyacrylonitrile dry powder and 139g of dimethylacetamide solvent and add them to the container;

[0093] (3) Dissolution: Place the glass beaker containing the spinning solution in a water bath and heat it to 90°C to obtain the original solution;

[0094] (4) Pretreatment of raw liquid: Remove the "skin" on the surface of the raw pulp liquid;

[0095] (5) Viscosity test preparation: Select 29# rotor, insert the rotor into the original liquid, and connect it to the test instrument with a hook;

[0096] (6) Pretreatment before testing: After the rotor is embedded in the original solution, add 5 mL of 60℃ dimethylacetamide solvent;

[0097] (7) Viscosity test: At a relative humidity of 30-40%, start the test instrument and record the results of three experiments.

[0098] Comparative Example 1

[0099] This comparative example is the same as Example 1, except that step (6) is removed.

[0100] Comparative Example 2

[0101] This comparative example is the same as Example 1, except that the relative humidity of the air is adjusted to 70-80%, and the operation in step (6) is removed.

[0102] Comparative Example 3

[0103] This comparative example is the same as Example 1, except that the operation of 8 mL of dimethylacetamide at 35°C in step (6) is repeated.

[0104] Comparative Example 4

[0105] This comparative example is the same as Example 1, except that the operation of 8 mL of dimethylacetamide at 65°C in step (6) is performed.

[0106] Comparative Example 5

[0107] This comparative example is the same as Example 1, except that the operation of 4 mL of dimethylacetamide at 55°C in step (6) is repeated.

[0108] Comparative Example 6

[0109] This comparative example is the same as Example 1, except that the operation of 20 mL of dimethylacetamide at 55°C in step (6) is performed.

[0110] The test results of the above embodiments and comparative examples are shown in Table 1.

[0111] Table 1 Test Results

[0112]

[0113]

[0114] Of course, the above description is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is also not limited to the above examples, and all equivalent changes and improvements made by those skilled in the art within the scope of the present invention should fall within the patent coverage of the present invention.

Claims

1. A method for testing the viscosity of polyacrylonitrile spinning solution, characterized in that: Includes the following steps: (1) Container pretreatment: Dry the preparation container and cool it to room temperature; (2) Preparation of spinning solution: Weigh out the polyacrylonitrile dry powder and solvent and add them to the container; (3) Dissolution: Dissolve according to temperature, and the original solution is obtained after dissolution; (4) Pretreatment of the original solution: Remove the "skin" on the surface of the original solution; (5) Viscosity test preparation: Select a rotor, insert the rotor into the original liquid, and connect it to the test instrument with a hook; (6) Pretreatment before testing: After the rotor is embedded in the original solution, dimethylacetamide is added as a solvent at a temperature of 40~65℃; the mass of the added solvent is 2.0%~10.0% of the total mass of the original solution; (7) Viscosity test: Start the testing instrument to perform the viscosity test and record the test results.

2. The method for testing the viscosity of polyacrylonitrile spinning solution according to claim 1, characterized in that: The drying temperature in step (1) is 100~120℃ and the drying time is 1~2h.

3. The method for testing the viscosity of polyacrylonitrile spinning solution according to claim 1, characterized in that: The mass ratio of polyacrylonitrile dry powder to solvent in step (2) is 1:2.05~1:3.

0.

4. The method for testing the viscosity of polyacrylonitrile spinning solution according to claim 1, characterized in that: The solvent used in step (2) is dimethylacetamide.

5. The method for testing the viscosity of polyacrylonitrile spinning solution according to claim 1, characterized in that: Step (5) Select a rotor model with a viscosity range of 50,000-100,000 mPa•s.

6. The method for testing the viscosity of polyacrylonitrile spinning solution according to claim 1, characterized in that: In step (7), the viscosity test temperature is kept consistent with the solvent temperature.

7. The method for testing the viscosity of polyacrylonitrile spinning solution according to claim 1, characterized in that: The testing instrument is an NDJ-1C rotational viscometer.

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