A coagulation bath and methods of use and regeneration thereof

Abstract

The application belongs to the technical field of fiber preparation, and particularly relates to a coagulation bath and application method and regeneration method thereof. The application provides a coagulation bath, which comprises coagulation bath 1 or coagulation bath 2; the coagulation bath 1 comprises H2CO3 and / or X2CO3; the coagulation bath 2 comprises H2SO3 and / or Y2SO3; X and Y independently comprise at least one of Li, Na, K, Rb, Cs, Fr and NH4. The coagulation bath provided by the application has moderate coagulation speed, low reagent cost and small corrosion, and is beneficial to the formation of regular structure of fibers in the coagulation process, thereby improving the quality of fibers.

Description

Technical Field

[0001] This invention belongs to the field of fiber preparation technology, specifically relating to a coagulation bath and its application and regeneration methods. Background Technology

[0002] Chemical fibers are typically obtained from cellulose solutions through wet spinning. The coagulation bath, used in wet spinning, precipitates cellulose from the solution and forms fibers, playing a decisive role in the fiber's morphology and properties. This process usually involves both physical and chemical processes. The physical process is a dual diffusion process between solvent and non-solvent, causing the solution to form a gel and solidify. The chemical process involves cellulose derivatives transforming into cellulose through chemical reactions, or by chemically disrupting the chemical composition of the cellulose solvent, causing it to lose its ability to dissolve cellulose, thus obtaining cellulose.

[0003] Traditional coagulation baths are usually aqueous solutions containing sulfuric acid and sulfates. However, the corrosiveness of these coagulation baths and their excessively fast coagulation rate result in irregular fiber structures, affecting fiber quality. Summary of the Invention

[0004] The purpose of this invention is to provide a coagulation bath and its application and regeneration methods. The coagulation bath provided by this invention has a moderate coagulation rate, requires low-cost reagents with low corrosivity, and facilitates the formation of regular fiber structures during the coagulation process, thereby improving fiber quality.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The present invention provides a coagulation bath, including coagulation bath 1 or coagulation bath 2;

[0007] The coagulation bath 1 includes H2CO3 and / or X2CO3;

[0008] The coagulation bath 2 includes H2SO3 and / or Y2SO3;

[0009] The X and Y elements are independently selected from at least one of Li, Na, K, Rb, Cs, Fr, and NH4.

[0010] Preferably, the mass concentration of H2CO3 in the coagulation bath 1 is 0.1-0.5%; and the mass concentration of X2CO3 is 0.1-40%.

[0011] Preferably, the mass concentration of H2SO3 in the coagulation bath 2 is 0.1-20%; and the mass concentration of Y2SO3 is 0.1-40%.

[0012] Preferably, the coagulation bath further includes additives; the additives include urea and / or thiourea;

[0013] The mass concentration of the additive is 0.4% to 40%.

[0014] The present invention also provides a method for applying a coagulation bath, comprising the following steps:

[0015] Prepreg was prepared using an alkaline natural polymer solution as a raw material;

[0016] The prepreg is passed into a coagulation bath for molding to obtain nascent fibers and a coagulation bath to be regenerated.

[0017] The coagulation bath is the coagulation bath described in the above technical solution.

[0018] Preferably, the alkaline natural polymer solution comprises natural polymer materials, metal hydroxides, additives, and water;

[0019] The mass concentration of the natural polymer material is 5-9%, and the degree of polymerization of the natural polymer material is 200-800.

[0020] The mass concentration of the auxiliary agent is 0.01-15%;

[0021] The mass concentration of the metal hydroxide is 2-15%.

[0022] Preferably, the molding temperature is 10–80°C.

[0023] The present invention also provides a method for regenerating a coagulation bath, comprising the following steps:

[0024] The condensate bath to be regenerated is brought into contact with the regeneration gas to obtain the regenerated condensate bath;

[0025] The coagulation bath to be regenerated is the coagulation bath to be regenerated obtained in the application method described in the above technical solution;

[0026] The regenerated gas is carbon dioxide or sulfur dioxide.

[0027] Preferably, when the coagulation bath is coagulation bath 1, the mass concentration of XHCO3 in the regenerated coagulation bath is 0.1-20 wt%.

[0028] When the coagulation bath is coagulation bath 2, the mass concentration of XHSO3 in the regenerated coagulation bath is 0.1-20 wt%.

[0029] The X and Y elements are independently selected from at least one of Li, Na, K, Rb, Cs, Fr, and NH4.

[0030] Preferably, the contact temperature is 30–60°C.

[0031] This invention provides a coagulation bath, comprising coagulation bath 1 or coagulation bath 2; coagulation bath 1 comprises H2CO3 and / or X2CO3; coagulation bath 2 comprises H2SO3 and / or Y2SO3; wherein X and Y independently comprise at least one of Li, Na, K, Rb, Cs, Fr, and NH4. The coagulation bath provided by this invention has a moderate coagulation rate, requires low-cost reagents, and exhibits low corrosivity. During coagulation, it facilitates the formation of a regular fiber structure, thereby improving fiber quality.

[0032] The present invention also provides a method for applying a coagulation bath, comprising the following steps: preparing a prepreg using an alkaline natural polymer solution as raw material; passing the prepreg into a coagulation bath for molding to obtain nascent fibers and a coagulation bath to be regenerated.

[0033] This invention also provides a method for regenerating a coagulation bath, comprising the following steps: contacting the coagulation bath to be regenerated with a regenerating gas to obtain a regenerated coagulation bath; the coagulation bath to be regenerated is the coagulation bath obtained in the application method described above; the regenerating gas is carbon dioxide or sulfur dioxide. This invention regenerates the coagulation bath into bicarbonate or bisulfite through sulfation with carbon dioxide or sulfur dioxide, enabling the regenerated coagulation bath to be recycled up to 100 times. Attached Figure Description

[0034] Figure 1 The molding and regeneration system provided by the present invention comprises: 1-coagulation bath, 2-first evaporation tower, 3-acidification tower, 4-second evaporation tower, 5-filtration device, 6-drying device, 7-sedimentation tank, and 8-filter tank. Detailed Implementation

[0035] The present invention provides a coagulation bath, including coagulation bath 1 or coagulation bath 2;

[0036] The coagulation bath 1 includes H2CO3 and / or X2CO3;

[0037] The coagulation bath 2 includes H2SO3 and / or Y2SO3;

[0038] The X and Y elements are independently selected from at least one of Li, Na, K, Rb, Cs, Fr, and NH4.

[0039] In this invention, unless otherwise specified, all components are commercially available products well known to those skilled in the art.

[0040] In this invention, the mass concentration of H2CO3 in the coagulation bath 1 is preferably 0.1-0.5%, more preferably 0.1-0.3%, and even more preferably 0.1-0.2%. In this invention, the mass concentration of X2CO3 is preferably 0.1-40%, more preferably 5-35%, and even more preferably 10-30%. In this invention, the solvent in the coagulation bath 1 is preferably water.

[0041] In this invention, the mass concentration of H2SO3 in the coagulation bath 2 is preferably 0.1-20%, more preferably 5-18%, and even more preferably 10-15%. In this invention, the mass concentration of Y2SO3 is preferably 0.1-40%, more preferably 5-35%, and even more preferably 10-30%. In this invention, the solvent in the coagulation bath 2 is preferably water.

[0042] In this invention, the coagulation bath preferably includes additives; the additives preferably include urea and / or thiourea; the mass concentration of the additives is preferably 0.4-40%, more preferably 5-35%, and even more preferably 10-30%.

[0043] The present invention does not impose any special limitations on the preparation method of the coagulation bath; the raw materials contained herein can be mixed evenly directly.

[0044] The present invention also provides a method for applying a coagulation bath, comprising the following steps:

[0045] Prepreg was prepared using an alkaline natural polymer solution as a raw material;

[0046] The prepreg is passed into a coagulation bath for molding to obtain nascent fibers and a coagulation bath to be regenerated.

[0047] The coagulation bath is the coagulation bath described in the above technical solution.

[0048] This invention uses an alkaline natural polymer solution as a raw material to prepare a prepreg.

[0049] In this invention, the alkaline natural polymer solution preferably comprises a natural polymer material, a metal hydroxide, an additive, and water. In this invention, the natural polymer material preferably comprises at least one selected from cellulose, cellulose carbamate, chitin, and chitosan. In this invention, the mass concentration of the natural polymer material is preferably 5-9%, more preferably 6-8%; the degree of polymerization of the natural polymer material is preferably 200-800, more preferably 300-700, and even more preferably 400-500.

[0050] In this invention, the metal hydroxide preferably includes at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide. In this invention, the mass concentration of the metal hydroxide is preferably 2-15%, more preferably 5-12%, and even more preferably 8-10%.

[0051] In this invention, the auxiliary agent preferably includes at least one selected from urea, zinc oxide, and thiourea. In this invention, the mass concentration of the auxiliary agent is preferably 0-15%, more preferably 1-12%, and even more preferably 5-10%.

[0052] In this invention, the preferred method for preparing the alkaline natural polymer solution includes the following steps: mixing a natural polymer material, a metal hydroxide, an additive, and water, followed by degassing to obtain the alkaline natural polymer solution. This invention does not impose any particular limitation on the mixing and degassing processes; any process well-known to those skilled in the art can be used.

[0053] In this invention, the prepreg preferably comprises a filamentous prepreg or a film-like prepreg. The preparation of the filamentous prepreg preferably involves wet spinning the alkaline natural polymer solution. The preparation of the film-like prepreg preferably involves extruding the alkaline natural polymer solution. This invention does not impose any particular limitation on the wet spinning and extrusion processes; any process well-known to those skilled in the art can be used.

[0054] After obtaining the prepreg, the present invention introduces the prepreg into a coagulation bath for molding to obtain nascent fibers and a coagulation bath to be regenerated. The coagulation bath is the coagulation bath described in the above technical solution.

[0055] In this invention, the molding temperature is preferably 10–80°C, more preferably 20–70°C, and even more preferably 30–40°C. In this invention, the molding process also preferably includes a 20–30% positive stretching of the prepreg. This invention does not impose any special limitations on the specific molding process; any process well-known to those skilled in the art can be used.

[0056] In this invention, when the additive in the alkaline natural polymer solution is zinc oxide, zinc carbonate precipitate is preferably formed during the molding process; when the additive is urea and / or thiourea, the additive preferably accumulates in the coagulation bath during the molding process. In this invention, the accumulation of the additive is beneficial to improving the performance of the product.

[0057] In this invention, the nascent fibers preferably include filamentous nascent fibers and film-like nascent fibers. After obtaining the nascent fibers, the invention further preferably includes sequentially washing, oiling, and drying the nascent fibers. In this invention, the washing temperature is preferably 65°C. The oiling process is not particularly limited in this invention and can be any process well known to those skilled in the art. In this invention, the drying conditions for the filamentous nascent fibers are preferably performed at 130°C. In this invention, the drying conditions for the film-like nascent fibers preferably include sequential hot air drying at 70°C, 90°C, and 60°C.

[0058] In this invention, when the coagulation bath is coagulation bath 1, the mass concentration of X₂CO₃ in the coagulation bath to be regenerated is preferably 0.2% to 45%. In this invention, when the coagulation bath is coagulation bath 2, the mass concentration of X₂SO₃ in the coagulation bath to be regenerated is preferably 0.2% to 45%. In this invention, the coagulation bath to be regenerated preferably also includes additives; the mass concentration of the additives is preferably 0.01% to 40%, but does not exceed 40%.

[0059] The present invention also provides a method for regenerating a coagulation bath, comprising the following steps:

[0060] The condensate bath to be regenerated is brought into contact with the regeneration gas to obtain the regenerated condensate bath;

[0061] The coagulation bath to be regenerated is the coagulation bath to be regenerated obtained in the application method described in the above technical solution;

[0062] The regenerated gas is carbon dioxide or sulfur dioxide.

[0063] Prior to the contact, the present invention preferably includes filtering and dewatering the coagulation bath to be regenerated. The filtration process is not particularly limited in the present invention and can be any method well known to those skilled in the art. In the present invention, filtration can remove micelles or precipitates generated when the additive is zinc oxide from the coagulation bath to be regenerated. In the present invention, the dewatering method is preferably low-temperature multi-effect evaporation or membrane concentration.

[0064] In this invention, the contact temperature is preferably 30–60°C, more preferably 40–50°C. This invention does not impose any particular limitation on the contact method; any resin-based method used by those skilled in the art is acceptable. In a specific embodiment of this invention, the contact is preferably a countercurrent contact.

[0065] In this invention, when the coagulation bath is coagulation bath 1, the mass concentration of XHCO3 in the regenerated coagulation bath is preferably 0.1–20 wt%. In this invention, when the coagulation bath is coagulation bath 2, the mass concentration of XHSO3 in the regenerated coagulation bath is preferably 0.1–20 wt%. In this invention, X and Y independently include at least one of Li, Na, K, Rb, Cs, Fr, and NH4. In this invention, the regenerated coagulation bath preferably also includes an additive; the mass concentration of the additive is preferably 0.01–40%, but does not exceed 40%.

[0066] In this invention, when the mass concentration of urea and / or thiourea in the coagulation bath to be regenerated is preferably ≥40%, the invention also preferably includes a first post-treatment or a second post-treatment of the coagulation bath to be regenerated.

[0067] In this invention, the first post-processing preferably includes evaporating and crystallizing the coagulation bath to be regenerated, followed by filtration and drying to obtain bicarbonate and urea or thiourea, respectively. In this invention, the evaporation and crystallization temperature of the bicarbonate is preferably 40–50°C; the evaporation and crystallization temperature of the urea or thiourea is preferably 55–80°C. This invention does not impose any particular limitation on the evaporation and crystallization process; any process well known to those skilled in the art can be used.

[0068] In this invention, the second post-treatment preferably includes mixing the coagulation bath to be regenerated and quicklime, followed by filtration to obtain a treated liquid. In this invention, the treated liquid preferably includes hydroxides, urea, and / or thiourea, which can be used to dissolve natural polymer materials.

[0069] In this invention, the use of a first post-treatment and a second post-treatment solves the problem of recycling high-concentration salt, reduces production difficulty and cost, and has broad application prospects.

[0070] In this invention, the application and regeneration of the coagulation bath are preferably carried out in a molding and regeneration system.

[0071] In this invention, the molding and regeneration system preferably includes a coagulation bath 1, a first evaporation tower 2, and an acidification tower 3 connected in sequence.

[0072] In this invention, the coagulation bath 1 is used to mix the prepreg and the coagulation bath for molding; the first evaporation tower 2 is used to remove water from the coagulation bath to be regenerated; and the acidification tower 3 is used to regenerate the coagulation bath to be regenerated by contacting the regenerated gas.

[0073] In this invention, the first evaporation tower 2 is preferably connected in sequence to the second evaporation tower 4, the filter device 5, and the drying device 6; the second evaporation tower 4, the filter device 5, and the drying device 6 are used for the first post-treatment. In this invention, the filter device 5 is preferably a centrifuge; the drying device 6 is preferably at least one of a flash dryer, a disc continuous dryer, a fluidized bed dryer, a vacuum rake dryer, and a rotary drum dryer.

[0074] In this invention, the coagulation bath 1 is preferably connected in sequence to the sedimentation tank 7 and the filter tank 8; the sedimentation tank 7 and the filter tank 8 are used for the second post-treatment.

[0075] To further illustrate the present invention, a coagulation bath and its application and regeneration methods provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0076] Example 1

[0077] Cellulose with a degree of polymerization of 400 was dissolved in a mixture of sodium hydroxide, urea and water (in a mass ratio of 7:12:81), and degassed to obtain an alkaline natural polymer solution with a cellulose mass concentration of 7.5 wt%.

[0078] The obtained solution is wet-spun to obtain a fiber stream. The fiber stream is then shaped by passing it through a coagulation bath composed of a saturated carbonic acid solution at a temperature of 20°C and subjected to 30% positive drawing to obtain nascent fibers and a coagulation bath to be regenerated (wherein, the sodium carbonate content is 0.13 wt% and the urea content is 0.22 wt%).

[0079] The obtained nascent fibers were sequentially washed with hot water at 65℃, oiled, and dried at 110℃ to obtain cellulose long fibers; the density of the fiber long fibers was 133 dtex, the dry elongation was 12.1%, and the average strength was 1.7 cN / dtex.

[0080] Example 2

[0081] Cellulose with a degree of polymerization of 250 was dissolved in a mixture of sodium hydroxide, urea and water (in a mass ratio of 7:5:87), and degassing was performed to obtain an alkaline natural polymer solution with a cellulose mass concentration of 8 wt%.

[0082] The obtained solution is wet-spun to obtain a fiber stream. The fiber stream is then shaped by passing it through a coagulation bath composed of a saturated carbonic acid solution and sodium carbonate with a mass concentration of 3.2%. The temperature of the coagulation bath is 20°C, and a 30% positive draw is performed to obtain nascent fibers and a coagulation bath to be regenerated (wherein, the sodium carbonate content is 3.3 wt% and the urea content is 0.11 wt%).

[0083] The nascent fibers were washed with hot water at 65°C, oiled, and dried at 110°C to obtain cellulose long fibers. The density of the cellulose long fibers was 133 dtex, the dry elongation was 15.0%, and the average strength was 1.9 cN / dtex.

[0084] Example 3

[0085] Cellulose with a degree of polymerization of 400 was dissolved in a mixture of sodium hydroxide, urea and water (in a mass ratio of 7:12:81), and degassed to obtain an alkaline natural polymer solution with a cellulose mass concentration of 7.5 wt%.

[0086] The obtained solution is wet-spun to obtain fiber streams. The fiber streams are then formed in a coagulation bath composed of a saturated carbonic acid solution, sodium carbonate with a mass concentration of 3.2% and urea with a mass concentration of 10%. The temperature of the coagulation bath is 20°C, and 30% positive drawing is performed to obtain nascent fibers and a coagulation bath to be regenerated (wherein, the sodium carbonate content is 3.4 wt% and the urea content is 10.1 wt%).

[0087] The nascent fibers were washed with hot water at 65°C, oiled, and dried at 110°C to obtain cellulose long fibers. The density of the cellulose long fibers was 133 dtex, the dry elongation was 16%, and the average strength was 2.3 cN / dtex.

[0088] Example 4

[0089] Chitin with a degree of polymerization of 250 was dissolved in a mixture of potassium hydroxide, urea and water (the mass ratio of sodium hydroxide, urea and water was 12.7:5.7:81.6), and degassing was performed to obtain an alkaline natural polymer solution with a chitin mass concentration of 7 wt%.

[0090] The obtained solution is wet-spun to obtain fiber streams. The fiber streams are then formed in a coagulation bath composed of a saturated carbonic acid solution, potassium carbonate with a mass concentration of 10.3% and urea with a mass concentration of 14%. The temperature of the coagulation bath is 10°C, and 20% positive drawing is performed to obtain nascent fibers and a coagulation bath to be regenerated (wherein, the potassium carbonate content is 11 wt% and the urea content is 14.2 wt%).

[0091] The nascent fibers were washed with hot water at 65°C, oiled, and dried at 110°C to obtain cellulose long fibers. The density of the cellulose long fibers was 133 dtex, the dry elongation was 15.3%, and the average strength was 2.0 cN / dtex.

[0092] Example 5

[0093] Cellulose carbamate with a degree of polymerization of 250 was dissolved in a mixture of sodium hydroxide and water (the mass ratio of sodium hydroxide to water was 9:91), and degassing was performed to obtain an alkaline natural polymer solution with a cellulose carbamate mass concentration of 8.5 wt%.

[0094] The obtained solution is extruded and sprayed into a film, and then formed in a coagulation bath composed of saturated carbonic acid solution, sodium carbonate with a mass concentration of 4.8% and urea with a mass concentration of 15%. The temperature of the coagulation bath is 20°C, and 30% positive stretching is performed to obtain a nascent fiber membrane and a coagulation bath to be regenerated (wherein, the sodium carbonate content is 4.9 wt% and the urea content is 15.2 wt%).

[0095] The obtained nascent fiber membrane was washed with hot water at 65°C, soaked in 30% glycerol and oiled, and then dried with hot air at 70°C, 90°C and 60°C respectively. After being rolled up, a cellulose film was obtained.

[0096] The cellulose film has high transparency and uniform thickness, with a longitudinal strength of 128 MPa and an elongation at break of 16.7%; a transverse strength of 110 MPa and an elongation at break of 26.7%.

[0097] Example 6

[0098] The coagulation bath to be regenerated obtained in Example 1 was transferred to the first evaporation tower, and the water was evaporated to obtain a mixed liquid with a sodium carbonate concentration of 13 wt% and a urea content of 22 wt%.

[0099] The resulting mixture was passed into an acidification tower at a temperature of 55°C and contacted countercurrently with carbon dioxide gas to obtain a regenerated coagulation bath with a sodium bicarbonate concentration of 10 wt% and a urea content of 22 wt%.

[0100] The obtained regenerated coagulation bath is recycled back to the coagulation bath tank, and long fibers are prepared according to the method of Preparation Example 1;

[0101] After repeating the above method 10 times, the properties of the prepared long fiber are basically the same as those of the long fiber obtained in Example 1, with a linear density of 133 dtex, a dry elongation of 15.6%, and an average strength of 2.2 cN / dtex.

[0102] Example 7

[0103] The coagulation bath to be regenerated obtained in Example 2 was transferred to the first evaporation tower, and the water was evaporated to obtain a mixed solution with a sodium carbonate concentration of 6.4 wt% and a urea content of 0.22 wt%.

[0104] The resulting mixture was passed into an acidification tower at a temperature of 35°C and contacted countercurrently with carbon dioxide gas to obtain a regenerated coagulation bath with a sodium bicarbonate concentration of 10 wt% and a urea content of 0.22 wt%.

[0105] The obtained regenerated coagulation bath is recycled back to the coagulation bath tank, and long fibers are prepared according to the method of Preparation Example 2;

[0106] After 20 cycles of the above method, the properties of the prepared long fiber are basically the same as those of the long fiber obtained in Example 2, with a linear density of 133 dtex, a dry elongation of 16%, and an average strength of 2.2 cN / dtex.

[0107] Example 8

[0108] The coagulation bath to be regenerated obtained in Example 3 was transferred to the first evaporation tower, and the water was evaporated to obtain a mixed solution with a sodium carbonate concentration of 6.4 wt% and a urea content of 20.2 wt%.

[0109] The resulting mixture was passed into an acidification tower at a temperature of 40°C and contacted countercurrently with carbon dioxide gas to obtain a regenerated coagulation bath with a sodium bicarbonate concentration of 10 wt% and a urea content of 20.2 wt%.

[0110] The obtained regenerated coagulation bath was recycled back to the coagulation bath tank, and long fibers were prepared according to the method of Preparation Example 3;

[0111] After 50 cycles of the above method, the properties of the prepared long fiber are basically the same as those of the long fiber obtained in Example 3, with a linear density of 133 dtex, a dry elongation of 15%, and an average strength of 2.5 cN / dtex.

[0112] Example 9

[0113] The coagulation bath to be regenerated obtained in Example 4 was transferred to the first evaporation tower, and the water was evaporated to obtain a mixed solution with a potassium carbonate concentration of 13.8 wt% and a urea content of 20.2 wt%.

[0114] The resulting mixture was passed into an acidification tower at a temperature of 40°C and contacted countercurrently with carbon dioxide gas to obtain a regenerated coagulation bath with a potassium bicarbonate concentration of 20.0 wt% and a urea content of 20.2 wt%.

[0115] The obtained regenerated coagulation bath was recycled back to the coagulation bath tank, and long fibers were prepared according to the method of Preparation Example 4.

[0116] After 50 cycles of the above method, the properties of the prepared long fiber are basically the same as those of the long fiber obtained in Example 4, with a linear density of 133 dtex, a dry elongation of 15.3%, and an average strength of 2.50 cN / dtex.

[0117] Example 10

[0118] The coagulation bath to be regenerated obtained in Example 5 was transferred to the first evaporation tower, and the water was evaporated to obtain a mixed solution with a sodium carbonate concentration of 6.4 wt% and a urea content of 20.2 wt%.

[0119] The resulting mixture was passed into an acidification tower at a temperature of 40°C and contacted countercurrently with carbon dioxide gas to obtain a regenerated coagulation bath with a sodium bicarbonate concentration of 10 wt% and a urea content of 20.2 wt%.

[0120] The obtained regenerated coagulation bath was recycled back to the coagulation bath tank, and fiber films were prepared according to the method of Preparation Example 5;

[0121] After 50 cycles of the above method, the properties of the fiber film prepared are basically the same as those of the long fiber obtained in Example 5, with a longitudinal strength of 125 MPa and an elongation at break of 15.7%; a transverse strength of 108 MPa and an elongation at break of 25.7%.

[0122] Example 11

[0123] The coagulation bath to be regenerated obtained in Example 3 was transferred to the first evaporation tower, and the water was evaporated to obtain a mixed solution with a sodium carbonate concentration of 6.4 wt% and a urea content of 20.2 wt%.

[0124] The resulting mixture was passed into an acidification tower at a temperature of 40°C and contacted countercurrently with carbon dioxide gas to obtain a regenerated coagulation bath with a sodium bicarbonate concentration of 10 wt% and a urea content of 20.2 wt%.

[0125] The obtained regenerated coagulation bath was recycled back to the coagulation bath tank, and long fibers were prepared according to the method of Preparation Example 3;

[0126] After 100 cycles of the above method, the properties of the prepared long fiber are basically the same as those of the long fiber obtained in Example 3, with a linear density of 133 dtex, a dry elongation of 15%, and an average strength of 2.5 cN / dtex.

[0127] After 100 cycles of coagulation bath (with a urea concentration of 40 wt%), quicklime is added to the coagulation bath to react. After filtration and separation, a solution containing sodium hydroxide and urea is obtained. After precipitation, filtration and membrane concentration, the ratio is adjusted to obtain a regenerated sodium hydroxide / urea / water (mass ratio of 7:5:87) solvent, which is used to dissolve natural polymer materials.

[0128] Comparative Example 1

[0129] The method of Example 1 differs in that the coagulation bath is a sulfuric acid coagulation bath system (specifically composed of 110 g / L sulfuric acid and 150 g / L sodium sulfate);

[0130] The obtained fiber long yarns had a dry elongation of 8.1% and an average strength of 1.6 cN / dtex.

[0131] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for applying a coagulation bath, characterized in that, Includes the following steps: Prepreg was prepared using an alkaline natural polymer solution as a raw material; The prepreg is passed into a coagulation bath for molding to obtain nascent fibers and a coagulation bath to be regenerated. The condensate bath to be regenerated and the regeneration gas are brought into countercurrent contact to obtain a regenerated condensate bath; the regeneration gas is carbon dioxide. The obtained regenerated coagulation bath is circulated back into the coagulation bath tank to prepare long fibers. After multiple cycles, when the mass concentration of urea and / or thiourea in the regenerated coagulation bath is ≥40%, the regenerated coagulation bath is subjected to a first post-treatment or a second post-treatment. The first post-processing includes evaporating and crystallizing the regenerated coagulation bath, filtering and drying to obtain bicarbonate, urea and / or thiourea; The second post-treatment includes mixing the regenerated coagulation bath and quicklime and then filtering the mixture to obtain a treatment solution; the treatment solution includes hydroxide, urea and / or thiourea. The coagulation bath is a mixture of saturated H2CO3, X2CO3, and additives; X is Na or K; the mass concentration of X2CO3 is 3.2%~40%. The additives include urea and / or thiourea; the mass concentration of the additives is 0.4% to 40%. The alkaline natural polymer solution comprises a natural polymer material, a metal hydroxide, an additive, and water; the additive comprises at least one of urea and thiourea; the mass concentration of the natural polymer material is 5-9%, and the degree of polymerization of the natural polymer material is 200-800; the mass concentration of the metal hydroxide is 2-15%.

2. The application method according to claim 1, characterized in that, The mass concentration of the auxiliary agent is 0.01~15%.

3. The application method according to claim 1, characterized in that, The molding temperature is 10~80℃.

4. The application method according to claim 1 or 3, characterized in that, The molding process also includes a 20-30% positive stretching of the prepreg.

5. The application method according to claim 1, characterized in that, The nascent fibers include filamentous nascent fibers or film-like nascent fibers.

6. The application method according to claim 5, characterized in that, After obtaining the nascent fibers, the process further includes sequentially washing, oiling, and drying the nascent fibers; the washing temperature is 65°C; the drying conditions for the filamentous nascent fibers are drying at 130°C; and the drying conditions for the film-like nascent fibers include sequential hot air drying at 70°C, 90°C, and 60°C.

7. The application method according to claim 1, characterized in that, The temperature of the countercurrent contact is 30~60℃.

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