Environment-friendly efficient washing equipment and process in para-aramid fiber production process

Abstract

The invention discloses environment-friendly efficient washing equipment and technology in the para-aramid fiber production process, and belongs to the technical field of aramid fiber production, the environment-friendly efficient washing equipment comprises a first-stage washing box, a second-stage washing box, a third-stage washing box and a four-roller machine, the first-stage washing box, the second-stage washing box and the third-stage washing box are the same in structure, a pair of washing rollers are arranged in the washing boxes in an up-down corresponding mode, and the four-roller machine is connected with the first-stage washing box and the second-stage washing box. A plurality of water pipes and spraying heads are fixedly installed at the top of the washing box, the spraying heads are fixed to the bottoms of the water pipes, the two washing rollers are located below the spraying heads, a vacuum suction device is arranged between the two washing rollers and extends in the axial direction of the washing rollers, and the two ends of the vacuum suction device are fixed to the wall of the washing box; a first drawing roller, a second drawing roller and a pair of extrusion rollers are arranged in the four-roller machine. Spraying, extruding and vacuum suction are used as main modes, aramid fibers are cleaned, the technological process is short, operation is easy, the washing effect is good, the product quality is stable, and the treatment process meets the requirement for green processing and manufacturing.

Description

Technical Field

[0001] The invention relates to the technical field of aramid fiber production, in particular to green and efficient water washing equipment and process in the production process of para-aramid fibers. Background Art

[0002] Aromatic polyamide fiber refers to a linear polymer with at least 85% amide bonds and two benzene ring groups connected. It is mainly divided into two categories: para-aramid and meta-aramid. It has the properties of high strength, corrosion resistance, high modulus, high temperature resistance, insulation, and good fatigue resistance.

[0003] The washing process of para-aramid fiber is an important factor affecting the quality of para-aramid fiber, and the washing effect directly affects the physical and mechanical properties of aramid fiber. On the one hand, the residual solvent in the para-aramid fiber will change the cross-sectional shape of the fiber during the drying and densification process, forming some irregular peeling, and the surface will be etched to form gullies, making the originally smooth fiber surface rough, resulting in hairy and broken fibers, etc., affecting subsequent processing and product quality.

[0004] On the other hand, aramid is an organic synthetic fiber with high modulus and high strength made from poly(p-phenylene terephthalamide) using liquid crystal spinning technology. Its molecular chain is a full benzene ring structure, which is relatively rigid and difficult to fold. Therefore, its molecular chain is a semi-straight chain conformation in the crystal region. Aramid fiber contains several levels of microstructures, including a crystalline structure and a skin-core structure. During the solidification process of the fiber, the differences in length, gaps and fibril orientation between the skin and core of the fiber form a skin-core structure. The presence of solvents will destroy the skin-core structure of the fiber, causing crystal defects in the fiber, resulting in a decrease in the mechanical properties of the fiber, a decrease in high temperature resistance, abnormal dyeing, etc., affecting the subsequent processing and application of the fiber, and is not conducive to the preparation of high-quality para-aramid fiber. Therefore, in production, the solvent remaining in the fiber must be washed as clean as possible to avoid affecting subsequent processing and use. Summary of the invention

[0005] The residual sulfuric acid in the para-aramid fiber will reduce the breaking strength and initial modulus of the fiber, and it is impossible to prepare high-quality para-aramid fiber. As time goes by, the residual sulfuric acid in the fiber will further accelerate the decline of the physical and mechanical properties of the fiber, and the stability of product quality cannot be guaranteed. The present invention provides a design and development of a green and efficient washing process for para-aramid fiber to prepare a high-quality para-aramid fiber.

[0006] A green and efficient water washing equipment in the production process of para-aramid fiber comprises a primary water washing box, a secondary water washing box, a tertiary water washing box and a four-roller machine which are sequentially arranged along the conveying direction of the para-aramid fiber. The primary water washing box, the secondary water washing box and the tertiary water washing box have the same structure. A pair of water washing rollers are correspondingly arranged in the upper and lower parts of the water washing box. A plurality of water pipes and spray heads are fixedly installed on the top of the water washing box. The spray heads are fixed on the bottom of the water pipes. Two water washing rollers are located below the spray heads. The bottoms of the two water washing rollers are fixed on the water washing roller bases. A vacuum suction device is arranged between the two water washing rollers. The vacuum suction device extends along the axial direction of the water washing rollers and has both ends fixed on the wall of the water washing box. A first drafting roller, a second drafting roller and a pair of squeezing rollers are sequentially arranged in the four-roller machine along the conveying direction of the para-aramid fiber.

[0007] Furthermore, the shells of the water washing box and the four-roller machine are both vertical rectangular blocks with a hollow interior and a missing top surface.

[0008] The process of using the green and efficient water washing equipment in the production process of the above-mentioned para-aramid fiber for efficient water washing is as follows: The para-aramid fiber first bypasses the washing roller of the primary washing box, is sprayed by the spray head and then is vacuum sucked by a vacuum suction device, then bypasses the washing roller of the secondary washing box, is sprayed by the spray head and then is vacuum sucked by a vacuum suction device, then bypasses the washing roller of the tertiary washing box, is sprayed by the spray head and then is vacuum sucked by a vacuum suction device, finally reaches the four-roller machine, is stretched by the first and second stretching rollers, and then enters the squeezing roller to squeeze out the solvent that has penetrated into it.

[0009] Furthermore, the temperature of water sprayed from the spray head is 10-90°C, the speed of the water washing roller is 50-450m / min, the tension of the water washing roller is 0.1-0.3g / d, the vacuum suction pressure of the vacuum suction device is 20-100kPa, and the angle of the spray head is 30-150°.

[0010] More preferably, the temperature of water sprayed from the spray head is 30-50°C, the speed of the water washing roller is 250-350 m / min, the tension of the water washing roller is 0.15-0.2 g / d, the vacuum suction pressure of the vacuum suction device is 60-80 kPa, and the angle of the spray head is 60-120°.

[0011] After the para-aramid fiber is coagulated and formed in a coagulation bath, a small amount of sulfuric acid is contained inside. The para-aramid fiber is introduced into a high-efficiency water washing device for cleaning, and the residual sulfuric acid in the para-aramid fiber is removed by washing.

[0012] Compared with the conventional washing process of para-aramid fiber, the advantages and effects of the present invention are as follows: (1) Product quality: The liquid repeatedly falls and is squeezed out with the roller under the action of centrifugal force. Clean water immediately falls on the surface of the silk thread when the silk thread reaches the roller surface, which further improves the washing effect of the fiber while ensuring the stability of product quality.

[0013] (2) Short process: The present invention mainly adopts spraying, extrusion and vacuum suction to clean the fiber, and the process flow is short and the operation is simple.

[0014] (3) Cleaning effect: The water used for high-efficiency water washing is soft water or pure water. The water is sprayed on the para-aramid fiber using a spray head to ensure that the contact efficiency between the liquid and the para-aramid fiber is maximized. The frequent contact and exchange between the silk thread surface and the liquid can improve the fiber washing effect.

[0015] (4) Economic and environmentally friendly: The present invention uses spraying, extrusion, and vacuum suction as the main methods to clean aramid fibers. Compared with the traditional immersion cleaning method, this process has a short process flow, simple operation, good washing effect, stable product quality, and the processing process meets the requirements of green processing and manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the green and efficient washing process of para-aramid fiber of the present application; Figure 2 It is a schematic diagram of the front structure of the high-efficiency water washing equipment; Figure 3 It is a side schematic diagram of the washing box structure; In the figure: 1. water pipe, 2. spray head, 31. upper water washing roller, 32. lower water washing roller, 4. vacuum suction device, 51. primary water washing box, 52. secondary water washing box, 53. tertiary water washing box, 6. four-roller machine, 71. first drafting roller, 72. second drafting roller, 8. squeezing roller, 9. para-aramid fiber, 10. water washing roller base. DETAILED DESCRIPTION

[0017] See also Figure 2 , Figure 3A green and efficient water washing equipment in the production process of para-aramid fiber comprises a primary water washing box 51, a secondary water washing box 52, a tertiary water washing box 53 and a four-roller machine 6 which are sequentially arranged along the conveying direction of the para-aramid fiber 9. The primary water washing box 51, the secondary water washing box 52 and the tertiary water washing box 53 have the same structure. A pair of upper water washing rollers 31 and a lower water washing roller 32 are correspondingly arranged in the water washing box. A plurality of water pipes 1 and a spray head 2 are fixedly installed on the top of the water washing box. The spray head 2 is fixed at the bottom of the water pipe 1. The two water washing rollers 31 and 32 are located below the spray head 2. The bottoms of the two water washing rollers 31 and 32 are fixed on the water washing roller base 10. A vacuum suction device 4 is arranged between the two water washing rollers. The vacuum suction device 4 extends along the axial direction of the water washing roller and its two ends are fixed on the wall of the water washing box. A first drafting roller 71, a second drafting roller 72 and a pair of squeezing rollers 8 are sequentially arranged in the four-roller machine 6 along the conveying direction of the para-aramid fiber 9.

[0018] The shells of the water washing box and the four-roller machine 6 are both vertical rectangular parallelepipeds with hollow interiors and missing top surfaces, and the two water washing rollers 31 and 32 are respectively located on the upper and lower sides of the water washing box. The para-aramid fiber 9 is sequentially washed with primary water from the left end (bypassing the washing rollers 31 and 32, and entering the vacuum suction device 4 after being sprayed by the spray head 2. The vacuum suction device 4 is fixedly installed between the front wall and the rear wall of the washing box 5, and is located on the inner side of the para-aramid fiber 9. The bottoms of the two washing rollers 31 and 32 are fixedly installed on the washing roller base 10. A water pipe 1 is fixedly installed on the top of the washing box, a water pump is fixedly installed on the top of the water pipe 1, and a spray head 2 is fixedly installed on the bottom of the water pipe 1. Through the setting of the upper and lower pairs of washing rollers 31 and 32, the para-aramid fiber to be cleaned is wound around its outer side), and then sequentially washed with secondary water and tertiary water, and finally reaches the four-roller machine 6 (after being drafted by the first drafting roller 71 and the second drafting roller 72, it enters the squeezing roller 8). After starting the motor, the washing roller can be driven to rotate, thereby driving the para-aramid fiber to move. The washing box is filled with washing water. Before the para-aramid fiber 9 enters the washing box 5, water is pressed into the water pipe 1 by a water pump and finally sprayed out from the spray head 2. The spray head 2 sprays and rinses the para-aramid fiber 9, and uses the impact force to wash down most of the impurities. Then, the para-aramid fiber 9 enters the vacuum suction device 4 under the guidance of the washing roller to remove the acid mist and impurities generated by the washing. The para-aramid fiber 9 is sucked by the vacuum suction device 4 during the movement, which further improves the cleaning effect. After the para-aramid fiber 9 passes through the suction of the vacuum suction device 4 and enters the right four-roller machine 6 after three-stage washing, it is subjected to the joint action of the drafting rollers 71 and 72 and the squeezing roller 8. The para-aramid fiber 9 is squeezed to squeeze out the solvent that has penetrated into it, further enhancing the cleaning effect and achieving the purpose of efficient cleaning.

[0019] When in use, the motor is started to move the aramid fiber, and the spray head 2 is used to flush the aramid fiber through the water pump. The aramid fiber is sucked by the vacuum suction device and squeezed by the squeezing roller 8 during movement in the washing box, and finally moved out of the four-roller machine 6 to complete the washing process.

[0020] In summary, the green and efficient water washing process of the para-aramid fiber, through the setting of the squeezing roller 8, after the para-aramid fiber 9 passes through the three-stage water washing and vacuum suction device 4, when it passes through the right four-roller machine 6, it is squeezed by the two drafting rollers 71 and 72 and a pair of squeezing rollers 8. The para-aramid fiber 9 is squeezed to squeeze out the solvent that has penetrated into it, further improving the water washing effect and achieving the purpose of efficient washing. The conventional water washing process of the para-aramid fiber is mainly washed by immersion washing, which requires multiple immersion washings, and the washing process is complicated, the water consumption is large, and it is not easy to remove all impurities, resulting in poor washing effect and other problems.

[0021] Breaking strength and breaking elongation Breaking strength: the ratio of yarn breaking strength to yarn linear density, the unit is cN / dtex.

[0022] Elongation at break: The increase in sample length under the action of breaking force. The elongation at break is the percentage of the increase in sample length to the initial length.

[0023] Use a constant rate of extension (CRE) strength tester to stretch the sample at a certain stretching speed until it breaks, and record the breaking strength and breaking elongation values. Refer to the standard of GB / T 42823-2023 "Para-aramid filaments", in which the type of clamps, clamping distance, stretching speed, and pre-tension are all in accordance with the provisions of GB / T 42823-2023 "Para-aramid filaments".

[0024] Initial modulus: Find the point on the stress-strain curve where the change in strength with elongation is the largest (i.e. the point where the tangent angle is the largest), and the slope of the tangent at that point is the initial modulus. Follow the provisions of GB / T 14344-2022 "Test method for tensile properties of chemical fiber filaments".

[0025] Residual sulfuric acid content in tow The washed silk bundles are dried, cut into fine powders and soaked in hot water. The obtained solution is cooled and the pH value of the solution is tested.

[0026] Embodiment 1: The washing temperature will affect the double diffusion between the residual sulfuric acid and the washing liquid of para-aramid fiber. As the washing temperature increases, the molecular movement speed increases, thus affecting the washing effect of the fiber. Therefore, it is necessary to explore the effect of washing temperature on the mechanical properties of para-aramid fiber.

[0027] Process parameters: water washing temperature is 10-90°C, the speed of the water washing roller is 250m / min, the tension of the water washing roller is 0.2g / d, the vacuum suction pressure is 60kPa, and the angle of the spray head is 90° (i.e. the angle between the water pipe and the top of the water washing box).

[0028] Operation process: Figure 1 As shown, the para-aramid fiber 9 (containing a small amount of sulfuric acid) coagulated in the coagulation bath first bypasses the washing roller of the primary washing box 51, is sprayed by the spray head 2, and then is vacuum-sucked by the vacuum suction device 4 to complete the primary washing, then bypasses the washing roller of the secondary washing box 52, is sprayed by the spray head 2, and then is vacuum-sucked by the vacuum suction device 4 to complete the secondary washing, then bypasses the washing roller of the tertiary washing box 53, is sprayed by the spray head 2, and then is vacuum-sucked by the vacuum suction device 4 to complete the tertiary washing, and finally reaches the four-roller machine 6, is drafted by the first drafting roller 71 and the first drafting roller 72, and then enters the squeezing roller 8 to squeeze out the solvent that has penetrated into it. Thereby, the residual sulfuric acid in the para-aramid fiber 9 is removed.

[0029] The washed para-aramid fiber 9 is dried at 120-150° C. to remove moisture from the fiber until the moisture content of the fiber is ≤8-15%, thereby obtaining the para-aramid fiber.

[0030] According to GB / T 42823-2023 “Para-aramid Filament”, the mechanical properties of para-aramid fibers at different washing temperatures are shown in Table 1.

[0031] Table 1 Effect of washing temperature on mechanical properties of para-aramid fiber It can be seen from Table 1 that with the increase of washing temperature, the breaking strength of para-aramid fiber increases first and then decreases. Under comprehensive conditions, the preferred washing temperature is 30-50°C.

[0032] Embodiment 2: The speed of the washing roller affects the orientation of the fiber macromolecules, and then affects the grain size, crystallinity, and orientation inside the fiber, thereby affecting the fiber's breaking strength. Therefore, it is necessary to explore the effect of the washing roller speed on the mechanical properties of para-aramid fibers.

[0033] Process parameters: water washing temperature is 50°C, the speed of the water washing roller is 50-450 m / min, the tension of the water washing roller is 0.2 g / d, the vacuum suction pressure is 60 kPa, and the angle of the spray head is 90°.

[0034] The specific operation process is the same as that of Example 1.

[0035] According to GB / T 42823-2023 “Para-aramid filament”, the mechanical properties of para-aramid fiber at different washing roller speeds are shown in Table 2.

[0036] Table 2 Effect of washing roller speed on mechanical properties of para-aramid It can be seen from Table 2 that with the increase of the washing roller speed, the breaking strength of the para-aramid fiber increases slightly; but when the washing roller speed continues to increase, the mechanical properties of the spun fiber begin to decrease. Under comprehensive conditions, the preferred washing roller speed is 250-350 m / min. Embodiment 3: The magnitude of washing tension directly affects the washing effect of the fiber, and then affects the physical and mechanical properties of the fiber. Therefore, it is necessary to explore the effect of washing tension on the mechanical properties of para-aramid fiber.

[0037] Process parameters: water washing temperature is 50°C, the speed of the water washing roller is 250m / min, the tension of the water washing roller is 0.1-0.2g / d, the vacuum suction pressure is 60kPa, and the angle of the spray head is 90°.

[0038] The specific operation process is the same as that in Example 1.

[0039] According to GB / T 42823-2023 “Para-aramid filament”, the mechanical properties of para-aramid fiber under different washing tensions are shown in Table 3.

[0040] Table 3 Effect of washing tension on mechanical properties of para-aramid It can be seen from Table 3 that with the increase of washing tension, the breaking strength of para-aramid fiber increases slightly; but when the washing tension continues to increase, the mechanical properties of the spun fiber begin to decrease. Under comprehensive conditions, the preferred washing tension is 0.15-0.2 g / d.

[0041] Embodiment 4: The magnitude of the vacuum suction pressure directly affects the washing effect of the fiber, and then affects the physical and mechanical properties of the fiber. Therefore, it is necessary to explore the effect of vacuum suction pressure on the mechanical properties of para-aramid fiber.

[0042] Process parameters: water washing temperature is 50°C, the speed of the water washing roller is 250m / min, the tension of the water washing roller is 0.2g / d, the vacuum suction pressure is 20-100kPa, and the angle of the spray head is 90°.

[0043] The specific operation process is the same as that in Example 1.

[0044] According to GB / T 42823-2023 “Para-aramid filament”, the mechanical properties of para-aramid fibers under different vacuum suction pressures are shown in Table 4.

[0045] Table 4 Effect of vacuum suction pressure on mechanical properties of para-aramid It can be seen from Table 4 that with the increase of vacuum suction pressure, the breaking strength of para-aramid fiber increases slightly; but when the vacuum suction pressure continues to increase, the mechanical properties of the spun fiber begin to decrease. Under comprehensive conditions, the preferred vacuum suction pressure is 60-80 kPa.

[0046] Embodiment 5: The setting angle of the spray head directly affects the washing effect of the fiber, and then affects the physical and mechanical properties of the fiber. Therefore, it is necessary to explore the effect of the setting angle of the spray head on the mechanical properties of para-aramid fiber.

[0047] Process parameters: water washing temperature is 50°C, the speed of the water washing roller is 250m / min, the tension of the water washing roller is 0.2g / d, the vacuum suction pressure is 60kPa, and the angle of the spray head is 30-150°.

[0048] The specific operation process is the same as that of Example 1.

[0049] According to GB / T 42823-2023 “Para-aramid filaments”, the mechanical properties of para-aramid fibers at different spray head setting angles are shown in Table 5.

[0050] Table 5 Effect of the setting angle of the sprinkler head on the mechanical properties of para-aramid It can be seen from Table 5 that as the setting angle of the spray head increases, the breaking strength of the para-aramid fiber increases slightly; but when the setting angle of the spray head continues to increase, the mechanical properties of the spun fiber begin to decrease. Under comprehensive conditions, the preferred setting angle of the spray head is 60-120°.

[0051] Comparative Example 1: Compare the green and efficient washing process of para-aramid fiber with the conventional washing process of para-aramid fiber.

[0052] Green and efficient washing process parameters for para-aramid fiber: washing temperature is 50°C, washing roller speed is 250m / min, washing roller tension is 0.2g / d, vacuum suction pressure is 60kPa, and the spray head setting angle is 90° The specific operation process is the same as that of Example 1.

[0053] The conventional washing process parameters of para-aramid fiber are: washing temperature 30-50℃, washing roller speed 250-350m / min.

[0054] The conventional water washing process of para-aramid fiber is as follows: the para-aramid fiber (containing a small amount of sulfuric acid inside) coagulated in a coagulation bath is introduced into a conventional water washing device (the conventional water washing device is not equipped with a vacuum suction device) for washing, and the residual sulfuric acid in the para-aramid fiber is removed by washing.

[0055] According to GB / T 42823-2023 "Para-aramid Filament", GB / T 14344-2022 "Test method for tensile properties of chemical fiber filaments" and GB / T 534-2014 "Industrial Sulfuric Acid", the performance indicators of para-aramid fiber using green and efficient water washing process and conventional water washing process are compared. The results are shown in Table 6.

[0056] Table 6 Comparison between green and efficient washing process and conventional washing process for para-aramid fiber Para-aramid fiber Green and efficient washing process Conventional washing process Breaking strength (cN / dtex) 23.01 20.56 Elongation at break (%) 3.17 3.42 Initial modulus (cN / dtex) 723.85 623.07 Sulfuric acid concentration in water washing wastewater (wt.%) 0.01 0.26 It can be seen from Table 6 that the physical and mechanical properties of the para-aramid fiber treated with the optimal green and efficient washing process are significantly higher than those of the para-aramid fiber treated with the conventional washing process, and the sulfuric acid concentration in the washing wastewater is lower and the fiber washing effect is better.

[0057] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A green and efficient water washing equipment in the production process of para-aramid fiber, characterized in that: It includes a primary water washing box, a secondary water washing box, a tertiary water washing box and a four-roller machine which are sequentially arranged along the conveying direction of the para-aramid fiber. The primary water washing box, the secondary water washing box and the tertiary water washing box have the same structure. A pair of water washing rollers are correspondingly arranged in the upper and lower parts of the water washing box. A plurality of water pipes and spray heads are fixedly installed on the top of the water washing box. The spray heads are fixed on the bottom of the water pipes. Two water washing rollers are located below the spray heads. The bottoms of the two water washing rollers are fixed on the water washing roller bases. A vacuum suction device is arranged between the two water washing rollers. The vacuum suction device extends along the axial direction of the water washing rollers and has both ends fixed on the wall of the water washing box. A first drafting roller, a second drafting roller and a pair of squeezing rollers are sequentially arranged in the four-roller machine along the conveying direction of the para-aramid fiber.

2. The green and efficient water washing equipment in the production process of para-aramid fiber according to claim 1, characterized in that: The shells of the water washing box and the four-roller machine are both vertical rectangular blocks with a hollow interior and a missing top surface.

3. A process for high-efficiency water washing using the green and high-efficiency water washing equipment in the production process of para-aramid fiber according to claim 1 or 2, characterized in that: The process is as follows: The para-aramid fiber first bypasses the washing roller of the primary washing box, is sprayed by the spray head and then is vacuum sucked by a vacuum suction device, then bypasses the washing roller of the secondary washing box, is sprayed by the spray head and then is vacuum sucked by a vacuum suction device, then bypasses the washing roller of the tertiary washing box, is sprayed by the spray head and then is vacuum sucked by a vacuum suction device, finally reaches the four-roller machine, is stretched by the first and second stretching rollers, and then enters the squeezing roller to squeeze out the solvent that has penetrated into it.

4. The high-efficiency water washing process according to claim 3, characterized in that: The temperature of the water sprayed from the spray head is 10~90℃, the speed of the water washing roller is 50~450m / min, the tension of the water washing roller is 0.1~0.3 g / d, the vacuum suction pressure of the vacuum suction device is 20~100kPa, and the angle of the spray head is 30~150°.

5. The high-efficiency water washing process according to claim 4, characterized in that: The temperature of the water sprayed from the spray head is 30~50℃, the speed of the water washing roller is 250~350m / min, the tension of the water washing roller is 0.15~0.2g / d, the vacuum suction pressure of the vacuum suction device is 60~80kPa, and the angle of the spray head is 60~120°.

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