A method for crimping PBO staple fibers

Abstract

The application belongs to the field of high-performance fiber processing, and specifically provides a crimping processing method for PBO short fibers. The method specifically softens the tow through a softening agent to replace high-temperature steam treatment, and the produced PBO short fibers have good flexibility. In the method, the tow is softened through the softening agent without using high-temperature steam, the structure of the fibers can be maintained without being damaged, good mechanical properties are maintained, the short fibers with good crimping performance can be obtained through subsequent low-temperature crimping and cutting, the processing cost and energy consumption are greatly reduced, the difficulty of process control is also significantly reduced, and the quality of the final product can be ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high-performance fiber processing, and particularly relates to a crimping processing method of PBO short fibers. BACKGROUND

[0002] In recent years, the production and application of PBO fibers have greatly developed in China. In the production of PBO filaments, low-grade filaments (mechanical properties less than or equal to 30 cN / dtex) that do not meet the requirements will appear. PBO is a high-performance fiber, and is expensive. Although these low-grade filaments cannot meet the requirements of high-end product applications, they still have mechanical properties and high-temperature resistance and other properties much higher than ordinary synthetic fibers. How to digest and reasonably use this part of the material, the successful experience abroad is that PBO short fibers are made of PBO filaments as raw materials, and are cut into short fibers with a length of tens of millimeters to several centimeters through special equipment crimping and setting. The product can be widely used in the fields of heat insulation layer of ship engines, ablation-resistant materials, high-temperature rollers, high-temperature filter belts, heat-resistant belts, heat-resistant damping materials for aluminum and glass processing, and other high-temperature-resistant materials and protective products such as flame-retardant protective clothing, fire-fighting clothing, cable protective sleeves, racing clothing, pilot clothing, and safety gloves, for developing high-performance protective fabric materials, and realizing the profit maximization of PBO production.

[0003] In the production of short fibers, the crimping process usually adopts a stuffing box type mechanical crimping. The fiber is preheated in a steam heat box above its glass transition temperature, and then is sent into a stuffing box by a pair of pressure rollers under the action of extrusion force, and is bent and deformed to form uniform and regular plane crimping. At this time, the crimping structure is generally unstable, and then is stabilized through a heat setting process to become a product form with permanent crimping structure. The temperature control during extrusion deformation is near the glass transition temperature, and the heat setting temperature is generally controlled near the cold crystallization temperature. It can be seen that in the production of PBO short fibers, the energy consumption increases and the cost is higher when the fiber passes through the high-temperature steam process. At the same time, a higher steam pressure is required, which greatly disturbs the fiber bundle and affects the quality of the finished product.

[0004] The softening temperature of the molecular chain of PBO fiber is generally about 550℃, and its complete crystalline structure gives it a strength higher than 37.67 cN / dtex. In this case, the process conditions of ordinary synthetic fibers cannot meet the processing requirements of PBO short fibers. Especially in the crimping process, the high-temperature preheating treatment before crimping and the high-temperature setting treatment after crimping are difficult for PBO fibers. The high-temperature preheating and high-temperature setting treatment temperature must be higher than 550℃, which causes high energy consumption and is not conducive to the energy-saving optimization of the process.

[0005] The prior art CN 105040128A discloses a heat treatment modification method of PBO fiber, the PBO fiber is passed through a tension roller into a segmented heat treatment channel, a preheating section and a cooling section are additionally arranged in the segmented heat treatment channel, so that the strength and modulus of the treated fiber are greatly increased. However, the technical scheme adopts heat treatment of the fiber at 550 DEG C to soften the PBO molecular chain, which has high energy consumption and damages the fiber performance.

[0006] CN110273214A discloses a high-performance polyimide crimped short fiber and a preparation method thereof, and discloses a preparation method of a high-performance polyimide crimped short fiber. After the polyimide long fiber is washed by bundling and washing, it is passed through a water washing tank into an oiling machine, then dried and heated by an electric heating plate, and then passed through a crimping machine and a cooling conveyor in sequence, and then tension adjustment is performed, and finally cut into short pieces after passing through a traction tension machine. Finally, a high-performance polyimide crimped short fiber is obtained. The polyimide crimped short fiber produced by the preparation method has a high heating temperature of the electric heating plate higher than the glass transition temperature of the fiber, a short steam treatment time, and does not need to be subjected to high-temperature setting treatment after crimping, but can be cut off after normal temperature cooling treatment. The heating temperature of the electric heating plate of the scheme is higher than the glass transition temperature of the fiber, although the crimping can be realized, but the energy consumption is still high, the requirement for process control is also high, and the fiber performance is also damaged.

[0007] Therefore, whether a PBO short fiber crimping processing method with lower energy consumption and less fiber quality loss can be provided has become one of the problems to be solved in the field. SUMMARY

[0008] In view of the problems of the existing short fiber processing technology, such as difficulty in processing, high cost of fiber bending, and defects in product quality after bending, the present application provides a PBO short fiber crimping processing method with low energy consumption and good crimping performance. The softener is used to soften the tow to replace high-temperature steam treatment, which has low processing cost and good flexibility of the produced PBO short fiber.

[0009] Without using high-temperature steam, the softener is used to soften the tow, which can maintain the structure of the fiber without being damaged, keep good mechanical properties, facilitate subsequent low-temperature crimping and cutting to obtain short fibers with good crimping performance, greatly reduce the processing cost and energy consumption, significantly reduce the difficulty of process control, and ensure the quality of the final product.

[0010] The PBO short fiber crimping processing method provided by the present application comprises the following steps:

[0011] 1) After the PBO long fiber is bundled, it is slightly softened to form a flexible tow;

[0012] The mild softening in the step is oil tank soaking oiling treatment with a softening agent; the mechanical property of the PBO filament is less than or equal to 30 cN / dtex;

[0013] 2) The flexible filament bundle is fed into a crimping machine for low-temperature crimping; the temperature of the low-temperature crimping is 20-100℃;

[0014] 3) After crimping, the crimped fiber is placed into an oven for drying treatment at 100-200℃ for 1s-100s;

[0015] 4) Tension adjustment is performed, and then the crimped fiber is cut by a cutting machine to obtain PBO staple fiber with good crimping performance.

[0016] The PBO filament in the step 1) is completely soaked in the softening agent, which can form a protective film on the surface of the fiber monofilament, improve the electrostatic effect between the monofilaments, and enhance the moving ability of the monofilaments, which is macroscopically reflected as the improvement of the fiber flexibility. The softening of the fiber filament bundle through the softening agent replaces the existing high-temperature steam softening, reduces the cost, and also reduces the disturbance of the filament bundle.

[0017] However, too much softening agent is easy to remain on the surface of the fiber, which affects the next step of the short fiber application. Only a certain concentration can achieve the softening effect, and if the amount of the softening agent is too low, the electrostatic effect between the monofilaments will be large, the moving ability will be weak, and it will be difficult to soften.

[0018] The flexible filament bundle is formed by a plurality of PBO filaments, wherein the single PBO filament meets the mechanical property of less than or equal to 30 cN / dtex, and also meets the fineness range of 1.0 dtex-1000 dtex, and finally the flexible filament bundle has a fineness range of 10 dtex-100000 dtex.

[0019] Preferably, the mass concentration of the softening agent is 1-10%, and the solvent of the softening agent is water, and the solute is a softening oil agent; specifically, a certain mass of softening oil agent is dissolved in water; the softening oil agent includes one or more of octadecyl bis ester quaternary ammonium salt YH-866, ester quaternary ammonium salt TEP-88, ester quaternary ammonium salt TEP-90, polystyrene sulfonic acid sodium, C6-C20 alkyl phosphate potassium salt, C8-C26 alkyl benzene sulfonic acid salt, fatty acid ester or fatty acid polyoxyethylene ether, fatty alcohol polyoxyethylene polyoxypropylene ether, sorbitol monooleate, polyoxyethylene sorbitan ester or synthetic ester, and propionic acid alcohol ester.

[0020] Preferably, in the oil tank soaking oiling treatment in the step 1), the temperature of the oil tank soaking is not less than 50℃, and the soaking time is 2-40s. The amount of the softening agent attached can be controlled by controlling the soaking time, and the more the softening agent attached, the longer the time.

[0021] Preferably, in step 2), the working pressure of the curling machine is 0.1MPa-0.8MPa, and the feeding speed of the curling machine is 10-100m / min.

[0022] Preferably, in step 4), the tension is adjusted to 0.01-10.0 cN / dtex.

[0023] The resulting PBO short fibers exhibited good crimp properties, with fiber specifications ranging from 1.0 to 10.0 dtex, lengths from 30 to 100 mm, oil content from 0.1 to 10.0%, moisture content from 0.1 to 10.0%, crimp counts from 2 to 40 per 25 mm, crimp rate from 1.0 to 15%, breaking strength from 0.5 to 50 cN / dtex, and elongation at break from 0.1 to 10.0%, meeting the requirements for subsequent industrial applications.

[0024] The crimping process for PBO short fibers proposed in this invention achieves the following beneficial effects:

[0025] 1. This application proposes for the first time that fibers can be softened using only a softening agent without the need for high-temperature steam, making them easier to bend in subsequent processes. The fiber crimping process does not include a high-temperature steam stretching process, thereby reducing production costs. By using a softening agent to improve the softness of the fiber bundle, the fibers can be softened without high temperatures, allowing the fiber bundle to smoothly undergo the crimping process when entering the crimping machine, maintaining the fiber structure without damage, and preserving good mechanical properties to obtain short fibers with good crimping performance.

[0026] 2. The softener used in this application can reduce the electrostatic effect between monofilaments, thereby enhancing the mobility of the monofilaments and improving the softness of the fiber. Attached Figure Description

[0027] Figure 1 This is a short fiber sample produced by the PBO short fiber crimping processing method in Example 1 of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to specific embodiments. These embodiments are only used to illustrate the technical solution of the present invention in more detail and should not be construed as limiting the scope of protection of the present invention.

[0029] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0030] This application discloses a method for crimping PBO short fibers, including the following steps:

[0031] Step S1: After bundling the PBO filaments, soak the bundles in a softening agent to soften them slightly and form flexible bundles.

[0032] Step S2: Feed the flexible filament bundle into the crimping machine and crimp it at a low temperature of 20-100℃;

[0033] Step S3: After crimping, place the crimped fibers into an oven and dry them at 100-200℃.

[0034] Step S4: After adjusting the tension to 0.01-10.0 cN / dtex, the fiber is cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good crimping properties.

[0035] Specifically, in this embodiment, the fiber bundles are softened with a softening agent instead of the existing high-temperature steam softening, which reduces costs and also reduces the disturbance of the fiber bundles.

[0036] This application provides the following embodiments and comparative examples. It should be noted that the steps in all embodiments of this application are performed in the order listed.

[0037] Example 1: A method for crimping PBO short fibers, the specific steps of which are as follows:

[0038] Step S1: Bundle 20 bundles of commercially available 555dtex PBO filaments into a 11100dtex filament bundle, then soak the filament bundle in a 1% softening agent aqueous solution at 50°C for 5 seconds to ensure complete immersion and softening, thus forming a flexible filament bundle.

[0039] The solute composition of the softener aqueous solution is as follows by weight percentage: 10% octadecyl diester quaternary ammonium salt YH-866, 20% potassium hexadecyl phosphate, 20% decaglycerol monolaurate, 30% sorbitan monooleate, and 20% propionic acid ester.

[0040] Step S2: Feed the flexible filament bundle into the crimping machine at a working pressure of 0.1 MPa and a feeding speed of 10 m / min. Perform low-temperature crimping at 20°C.

[0041] Step S3: After curling, place the curled fibers into an oven and dry them at 100°C for 8 seconds.

[0042] Step S4: Under a tension of 0.1 cN / dtex, the fiber is cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good crimping properties.

[0043] The prepared PBO short fibers exhibited good crimp properties, with a length of 30–50 mm, an oil content (softener) of 0.1%, a moisture content of 4.0%, a crimp count of 15 crimps / 25 mm, a crimp rate of 3.5%, a breaking strength of 30 cN / dtex, and a breaking elongation of 3.0%, meeting the requirements for subsequent industrial applications. Figure 1 It is evident that the short fibers prepared using this method have a good crimping effect.

[0044] The inventors tested the tensile and crimp properties of short fibers in accordance with the national standards GB / T 14337-2008 "Test Method for Tensile Properties of Chemical Fiber Short Fibers" and GB / T 14338-2008 "Test Method for Crimping Properties of Chemical Fiber Short Fibers".

[0045] Example 2: A method for crimping PBO short fibers, the specific steps of which are as follows:

[0046] Step S1: Bundle 40 bundles of commercially available 555dtex PBO filaments into a 22200dtex filament bundle, then soak the filament bundle in a 3% softening agent aqueous solution at 60°C for 6 seconds to soften it slightly and form a flexible filament bundle.

[0047] The solute composition of the softener aqueous solution is 10% by weight of ester-based quaternary ammonium salt TEP-88, 30% of dodecylbenzene sulfonate, 20% of decaglycerol monolaurate, and 40% of polyoxyethylene dehydrated sorbitol ester.

[0048] Step S2: Feed the flexible filament bundle into the crimping machine at a working pressure of 0.2 MPa and a feeding speed of 15 m / min, and perform low-temperature crimping at 30°C.

[0049] Step S3: After curling, place the curled fibers into an oven and dry them at 110°C for 10 seconds.

[0050] Step S4: Under a tension of 0.2 cN / dtex, the fiber is cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good crimping properties.

[0051] The prepared PBO short fibers have good crimp properties, with a length of 50-100 mm, an oil content of 0.7%, a water content of 3.0%, a crimp count of 16 / 25 mm, a crimp rate of 3.7%, a breaking strength of 29 cN / dtex, and a breaking elongation of 3.0%, which can meet the requirements of subsequent industrial applications.

[0052] Example 3: A method for crimping PBO short fibers, the specific steps of which are as follows:

[0053] Step S1: Bundle 12 bundles of commercially available 555dtex PBO filaments into a 6660dtex filament bundle, then soak the filament bundle in a 5% softening agent aqueous solution at 70°C for 7 seconds to soften it slightly and form a flexible filament bundle.

[0054] The solute composition of the softener aqueous solution by weight percentage is 30% ester-based quaternary ammonium salt TEP-90, 20% potassium hexadecyl phosphate, 40% sorbitan monooleate, 5% polyoxyethylene dehydrated sorbitan ester, and 5% propionic acid leaf ester.

[0055] Step S2: Feed the flexible filament bundle into the crimping machine at a working pressure of 0.9 MPa and a feeding speed of 30 m / min, and perform low-temperature crimping at 70°C.

[0056] Step S3: After curling, place the curled fibers into an oven and dry them at 130°C for 12 seconds.

[0057] Step S4: Under a tension of 0.3 cN / dtex, the fiber is cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good crimping properties.

[0058] The prepared PBO short fibers exhibit good crimp properties, with a length of 30–60 mm, an oil content of 0.7%, a water content of 2.0%, a crimp count of 18 / 25 mm, a crimp rate of 3.2%, a breaking strength of 28 cN / dtex, and a breaking elongation of 3.2%, which can meet the requirements of subsequent industrial applications.

[0059] Example 4: A method for crimping PBO short fibers, the specific steps of which are as follows:

[0060] Step S1: After bundling four commercially available 555dtex PBO filaments into a 2220dtex filament bundle, the filament bundle is immersed in a 7% softening agent aqueous solution at 90°C for 9 seconds to soften it slightly and form a flexible filament bundle.

[0061] The solute composition of the softener aqueous solution is 15% sodium polystyrene sulfonate, 25% dodecylbenzene sulfonate, 30% polyoxyethylene dehydrosorbitan ester, and 30% propionate leaf ester by weight percentage.

[0062] Step S2: Feed the flexible filament bundle into the crimping machine at a feeding speed of 0.5 MPa and a crimping machine feeding speed of 50 m / min, and perform low-temperature crimping at 80°C.

[0063] Step S3: After curling, place the curled fibers into an oven and dry them at 180°C for 6 seconds.

[0064] Step S4: Under a tension of 0.4 cN / dtex, the fiber is cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good crimping properties.

[0065] The prepared PBO short fibers have good crimp properties, with a length of 40-80 mm, an oil content of 1.2%, a water content of 3.9%, a crimp count of 20 / 25 mm, a crimp rate of 3.4%, a breaking strength of 27 cN / dtex, and a breaking elongation of 3.5%, which can meet the requirements of subsequent industrial applications.

[0066] A comparative example of a crimping processing method for PBO short fibers, the specific steps of which are as follows:

[0067] Step S1: After bundling 4 bundles of commercially available 555dtex PBO filaments into a 2220dtex filament bundle, the filament bundle is preheated at 550℃ in a steam heating box.

[0068] Step S2: Feed the flexible filament bundle into the crimping machine at a working pressure of 0.5 MPa and a feeding speed of 50 m / min, and perform high-temperature crimping at 500°C.

[0069] Step S3: After curling, place the curled fibers into an oven and dry them at 300~400℃ for 6 seconds;

[0070] Step S4: Under a tension of 0.4 cN / dtex, the fiber is cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good crimping properties.

[0071] The above-mentioned PBO short fibers have good crimp properties, with a length of 40-80 mm, an oil content of 2%, a water content of 4%, a crimp count of 18 / 25 mm, a crimp rate of 3.0%, a breaking strength of 20 cN / dtex, and a breaking elongation of 3.0%.

[0072] It can be seen that the short fibers prepared by high-temperature crimping in the comparative example have lower strength, with a breaking strength of 20 cN / dtex. The short fibers prepared by low-temperature crimping using the softener in this application have a breaking strength greater than 27 cN / dtex, which is far superior to the comparative example. The crimping effects of the two are not much different, but this application uses a low-temperature process, which significantly reduces energy consumption compared to the comparative example.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any equivalent substitutions or modifications made by those skilled in the art within the spirit and principle of the present invention without any creative effort should be included within the protection scope of the present invention.

Claims

1. A method for crimping PBO short fibers, characterized in that, Includes the following steps: 1) After bundling the PBO filaments, they are lightly softened to form flexible filament bundles; Mild softening involves immersing the PBO filament in an oil bath using a softening agent; the mechanical properties of the PBO filament are less than or equal to 30 cN / dtex. The softener has a mass concentration of 1-10%, the solvent of the softener is water, and the solute is a softening oil agent; the softening oil agent includes one or more of the following: octadecyl diester quaternary ammonium salt YH-866, ester quaternary ammonium salt TEP-88, ester quaternary ammonium salt TEP-90, sodium polystyrene sulfonate, C6-C20 alkyl phosphate potassium salt, C8-C26 alkylbenzene sulfonate, fatty acid ester or fatty acid polyoxyethylene ether, fatty alcohol polyoxyethylene polyoxypropylene ether, sorbitan monooleate, polyoxyethylene dehydrated sorbitan ester, and propionic acid ester. 2) The flexible filament bundle is fed into a crimping machine for low-temperature crimping; the low-temperature crimping temperature is 20-100℃; 3) After the curling is completed, place the curled fibers into an oven and dry them at 100-200℃ for 1 to 100 seconds; 4) After tension adjustment, the fiber is cut by a cutting machine and packaged to obtain PBO short fibers with good crimping properties.

2. The crimping processing method for PBO short fibers according to claim 1, characterized in that, The fineness range of a single PBO filament is 1.0 dtex to 1000 dtex, and the fineness range of the final obtained flexible filament bundle is 10 dtex to 100000 dtex.

3. The crimping processing method for PBO short fibers according to claim 1, characterized in that, Step 1) During the oil soaking process, the temperature of the oil soaking tank should not be less than 50℃, and the soaking time should be 2-40s.

4. The crimping processing method for PBO short fibers according to claim 1, characterized in that, In step 2), the working pressure of the curling machine is 0.1MPa-0.8MPa, and the feeding speed of the curling machine is 10-100m / min.

5. The crimping processing method for PBO short fibers according to claim 1, characterized in that, In step 4), the tension is adjusted to 0.01-10.0 cN / dtex.

6. The crimping processing method for PBO short fibers according to claim 1, characterized in that, The final PBO short fiber specifications are 1.0-10.0 dtex, length 30-100 mm, oil content 0.1-10.0%, moisture content 0.1-10.0%, crimp number 2-40 / 25 mm, crimp rate 1.0-15%, breaking strength 0.5-50 cN / dtex, and breaking elongation 0.1-10.0%.

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