Crimping processing method of PBO short fiber

Abstract

The invention belongs to the field of high-performance fiber processing, and particularly provides a curling processing method of PBO short fibers, specifically, tows are softened through a softening agent to replace high-temperature steam treatment, and the produced PBO short fibers are good in flexibility. According to the scheme, under the condition that high-temperature steam is not used, the tows are softened through the softening agent, the structure of the fibers can be maintained not to be damaged, good mechanical performance is kept, short fibers with good curling performance can be obtained conveniently through subsequent low-temperature curling and cutting, the processing cost and energy consumption are greatly reduced, and the process control difficulty is also remarkably reduced; and the quality of a final product can be ensured.

Description

Technical Field

[0001] The invention belongs to the field of high-performance fiber processing, and in particular relates to a curling processing method for PBO short fibers. Background Art

[0002] In recent years, the production and application of PBO fiber in China have made great progress. In the production of PBO filaments, there will be low-grade filaments whose indicators do not meet the requirements (mechanical properties are less than or equal to 30cN / dtex). 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 that are far higher than ordinary synthetic fibers. How to digest and reasonably apply this part of the material? The successful experience abroad is: PBO staple fiber is made of PBO filament as raw material, and is curled, shaped and cut by special equipment to make short fibers with a length of tens of millimeters to several centimeters. Using the high-temperature resistance, flame retardancy, high strength, low elongation, chemical stability, acid and alkali resistance and other high performances of PBO fiber, this product can be widely used in high-temperature resistant materials such as ship engine insulation layer, ablation-resistant materials, high-temperature rollers, high-temperature filter belts, heat-resistant belts, heat-resistant shock-absorbing materials for aluminum and glass processing, and flame-retardant protective clothing, fire clothing, cable protection sleeves, racing sportswear, pilot clothing, safety gloves and other protective products. It is used to develop high-performance protective fabric materials to maximize the profit of PBO production.

[0003] The crimping process in the production of staple fibers usually uses a stuffing box type mechanical crimping. After the fibers are preheated in a steam hot box above their glass transition temperature, they are fed into the stuffing box with the help of a pair of pressure rollers. Under the action of the extrusion external force, they bend and deform to form a uniform and regular plane curl. At this time, the curling structure is generally an unstable structure, which is then stabilized through a heat setting process to become a product with a permanent curling structure. The temperature during extrusion deformation is controlled near its glass transition temperature, and the heat setting temperature is generally controlled near its cold crystallization temperature. It can be seen that when producing PBO staple fibers, the fiber undergoes a high-temperature steam process, which increases energy consumption and has a high cost. At the same time, a higher steam pressure is required, which causes a greater disturbance to the tow and affects the quality of subsequent finished products.

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

[0005] In the prior art, CN 105040128A discloses a heat treatment modification method for PBO fibers, in which the PBO fibers are passed through a tension roller into a segmented heat treatment channel, and a preheating section and a cooling section are added in the segmented heat treatment channel, so that the strength and modulus of the treated fibers are greatly increased. However, the technical solution softens the PBO molecular chain at 550°C and heat treats the fibers. This high-temperature heat treatment consumes a lot of energy and damages the fiber properties.

[0006] CN110273214A discloses a high-performance polyimide curly staple fiber and a preparation method thereof, and discloses a preparation method of a high-performance polyimide curly staple fiber, wherein the polyimide long fiber is subjected to a bunching rinse, and then enters an oiling machine through a water washing tank, and then is dried and heated by an electric heating plate, and then successively passes through a crimping machine and a cooling conveyor, and tension adjustment can be performed, and finally short-cut treatment is performed after passing through a traction tension machine, and finally a high-performance polyimide curly staple fiber is obtained. The preparation method of the present invention is used to produce polyimide curly short fibers, because the heating temperature of the electric heating plate is higher than the glass transition temperature of the fiber, the steam treatment time is short, and no high-temperature shaping treatment is required after curling, and the fiber can be cut after being cooled at room temperature. The heating temperature of the electric heating plate in this scheme is higher than the glass transition temperature of the fiber. Although curling can be achieved, the energy consumption is still high, the requirements for process control are also high, and the fiber performance is also damaged.

[0007] Therefore, whether it is possible to provide a more energy-efficient and less fiber quality-destroying PBO staple fiber curling processing method has become one of the problems to be solved urgently in this field. Summary of the invention

[0008] In view of the problems in the prior art that the staple fiber processing technology is difficult, the fiber bending cost is high and the product quality after bending is defective, the present invention provides a curling processing method for PBO staple fibers with low energy consumption and good curling property. The filament bundle is softened by a softener to replace high-temperature steam treatment. The processing cost is low and the produced PBO staple fibers have good flexibility.

[0009] The present invention softens the filament bundle by a softener without using high-temperature steam, thereby maintaining the structure of the fiber from being damaged and maintaining good mechanical properties, making it easier to subsequently curl and cut at low temperatures to obtain short fibers with good curling properties. 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 guaranteed.

[0010] The curling processing method of PBO short fibers provided by the present invention comprises the following steps: 1) After the PBO filaments are bundled, they are slightly softened to form flexible bundles; The mild softening in this step is to use a softener to soak the filament in an oil tank for oiling; the mechanical properties of the PBO filament are less than or equal to 30 cN / dtex; 2) feeding the flexible tow into a crimping machine for low-temperature crimping; the temperature of the low-temperature crimping is 20-100°C; 3) After curling, place the curled fiber in an oven and dry it at 100-200°C for 1s~100s; 4) Adjust the tension, then send it to the cutting machine for cutting and packing to obtain PBO short fibers with good curling performance.

[0011] In the step 1), the PBO filaments are completely immersed in the softener, which can form a protective film on the surface of the fiber monofilaments, improve the electrostatic effect between the monofilaments, and enhance the mobility of the monofilaments. The macroscopic manifestation is that the flexibility of the fiber is improved. The fiber bundle is softened by the softener, replacing the existing high-temperature steam softening, which reduces the cost and can also reduce the disturbance of the bundle.

[0012] If the amount of softener is too high, too much residue will easily remain on the fiber surface, which will affect the next application of the short fiber. Only a certain concentration is required to achieve the softening effect. If the amount of softener is too low, it will lead to a large electrostatic effect between the single fibers, weak mobility, and difficulty in softening.

[0013] The flexible filament bundle is composed of a plurality of PBO filaments, wherein a single PBO filament not only satisfies the single mechanical property of less than or equal to 30 cN / dtex, but also needs to meet the fineness range of 1.0 dtex to 1000 dtex. The fineness range of the finally obtained flexible filament bundle is 10 dtex to 100000 dtex.

[0014] Preferably, the mass concentration of the softener is 1-10%, and the solvent of the softener is water, and the solute is a softening oil; specifically, a certain mass of the softening oil is dissolved in water; the softening oil includes 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 alkyl benzene sulfonate, fatty acid ester or fatty acid polyoxyethylene ether, fatty alcohol polyoxyethylene polyoxypropylene ether, sorbitan monooleate, polyoxyethylene dehydrated sorbitan ester or synthetic ester, and one or more mixtures of propionic acid alcohol ester.

[0015] Preferably, in step 1) the oiling treatment by immersion in the oil tank, the immersion temperature of the oil tank is not less than 50° C., and the immersion time is 2-40 seconds. The amount of softener attached can be controlled by controlling the immersion time. The longer the time, the more softener is attached.

[0016] Preferably, in step 2), the working pressure of the crimping machine is 0.1 MPa-0.8 MPa, and the feeding speed of the crimping machine is 10-100 m / min.

[0017] Preferably, in step 4), the tension is adjusted to 0.01-10.0 cN / dtex.

[0018] The PBO staple fibers finally obtained have good curling performance, with fiber specifications of 1.0-10.0 dtex, length of 30-100 mm, oil content of 0.1-10.0%, moisture content of 0.1-10.0%, curl number of 2-40 / 25 mm, curl rate of 1.0-15%, breaking strength of 0.5-50 cN / dtex, and breaking elongation of 0.1-10.0%, which can meet the needs of subsequent industrial applications.

[0019] The curling processing method of PBO short fibers proposed in the present invention has achieved the following beneficial effects: 1. This application proposes for the first time that fibers can be softened by only using a softener without high-temperature steam, so as to facilitate subsequent bending. The fiber curling process does not include a high-temperature steam drawing process, thereby reducing production costs. By using a softener to improve the softness of the filament bundle, the fiber can be softened without the need for a high temperature, so that the filament bundle can be smoothly curled when entering the crimping machine, thereby maintaining the fiber structure from being damaged and maintaining good mechanical properties to obtain short fibers with good crimping properties.

[0020] 2. The softener used in the present application can reduce the electrostatic effect between the monofilaments, thereby enhancing the mobility of the monofilaments and improving the flexibility of the fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a short fiber sample produced by the PBO short fiber curling processing method in Example 1 of the present invention. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below in conjunction with 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 protection scope of the present invention.

[0023] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0024] The present application discloses a method for curling PBO staple fibers, comprising the following steps: Step S1: After the PBO filaments are bundled, the bundles are placed in a softener for soaking to slightly soften them to form flexible bundles; Step S2: feeding the flexible tow into a crimping machine for low temperature crimping at 20-100°C; Step S3: After curling is completed, the curled fiber is placed in an oven and dried at 100-200°C; Step S4: After adjusting the tension to 0.01-10.0 cN / dtex, the fibers are cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good curling properties.

[0025] Specifically, in the embodiments of the present application, the fiber bundles are softened by a softener, replacing the existing high-temperature steam softening, thereby reducing costs and also reducing disturbances of the bundles.

[0026] The present application provides the following embodiments and comparative examples. It should be noted that the steps in all the embodiments of the present application are performed in the order of the listed steps.

[0027] Example 1 A method for curling PBO staple fibers, the specific steps are as follows: Step S1: after bundling 20 bundles of commercially available PBO filaments with a specification of 555 dtex into a bundle of 11100 dtex, the bundle is placed in a softener aqueous solution with a mass concentration of 1% for immersion, and is completely immersed and softened at 50° C. for 5 seconds to perform slight softening to form a flexible bundle; The solute composition in the softener aqueous solution is 10% by weight of octadecyl diester quaternary ammonium salt YH-866, 20% by weight of hexadecyl potassium phosphate, 20% by weight of decaglycerol monolaurate, 30% by weight of sorbitan monooleate, and 20% by weight of propionate.

[0028] Step S2: feeding the flexible tow into a crimping machine with a working pressure of 0.1 MPa and a feeding speed of 10 m / min, and performing low-temperature crimping at 20° C.; Step S3: After curling is completed, the curled fiber is placed in an oven and dried at 100° C. for 8 seconds; Step S4: under a tension of 0.1 cN / dtex, the fibers are cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good curling properties.

[0029] The prepared PBO short fibers have good curling properties, a length of 30-50 mm, an oil content (softener) of 0.1%, a moisture content of 4.0%, a curl number of 15 / 25 mm, a curl rate of 3.5%, a breaking strength of 30 cN / dtex, and a breaking elongation of 3.0%, which can meet the needs of subsequent industrial applications. Figure 1 It can be seen that the short fibers prepared by the method have a better curling effect.

[0030] The inventors tested the tensile properties and curling properties of staple fibers in accordance with the national standards GB / T 14337-2008 "Test method for tensile properties of chemical staple fibers" and GB / T 14338-2008 "Test method for curling properties of chemical staple fibers".

[0031] Example 2 A method for curling PBO staple fibers, the specific steps are as follows: Step S1: After 40 bundles of commercially available PBO filaments with a specification of 555 dtex are bundled into a bundle of 22200 dtex, the bundle is placed in a softener aqueous solution with a mass concentration of 3% and immersed at 60° C. for 6 seconds to soften slightly and form a flexible bundle; The solute composition in the softener aqueous solution is 10% by weight of ester quaternary ammonium salt TEP-88, 30% by weight of dodecylbenzene sulfonate, 20% by weight of decaglycerol monolaurate, and 40% by weight of polyoxyethylene dehydrated sorbitan ester.

[0032] Step S2: feeding the flexible tow into a crimping machine with a working pressure of 0.2 MPa and a feeding speed of 15 m / min, and performing low-temperature crimping at 30° C.; Step S3: After curling is completed, the curled fiber is placed in an oven and dried at 110° C. for 10 seconds; Step S4: under a tension of 0.2 cN / dtex, the fibers are cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good curling properties.

[0033] The prepared PBO staple fibers have good curling properties, a length of 50-100 mm, an oil content of 0.7%, a moisture content of 3.0%, a curl number of 16 / 25 mm, a curl rate of 3.7%, a breaking strength of 29 cN / dtex, and a breaking elongation of 3.0%, which can meet the needs of subsequent industrial applications.

[0034] Example 3 A method for curling PBO staple fibers, the specific steps are as follows: Step S1: after bundling 12 bundles of commercially available PBO filaments with a specification of 555 dtex into a bundle of 6660 dtex, the bundle is placed in a softener aqueous solution with a mass concentration of 5% and immersed at 70° C. for 7 seconds to soften slightly and form a flexible bundle; The solute composition in the softener aqueous solution is 30% by weight of ester quaternary ammonium salt TEP-90, 20% potassium hexadecyl phosphate, 40% sorbitan monooleate, 5% polyoxyethylene sorbitan ester, and 5% leaf propionate.

[0035] Step S2: feeding the flexible tow into a crimping machine with a working pressure of 0.9 MPa and a feeding speed of 30 m / min, and performing low-temperature crimping at 70° C.; Step S3: After curling is completed, the curled fiber is placed in an oven and dried at 130° C. for 12 seconds; Step S4: under a tension of 0.3 cN / dtex, the fibers are cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good curling properties.

[0036] The prepared PBO staple fibers have good curling properties, with a length of 30-60 mm, an oil content of 0.7%, a moisture content of 2.0%, a curl number of 18 / 25 mm, a curl rate of 3.2%, a breaking strength of 28 cN / dtex, and a breaking elongation of 3.2%, which can meet the needs of subsequent industrial applications.

[0037] Example 4 A method for curling PBO staple fibers, the specific steps are as follows: Step S1: after bundling 4 bundles of commercially available PBO filaments with a specification of 555 dtex into a bundle of 2220 dtex, the bundle is placed in a softener aqueous solution with a mass concentration of 7% and immersed at 90° C. for 9 seconds to soften slightly and form a flexible bundle; The solute composition in the softener aqueous solution is 15% of sodium polystyrene sulfonate, 25% of dodecylbenzene sulfonate, 30% of polyoxyethylene sorbitan ester and 30% of leaf propionate by weight.

[0038] Step S2: feeding the flexible tow into a crimping machine at a feeding speed of 0.5 MPa and a feeding speed of 50 m / min, and performing low-temperature crimping at 80° C.; Step S3: After curling is completed, the curled fiber is placed in an oven and dried at 180° C. for 6 seconds; Step S4: under a tension of 0.4 cN / dtex, the fibers are cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good curling properties.

[0039] The prepared PBO staple fibers have good curling properties, with a length of 40 to 80 mm, an oil content of 1.2%, a moisture content of 3.9%, a curl number of 20 / 25 mm, a curl rate of 3.4%, a breaking strength of 27 cN / dtex, and an elongation at break of 3.5%, which can meet the needs of subsequent industrial applications.

[0040] Comparative Example A method for curling PBO staple fibers, the specific steps are as follows: Step S1: after bundling 4 bundles of commercially available PBO filaments with a specification of 555 dtex into a bundle of 2220 dtex, the bundle is preheated at a high temperature of 550° C. in a steam hot box; Step S2: feeding the flexible tow into a crimping machine with a working pressure of 0.5 MPa and a feeding speed of 50 m / min, and performing high-temperature crimping at 500° C.; Step S3: After curling is completed, the curled fiber is placed in an oven and dried at 300-400°C for 6 seconds; Step S4: under a tension of 0.4 cN / dtex, the fibers are cut by a cutting machine and packaged by a packaging machine to obtain PBO short fibers with good curling properties.

[0041] The above-mentioned PBO short fibers have good curling performance, a length of 40 to 80 mm, an oil content of 2%, a moisture content of 4%, a curl number of 18 / 25 mm, a curl rate of 3.0%, a breaking strength of 20 cN / dtex, and a breaking elongation of 3.0%.

[0042] It can be seen that the strength of the short fibers prepared by high-temperature curling in the comparative example is relatively low, with a breaking strength of 20 cN / dtex; the breaking strength of the short fibers prepared by low-temperature curling with the softener in the present application scheme is greater than 27 cN / dtex, which is much better than the scheme of the comparative example. The curling effects of the two are not much different, but the present application adopts a low-temperature process, which has a very significant reduction in energy consumption compared with the comparative example.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any equivalent substitutions, modifications, etc. made by technicians in this field without any creative work within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for curling PBO short fibers, characterized in that: The following steps are involved: 1) After the PBO filaments are bundled, they are slightly softened to form flexible bundles; Mild softening is to use a softener to soak the filament in an oil tank for oiling; the mechanical properties of the PBO filament are less than or equal to 30 cN / dtex; 2) feeding the flexible tow into a crimping machine for low-temperature crimping; the temperature of the low-temperature crimping is 20-100°C; 3) After curling, place the curled fiber in an oven and dry it at 100-200°C for 1s~100s; 4) Adjust the tension, then send it to the cutting machine for cutting and packing to obtain PBO short fibers with good curling performance.

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

3. The crimping processing method of PBO short fibers according to claim 1, characterized in that: The mass concentration of the softener is 1-10%, the solvent of the softener is water, and the solute is a softening oil; the softening oil includes 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 alkyl benzene sulfonate, fatty acid ester or fatty acid polyoxyethylene ether, fatty alcohol polyoxyethylene polyoxypropylene ether, sorbitan monooleate, polyoxyethylene dehydrated sorbitan ester or synthetic ester, and one or more mixtures of propionic acid alcohol ester.

4. The crimping processing method of PBO short fibers according to claim 1 or 3, characterized in that: Step 1) During the oiling treatment, the temperature of the oiling tank is not less than 50°C, and the soaking time is 2-40s.

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

6. The crimping processing method of PBO short fibers according to claim 1, characterized in that: Step 4) Adjust the tension to 0.01-10.0 cN / dtex.

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

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