Low-damage para-aramid crimped staple fiber and production method thereof

Abstract

The invention belongs to the technical field of fiber manufacturing, and discloses a low-damage para-aramid curled staple fiber and a production method thereof.The para-aramid fiber is treated through a staple fiber oiling agent, after the content of the staple fiber oiling agent in the para-aramid fiber reaches 0.1-0.3% wt, the para-aramid fiber is fed into a curled filling bin with the inner wall subjected to ceramic coating treatment to be curled, and the low-damage para-aramid curled staple fiber is obtained. Through short fiber oiling agent treatment and curling filling bin inner wall ceramic coating treatment, a lower friction coefficient is generated between the short fibers and the ceramic surface in the curling process, and it is guaranteed that the relative initial filament strength retention rate of the para-aramid curled short fibers is larger than or equal to 85%.

Description

Technical Field

[0001] The present invention relates to a low-damage para-aramid crimped staple fiber and a production method thereof, and particularly to a production process for preparing low-damage para-aramid crimped staple fiber and the prepared para-aramid crimped staple fiber, belonging to the technical field of fiber manufacturing. Background Art

[0002] Para-aramid fibers are high-tech materials with excellent mechanical and thermal properties, and are widely used in the fields of national defense and military industry, and optical cable rubber. The staple fibers prepared therefrom can be used in the field of protection, such as cut-resistant and heat-resistant gloves, cut-resistant and heat-resistant fabrics, and heat-resistant and high-strength sewing threads. At present, when preparing high-strength yarns or textile products, there are relatively high requirements for the strength of staple fiber filaments. However, after the para-aramid fibers are processed by the conventional crimping process, the fiber strength loss is relatively large, which greatly reduces the quality of the staple fibers. The main reason for the large strength loss is that the high-rigidity and high-crystallinity structure of para-aramid fibers is easily damaged by external force bending and abrasion. After the fibers pass through the crimping process, the key skin-core structure is physically damaged, and the cortical structure where the fibers are mainly stressed is severely damaged under mechanical pressure and friction on the surface of the filling bin, resulting in a significant decrease in the strength of the para-aramid single filaments after crimping, and the strength loss is up to more than 30%.

[0003] In the prior art, the invention patent with the publication number of CN102926068A discloses a crimping processing method for para-aramid staple fibers. In this method, the aramid filaments are bundled and then enter the mechanical stuffing type crimping box through an oil washing tank for oil washing, a hot water bath, or a low-pressure steam heat box for crimping. After crimping is completed, the fibers enter the oven, and the crimped fibers are dried at 80-140°C, and there is no need to carry out the setting treatment at a high temperature of 340°C, and then the tension can be adjusted and the fibers can enter the cutting machine to be cut to obtain para-aramid staple fibers with good crimping performance. This method only considers the energy consumption during the crimping process and the crimping performance of the fibers, and does not disclose the loss of fiber strength.

[0004] The invention patent with the publication number of CN112921651A discloses a crimping processing method for para-aramid staple fibers. In this method, the tow is placed in a softening agent composed of a softening agent and aramid oil agent, soaked to form a flexible tow, and then extruded, crimped, dried and cut to obtain para-aramid staple fibers. This method uses a softening agent added to the oil agent as a softening agent to soften the fibers, which can reduce the friction coefficient of the single filaments, enhance the moving ability of the single filaments, improve the flexibility of the fibers, and make the state of the tow easily undergo the crimping process when entering the crimper. This method crimps the fibers after softening them with a softening agent, but the softening process of the fibers may also damage the fiber structure, resulting in a decrease in the fiber strength after crimping.

[0005] The invention patent with the publication number CN113981682A discloses a pre-activated para-aramid fiber and its preparation method. In this method, the para-aramid fiber is impregnated in an activation sizing agent for pretreatment, then the fiber is dried in two stages, and finally wound to form the pre-activated para-aramid fiber. The raw materials of the activation sizing agent used include epoxy resin, phenolic resin, fatty alcohol polyoxyethylene ether, phosphate ester, glycerol oleate, and distilled water. Through the pre-activation treatment process, while ensuring the adhesion between the para-aramid fiber and the rubber matrix, the fiber itself can also maintain a high strength. This method aims to improve the problem of poor adhesion between the para-aramid fiber and the rubber matrix, and at the same time can maintain the fiber strength. Whether it can maintain a high strength of the fiber after curling remains to be verified. Summary of the Invention

[0006] The present invention aims to solve the problem of damage to para-aramid fibers in the existing crimped staple fiber technology, and provides a production method for low-damage para-aramid crimped staple fibers. Through the treatment of the staple fiber sizing agent and the ceramic coating on the inner wall of the crimping filling bin, a lower friction coefficient is generated between the staple fiber and the ceramic surface during the crimping process, so that the strength retention rate of the produced staple fiber relative to the initial filament is high. For this reason, the present invention also provides para-aramid crimped staple fibers obtained by this production method.

[0007] The present invention is realized through the following technical solutions: A production method for low-damage para-aramid crimped staple fibers, using a staple fiber sizing agent to treat para-aramid fibers. After the content of the staple fiber sizing agent in the para-aramid fibers reaches 0.1 - 0.3%wt, it is sent to a crimping filling bin with a ceramic-coated inner wall for crimping to obtain para-aramid crimped staple fibers. The staple fiber sizing agent is a mixture composed of alkyl phosphate ester, alkyl polyoxyethylene ether alkane ester, and aliphatic isooctyl ester. The mass ratio of alkyl phosphate ester : alkyl polyoxyethylene ether alkane ester : aliphatic isooctyl ester is 2 - 1 : 0.5 - 1 : 2 - 3.

[0008] The ceramic coating is alumina, zirconia, or chromium oxide.

[0009] In the crimping filling bin, the friction coefficient between the para-aramid fiber and the ceramic coating surface is ≤0.15.

[0010] The fiber strength retention rate of the para-aramid crimped staple fiber is ≥85%.

[0011] Para-aramid crimped staple fibers obtained by the above production method.

[0012] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The present invention first proposes to make a smooth ceramic coating on the metal surface in the crimping machine filling bin to reduce the wear of the fiber in the bin and thus reduce the loss of fiber strength.

[0013] (2) To further solve the problem of damage to para-aramid fibers in the existing crimped staple fiber technology, on the basis of using a smooth ceramic coating, a corresponding staple fiber oil agent is matched to further reduce the friction between the fibers and the surrounding of the bin wall to ensure maintaining a high strength retention rate.

[0014] (3) While significantly reducing the fiber strength loss through the ceramic coating and fiber oil agent, the present invention also reduces the internal wear of the crimper and the maintenance cost of the crimper. Description of the Drawings

[0015] Figure 1 It is a schematic diagram inside the crimping filling bin.

[0016] Figure 2 It is a schematic diagram of the structure of the ceramic coating on the inner wall of the crimping filling bin. Detailed Embodiments

[0017] The present invention will be further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0018] See Figure 1 and Figure 2 As shown, para-aramid filaments are crimped to prepare para-aramid crimped staple fibers.

[0019] In the following embodiments, the single-filament strength test is based on the standard GB / T 35442-2017, the fiber crimp number and crimp ratio test are based on the standard GB / T 35442-2017, and the fiber friction coefficient with the ceramic surface test is based on the standard T / CSTM 00522-2022.

[0020] Example 1: This example takes the ceramic coating + staple fiber oil agent as an example.

[0021] After the para-aramid filaments with a single-filament strength of 22.5 cN / dtex are bundled, they are softened by steam humidification at 150 °C and sprayed with a staple fiber oil agent. The oil agent is sprayed in a controlled amount, and the final staple fiber oil agent content is 0.15%. The components of the staple fiber oil agent are alkyl phosphate, alkyl polyoxyethylene ether alkane ester, and aliphatic isooctyl ester, which are MOA-3P, PEG400DL, and isooctyl stearate respectively, and their mass ratios are 1:0.5:2 in sequence.

[0022] The fibers treated with the above staple fiber oil agent are sent into the crimping filling bin. The inner wall of the crimping filling bin is treated with an alumina coating. During the crimping process, the measured friction coefficient μ 动 is 1.24, μ 静It is 1.32. After crimping, the monofilament strength is 20.7 cN / dtex, the crimp number is 8.5 per 25 mm, and the crimp percentage is 12.3%.

[0023] Example 2: This example takes ceramic coating + staple fiber oil agent as an example.

[0024] After collecting para-aramid filaments with a monofilament strength of 22.5 cN / dtex, they are softened by steam humidification at 150 °C and sprayed with staple fiber oil agent. The oil agent is sprayed with a controlled amount. The final staple fiber oil agent content of the fiber is 0.18%. The components of the staple fiber oil agent, namely alkyl phosphate, alkyl polyoxyethylene ether alkane ester, and aliphatic isooctyl ester, are MOA-3P, PEG400ML, and isooctyl stearate respectively, and their mass ratios are 1:1:3 in sequence.

[0025] The fiber treated with the above staple fiber oil agent is sent into a crimp filling bin. The inner wall of this crimp filling bin is treated with alumina coating. During the crimping process, the measured friction coefficient μ of the fiber with this alumina coating 动 is 1.21, μ 静 is 1.30. After crimping, the monofilament strength is 21.2 cN / dtex, the crimp number is 9.1 per 25 mm, and the crimp percentage is 14.7%.

[0026] Example 3: This example takes ceramic coating + staple fiber oil agent as an example.

[0027] After collecting para-aramid filaments with a monofilament strength of 22.5 cN / dtex, they are softened by steam humidification at 150 °C and sprayed with staple fiber oil agent. The oil agent is sprayed with a controlled amount. The final staple fiber oil agent content of the fiber is 0.18%. The components of the staple fiber oil agent, namely alkyl phosphate, alkyl polyoxyethylene ether alkane ester, and aliphatic isooctyl ester, are MOAPK, PEG400ML, and isooctyl palmitate respectively, and their mass ratios are 1:1:3 in sequence.

[0028] The fiber treated with the above staple fiber oil agent is sent into a crimp filling bin. The inner wall of this crimp filling bin is treated with alumina coating. During the crimping process, the measured friction coefficient μ of the fiber with this alumina coating 动 is 1.28, μ 静 is 1.35. After crimping, the monofilament strength is 20.1 cN / dtex, the crimp number is 9.5 per 25 mm, and the crimp percentage is 15.3%.

[0029] Comparative Example 1: This comparative example takes the crimping process with only ceramic coating as an example.

[0030] After the para-aramid filaments with a single-filament strength of 22.5 cN / dtex are bundled, they are softened by humidifying with 150°C steam and fed into the crimping and filling bin in an oil-free state. The inner wall of this crimping and filling bin is treated with a zirconia coating. During the crimping process, the measured friction coefficient μ of the fiber with this alumina coating 动 is 1.58, μ 静 is 1.63. After crimping, the single-filament strength is 18.1 cN / dtex, the number of crimps is 9.3 per 25 mm, and the crimp percentage is 14.8%.

[0031] Comparative Example 2: In this comparative example, the crimping process is only spraying sizing agent as an example After the para-aramid filaments with a single-filament strength of 22.5 cN / dtex are bundled, they are softened by humidifying with 150°C steam and sprayed with staple fiber sizing agent. The sizing agent is sprayed in a controlled amount, and the final content of staple fiber sizing agent in the fiber is 0.21%. The components of the staple fiber sizing agent are alkyl phosphate, alkyl polyethylene glycol ether alkane ester, and aliphatic isooctyl ester, which are MOAPK, PEG400ML, and isooctyl palmitate respectively, and their mass ratios are 1:0.5:3 in sequence.

[0032] The fibers treated with the above staple fiber sizing agent are fed into a crimping and filling bin without ceramic coating treatment. During the crimping process, the measured friction coefficient μ of the fiber with the metal base in the bin 动 is 1.67, μ 静 is 1.72. After crimping, the single-filament strength is 17.5 cN / dtex, the number of crimps is 9.5 per 25 mm, and the crimp percentage is 16.5%.

[0033] Comparative Example 3: In this comparative example, the crimping process is a conventional crimping process as an example.

[0034] After the para-aramid filaments with a single-filament strength of 22.5 cN / dtex are bundled, they are softened by humidifying with steam and sprayed with sizing agent and then enter the metal filling bin in the crimper. The sizing agent is sprayed in a controlled amount, and the final sizing agent content in the fiber is 0.15%. The sizing agent is an alkyl phosphate component of MOAPK. After the fiber is sized, the measured dynamic and static friction coefficients μ of the fiber with the metal in the bin are 1.89 and 1.95 respectively. After crimping, the single-filament strength is 16.2 cN / dtex, the number of crimps is 10.4 per 25 mm, and the crimp percentage is 17.2%.

[0035] The relevant data statistics of the above Example 1 and comparative examples are shown in Table 1 below.

[0036] Table 1 Data comparison table of examples and comparative examples As can be seen from Table 1, when the present invention is crimped in cooperation with a crimping filling bin treated with a staple fiber finish and a ceramic coating, the staple fiber strength can be higher, and the fiber strength retention rate can reach up to 94.2%; when crimping is performed using only a staple fiber finish or only a crimping filling bin treated with a ceramic coating, the staple fiber strength decreases, and the fiber strength retention rate is only about 80%; when crimping is performed using a conventional staple fiber finish and a conventional metal filling bin, the fiber wear is greater, the staple fiber strength is lower, and the quality of the staple fiber prepared from the same filament is lower.

[0037] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for producing low-damage para-aramid curly staple fibers, characterized in that: The para-aramid fiber is treated with a staple oil agent to make the staple oil agent content in the para-aramid fiber reach 0.1-0.3%wt, and then sent to a crimping filling bin with a ceramic coating on the inner wall for crimping to obtain para-aramid crimped staple fibers. The staple fiber oil agent is a mixture of alkyl phosphate, alkyl polyoxyethylene ether alkane ester and aliphatic isooctyl ester, and the mass ratio of alkyl phosphate: alkyl polyoxyethylene ether alkane ester: aliphatic isooctyl ester is 2-1: 0.5-1: 2-3.

2. The production method according to claim 1, characterized in that: The ceramic coating is aluminum oxide, zirconium oxide or chromium oxide.

3. The production method according to claim 1, characterized in that: In the crimping filling bin, the friction coefficient between the para-aramid fiber and the surface of the ceramic coating is ≤0.

15.

4. The production method according to claim 1, characterized in that: The fiber strength retention rate of the para-aramid curly staple fiber is ≥85%.

5. Para-aramid curly staple fibers obtained by the production method according to any one of claims 1 to 4.

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