Environment-friendly hygroscopic sizing agent for aramid fiber as well as preparation method and application of environment-friendly hygroscopic sizing agent

Abstract

The invention discloses an environment-friendly hygroscopic sizing agent for aramid fiber as well as a preparation method and application thereof, and the preparation method of the environment-friendly hygroscopic sizing agent for aramid fiber comprises the following steps: reacting polyvinyl alcohol with a solvent to obtain an intermediate containing unsaturated double bonds; slowly dropwise adding a sodium hydroxide aqueous solution into an acrylic monomer for reaction to obtain an acrylic acid neutralized solution; the preparation method comprises the following steps: slowly dropwise adding acrylate and an intermediate containing unsaturated double bonds into an acrylic acid neutralization solution, uniformly mixing to obtain a mixed solution, then slowly dropwise adding a free radical initiator aqueous solution into the mixed solution, and reacting in a protective gas atmosphere to obtain a polyacrylic acid polymer solution; and slowly adding the cross-linking agent into the polyacrylic acid polymer solution, and uniformly mixing to obtain the environment-friendly hygroscopic sizing agent for the aramid fiber. The environment-friendly hygroscopic sizing agent for the aramid fibers has an excellent hygroscopic application effect, can solve the problem of moisture absorption caused by exposure of the aramid fibers in air, and is low in cost, environment-friendly and pollution-free.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sizing agent, and particularly relates to an environmentally friendly hygroscopic sizing agent for aramid fiber and a preparation method and application thereof. BACKGROUND

[0002] Poly-p-phenyleneterephthalamide (PPTA) fiber, also known as aramid fiber, has the advantages of ultrahigh strength, high modulus, light weight, high temperature resistance and corrosion resistance, and has become one of the high-performance materials in many fields of military and civilian industries. Since the molecules of aramid fiber are linear structures of aromatic rings connected by amide bonds, they present a linear rigid structure of a large conjugated benzene ring that is difficult to rotate, so this molecular structure endows it with excellent mechanical properties, but also has high hygroscopicity, so it is necessary to perform sizing on the surface of the fiber to prevent hygroscopicity.

[0003] At present, the polymer sizing agent for preventing aramid fiber from absorbing moisture is usually polyurethane type, silicone type, phosphate type, etc., but due to the preparation process or subsequent fiber desizing application process of polyurethane type, silicone type and phosphate type sizing agent, toxic organic tin catalyst, organic silicon and organic phosphorus compounds are left, which will cause serious pollution of waste water, waste gas and waste residue. Therefore, it is urgent to develop an environmentally friendly polymer sizing agent for preventing aramid fiber from absorbing moisture. SUMMARY

[0004] In order to solve the problems raised in the background art, the purpose of the present application is to provide an environmentally friendly hygroscopic sizing agent for aramid fiber and a preparation method and application thereof. The environmentally friendly hygroscopic sizing agent for aramid fiber can effectively prevent the aramid fiber from absorbing moisture, and can meet the requirement of excellent adhesion of the interface of the aramid fiber on the basis of ensuring the strong hygroscopicity of the sizing agent, and can solve the problem of moisture absorption of aramid fiber caused by exposure to air. It is fast drying, simple sizing, simple preparation method, low cost and pollution-free.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: on the one hand, the present application provides a preparation method of an environmentally friendly hygroscopic sizing agent for aramid fiber, comprising the following steps:

[0006] (1) reacting polyvinyl alcohol and a solvent at 75-95 DEG C for 1-2 h to obtain an intermediate containing unsaturated double bonds;

[0007] (2) slowly adding sodium hydroxide aqueous solution to the acrylic acid monomer, and reacting at 0-25 DEG C for 0.5-2 h to obtain an acrylic acid neutralization solution;

[0008] (3) Slowly add acrylate and the intermediate containing unsaturated double bonds prepared in step (1) to the acrylic acid neutralization solution prepared in step (2) and mix them evenly to obtain a mixture. Then slowly add free radical initiator aqueous solution to the mixture and react for 0.5h-3h under a protective gas atmosphere at 65℃-90℃ to obtain polyacrylic acid polymer solution.

[0009] (4) Slowly add the crosslinking agent to the polyacrylic acid polymer solution and mix evenly to obtain an environmentally friendly hygroscopic sizing agent for aramid fibers.

[0010] The method involves first mixing an intermediate containing unsaturated double bonds, an acrylic acid neutralizing solution, and an acrylate to form a mixture, and then adding an aqueous solution of a free radical initiator to the mixture for polymerization. This method can prevent the acrylic acid from undergoing explosive polymerization due to uneven stirring after heating, thus ensuring controllable polymerization and producing a sizing agent with high stability and adhesion.

[0011] Furthermore, the degree of polymerization of the polyvinyl alcohol described in step (1) is 1700, and the degree of alcoholysis is 78%-99%;

[0012] The solvent used in step (1) is selected from at least one of deionized water, glycerol, methanol and ethanol, preferably deionized water;

[0013] The mass ratio of polyvinyl alcohol to solvent in step (1) is (0.07~0.1):1.

[0014] Further, the acrylic monomer mentioned in step (2) is selected from acrylic acid, or a combination of acrylic acid and methacrylic acid; when the acrylic monomer is a combination of acrylic acid and methacrylic acid, the mass ratio of acrylic acid to methacrylic acid is (80-95):(5-20);

[0015] The mass ratio of acrylic acid monomer to sodium hydroxide in the sodium hydroxide aqueous solution in step (2) is (1.8~2.65):1;

[0016] The degree of neutralization of the acrylic acid neutralizing solution in step (2) is 70%-100%.

[0017] Further, the mass ratio of the acrylate in step (3) to the acrylic monomer in step (2) is (0.15~0.5):1;

[0018] The intermediate containing unsaturated double bonds in step (3) accounts for 3-15% of the mass fraction of the acrylic monomer in step (2);

[0019] The free radical initiator in the aqueous solution of the free radical initiator in step (3) accounts for 0.3-0.5% of the mass fraction of the acrylic monomer in step (2);

[0020] In step (3), the mass ratio of free radical initiator to water in the free radical initiator aqueous solution is (0.035–0.09):10;

[0021] The protective gas atmosphere mentioned in step (3) includes nitrogen, argon, etc.

[0022] Further, the acrylate in step (3) is selected from at least one of polyethylene glycol dimethacrylate, polyethylene glycol diacrylate (PEGDA), and poly(propylene glycol) dimethacrylate; preferably, the molecular weight of the polyethylene glycol dimethacrylate is 400-1000, the molecular weight of the polyethylene glycol diacrylate is 400-1000, and the molecular weight of the poly(propylene glycol) dimethacrylate is 400-800, which is beneficial for preparing an environmentally friendly hygroscopic sizing agent for aramid fibers with relatively stable interfacial adhesion and strong water absorption;

[0023] The free radical initiator mentioned in step (3) is selected from at least one of ammonium persulfate, potassium persulfate, azobisisobutyronitrile, and benzoyl peroxide.

[0024] Further, the crosslinking agent in step (4) is selected from at least one of glycidyl methacrylate, N,N'-methylenebisacrylamide, trimethylolpropane trimethacrylate, and 1,4-butanediol dimethacrylate;

[0025] The crosslinking agent in step (4) accounts for 0.5-1.0% of the mass fraction of the acrylic monomer in step (2).

[0026] On the other hand, the present invention provides an environmentally friendly hygroscopic sizing agent for aramid fibers, which is prepared by any of the above-described methods for preparing environmentally friendly hygroscopic sizing agents for aramid fibers.

[0027] On the other hand, the present invention provides the application of the above-described environmentally friendly hygroscopic sizing agent for aramid fibers in preventing moisture absorption on the surface of aramid fibers.

[0028] Furthermore, the present invention provides a method for using the aforementioned environmentally friendly hygroscopic sizing agent for aramid fibers, comprising the following steps:

[0029] (1) The aramid fiber described above is uniformly sprayed onto the surface of the aramid fiber or fabric with an environmentally friendly hygroscopic sizing agent to form a dense sizing film.

[0030] (2) The sizing aramid fibers or fabrics can be dried by heating.

[0031] Heating and drying are used to perform thermal cross-linking during drying, thereby enhancing the adhesion of the slurry.

[0032] Furthermore, the drying temperature is 80℃~120℃, and the drying time is 1h~2h.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention uses acrylic acid as the matrix raw material and polymerizes it with polyvinyl alcohol intermediate containing unsaturated double bonds to improve the water absorption efficiency of acrylic acid. At the same time, it uses acrylate as an auxiliary material to copolymerize with acrylic acid block copolymer, which effectively improves the adhesion of the sizing agent. Finally, a crosslinking agent containing epoxy or multifunctional groups is mixed evenly with it, which can prevent excessive crosslinking during the polymerization process and cause explosive polymerization, and can also cause thermal crosslinking during the drying process after sizing, thereby improving the adhesion and water absorption of the sizing film to the fiber surface.

[0035] The environmentally friendly hygroscopic sizing agent for aramid fibers of this invention contains polyacrylic acid block acrylate and vinyl alcohol units, which can form a dense cross-linked network structure with acrylic acid molecules. The numerous hydrogen bond sites in the system can enhance the interaction between molecular chains, enabling the sizing fiber to meet a water absorption rate several times the weight of the sizing amount. Furthermore, the hydrogen bonds can effectively trap a large number of water molecules within the cross-linked network structure, thereby preventing moisture absorption caused by water molecules contacting the surface of the aramid fiber.

[0036] The environmentally friendly hygroscopic sizing agent for aramid fibers of this invention has a significant and superior hygroscopic effect, and dries quickly, is easy to sizing, has a simple preparation method, is low in cost, and is environmentally friendly and pollution-free. Using the environmentally friendly hygroscopic sizing agent for aramid fibers to treat the surface of aramid fibers to form a polymer film can prevent the aramid fibers from absorbing moisture when exposed to the environment. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a diagram of the cross-linked network structure of aramid fibers after sizing with the environmentally friendly hygroscopic sizing agent of this invention;

[0039] Figure 2 This is the Fourier transform infrared spectrum of the environmentally friendly hygroscopic sizing agent for aramid fibers prepared in Example 1 of this invention;

[0040] Figure 3In this image, 'a' is a scanning electron microscope image of the environmentally friendly hygroscopic sizing agent for aramid fibers prepared in Example 1 of this invention. Figure 3 b in the figure is a scanning electron microscope image of the environmentally friendly hygroscopic sizing agent for aramid fibers prepared in Comparative Example 1 of this invention;

[0041] Figure 4 In this paper, 'a' is a photograph of the resin block after the aramid fibers prepared in Example 1 of this invention have been dried with an environmentally friendly hygroscopic sizing agent. Figure 4 In Figure b, there is a photograph of the resin block after the aramid fiber prepared in Comparative Example 1 of this invention has been dried with an environmentally friendly hygroscopic sizing agent. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0043] Example 1

[0044] Preparation of environmentally friendly hygroscopic sizing agent for aramid fibers: (1) 8g of polyvinyl alcohol-1799 type (1799 type means: degree of polymerization of 1700, degree of alcoholysis of 99%) and 95g of deionized water were reacted at 90℃ for 2h to obtain an intermediate containing unsaturated double bonds;

[0045] (2) Dissolve 11g of sodium hydroxide solid in 40g of deionized water to obtain sodium hydroxide aqueous solution. Slowly add sodium hydroxide aqueous solution to 20g of acrylic acid AA and react in a cold water bath for 1.5h. Ensure that sodium hydroxide aqueous solution is added dropwise for at least 1h while the reaction is proceeding to obtain acrylic acid neutralized solution.

[0046] (3) Dissolve 0.073g of potassium persulfate solid in 10g of deionized water to obtain an aqueous solution of free radical initiator. Slowly add 6.5g of polyethylene glycol diacrylate (PEGDA) with a molecular weight of 400 and 1.3g of an intermediate containing unsaturated double bonds to the acrylic acid neutralization solution and mix them evenly to obtain a mixed solution. Ensure that the addition and mixing time is at least 0.5h. Then slowly add the aqueous solution of free radical initiator to the mixed solution and react at 75℃ under a nitrogen atmosphere for 2h. Ensure that the aqueous solution of free radical initiator is added dropwise at the same time as the reaction proceeds for at least 1.5h to obtain a polyacrylic acid polymer solution.

[0047] (4) After cooling the polyacrylic acid polymer solution to room temperature, slowly add 0.13g of N,N'-methylenebisacrylamide and mix evenly to obtain an environmentally friendly hygroscopic sizing agent for aramid fibers.

[0048] Example 2

[0049] Preparation of environmentally friendly hygroscopic sizing agent for aramid fibers: (1) 8g of polyvinyl alcohol type 1799 (1799 means: degree of polymerization of 1700 and degree of alcoholysis of 99%) and 90g of deionized water were reacted at 90℃ for 2h to obtain an intermediate containing unsaturated double bonds;

[0050] (2) Dissolve 8.18g of sodium hydroxide solid in 45g of deionized water to obtain sodium hydroxide aqueous solution. Slowly add sodium hydroxide aqueous solution to a mixture of 20g of acrylic acid and 1.26g of methacrylic acid. React in a cold water bath for 1h. Ensure that sodium hydroxide aqueous solution is added dropwise for at least 0.5h while the reaction is proceeding to obtain acrylic acid neutralized solution.

[0051] (3) Dissolve 0.08g of ammonium persulfate solid in 9g of deionized water to obtain an aqueous solution of free radical initiator. Slowly add 3.3g of polyethylene glycol diacrylate with a molecular weight of 400 and 1.48g of an intermediate containing unsaturated double bonds to the acrylic acid neutralization solution and mix evenly to obtain a mixed solution. Ensure that the addition and mixing time is at least 0.5h. Then slowly add the aqueous solution of free radical initiator to the mixed solution and react at 85℃ under a nitrogen atmosphere for 0.5h. Ensure that the aqueous solution of free radical initiator is added dropwise at the same time as the reaction proceeds for at least 0.5h to obtain a polyacrylic acid polymer solution.

[0052] (4) After cooling the polyacrylic acid polymer solution to room temperature, slowly add 0.21g of N,N'-methylenebisacrylamide and mix evenly to obtain an environmentally friendly hygroscopic sizing agent for aramid fibers.

[0053] Example 3

[0054] Preparation of environmentally friendly hygroscopic sizing agent for aramid fibers: (1) 8g of polyvinyl alcohol type 1795 (1795 means: degree of polymerization of 1700 and degree of alcoholysis of 95%) and 92g of deionized water were reacted at 90℃ for 2h to obtain an intermediate containing unsaturated double bonds.

[0055] (2) Dissolve 5.5g of sodium hydroxide solid in 20g of deionized water to obtain sodium hydroxide aqueous solution. Slowly add sodium hydroxide aqueous solution to 10g of acrylic acid and react in a cold water bath for 0.8h. Ensure that sodium hydroxide aqueous solution is added dropwise for at least 0.5h while the reaction is proceeding to obtain acrylic acid neutralized solution.

[0056] (3) Dissolve 0.05g of potassium persulfate solid in 10g of deionized water to obtain an aqueous solution of free radical initiator. Slowly add 3.3g of poly(propylene glycol) dimethacrylate with a molecular weight of 560 and 1.5g of an intermediate containing unsaturated double bonds to the acrylic acid neutralization solution and mix them evenly to obtain a mixed solution. Ensure that the addition and mixing time is at least 0.5h. Then slowly add the aqueous solution of free radical initiator to the mixed solution and react at 85℃ under a nitrogen atmosphere for 2h. Ensure that the aqueous solution of free radical initiator is added dropwise at the same time as the reaction proceeds for at least 1.5h to obtain a polyacrylic acid polymer solution.

[0057] (4) After cooling the polyacrylic acid polymer solution to room temperature, slowly add 0.19g of glycidyl methacrylate and mix evenly to obtain an environmentally friendly hygroscopic sizing agent for aramid fibers.

[0058] Comparative Example 1

[0059] This comparative example provides an environmentally friendly hygroscopic sizing agent for aramid fibers, which differs from Example 1 in that acrylic acid is replaced with methacrylic acid.

[0060] Comparative Example 2

[0061] This comparative example provides an environmentally friendly hygroscopic sizing agent for aramid fibers, which differs from Example 2 in that acrylic acid is replaced with methacrylic acid, and methacrylic acid is replaced with acrylic acid.

[0062] The cross-linked network structure of aramid fibers after sizing with an environmentally friendly hygroscopic sizing agent is shown in the figure below. Figure 1 As shown, from Figure 1 As can be seen, by constructing a network structure with polyacrylic acid chains as the main component and vinyl alcohol blocks and crosslinking agent branches as auxiliary components through sizing, a more uniform and dense molecular structure is covered on the fiber surface at the microscopic level, which endows it with excellent adhesion properties.

[0063] The Fourier transform infrared spectrum of the aramid fiber prepared in Example 1 using the environmentally friendly hygroscopic sizing agent is shown below. Figure 2 As shown, from Figure 2 It can be seen that it is located at 3417cm -1 2813cm -1 1637cm -1 1347cm -1 and 1114cm -1 The stretching vibration peaks corresponding to the -OH, -O-CH2-O, C=CC=C, -C-COO- and -COC- groups, respectively, demonstrate the successful synthesis of an environmentally friendly hygroscopic sizing agent for aramid fibers.

[0064] Scanning electron microscope images of the environmentally friendly hygroscopic sizing agent for aramid fibers prepared in Example 1 and the environmentally friendly hygroscopic sizing agent for aramid fibers prepared in Comparative Example 1 are shown below. Figure 3 As shown, from Figure 3 As can be seen from 'a', a uniform and dense sizing layer was observed on the fiber surface, indicating that the environmentally friendly hygroscopic sizing agent for aramid fibers prepared in Example 1 exhibits excellent interfacial adhesion; from Figure 3 As can be seen from b, the sizing layer on the fiber surface is unevenly distributed and shows clumping after sizing, indicating that the interfacial adhesion of the sizing agent in Comparative Example 1 is not ideal and its adhesion to the fiber does not meet the requirements. Through a direct comparison of different sized fiber samples, it is shown that the environmentally friendly hygroscopic sizing agent for aramid fibers prepared in the embodiments of this invention has excellent interfacial adhesion.

[0065] The performance of the environmentally friendly hygroscopic sizing agents for aramid fibers provided in Examples 1-3 and Comparative Examples 1-2 was characterized by the following method: 20g of the environmentally friendly hygroscopic sizing agent for aramid fibers was placed in a beaker and dried at 120℃ for 2 hours. The water absorption rate of the dried aramid fibers to 50mL was then tested. The results are shown in Table 1. Photos of the resin blocks after drying of the sizing agents from Examples 1 and Comparative Examples 1 are shown below. Figure 4 As shown.

[0066] Table 1. Characterization results of water absorption performance of Examples 1-3 and Comparative Examples 1-2

[0067]

[0068] As shown in Table 1, the environmentally friendly hygroscopic sizing agents for aramid fibers provided in Examples 1-3 have relatively rapid and strong hygroscopic properties.

[0069] from Figure 4 It can be seen that in Comparative Example 1, after replacing acrylic acid with methacrylic acid, the dried slurry contained more fragmented resin, and due to the weak cross-linking degree, the resin became more brittle and difficult to adhere to the fibers, thus affecting the moisture absorption performance of the fibers after sizing. The above results indicate that the present invention uses acrylic acid as the main monomer for polymerization, combined with polyvinyl alcohol monomer for synergistic effect, and with an appropriate weight of excipients, which can enhance the moisture absorption of the sizing agent while also taking into account its adhesion.

[0070] 10g of aramid fiber was sprayed with an environmentally friendly hygroscopic sizing agent provided in Examples 1-3 and Comparative Examples 1-2, which account for approximately 10wt% of the fiber weight. After sizing, the fiber was dried. The sized aramid fiber was then placed in 100mL of deionized water for 1min. The sized aramid fiber was then removed and weighed. The hygroscopic properties of the sized fiber were compared, and the results are shown in Table 2.

[0071] Table 2. Performance Tests of Sizing Fibers

[0072]

[0073] As shown in Table 2, the environmentally friendly hygroscopic sizing agents for aramid fibers provided in Examples 1-3 significantly improved the hygroscopic properties of the fibers. However, the improvement in hygroscopic properties was relatively small when the environmentally friendly hygroscopic sizing agents for aramid fibers provided in Comparative Examples 1-2 were applied. This is because the environmentally friendly hygroscopic sizing agents for aramid fibers provided in Comparative Examples 1-2 pulverized on the fiber surface, resulting in poor interfacial adhesion and difficulty in constructing a uniform polyacrylic acid water-absorbing film on the fiber surface. Therefore, the hygroscopic properties were close to those of the original fibers. These results indicate that the environmentally friendly hygroscopic sizing agent for aramid fibers prepared by the present invention using acrylic acid as the main monomer and synergistic polymerization with excipients can significantly prevent the aramid fiber surface from contacting air moisture. While ensuring excellent interfacial adhesion after sizing, it can meet the requirements of the sizing agent for hygroscopic and water-blocking properties of aramid fibers.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing an environmentally friendly hygroscopic sizing agent for aramid fibers, characterized in that, Includes the following steps: (1) Polyvinyl alcohol and solvent are reacted at 75℃-95℃ for 1h-2h to obtain an intermediate containing unsaturated double bonds; (2) Add sodium hydroxide aqueous solution dropwise to acrylic acid monomer and react at 0℃-25℃ for 0.5h-2h to obtain acrylic acid neutralized solution; (3) Slowly add acrylate and the intermediate containing unsaturated double bonds prepared in step (1) to the acrylic acid neutralization solution prepared in step (2) and mix them evenly to obtain a mixture. Then slowly add free radical initiator aqueous solution to the mixture and react for 0.5h-3h under a protective gas atmosphere at 65℃-90℃ to obtain polyacrylic acid polymer solution. (4) Slowly add the crosslinking agent to the polyacrylic acid polymer solution and mix evenly to obtain an environmentally friendly hygroscopic sizing agent for aramid fibers.

2. The method for preparing the environmentally friendly hygroscopic sizing agent for aramid fibers according to claim 1, characterized in that, The degree of polymerization of the polyvinyl alcohol mentioned in step (1) is 1700, and the degree of alcoholysis is 78%-99%; The solvent used in step (1) is selected from at least one of deionized water, glycerol, methanol and ethanol, preferably deionized water; The mass ratio of polyvinyl alcohol to solvent in step (1) is (0.07~0.1):

1.

3. The method for preparing the environmentally friendly hygroscopic sizing agent for aramid fibers according to claim 1, characterized in that, The acrylic monomer mentioned in step (2) is selected from acrylic acid, or a combination of acrylic acid and methacrylic acid; when the acrylic monomer is a combination of acrylic acid and methacrylic acid, the mass ratio of acrylic acid to methacrylic acid is (80-95):(5-20); The mass ratio of acrylic acid monomer to sodium hydroxide in the sodium hydroxide aqueous solution in step (2) is (1.8~2.65):1; The degree of neutralization of the acrylic acid neutralizing solution in step (2) is 70%-100%.

4. The method for preparing the environmentally friendly hygroscopic sizing agent for aramid fibers according to claim 1, characterized in that, The mass ratio of the acrylate in step (3) to the acrylic monomer in step (2) is (0.15~0.5):1; The intermediate containing unsaturated double bonds in step (3) accounts for 3-15% of the mass fraction of the acrylic monomer in step (2); The free radical initiator in the aqueous solution of the free radical initiator in step (3) accounts for 0.3-0.5% of the mass fraction of the acrylic monomer in step (2); In step (3), the mass ratio of free radical initiator to water in the free radical initiator aqueous solution is (0.035 to 0.09):

10.

5. The method for preparing the environmentally friendly hygroscopic sizing agent for aramid fibers according to claim 1, characterized in that, The acrylate mentioned in step (3) is selected from at least one of polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, and poly(propylene glycol) dimethacrylate; preferably, the molecular weight of the polyethylene glycol dimethacrylate is 400-1000, the molecular weight of the polyethylene glycol diacrylate is 400-1000, and the molecular weight of the poly(propylene glycol) dimethacrylate is 400-800. The free radical initiator mentioned in step (3) is selected from at least one of ammonium persulfate, potassium persulfate, azobisisobutyronitrile, and benzoyl peroxide.

6. The method for preparing the environmentally friendly hygroscopic sizing agent for aramid fibers according to claim 1, characterized in that, The crosslinking agent mentioned in step (4) is selected from at least one of glycidyl methacrylate, N,N'-methylenebisacrylamide, trimethylolpropane trimethacrylate, and 1,4-butanediol dimethacrylate; The crosslinking agent in step (4) accounts for 0.5-1.0% of the mass fraction of the acrylic monomer in step (2).

7. An environmentally friendly hygroscopic sizing agent for aramid fibers, characterized in that, It is prepared by the method for preparing an environmentally friendly hygroscopic sizing agent for aramid fibers as described in any one of claims 1-6.

8. The use of the environmentally friendly hygroscopic sizing agent for aramid fibers as described in claim 7 in preventing moisture absorption on the surface of aramid fibers.

9. The method of using the environmentally friendly hygroscopic sizing agent for aramid fibers according to claim 7, characterized in that, Includes the following steps: (1) The aramid fiber described in claim 7 is uniformly sprayed onto the surface of the aramid fiber or fabric with an environmentally friendly hygroscopic sizing agent to form a dense sizing film. (2) The sizing aramid fibers or fabrics can be dried by heating.

10. The method of using the environmentally friendly hygroscopic sizing agent for aramid fibers according to claim 9, characterized in that, The drying temperature is 80℃~120℃, and the drying time is 1h~2h.

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