Polyoxymethylene fiber sizing agent and preparation method thereof

Abstract

The present invention provides a polyformaldehyde fiber sizing agent, comprising a bridging agent, an outer layer emulsion, a pH regulator and water; the bridging agent comprises a compound represented by formula (I). The present application also provides a method for preparing the polyformaldehyde fiber sizing agent. The present application also provides polyformaldehyde fiber and concrete. The polyformaldehyde fiber sizing agent provided in the present application can improve the surface activity of polyformaldehyde fiber and form a good interface with ultra-high performance concrete; and the mechanical properties of concrete comprising polyformaldehyde fiber are significantly improved. On the other hand, the preparation method of the polyformaldehyde fiber sizing agent is simple, easy to operate, easy to implement, and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of reinforced concrete, in particular to a polyoxymethylene fiber sizing agent, a preparation method thereof and polyoxymethylene fiber. Background Art

[0002] Ultra-high performance concrete (UHPCC) is a special engineering material with ultra-high strength, toughness, and high durability. It has good application prospects in defense engineering, marine engineering, nuclear industry, protective engineering, and interior and exterior materials. Compared with ordinary concrete, UHPCC generally uses fine yarn as a skeleton, adds silica fume, high-efficiency water reducer, and reinforcing fiber, and utilizes the filling properties and volcanic ash effect of mineral admixtures to improve the density of concrete. Reinforcing fibers are generally steel fibers, basalt fibers, ultra-high molecular weight polyethylene fibers, and polyoxymethylene fibers. Organic fibers have ultra-high toughness and can effectively improve the crack resistance and impact resistance of ultra-high performance concrete. However, the smooth surface and chemical inertness of ultra-high molecular weight polyethylene fibers and polyoxymethylene fibers make it difficult for their surfaces to react chemically and poorly bond with the matrix, which to a certain extent reduces their reinforcement effect.

[0003] Ultra-high molecular weight polyethylene (UHMWPE) fibers, one of the three main functional fibers, have seen numerous reports on their surface modification. For example, patent CN104278510A uses a mixed solution of potassium permanganate and concentrated nitric acid to chemically oxidize UHMWPE fibers, introducing polar groups on the fiber surface and enhancing interfacial interactions. Patent CN1035308A uses plasma to surface treat UHMWPE fibers, significantly enhancing their wettability and surface adhesion to common substrates. However, there are currently few reports on surface modification of polyoxymethylene (POM) fibers for the reinforcement of ultra-high performance concrete (UHPCC). Therefore, finding new methods for improving the surface treatment of POM fibers is of great practical significance. Summary of the Invention

[0004] The technical problem solved by the present invention is to provide a polyformaldehyde fiber sizing agent, which can improve the surface activity of polyformaldehyde fiber. Furthermore, the polyformaldehyde fiber can form a good interface effect when applied to concrete, thereby increasing the interaction force between the polyformaldehyde fiber and the matrix.

[0005] In view of this, the present application provides a polyoxymethylene fiber sizing agent, comprising a bridging agent, an outer layer emulsion, a pH regulator and water;

[0006] The bridging agent includes a compound as shown in formula (I);

[0007]

[0008] Wherein, R is a reaction residue of one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine, n=1-10, and m represents the degree of polymerization of the bisphenol A epoxy resin, specifically 1-10.

[0009] Preferably, the content of the bridging agent is 1.0-10.0 wt %, the content of the resin in the outer layer emulsion is 3.0-25.0 wt %, the content of the pH regulator is 0.01-2.0 wt %, and the balance is water.

[0010] Preferably, the outer layer emulsion is selected from one or more of bisphenol A epoxy emulsion, bisphenol F epoxy emulsion, polyphenol epoxy emulsion and aliphatic glycidyl ether epoxy emulsion; the pH regulator is selected from one or more of formic acid, acetic acid, citric acid and organic amines.

[0011] Preferably, the preparation method of the bridging agent comprises the following steps:

[0012] reacting a base amine with polyether polyol glycidyl ether to obtain a first intermediate;

[0013] reacting the first intermediate with an epoxy resin to obtain a second intermediate;

[0014] The second intermediate, a basic amine and water are reacted to obtain a bridging agent.

[0015] Preferably, the base amine is selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine, and the molar ratio of the base amine to the polyether polyol glycidyl ether is (2.4-2.0):1; in the reaction to obtain the first intermediate, the reaction temperature is 0-30°C and the time is 1-5h; in the reaction to obtain the second intermediate, the reaction temperature is 0-30°C and the time is 1-5h; in the reaction to obtain the third intermediate, the reaction temperature is 0-30°C and the time is 1-5h.

[0016] Preferably, the content of the bridging agent is 1.0-8.0 wt %, the content of the resin in the outer layer emulsion is 5.0-20.0 wt %, the content of the pH regulator is 0.1-1.5 wt %, and the balance is water.

[0017] The present application also provides a method for preparing a polyoxymethylene fiber sizing agent, comprising the following steps:

[0018] mixing the bridging agent and water to obtain a preformed bridging agent;

[0019] mixing the outer layer emulsion and water to obtain a preformed outer layer emulsion;

[0020] The prefabricated bridging agent, water and the prefabricated outer layer emulsion are stirred and then a pH regulator is added to obtain a polyoxymethylene fiber sizing agent;

[0021] The bridging agent includes a compound as shown in formula (I);

[0022]

[0023] Wherein, R is a reaction residue of one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine, n=1-10, and m represents the degree of polymerization of the bisphenol A epoxy resin, specifically 1-10.

[0024] Preferably, in the step of obtaining the prefabricated bridging agent, the mass ratio of the bridging agent to the water is 1:(3-8); in the step of obtaining the prefabricated outer layer emulsion, the mass ratio of the outer layer emulsion to water is 1:(2-5); and the pH value of the polyformaldehyde fiber sizing agent is 8.0-9.5.

[0025] The present application also provides a polyformaldehyde fiber, comprising a polyformaldehyde fiber body and a polyformaldehyde fiber sizing agent, wherein the polyformaldehyde fiber sizing agent is the polyformaldehyde fiber sizing agent described or the polyformaldehyde fiber sizing agent prepared by the preparation method described.

[0026] The present application also provides a concrete comprising polyformaldehyde fiber, wherein the polyformaldehyde fiber is the polyformaldehyde fiber described above.

[0027] The present application provides a polyformaldehyde fiber sizing agent, which is composed of a bridging agent, an outer layer emulsion, a pH regulator and water, wherein the bridging agent includes a specific compound; the bridging agent can repair cracks generated in the polyformaldehyde fiber precursor during the molding process and play a role in protecting the fiber. At the same time, the coating formed on the surface of the polyformaldehyde fiber has a large number of active functional groups. The amino group forms a hydrogen bond with the CO in the polyformaldehyde, and the interface interaction with the fiber is enhanced by crack penetration and hydrogen bonding. At the same time, the outer layer active functional groups in the bridging agent react chemically with the epoxy groups in the outer layer emulsion to form a strong mechanical interlocking layer. Another part of the active organic functional groups can react with the cement matrix and play a bridge role. Therefore, the bridging agent can improve the mechanical strength, interface bonding and fatigue life of the polyformaldehyde fiber reinforced composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the contact angle between polyoxymethylene fiber and water;

[0029] Figure 2 Schematic diagram of the contact angle between polyoxymethylene fiber obtained by using the polyoxymethylene sizing agent of Example 3 of the present invention and water;

[0030] Figure 3 This is the infrared spectrum of the bridging agent prepared in the embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0032] In view of the performance requirements of polyformaldehyde fibers and concrete in the prior art, this application provides a polyformaldehyde fiber sizing agent and a preparation method thereof, which can improve the surface activity of polyformaldehyde fibers, form a good interface with ultra-high performance concrete, and enhance the interaction between the fibers and the matrix. Specifically, this application first provides a polyformaldehyde fiber sizing agent, and the polyformaldehyde fibers prepared therefrom are particularly suitable for reinforcing ultra-high performance concrete. The polyformaldehyde fiber sizing agent includes: a bridging agent, an outer layer emulsion, a pH regulator, and water;

[0033] The bridging agent includes a compound as shown in formula (I);

[0034]

[0035] Wherein, R is the reaction residue of one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine, n=1 to 10, preferably 8, and m represents the degree of polymerization of the bisphenol A epoxy resin, which can be specifically 0, 1, 2, 3, 4, 5, 10, 15, 20, 25, or 30.

[0036] In the above-mentioned polyoxymethylene fiber sizing agent, the outer layer emulsion is one or more of bisphenol A epoxy emulsion, bisphenol F epoxy emulsion, polyphenol epoxy emulsion and aliphatic glycidyl ether epoxy emulsion.

[0037] In the above-mentioned polyoxymethylene fiber sizing agent, the pH regulator is selected from one or more of formic acid, acetic acid, citric acid and organic amines.

[0038] In the present application, the content of the bridging agent is 1.0-10.0wt%, the content of the resin in the outer layer emulsion is 3.0-25.0wt%, the content of the pH regulator is 0.01-2.0wt%, and the balance is water; specifically, the content of the bridging agent is 1.0-8.0wt%, the content of the resin in the outer layer emulsion is 5.0-20.0wt%, the content of the pH regulator is 0.1-1.5wt%, and the balance is water.

[0039] Furthermore, the preparation method of the bridging agent comprises the following steps:

[0040] reacting a base amine with polyether polyol glycidyl ether to obtain a first intermediate;

[0041] reacting the first intermediate with an epoxy resin to obtain a second intermediate;

[0042] The second intermediate, a basic amine and water are reacted to obtain a bridging agent.

[0043] In the preparation method of the bridging agent provided by the present invention, a base amine and a polyether polyol glycidyl ether are first mixed in an organic solvent to carry out a ring-opening reaction. The base amine is selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine. In a specific embodiment, the base amine is selected from triethylenetetramine; the organic solvent is preferably one or more of dioxane, propylene glycol monomethyl ether and NN dimethylacetamide. Specifically, the organic solvent is selected from dioxane; the polyether polyol glycidyl ether is polyethylene glycol glycidyl ether; the molar ratio of the base amine to the polyether polyol glycidyl ether is 2.0 to 2.5:1. Specifically, the base amine and The molar ratio of polyether polyol glycidyl ether is (2.1-2.3):1; the molar ratio of the polyether polyol glycidyl ether to the organic solvent is 1:(1-1.5), specifically, the molar ratio of the polyether polyol glycidyl ether to the organic solvent is 1:(1-1.3); the temperature of the mixing reaction is preferably 0-30°C, specifically 5°C, 10°C, 15°C, 20°C, 25°C or 30°C; the time of the mixing reaction is preferably 1.5-3h, specifically 1.5h, 2h, 2.5h and 3h.

[0044] In the present invention, the specific process of mixing the base amine and the polyether polyol glycidyl ether in an organic solvent comprises:

[0045] The polyether polyol glycidyl ether and the base amine are dissolved in an organic solvent respectively, and the obtained polyether polyol glycidyl ether solution is titrated into the base amine solution for mixing and reaction.

[0046] The dissolution temperature is preferably room temperature; after the mixing reaction is completed, a first intermediate is obtained.

[0047] After obtaining the first intermediate, the present application mixes the first intermediate with an epoxy resin for a ring-opening reaction. Wherein, the epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy, hydrogenated bisphenol A epoxy resin and novolac epoxy resin. The molar ratio of the epoxy resin to the first intermediate is preferably 1: (1 to 1.5), more preferably 1: (1.1 to 1.3); the temperature of the mixing reaction is 40 to 60°C, specifically 40°C, 45°C, 50°C, 55°C or 60°C; the time of the mixing reaction is preferably 1.5 to 3 hours, specifically 1.5 hours, 2 hours, 2.5 hours and 3 hours.

[0048] In the present invention, the specific process of mixing the first intermediate with the epoxy resin preferably includes:

[0049] The first intermediate is heated, and after the system temperature stabilizes, it is mixed with the epoxy resin for reaction. After the mixing reaction is completed, the second intermediate is obtained.

[0050] After obtaining the second intermediate, the second intermediate, a base amine, and deionized water are mixed to perform a ring-opening reaction. The molar ratio of the base amine to the second intermediate is preferably 1:(1-1.5), specifically 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5. The temperature of the mixing reaction is preferably 30-40°C, specifically 30°C, 35°C, or 40°C. The mixing reaction time is preferably 2-4 hours, specifically 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours. After the mixing reaction is completed, a bridging agent is obtained.

[0051] The content of the compound represented by formula (I) in the bridging agent is 20 to 35 wt %.

[0052] In the present invention, the bridging agent plays a core role in the sizing agent: on the one hand, it can repair cracks generated by the polyformaldehyde fiber precursor during the molding process and play a role in protecting the fiber; on the other hand, the coating attached to the surface of the polyformaldehyde fiber has a large number of active functional groups, and the amino groups form hydrogen bonds with the CO bonds in the polyformaldehyde, which enhances the interfacial interaction with the fiber through crack penetration and hydrogen bonding. At the same time, the active functional groups in the outer layer react chemically with the epoxy groups in the outer emulsion layer to form a strong mechanical interlocking layer. Another part of the active organic functional groups can react with the cement matrix and play a bridge role. Therefore, the bridging agent is very important and can improve the mechanical strength, interfacial bonding and fatigue life of the polyformaldehyde fiber reinforced composite material.

[0053] The outer emulsion layer is one of the most important components of polyoxymethylene fiber, which determines the production, processing and technical performance and mechanical properties of polyoxymethylene fiber and composite materials. Selecting a suitable outer emulsion can not only ensure the smoothness of subsequent processing, but also ensure the wetting performance of polyoxymethylene fiber.

[0054] The present application also provides a method for preparing the above-mentioned polyoxymethylene fiber sizing agent, comprising the following steps:

[0055] mixing the bridging agent and water to obtain a preformed bridging agent;

[0056] mixing the outer layer emulsion and water to obtain a preformed outer layer emulsion;

[0057] The prefabricated bridging agent, water and the prefabricated outer layer emulsion are stirred and then a pH regulator is added to obtain a polyoxymethylene fiber sizing agent.

[0058] More specifically, the preparation method of the polyoxymethylene fiber sizing agent comprises the following steps:

[0059] Step 1: Add 3 to 8 times the weight of the bridging agent to the first disperser, then add the bridging agent, and stir evenly for 10 to 20 minutes at a stirring speed of 50 to 200 r / min to obtain a prefabricated bridging agent;

[0060] Step 2: Add water 2 to 5 times the weight of the outer layer emulsion into a second disperser, then add the outer layer emulsion, and stir evenly for 10 to 20 minutes at a stirring speed of 50 to 200 r / min to obtain a prefabricated outer layer emulsion;

[0061] Step 3: Add 20% to 40% of the mass of the pre-configured sizing agent into the preparation kettle, then add the prefabricated bridging agent; then add the prefabricated outer layer emulsion in step 2; finally add the remaining water, stir for 15 to 30 minutes at a stirring speed of 50 to 200 r / min, and finally add a pH regulator to adjust the pH value to 8.5 to 9.5 to obtain a polyoxymethylene fiber sizing agent.

[0062] The present application also provides a polyformaldehyde fiber, which includes polyformaldehyde fiber and a polyformaldehyde fiber sizing agent, wherein the polyformaldehyde fiber sizing agent is the polyformaldehyde fiber sizing agent described in the above scheme.

[0063] In the polyoxymethylene fiber provided in the present application, the polyoxymethylene fiber sizing agent accounts for 0.5 to 2.0 wt % of the polyoxymethylene fiber. Specifically, the polyoxymethylene fiber sizing agent accounts for 1.0 to 1.5 wt % of the polyoxymethylene fiber.

[0064] The present application also provides a concrete comprising the polyoxymethylene fiber described in the above solution.

[0065] In the concrete, except for the polyoxymethylene fiber, other components are well known to those skilled in the art and are not particularly limited in this application.

[0066] The polyformaldehyde fiber sizing agent provided by the present invention can improve the surface properties of super polyformaldehyde fiber, while improving its bonding ability with the interface of reinforced ultra-high performance concrete, thereby improving the mechanical properties of the product.

[0067] In order to further understand the present invention, the polyoxymethylene fiber sizing agent and polyoxymethylene fiber provided by the present invention are described in detail below with reference to the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0068] The following embodiment is a method for preparing a polyoxymethylene fiber sizing agent, comprising the following steps:

[0069] Step 1: At 25°C, add water 5 times the weight of the bridging agent into the first disperser, then add the bridging agent, and stir evenly for 15 minutes at a stirring speed of 150 r / min to obtain a prefabricated bridging agent;

[0070] Step 2: At 25°C, add water twice the weight of the outer layer emulsion into the second disperser, then add the outer layer emulsion, and stir evenly for 10 minutes at a stirring speed of 150 r / min to obtain a prefabricated outer layer emulsion;

[0071] Step 3: At 25°C, add 30% of the mass of the pre-configured sizing agent into the configuration kettle, then add the prefabricated bridging agent in step 1), and then add the prefabricated outer layer emulsion in step 2); finally, add the remaining water, stir for 20 minutes at a stirring speed of 150 r / min, and finally add a pH regulator to adjust the pH to 9.0 to obtain a polyoxymethylene fiber sizing agent.

[0072] The polyoxymethylene fiber sizing agent is coated on the surface of the polyoxymethylene fiber, and the oil content on the surface of the prepared polyoxymethylene fiber is 1.0%.

[0073] The preparation of the bridging agent in the following examples is as follows:

[0074] A) adding triethylenetetramine and dioxane in a molar ratio of 2:1 to a reaction kettle, controlling the temperature at 20° C., titrating a mixture of polyethylene glycol glycidyl ether (n=8) and dioxane in a molar ratio of 1:1 into the reaction kettle, and reacting at 20° C. for 2 h to obtain a first intermediate;

[0075] B) heating the obtained first intermediate to 40° C., and after the temperature stabilizes, adding bisphenol A epoxy (m=2) and a solvent, and reacting at this temperature for 2 hours to obtain a second intermediate; the molar ratio of the epoxy resin to the first intermediate is 1:1.5;

[0076] C) cooling the obtained second intermediate to 30° C., adding triethylenetetramine and deionized water (controlling the solid content at 30%), and reacting at this temperature for 2 hours to obtain a bridging agent; wherein the molar ratio of triethylenetetramine to the second intermediate is 1:1.5.

[0077] Figure 3 is the infrared spectrum of the bridging agent prepared above.

[0078] Example 1

[0079] The components of polyoxymethylene fiber sizing agent are as follows:

[0080] bridging agent 3.0%;

[0081] outer emulsion 10.0%;

[0082] pH adjuster 0.2%;

[0083] Water 86.8%.

[0084] Example 2

[0085] The components of polyoxymethylene fiber sizing agent are as follows:

[0086] bridging agent 5.0%;

[0087] outer emulsion 16.0%;

[0088] pH adjuster 0.2%;

[0089] Water 78.8%.

[0090] Example 3

[0091] The components of polyoxymethylene fiber sizing agent are as follows:

[0092] bridging agent 7.0%;

[0093] outer emulsion 22.0%;

[0094] pH adjuster 0.2%;

[0095] Water 70.8%.

[0096] In the above embodiments 1 to 3, the outer layer emulsion is selected from bisphenol A epoxy emulsion, and the pH regulator is selected from acetic acid.

[0097] The polyoxymethylene fiber sizing agent prepared in Examples 1 to 3 was applied to the surface of the polyoxymethylene fiber body, with the content of 1.0 wt %.

[0098] The polyoxymethylene fibers prepared in Examples 1 to 3 were tested for contact angle and interfacial properties by the contact angle method and the pull-out method, and the bending load of the reinforced concrete slabs thereof was tested according to GB / T 50081. The test results are shown in Table 1.

[0099] Table 1 Performance data of polyoxymethylene fibers prepared using Examples 1 to 3

[0100]

[0101] It can be seen from Table 1 that the contact angle and interfacial strength of the polyoxymethylene fiber after sizing and coating are significantly improved compared with the uncoated fiber; for example, the contact angles of the polyoxymethylene fiber prepared in Example 3 and the original polyoxymethylene fiber with water are as follows: Figure 1 and Figure 2 As shown in the figure, the contact angle of the polyformaldehyde fiber prepared in Example 3 with water is reduced by 40.5%, and the interface strength is increased by 22.2%, which indicates that the bonding between the polyformaldehyde fiber and the matrix is ​​significantly improved after sizing, which is also proven by the improvement in the bending performance of the reinforced ultra-high performance concrete.

[0102] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0103] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polyoxymethylene fiber sizing agent comprising a bridging agent, an outer layer emulsion, a pH regulator, and water; The outer layer emulsion is selected from one or more of bisphenol A epoxy emulsion, bisphenol F epoxy emulsion, polyphenol epoxy emulsion and aliphatic glycidyl ether epoxy emulsion; The bridging agent includes a compound as shown in formula (I); （I）； The preparation method of the bridging agent comprises the following steps: reacting a base amine with polyether polyol glycidyl ether to obtain a first intermediate; reacting the first intermediate with an epoxy resin to obtain a second intermediate; reacting the second intermediate, a base amine and water to obtain a bridging agent; The base amine is selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine; Wherein, R is a reaction residue of one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine, n=1-10, and m represents the degree of polymerization of the bisphenol A epoxy resin, specifically 1-10.

2. The polyoxymethylene fiber sizing agent according to claim 1, characterized in that The content of the bridging agent is 1.0-10.0 wt %, the content of the resin in the outer layer emulsion is 3.0-25.0 wt %, the content of the pH regulator is 0.01-2.0 wt %, and the balance is water.

3. The polyoxymethylene fiber sizing agent according to claim 1, characterized in that The pH regulator is selected from one or more of formic acid, acetic acid, citric acid and organic amines.

4. The polyoxymethylene fiber sizing agent according to claim 1, characterized in that The molar ratio of the base amine to the polyether polyol glycidyl ether is (2.4-2.0):1; in the reaction to obtain the first intermediate, the reaction temperature is 0-30°C and the reaction time is 1-5 hours; in the reaction to obtain the second intermediate, the reaction temperature is 0-30°C and the reaction time is 1-5 hours; in the reaction to obtain the third intermediate, the reaction temperature is 0-30°C and the reaction time is 1-5 hours.

5. The polyoxymethylene fiber sizing agent according to claim 1, characterized in that The content of the bridging agent is 1.0-8.0 wt %, the content of the resin in the outer layer emulsion is 5.0-20.0 wt %, the content of the pH regulator is 0.1-1.5 wt %, and the balance is water.

6. The method for preparing the polyoxymethylene fiber sizing agent according to any one of claims 1 to 5, comprising the following steps: mixing the bridging agent and water to obtain a preformed bridging agent; mixing the outer layer emulsion and water to obtain a preformed outer layer emulsion; The prefabricated bridging agent, water and the prefabricated outer layer emulsion are stirred and then a pH regulator is added to obtain a polyoxymethylene fiber sizing agent; The bridging agent includes a compound as shown in formula (I); （I）； The preparation method of the bridging agent comprises the following steps: reacting a base amine with polyether polyol glycidyl ether to obtain a first intermediate; reacting the first intermediate with an epoxy resin to obtain a second intermediate; reacting the second intermediate, a base amine and water to obtain a bridging agent; The base amine is selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine; Wherein, R is a reaction residue of one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine, n=1-10, and m represents the degree of polymerization of the bisphenol A epoxy resin, specifically 1-10.

7. The preparation method according to claim 6, characterized in that In the step of obtaining the prefabricated bridging agent, the mass ratio of the bridging agent to the water is 1:(3~8); in the step of obtaining the prefabricated outer layer emulsion, the mass ratio of the outer layer emulsion to water is 1:(2~5); and the pH value of the polyoxymethylene fiber sizing agent is 8.0~9.

5.

8. A polyoxymethylene fiber comprising a polyoxymethylene fiber body and a polyoxymethylene fiber sizing agent, wherein the polyoxymethylene fiber sizing agent is the polyoxymethylene fiber sizing agent according to any one of claims 1 to 5 or the polyoxymethylene fiber sizing agent prepared by the preparation method according to any one of claims 6 to 7.

9. Concrete comprising polyoxymethylene fiber, wherein the polyoxymethylene fiber is the polyoxymethylene fiber according to claim 8.

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