Anti-oxidation waterborne polyurethane film-forming agent for glass fiber chopped yarn and preparation method of anti-oxidation waterborne polyurethane film-forming agent

Abstract

The invention belongs to the technical field of glass fiber additives, and particularly relates to an anti-oxidation waterborne polyurethane film-forming agent for glass fiber chopped yarns and a preparation method thereof.The anti-oxidation waterborne polyurethane film-forming agent for the glass fiber chopped yarns comprises effective components and water, the effective components account for 30-45% of the total mass of the antioxidant waterborne polyurethane film-forming agent for the glass fiber chopped yarn and are prepared from the following raw materials in percentage by weight: 10-15% of polyether polyol, 25-45% of polyester polyol, 15-35% of isocyanate, 0.01-0.02% of a catalyst, 1.5-5% of a first chain extender, 1.5-5% of a second chain extender, 3-10% of an emulsifier, 3-5% of a first organic solvent and 10-15% of a second organic solvent, 1-5% of citric acid and 1-5% of urea. The carbon quantum dots prepared by adding citric acid, urea and ethylene glycol are used for adjusting the oxidation resistance of the polyurethane film-forming agent, and the film-forming agent with good processability, mechanical property, film-forming property and oxidation resistance is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of glass fiber additives, and particularly relates to an antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarns and a preparation method thereof. Background Art

[0002] Chopped glass fiber yarn boasts excellent properties such as high strength, corrosion resistance, electrical insulation, and low flammability. As a reinforcing material in high-performance composite materials, it is widely used in defense fields such as aviation, aerospace, and the nuclear industry. A water-based polyurethane emulsion film-forming agent is a component of chopped glass fiber yarn. It forms a thin, tough, continuous protective film on the fiber surface. However, when chopped glass fiber yarn is processed to prepare composite materials, the film formed on the composite surface is susceptible to oxidation to a certain extent.

[0003] Chinese patent CN112480360A discloses a water-based polyurethane film-forming agent for glass fiber, which includes the following components, with the weight percentage of each component expressed as follows: 40-50% polyethylene adipate, 25-35% diisocyanate, 2-8% chain extender, 0.5-4% triethylamine, and 0.06-0.15% dibutyltin dilaurate.

[0004] The core problem of this patent is that no modified structure with antioxidant properties and high surface energy is added during the subsequent processing of glass fiber into composite materials. Instead, only the commonly used formula of general water-based polyurethane is applied, resulting in key performance not meeting the standards. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the technical problem to be solved by the present invention is to provide an antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarn, which has good processing performance, mechanical properties, film-forming properties and antioxidant properties, and the present invention also provides a preparation method thereof.

[0006] The technical solution adopted by the present invention to solve its technical problem is: The antioxidant water-based polyurethane film-forming agent for glass fiber chopped strands of the present invention comprises an active ingredient and water, wherein the active ingredient accounts for 30-45% of the total mass of the antioxidant water-based polyurethane film-forming agent for glass fiber chopped strands, and the active ingredient is prepared from the following raw materials in percentage by weight: 10-15% of polyether polyol, 25-45% of polyester polyol, 15-35% of isocyanate, 0.01-0.02% of catalyst, 1.5-5% of a first chain extender, 1.5-5% of a second chain extender, 3-10% of an emulsifier, 3-5% of a first organic solvent, 10-15% of a second organic solvent, 1-5% of citric acid, and 1-5% of urea.

[0007] in: The molecular weight of the polyether polyol is 1500-3000, and the molecular weight of the polyester polyol is 1000-2000; the polyether polyol is one or more of polyoxypropylene glycol, polytetramethylene glycol or polyoxypropylene triol, and the polyester polyol is one or more of polyethylene adipate, polybutylene adipate-1,4-diol or polyneopentyl adipate.

[0008] The isocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate or 4,4-dicyclohexylmethane diisocyanate.

[0009] The first chain extender is one or more of neopentyl glycol, 1,4-butanediol, and 1,2-cyclohexanediol; the second chain extender is one or more of 3,3-dichloro-4,4-diaminodiphenylmethane, hydrazine hydrate, diethyltoluenediamine, 3,5-diaminoisobutyl p-chlorobenzoate, 3,5-dimethylthiotoluenediamine, or isophoronediamine; and the catalyst is one or more of dibutyltin dilaurate, stannous isooctanoate, dibutyltin dibutyrate, pentamethyldiethylenetriamine, or bismuth isooctanoate.

[0010] The emulsifier is one or more of a polyoxyethylene emulsifier, an alkyl alcohol polyoxyethylene ether emulsifier or a polyurethane reactive emulsifier. The first organic solvent is ethylene glycol and the second organic solvent is acetone.

[0011] The method for preparing the antioxidant water-based polyurethane film-forming agent for glass fiber chopped strands is characterized by comprising the following steps: (1) mixing polyether polyol and polyester polyol and then dehydrating them to obtain dehydrated polyol; (2) mixing citric acid and urea, adding the mixture to the first organic solvent, stirring, and keeping warm. After the end of the warming, the mixture is cooled to room temperature, and then centrifuged to obtain and collect the supernatant; (3) adding the supernatant obtained in step (2) to the dehydrated polyol in step (1), and then adding isocyanate and a catalyst, and performing a prepolymerization reaction under the protection of an inert gas to obtain a polyurethane prepolymer; (4) adding a first chain extender to the polyurethane prepolymer to carry out a reaction, then adding a second organic solvent, continuing the reaction, and then adding an emulsifier to carry out preliminary emulsification to obtain a preliminary emulsified product; (5) The initial emulsified product is cooled and deionized water is added and stirred for re-emulsification, and then a second chain extender is added and stirred continuously for chain extension reaction to obtain an antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarn.

[0012] In the step (1), the dehydration temperature is 100-120° C., and the dehydration time is 60-120 min.

[0013] In the step (2), the stirring time is 30-60 minutes, the holding temperature is 180-200°C, and the holding time is 4-6 hours; the centrifugal speed is 8000-12000 rpm, and the prepolymerization temperature in step (3) is 80-85°C, and the prepolymerization time is 60-120 minutes.

[0014] In the step (4), the reaction time is 50-80 min, the reaction temperature is 80-85°C, the continued reaction temperature is 55-60°C, the continued reaction time is 10-15 min, the initial emulsification time is 20-30 min, and the initial emulsification temperature is 55-60°C.

[0015] In the step (5), the cooling temperature is 35-45°C, the stirring speed is 1200-1500 rpm, and the re-emulsification time is 25-30 min; the continuous stirring speed is 500-800 rpm, the chain extension reaction time is 60-90 min, and the chain extension reaction temperature is 35-45°C.

[0016] The present invention first generates an isocyanate-terminated polyurethane prepolymer by reacting polyether polyol, polyester polyol and diisocyanate, and adds carbon quantum dots prepared by the supernatant of citric acid, urea and ethylene glycol to modify the surface of the film-forming agent to modify its antioxidant capacity, so that its surface is covered with a protective film. In the later stage of emulsification, an amino compound is finally used to perform end-capping treatment at a lower temperature, and the carbamate bond generated by it and the remaining isocyanate can also be well coated by the carbon quantum dots. The entire preparation process is simple and clear, and an environmentally friendly film-forming agent with low VOC emissions is obtained. The obtained product serves as an important film-forming agent for glass fiber yarn, which gives the glass fiber good bundling and ductility, as well as antioxidant capacity for subsequent processing. In addition, the film-forming agent prepared by the present invention can also be used in various fields such as fabric sizing agents, leather finishing agents, carbon fiber sizing agents, adhesives and coatings. Compared to other waterborne polyurethane film-forming agents, this waterborne polyurethane film-forming agent, thanks to its larger molecular weight and excellent antioxidant capacity, combines both physical stiffness and antioxidant properties after film formation. The waterborne polyurethane is designed with nonionic hydrophilic groups, which ensures strong binding to substrate surfaces containing negative groups such as hydroxyl groups, ensuring the stability of the film-forming agent.

[0017] The present invention does not affect the excellent mechanical and chemical properties of the waterborne polyurethane resin itself. The carbon quantum dots prepared by adding citric acid, urea and ethylene glycol are used to improve the surface defects of the polyurethane film-forming agent and adjust its antioxidant capacity. When the present invention is used as a film-forming agent for glass fiber chopped yarn, it can better change the material oxidation and yellowing phenomenon caused by glass fiber in the production process and subsequent processing applications, so that the glass fiber yarn has good mechanical properties while ensuring its service life. The carbon quantum dots prepared by citric acid, urea and ethylene glycol play a good role in the polyurethane film-forming agent, provide an excellent film-forming agent for the production of glass fiber chopped yarn, and expand the application of glass fiber. The process of the present invention is simple, the reaction is easy to control, the raw materials used are easy to obtain, and it is suitable for industrial production.

[0018] The beneficial effects of the present invention are: The carbon quantum dots prepared by adding citric acid, urea and ethylene glycol are used to adjust the antioxidant ability of the polyurethane film-forming agent, aiming to obtain a film-forming agent with good processing performance, mechanical properties, film-forming performance and antioxidant performance.

[0019] The present invention forms a carbon quantum dot surface modifier by heating citric acid, urea, and ethylene glycol at high temperatures. Citric acid contains three carboxyl groups and one hydroxyl group, providing a rich carbon and oxygen source and readily forming sp² carbon nuclei upon thermal decomposition. Urea is an excellent nitrogen source. During the reaction, nitrogen-containing groups, such as amino and cyano groups, generated by urea decomposition are effectively incorporated into the carbon skeleton formed by the dehydration and carbonization of citric acid, forming nitrogen-doped carbon quantum dots. When ethylene glycol is used as a solvent for citric acid and urea, it more effectively drives the dehydration and carbonization of citric acid, promoting the formation and growth of carbon nuclei, resulting in the production of 80-200 nm carbon quantum dots. This nanostructure facilitates better adhesion of the carbon quantum dots to the surface of the polyurethane film. Ethylene glycol also utilizes its abundant surface active hydroxyl groups, allowing the carbon quantum dots to act as nanochain extenders and directly participate in the -NCO / -OH chain extension reaction, achieving molecular-level dispersion and strong interfacial chemical bonding of the carbon quantum dots within the waterborne polyurethane matrix through covalent bonds. The unextended carbon quantum dots can be directly dispersed as surface modifiers within the waterborne polyurethane matrix, forming a nanoscale barrier that blocks oxygen penetration, significantly reducing the oxidation rate and delaying material failure. Furthermore, due to the small size and large specific surface area of ​​the carbon quantum dots, they can produce a surface effect, resulting in composite materials with superior antioxidant properties. The aqueous film-forming agent prepared by this invention exhibits good stability after storage at room temperature (25-30°C) for six months without flocculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an SEM image of carbon quantum dots prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The embodiments of the present invention are further described below with reference to the accompanying drawings: The manufacturer of the alkyl alcohol polyoxyethylene ether emulsifier is BASF of Germany, and the model is Emulan®TO 40; The manufacturer of polyoxyethylene emulsifier is BASF of Germany, and the model is PluronicPE6800.

[0022] Example 1 The preparation method of an antioxidant water-based polyurethane film-forming agent for glass fiber chopped strands comprises the following steps: (1) 70 g of polytetrahydrofuran diol and 220 g of polyethylene adipate glycol were mixed, and then vacuum dehydrated at 100° C. for 80 min to obtain a dehydrated polyol; (2) 8 g of citric acid and 10 g of urea were mixed and added to 25 g of ethylene glycol, stirred for 30 min, and kept at 200 ° C for 6 h. After the end of the heat preservation, it was cooled to room temperature and then centrifuged at 10,000 rpm to obtain and collect the supernatant; the SEM image of the carbon quantum dots obtained after the supernatant was dried is shown in the figure. Figure 1 As shown, it presents a standard spherical shape; (3) Cooling the dehydrated polyol in step (1) to 85° C., adding the supernatant obtained in step (2), and then adding 165.4 g of isophorone diisocyanate and 0.08 g of dibutyltin dilaurate, and carrying out a prepolymerization reaction at 80° C. for 70 min under inert gas protection to obtain a polyurethane prepolymer; (4) Add 25.8 g of neopentyl glycol to the polyurethane prepolymer at 80°C and react for 60 min, then add 84.8 g of acetone at 60°C and continue to react for 15 min, then add 22 g of alkyl alcohol polyoxyethylene ether emulsifier at 60°C and perform preliminary emulsification for 20 min to obtain a preliminary emulsified product; (5) The preliminary emulsified product was cooled to 40°C, and 800 g of deionized water was added at 1200 rpm for re-emulsification for 25 min. Subsequently, 22.6 g of isophorone diamine was added at 40°C and 600 rpm for chain extension reaction for 70 min to obtain an antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarn.

[0023] Example 2 The preparation method of an antioxidant water-based polyurethane film-forming agent for glass fiber chopped strands comprises the following steps: (1) 90 g of polyoxypropylene glycol and 180 g of polyethylene adipate glycol were mixed, and then vacuum dehydrated at 110° C. for 80 min to obtain a dehydrated polyol; (2) 28 g of citric acid and 25 g of urea were mixed and added to 29 g of ethylene glycol, stirred for 40 min, and kept at 180 °C for 5 h. After the end of the holding period, the mixture was cooled to room temperature and then centrifuged at 8000 rpm to obtain and collect the supernatant; (3) The dehydrated polyol in step (1) was cooled to 85° C., and the supernatant obtained in step (2) was added, followed by the addition of 159.2 g of toluene diisocyanate and 0.08 g of pentamethyldiethylenetriamine. A prepolymerization reaction was carried out at 85° C. under inert gas protection for 70 min to obtain a polyurethane prepolymer; (4) Add 23.1 g of 1,4-butanediol to the polyurethane prepolymer at 85°C and react for 60 min, then add 73.8 g of acetone at 60°C and continue to react for 10 min, then add 20 g of alkyl alcohol polyoxyethylene ether emulsifier at 60°C and perform preliminary emulsification for 30 min to obtain a preliminary emulsified product; (5) The preliminary emulsified product was cooled to 41°C, and 800 g of deionized water was added at 1200 rpm for re-emulsification for 30 min. Subsequently, 15.52 g of hydrazine hydrate was added at 41°C and 600 rpm for chain extension reaction for 70 min to obtain an antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarn.

[0024] Example 3 The preparation method of an antioxidant water-based polyurethane film-forming agent for glass fiber chopped strands comprises the following steps: (1) 65 g of polytetrahydrofuran diol and 120 g of poly(1,4-butanediol) adipate were mixed, and then vacuum dehydrated at 120° C. for 90 min to obtain a dehydrated polyol; (2) 8 g of citric acid and 10 g of urea were mixed and added to 13 g of ethylene glycol, stirred for 60 min, and kept at 190 °C for 5 h. After the end of the heat preservation, the mixture was cooled to room temperature and then centrifuged at 10,000 rpm to obtain and collect the supernatant; (3) cooling the dehydrated polyol in step (1) to 80° C., adding the supernatant obtained in step (2), and then adding 110.6 g of diphenylmethane diisocyanate and 0.08 g of bismuth isooctanoate, and carrying out a prepolymerization reaction at 80° C. for 90 min under inert gas protection to obtain a polyurethane prepolymer; (4) 18 g of neopentyl glycol was added to the polyurethane prepolymer at 80 °C and reacted for 80 min, followed by the addition of 63.6 g of acetone at 55 °C and the reaction continued for 10 min, followed by the addition of 15 g of a polyoxyethylene emulsifier at 55 °C for preliminary emulsification for 25 min to obtain a preliminary emulsified product; (5) The preliminary emulsified product was cooled to 42°C, and 800 g of deionized water was added at 1500 rpm for re-emulsification for 25 min. Subsequently, 10 g of 3,5-dimethylthiotoluenediamine was added at 42°C and 500 rpm for chain extension reaction for 60 min to obtain an antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarn.

[0025] Example 4 The preparation method of an antioxidant water-based polyurethane film-forming agent for glass fiber chopped strands comprises the following steps: (1) 55 g of polyoxypropylene triol and 230 g of polyethylene adipate glycol were mixed, and then vacuum dehydrated at 110° C. for 80 min to obtain a dehydrated polyol; (2) 22 g of citric acid and 6.8 g of urea were mixed and added to 19 g of ethylene glycol, stirred for 40 min, and kept at 180 °C for 6 h. After the end of the holding period, the mixture was cooled to room temperature and then centrifuged at 8000 rpm to obtain and collect the supernatant; (3) Cooling the dehydrated polyol in step (1) to 83° C., adding the supernatant obtained in step (2), and then adding 80 g of hexamethylene diisocyanate and 0.1 g of stannous isooctanoate, and carrying out a prepolymerization reaction at 83° C. for 100 min under inert gas protection to obtain a polyurethane prepolymer; (4) 10.6 g of 1,2-cyclohexanediol was added to the polyurethane prepolymer at 83°C and reacted for 70 min, followed by the addition of 55.8 g of acetone at 58°C and the reaction continued for 12 min, followed by the addition of 21 g of alkyl alcohol polyoxyethylene ether emulsifier at 58°C for preliminary emulsification for 25 min to obtain a preliminary emulsified product; (5) The preliminary emulsified product was cooled to 40°C, and 800 g of deionized water was added at 1200 rpm for re-emulsification for 28 min. Subsequently, 22.6 g of 3,5-diaminoisobutyl chlorobenzoate was added at 40°C and 600 rpm for chain extension reaction for 80 min to obtain an antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarn.

[0026] Example 5 The preparation method of an antioxidant water-based polyurethane film-forming agent for glass fiber chopped strands comprises the following steps: (1) 53 g of polytetrahydrofuran diol and 100 g of polyneopentyl adipate glycol were mixed, and then vacuum dehydrated at 100° C. for 60 min to obtain a dehydrated polyol; (2) 16 g of citric acid and 10 g of urea were mixed and added to 15 g of ethylene glycol, stirred for 50 min, and kept at 185 °C for 5 h. After the end of the heat preservation, the mixture was cooled to room temperature and then centrifuged at 12,000 rpm to obtain and collect the supernatant; (3) cooling the dehydrated polyol in step (1) to 85° C. and adding 2 g of the supernatant obtained in step (2), followed by adding 60 g of 4,4-dicyclohexylmethane diisocyanate and 0.06 g of dibutyltin dilaurate, and carrying out a prepolymerization reaction at 85° C. for 60 min under inert gas protection to obtain a polyurethane prepolymer; (4) 28.1 g of neopentyl glycol was added to the polyurethane prepolymer at 85°C and reacted for 70 min, followed by the addition of 52.8 g of acetone at 55°C and the reaction continued for 15 min, followed by the addition of 21 g of alkyl alcohol polyoxyethylene ether emulsifier at 55°C for preliminary emulsification for 23 min to obtain a preliminary emulsified product; (5) The preliminary emulsified product was cooled to 40°C, and 800 g of deionized water was added at 1300 rpm for re-emulsification for 30 min. Subsequently, 16.6 g of diethyltoluenediamine was added at 40°C and 800 rpm for chain extension reaction for 80 min to obtain an antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarn.

[0027] Comparative Example 1 Step (2) was removed and the remaining operations were the same as in Example 1 to obtain a film-forming agent.

[0028] Comparative Example 2 In step (2), citric acid is not added, and the remaining operations are the same as in Example 1 to obtain a film-forming agent.

[0029] Comparative Example 3 In step (2), urea is not added, and the remaining operations are the same as those in Example 1 to obtain a film-forming agent.

[0030] Comparative Example 4 In step (2), ethylene glycol is not added, and the remaining operations are the same as in Example 1 to obtain a film-forming agent.

[0031] Comparative testing was conducted on the film-forming products of Examples 1-5 and Comparative Examples 1-4. 1.5g of the film sample was placed in a glass dish 35mm in diameter and 15mm deep. The sample was tested using a ColorMeterMAX LED (full visible light spectrum) at 270°C for 10 minutes. The LAB value was measured and the product of the color difference and ab was calculated. The antioxidant performance test data for the film-forming agents of Examples 1-5 and Comparative Examples 1-4 are shown in Table 1.

[0032] As can be seen from Table 1, the antioxidant aqueous film-forming agent prepared by the present invention has significantly improved heat-resistant yellowing ability.

[0033] In summary, the present invention performs surface modification on the water-based polyurethane film-forming agent, and adopts the antioxidant water-based film-forming agent prepared by the present invention to be applied to the preparation of glass fiber products, which can better compensate for the defect of weak interface bonding in the film-forming agent caused by factors such as thermal processing or light exposure of the glass fiber material, thereby making the glass fiber material have better antioxidant properties.

Claims

1. An antioxidant water-based polyurethane film-forming agent for glass fiber chopped strands, characterized in that: The invention comprises active ingredients and water, wherein the active ingredients account for 30-45% of the total mass of the antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarns, and the active ingredients are prepared from the following raw materials in the following weight percentages: 10-15% of polyether polyol, 25-45% of polyester polyol, 15-35% of isocyanate, 0.01-0.02% of catalyst, 1.5-5% of a first chain extender, 1.5-5% of a second chain extender, 3-10% of an emulsifier, 3-5% of a first organic solvent, 10-15% of a second organic solvent, 1-5% of citric acid, and 1-5% of urea.

2. The antioxidant aqueous polyurethane film-forming agent for glass fiber chopped strands according to claim 1, characterized in that: The molecular weight of the polyether polyol is 1500-3000, and the molecular weight of the polyester polyol is 1000-2000; the polyether polyol is one or more of polyoxypropylene glycol, polytetramethylene glycol or polyoxypropylene triol, and the polyester polyol is one or more of polyethylene adipate glycol, polybutylene adipate-1,4-diol or polyneopentyl adipate glycol.

3. The antioxidant aqueous polyurethane film-forming agent for glass fiber chopped strands according to claim 1, characterized in that: The isocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate or 4,4-dicyclohexylmethane diisocyanate.

4. The antioxidant aqueous polyurethane film-forming agent for glass fiber chopped strands according to claim 1, characterized in that: The first chain extender is one or more of neopentyl glycol, 1,4-butanediol, and 1,2-cyclohexanediol; the second chain extender is one or more of 3,3-dichloro-4,4-diaminodiphenylmethane, hydrazine hydrate, diethyltoluenediamine, 3,5-diaminoisobutyl p-chlorobenzoate, 3,5-dimethylthiotoluenediamine, or isophoronediamine; and the catalyst is one or more of dibutyltin dilaurate, stannous isooctanoate, dibutyltin dibutyrate, pentamethyldiethylenetriamine, or bismuth isooctanoate.

5. The antioxidant aqueous polyurethane film-forming agent for glass fiber chopped strands according to claim 1, characterized in that: The emulsifier is one or more of a polyoxyethylene emulsifier, an alkyl alcohol polyoxyethylene ether emulsifier or a polyurethane reactive emulsifier, the first organic solvent is ethylene glycol, and the second organic solvent is acetone.

6. A method for preparing the antioxidant aqueous polyurethane film-forming agent for glass fiber chopped strands according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) mixing polyether polyol and polyester polyol and then dehydrating them to obtain dehydrated polyol; (2) mixing citric acid and urea, adding the mixture to the first organic solvent, stirring, and keeping warm. After the end of the warming, the mixture is cooled to room temperature, and then centrifuged to obtain and collect the supernatant; (3) adding the supernatant obtained in step (2) to the dehydrated polyol in step (1), and then adding isocyanate and a catalyst, and performing a prepolymerization reaction under the protection of an inert gas to obtain a polyurethane prepolymer; (4) adding a first chain extender to the polyurethane prepolymer to carry out a reaction, then adding a second organic solvent, continuing the reaction, and then adding an emulsifier to carry out preliminary emulsification to obtain a preliminary emulsified product; (5) The initial emulsified product is cooled and deionized water is added and stirred for re-emulsification, and then a second chain extender is added and stirred continuously for chain extension reaction to obtain an antioxidant water-based polyurethane film-forming agent for glass fiber chopped yarn.

7. The method for preparing an antioxidant aqueous polyurethane film-forming agent for glass fiber chopped strands according to claim 6, wherein: In step (1), the dehydration temperature is 100-120° C., and the dehydration time is 60-120 min.

8. The method for preparing an antioxidant aqueous polyurethane film-forming agent for glass fiber chopped strands according to claim 6, wherein: In step (2), the stirring time is 30-60 min, the holding temperature is 180-200° C., and the holding time is 4-6 h; the centrifugal speed is 8000-12000 rpm, and the prepolymerization temperature in step (3) is 80-85° C., and the prepolymerization time is 60-120 min.

9. The method for preparing an antioxidant aqueous polyurethane film-forming agent for glass fiber chopped strands according to claim 6, wherein: In step (4), the reaction time is 50-80 min, the reaction temperature is 80-85°C, the continued reaction temperature is 55-60°C, the continued reaction time is 10-15 min, the initial emulsification time is 20-30 min, and the initial emulsification temperature is 55-60°C.

10. The method for preparing an antioxidant aqueous polyurethane film-forming agent for glass fiber chopped strands according to claim 6, wherein: In step (5), the cooling temperature is 35-45°C, the stirring speed is 1200-1500 rpm, and the re-emulsification time is 25-30 min; the continuous stirring speed is 500-800 rpm, the chain extension reaction time is 60-90 min, and the chain extension reaction temperature is 35-45°C.

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