Sizing agent for quartz fiber, preparation method and application thereof

Abstract

The application provides a sizing agent for quartz fibers, a preparation method and application, and relates to the technical field of preparation and application of polymer compound compositions. The preparation method is a preparation process of "aromatic dianhydride pretreatment + special polycondensation treatment + mixing treatment of polyamide acid salt, tertiary amine and functional additives according to a specific ratio", and can stably prepare the sizing agent for quartz fibers; the whole preparation process is a full aqueous system, the functional additives can be completely volatilized at high temperature, and there is no residue, so that the sizing agent has the characteristics of environmental friendliness and high performance. The obtained sizing agent for quartz fibers has extremely high molecular weight and temperature resistance potential, and the glass transition temperature is above 300 DEG C. When the sizing agent is applied to the sizing treatment of quartz fibers, a high-performance protective layer which can resist high temperature above 350 DEG C can be formed on the surface of the quartz fibers, the long-term working temperature and the processing stability range of the quartz fiber reinforced polymer matrix composite are widened, and the application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of preparation and application technology of polymer compound compositions, and particularly to a sizing agent for quartz fibers, its preparation method and application. Background Technology

[0002] With the continuous advancement of modern industrial technology, increasingly stringent requirements have been placed on the lightweight, high strength, and stability of materials under extreme conditions (such as high temperatures). Against this backdrop, quartz fiber reinforced polymer matrix composites, with their excellent lightweight properties and high specific strength, have shown great application potential in the field of high-performance structural materials.

[0003] However, despite the excellent temperature resistance of quartz fibers themselves, these composite materials still face key limitations in practical applications, specifically in their limited long-term operating temperature and processing stability range. This is mainly due to the insufficient thermal stability of current sizing agents used for quartz fibers. As a crucial transition layer connecting the fiber and the polymer matrix, it often becomes the first component in the composite system to decompose or fail at high temperatures, thus failing to effectively meet the stringent processing conditions and subsequent service environments of the composite material, severely restricting its further promotion in high-performance and high-temperature applications.

[0004] Existing sizing agents for quartz fibers generally have low inherent temperature resistance, making the sizing agent film prone to thermal degradation under high-temperature processing or long-term high-temperature service conditions. Furthermore, these systems often contain various small-molecule organic additives (such as lubricants and surfactants), which are also highly susceptible to decomposition and failure at high temperatures. This not only damages the integrity and stability of the sizing agent film, affecting the long-term performance of the composite material, but may also release harmful substances, posing a potential environmental pollution risk. Summary of the Invention

[0005] The main objective of this invention is to provide a sizing agent for quartz fibers, its preparation method, and its application, aiming to solve the problems of poor heat resistance and environmental unfriendliness of existing sizing agents for quartz fibers.

[0006] To achieve the above objectives, the present invention provides a method for preparing a sizing agent for quartz fibers, comprising the following steps:

[0007] Aromatic dianhydride is heat-treated to obtain treated aromatic dianhydride; the heat treatment temperature is (T m -80)~(T m -20)℃, T m The melting point of the aromatic dianhydride is denoted as .

[0008] Aromatic diamine is dissolved in an aprotic polar organic solvent, and the treated aromatic dianhydride is added to it in multiple portions under a chemically inert atmosphere to obtain a mixture; a polycondensation reaction is carried out to obtain a polyamic acid solution.

[0009] A first tertiary amine is added to the polyamic acid solution, and the mixture is stirred to obtain a polyamic acid salt solution.

[0010] The polyamic acid salt solution was subjected to precipitation and drying treatments in sequence to obtain polyamic acid salt solid.

[0011] The polyamic acid salt solid, the second tertiary amine, and the functional additives are mixed to obtain a sizing agent for quartz fibers; the functional additives include at least one of nonionic surfactants and anionic surfactants.

[0012] In the mixture, the sum of the masses of the aromatic diamine and the aromatic dianhydride is 5-20% of the mass of the mixture; the molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1-1.5; the molar ratio of the first tertiary amine to the aromatic dianhydride is 2-3:1; the molar ratio of the second tertiary amine to the aromatic dianhydride is 1-2:1; and the mass of the functional additive is 1-2% of the mass of the sizing agent for quartz fiber.

[0013] Furthermore, the temperature of the heat treatment is 200~260℃; the atmosphere condition of the heat treatment is vacuum.

[0014] Further, the aromatic dianhydride includes at least one of pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0015] The aromatic diamine includes at least one of 4,4-diaminodiphenyl ether, m-phenylenediamine, and p-phenylenediamine;

[0016] The aprotic polar organic solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide.

[0017] Both the first tertiary amine and the second tertiary amine include at least one of triethylamine and N,N-dimethylethanolamine.

[0018] Furthermore, the method of adding the treated aromatic dianhydride in multiple steps is as follows: half of the remaining mass of the treated aromatic dianhydride is added each time, and the remaining amount is added in the last step; and the addition is judged by the obvious lightening of the solution color.

[0019] Furthermore, the duration of the polycondensation reaction is 4-6 hours.

[0020] Furthermore, the precipitation treatment method includes: adding the polyamic acid salt solution to a precipitant; the precipitant includes ethyl acetate.

[0021] Furthermore, the drying temperature is 30~50℃.

[0022] The present invention also provides a sizing agent for quartz fibers prepared by the preparation method described above, wherein the solid content of the sizing agent for quartz fibers is 0.5~2 wt.%.

[0023] The present invention also provides an application of the sizing agent for quartz fibers as described above in the sizing treatment of quartz fibers, wherein quartz fibers are immersed in the sizing agent for quartz fibers and then subjected to drying treatment and three-gradient curing treatment in sequence; the temperatures of the three-gradient curing treatment are 150~200℃, 250~300℃ and above 350℃ in sequence.

[0024] Furthermore, the drying temperature is 80~100℃.

[0025] The beneficial effects achieved by this invention are as follows:

[0026] The method for preparing a sizing agent for quartz fibers provided by this invention utilizes a process of "aromatic dianhydride pretreatment + unique polycondensation treatment + mixing of polyamic acid salts, tertiary amines, and functional additives in a specific ratio," which can stably produce a sizing agent for quartz fibers. Furthermore, the entire preparation process of this sizing agent for quartz fibers is an all-aqueous system, and the functional additives used are completely volatilized at high temperatures, leaving no residue, thus combining environmental friendliness with high performance.

[0027] The sizing agent for quartz fibers provided by this invention has extremely high molecular weight and temperature resistance potential, and the glass transition temperature of the sizing agent for quartz fibers is above 300°C.

[0028] Applying this sizing agent to the quartz fiber sizing process can form a high-performance protective layer on the quartz fiber surface that can withstand temperatures above 350°C, thus broadening the long-term working temperature and processing stability range of quartz fiber reinforced polymer matrix composites, and showing broad application prospects. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0030] Figure 1This is a photograph of the polyamic acid solution prepared in step (2) of Example 1 of the present invention.

[0031] Figure 2 This is a photograph of the sizing agent for quartz fibers prepared in Example 1 of the present invention.

[0032] Figure 3 This is a gel permeation chromatography (GPC) test chromatogram of the polyamate solid obtained in step (3) of Example 1 of the present invention;

[0033] Figure 4 The thermogravimetric analysis (TGA) test results of the sizing agent for quartz fiber prepared in Example 1 of this invention are shown.

[0034] Figure 5 The image shows a differential scanning calorimeter (DSC) test result of the sizing agent for quartz fibers prepared in Example 1 of this invention.

[0035] Figure 6 This is a photograph of the quartz fiber in Example 1 of the present invention after being sized with a sizing agent for 30 minutes.

[0036] Figure 7 Thermogravimetric analysis (TGA) results of the polyamic acid acid waterborne sizing agent in Comparative Example 1 of this invention;

[0037] Figure 8 Thermogravimetric analysis (TGA) results of the polyamic acid acid waterborne sizing agent in Comparative Example 2 of this invention;

[0038] Figure 9 Thermogravimetric analysis (TGA) results of the polyamic acid acid salt aqueous sizing agent in Comparative Example 3 of this invention;

[0039] Figure 10 This is a gel permeation chromatography (GPC) test chromatogram of the polyamate solid obtained in step (3) of Comparative Example 4 of the present invention;

[0040] Figure 11 These are actual photographs of the preparation process of the sizing agent in Comparative Example 5 of this invention;

[0041] Figure 12 These are actual photographs of the preparation process of the sizing agent in Comparative Example 6 of this invention;

[0042] Figure 13 These are actual photographs of the preparation process of the sizing agent in Comparative Example 7 of this invention;

[0043] Figure 14 The image shows a differential scanning calorimeter (DSC) test result of the sizing agent for quartz fiber prepared in Comparative Example 8 of this invention.

[0044] Figure 15This is a differential scanning calorimeter (DSC) test image of the sizing agent for quartz fibers prepared in Comparative Example 9 of the present invention.

[0045] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. It should also be understood that the terminology used in the embodiments of this invention is for describing specific implementations and not for limiting the scope of protection of this invention.

[0048] Unless otherwise defined, all technical and scientific terms used in this invention are consistent with the prior art known to those skilled in the art and the description of this invention. This invention may also be implemented using any prior art methods, devices and materials similar to or equivalent to those described, used or made by means of methods, devices and materials in the embodiments of this invention.

[0049] When numerical ranges are given in the examples, it should be understood that, unless otherwise stated in the invention, both endpoints of each range and any value between the two endpoints may be used. Test methods in the following examples that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers. Unless otherwise specified, all materials or reagents required in the following examples are commercially available.

[0050] To address the problems of poor heat resistance and environmental unfriendliness of existing sizing agents for quartz fibers, this invention provides a method for preparing a sizing agent for quartz fibers, comprising the following steps:

[0051] Aromatic dianhydride was heat-treated to obtain treated aromatic dianhydride; the heat treatment temperature was (T). m -80)~(T m -20)℃, T m This is the melting point of aromatic dianhydrides. Specifically, it is determined by (T... m -80)~(T m Strict heat treatment of aromatic dianhydride at -20℃ can not only fully remove the adsorbed water in the aromatic dianhydride, but also avoid the oxidation or decomposition of the aromatic dianhydride due to excessive temperature; it can effectively eliminate side reactions caused by trace water, while ensuring the activity of monomers.

[0052] An aromatic diamine is dissolved in an aprotic polar organic solvent, and treated aromatic dianhydride is added to it in multiple portions under a chemically inert atmosphere to obtain a mixture; a polycondensation reaction is then carried out to obtain a polyamic acid solution. Specifically, the treated aromatic dianhydride is added 4-5 times. Optionally, the chemically inert atmosphere is a nitrogen or argon atmosphere. Optionally, the polycondensation reaction temperature is 0-40°C. Preferably, the polycondensation reaction temperature is 25-40°C.

[0053] A first tertiary amine is added to a polyamic acid solution, and the mixture is stirred to obtain a polyamate solution. The polyamate solution is then subjected to precipitation and drying treatments to obtain a solid polyamate. Specifically, a process of homogeneous salt formation followed by precipitation is adopted: the tertiary amine is first added to the polyamic acid solution, utilizing the high contact area of ​​the liquid phase to achieve homogeneous modification; this avoids the problem of amine penetration due to the tight packing of molecular chains in the previous precipitation-modification method, and can significantly improve the water solubility and stability of the sizing agent.

[0054] A sizing agent for quartz fibers is obtained by mixing solid polyamic acid salt, a second tertiary amine, and functional additives; the functional additives include at least one of nonionic surfactants and anionic surfactants. Optionally, the functional additives are nonionic surfactants or anionic surfactants.

[0055] Optionally, the nonionic surfactant is polyvinyl alcohol; the anionic surfactant is one or more of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate.

[0056] In this mixture, the sum of the masses of aromatic diamine and aromatic dianhydride is 5-20% of the total mass of the mixture; the molar ratio of aromatic diamine to aromatic dianhydride is 1:1-1.5; the molar ratio of the first tertiary amine to aromatic dianhydride is 2-3:1; the molar ratio of the second tertiary amine to the treated aromatic dianhydride is 1-2:1; and the mass of the functional additive is 1-2% of the mass of the sizing agent for quartz fibers. Preferably, the molar ratio of aromatic diamine to aromatic dianhydride is 1:1-1.06.

[0057] Specifically, a molar ratio of 2 to 3:1 between the first tertiary amine and aromatic dianhydride can minimize the escape of small molecules during subsequent high-temperature treatment while ensuring solubility. This effectively suppresses voids formed inside the polyimide film due to the volatilization and aggregation of small molecules, thereby improving the film's density.

[0058] Preferably, the sum of the masses of the aromatic diamine and the aromatic dianhydride in the mixture is 15% of the mass of the mixture.

[0059] Preferably, the molar ratio of aromatic diamine to aromatic dianhydride is 1:1.04.

[0060] The method for preparing a sizing agent for quartz fibers provided by this invention utilizes a process of "aromatic dianhydride pretreatment + unique polycondensation treatment + mixing of polyamic acid salts, tertiary amines, and functional additives in a specific ratio," which can stably produce a sizing agent for quartz fibers. Furthermore, the entire preparation process of this sizing agent for quartz fibers is an all-aqueous system, and the functional additives used are completely volatilized at high temperatures, leaving no residue, thus combining environmental friendliness with high performance.

[0061] Furthermore, the heat treatment temperature is 200~260℃; the heat treatment atmosphere is a vacuum.

[0062] Further, the aromatic dianhydride includes at least one selected from pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride. Optionally, the aromatic dianhydride is pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, or 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0063] The aromatic diamine includes at least one of 4,4-diaminodiphenyl ether, m-phenylenediamine, and p-phenylenediamine. Optionally, the aromatic diamine is 4,4-diaminodiphenyl ether, m-phenylenediamine, or p-phenylenediamine.

[0064] The aprotic polar organic solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide. Optionally, the aprotic polar organic solvent is N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, or dimethyl sulfoxide.

[0065] Both the first tertiary amine and the second tertiary amine include at least one of triethylamine and N,N-dimethylethanolamine. Optionally, both the first tertiary amine and the second tertiary amine are triethylamine or N,N-dimethylethanolamine.

[0066] Furthermore, the addition method for the step of adding the treated aromatic dianhydride in multiple stages is as follows: add 1 / 2 of the remaining mass of the treated aromatic dianhydride each time, and add the rest in the last stage; and use the obvious lightening of the solution color as the criterion for adding the material.

[0067] Specifically, this addition method employs a color-monitored addition method. It utilizes the mechanism that the yellow-brown charge-transfer complex formed by the treated aromatic dianhydride (electron acceptor) and aromatic diamine (electron donor) fades in color as amide bonds are formed during the reaction, allowing for precise judgment of the reaction progress. The addition is done in 4-5 batches, with each batch containing half the remaining mass of the treated aromatic dianhydride (the last batch contains the entire remaining amount). After the initial addition of the treated aromatic dianhydride, the solution turns yellow-brown due to the formation of the charge-transfer complex. Subsequent batches should only be added after the solution color has changed from yellow-brown to pale yellow and noticeably faded.

[0068] Furthermore, the polycondensation reaction duration is 4–6 hours. Specifically, controlling the polycondensation reaction duration to 4–6 hours avoids both low polymerization degree due to excessively short time and degradation due to excessively long time, thereby ensuring that the polymer possesses extremely high molecular weight and temperature resistance potential.

[0069] Further, the precipitation treatment method includes: adding a polyamate solution to a precipitant; the precipitant includes ethyl acetate. Optionally, the precipitation treatment method involves adding a polyamate solution to a precipitant; the precipitant includes ethyl acetate. Specifically, the polyamate solution is added to ethyl acetate for precipitation, the solid is collected by filtration and vacuum drying to obtain solid polyamate. Optionally, the criterion for determining the end of the precipitation treatment is that no more solid precipitates in the ethyl acetate.

[0070] Furthermore, the drying temperature is 30~50℃. Specifically, drying at temperatures below 30℃ results in a slow drying rate; temperatures above 50℃ may cause imidization of polyamate solids, leading to premature cyclization and poor water solubility.

[0071] The present invention also provides a sizing agent for quartz fibers prepared by the above preparation method, wherein the solid content of the sizing agent for quartz fibers is 0.5~2 wt.%. Specifically, if the solid content of the sizing agent for quartz fibers is less than 0.5 wt%, the lubrication effect on quartz fibers is poor, and quartz fibers are prone to fuzzing; if the solid content of the sizing agent for quartz fibers exceeds 2 wt%, the quartz fibers will harden, affecting processing performance.

[0072] The sizing agent for quartz fibers provided by this invention has extremely high molecular weight and temperature resistance potential, and the glass transition temperature of the sizing agent for quartz fibers is above 300°C.

[0073] The present invention also provides an application of the above-mentioned sizing agent for quartz fibers in the sizing treatment of quartz fibers, wherein quartz fibers are immersed in the sizing agent for quartz fibers and then subjected to drying treatment and three-gradient curing treatment in sequence; the temperatures of the three-gradient curing treatment are 150~200℃, 250~300℃ and above 350℃ in sequence.

[0074] Specifically, the low-temperature, long-duration drying at 150-200℃ prevents coating agglomeration; the gradient design at medium-high temperatures of 250-300℃ and above 350℃ creates a closed-loop reaction, further regulating molecular chain dynamics and inducing rearrangement and close packing of polyimide molecular chains. With this specific process, thermal induction endows the molecular chains with suitable mobility, promoting the orderly arrangement and close packing of polyimide molecular chains on the fiber surface; synergistically with sizing agents for quartz fibers, this results in a high-performance protective layer on the quartz fiber surface capable of withstanding temperatures above 350℃.

[0075] Optionally, the treatment time is 1-2 hours for 150-200℃; 0.5-1 hour for 250-300℃; and 0.5-1 hour for treatment above 350℃.

[0076] Applying this sizing agent to the quartz fiber sizing process can form a high-performance protective layer on the quartz fiber surface that can withstand temperatures above 350°C, thus broadening the long-term working temperature and processing stability range of quartz fiber reinforced polymer matrix composites, and showing broad application prospects.

[0077] Furthermore, the drying temperature is 80~100℃. Specifically, a long drying process at 80~100℃ is performed first to prevent the solvent from evaporating too quickly and causing the sizing agent microspheres of the quartz fiber to agglomerate.

[0078] Optionally, the treatment time at 80~100℃ is 0.5~1h.

[0079] To further illustrate the present invention, the following examples are provided:

[0080] Example 1

[0081] (1) Heat treatment of aromatic dianhydride: Take out 3.03g (0.0102mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and vacuum bake at 220℃ for 4h to fully remove adsorbed water and maintain activity.

[0082] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C), and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a pale yellow, the next batch was added. A total of 4 batches were added. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain the following result. Figure 1 The sample is a homogeneous, transparent, low-viscosity polyamic acid (PAA) solution with a mass fraction of 10%.

[0083] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 2.06 g (0.0204 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 30°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, obtaining a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable sizing agent for quartz fibers (solid content 1.15 wt%). The results are as follows. Figure 2 As shown.

[0084] Polyamate solids obtained by gel permeation chromatography (GPC), such as Figure 3 As shown, the number-average molecular weight is 78,769, the weight-average molecular weight is 100,039, and the dispersion coefficient is 1.27. This indicates that the molecular weight is uniform and relatively large, which is the basis for its good temperature resistance.

[0085] Thermogravimetric analysis (TGA) showed that the temperature at which the sizing agent for quartz fiber loses 5% of its weight can reach 498℃. Figure 4 As shown, it exhibits good high-temperature resistance, meeting the processing requirements of quartz fiber reinforced polymer matrix composites.

[0086] Differential scanning calorimetry (DSC) analysis showed that the glass transition temperature of the sizing agent for quartz fibers can reach 313℃. Figure 5 As shown, it has good thermal stability.

[0087] (4) Finally, immerse the quartz fiber thoroughly in the sizing agent for quartz fiber for 30 minutes. Figure 6 After being removed, the material is dried in a forced-air oven at 100°C for 1 hour. Then, it is heated in a muffle furnace at 150°C for 1 hour, 250°C for 1 hour, and 350°C for 1 hour until imidization is complete, thus obtaining the quartz fiber reinforced polymer matrix composite material.

[0088] Example 2

[0089] (1) Heat treatment of aromatic dianhydride: Take out 3.03g (0.0102mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and vacuum bake at 280℃ for 4h to fully remove adsorbed water and maintain activity.

[0090] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 23.46 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 25 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. A total of 4 batches were added. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 15%.

[0091] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 3.09 g (0.0306 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 50°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable sizing agent for quartz fibers (solid content 1.31 wt%).

[0092] Thermogravimetric analysis (TGA) showed that the temperature at which the sizing agent for quartz fiber loses 5% of its weight can reach 490℃, and differential scanning calorimetry (DSC) showed that the glass transition temperature of the sizing agent for quartz fiber can reach 310℃.

[0093] (4) Finally, the quartz fiber is fully immersed in the quartz fiber sizing agent for 30 minutes. After taking it out, it is dried in a forced-air oven at 80°C for 1 hour. After taking it out, it is heated in a muffle furnace at 200°C for 1 hour, 300°C for 1 hour, and 350°C for 1 hour until imidization is complete. The quartz fiber reinforced polymer matrix composite material can then be obtained.

[0094] Example 3

[0095] (1) Heat treatment of aromatic dianhydride: Take out 2.18g (0.01mol) of pyromellitic dianhydride (PMDA) monomer (melting point 290℃) that was sealed and stored, place it in a forced-air oven, and bake it under vacuum at 210℃ for 4h to fully remove adsorbed water and maintain activity.

[0096] (2) Synthesis of polyamic acid: 1.60 g (0.01 mol) of diamine 4,4-diaminodiphenyl ether (ODA) was added to a 100 ml three-necked flask, and 28.53 g of N-methylpyrrolidone (NMP) was added. The three-necked flask was placed in a water bath (temperature controlled at 30 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. A total of 5 batches were added. A condenser and a three-way valve were attached to the three-necked flask, and nitrogen gas was evacuated to allow the reaction to proceed for 6 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 12%.

[0097] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 2.02 g (0.02 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 40°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 500.00 g of deionized water to prepare an aqueous solution containing 1.50 g (0.015 mol) of sodium dodecyl sulfonate and 5.00 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable sizing agent for quartz fibers (solid content 1.5 wt%).

[0098] Thermogravimetric analysis (TGA) showed that the temperature at which the sizing agent for quartz fiber loses 5% of its weight can reach 495℃, and differential scanning calorimetry (DSC) showed that the glass transition temperature of the sizing agent for quartz fiber can reach 306℃.

[0099] (4) Finally, the quartz fiber is fully immersed in the quartz fiber sizing agent for 30 minutes. After taking it out, it is dried in a forced-air oven at 90°C for 1 hour. After taking it out, it is heated in a muffle furnace at 180°C for 1 hour, 280°C for 1 hour, and 380°C for 1 hour until imidization is complete, and the quartz fiber reinforced polymer matrix composite material can be obtained.

[0100] Example 4

[0101] (1) Aromatic dianhydride heat treatment: Take out 3.15g (0.0106mol) of 3,3'4,4'-biphenyltetracarboxylic acid (BPDA) monomer (melting point 290℃) that was sealed and stored, place it in a forced-air oven, and vacuum bake at 250℃ for 4h to fully remove adsorbed water and maintain activity.

[0102] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine (m-PDA) was added to a 100 ml three-necked flask, and 50.00 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 25 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. A total of 5 batches were added. A condenser and a three-way valve were attached to the three-necked flask, and nitrogen gas was evacuated to allow the reaction to proceed for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with a low viscosity and a mass fraction of 8%.

[0103] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 3.03 g (0.03 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 50°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 700.00 g of deionized water to prepare an aqueous solution containing 1.40 g of polyvinyl alcohol and 1.40 g of sodium dodecylbenzene sulfonate. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable sizing agent for quartz fibers (solid content 2.0 wt%).

[0104] Thermogravimetric analysis (TGA) showed that the temperature at which the sizing agent for quartz fiber loses 5% of its weight can reach 480℃, and differential scanning calorimetry (DSC) showed that the glass transition temperature of the sizing agent for quartz fiber can reach 303℃.

[0105] (4) Finally, the quartz fiber is fully immersed in the quartz fiber sizing agent for 30 minutes. After taking it out, it is dried in a forced-air oven at 100°C for 1 hour. After taking it out, it is heated in a muffle furnace at 190°C for 1 hour, 290°C for 1 hour, and 390°C for 1 hour until imidization is complete. The quartz fiber reinforced polymer matrix composite material can then be obtained.

[0106] Example 5

[0107] (1) Heat treatment of aromatic dianhydride: Take out 3.03g (0.0102mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and vacuum bake at 220℃ for 4h to fully remove adsorbed water and maintain activity.

[0108] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. The addition was done in a total of 4 batches. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 15%.

[0109] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 2.02 g (0.02 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 45°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 550.00 g of deionized water to prepare an aqueous solution containing 0.55 g (0.0055 mol) of sodium dodecyl sulfate and 5.50 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable sizing agent for quartz fibers (solid content 1.8 wt%).

[0110] Thermogravimetric analysis (TGA) showed that the temperature at which the sizing agent for quartz fiber loses 5% of its weight can reach 488℃, and differential scanning calorimetry (DSC) showed that the glass transition temperature of the sizing agent for quartz fiber can reach 301℃.

[0111] (4) Finally, the quartz fiber is fully immersed in the sizing agent for quartz fiber for 30 minutes. After taking it out, it is dried in a forced-air oven at 100°C for 1 hour. After taking it out, it is heated in a muffle furnace at 150°C for 1 hour, 250°C for 1 hour, and 350°C for 1 hour until imidization is complete, and the quartz fiber reinforced polymer matrix composite material can be obtained.

[0112] Comparative Example 1

[0113] Aromatic dianhydride heat treatment is not performed.

[0114] (1) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. 3.03 g (0.0102 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride monomer that had not been pretreated was taken out and added in batches of half the remaining amount. When the solution changed from a distinct yellow-brown to a pale yellow, the next batch was added. The addition was done in 4 batches. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 h to obtain a homogeneous, transparent, low-viscosity polyamic acid (PAA) solution with a mass fraction of 10%.

[0115] (2) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 2.06 g (0.0204 mol) of triethylamine, and stir thoroughly. Then add ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 30°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable thermoplastic polyamic acid salt aqueous sizing agent.

[0116] (3) Finally, the quartz fiber is fully immersed in the polyamic acid water-based sizing agent for 30 minutes. After taking it out, it is dried in a forced-air oven at 100°C for 1 hour. After taking it out, it is heated in a muffle furnace at 150°C for 1 hour, 250°C for 1 hour, and 350°C for 1 hour until imidization is complete. The quartz fiber treated with water-soluble polyimide precursor sizing agent can be obtained.

[0117] The polyamic acid salt aqueous sizing agent loses 5% at a temperature of 226℃. Figure 7 As shown, the temperature resistance decreases significantly.

[0118] Comparative Example 2

[0119] The heat treatment temperature for aromatic dianhydride is 180℃.

[0120] (1) Heat treatment of aromatic dianhydride: Take out 3.03 g (0.0102 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and heat it at 180℃ (T m Vacuum baking at -120℃ for 4 hours.

[0121] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. The addition was done in a total of 4 batches. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 10%.

[0122] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 2.06 g (0.0204 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 30°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable thermoplastic polyamic acid salt aqueous sizing agent.

[0123] (4) Finally, the quartz fiber is fully immersed in the polyamic acid water-based sizing agent for 30 minutes. After taking it out, it is dried in a forced-air oven at 100°C for 1 hour. After taking it out, it is heated in a muffle furnace at 150°C for 1 hour, 250°C for 1 hour, and 350°C for 1 hour until imidization is complete. The quartz fiber treated with water-soluble polyimide precursor sizing agent can be obtained.

[0124] Aromatic dianhydrides in <(T m After heat treatment in the range of -80℃, the temperature at which the polyamic acid acid salt water-based sizing agent loses 5% of its weight is 440℃. Figure 8 As shown, the temperature resistance decreases significantly.

[0125] Comparative Example 3

[0126] The heat treatment temperature for aromatic dianhydride is 290℃.

[0127] (1) Heat treatment of aromatic dianhydride: Take out 3.03 g (0.0102 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and heat it at 290℃ (T m Vacuum baking at -10℃ for 4 hours.

[0128] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. The addition was done in a total of 4 batches. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 10%.

[0129] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 2.06 g (0.0204 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 30°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable thermoplastic polyamic acid salt aqueous sizing agent.

[0130] (4) Finally, the quartz fiber is fully immersed in the polyamic acid water-based sizing agent for 30 minutes. After taking it out, it is dried in a forced-air oven at 100°C for 1 hour. After taking it out, it is heated in a muffle furnace at 150°C for 1 hour, 250°C for 1 hour, and 350°C for 1 hour until imidization is complete. The quartz fiber treated with water-soluble polyimide precursor sizing agent can be obtained.

[0131] Dihydric acid in > (T) m After pretreatment at a temperature range of -20°C, the polyamic acid aqueous sizing agent lost 5% of its weight at a temperature of 413°C. Figure 9 As shown, the temperature resistance decreases significantly.

[0132] Comparative Example 4

[0133] The treated aromatic dianhydride is not monitored by colorimetry; that is, it is added all at once without being added in batches.

[0134] (1) Heat treatment of aromatic dianhydride: Take out 3.03g (0.0102mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and vacuum bake at 220℃ for 4h to fully remove adsorbed water and maintain activity.

[0135] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C), and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added directly. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 h to obtain a homogeneous, transparent, low-viscosity polyamic acid (PAA) solution with a mass fraction of 10%.

[0136] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 2.06 g (0.0204 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 30°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable thermoplastic polyamic acid salt aqueous sizing agent.

[0137] (4) Finally, the quartz fiber is fully immersed in the polyamic acid water-based sizing agent for 30 minutes. After taking it out, it is dried in a forced-air oven at 100°C for 1 hour. After taking it out, it is heated in a muffle furnace at 150°C for 1 hour, 250°C for 1 hour, and 350°C for 1 hour until imidization is complete. The quartz fiber treated with water-soluble polyimide precursor sizing agent can be obtained.

[0138] Polyamate solids obtained by GPC testing, such as Figure 10 As shown, the weight-average molecular weight is 18781, the number-average molecular weight is 10783, and the dispersion coefficient is 1.47. The molecular weight is significantly reduced, and the distribution is also widened.

[0139] Comparative Example 5

[0140] Change the order of addition of the first tertiary amine; that is, perform precipitation treatment first and then add the tertiary amine.

[0141] (1) Heat treatment of aromatic dianhydride: Take out 3.03g (0.0102mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and vacuum bake at 220℃ for 4h to fully remove adsorbed water and maintain activity.

[0142] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. The addition was done in a total of 4 batches. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 10%.

[0143] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add ethyl acetate to precipitate, then add 2.06 g (0.0204 mol) of triethylamine to the precipitate for modification, then add water and stir thoroughly. However, the precipitate agglomerates and cannot be dissolved. Figure 11 As shown.

[0144] Comparative Example 6

[0145] The molar ratio of the first tertiary amine to the treated aromatic dianhydride is 1:1.

[0146] (1) Heat treatment of aromatic dianhydride: Take out 3.03g (0.0102mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and vacuum bake at 220℃ for 4h to fully remove adsorbed water and maintain activity.

[0147] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. The addition was done in a total of 4 batches. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 10%.

[0148] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 1.03 g (0.0102 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 30°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, obtaining a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve. Even after 3 h, 1 / 3 of the solid remains, indicating that the dissolution rate is too slow. Figure 12 As shown.

[0149] Comparative Example 7

[0150] The molar ratio of the first tertiary amine to the treated aromatic dianhydride is 4:1.

[0151] (1) Heat treatment of aromatic dianhydride: Take out 3.03g (0.0102mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and vacuum bake at 220℃ for 4h to fully remove adsorbed water and maintain activity.

[0152] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. The addition was done in a total of 4 batches. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 10%.

[0153] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 4.12 g (0.0416 mol) of triethylamine, and stir thoroughly. Then add ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 30°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable thermoplastic polyamic acid salt aqueous sizing agent.

[0154] (4) Pour the sizing agent into a glass petri dish (simulating sizing for easy observation), place it in a forced-air oven and air dry at 100℃ for 1 hour. After removing it, heat it in a muffle furnace at 150℃ for 1 hour, 250℃ for 1 hour, and 350℃ for 1 hour until imidization is complete. It was found that the surface of the resulting membrane had many bubbles and was uneven (triethylamine small molecules escaped). Figure 13 As shown.

[0155] Comparative Example 8

[0156] The application process uses only a single gradient curing treatment; that is, sizing treatment at 350℃ for 4 hours.

[0157] (1) Heat treatment of aromatic dianhydride: Take out 3.03g (0.0102mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and vacuum bake at 220℃ for 4 hours to fully remove adsorbed water and maintain activity.

[0158] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. The addition was done in a total of 4 batches. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 10%.

[0159] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 2.06 g (0.0204 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 30°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable sizing agent for quartz fibers (solid content 1.15 wt%).

[0160] (4) Finally, the quartz fiber is fully immersed in the sizing agent for quartz fiber for 30 minutes, and then heated directly in a muffle furnace at 350 degrees Celsius for 4 hours until imidization is complete, so as to obtain quartz fiber treated with sizing agent for quartz fiber.

[0161] The glass transition temperature of the sizing agent for quartz fibers was determined to be 304.6℃ using differential scanning calorimetry (DSC). Figure 14 As shown, there has been a decrease.

[0162] Comparative Example 9

[0163] The application process employs a two-gradient curing treatment: sizing at 250℃ for 2 hours and sizing at 350℃ for 2 hours.

[0164] (1) Heat treatment of aromatic dianhydride: Take out 3.03g (0.0102mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride that has been sealed and stored, place it in a forced-air drying oven, and vacuum bake at 220℃ for 4h to fully remove adsorbed water and maintain activity.

[0165] (2) Synthesis of polyamic acid: 1.08 g (0.01 mol) of the diamine m-phenylenediamine was added to a 100 ml three-necked flask, and 36.99 g of N,N-dimethylacetamide (DMAc) was added. The three-necked flask was placed in a water bath (temperature controlled at 40 °C) and stirred with a mechanical stirrer until a clear and transparent solution was obtained. The aromatic diamine treated in step (1) was added in multiple batches, with only half of the remaining portion added each time. When the solution changed from a distinct yellow-brown to a light yellow, the next batch was added. The addition was done in a total of 4 batches. A condenser and a three-way valve were attached to the three-necked flask, and the mixture was evacuated and reacted for 4 hours to obtain a homogeneous, transparent polyamic acid (PAA) solution with low viscosity and a mass fraction of 10%.

[0166] (3) Preparation of sizing agent: Pour the polyamic acid solution into a beaker, add 2.06 g (0.0204 mol) of triethylamine, and stir thoroughly. Then pour in ethyl acetate until precipitation is complete, filter, transfer the precipitate to a petri dish and place it in a vacuum oven at 30°C to dry thoroughly for 24 h until the organic solvent is fully evaporated, to obtain a pale yellow polyamic acid salt solid. At the same time, add 617.76 g of deionized water to prepare an aqueous solution containing 1.03 g (0.0102 mol) of triethylamine and 6.24 g of polyvinyl alcohol. Pour the thoroughly dried polyamic acid salt solid into the prepared solution, and stir thoroughly in a three-necked flask to dissolve for 1 h to obtain a homogeneous and stable sizing agent for quartz fibers (solid content 1.15 wt%).

[0167] (4) Finally, the quartz fiber is fully immersed in the sizing agent for quartz fiber for 30 minutes. After taking it out, it is kept in a muffle furnace at 250℃ for 2 hours and 350℃ for 2 hours until imidization is complete. The quartz fiber sizing agent for quartz fiber is then obtained.

[0168] The glass transition temperature of the sizing agent for quartz fibers was determined to be 300.2℃ using differential scanning calorimetry (DSC). Figure 15 As shown, there has been a decrease.

[0169] In summary, the above-described technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a sizing agent for quartz fibers, characterized in that, Including the following steps: Aromatic dianhydride is heat-treated to obtain treated aromatic dianhydride; the heat treatment temperature is (T m -80)~(T m -20)℃, T m The melting point of the aromatic dianhydride; Aromatic diamine is dissolved in an aprotic polar organic solvent, and the treated aromatic dianhydride is added to it in multiple portions under a chemically inert atmosphere to obtain a mixture; a polycondensation reaction is carried out to obtain a polyamic acid solution. The aprotic polar organic solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide; The process of adding the treated aromatic dianhydride in multiple stages includes: adding half of the remaining mass of the treated aromatic dianhydride each time, and adding the rest in the last stage; and using a significant lightening of the solution color as the criterion for adding the material. A first tertiary amine is added to the polyamic acid solution, and the mixture is stirred to obtain a polyamic acid salt solution. The polyamic acid salt solution was subjected to precipitation and drying treatments in sequence to obtain polyamic acid salt solid; The polyamic acid salt solid, the second tertiary amine, and the functional additives are mixed to obtain a sizing agent for quartz fibers; the functional additives include at least one of nonionic surfactants and anionic surfactants. In the mixture, the sum of the masses of the aromatic diamine and the aromatic dianhydride is 5-20% of the mass of the mixture; the molar ratio of the aromatic diamine to the aromatic dianhydride is 1:1-1.5; the molar ratio of the first tertiary amine to the aromatic dianhydride is 2-3:1; the molar ratio of the second tertiary amine to the aromatic dianhydride is 1-2:1; and the mass of the functional additive is 1-2% of the mass of the sizing agent for quartz fiber.

2. The preparation method according to claim 1, characterized in that, The heat treatment temperature is 200~260℃; the heat treatment atmosphere is a vacuum.

3. The preparation method according to claim 1, characterized in that, The aromatic dianhydride includes at least one of pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride. The aromatic diamine includes at least one of 4,4-diaminodiphenyl ether, m-phenylenediamine, and p-phenylenediamine; Both the first tertiary amine and the second tertiary amine include at least one of triethylamine and N,N-dimethylethanolamine.

4. The preparation method according to claim 1, characterized in that, The duration of the polycondensation reaction is 4-6 hours.

5. The preparation method according to claim 1, characterized in that, The precipitation treatment method includes adding the polyamic acid salt solution to a precipitant; the precipitant includes ethyl acetate.

6. The preparation method according to claim 1, characterized in that, The drying process is carried out at a temperature of 30~50℃.

7. A sizing agent for quartz fibers prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The solid content of the sizing agent used for the quartz fiber is 0.5~2 wt.%.

8. The application of the sizing agent for quartz fibers as described in claim 7 in the sizing treatment of quartz fibers, characterized in that, Quartz fibers are impregnated in a sizing agent for quartz fibers, and then subjected to drying and three-gradient curing treatments in sequence. The temperatures for the three-gradient curing process are 150~200℃, 250~300℃, and above 350℃, respectively.

9. The application according to claim 8, characterized in that, The drying temperature is 80~100℃.

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