Complex modified starch for secondary sizing of electronic glass fibers and method for its production

Abstract

The present application relates to electronic glass fiber sizing material technical field, disclose a kind of composite modified starch for electronic glass fiber secondary sizing and its preparation method. With deionized water, high amylose starch, sodium sulfate, sodium hydroxide solution, acrylamide, vinyl acetate and oxidant as main raw material, and introduce low ash hydroxypropyl trimethyl ammonium hydroxypropyl sulfonic acid double ion polyglycerol borate glass affinity modification compound and methoxy polyethylene glycol succinic acid monoester aminopropyl silane amide low ash flexible film-forming modification compound, by suspension dispersion, carbamoyl ethyl modification, composite esterification modification, oxidation viscosity reduction, neutralization, centrifugation, washing, drying and crushing are prepared. The obtained composite modified starch has the characteristics of low ash, good film-forming property, sizing film flexible and transparent, viscosity stability, strong affinity with electronic glass fiber surface, easy desizing and low residual.

Description

Technical Field

[0001] This invention relates to the field of sizing materials for electronic glass fibers, specifically to a composite modified starch for secondary sizing of electronic glass fibers and its preparation method. Background Technology

[0002] Electronic glass fiber is a crucial basic material in electronic fabrics, copper-clad laminates, and insulating reinforcement materials. Its production process requires a sizing system to improve fiber bundle cohesion, abrasion resistance, flexibility, and weaving permeability. Existing resizing materials for electronic glass fiber typically consist of starch, polyvinyl alcohol, acrylic polymers, polyester emulsions, or a blend of various film-forming aids. Among these, starch-based materials have attracted attention due to their wide availability, low price, biodegradability, ease of desizing, and low environmental impact. High-amylose starch exhibits good film-forming properties and low ash content, leaving minimal residue after ignition, theoretically suitable for the low residue, low pollution, and easily treatable wastewater requirements of electronic glass fiber. However, unmodified natural starch suffers from insufficient dispersion stability, large viscosity fluctuations in the paste, brittle sizing film, and limited adhesion to the glass fiber surface. Direct use of unmodified natural starch in the resizing of electronic glass fiber can easily lead to defects such as uneven sizing film, increased fiber hairiness, weaving friction damage, decreased fabric smoothness, and instability during the desizing process.

[0003] To improve the application performance of starch, existing technologies often employ methods such as etherification, esterification, oxidation, acid hydrolysis, crosslinking, or modification with composite auxiliaries to adjust the hydrophilicity, film-forming properties, viscosity, and degradation performance of starch. Acrylamide can undergo carbamoyl ethylation with starch hydroxyl groups under alkaline conditions, improving the hydrophilicity of starch molecular chains and the binding performance of the sizing film; vinyl acetate can be used for starch esterification modification, improving the flexibility and transparency of the sizing film; oxidants can further adjust the structure of starch molecular chains, reduce the viscosity of the paste, and improve desizing performance. However, single chemical modification is usually insufficient to simultaneously meet the requirements of low ash content, low residue, high film-forming uniformity, good interfacial affinity, and stable viscosity required for sizing electronic glass fibers. In particular, the surface of glass fibers is rich in silanol groups, and the interfacial interaction between ordinary starch molecules and these molecules is weak, making it difficult to form a continuous sizing film on the fiber surface that combines flexibility, protection, and easy desizing; simply increasing the amount of film-forming agent may result in an overly hard sizing film, increased desizing load, increased loss on ignition residue, and increased wastewater treatment pressure. Therefore, the field of electronic glass fiber re-sizing still needs a composite modified starch material with natural high amylose as the main component, and which has low ash content and high interfacial compatibility, so that it can improve the stability of slurry, fiber surface adhesion, slurry film flexibility and weaving protection while maintaining the advantages of being green, easy to degrade and easy to burn off. Summary of the Invention

[0004] The purpose of this invention is to provide a composite modified starch for secondary sizing of electronic glass fibers and its preparation method, which solves the technical problems of existing starch sizing agents such as unstable viscosity, brittle film formation, poor affinity with glass fibers, excessive hairiness, and high desizing residue.

[0005] The present invention achieves the above objectives through the following technical solutions: A method for preparing composite modified starch for secondary sizing of electronic glass fibers, comprising the following steps: S1. By weight, 150.0-300.0 parts of deionized water, 100.0 parts of high amylose, and 5.0-12.0 parts of sodium sulfate are mixed to obtain a high amylose suspension; 0.2-1.2 parts of a low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modifying compound are added to the high amylose suspension, and mixing is continued to obtain an interface affinity modified starch suspension; 50.0-100.0 parts of sodium hydroxide solution and 5.0-15.0 parts of acrylamide are added to the interface affinity modified starch suspension, and the mixture is reacted at 30-55℃ to obtain a carbamoyl ethyl modified starch suspension; S2. Adjust the pH of the carbamoyl ethyl modified starch suspension to 9.0-10.0, add 0.2-1.5 parts of methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide low-ash flexible film-forming modifying compound, continue mixing, add 3.0-10.0 parts of vinyl acetate, and react at 35-50℃ to obtain a composite esterified modified starch suspension; adjust the pH of the composite esterified modified starch suspension to 8.0-9.0, add 0.5-3.5 parts of oxidant, continue the reaction, adjust the pH to 6.0-7.0, centrifuge, wash, dry, and pulverize.

[0006] In this invention, during the preparation of the composite modified starch for secondary sizing of electronic glass fibers, deionized water forms a suspension of high amylose starch. Sodium sulfate adjusts the ionic strength of the system and inhibits excessive swelling of the high amylose particles, ensuring that subsequent reactions mainly occur on the particle surface under limited swelling conditions. After the addition of a low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modifier, its polyhydroxy, diionic, and borate structures are distributed on the surface of the high amylose particles through hydrogen bonding, ionic interactions, and dynamic complexation, improving suspension dispersibility. Upon addition of sodium hydroxide solution, the hydroxyl groups of the high amylose are partially deprotonated and activated. Under alkaline conditions, the carbon-carbon double bonds in the acrylamide accept the attack of the activated high amylose hydroxyl groups, undergoing Michael addition, which allows the carbamoyl ethyl structure to integrate into the high amylose backbone, generating a carbamoyl ethyl modified starch suspension. Subsequently, the conditions were adjusted to a weakly alkaline state, and a low-ash, flexible film-forming modifying compound, methoxy polyethylene glycol succinate monoester-aminopropylsilaneamide, was added. Its polyether segments, amide structure, and silanol active structure formed a composite interfacial layer with the carbamoyl ethyl modified starch suspension. After the addition of vinyl acetate, the vinyl acetate acetylated the hydroxyl groups of the high amylose starch. Simultaneously, the self-hydrolysis of vinyl acetate and the reverse hydrolysis of starch acetate constituted competing side reactions. Therefore, a weakly alkaline range is beneficial for balancing reaction efficiency and side reaction control. The composite esterified modified starch suspension was then adjusted to a weakly alkaline state suitable for the action of the oxidant. Sodium hypochlorite or hydrogen peroxide was used to gently oxidize the starch segments, converting some hydroxyl groups to carbonyl or carboxyl groups and reducing the viscosity of the paste. Finally, the solution was adjusted to near neutral, centrifuged, washed, dried, and pulverized to obtain the composite modified starch for secondary sizing of electronic glass fibers.

[0007] According to a preferred embodiment of the present invention, in step S1, the high amylose starch is high amylose tapioca starch or high amylose corn starch; the reaction time at 30-55°C is 12-24 hours.

[0008] According to a preferred embodiment of the present invention, in step S2, the reaction time at 35-50°C is 2-6 hours; the oxidant is sodium hypochlorite or hydrogen peroxide.

[0009] According to a preferred embodiment of the present invention, the preparation method of the low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound includes: A1. By weight, mix 100.0 parts of polyglycerol-3 and 180.0-240.0 parts of deionized water. Under nitrogen protection, add 20.0-35.0 parts of an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride, and add sodium hydroxide aqueous solution dropwise to adjust the pH to 10.5-11.5. React at 45-55℃. Add 12.0-24.0 parts of sodium 3-chloro-2-hydroxypropylsulfonate, adjust the pH to 10.0-11.0, and react at 50-60℃. Add 3.0-7.0 parts of boric acid and 5.0-10.0 parts of glycerol, adjust the pH to 8.2-8.8, and react at 35-40℃ to obtain a diionized polyglycerol borate reaction solution. A2. Adjust the pH of the diionic polyglycerol borate reaction solution to 8.0-8.5, concentrate under reduced pressure at 45-55℃, dry and pulverize.

[0010] In the preparation of the low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borosilicate glass affinity modified compound, polyglycerol-3, as a polyol backbone containing multiple hydroxyl groups, forms a homogeneous aqueous phase system in deionized water. After adding an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride and dropwise adding an aqueous solution of sodium hydroxide, the system is under alkaline conditions. Some of the hydroxyl groups in polyglycerol-3 are deprotonated and activated. Under alkaline conditions, 3-chloro-2-hydroxypropyltrimethylammonium chloride dechlorinates and transforms into a highly reactive epoxide structure, which then undergoes ring-opening etherification with the hydroxyl groups of polyglycerol-3, introducing an N-hydroxypropyltrimethylammonium structure onto the polyglycerol-3 backbone. Subsequently, sodium 3-chloro-2-hydroxypropylsulfonate was added. Under continuous alkaline and heating conditions, the unreacted hydroxyl groups in polyglycerol-3 continued to undergo ring-opening etherification with sodium 3-chloro-2-hydroxypropylsulfonate via an epoxy intermediate, incorporating the hydroxypropylsulfonic acid structure into the polyglycerol-3 backbone. This resulted in a diionic polyglycerol structure containing both N-hydroxypropyltrimethylammonium and hydroxypropylsulfonic acid structures. After the addition of boric acid and glycerol, boric acid formed a reversible borate complex with adjacent hydroxyl groups in polyglycerol-3 and glycerol, yielding a diionic polyglycerol borate reaction solution. This reaction solution was concentrated under reduced pressure, dried, and pulverized under weakly alkaline conditions to obtain a low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound. In this process, the N-hydroxypropyltrimethylammonium structure enhanced polar adsorption and wetting, the hydroxypropylsulfonic acid structure improved water dispersion stability, the polyglycerol-3 polyhydroxy backbone enhanced hydrogen bonding, and the borate structure strengthened the dynamic complexation between the polyhydroxy systems.

[0011] According to a preferred embodiment of the present invention, in step A1, the reaction time is 3-5 hours at 45-55°C; 4-6 hours at 50-60°C; and 2-4 hours at 35-40°C.

[0012] According to a preferred embodiment of the present invention, in step A2, the drying temperature is 50-70°C.

[0013] According to a preferred embodiment of the present invention, the preparation method of the methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide low-ash flexible film-forming modified compound includes: B1. By weight, mix 100.0 parts of methoxy polyethylene glycol-750, 10.0-18.0 parts of succinic anhydride, 0.2-0.6 parts of 4-dimethylaminopyridine, and 80.0-120.0 parts of anhydrous acetone, and react under nitrogen protection at 50-58°C to obtain a methoxy polyethylene glycol succinate monoester reaction solution; distill the methoxy polyethylene glycol succinate monoester reaction solution under reduced pressure, add 160.0-220.0 parts of a mixed solvent of ethanol and water, and add... Add 8.0-14.0 parts of N-hydroxysuccinimide and 12.0-20.0 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, adjust the pH to 4.5-5.5, and activate at 20-30℃ to obtain an activated carboxyl polyether reaction solution; add 8.0-16.0 parts of 3-aminopropyltriethoxysilane dropwise to the activated carboxyl polyether reaction solution, adjust the pH to 6.0-7.0, and react at 25-35℃ to obtain a polyether silane amide reaction solution; B2. Concentrate the polyether silaneamide reaction solution under reduced pressure at 40-50℃, then dry and pulverize.

[0014] In this invention, in the preparation of the methoxy polyethylene glycol succinate monoester-aminopropylsilaneamide low-ash flexible film-forming modified compound, the terminal hydroxyl group of methoxy polyethylene glycol-750 undergoes ring-opening esterification with succinic anhydride in the presence of 4-dimethylaminopyridine, generating a methoxy polyethylene glycol succinate monoester reaction solution containing a polyether flexible segment and a terminal carboxyl group. After removing anhydrous acetone by vacuum distillation, a mixed solvent of ethanol and water, N-hydroxysuccinimide, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride are added. Under weakly acidic conditions, the carboxyl group in the methoxy polyethylene glycol succinate monoester is activated, forming an activated carboxyl polyether reaction solution containing a succinimide active ester structure. Subsequently, 3-aminopropyltriethoxysilane is added dropwise and adjusted to near-neutral conditions. The amino group in 3-aminopropyltriethoxysilane undergoes amidation coupling with the activated carboxyl group, forming a polyether silaneamide reaction solution. In this stage, the mixed solvent of ethanol and water causes partial hydrolysis of the ethoxysilane structure in 3-aminopropyltriethoxysilane, generating a silanol structure with interfacial reactivity. However, this should not be described as complete condensation in this step. After vacuum concentration, drying, and pulverization, the polyether silane amide reaction solution yields a methoxy polyethylene glycol succinate monoester-aminopropylsilane amide low-ash flexible film-forming modified compound. In this compound, the methoxy polyethylene glycol-750 segment imparts hydrophilic spreading and flexibility to the film, the succinate monoester structure provides carboxyl coupling sites, the amide structure improves connection stability, and the silanol structure formed by the hydrolysis of 3-aminopropyltriethoxysilane facilitates hydrogen bonding and condensation with the silanol groups on the glass fiber surface, thereby improving the interfacial compatibility of the composite modified starch on the electronic glass fiber surface.

[0015] According to a preferred embodiment of the present invention, in step B1, the reaction time at 50-58°C is 4-6 hours; the activation time at 20-30°C is 1-2 hours; and the reaction time at 25-35°C is 5-8 hours.

[0016] According to a preferred embodiment of the present invention, in step B2, the drying temperature is 45-65°C.

[0017] The present invention also provides a composite modified starch for secondary sizing of electronic glass fibers, prepared according to the method described above.

[0018] The beneficial effects of this invention are as follows: This invention uses deionized water, high amylose, and sodium sulfate to form a high amylose suspension, allowing the high amylose to participate in subsequent reactions in a relatively stable suspension state, reducing the impact of excessive swelling and viscosity abrupt changes on sizing performance. The addition of a low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borosilicate glass affinity modifier improves the dispersion uniformity of the high amylose suspension and enhances the wetting and adhesion of the interface affinity modified starch suspension to the surface of electronic glass fibers, resulting in a more continuous distribution of the sizing film on the fiber surface and reducing the occurrence of localized sizing defects, fuzzing, and frictional damage.

[0019] This invention treats an interfacial affinity modified starch suspension with sodium hydroxide solution and acrylamide to obtain a carbamoyl ethyl modified starch suspension, which improves the hydrophilicity, slurry stability, and film-forming properties of high amylose starch. Subsequently, a methoxy polyethylene glycol succinate monoester-aminopropylsilaneamide low-ash flexible film-forming modifying compound and vinyl acetate are added to form a composite esterified modified starch suspension. This improves the flexibility, transparency, and folding resistance of the slurry film. The composite modified starch used in the secondary sizing of electronic glass fibers provides better bundle protection and abrasion resistance during weaving, reducing filament breakage, pilling, and fabric defects.

[0020] This invention employs an oxidizing agent, such as sodium hypochlorite or hydrogen peroxide, to treat a composite esterified modified starch suspension. This oxidizing agent adjusts the slurry viscosity and desizing performance, resulting in a composite modified starch for secondary sizing of electronic glass fibers that is low in ash, low in residue, easily ignited, and easy to process. The resulting product exhibits good compatibility with water and commonly used sizing auxiliaries, provides stable slurry preparation, and improves fiber bundle protection and fabric smoothness when applied to electronic glass fibers. It also enhances the stability of the weaving process and reduces the burden of subsequent desizing, ignition loss, and wastewater treatment. Detailed Implementation

[0021] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0022] Example 1 This embodiment provides a method for preparing composite modified starch for secondary sizing of electronic glass fibers, the steps of which include: Step S1: Add 225.0g of deionized water, 100.0g of high amylose cassava starch, and 8.5g of sodium sulfate to a reactor equipped with a stirrer, thermometer, and pH meter. Stir at 300r / min for 30min at 25℃ to uniformly disperse the high amylose cassava starch, obtaining a high amylose suspension. Add 0.7g of low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modifier to the high amylose suspension. Continue stirring at 25℃ for 20min to uniformly disperse it in the high amylose suspension, obtaining an interface affinity modified starch suspension. Add 75.0g of 3.0% sodium hydroxide solution to the interface affinity modified starch suspension. After stirring for 10min, add 10.0g of acrylamide. Raise the temperature to 42.5℃ and stir at 300r / min for 18h at 42.5℃ to obtain a carbamoyl ethyl modified starch suspension.

[0023] Step S2: Adjust the pH of the carbamoyl ethyl modified starch suspension to 9.5, add 0.85g of methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide low-ash flexible film-forming modifying compound, stir at 25℃ for 20min to uniformly disperse it in the carbamoyl ethyl modified starch suspension, add 6.5g of vinyl acetate, raise the temperature to 42.5℃, and stir at 300r / min for 4h at 42.5℃ to obtain a composite esterified modified starch suspension; adjust the pH of the composite esterified modified starch suspension to 8.5, add 2.0g of peroxide Hydrogen oxides were added and stirred at 300 rpm for 3 hours at 42.5℃. The pH was adjusted to 6.5, and the mixture was centrifuged at 4000 rpm for 10 minutes. The supernatant was discarded, and the precipitate was washed three times with deionized water. Each time, 300.0 g of deionized water was added to redisperse the precipitate, and the mixture was centrifuged again until the pH of the washing solution was 7.0. The washed precipitate was then dried in a vacuum drying oven at 55℃ until the mass change between two consecutive weighings did not exceed 0.1%. The precipitate was cooled to 25℃ and pulverized into a uniform powder to obtain the composite modified starch for secondary sizing of electronic glass fibers.

[0024] Preparation of low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound: Step A1: Add 100.0 g of polyglycerol-3 and 210.0 g of deionized water to a reactor equipped with a stirrer, condenser, thermometer, pH meter, and nitrogen inlet device. Stir at 300 rpm for 20 min at 25°C to ensure complete dispersion of polyglycerol-3. Purge the reactor with nitrogen gas of not less than 99.9% purity at a flow rate of 50 mL / min for 20 min, maintaining nitrogen protection. Add 27.5 g of a 60.0% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride and stir at 30°C for 10 min. Then, add 11.5 g of a 20.0% aqueous solution dropwise. A % sodium hydroxide aqueous solution was added dropwise over 20 minutes, and the pH of the system was adjusted to 11.0. The temperature was raised to 50°C, and the reaction was stirred at 300 rpm for 4 hours at 50°C. After the reaction was completed, 18.0 g of sodium 3-chloro-2-hydroxypropylsulfonate was added, and the mixture was stirred for another 10 minutes. The pH of the system was adjusted to 10.5, and the temperature was raised to 55°C. The mixture was stirred at 300 rpm for 5 hours at 55°C. After the reaction was completed, 5.0 g of boric acid and 7.5 g of glycerol were added, and the mixture was stirred for another 15 minutes. The pH of the system was adjusted to 8.5, and the mixture was stirred at 300 rpm for 3 hours at 37.5°C to obtain the diionic polyglycerol borate reaction solution.

[0025] Step A2: Adjust the pH of the diionic polyglycerol borate reaction solution to 8.2, concentrate it under reduced pressure at 50℃ and a vacuum of -0.08MPa until no obvious flowing water is precipitated in the system, and obtain a concentrated solution; place the concentrated solution in a vacuum drying oven at 60℃ and dry it until the mass change between two consecutive weighings does not exceed 0.1%, cool it to 25℃, and pulverize it into a uniform powder to obtain a low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound.

[0026] Preparation of a low-ash, flexible film-forming modified compound of methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide: Step B1: In a reactor equipped with a stirrer, condenser, thermometer, pH meter, and nitrogen inlet, add 100.0g of methoxy polyethylene glycol-750, 14.0g of succinic anhydride, 0.4g of 4-dimethylaminopyridine, and 100.0g of anhydrous acetone. Stir at 300r / min for 15min at 25℃ to ensure uniform mixing. Purge with nitrogen gas of not less than 99.9% purity at a flow rate of 50mL / min for 20min, maintaining nitrogen protection. Raise the temperature to 54℃ and react at 300r / min for 5h to obtain a methoxy polyethylene glycol succinic acid monoester reaction solution. Then, heat the methoxy polyethylene glycol succinic acid monoester reaction solution at 45℃ under a vacuum of -0.08MPa. Distilled under reduced pressure until anhydrous acetone was mostly distilled off and the system had no obvious solvent odor. Cooled to 25°C, a mixed solvent of ethanol and water consisting of 133.0 g of ethanol and 57.0 g of water was added. The mixture was stirred at 25°C for 15 min. 11.0 g of N-hydroxysuccinimide and 16.0 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added, and the pH was adjusted to 5.0. The mixture was stirred at 300 r / min at 25°C for 1.5 h to activate the reaction solution, resulting in activated carboxyl polyether. 12.0 g of 3-aminopropyltriethoxysilane was added dropwise to the activated carboxyl polyether reaction solution over 20 min. The pH was adjusted to 6.5, and the mixture was stirred at 300 r / min at 30°C for 6.5 h to obtain a polyether silane amide reaction solution. Step B2: The polyether silane amide reaction solution is concentrated under reduced pressure at 45°C and a vacuum of -0.08 MPa until no obvious low-boiling substances are distilled off, resulting in a concentrated solution. The concentrated solution is then dried in a vacuum drying oven at 55°C until the mass change between two consecutive weighings does not exceed 0.1%. After cooling to 25°C, it is pulverized into a uniform powder to obtain a methoxy polyethylene glycol succinic acid monoester-aminopropyl silane amide low-ash flexible film-forming modified compound.

[0027] Example 2 The specific implementation method is the same as in Example 1, except that this example provides a method for preparing composite modified starch for secondary sizing of electronic glass fibers, the steps of which include: Step S1: Add 150.0g of deionized water, 100.0g of high amylose cassava starch, and 5.0g of sodium sulfate to a reactor and mix to uniformly disperse the high amylose cassava starch, obtaining a high amylose suspension; add 0.2g of low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modifier compound to the high amylose suspension, and continue mixing to uniformly disperse it in the high amylose suspension, obtaining an interface affinity modified starch suspension; add 50.0g of 3.0% sodium hydroxide solution and 5.0g of acrylamide to the interface affinity modified starch suspension, and react at 30℃ for 12h to obtain a carbamoyl ethyl modified starch suspension.

[0028] Step S2: Adjust the pH of the carbamoyl ethyl modified starch suspension to 9.0, add 0.2g of methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide low-ash flexible film-forming modifying compound, continue mixing to uniformly disperse it in the carbamoyl ethyl modified starch suspension, add 3.0g of vinyl acetate, and react at 35℃ for 2h to obtain a composite esterified modified starch suspension; adjust the pH of the composite esterified modified starch suspension to 8.0, add 0.5g of sodium hypochlorite, continue reacting for 1h, adjust the pH to 6.0, centrifuge, wash, dry at 50℃ until the mass is constant, pulverize, and obtain a composite modified starch for secondary sizing of electronic glass fibers.

[0029] Preparation of low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound: Step A1: Add 100.0g of polyglycerol-3 and 180.0g of deionized water to the reactor, turn on the stirrer to completely disperse the polyglycerol-3, add 20.0g of 60.0% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride under nitrogen protection, add 8.0g of 20.0% aqueous solution of sodium hydroxide dropwise, adjust the pH to 10.5, and react at 45℃ for 3h; after the reaction is completed, add 12.0g of sodium 3-chloro-2-hydroxypropylsulfonate, adjust the pH to 10.0, and react at 50℃ for 4h; continue to add 3.0g of boric acid and 5.0g of glycerol, adjust the pH to 8.2, and react at 35℃ for 2h to obtain the diionized polyglycerol borate reaction solution.

[0030] Step A2: Adjust the pH of the diionic polyglycerol borate reaction solution to 8.0, concentrate it under reduced pressure at 45°C to form a homogeneous concentrate, dry the concentrate at 50°C until the mass is constant, pulverize it, and obtain the low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound.

[0031] Preparation of a low-ash, flexible film-forming modified compound of methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide: Step B1: 100.0g of methoxy polyethylene glycol-750, 10.0g of succinic anhydride, 0.2g of 4-dimethylaminopyridine, and 80.0g of anhydrous acetone were added to a reactor and mixed. The mixture was reacted at 50°C for 4 hours under nitrogen protection to obtain a methoxy polyethylene glycol succinic acid monoester reaction solution. The anhydrous acetone was removed from the methoxy polyethylene glycol succinic acid monoester reaction solution by vacuum distillation, and a mixture of 112.0g of ethanol and 48.0g of water was added. A mixed solvent of ethanol and water was used to add 8.0 g of N-hydroxysuccinimide and 12.0 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and the pH was adjusted to 4.5. The mixture was then activated at 20 °C for 1 h to obtain an activated carboxyl polyether reaction solution. 8.0 g of 3-aminopropyltriethoxysilane was added dropwise to the activated carboxyl polyether reaction solution, and the pH was adjusted to 6.0. The mixture was then reacted at 25 °C for 5 h to obtain a polyether silane amide reaction solution.

[0032] Step B2: Concentrate the polyether silane amide reaction solution under reduced pressure at 40°C to form a homogeneous concentrate. Dry the concentrate at 45°C until the mass is constant, then pulverize it to obtain a methoxy polyethylene glycol succinate monoester-aminopropyl silane amide low-ash flexible film-forming modified compound.

[0033] Example 3 The specific implementation method is the same as in Example 1, except that this example provides a method for preparing composite modified starch for secondary sizing of electronic glass fibers, the steps of which include: Step S1: Add 300.0g of deionized water, 100.0g of high amylose corn starch, and 12.0g of sodium sulfate to a reactor and mix to uniformly disperse the high amylose corn starch, obtaining a high amylose starch suspension; add 1.2g of low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modifier compound to the high amylose starch suspension, and continue mixing to uniformly disperse it in the high amylose starch suspension, obtaining an interface affinity modified starch suspension; add 100.0g of 3.0% sodium hydroxide solution and 15.0g of acrylamide to the interface affinity modified starch suspension, and react at 55℃ for 24h to obtain a carbamoyl ethyl modified starch suspension.

[0034] Step S2: Adjust the pH of the carbamoyl ethyl modified starch suspension to 10.0, add 1.5g of methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide low-ash flexible film-forming modifying compound, continue mixing to uniformly disperse it in the carbamoyl ethyl modified starch suspension, add 10.0g of vinyl acetate, and react at 50℃ for 6h to obtain a composite esterified modified starch suspension; adjust the pH of the composite esterified modified starch suspension to 9.0, add 3.5g of hydrogen peroxide, continue reacting for 6h, adjust the pH to 7.0, centrifuge, wash, dry at 60℃ until the mass is constant, pulverize, and obtain a composite modified starch for secondary sizing of electronic glass fibers.

[0035] Preparation of low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound: Step A1: Add 100.0g of polyglycerol-3 and 240.0g of deionized water to the reactor, turn on the stirrer to completely disperse the polyglycerol-3, add 35.0g of 60.0% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride under nitrogen protection, add 15.0g of 20.0% aqueous solution of sodium hydroxide dropwise, adjust the pH to 11.5, and react at 55℃ for 5h; after the reaction is completed, add 24.0g of sodium 3-chloro-2-hydroxypropylsulfonate, adjust the pH to 11.0, and react at 60℃ for 6h; continue to add 7.0g of boric acid and 10.0g of glycerol, adjust the pH to 8.8, and react at 40℃ for 4h to obtain the diionized polyglycerol borate reaction solution.

[0036] Step A2: Adjust the pH of the diionic polyglycerol borate reaction solution to 8.5, concentrate it under reduced pressure at 55°C to form a homogeneous concentrate, dry the concentrate at 70°C until the mass is constant, pulverize it, and obtain the low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound.

[0037] Preparation of a low-ash, flexible film-forming modified compound of methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide: Step B1: 100.0g of methoxy polyethylene glycol-750, 18.0g of succinic anhydride, 0.6g of 4-dimethylaminopyridine, and 120.0g of anhydrous acetone were added to a reactor and mixed. The mixture was reacted at 58°C for 6 hours under nitrogen protection to obtain a methoxy polyethylene glycol succinic acid monoester reaction solution. The anhydrous acetone was removed from the methoxy polyethylene glycol succinic acid monoester reaction solution by vacuum distillation, and a mixture of 154.0g of ethanol and 66.0g of water was added. A mixed solvent of ethanol and water was used to add 14.0 g of N-hydroxysuccinimide and 20.0 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and the pH was adjusted to 5.5. The mixture was then activated at 30 °C for 2 h to obtain an activated carboxyl polyether reaction solution. 16.0 g of 3-aminopropyltriethoxysilane was added dropwise to the activated carboxyl polyether reaction solution, and the pH was adjusted to 7.0. The mixture was then reacted at 35 °C for 8 h to obtain a polyether silane amide reaction solution.

[0038] Step B2: Concentrate the polyether silane amide reaction solution under reduced pressure at 50°C to form a homogeneous concentrate. Dry the concentrate at 65°C until the mass is constant, then pulverize it to obtain a methoxy polyethylene glycol succinate monoester-aminopropyl silane amide low-ash flexible film-forming modified compound.

[0039] Comparative Example 1 The specific implementation method is the same as in Example 1, except that 0.7g of low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modification compound is not added in step S1, and the rest is the same as in Example 1.

[0040] Comparative Example 2 The specific implementation method is the same as in Example 1, except that 0.85g of methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide low-ash flexible film-forming modifying compound is not added in step S2, and the rest is the same as in Example 1.

[0041] Comparative Example 3 The specific implementation method is the same as in Example 1, except that 2.0g of hydrogen peroxide is not added in step S2, and the rest is the same as in Example 1.

[0042] Performance testing The composite modified starches prepared in Examples 1-3 and Comparative Examples 1-3 for secondary sizing of electronic glass fibers were subjected to performance testing according to the following method, which includes the following steps: The composite modified starch samples obtained from Examples 1-3 and Comparative Examples 1-3 for secondary sizing of electronic glass fibers were taken and equilibrated for 24 hours at 25°C and 50% relative humidity.

[0043] For the initial viscosity and viscosity change rate tests, 50.0g of sample was weighed and added to 950.0g of deionized water. The sample was dispersed at 25℃ for 20min, heated to 95℃ and held for 30min to allow the sample to fully gelatinize. Then, it was cooled to 50℃, and deionized water was added to bring the total mass of the system to 1000.0g, resulting in a starch paste with a mass fraction of 5.0%. After cooling the starch paste to 25℃, the initial viscosity was tested using a rotational viscometer. The test rotor and rotation speed were kept consistent in all samples, and the value after 30s of stabilization was taken as the initial viscosity.

[0044] Take another batch of starch paste and place it in a sealed container. Let it stand at 25°C for 24 hours. Then, measure the viscosity after standing under the same test conditions. The viscosity change rate is calculated as "absolute value of the difference between the viscosity after standing for 24 hours and the initial viscosity / initial viscosity × 100%".

[0045] During the 550nm transmittance test, a starch paste with a mass fraction of 5.0% was uniformly coated onto the surface of a clean glass plate. The wet film thickness was controlled to be 200μm. The film was dried at 50℃ to constant weight to obtain a uniform film. After the film was completely peeled off from the glass plate, a flat area was cut out, and the transmittance was measured at 550nm using a visible spectrophotometer.

[0046] During the elongation at break test of the slurry film, the slurry film was cut into samples with a width of 10 mm and an effective clamping length of 50 mm. After equilibration for 24 hours at 25℃ and 50% relative humidity, a tensile test was performed at a tensile speed of 50 mm / min. The elongation at break was recorded, and the elongation at break was calculated as "elongation at break / effective clamping length × 100%".

[0047] In the abrasion resistance cycle test of electronic glass fiber, a starch paste with a mass fraction of 5.0% was used as a secondary sizing solution to impregnate and sizing the same batch of electronic glass fiber, with the sizing rate controlled at 1.0%. After drying at 105℃ for 10 minutes, a reciprocating friction test was conducted under the same tension, the same friction contact angle, and the same friction load. The number of reciprocating friction cycles before the electronic glass fiber bundle showed obvious filament breakage or rapid increase in fuzz was taken as the abrasion resistance cycle of the electronic glass fiber.

[0048] During the hair count test, electronic glass fibers that have undergone secondary sizing and drying are used. Under the same traction speed and the same test length conditions, the number of hairs with a length greater than 1 mm is counted and converted into the number of hairs per 1000 m of electronic glass fiber.

[0049] During the desizing residue test, the mass of electronic glass fiber after secondary sizing and drying was weighed and recorded as the mass before desizing. It was then placed in deionized water at 90℃ for 30 minutes, rinsed with deionized water, and dried at 105℃ to constant weight, which was recorded as the mass after desizing. The desizing residue rate was calculated as "mass after desizing / mass before desizing × 100%".

[0050] For ash content testing, weigh the sample after drying to constant weight at 105℃, place it in a high-temperature resistant crucible, ignite it in a muffle furnace to constant weight, and weigh the residual ash after cooling. Calculate the ash content as "residual ash mass / dried sample mass × 100%". All tests were conducted using the same batch of samples, the same sample preparation conditions, and the same testing conditions. The test results were taken as the average of three parallel samples.

[0051] Test results: Table 1: Test results of each embodiment and comparative example ; Examples 1-3 showed significant improvements over Comparative Examples 1-3 in terms of viscosity stability, film transparency, film flexibility, wear resistance protection of electronic glass fibers, fuzz control, and desizing residue control. This indicates that the present invention can effectively solve the problems of unstable viscosity of existing starch sizing agents, brittle film, insufficient affinity with the surface of electronic glass fibers, excessive fuzz and broken fibers during weaving, and high residue after desizing.

[0052] Specifically, the initial viscosities of Examples 1-3 ranged from 24.8 to 92.6 mPa·s, all within a low range suitable for sizing. Among them, Example 1 had a viscosity of 61.8 mPa·s, with a viscosity change rate of only 3.5%, significantly lower than the 10.4% of Comparative Example 1, 7.9% of Comparative Example 2, and 15.8% of Comparative Example 3. This indicates that the synergistic effect of the low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound, the methoxy polyethylene glycol succinate monoester-aminopropylsilane amide low-ash flexible film-forming modified compound, and the oxidant can significantly improve the storage stability of the paste and prevent excessive viscosity increase.

[0053] The transmittance at 550 nm in Examples 1-3 was 89.7-92.6%, which was higher than that of Comparative Example 1 (87.2%), Comparative Example 2 (84.6%), and Comparative Example 3 (86.5%). Furthermore, the elongation at break of the film was 13.5-18.7%, which was higher than that of Comparative Example 2 (6.8%). This indicates that the methoxy polyethylene glycol succinate monoester-aminopropyl silane amide low-ash flexible film-forming modifier compound can improve the flexibility and transparency of the film and prevent the film from becoming brittle.

[0054] The electronic glass fibers of Examples 1-3 had abrasion resistance cycles of 526-685, significantly higher than those of Comparative Example 1 (392), Comparative Example 2 (348), and Comparative Example 3 (436); the number of hairs was only 7-14 per 1000m, significantly lower than those of Comparative Example 1 (36 per 1000m), Comparative Example 2 (29 per 1000m), and Comparative Example 3 (23 per 1000m). This indicates that the low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modifier compound can enhance the wetting and adhesion of the slurry to the surface of the electronic glass fibers, and the methoxy polyethylene glycol succinate monoester-aminopropylsilane amide low-ash flexible film-forming modifier compound can improve the abrasion resistance and protection of the slurry film.

[0055] The desizing residue rate of Examples 1-3 was 0.16-0.29%, which was significantly lower than that of Comparative Example 3 (0.91%), indicating that oxidant treatment can effectively reduce residue and improve desizing performance. The ash content of Examples 1-3 was 0.055-0.068%, which was close to that of the Comparative Example and remained at a low level, indicating that the present invention does not significantly increase inorganic ash residue while improving sizing protection performance.

[0056] In summary, this invention utilizes the synergistic effect of a low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modifier, a methoxy polyethylene glycol succinate monoester-aminopropylsilaneamide low-ash flexible film-forming modifier, and an oxidant to produce a composite modified starch for secondary sizing of electronic glass fibers. This modified starch exhibits a combination of properties including low viscosity, low viscosity change rate, high transparency and flexible film, high abrasion resistance, low fuzz, low desizing residue, and low ash content.

[0057] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing composite modified starch for secondary sizing of electronic glass fibers, characterized in that the steps include... include: S1. By weight, 150.0-300.0 parts of deionized water, 100.0 parts of high amylose, and 5.0-12.0 parts of sodium sulfate are mixed to obtain a high amylose suspension; 0.2-1.2 parts of a low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modifying compound are added to the high amylose suspension, and mixing is continued to obtain an interface affinity modified starch suspension; 50.0-100.0 parts of sodium hydroxide solution and 5.0-15.0 parts of acrylamide are added to the interface affinity modified starch suspension, and the mixture is reacted at 30-55℃ to obtain a carbamoyl ethyl modified starch suspension; S2. Adjust the pH of the carbamoyl ethyl modified starch suspension to 9.0-10.0, add 0.2-1.5 parts of methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide low ash flexible film-forming modifying compound, continue mixing, add 3.0-10.0 parts of vinyl acetate, and react at 35-50℃ to obtain a composite esterified modified starch suspension; Adjust the pH of the composite esterified modified starch suspension to 8.0-9.0, add 0.5-3.5 parts of oxidant, continue the reaction, adjust the pH to 6.0-7.0, centrifuge, wash, dry, and pulverize.

2. The method for preparing composite modified starch for secondary sizing of electronic glass fibers according to claim 1, characterized in that, In step S1, the high amylose is high amylose tapioca starch or high amylose corn starch; the reaction time at 30-55℃ is 12-24h.

3. The method for preparing composite modified starch for secondary sizing of electronic glass fibers according to claim 1, characterized in that, In step S2, the reaction time at 35-50℃ is 2-6 hours; the oxidant is sodium hypochlorite or hydrogen peroxide.

4. The method for preparing composite modified starch for secondary sizing of electronic glass fibers according to claim 1, characterized in that, The preparation method of the low-ash N-hydroxypropyltrimethylammonium-hydroxypropylsulfonic acid diionic polyglycerol borate glass affinity modified compound includes: A1. By weight, mix 100.0 parts of polyglycerol-3 and 180.0-240.0 parts of deionized water. Under nitrogen protection, add 20.0-35.0 parts of an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride, and add sodium hydroxide aqueous solution dropwise to adjust the pH to 10.5-11.

5. React at 45-55℃. Add 12.0-24.0 parts of sodium 3-chloro-2-hydroxypropylsulfonate, adjust the pH to 10.0-11.0, and react at 50-60℃. Add 3.0-7.0 parts of boric acid and 5.0-10.0 parts of glycerol, adjust the pH to 8.2-8.8, and react at 35-40℃ to obtain a diionized polyglycerol borate reaction solution. A2. Adjust the pH of the diionic polyglycerol borate reaction solution to 8.0-8.5, concentrate under reduced pressure at 45-55℃, dry and pulverize.

5. The method for preparing composite modified starch for secondary sizing of electronic glass fibers according to claim 4, characterized in that, In step A1, the reaction time is 3-5 hours at 45-55℃; 4-6 hours at 50-60℃; and 2-4 hours at 35-40℃.

6. The method for preparing composite modified starch for secondary sizing of electronic glass fibers according to claim 4, characterized in that, In step A2, the drying temperature is 50-70℃.

7. The method for preparing composite modified starch for secondary sizing of electronic glass fibers according to claim 1, characterized in that, The preparation method of the methoxy polyethylene glycol succinate monoester-aminopropyl silaneamide low-ash flexible film-forming modified compound includes: B1. By weight, mix 100.0 parts of methoxy polyethylene glycol-750, 10.0-18.0 parts of succinic anhydride, 0.2-0.6 parts of 4-dimethylaminopyridine, and 80.0-120.0 parts of anhydrous acetone, and react under nitrogen protection at 50-58°C to obtain a methoxy polyethylene glycol succinate monoester reaction solution; distill the methoxy polyethylene glycol succinate monoester reaction solution under reduced pressure, add 160.0-220.0 parts of a mixed solvent of ethanol and water, and add... Add 8.0-14.0 parts of N-hydroxysuccinimide and 12.0-20.0 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, adjust the pH to 4.5-5.5, and activate at 20-30℃ to obtain an activated carboxyl polyether reaction solution; add 8.0-16.0 parts of 3-aminopropyltriethoxysilane dropwise to the activated carboxyl polyether reaction solution, adjust the pH to 6.0-7.0, and react at 25-35℃ to obtain a polyether silane amide reaction solution; B2. Concentrate the polyether silaneamide reaction solution under reduced pressure at 40-50℃, then dry and pulverize.

8. The method for preparing composite modified starch for secondary sizing of electronic glass fibers according to claim 7, characterized in that, In step B1, the reaction time is 4-6 hours at 50-58°C; the activation time is 1-2 hours at 20-30°C; and the reaction time is 5-8 hours at 25-35°C.

9. The method for preparing composite modified starch for secondary sizing of electronic glass fibers according to claim 7, characterized in that, In step B2, the drying temperature is 45-65℃.

10. A composite modified starch for secondary sizing of electronic glass fibers, characterized in that, The composite modified starch for secondary sizing of electronic glass fibers is prepared according to any one of claims 1-9 by the method for preparing the composite modified starch for secondary sizing of electronic glass fibers.