A silica dispersion, its preparation method and application

Abstract

This invention discloses a silica dispersion, its preparation method, and its applications. By mass, each 100 parts of silica dispersion contains the following components: 5-20 parts modified silica and 80-95 parts ethylene glycol. The modified silica is prepared by modifying silica with a hydrophilic modifier and a lipophilic modifier. The hydrophilic modifier is a copolymer obtained by polymerizing an acrylamide derivative, sodium styrene sulfonate, and maleic anhydride. The lipophilic modifier is a lipophilic silane coupling agent. This invention uses a hydrophilic modifier and a lipophilic modifier to modify silica sequentially, resulting in partial grafting of hydrophilic groups and partial grafting of lipophilic groups onto the silica surface. The hydrophilic groups enable stable dispersion of silica in ethylene glycol, preventing sedimentation, agglomeration, or re-coarsening during storage or transportation. The lipophilic groups improve the compatibility of silica with the polymer during polyester polymerization, allowing for uniform dispersion in the polyester.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a silica dispersion, its preparation method, and its application in in-situ polymerization of polyester. Background Technology

[0002] In my country, synthetic fibers containing more than 85% polyethylene terephthalate (PET) are called polyester fibers, and their commercial name is polyester. Polyester is a polymer obtained by the condensation polymerization of polybasic acids and polyols. Polyester synthesis processes include direct esterification and transesterification. Direct esterification has become the main synthesis process due to its advantages such as low raw material consumption and short reaction time. The main reaction process of direct esterification is as follows: first, high-purity terephthalic acid and ethylene glycol undergo an esterification reaction to produce ester and water. Then, the generated ester undergoes a condensation polymerization reaction to obtain polyester and ethylene glycol. This condensation polymerization includes pre-condensation polymerization and final condensation polymerization. Polyester fiber is a typical hydrophobic fiber with a moisture regain of only about 0.4%. Furthermore, polyester fibers generally have a smooth surface without a porous structure, resulting in poor wearing comfort when used as clothing materials and a stuffy feeling when worn in humid and hot conditions.

[0003] High-performance, multifunctional, lightweight, and flexible new fiber materials provide an important path for enhancing the value of the textile industry and meeting the upgraded consumer demands for functionality, fashion, and green products. Adding silica to polyester fibers followed by alkali treatment creates micropores on the fiber surface, giving the fibers moisture-wicking and quick-drying properties. Three invention patents published by Suzhou Jinhui Fiber New Materials Co., Ltd. (publication numbers CN104746171A, CN104746172A, and CN104746173A) involve adding nano-silica to hemp carbon polyester fibers, coffee carbon polyester fibers, and hemp stalk carbon polyester fibers, followed by alkali washing to remove the silica, resulting in porous polyester fibers that improve the fibers' adsorption and moisture absorption capabilities.

[0004] Silica surfaces contain various hydroxyl groups, such as free hydroxyl groups, associated hydroxyl groups, and twinned hydroxyl groups. Adjacent hydroxyl groups are bonded together by hydrogen bonds. The hydrogen atoms of isolated hydroxyl groups are highly positively charged and readily adsorb onto negatively charged atoms. The presence of surface hydroxyl groups gives the surface chemisorption activity, forming hydrogen bonds with water molecules for adsorption. Furthermore, smaller particle size, larger specific surface area, higher surface energy, and stronger cohesion result in a thermodynamically unstable state, making particle aggregation more likely. After reducing particle size through physical and mechanical methods, surfactants or surface treatments are still needed to prevent coarsening and aggregation during subsequent storage, or incompatibility with the polymer matrix during use. The three invention patents (publication numbers CN104746171A, CN104746172A, and CN104746173A) published by Suzhou Jinhui Fiber New Material Co., Ltd. involve directly dispersing hemp charcoal / coffee charcoal / hemp stalk charcoal, silane coupling agent, and nano-sized silica powder. Specifically, the nano-sized silica is attached to the pores on the surface of the hemp charcoal / coffee charcoal / hemp stalk charcoal without pretreatment, resulting in uneven dispersion of silica in the fiber.

[0005] Chinese patent CN102330188A discloses a method for preparing nano-silica-modified polyester fibers. The method involves adding terephthalic acid and ethylene glycol to a slurry kettle for pulping, then adding nano-silica, nano-zirconium dioxide, and a matting agent, titanium dioxide, to the slurry kettle for esterification and polycondensation to obtain nano-modified polyester chips. This patent uses a technique that directly adds nano-silica to the polymer monomers for polymerization. However, this method of directly adding nano-silica suffers from drawbacks. Since silica cannot be well dispersed in ethylene glycol, it tends to agglomerate during polymerization and esterification, failing to disperse effectively in the polyester chips and thus failing to exhibit the effects and properties of nanomaterials.

[0006] Ye Renji, a student majoring in Materials Physics and Chemistry at Donghua University, in his 2005 graduate thesis "Industrial Research on PET Fiber Modified with Nano-Silica," described a method that involves dispersing different nanoparticles in ethylene glycol using high-speed shearing and stirring. The ethylene glycol is then esterified with terephthalic acid, followed by condensation polymerization to obtain uniformly dispersed PET / nano-silica chips, which are then melt-spun. This method uses high-speed shearing to disperse nano-silica in ethylene glycol; however, this method only disperses the silica briefly, and after the shearing force ceases, the nanoparticles exhibit aggregation, agglomeration, and coarsening.

[0007] Chinese patent CN1760443A discloses a method for preparing polyester nanocomposite materials for deep-dyeing fibers. The method uses nano-silica as an additive modifier, firstly organically modifying its surface to ensure uniform dispersion in ethylene glycol, one of the polyester monomers. The prepared nano-silica / ethylene glycol dispersion is then added to a reactor during esterification, where it polymerizes with another polyester monomer. During polymerization, a polyester nanocomposite material is obtained, which is then melt-spun at high temperature to finally form the polyester nanocomposite fiber. This method significantly improves dye uptake by adding nano-silica particles during the polymerization reaction. The nano-silica undergoes surface organic coating modification, using one or more organic modifiers and coupling agents. However, the use of organic modifiers or coupling agents does not effectively improve the dispersion of nano-silica in ethylene glycol or polyester.

[0008] Silica particles generally have a hydrophilic and highly polar surface, making them prone to binding with moisture in the air and agglomerating. This reduces their dispersibility, and the resulting agglomerates are difficult to disperse in weakly polar organic media, nor do they readily undergo physical adsorption with the organic medium. To improve the dispersibility of silica, commonly used modifiers include silane coupling agents, organohalosilanes, silazanes, siloxane organosilicon compounds, alcohols, and organic polymers. Existing technologies do not report on the sequential modification of silica with hydrophilic and lipophilic modifiers, and their application in in-situ polymerization of polyester to improve the compatibility and dispersibility of silica with polyester, thereby enhancing the moisture absorption and quick-drying properties of polyester fibers. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide a silica dispersion, its preparation method, and its applications. The present invention employs a hydrophilic modifier and a lipophilic modifier to sequentially modify silica, resulting in partial grafting of hydrophilic groups and partial grafting of lipophilic groups onto the silica surface. The hydrophilic groups enable stable dispersion of silica in ethylene glycol, preventing sedimentation, agglomeration, or coarsening during storage or transportation. The lipophilic groups enhance the compatibility of silica with the polymer during polyester polymerization, thereby enabling uniform dispersion within the polyester.

[0010] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0011] A silica dispersion, by mass, comprises the following components in every 100 parts of silica dispersion: 5-20 parts of modified silica and 80-95 parts of ethylene glycol; wherein the modified silica is prepared by modifying silica with a hydrophilic modifier and a lipophilic modifier, the hydrophilic modifier being a copolymer obtained by polymerizing an acrylamide derivative, sodium styrene sulfonate, and maleic anhydride, and the lipophilic modifier being a lipophilic silane coupling agent.

[0012] Furthermore, the acrylamide derivative has the structure shown in general formula (I):

[0013]

[0014] In general formula (Ⅰ), R1, R2, and R3 may be the same or different, and each is independently selected from H or methyl; R4 is one of alkane group or aromatic group; M is one of Na, K, and H. Preferably, the acrylamide derivative is selected from one of 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamido-2-methylpropanesulfonate, sodium 4-acrylamidobenzenesulfonate, and sodium p-methacrylamidobenzenesulfonate.

[0015] Preferably, the lipophilic silane coupling agent is selected from at least one of phenyltrimethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, and octadecyltrimethoxysilane.

[0016] Furthermore, the silica is nano-silica prepared by a gas-phase method, with a particle size of 50-100 nm.

[0017] The present invention further provides a method for preparing the silica dispersion, comprising the following steps:

[0018] (1) Hydrophilic modification

[0019] A hydrophilic modifier was obtained by polymerization of acrylamide derivatives, sodium styrene sulfonate, and maleic anhydride under inert gas protection using potassium persulfate and sodium bisulfite as initiators. An aqueous solution of silica was added to the hydrophilic modifier to carry out a hydrophilic modification reaction. After the reaction, the silica was filtered, washed, and dried to obtain hydrophilic silica.

[0020] (2) Lipophilic modification

[0021] An oleophilic modifier was added to an aqueous solution of hydrophilic silica, and the mixture was heated under inert gas protection. After the reaction, the silica was filtered, washed, and dried to obtain the modified silica.

[0022] (3) Preparation of silica dispersion

[0023] The modified silica and ethylene glycol are mixed according to the formula and dispersed evenly by mechanical stirring to obtain a silica dispersion.

[0024] In the above method, the hydrophilic modifier is prepared by polymerization of three monomers through unsaturated double bonds under the action of an oxidant; the anhydride group of the hydrophilic modifier reacts with the hydroxyl group of silica to graft the hydrophilic group onto the silica surface; the methoxy / ethoxy group of the lipophilic modifier reacts with the hydroxyl group of silica after hydrolysis to graft the lipophilic group onto the silica surface.

[0025] Furthermore, in step (1), the mass ratio of acrylamide derivative, sodium styrene sulfonate, and maleic anhydride is (1-3):(1-3):1.

[0026] Furthermore, in this method, the mass of the hydrophilic modifier is 1-3% of the mass of silica; the mass of the lipophilic modifier is 1-3% of the mass of the hydrophilic silica.

[0027] Furthermore, in step (1), the heating temperature is 50-70℃, the polymerization reaction time is 2-6h, and the hydrophilic modification reaction time is 1-4h; in step (2), the heating temperature is 70-90℃, and the reaction time is 1-4h.

[0028] This invention further provides the application of silica dispersions in in-situ polyester polymerization. Specifically, the silica dispersion is added during the polyester polymerization process, either during esterification, pre-condensation, final condensation, or before the reaction. The silica dispersion of this invention is modified silica dispersed in ethylene glycol. Ethylene glycol can be used as a raw material for polyester esterification; therefore, the silica dispersion is preferably added before the esterification reaction.

[0029] The specific preparation process of polyester fiber is as follows: raw materials such as silica dispersion, polyterephthalic acid, ethylene glycol and oxidant are esterified, pre-condensed and finally condensed to obtain polyester melt, which is then spun to obtain polyester fiber; silica is removed by alkaline washing to form micropores on the surface of polyester fiber.

[0030] The beneficial effects of this invention are:

[0031] This invention utilizes hydrophilic and lipophilic modifiers to modify silica sequentially, grafting hydrophilic groups onto the silica surface and lipophilic groups onto the silica surface. The hydrophilic groups enable silica to be stably dispersed in ethylene glycol, and the prepared silica dispersion will not experience sedimentation, agglomeration, or coarsening during storage or transportation. The lipophilic groups enhance the compatibility of silica with the polyester polymer, allowing silica to be uniformly dispersed in the polyester.

[0032] The modified silica surface has no hydroxyl groups that crosslink or self-polymerize, resulting in a lower system viscosity. Furthermore, the sulfonated styrene-maleic anhydride in the hydrophilic modifier can reduce the viscosity of the system, thereby increasing the solid content of the silica dispersion. Acrylamide derivatives can not only improve the dispersibility of silica in water, but also improve the mechanical properties of polyester fibers.

[0033] The silica dispersion of the present invention has low viscosity, high solid content, small particle size, and good storage stability. When applied to in-situ polymerization of polyester, the micropores on the surface of the polyester fiber are uniformly dispersed after alkali dissolution, and the fiber's breaking strength and elongation at break do not change significantly. In addition, the water diffusion time is short and the evaporation rate is high, which gives it good moisture absorption and quick-drying properties. Attached Figure Description

[0034] Figure 1 This is a SEM image of microporous polyester fiber No. 1 corresponding to an embodiment of the present invention. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0036] This invention provides a silica dispersion, comprising, by weight, 5-20 parts modified silica and 80-95 parts ethylene glycol per 100 parts of silica dispersion; wherein the modified silica is prepared by modifying silica with a hydrophilic modifier and a lipophilic modifier, the hydrophilic modifier being a copolymer obtained by polymerizing an acrylamide derivative, sodium styrene sulfonate, and maleic anhydride, and the lipophilic modifier being a lipophilic silane coupling agent.

[0037] Among them, acrylamide derivatives have the structure shown in general formula (Ⅰ):

[0038]

[0039] In general formula (Ⅰ), R1, R2, and R3 may be the same or different, and each is independently selected from H or methyl; R4 is one of alkane group or aromatic group; M is one of Na, K, and H.

[0040] The acrylamide derivative is preferably one of 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamido-2-methylpropanesulfonate, sodium 4-acrylamidobenzenesulfonate, and sodium p-methacrylamidobenzenesulfonate.

[0041] The lipophilic silane coupling agent is preferably at least one of phenyltrimethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, and octadecyltrimethoxysilane.

[0042] The silica in this product is nano-silica prepared by a gas-phase method, with a particle size of 50–100 nm.

[0043] The present invention further provides a method for preparing the silica dispersion, comprising the following steps:

[0044] (1) Hydrophilic modification

[0045] Acrylamide derivatives, sodium styrene sulfonate, and maleic anhydride are mixed in a mass ratio of (1-3):

[0046] (1-3): 1. Using potassium persulfate and sodium bisulfite as initiators, the mixture is heated to 50-70°C under inert gas protection and polymerized for 2-6 hours to obtain a hydrophilic modifier. Then, an aqueous silica solution is added to the hydrophilic modifier, and the reaction continues for 1-4 hours. After the reaction, the mixture is filtered, washed, and dried to obtain hydrophilic silica. The mass of the hydrophilic modifier is 1-3% of the mass of silica.

[0047] (2) Lipophilic modification

[0048] An oleophilic modifier is added to an aqueous solution of hydrophilic silica, and the mixture is heated to 70–90°C under inert gas protection for 1–4 hours. After the reaction, the silica is filtered, washed, and dried to obtain modified silica. The mass of the oleophilic modifier is 1–3% of the mass of the hydrophilic silica.

[0049] (3) Preparation of silica dispersion

[0050] The modified silica and ethylene glycol are mixed according to the formula and dispersed evenly by mechanical stirring to obtain a silica dispersion.

[0051] In the above method, the hydrophilic modifier is prepared by polymerization of three monomers through unsaturated double bonds under the action of an oxidant; the anhydride group of the hydrophilic modifier reacts with the hydroxyl group of silica to graft the hydrophilic group onto the silica surface; the methoxy / ethoxy group of the lipophilic modifier reacts with the hydroxyl group of silica after hydrolysis to graft the lipophilic group onto the silica surface.

[0052] This invention further provides the application of silica dispersions in in-situ polyester polymerization. Specifically, the silica dispersion is added during the polyester polymerization process, either during esterification, pre-condensation, final condensation, or before the reaction. The silica dispersion of this invention is modified silica dispersed in ethylene glycol. Ethylene glycol can be used as a raw material for polyester esterification; therefore, the silica dispersion is preferably added before the esterification reaction.

[0053] Polyester fiber preparation process: Raw materials such as silica dispersion, polyterephthalic acid, ethylene glycol and oxidant are esterified, pre-condensed and final condensed to obtain polyester melt, which is then spun to obtain polyester fiber; silica is removed by alkaline washing to form micropores on the surface of polyester fiber.

[0054] The present invention will be further described in detail below through specific embodiments.

[0055] Preparation of modified silica

[0056] Example 1

[0057] 0.40 g of 2-acrylamide-2-methylpropanesulfonic acid was weighed and dispersed in 5 ml of ice water. The pH was adjusted to 8.0 with NaOH solution to obtain solution A. 0.40 g of sodium styrene sulfonate and 0.20 g of maleic anhydride were weighed and dispersed in 10 ml of water. Solution A was added, followed by 0.01 g of potassium persulfate and 0.01 g of sodium bisulfite. The mixture was heated to 56 °C under a nitrogen atmosphere and polymerized for 4 h to obtain a hydrophilic modifier. Then, an aqueous solution of silica containing 50 g of silica was added, and the reaction was continued for 2 h. The mixture was filtered, washed, and dried to obtain hydrophilic silica.

[0058] 1g of phenyltrimethoxysilane was added to an aqueous solution of hydrophilic silica containing 50g of hydrophilic silica. The mixture was heated to 80°C under a nitrogen atmosphere and reacted for 2 hours. The mixture was then filtered, washed, and dried to obtain modified silica Al.

[0059] Example 2

[0060] 0.20 g of 2-acrylamide-2-methylpropanesulfonic acid was weighed and dispersed in 5 ml of ice water. The pH was adjusted to 8.0 with NaOH solution to obtain solution A. 0.60 g of sodium styrene sulfonate and 0.20 g of maleic anhydride were weighed and dispersed in 10 ml of water. Solution A was added, followed by 0.01 g of potassium persulfate and 0.01 g of sodium bisulfite. The mixture was heated to 56 °C under a nitrogen atmosphere and polymerized for 4 h to obtain a hydrophilic modifier. Then, an aqueous solution of silica containing 50 g of silica was added, and the reaction was continued for 2 h. The mixture was filtered, washed, and dried to obtain hydrophilic silica.

[0061] 1g of phenyltriethoxysilane was added to an aqueous solution of hydrophilic silica containing 50g of hydrophilic silica. The mixture was heated to 80°C under a nitrogen atmosphere and reacted for 2 hours. The mixture was then filtered, washed, and dried to obtain modified silica A2.

[0062] Comparative Example 1

[0063] Weigh 0.80 g of 2-acrylamide-2-methylpropanesulfonic acid and disperse it in 10 ml of ice water. Adjust the pH to 8.0 with NaOH solution to obtain solution A. Weigh 0.80 g of sodium styrene sulfonate and 0.40 g of maleic anhydride and disperse them in 20 ml of water. Add solution A, then add 0.02 g of potassium persulfate and 0.02 g of sodium bisulfite. Heat to 56 °C in a nitrogen atmosphere and polymerize for 4 h to obtain a hydrophilic modifier. Then add an aqueous solution of silica containing 50 g of silica and continue the reaction for 2 h. Filter, wash, and dry to obtain hydrophilic silica.

[0064] 2g of phenyltrimethoxysilane was added to an aqueous solution of hydrophilic silica containing 50g of hydrophilic silica. The mixture was heated to 80°C under a nitrogen atmosphere and reacted for 2 hours. The mixture was then filtered, washed, and dried to obtain modified silica B.

[0065] Comparative Example 2

[0066] Weigh 0.40 g of 2-acrylamide-2-methylpropanesulfonic acid and disperse it in 5 ml of ice water. Adjust the pH to 8.0 with NaOH solution to obtain solution A. Weigh 0.40 g of sodium styrene sulfonate and 0.20 g of maleic anhydride and disperse them in 10 ml of water. Add solution A, then add 0.01 g of potassium persulfate and 0.01 g of sodium bisulfite. Heat to 56 °C in a nitrogen atmosphere and polymerize for 4 h to obtain a hydrophilic modifier. Then add an aqueous solution of silica containing 50 g of silica and continue the reaction for 2 h. Filter, wash, and dry to obtain modified silica C1.

[0067] Comparative Example 3

[0068] 0.80 g of 2-acrylamide-2-methylpropanesulfonic acid was weighed and dispersed in 10 ml of ice water. The pH was adjusted to 8.0 with NaOH solution to obtain solution A. 0.80 g of sodium styrene sulfonate and 0.40 g of maleic anhydride were weighed and dispersed in 20 ml of water. Solution A was added, along with 0.02 g of potassium persulfate and 0.02 g of sodium bisulfite. The mixture was heated to 56 °C under a nitrogen atmosphere and polymerized for 4 h to obtain a hydrophilic modifier. Then, 50 g of silica aqueous solution was added, and the reaction was continued for 2 h. The mixture was filtered, washed, and dried to obtain modified silica C2.

[0069] Comparative Example 4

[0070] 1g of phenyltrimethoxysilane was added to 50g of silica aqueous solution, heated to 80℃ in a nitrogen atmosphere, reacted for 2h, filtered, washed, and dried to obtain modified silica D1.

[0071] Comparative Example 5

[0072] 2g of phenyltrimethoxysilane was added to 50g of silica aqueous solution, heated to 80℃ in a nitrogen atmosphere, reacted for 2h, filtered, washed, and dried to obtain modified silica D2.

[0073] Comparative Example 6

[0074] Weigh 0.40g of sodium styrene sulfonate and 0.20g of maleic anhydride and disperse them in 10ml of water. Add 0.01g of potassium persulfate and 0.01g of sodium bisulfite. Heat to 56℃ in a nitrogen atmosphere and polymerize for 4h to obtain a hydrophilic modifier. Then add 50g of silica aqueous solution and continue the reaction for 2h. Filter, wash and dry to obtain hydrophilic silica.

[0075] 1g of phenyltrimethoxysilane was added to an aqueous solution of hydrophilic silica containing 50g of hydrophilic silica. The mixture was heated to 80°C under a nitrogen atmosphere and reacted for 2 hours. The mixture was then filtered, washed, and dried to obtain modified silica D3.

[0076] Preparation and testing of silica dispersions

[0077] The modified silica prepared in Examples 1-2 and Comparative Examples 1-6, as well as untreated silica (E) purchased directly, were mixed with ethylene glycol at the mass ratios in Table 1 and mechanically stirred to disperse them evenly, resulting in silica dispersions numbered 1 to 11.

[0078] Table 1. Mass ratio of silica dispersion components

[0079]

[0080] Viscosity and particle size were tested on silica dispersions No. 1-10, and viscosity and particle size were also tested after 30 days of storage. The test data are shown in Table 2. Since the slurry obtained from silica dispersion No. 11 was paste-like and had poor fluidity, no relevant tests were performed.

[0081] Table 2. Performance test results of silica dispersion

[0082]

[0083] As shown in Table 2 above, silica dispersions 1-5 have lower viscosity and smaller particle size in ethylene glycol due to the hydrophilic groups grafted onto the silica surface; after 30 days of storage, the viscosity and particle size do not change significantly. Silica dispersions 6-7 have higher viscosity and larger particle size in ethylene glycol due to the lipophilic groups grafted onto the silica surface; after 30 days of storage, the viscosity and particle size change significantly. Silica dispersion 8, due to the absence of acrylamide derivatives in the hydrophilic modifier, has higher viscosity and larger particle size in ethylene glycol compared to silica dispersion 1; after 30 days of storage, the viscosity and particle size change significantly. Silica dispersion 9 uses commercially available silica; due to its self-crosslinking, it has higher viscosity and larger particle size; after 30 days of storage, the viscosity and particle size change significantly. Compared to silica dispersion No. 1, silica dispersion No. 10 has an increased silica content, resulting in a slight increase in viscosity but little change in particle size; after 30 days of storage, the viscosity and particle size remain largely unchanged. Silica dispersion No. 11 uses commercially available silica; the resulting slurry is paste-like with poor flowability, and no relevant tests were conducted.

[0084] Preparation and performance testing of microporous polyester fibers

[0085] Silica dispersions numbered 1 to 10 were added to a polyester reaction vessel (where the mass of silica in the silica dispersions accounted for 1% of the total mass of terephthalic acid and ethylene glycol, the molar ratio of terephthalic acid to ethylene glycol was 1:1.2, and the mass of tetrabutyl titanate catalyst accounted for 0.2% of the mass of terephthalic acid). After esterification (reaction temperature 265℃, reaction pressure 150kPa), pre-polymerization (reaction temperature 260℃, reaction pressure 3kPa), and final polymerization (reaction temperature 265℃, reaction pressure 100Pa), a polyester melt was obtained. Spinning was performed at 255℃ and a winding speed of 4500m / min to obtain polyester fibers. The polyester fibers were alkali-washed in a 1mol / L sodium hydroxide solution at 100℃ for 120min, then washed with water and dried to obtain microporous polyester fibers numbered 1 to 10. The microporous polyester fibers numbered 1 to 10, and the conventional polyester fiber numbered 11 (without silica dispersion added during polymerization) were tested according to the following method:

[0086] Breaking strength and elongation at break: Refer to GB / T 14344-2022 Test method for tensile properties of chemical fiber filaments;

[0087] Water droplet diffusion time and evaporation rate: Refer to GB / T 21655.1-2008 Evaluation of moisture absorption and quick-drying properties of textiles - Part 1: Single combination test method.

[0088] The test results are shown in Table 3.

[0089] Table 3. Performance test results of polyester fibers

[0090] Polyester fiber serial number 1 2 3 4 5 6 7 8 9 10 11 Fracture strength (cN / dtex) 3.9 4.0 2.4 2.5 2.4 2.3 2.1 2.2 2.6 3.8 4.2 Elongation at break (%) 35 36 23 25 24 23 21 21 27 34 39 Water droplet diffusion time (s) 0.3 0.3 4.5 4.6 4.8 5.1 5.2 4.7 4.2 0.3 6.6 Evaporation rate (g / h) 1.06 1.06 0.16 0.17 0.15 0.15 0.14 0.15 0.21 1.05 0.11

[0091] Modified silica A1 or A2 is added during the polymerization of polyester fibers No. 1, No. 2 and No. 10. The content of A1 or A2 in the polyester fibers is the same. The breaking strength, breaking productivity, water diffusion time and evaporation rate of the two types of fibers are basically the same.

[0092] Compared with No. 11 polyester fiber, No. 1, No. 2 and No. 10 fibers have basically the same breaking strength and breaking productivity, short water diffusion time and high evaporation rate. It can be seen that the silica dispersion prepared by the present invention improves the moisture absorption and wicking performance of the fiber when applied to polyester fiber, and has little impact on the mechanical properties of the fiber.

[0093] Compared with No. 1 polyester fiber, No. 3 to No. 5 polyester fibers have poor breaking strength, breaking productivity, water diffusion time and evaporation rate. This is because the silica in No. 3 to No. 5 silica dispersions has poor dispersion performance in polyester synthesis, resulting in poor fiber mechanical properties and moisture absorption and wicking properties.

[0094] Compared with No. 1 polyester fiber, No. 6-7 polyester fiber has poor breaking strength, breaking productivity, drip diffusion time and evaporation rate. This is because the dispersion performance of No. 6-7 silica dispersion is poor and it is not well dispersed in polyester polymerization, resulting in poor fiber mechanical properties and moisture absorption and wicking properties.

[0095] Compared with No. 1 polyester fiber, No. 8 polyester fiber has poorer breaking strength, breaking productivity, water diffusion time, and evaporation rate. This is because the modifier of No. 8 silica dispersion does not contain acrylamide derivatives, and the dispersibility of silica dispersion is relatively poor.

[0096] Compared to No. 1 polyester fiber, the commercially available silica used in No. 9 polyester fiber has poor dispersion performance in ethylene glycol and polyester. No. 9 polyester fiber has poor breaking strength, breaking productivity, water droplet diffusion time and evaporation rate.

[0097] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any modifications or equivalent transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A silica dispersion, characterized in that, Based on mass parts, each 100 parts of silica dispersion contains the following components: 5-20 parts of modified silica and 80-95 parts of ethylene glycol; wherein the modified silica is prepared by modifying silica with a hydrophilic modifier and a lipophilic modifier, the hydrophilic modifier being a copolymer obtained by polymerizing an acrylamide derivative, sodium styrene sulfonate, and maleic anhydride, and the lipophilic modifier being a lipophilic silane coupling agent; the lipophilic silane coupling agent is selected from at least one of phenyltrimethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, and octadecyltrimethoxysilane; The anhydride groups of the hydrophilic modifier react with the hydroxyl groups of silica to graft the hydrophilic groups onto the silica surface; the methoxy / ethoxy groups of the lipophilic modifier react with the hydroxyl groups of silica after hydrolysis to graft the lipophilic groups onto the silica surface. The acrylamide derivative has the structure shown in general formula (I): ； In general formula (Ⅰ), R1, R2, and R3 may be the same or different, and each is independently selected from H or methyl; R4 is one of alkane group or aromatic group; M is one of Na, K, and H.

2. The silica dispersion according to claim 1, characterized in that, The acrylamide derivative is selected from one of 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamido-2-methylpropanesulfonate, sodium 4-acrylamidobenzenesulfonate, and sodium p-methacrylamidobenzenesulfonate.

3. The silica dispersion according to claim 1, characterized in that, The silica is nano-silica prepared by a gas-phase method.

4. A method for preparing the silica dispersion according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Hydrophilic modification A hydrophilic modifier was obtained by polymerization of acrylamide derivatives, sodium styrene sulfonate, and maleic anhydride under inert gas protection using potassium persulfate and sodium bisulfite as initiators. An aqueous solution of silica was added to the hydrophilic modifier to carry out a hydrophilic modification reaction. After the reaction, the silica was filtered, washed, and dried to obtain hydrophilic silica. (2) Lipophilic modification An oleophilic modifier was added to an aqueous solution of hydrophilic silica, and the mixture was heated under inert gas protection. After the reaction, the silica was filtered, washed, and dried to obtain the modified silica. (3) Preparation of silica dispersion The modified silica and ethylene glycol are mixed according to the formula and dispersed evenly by mechanical stirring to obtain a silica dispersion.

5. The method for preparing the silica dispersion according to claim 4, characterized in that, In step (1), the mass ratio of acrylamide derivative, sodium styrene sulfonate, and maleic anhydride is (1-3):(1-3):

1.

6. The method for preparing the silica dispersion according to claim 4, characterized in that, The mass of the hydrophilic modifier is 1 to 3% of the mass of silica; the mass of the lipophilic modifier is 1 to 3% of the mass of the hydrophilic silica.

7. The method for preparing the silica dispersion according to claim 4, characterized in that, In step (1), the heating temperature is 50-70℃, the polymerization reaction time is 2-6h, and the hydrophilic modification reaction time is 1-4h; in step (2), the heating temperature is 70-90℃, and the reaction time is 1-4h.

8. The use of the silica dispersion according to any one of claims 1 to 3 in in-situ polymerization of polyester.

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