A diluent, its preparation method and use

Abstract

The present application belongs to the technical field of chemical materials, and relates to a diluent, a preparation method and application thereof. The diluent is prepared by using liquid butyronitrile, ethyl acetate and the like as organic components, matching nano-silicon dioxide, a complex of trisodium phosphate and sodium dihydrogen phosphate, silane coupling agent modified nano-cellulose and polyethylene glycol water-based dispersant, and the balance is deionized water. By controlling the mass ratio of nano-silicon dioxide and modified cellulose (1:0.5-2) and the ratio of phosphate (1:0.5-2), the modified cellulose is prepared by combining lye dispersion, silane coupling agent modification and freeze-drying process, and then the diluent is prepared by nano-suspension preparation, organic phase mixing and kerosene adjustment. The product has the characteristics of low viscosity and low surface tension, and can be applied to the production of dust-free mixtures of automobile brake materials. By spraying or mixing, a dense antistatic film is formed, dust is effectively inhibited, and the environmental protection and industrial safety requirements are met.

Description

Technical Field

[0001] This invention belongs to the field of chemical materials technology, and relates to a diluent, its preparation method and application. Background Technology

[0002] Dust control has long been a technical challenge in the preparation of high-performance mixtures such as automotive brake materials. Dust generated during mixing, transportation, and packaging not only pollutes the working environment but also threatens the respiratory health of operators and may even pose a risk of combustion and explosion due to static electricity buildup. Current dust control technologies mainly use volatile organic solvents, such as acetone and xylene, as diluents to suppress dust particles by encapsulating them. However, these solvents are highly volatile, and VOC emission concentrations often exceed 50 mg / m³. 3 This can easily lead to air pollution in the work environment, and organic film-forming materials are prone to breakage due to mechanical friction, resulting in short dust suppression time.

[0003] Existing diluents have significant shortcomings in terms of environmental friendliness and long-lasting dust suppression, making them unsuitable for fields with stringent dust control requirements, such as automotive brake materials. Therefore, there is an urgent need to develop a new type of diluent that achieves a balance between high-stability dispersion, long-lasting dust suppression, and antistatic properties. Summary of the Invention

[0004] The purpose of this invention is to provide a diluent, its preparation method, and its application, which has the characteristic of good dust suppression effect.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A diluent comprising the following components (by mass percentage): 5%–8% liquid nitrile, 15%–24% ethyl acetate, 1%–3% light kerosene, 0.5%–2% nano-silica, 0.1%–1% phosphate inorganic compounds, 0.3%–1.5% silane coupling agent modified nanocellulose, 0.5%–2% aqueous dispersant, with the balance being deionized water;

[0007] The mass ratio of the nano-silica to the modified nano-cellulose is 1:0.5~2.

[0008] The nano-silica has a specific surface area of ​​150~300m² / g and a surface hydroxyl content ≥3.0mmol / g;

[0009] The phosphate inorganic compound is a mixture of trisodium phosphate and sodium dihydrogen phosphate in a mass ratio of 1:0.5~2;

[0010] The preparation method of the silane coupling agent modified nanocellulose is as follows.

[0011] S1: Disperse nanocellulose in an alkaline solution with pH=10~12, add silane coupling agent KH-550, and mix and stir at 400~600r / min for 2~4h at 60~80℃ to obtain a solid-liquid mixture;

[0012] S2: After centrifugation and washing with water, the solid-liquid mixture is freeze-dried to obtain modified nanocellulose.

[0013] Furthermore, the aqueous dispersant is polyethylene glycol, with a homogeneous molecular weight of 2000-3000.

[0014] Furthermore, the nanocellulose is lignocellulose with a fiber diameter ≤50nm.

[0015] Furthermore, the alkaline solution in S1 is at least one of sodium hydroxide and potassium hydroxide.

[0016] Furthermore, the solid-liquid mass ratio (w / v) of nanocellulose and alkaline solution in S1 is 5%, and the mass of silane coupling agent KH-550 added is 5~15% based on the mass of nanocellulose.

[0017] Furthermore, the freeze-drying parameters in S2 are: pre-freezing temperature -40~-50℃, vacuum degree ≤10Pa, and drying time 48~72h.

[0018] Furthermore, the modified nanocellulose obtained in S2 has a water content of ≤2.0%.

[0019] A method for preparing a diluent, the method comprising the following steps:

[0020] A1: Add nano-silica, phosphate inorganic compounds and aqueous dispersant to deionized water and stir at 300~500 r / min for 1~2 h to form a nano suspension;

[0021] A2: Add liquid nitrile butadiene and ethyl acetate to the suspension and ultrasonically disperse at 50~70℃ for 30~60min;

[0022] A3: Add light kerosene and stir at 100-200 r / min for 20-30 min to obtain the diluent with a pH of 6-8.

[0023] An application of a diluent that can be used in the production of dust-free mixtures for automotive brake material preparation, forming a dense antistatic film on the surface of the material through a spraying or mixing process.

[0024] This invention provides a diluent, its preparation method, and its application. By optimizing the ratio of each component and the synergistic effect of specific parameters, it exhibits significant advantages in terms of environmental friendliness, dispersion stability, long-lasting dust suppression, and antistatic properties.

[0025] The mass ratio of nano-silica to silane coupling agent-modified nanocellulose is 1:0.5~2, a ratio set based on the functional complementarity and interfacial synergistic effect of the two nanomaterials. The high specific surface area (150~300 m² / g) of nano-silica provides a large number of surface hydroxyl groups, enabling it to preferentially adsorb dust particles through hydrogen bonding, while simultaneously forming chemical cross-links with the amino or siloxane groups on the surface of the silane coupling agent-modified nanocellulose. After modification with the silane coupling agent KH-550 under alkaline conditions, the surface hydroxyl groups of the nanocellulose are partially replaced, forming a compatible interface with the inorganic phase, thereby constructing a three-dimensional network structure in the mixed system. When the ratio of nano-silica to modified nanocellulose is controlled at 1:0.5~2, the rigid framework of nano-silica and the flexible long chains of cellulose form an interpenetrating network, avoiding both agglomeration of individual nanoparticles due to excessively high interfacial energy and a surge in system viscosity caused by excessive cellulose. The synergistic effect at this ratio can significantly improve the dispersion stability of the suspension and form a dense structure during film formation, effectively blocking dust escape.

[0026] The synergistic effect of the high specific surface area and hydroxyl content of nano-silica provides dual protection for dust adsorption and antistatic functions. Nano-silica with a specific surface area ≥150 m² / g possesses abundant surface active sites, capable of physically adsorbing dust particles with an adsorption capacity of 1.5–2 times its own mass. Hydroxyl groups form hydrogen bonds with the ether oxygen bonds of polyethylene glycol, enhancing the wettability of nanoparticles in aqueous phases. Simultaneously, the surface hydroxyl groups interact with phosphate ions (… The electrostatic effect of the hydroxyl group can adjust the zeta potential to -30 to -40 mV (absolute value > 20 mV), thereby inhibiting the aggregation of nanoparticles through charge repulsion. In addition, the surface hydroxyl groups act as proton donors and can form ion-dipole interactions with the amino groups in the modified nanocellulose, further enhancing the bonding strength of the inorganic-organic interface and effectively reducing the surface resistivity of the antistatic layer after film formation.

[0027] In this invention, a phosphate-based inorganic compound system is used, consisting of trisodium phosphate and sodium dihydrogen phosphate in a mass ratio of 1:0.5-2. Through a dual mechanism of buffering pH and regulating ionic strength, the long-term stability and film uniformity of the nano-suspension are achieved. The weakly alkaline trisodium phosphate and weakly acidic sodium dihydrogen phosphate, mixed in a 1:0.5-2 ratio, can form a buffer environment of pH 6-8 in the diluent system, avoiding the abrupt pH changes caused by a single phosphate. An appropriate ion concentration maintains the ionic strength of the system and prevents nanoparticle flocculation caused by double-layer compression. The dissociation equilibrium of the two at this ratio ( The concentration of anions in the solution can be dynamically adjusted to make the surface charge distribution of nano-silica uniform, and finally form a homogeneous film layer with uniform thickness in the spraying or mixing process.

[0028] Furthermore, the preparation parameters and freeze-drying process of silane coupling agent-modified nanocellulose in this invention ensure the morphological integrity and interfacial activity of the cellulose nanofibers. Under alkaline conditions of pH 10-12, some crystalline regions of the nanocellulose are destroyed, exposing more hydroxyl groups for grafting with the silane coupling agent. Simultaneously, the alkaline environment promotes the hydrolysis of KH-550 to generate silanols (Si-OH), which condense with the hydroxyl groups of cellulose to form Si-OC bonds. A solid-liquid ratio of 5% balances reaction efficiency and dispersion uniformity: if the solid content is too low, the cellulose dispersion is too thin, leading to uneven modification; if the solid content is too high, the increased local viscosity hinders the diffusion of KH-550. With an addition of 5-15% KH-550, 0.2-0.5 mmol of amino groups can be grafted onto each gram of cellulose. This avoids the decrease in fiber rigidity caused by excessive silane and ensures that the modified cellulose has moderate hydrophobicity, allowing it to bind tightly with nano-silica in the diluent and be compatible with the light kerosene fraction of the non-polar component, reducing the tendency for phase separation. The freeze-drying process retains the nanoscale diameter and high aspect ratio of the fiber through deep dehydration (moisture content ≤2.0%), thereby enhancing the toughness of the membrane layer through mechanical interlocking and chemical bonding in subsequent applications. The tear resistance is 2-3 times higher than that of unmodified cellulose.

[0029] Finally, the synergistic addition of light kerosene and liquid nitrile butadiene nitrile achieves a balance between low volatility and rapid film formation. As a non-polar solvent, light kerosene reduces the surface tension of the diluent, promoting its penetration into the material's pores. Meanwhile, the acrylonitrile groups (-C≡N) in the liquid nitrile butadiene nitrile combine with phosphate ions through dipole interactions, forming a continuous phase after water evaporation, thus accelerating film curing. When the ratio of the two is controlled at 1:2.5~8, the lubricating effect of kerosene reduces the impact and rebound of atomized droplets during spraying, improving film formation efficiency. The polar groups of nitrile butadiene nitrile synergistically work with the nanocomposite network to maintain the film's flexibility within the range of -20~120℃, preventing brittleness caused by temperature changes. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0031] Example 1

[0032] Diluent components: 6% liquid nitrile, 18% ethyl acetate, 2% light kerosene, 1% nano silica, 0.5% mixture of trisodium phosphate and sodium dihydrogen phosphate (mass ratio 1:1), 0.8% silane coupling agent modified nanocellulose, 1% polyethylene glycol (molecular weight 2500), and the balance is deionized water;

[0033] Preparation steps of silane coupling agent modified nanocellulose:

[0034] Alkali solution preparation: Weigh 5g of lignocellulose with a fiber diameter ≤50nm, disperse it in 100mL of sodium hydroxide solution with pH=11, and stir at 500r / min for 30min until it is uniformly dispersed.

[0035] Silane coupling agent modification: Add 0.5g of silane coupling agent KH-550 to the suspension, heat to 70℃, and stir at 500r / min for 3h to form a solid-liquid mixture;

[0036] Post-processing: The mixture was centrifuged, washed three times with deionized water, transferred to a freeze dryer, pre-frozen at -45℃, vacuum degree 8Pa, and dried for 60h to obtain modified nanocellulose with a moisture content of 1.5%.

[0037] Diluent preparation steps:

[0038] Preparation of nano suspension: 1g of nano silica with a specific surface area of ​​200m² / g and a surface hydroxyl content of 3.5mmol / g, 0.25g of trisodium phosphate, 0.25g of sodium dihydrogen phosphate and 1g of polyethylene glycol were added to 88.45g of deionized water and stirred at 400r / min for 1.5h to form a uniform suspension.

[0039] Organic phase mixing: Add 6g of liquid butyronitrile and 18g of ethyl acetate to the suspension, heat to 60℃, and ultrasonically disperse for 45min to form a semi-transparent emulsion;

[0040] Adding light kerosene: Slowly add 2g of light kerosene, stir at 150r / min for 25min, adjust the pH to 7.0, and obtain a diluent with a viscosity of 80mPa·s and a surface tension of 28mN / m.

[0041] Example 2

[0042] Diluent components: 8% liquid nitrile, 20% ethyl acetate, 1.5% light kerosene, 1.5% nano silica, 0.8% mixture of trisodium phosphate and sodium dihydrogen phosphate (mass ratio 1:1.5), 1.2% silane coupling agent modified nanocellulose, 1.5% polyethylene glycol (molecular weight 2000), and the balance is deionized water;

[0043] Preparation steps of silane coupling agent modified nanocellulose:

[0044] Alkali solution preparation: Weigh 6g of lignocellulose and disperse it in 120mL of potassium hydroxide solution with pH=10. Stir at 400r / min for 40min until completely dispersed.

[0045] Silane coupling agent modification: Add 0.9g KH-550 to the suspension, heat to 65℃, stir at 600r / min for 2.5h to form a milky white mixture;

[0046] Post-processing: After centrifugation, the product was washed three times with water, transferred to a freeze dryer, pre-frozen at -50℃, under a vacuum of 5Pa, and dried for 48 hours to obtain modified nanocellulose with a moisture content of 1.2%.

[0047] Diluent preparation steps:

[0048] Preparation of nano-suspension: 1.5g of nano-silica with a specific surface area of ​​250m² / g and a surface hydroxyl content of 4.0mmol / g, 0.32g of trisodium phosphate, 0.48g of sodium dihydrogen phosphate and 1.5g of polyethylene glycol were added to 85.38g of deionized water and stirred at 500r / min for 1h to form a stable suspension.

[0049] Organic phase mixing: Add 8g of liquid butyronitrile and 20g of ethyl acetate, heat to 55℃, and ultrasonically disperse for 60min to form a uniform emulsion;

[0050] Adding light kerosene: Slowly add 1.5g of light kerosene, stir at 200r / min for 20min, adjust the pH to 6.5, and finally obtain a diluent with a viscosity of 95mPa·s and a surface tension of 26mN / m.

[0051] Example 3

[0052] Diluent components: 5% liquid nitrile, 24% ethyl acetate, 1% light kerosene, 0.8% nano silica, 0.3% mixture of trisodium phosphate and sodium dihydrogen phosphate (mass ratio 1:0.8), 0.5% silane coupling agent modified nanocellulose, 0.8% polyethylene glycol (molecular weight 3000), and the balance is deionized water;

[0053] Preparation steps of silane coupling agent modified nanocellulose:

[0054] Alkali solution preparation: Weigh 3g of lignocellulose and disperse it in 60mL of sodium hydroxide solution with pH=12. Stir at 600r / min for 20min until completely dispersed.

[0055] Silane coupling agent modification: Add 0.15g KH-550 to the suspension, heat to 80℃, stir at 400r / min for 4h to form a light yellow mixture.

[0056] Post-processing: After centrifugation, the product was washed three times with water, transferred to a freeze dryer, pre-frozen at -40℃, under a vacuum of 10Pa, and dried for 72 hours to obtain modified nanocellulose with a moisture content of 1.8%.

[0057] Diluent preparation steps:

[0058] Preparation of nano-suspension: 0.8g of nano-silica with a specific surface area of ​​180m² / g and a surface hydroxyl content of 3.2mmol / g, 0.13g of trisodium phosphate, 0.17g of sodium dihydrogen phosphate and 0.8g of polyethylene glycol were added to 88.5g of deionized water and stirred at 300r / min for 2h to form a stable suspension.

[0059] Organic phase mixing: Add 5g of liquid butyronitrile and 24g of ethyl acetate, heat to 70℃, and ultrasonically disperse for 30min to form a semi-transparent emulsion;

[0060] Adding light kerosene: Slowly add 1g of light kerosene, stir at 100r / min for 30min, adjust the pH to 7.5, and finally obtain a diluent with a viscosity of 70mPa·s and a surface tension of 30mPa·s.

[0061] Comparative Example 1

[0062] This comparative example uses only trisodium phosphate as the inorganic phosphate compound, and the remaining steps are the same as in Example 2.

[0063] The diluent prepared in this comparative example has a viscosity of 110 mPa·s and a surface tension of 30 mN / m.

[0064] Comparative Example 2

[0065] This comparative example uses only sodium dihydrogen phosphate as the inorganic phosphate compound, and the remaining steps are the same as in Example 2.

[0066] The diluent prepared in this comparative example has a viscosity of 105 mPa·s and a surface tension of 29 mN / m.

[0067] Comparative Example 3

[0068] This comparative example does not use silane coupling agents to modify nanocellulose; it only uses nanocellulose, and the remaining steps are the same as in Example 2.

[0069] The diluent prepared in this comparative example has a viscosity of 120 mPa·s and a surface tension of 32 mN / m.

[0070] After mixing the diluents and mixtures prepared in the examples and comparative examples, dynamic dust concentration was measured. The testing method referred to standard GBZ / T 192.6-2018. The test results are shown in the table below.

[0071]

[0072] The experimental data above show that when trisodium phosphate and sodium dihydrogen phosphate are combined, the pH buffering effect can maintain the surface charge stability of nanoparticles, significantly reduce viscosity and surface tension, and improve film uniformity; the modified nanocellulose, through hydrophobic groups ( It is compatible with organic phases, while retaining the combination of hydroxyl groups with inorganic phases to form strong interfacial interactions, effectively improving the film density by more than 3 times; single phosphate or unmodified cellulose will lead to phase separation and increased film defects in the system, ultimately resulting in a significant decrease in dust suppression efficiency.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A diluent, characterized in that, The diluent consists of the following components: 5%–8% liquid nitrile, 15%–24% ethyl acetate, 1%–3% light kerosene, 0.5%–2% nano-silica, 0.1%–1% phosphate inorganic compounds, 0.3%–1.5% silane coupling agent modified nanocellulose, 0.5%–2% aqueous dispersant, and the balance being deionized water. The mass ratio of the nano-silica to the modified nano-cellulose is 1:0.5~2. The nano-silica has a specific surface area of ​​150~300m² / g and a surface hydroxyl content ≥3.0mmol / g; The phosphate inorganic compound is a mixture of trisodium phosphate and sodium dihydrogen phosphate in a mass ratio of 1:0.5~2; The aqueous dispersant is polyethylene glycol, with a mass-average molecular weight of 2000-3000. The preparation method of the silane coupling agent modified nanocellulose is as follows: S1: Disperse nanocellulose in an alkaline solution with pH=10~12, add silane coupling agent KH-550, and mix and stir at 400~600r / min for 2~4h at 60~80℃ to obtain a solid-liquid mixture; S2: After centrifugation and washing with water, the solid-liquid mixture is freeze-dried to obtain modified nanocellulose; The method for preparing the diluent includes the following steps: A1: Add nano-silica, phosphate inorganic compounds and aqueous dispersant to deionized water and stir at 300~500 r / min for 1~2 h to form a nano suspension; A2: Add liquid nitrile butadiene and ethyl acetate to the suspension and ultrasonically disperse at 50~70℃ for 30~60min; A3: Add light kerosene and stir at 100-200 r / min for 20-30 min to obtain the diluent with a pH of 6-8.

2. The diluent according to claim 1, characterized in that, The nanocellulose is lignocellulose with a fiber diameter ≤50nm.

3. The diluent according to claim 1, characterized in that, The alkaline solution in S1 is at least one of sodium hydroxide and potassium hydroxide.

4. The diluent according to claim 1, characterized in that, The solid-liquid ratio of nanocellulose and alkaline solution in S1 is 5g:100mL. Based on the mass of nanocellulose, the mass of silane coupling agent KH-550 added is 5~15%.

5. A diluent according to claim 1, characterized in that, The freeze-drying parameters in S2 are: pre-freezing temperature -40~-50℃, vacuum degree ≤10Pa, and drying time 48~72h.

6. The diluent according to claim 1, characterized in that, The modified nanocellulose obtained in S2 has a moisture content of ≤2.0%.

7. The application of a diluent according to any one of claims 1 to 6, characterized in that, The diluent is used in the production of dust-free mixtures for automotive brake materials, forming a dense antistatic film on the material surface through spraying or mixing processes.

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