Perfluoropolyether-coated nano calcium carbonate particles, method for preparing same, and perfluoropolyether grease

Abstract

This invention discloses a perfluoropolyether-coated nano-calcium carbonate particle, its preparation method, and a perfluoropolyether lubricant. The perfluoropolyether-coated nano-calcium carbonate particle comprises nano-calcium carbonate particles, an epoxy resin dynamic crosslinking layer coating the nano-calcium carbonate particles, and perfluoropolyether grafted onto the surface of the epoxy resin dynamic crosslinking layer. Based on 100 wt% of the perfluoropolyether-coated nano-calcium carbonate particles, the amount of the nano-calcium carbonate particles is 70-95 wt%; the amount of the epoxy resin dynamic crosslinking layer is 1-10 wt%; and the amount of the perfluoropolyether is 1-20 wt%. The epoxy resin dynamic crosslinking layer exhibits dynamic crosslinking characteristics under high-temperature conditions. If the carboxyl-terminated perfluoropolyether detaches from the dynamic crosslinking layer under mechanical force, it can return to the surface of the dynamic crosslinking layer through a dynamic crosslinking reaction, thereby ensuring the stability of the perfluoropolyether-coated nano-calcium carbonate structure. This solves the problems of poor stability and easy detachment at high temperatures and over long periods associated with traditional nano-calcium carbonate.

Description

Technical Field

[0001] This invention relates to the field of lubricating materials technology, specifically to a perfluoropolyether-coated nano-calcium carbonate particle, its preparation method, and a perfluoropolyether lubricating grease. Background Technology

[0002] Perfluoropolyethers (PFPEs) are a class of synthetic lubricants with excellent chemical stability and high-temperature resistance, widely used in aerospace, automotive, electronics, and machinery industries. Due to their unique structure, PFPEs maintain good lubrication performance under extreme conditions (such as high temperatures, radiation, strong acids, strong alkalis, and corrosive media), effectively reducing friction and wear. However, the high viscosity and low surface energy of PFPEs make them difficult to integrate well with traditional fillers or additives, limiting their performance optimization in certain applications.

[0003] Nano-calcium carbonate, as a commonly used additive, is widely used in lubricating greases due to its excellent anti-wear properties and cost-effectiveness. Traditional nano-calcium carbonate is a hydrophilic inorganic compound with multiple hydroxyl groups, resulting in poor dispersibility and stability in hydrophobic perfluoropolyether matrices, thus affecting the performance of the final product. While directly modifying the end groups of perfluoropolyether and grafting them onto the surface of nano-calcium carbonate can temporarily enhance its dispersibility in perfluoropolyether greases, the grafted perfluoropolyether detaches from the nano-calcium carbonate surface with prolonged use under high-temperature conditions, leading to a decrease in the dispersibility of nano-calcium carbonate in perfluoropolyether greases over extended use.

[0004] Therefore, there is an urgent need for a perfluoropolyether-grafted nano-calcium carbonate with good dispersibility in perfluoropolyether grease, so as to further produce perfluoropolyether grease with good anti-wear properties and low bearing temperature rise. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides perfluoropolyether-coated nano-calcium carbonate particles, their preparation method, and perfluoropolyether grease. The perfluoropolyether-coated nano-calcium carbonate particles provided by this invention improve the dispersibility and stability of nano-calcium carbonate particles in perfluoropolyether grease. Compared with perfluoropolyether grease containing ordinary nano-calcium carbonate particles, perfluoropolyether grease with perfluoropolyether-coated nano-calcium carbonate particles provided by this invention exhibits superior friction resistance and lower bearing temperature rise.

[0006] To solve the above-mentioned technical problems, the first aspect of the present invention provides a perfluoropolyether-coated nano-calcium carbonate particle, wherein the perfluoropolyether-coated nano-calcium carbonate particle includes nano-calcium carbonate particles, an epoxy resin dynamic crosslinking layer coating the nano-calcium carbonate particles, and perfluoropolyether grafted onto the surface of the epoxy resin dynamic crosslinking layer.

[0007] Based on 100 wt% of the perfluoropolyether-coated nano-calcium carbonate particles, the amount of the nano-calcium carbonate particles is 70-95 wt%; the amount of the epoxy resin dynamic crosslinking layer is 1-10 wt%; and the amount of the perfluoropolyether is 1-20 wt%.

[0008] In this invention, the surface of nano-calcium carbonate particles is modified through a dynamic crosslinking reaction. First, an epoxy resin dynamic crosslinking layer is coated onto the surface of the nano-calcium carbonate particles, and then perfluoropolyether is grafted onto the dynamic crosslinking layer. The epoxy resin dynamic crosslinking layer exhibits dynamic crosslinking characteristics under high-temperature conditions. If the perfluoropolyether detaches from the dynamic crosslinking layer under mechanical force, it can return to the surface of the dynamic crosslinking layer through a dynamic crosslinking reaction, thereby ensuring the stability of the perfluoropolyether-coated nano-calcium carbonate particles. Furthermore, by adjusting the content of nano-calcium carbonate particles, the epoxy resin dynamic crosslinking layer, and the perfluoropolyether in the perfluoropolyether-coated nano-calcium carbonate particles, the stability of the perfluoropolyether-coated nano-calcium carbonate particles is further enhanced.

[0009] In some embodiments of the present invention, the epoxy resin dynamic crosslinking layer is formed by a crosslinking curing reaction of raw materials including epoxy resin, acid anhydride compound, and triethanolamine.

[0010] In some embodiments of the present invention, the molar ratio of the epoxy resin, the acid anhydride compound and the triethanolamine is 1:(1-1.2):(0.05-0.15).

[0011] In some embodiments of the present invention, the dynamic crosslinking layer contains one or more of ester bonds, ether bonds, hydroxyl groups, carboxyl groups, and tertiary amine groups.

[0012] In this invention, the epoxy resin dynamic crosslinking layer coating nano-calcium carbonate undergoes a series of chemical reactions, including but not limited to: the hydroxyl groups in triethanolamine react with the anhydride groups in the anhydride compound to form ester bonds and carboxylic acid groups; the resulting carboxylic acid groups react with the epoxy groups in the epoxy resin to form ester bonds and hydroxyl groups; the tertiary amine groups in triethanolamine initiate the ring-opening of the anhydride groups in the anhydride compound to generate carboxylic acid anions; the carboxylic acid anions initiate the ring-opening of the epoxy groups in the epoxy resin to generate ester bonds and hydroxyl anions; the hydroxyl anions initiate the ring-opening of the epoxy groups in the epoxy resin to generate ether bonds and oxygen anions. Through the above complex crosslinking reactions, a dynamic crosslinking network structure containing ester bonds, ether bonds, hydroxyl groups, carboxyl groups, and tertiary amine groups is finally formed. In the dynamic crosslinking network, through the interaction of tertiary amine groups, ester bonds with ester bonds, ester bonds with hydroxyl groups, and ester bonds with carboxyl groups continuously undergo dynamic transesterification reactions above 200°C, hence the name dynamic crosslinking network. Further adjusting the molar ratio of epoxy resin, anhydride compound, and triethanolamine in the epoxy resin dynamic crosslinking layer increases the stability of the dynamic crosslinking network.

[0013] In some embodiments of the present invention, the epoxy resin is selected from bisphenol A type epoxy resin, aliphatic epoxy resin or alicyclic epoxy resin.

[0014] In some embodiments of the present invention, the anhydride compound is a monofunctional anhydride; preferably selected from methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, or dodecyl succinic anhydride.

[0015] In some embodiments of the present invention, the segmental structural formula of the perfluoropolyether is as follows:

[0016]

[0017] In equation (I), m and n are both integers, m≥1, n≥1.

[0018] In some embodiments of the present invention, 10≤m≤40, 10≤n≤40.

[0019] A second aspect of the present invention provides a method for preparing perfluoropolyether-coated nano-calcium carbonate particles, comprising the following steps:

[0020] (1) Provide carboxyl-terminated perfluoropolyether; (2) Coat the nano-calcium carbonate particles with an epoxy resin dynamic crosslinking layer to obtain an epoxy resin dynamic crosslinking layer coating the nano-calcium carbonate particles; (3) The carboxyl-terminated perfluoropolyether is grafted onto the surface of the epoxy resin dynamic crosslinking layer through an ester exchange reaction and / or an esterification reaction to obtain perfluoropolyether-coated nano-calcium carbonate particles.

[0021] In this invention, the main reactions involved in grafting carboxyl-terminated perfluoropolyether onto the epoxy resin dynamic crosslinking layer are transesterification reactions between the carboxyl groups in the carboxyl-terminated perfluoropolyether and the ester bonds in the epoxy resin dynamic crosslinking network, and / or dehydration esterification reactions between the carboxyl groups in the carboxyl-terminated perfluoropolyether and the hydroxyl groups in the dynamic crosslinking network. Through the above transesterification and dehydration esterification reactions, monocarboxyl-terminated perfluoropolyether is grafted onto the epoxy resin dynamic crosslinking layer.

[0022] In some embodiments of the present invention, in step (1), the terminal acyl fluoride perfluoropolyether of formula (II) is hydrolyzed in concentrated sulfuric acid to obtain the terminal carboxyl perfluoropolyether of formula (III).

[0023]

[0024] In equations (II) and (III), m and n are both integers, m≥1, n≥1.

[0025] In some embodiments of the present invention, 10≤m≤40, 10≤n≤40.

[0026] In some embodiments of the present invention, in step (2), epoxy resin, acid anhydride compound, and triethanolamine are first mixed to obtain liquid mixture I; liquid mixture I is second mixed with nano-calcium carbonate particles to obtain semi-solid mixture II; semi-solid mixture II is ball-milled to obtain nano-calcium carbonate coated with a dynamic cross-linking layer of epoxy resin.

[0027] In some embodiments of the present invention, in step (3), the carboxyl-terminated perfluoropolyether and the epoxy resin dynamic crosslinking layer-coated nano-calcium carbonate are mixed for the third time to obtain a semi-solid mixture III; the semi-solid mixture III is ball-milled to obtain perfluoropolyether-coated nano-calcium carbonate particles.

[0028] In some embodiments of the present invention, the weight-average molecular weight of the terminal acyl fluoride perfluoropolyether in step (1) is 2500 g / mol to 5000 g / mol, for example, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, or 5000 g / mol.

[0029] In some embodiments of the present invention, the hydrolysis conditions in step (1) include: a hydrolysis temperature of 15°C to 40°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C, or 40°C, preferably 20°C to 25°C; a hydrolysis time of 6h to 12h, for example, 6h, 7h, 8h, 9h, 10h, 11h, or 12h, preferably 10h to 12h; and a stirring rate of 200 to 300 rpm, for example, 200 rpm, 220 rpm, 240 rpm, 250 rpm, 260 rpm, 280 rpm, or 300 rpm.

[0030] In some embodiments of the present invention, the mass ratio of the terminal acyl fluoride perfluoropolyether to the concentrated sulfuric acid in step (1) is (100-120):1, for example, 100:1, 110:1, 120:1.

[0031] In some embodiments of the present invention, in step (2), the conditions for the first mixing include a temperature of 20°C to 25°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C, or 25°C.

[0032] In some embodiments of the present invention, the molar ratio of the epoxy resin to the anhydride compound is 1:(1 to 1.5), for example, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5.

[0033] In some embodiments of the present invention, the molar ratio of the epoxy resin to the triethanolamine is 1:(0.05-0.2), for example 1:0.05, 1:0.08, 1:0.09, 1:0.10, 1:0.12, 1:0.15, or 1:0.2.

[0034] In some embodiments of the present invention, in the second mixing in step (2), the mass ratio of the liquid mixture I to the nano-calcium carbonate particles is 1:(10-20), for example 1:10, 1:12, 1:15, 1:16, 1:18, or 1:20.

[0035] In some embodiments of the present invention, in step (2), the conditions for ball milling include: the volume ratio of the grinding balls to the semi-solid mixture II is (1.6 to 3):1; the ball milling is carried out in the ball mill jar of a ball mill, and the sum of the volume of the grinding balls and the volume of the semi-solid mixture II is less than two-thirds of the total volume of the ball mill jar; the ball milling temperature is 150°C to 200°C, the stirring rate is 50 to 240 rpm, and the ball milling time is 3 to 5 hours.

[0036] In some embodiments of the present invention, the ball milling in step (2) includes: first ball milling at a speed of 50-70 rpm for 50-90 min, then ball milling at a speed of 80-120 rpm for 50-90 min, then ball milling at a speed of 130-170 rpm for 50-90 min, and finally ball milling at a speed of 180-240 rpm for 20-40 min.

[0037] In some embodiments of the present invention, in step (3), in the third mixture, the mass ratio of the nano-calcium carbonate coated by the epoxy resin dynamic crosslinking layer to the carboxyl-terminated perfluoropolyether is (99:1) to (80:20).

[0038] In some embodiments of the present invention, in step (3), the conditions for ball milling include: the volume ratio of the grinding balls to the semi-solid mixture III is (1.6 to 3):1; the ball milling is carried out in the ball mill jar of a ball mill, and the sum of the volume of the grinding balls and the volume of the semi-solid mixture III is less than two-thirds of the total volume of the ball mill jar; the ball milling temperature is 150°C to 200°C, the stirring rate is 50 to 240 rpm, and the ball milling time is 3 to 5 hours.

[0039] In some embodiments of the present invention, the ball milling in step (3) includes: first ball milling at a speed of 50-70 rpm for 50-90 min, then ball milling at a speed of 80-120 rpm for 50-90 min, then ball milling at a speed of 130-170 rpm for 50-90 min, and finally ball milling at a speed of 180-240 rpm for 20-40 min.

[0040] A third aspect of the present invention provides a perfluoropolyether grease, wherein the perfluoropolyether grease comprises the above-mentioned perfluoropolyether-coated nano-calcium carbonate particles or the perfluoropolyether-coated nano-calcium carbonate particles prepared by the above-mentioned preparation method.

[0041] In this invention, the perfluoropolyether grease using the above-mentioned perfluoropolyether-coated nano-calcium carbonate particles exhibits superior friction resistance and lower bearing temperature rise compared to the perfluoropolyether grease with added ordinary nano-calcium carbonate particles.

[0042] In some embodiments of the present invention, the perfluoropolyether grease comprises the following components by mass percentage:

[0043] Perfluoropolyether base oil 50%–90%; thickener 5%–40%; perfluoropolyether-coated nano-calcium carbonate particles 0.5%–15%.

[0044] In this invention, the amount of perfluoropolyether base oil, thickener and perfluoropolyether-coated nano-calcium carbonate material added is further controlled. The resulting perfluoropolyether grease has low oil separation and good friction and wear performance, and can be applied to bearing conditions such as high speed and heavy load where bearing temperature rise needs to be controlled.

[0045] In some embodiments of the present invention, the perfluoropolyether base oil is selected from at least one of the perfluoropolyether base oils of formula (IV) or formula (V);

[0046]

[0047] In equations (IV) and (V), m, n, p, and q are all integers, m / n = 0.2 to 25, and p / q = 20 to 50;

[0048] In equations (IV) and (V), Rf1 and Rf2 may be the same or different, and Rf1 and Rf2 are each independently selected from -CF3, -C2F5, -C3F7 or -CF(CF3)OCF3.

[0049] In some embodiments of the present invention, the weight-average molecular weight of the perfluoropolyether base oil is 2000 g / mol to 20000 g / mol, for example, 2000 g / mol, 3000 g / mol, 5000 g / mol, 8000 g / mol, 10000 g / mol, 15000 g / mol, or 20000 g / mol.

[0050] In some embodiments of the present invention, the average particle size of the thickener is 0.1 μm to 20 μm, preferably 1 μm to 10 μm.

[0051] In some embodiments of the present invention, the weight-average molecular weight of the thickener is 1 × 10⁻⁶.4 g / mol~1×10 6 g / mol.

[0052] In some embodiments of the present invention, the specific surface area of ​​the thickener is 2m². 2 / g~50m 2 / g, preferably 10m 2 / g~20m 2 / g; melting point is 320℃~340℃.

[0053] In some embodiments of the present invention, the thickener is polytetrafluoroethylene.

[0054] In some embodiments of the present invention, the perfluoropolyether grease has a steel mesh oil separation of less than 6%, a wear scar diameter of less than 0.6 mm, and a coefficient of friction of less than 0.09.

[0055] A fourth aspect of the present invention provides a method for preparing perfluoropolyether grease, comprising mixing and grinding perfluoropolyether-coated nano-calcium carbonate particles, perfluoropolyether base oil and thickener to obtain the perfluoropolyether grease.

[0056] In some embodiments of the present invention, the thickener is pre-treated by drying before mixing the perfluoropolyether-coated nano-calcium carbonate particles, the perfluoropolyether base oil, and the thickener.

[0057] In some embodiments of the present invention, the preparation method of the perfluoropolyether grease specifically includes the following steps:

[0058] (1) Under the condition of a temperature of 20℃~60℃, the nano-calcium carbonate particles coated with perfluoropolyether are added to the perfluoropolyether base oil and stirred and mixed evenly to obtain a mixture.

[0059] (2) Place the thickener in an oven at a temperature of 105-115℃ and bake for 4-6 hours for drying pretreatment;

[0060] (3) Add the pretreated thickener from step (2) to the mixture obtained in step (1) and stir to obtain a paste blend;

[0061] (4) Grind the paste blend obtained in step (3) 3 to 5 times at room temperature using a three-roll mill to obtain an oily grease, namely the perfluoropolyether grease.

[0062] Beneficial effects:

[0063] This invention modifies the surface of nano-calcium carbonate particles through dynamic crosslinking. The perfluoropolyether-coated nano-calcium carbonate particles include nano-calcium carbonate particles, an epoxy resin dynamic crosslinking layer coating the nano-calcium carbonate particles, and perfluoropolyether grafted onto the surface of the epoxy resin dynamic crosslinking layer. The epoxy resin dynamic crosslinking layer exhibits dynamic crosslinking characteristics under high-temperature conditions. If the carboxyl-terminated perfluoropolyether detaches from the dynamic crosslinking layer under mechanical force, it can return to the surface of the dynamic crosslinking layer through a dynamic crosslinking reaction, thereby ensuring the stability of the perfluoropolyether-coated nano-calcium carbonate particles. This solves the problems of poor stability and easy detachment at high temperatures and over long periods of time associated with traditional nano-calcium carbonate. Furthermore, by adjusting the content of nano-calcium carbonate particles, the epoxy resin dynamic crosslinking layer, and the perfluoropolyether in the perfluoropolyether-coated nano-calcium carbonate particles, the stability of the perfluoropolyether-coated nano-calcium carbonate particles is further enhanced.

[0064] The perfluoropolyether-coated nano-calcium carbonate particles of the present invention can be uniformly dispersed in perfluoropolyether grease, solving the problem of poor compatibility between traditional nano-calcium carbonate particles and perfluoropolyether base oil. Furthermore, due to their ability to maintain long-term stability and dispersibility, the addition of the above-mentioned perfluoropolyether-coated nano-calcium carbonate particles can produce perfluoropolyether grease with good anti-wear performance, low oil separation, and low bearing temperature rise.

[0065] The perfluoropolyether grease prepared by adding nano-calcium carbonate particles coated with perfluoropolyether as described in this invention has low oil separation and good friction and wear performance, and can be applied to high-speed, heavy-load and other working conditions that require control of bearing temperature rise. Attached Figure Description

[0066] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0067] Figure 1 Schematic diagram of perfluoropolyether-coated nano-calcium carbonate particles;

[0068] Figure 2 Bearing temperature rise diagrams for Preparation Examples 1-3 and Comparative Preparation Examples 1-3. Detailed Implementation

[0069] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments and accompanying drawings. These embodiments are for illustrative purposes only and should not be considered as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the materials used in the embodiments are commercially available products or conventional products that can be synthesized by known methods.

[0070] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0071] The perfluoropolyether-coated nano-calcium carbonate particles of the present invention have the following structure: Figure 1 As shown:

[0072] Figure 1 In the process, the epoxy resin dynamic cross-linking layer is a dynamic cross-linked cured structure formed by epoxy resin, acid anhydride compound, and triethanolamine, and the perfluoropolyether grafted layer is a perfluoropolyether with carboxyl-terminated groups grafted onto the epoxy resin dynamic cross-linking layer.

[0073] Figure 1 The structural formula of the segments of perfluoropolyether:

[0074]

[0075] In formula (I), m and n are both integers, m≥1, n≥1; preferably, 10≤m≤40, 10≤n≤40.

[0076] Figure 1 R1 is the structural formula:

[0077] -CH2-CH2-. (VI)

[0078] Figure 1 R2 is the structural formula:

[0079]

[0080] For ease of explanation and understanding, Figure 1 The cross-linking network structure of the epoxy resin dynamic cross-linking layer is described using E51 type bisphenol A epoxy resin, methylhexahydrophthalic anhydride, and triethanolamine as examples. This does not mean that only these three substances can be used to construct the epoxy resin dynamic cross-linking layer. Among them, E51 type bisphenol A epoxy resin can be replaced with any bisphenol A type epoxy resin, any aliphatic epoxy resin, or any alicyclic epoxy resin. Methylhexahydrophthalic anhydride can be replaced with methyltetrahydrophthalic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, dodecyl succinic anhydride, and other monofunctional anhydrides.

[0081] The terminal acyl fluoride perfluoropolyether, concentrated sulfuric acid, E51 type bisphenol A epoxy resin, E44 type bisphenol A epoxy resin, CELLOXIDE 2021P alicyclic epoxy resin, methyl hexahydrophthalic anhydride, methyl nadic anhydride, triethanolamine, and nano calcium carbonate particles used in the embodiments of this invention are all common commercially available products and can be obtained through commercial purchase.

[0082] The polytetrafluoroethylene and perfluoropolyether base oil used in the preparation examples of this invention are both commercially available products that can be obtained through commercial purchase.

[0083] Unless otherwise specified, the room temperature in the embodiments of this invention is 25°C.

[0084] The present invention will be described in detail below through examples, preparation examples, and test examples.

[0085] Example 1

[0086] Preparation method of perfluoropolyether-coated nano-calcium carbonate particles

[0087] (1) Provide carboxyl-terminated perfluoropolyether

[0088] Take 3500g of terminal acyl fluoride perfluoropolyether with a weight average molecular weight of 3500g / mol (m=13, n=29), add it to 35g of concentrated sulfuric acid, and stir at 200rpm for 12h at 25℃ to obtain terminal carboxyl perfluoropolyether.

[0089] (2) Preparation of epoxy resin dynamic cross-linking layer coated with nano-calcium carbonate

[0090] E51 type bisphenol A epoxy resin (50g, 0.51mol epoxy groups), methyl hexahydrophthalic anhydride (84g, 0.51mol anhydride groups), and triethanolamine (7.45g, 0.05mol tertiary amine groups) were poured into a glass beaker and stirred to form a liquid mixture I. 10g of liquid mixture I was poured into 150g of nano-calcium carbonate particles and stirred to form a semi-solid mixture II. The semi-solid mixture II was added to a ball mill and ball milled using agate grinding balls at a volume ratio of 2:1. The ball milling temperature was controlled between 150℃ and 200℃, and the ball milling program was as follows: 50rpm for 60min, 100rpm for 60min, 150rpm for 60min, and 200rpm for 30min, to obtain nano-calcium carbonate coated with a dynamically cross-linked epoxy resin layer.

[0091] (3) Preparation of perfluoropolyether-coated nano-calcium carbonate particles

[0092] 90g of epoxy resin dynamically cross-linked coated nano-calcium carbonate was mixed with 10g of carboxyl-terminated perfluoropolyether to obtain semi-solid mixture III. The semi-solid mixture III was added to a ball mill and ball milled with agate grinding balls at a volume ratio of 2:1. The ball milling temperature was controlled between 150℃ and 200℃, and the ball milling program was 50rpm for 60min, 100rpm for 60min, 150rpm for 60min, and 200rpm for 30min to obtain perfluoropolyether coated nano-calcium carbonate particles.

[0093] The obtained perfluoropolyether-coated nano-calcium carbonate particles, based on 100 wt%, comprise: 84.4 wt% nano-calcium carbonate particles; 5.6 wt% epoxy resin dynamic crosslinking layer; and 10 wt% perfluoropolyether. In the epoxy resin dynamic crosslinking layer, the molar ratio of epoxy resin, acid anhydride compound, and triethanolamine is 1:1:0.1.

[0094] Example 2

[0095] Preparation method of perfluoropolyether-coated nano-calcium carbonate particles

[0096] (1) Provide carboxyl-terminated perfluoropolyether

[0097] Take 2500g of terminal acyl fluoride perfluoropolyether with a weight average molecular weight of 2500g / mol (m=14, n=13), add it to 25g of concentrated sulfuric acid, and stir at 200rpm for 12h at 25℃ to obtain terminal carboxyl perfluoropolyether.

[0098] (2) Preparation of epoxy resin dynamic cross-linking layer coated with nano-calcium carbonate

[0099] E44 type bisphenol A epoxy resin (50g, 0.44mol epoxy groups), methyl hexahydrophthalic anhydride (87.7g, 0.528mol anhydride groups), and triethanolamine (3.28g, 0.022mol tertiary amine groups) were poured into a glass beaker and stirred to form a liquid mixture I. 10g of liquid mixture I was poured into 100g of nano-calcium carbonate particles and stirred to form a semi-solid mixture II. The semi-solid mixture II was added to a ball mill using agate grinding balls at a volume ratio of 1.6:1. The ball milling temperature was controlled between 150℃ and 200℃, and the ball milling program was as follows: 50rpm for 60min, 100rpm for 60min, 150rpm for 60min, and 200rpm for 30min, to obtain nano-calcium carbonate coated with a dynamically cross-linked epoxy resin layer.

[0100] (3) Preparation of perfluoropolyether-coated nano-calcium carbonate particles

[0101] 85g of epoxy resin dynamically cross-linked coated nano-calcium carbonate was mixed with 15g of carboxyl-terminated perfluoropolyether to obtain semi-solid mixture III. The semi-solid mixture III was added to a ball mill and ball milling was performed using agate grinding balls at a volume ratio of 1.6:1. The ball milling temperature was controlled between 150℃ and 200℃, and the ball milling program was as follows: 50rpm for 60min, 100rpm for 60min, 150rpm for 60min, and 200rpm for 30min to obtain perfluoropolyether coated nano-calcium carbonate particles.

[0102] The obtained perfluoropolyether-coated calcium carbonate nanoparticles, based on 100 wt%, comprise: 77.3 wt% calcium carbonate nanoparticles; 7.7 wt% epoxy resin dynamic crosslinking layer; and 15 wt% perfluoropolyether. In the epoxy resin dynamic crosslinking layer, the molar ratio of epoxy resin, acid anhydride compound, and triethanolamine is 1:1.2:0.05.

[0103] Example 3

[0104] Preparation method of perfluoropolyether-coated nano-calcium carbonate particles

[0105] (1) Provide carboxyl-terminated perfluoropolyether

[0106] Take 5000g of terminal acyl fluoride perfluoropolyether with a weight average molecular weight of 5000g / mol (m=33, n=17), add it to 50g of concentrated sulfuric acid, and stir at 200rpm for 12h at 25℃ to hydrolyze it, thereby obtaining terminal carboxyl perfluoropolyether.

[0107] (2) Preparation of epoxy resin dynamic cross-linking layer coated with nano-calcium carbonate

[0108] CELLOXIDE 2021P alicyclic epoxy resin (50g, 0.77mol epoxy groups), methyl nadic anhydride (151g, 0.847mol anhydride groups), and triethanolamine (14.85g, 0.1mol tertiary amine groups) were poured into a glass beaker and stirred to form a first mixture, resulting in liquid mixture I. 10g of liquid mixture I was poured into 200g of nano-calcium carbonate particles and stirred to form a second mixture, resulting in semi-solid mixture II. The semi-solid mixture II was added to a ball mill using agate grinding balls at a volume ratio of 2.5:1. The ball milling temperature was controlled between 150℃ and 200℃, and the ball milling program was as follows: 50rpm for 60min, 100rpm for 60min, 150rpm for 60min, and 200rpm for 30min, to obtain nano-calcium carbonate coated with a dynamically cross-linked epoxy resin layer.

[0109] (3) Preparation of perfluoropolyether-coated nano-calcium carbonate particles

[0110] 95g of epoxy resin dynamically cross-linked coated nano-calcium carbonate was mixed with 5g of carboxyl-terminated perfluoropolyether to obtain semi-solid mixture III. The semi-solid mixture III was added to a ball mill and ball milled with agate grinding balls at a volume ratio of 2.5:1. The ball milling temperature was controlled between 150℃ and 200℃, and the ball milling program was as follows: 50 rpm for 60 min, 100 rpm for 60 min, 150 rpm for 60 min, and 200 rpm for 30 min to obtain perfluoropolyether coated nano-calcium carbonate particles.

[0111] The obtained perfluoropolyether-coated nano-calcium carbonate particles, based on 100 wt%, comprise: 90.5 wt% nano-calcium carbonate particles; 4.5 wt% epoxy resin dynamic crosslinking layer; and 5 wt% perfluoropolyether. In the epoxy resin dynamic crosslinking layer, the molar ratio of epoxy resin, acid anhydride compound, and triethanolamine is 1:1.1:0.13.

[0112] Comparative Example 1

[0113] Preparation method of perfluoropolyether-coated nano-calcium carbonate particles

[0114] According to step (1) of Example 1, carboxyl-terminated perfluoropolyether is provided, but the nano-calcium carbonate particles are not subjected to the epoxy resin dynamic crosslinking coating in step (2). The perfluoropolyether-coated nano-calcium carbonate is prepared directly according to the preparation method in step (3) of Example 1. The carboxyl-terminated perfluoropolyether and nano-calcium carbonate are ball-milled for coating.

[0115] The obtained perfluoropolyether-coated calcium carbonate nanoparticles, based on 100 wt%, comprise: 90 wt% calcium carbonate nanoparticles and 10 wt% perfluoropolyether.

[0116] Preparation Example 1

[0117] Preparation method of perfluoropolyether grease

[0118] (1) At a temperature of 40°C, 50g of the perfluoropolyether-coated nano-calcium carbonate particles prepared in Example 1 were added to 1000g of the linear perfluoropolyether base oil of Formula (IV) (weight average molecular weight of 6500g / mol, m / n = 3, Rf1 and Rf2 are both selected from -CF3), and stirred and mixed to obtain a mixture.

[0119] (2) Place 250g of polytetrafluoroethylene in an oven at 110℃ and bake for 5 hours for drying pretreatment.

[0120] The average particle size of polytetrafluoroethylene is 5.5 μm, and the weight-average molecular weight is 9.6 × 10⁻⁶. 4 g / mol, specific surface area 16m² 2 / g, melting point is 327℃.

[0121] (3) Add the pretreated polytetrafluoroethylene from step (2) to the mixture obtained in step (1) and stir to obtain a paste blend;

[0122] (4) At room temperature, the paste blend obtained in step (3) is ground three times using a three-roll mill to obtain perfluoropolyether grease.

[0123] Preparation Example 2

[0124] Preparation method of perfluoropolyether grease

[0125] (1) At a temperature of 50°C, take 80g of the perfluoropolyether-coated nano-calcium carbonate particles prepared in Example 2 and add them to 1000g of the linear perfluoropolyether base oil shown in Formula (V) (weight average molecular weight of 10500g / mol, p / q = 30, Rf1 is -CF3, Rf2 is -C2F5), and stir to mix and obtain a mixture.

[0126] (2) Place 220g of polytetrafluoroethylene in an oven at 110℃ and bake for 6 hours for drying pretreatment.

[0127] The average particle size of polytetrafluoroethylene is 4.1 μm, and the weight-average molecular weight is 3.5 × 10⁻⁶. 5 g / mol, specific surface area 13m² 2 / g, melting point is 330℃.

[0128] (3) Add the pretreated polytetrafluoroethylene from step (2) to the mixture obtained in step (1) and stir to obtain a paste blend;

[0129] (4) At room temperature, the paste blend obtained in step (3) is ground three times using a three-roll mill to obtain perfluoropolyether grease.

[0130] Preparation Example 3

[0131] Preparation method of perfluoropolyether grease

[0132] (1) At a temperature of 60°C, 100g of the perfluoropolyether-coated nano-calcium carbonate particles prepared in Example 3 were added to 1000g of the linear perfluoropolyether base oil of Formula (V) (weight average molecular weight of 10500g / mol, p / q = 30, Rf1 is -CF3, Rf2 is -C2F5), and stirred and mixed to obtain a mixture.

[0133] (2) Place 200g of polytetrafluoroethylene in an oven at 110℃ and bake for 4 hours for drying pretreatment.

[0134] The average particle size of polytetrafluoroethylene is 8.3 μm, and the weight-average molecular weight is 3.2 × 10⁻⁶. 4 g / mol, specific surface area 18m² 2 / g, melting point is 325℃.

[0135] (3) Add the pretreated polytetrafluoroethylene from step (2) to the mixture obtained in step (1) and stir to obtain a paste blend;

[0136] (4) At room temperature, the paste blend obtained in step (3) is ground three times using a three-roll mill to obtain perfluoropolyether grease.

[0137] Comparative Preparation Example 1

[0138] Comparative Preparation Example 1 was prepared according to the method described in Preparation Example 1, except that the perfluoropolyether-coated nano-calcium carbonate particles prepared in Example 1 were not added.

[0139] Comparative Preparation Example 2

[0140] Comparative Preparation Example 2 was prepared according to the method described in Preparation Example 1, except that conventional nano-calcium carbonate particles were used instead of the perfluoropolyether-coated nano-calcium carbonate particles prepared in this application.

[0141] Comparative preparation example 3

[0142] Comparative Preparation Example 3 was prepared according to the method described in Preparation Example 1, except that the 50g of perfluoropolyether-coated calcium carbonate nanoparticles prepared in Example 1 were replaced with the 50g of perfluoropolyether-coated calcium carbonate nanoparticles prepared in Comparative Example 1.

[0143] The performance test results of the perfluoropolyether greases prepared in Preparation Examples 1-3 and Comparative Preparation Examples 1-3 are shown in Table 1 and 2. Figure 2 As shown.

[0144] The oil content of the steel mesh was tested according to standard NB / SH / T 0324 (unit: %), under test conditions of 204℃ and 24h; the wear scar diameter (unit: mm) and friction coefficient were tested according to standard SH / T 0204, under test conditions of 1200rpm, 1h, 75℃ and 392N.

[0145] Meanwhile, the perfluoropolyether greases prepared in Preparation Examples 1-3 and Comparative Preparation Examples 1-3 were filled into bearings of the same model. The bearing temperatures were tested after 8h, 16h, 32h, 64h, 128h, 256h, and 512h of operation under axial load of 300N, radial load of 600N, and rotational speed of 3000rpm. The results are as follows: Figure 2 As shown.

[0146] Table 1. Oil separation performance and anti-wear properties of steel meshes from Preparation Examples 1-3 and Comparative Preparation Examples 1-3

[0147]

[0148]

[0149] From Table 1 above and Figure 2 Analysis of the test results shows that:

[0150] (1) In the perfluoropolyether greases prepared in Examples 1-3 of the present invention, the perfluoropolyether-coated nano-calcium carbonate particles have good compatibility with the perfluoropolyether base oil. When used as an anti-wear additive, it can effectively reduce the oil separation on the steel mesh, the wear scar diameter and the coefficient of friction of the perfluoropolyether grease, and can ensure that the lubricated bearing has a low bearing temperature rise over a long period of time. It is suitable for use in high-speed, heavy-load and other working conditions that require control of bearing temperature rise.

[0151] (2) In Comparative Preparation Example 1, compared with Preparation Example 1, the perfluoropolyether grease sample without any additives had a large oil separation in the steel mesh, poor anti-wear performance, and increased bearing temperature.

[0152] (3) In Comparative Preparation Example 2, compared with Preparation Example 1, nano-calcium carbonate particles were directly used as anti-wear additives; in Comparative Preparation Example 3, compared with Preparation Example 1, nano-calcium carbonate particles coated with non-epoxy resin dynamic cross-linked perfluoropolyether were used as anti-wear additives, which can reduce the grease's steel mesh oil separation, wear scar diameter, friction coefficient and bearing temperature rise, but the degree of reduction is limited.

[0153] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A perfluoropolyether-coated nano-calcium carbonate particle, characterized in that, The perfluoropolyether-coated nano-calcium carbonate particles include nano-calcium carbonate particles, an epoxy resin dynamic crosslinking layer coating the nano-calcium carbonate particles, and perfluoropolyether grafted onto the surface of the epoxy resin dynamic crosslinking layer. Based on 100 wt% of the perfluoropolyether-coated nano-calcium carbonate particles, the amount of the nano-calcium carbonate particles is 70-95 wt%; the amount of the epoxy resin dynamic crosslinking layer is 1-10 wt%; and the amount of the perfluoropolyether is 1-20 wt%.

2. The perfluoropolyether-coated nano-calcium carbonate particles according to claim 1, characterized in that, The epoxy resin dynamic cross-linked layer is formed by a cross-linking and curing reaction of raw materials including epoxy resin, acid anhydride compound, and triethanolamine.

3. The perfluoropolyether-coated nano-calcium carbonate particles according to claim 2, characterized in that, The molar ratio of the epoxy resin, the acid anhydride compound, and the triethanolamine is 1:(1-1.2):(0.05-0.15); And / or, the dynamic crosslinking layer contains one or more of the following: ester bonds, ether bonds, hydroxyl groups, carboxyl groups, and tertiary amine groups.

4. The perfluoropolyether-coated nano-calcium carbonate particles according to claim 2, characterized in that, The epoxy resin is selected from bisphenol A type epoxy resin, aliphatic epoxy resin or alicyclic epoxy resin. And / or, the anhydride compound is a monofunctional anhydride; preferably selected from methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, or dodecyl succinic anhydride.

5. The perfluoropolyether-coated nano-calcium carbonate particles according to any one of claims 1-4, characterized in that, The segmental structure of the perfluoropolyether is as follows: In formula (I), m and n are both integers, m≥1, n≥1; preferably, 10≤m≤40, 10≤n≤40.

6. The method for preparing perfluoropolyether-coated nano-calcium carbonate particles according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Provide carboxyl-terminated perfluoropolyether; (2) The nano-calcium carbonate particles are coated with an epoxy resin dynamic cross-linking layer to obtain the epoxy resin dynamic cross-linking layer coating the nano-calcium carbonate particles. (3) The carboxyl-terminated perfluoropolyether is grafted onto the surface of the epoxy resin dynamic crosslinking layer through transesterification and / or esterification to obtain perfluoropolyether-coated nano-calcium carbonate particles.

7. The preparation method according to claim 6, characterized in that, In step (1), the terminal acyl fluoride perfluoropolyether of formula (II) is hydrolyzed in concentrated sulfuric acid to obtain the terminal carboxyl perfluoropolyether of formula (III). In equations (II) and (III), m and n are both integers, m≥1, n≥1; preferably, 10≤m≤40, 10≤n≤40. And / or, in step (2), epoxy resin, acid anhydride compound, and triethanolamine are first mixed to obtain liquid mixture I; liquid mixture I is second mixed with nano-calcium carbonate particles to obtain semi-solid mixture II; semi-solid mixture II is ball-milled to obtain nano-calcium carbonate coated with epoxy resin dynamic crosslinking layer; And / or, in step (3), the carboxyl-terminated perfluoropolyether and the epoxy resin dynamic crosslinking layer-coated nano-calcium carbonate are mixed for the third time to obtain a semi-solid mixture III; the semi-solid mixture III is ball-milled to obtain perfluoropolyether-coated nano-calcium carbonate particles.

8. The preparation method according to claim 7, characterized in that, The weight-average molecular weight of the terminal acyl fluoride perfluoropolyether mentioned in step (1) is 2500 g / mol to 5000 g / mol; And / or, the hydrolysis conditions described in step (1) include: hydrolysis temperature of 15℃~40℃; hydrolysis time of 6h~12h; and stirring rate of 200~300rpm; And / or, the mass ratio of the terminal acyl fluoride perfluoropolyether to the concentrated sulfuric acid in step (1) is (100-120):1; And / or, in step (2), the conditions for the first mixing include: a temperature of 20°C to 25°C; And / or, the molar ratio of the epoxy resin to the acid anhydride compound is 1:(1 to 1.5); And / or, the molar ratio of the epoxy resin to the triethanolamine is 1:(0.05-0.2); And / or, in the second mixing in step (2), the mass ratio of the liquid mixture I to the nano-calcium carbonate particles is 1:(10-20); And / or, in step (2), the conditions for ball milling include: the volume ratio of the grinding balls to the semi-solid mixture II is (1.6 to 3): 1; the ball milling temperature is 150°C to 200°C; the stirring rate is 50 to 240 rpm; and the ball milling time is 3 to 5 h. And / or, in step (3), in the third mixture, the mass ratio of the nano-calcium carbonate coated by the epoxy resin dynamic crosslinking layer to the carboxyl-terminated perfluoropolyether is (99:1) to (80:20); And / or, in step (3), the conditions for ball milling include: the volume ratio of the grinding balls to the semi-solid mixture III is (1.6 to 3): 1; the ball milling temperature is 150°C to 200°C; the stirring rate is 50 to 240 rpm; and the ball milling time is 3 to 5 h.

9. The preparation method according to claim 8, characterized in that, The ball milling in step (2) includes: First, ball mill at a speed of 50-70 rpm for 50-90 minutes, then at a speed of 80-120 rpm for 50-90 minutes, then at a speed of 130-170 rpm for 50-90 minutes, and finally at a speed of 180-240 rpm for 20-40 minutes. And / or, the ball milling in step (3) includes: first ball milling at a speed of 50-70 rpm for 50-90 min, then ball milling at a speed of 80-120 rpm for 50-90 min, then ball milling at a speed of 130-170 rpm for 50-90 min, and finally ball milling at a speed of 180-240 rpm for 20-40 min.

10. A perfluoropolyether grease, characterized in that, The perfluoropolyether grease includes perfluoropolyether-coated calcium carbonate nanoparticles as described in any one of claims 1-4 or perfluoropolyether-coated calcium carbonate nanoparticles prepared by the preparation method described in any one of claims 5-7.

11. The perfluoropolyether grease according to claim 10, characterized in that, The perfluoropolyether grease comprises the following components by mass percentage: Perfluoropolyether base oil 50%–90%; Thickener 5%–40%; Perfluoropolyether-coated nano-calcium carbonate particles: 0.5%–15%; The perfluoropolyether base oil is selected from at least one of the perfluoropolyether base oils of formula (IV) or formula (V); In equations (IV) and (V), m, n, p, and q are all integers, m / n = 0.2 to 25, and p / q = 20 to 50; In equations (IV) and (V), Rf1 and Rf2 may be the same or different, and Rf1 and Rf2 are each independently selected from -CF3, -C2F5, -C3F7 or -CF(CF3)OCF3; And / or, the thickener has an average particle size of 0.1 μm to 20 μm, preferably 1 μm to 10 μm; and / or, the weight-average molecular weight is 1 × 10⁻⁶. 4 g / mol~1×10 6 g / mol; and / or, specific surface area of ​​2m² 2 / g~50m 2 / g, preferably 10m 2 / g~20m 2 / g; melting point is 320℃~340℃.

12. The perfluoropolyether grease according to claim 11, characterized in that, The weight-average molecular weight of the perfluoropolyether base oil is 2000 g / mol to 20000 g / mol; And / or, the thickener is polytetrafluoroethylene.

13. The method for preparing the perfluoropolyether grease according to any one of claims 10-12, characterized in that, The process involves mixing and grinding perfluoropolyether-coated nano-calcium carbonate particles, perfluoropolyether base oil, and a thickener to obtain the perfluoropolyether grease.

14. The method for preparing the perfluoropolyether grease according to claim 13, characterized in that, Before mixing the perfluoropolyether-coated nano-calcium carbonate particles, perfluoropolyether base oil, and thickener, the thickener is subjected to a drying pretreatment.

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