High-branching-degree perfluoropolyether siloxane for high-performance anti-fingerprint coating as well as preparation method and application of high-branching-degree perfluoropolyether siloxane

Abstract

The invention discloses high-branching-degree perfluoropolyether siloxane for a high-performance anti-fingerprint coating and a preparation method and application of the high-branching-degree perfluoropolyether siloxane, the structural general formula of the high-branching-degree perfluoropolyether siloxane is (SiO2) n-[O-Si (R1) (R2)-O-(CH2) m-NH-C (O)-PFPE] X, PFPE is a perfluoropolyether chain segment, and the number-average molecular weight is 1000-4000; r1 is selected from methyl or ethyl, and R2 is selected from methyl or C3-C10 alkyl containing an epoxy group; n is an integer of 2-6 and represents the polymerization degree of the siloxane core; m is an integer of 1-5; and x is an integer of 2-6 and represents functionality. According to the invention, a plurality of perfluoropolyether chains are bonded to the same siloxane oligomerization core, so that a three-dimensional network can be formed during curing, and the crosslinking density and wear resistance of the coating are remarkably improved.

Description

Technical Field

[0001] This invention relates to the fields of fine fluorochemicals and surface treatment technology, and in particular to a highly branched perfluoropolyether siloxane for high-performance anti-fingerprint coatings, its preparation method and application. Background Technology

[0002] With the widespread adoption of touchscreen devices, anti-fingerprint coatings (AF coatings) have become a standard feature of screens and casings. Perfluoropolyether siloxanes, due to their extremely low surface tension and excellent lubricity, are currently the mainstream active ingredient in anti-fingerprint agents. However, existing technologies mainly fall into two categories: one is to link siloxane anchoring groups to both ends or one end of a linear perfluoropolyether chain (e.g., CN113912834B); the other is to prepare fluorinated polysiloxanes through simple blending or sol-gel methods.

[0003] While linear structures offer good initial hydrophobicity and oleophobicity, in high-intensity steel wool abrasion tests (>10,000 cycles) or under high temperature and humidity conditions, the coating exhibits insufficient crosslinking density or uneven distribution of anchoring groups, leading to an increased coefficient of friction and severe contact angle attenuation. Furthermore, some existing technologies utilize long-chain perfluoroalkyl groups (such as C8 and above), but their bioaccumulation is restricted by environmental regulations.

[0004] Therefore, it is of great significance to develop a novel perfluoropolyether siloxane main agent that combines high crosslinking density, high wear resistance, and environmental friendliness. Summary of the Invention

[0005] To address the technical problems of poor adhesion and durability of existing perfluoropolyether siloxane anti-fingerprint coatings, the present invention aims to provide a highly branched perfluoropolyether siloxane for high-performance anti-fingerprint coatings and its preparation method. By bonding multiple perfluoropolyether chains to the same siloxane oligomer nucleus, a three-dimensional network can be formed during curing, significantly improving the crosslinking density and wear resistance of the anti-fingerprint coating.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] This invention provides a highly branched perfluoropolyether siloxane for use in high-performance anti-fingerprint coatings, with the general structural formula (SiO2). n —[O—Si(R1)(R2)—O—(CH2) m —NH—C(O)—PFPE] X In this context, PFPE is a perfluoropolyether segment with a number average molecular weight of 1000-4000; R1 is selected from methyl or ethyl, R2 is selected from methyl or C3-C10 alkyl containing epoxy groups; n is an integer from 2 to 6, representing the degree of polymerization of the siloxane core; m is an integer from 1 to 5; and x is an integer from 2 to 6, representing the functionality.

[0008] The present invention also provides a method for preparing the highly branched perfluoropolyether siloxane for high-performance anti-fingerprint coating, comprising the following steps:

[0009] S1. Preparation of star-shaped silicon core: Using polyhedral oligosilsesquioxane (POSS) or tetraethoxysilane as precursors, a star-shaped siloxane core containing multiple active hydroxyl groups (Si-OH) is prepared by hydrolysis and condensation under acidic conditions.

[0010] S2. Activation of perfluoropolyether: Under an inert atmosphere, perfluoropolyether (PFPE-COOH) with carboxyl-terminated groups is reacted with γ-aminopropyltrimethoxysilane coupling agent, wherein the molar ratio of carboxyl-terminated perfluoropolyether to γ-aminopropyltrimethoxysilane is 1:1.5~1:3.0, to prepare a perfluoropolyether intermediate with trimethoxysilane-terminated groups;

[0011] S3. Grafting reaction: The star-shaped siloxane core from step S1 and the perfluoropolyether intermediate with a trimethoxysilane end group from step S2 are subjected to an amidation reaction at 40–65°C in the presence of a catalyst and a dehydrating agent. Simultaneously, the trimethoxysilane undergoes hydrolysis and condensation to form Si-O-Si bonds. After purification, a pale yellow to colorless transparent viscous liquid is obtained, which is the highly branched perfluoropolyether siloxane.

[0012] Preferably, in step S1, the acidic condition is pH = 2-4.

[0013] Preferably, in step S1, the temperature of the hydrolysis-condensation reaction is 40-80℃ and the time is 2-8 h.

[0014] Preferably, in step S1, the molar ratio of the star-shaped siloxane core to the perfluoropolyether intermediate with a trimethoxysilane end group is 1:(n+0.5~n+2.0), where n is an integer from 2 to 6, representing the degree of polymerization of the siloxane core.

[0015] Preferably, in step S2, the catalyst for the reaction process is TiF4.

[0016] Preferably, in step S3, the catalyst is 4-dimethylaminopyridine; and the dehydrating agent is dicyclohexylcarbodiimide (DCC).

[0017] Preferably, when the precursor is a polyhedral oligosilsesquioxane (POSS), the chemical structural formula of the resulting highly branched perfluoropolyether siloxane is shown in formula (I). .

[0018] Preferably, when the precursor is tetraethoxysilane, the chemical structural formula of the resulting highly branched perfluoropolyether siloxane is shown in formula (II). .

[0019] The present invention also provides an anti-fingerprint material comprising the highly branched perfluoropolyether siloxane used for high-performance anti-fingerprint coatings.

[0020] The aforementioned anti-fingerprint materials can be applied to the surface treatment of glass, ceramics, plastics, metals, or sapphire substrates.

[0021] The above-described solution of the present invention has the following beneficial effects:

[0022] 1. Excellent abrasion resistance: Due to the high cross-linking density brought about by the star-shaped structure, the water contact angle of the cured coating can still be maintained above 105° after 10,000 steel wool abrasion tests, which is far superior to the linear structure control.

[0023] 2. Long-lasting adhesion: Multiple anchor groups form covalent bonds with the substrate, and there is no coating peeling after high and low temperature and high humidity tests (double 85 test).

[0024] 3. Low coefficient of friction: The coefficient of kinetic friction is less than 0.03, resulting in a smooth feel. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only schematic diagrams of some embodiments of the present invention. For those skilled in the art, other related drawings or technical solutions can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is the 1H NMR spectrum of the product obtained in Example 1 of the present invention.

[0027] Figure 2 The diagram shows the water droplet angle test process (left) and results (right) of the product obtained in Embodiment 2 of the present invention. Detailed Implementation

[0028] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0029] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0031] The present invention is further illustrated by the following embodiments, but is not limited to the embodiments.

[0032] The testing method is as follows:

[0033] Water contact angle (WCA): The OCA20 contact angle measuring instrument was used to test 5 points and the average value was taken.

[0034] Dynamic friction coefficient: friction coefficient testing machine, load 200g, speed 100MM / min.

[0035] Steel Wool Abrasion Resistance: #0000 steel wool, load 1kg, friction area 1x1cm, record the contact angle after friction.

[0036] Example 1

[0037] A method for preparing a highly branched perfluoropolyether siloxane includes the following steps:

[0038] S1. Preparation of star-shaped silicon core: 5.2 g of tetraethoxysilane and 30 ml of ethanol were added to a 250 ml three-necked flask equipped with a stirrer and a reflux condenser. 2 ml of deionized water and 0.1 ml of hydrochloric acid were added dropwise with stirring, and the mixture was heated to 60 °C and reacted for 4 h. The reaction solution was neutralized, filtered, and the solvent was removed by vacuum distillation to obtain a viscous star-shaped siloxane core (average degree of polymerization n≈4).

[0039] The number-average molecular weight Mn of the product obtained in step S1 was determined to be 1560 g / mol and the molecular weight distribution PDI was 2.1 by gel permeation chromatography (GPC, Waters 1515 system, mobile phase THF, polystyrene standard).

[0040] Using nuclear magnetic resonance silicon spectroscopy (NMR) 29 Its structure was analyzed by Si NMR (Bruker Avance 400 MHz, solvent CDCl3): a strong signal peak appeared at -98 ppm, which was assigned to Q. 3 The structure is [Si(OSi)3OH]; a weak signal peak appears at -108 ppm, which is assigned to Q. 4 Structure [Si(OSi)4]. Q 3 The peak integral accounts for about 65%, indicating that the product is mainly branched.

[0041] Based on the GPC molecular weight and NMR structural information, the average degree of polymerization of the siloxane core was calculated to be n≈4.

[0042] S2. Preparation of trimethoxysilane-modified perfluoropolyether: 50 g (0.025 mol) of dicarboxylic acid perfluoropolyether (Fluorolink® C10) with a molecular weight of 2000 was dissolved in 100 ml of hexafluoroxylene. 13.4 g (0.075 mol) of γ-aminopropyltrimethoxysilane and 0.2 g of titanium tetrafluoride (TiF4) were added. The mixture was reacted at 50 °C for 6 h under a nitrogen atmosphere to obtain the PFPE-Si(OMe)3 intermediate with the chemical formula —O—Si(R1)(R2)—O—(CH2). m —NH—C(O)—PFPE fragment (where R1=R2=CH3, m=3).

[0043] S3. Final Product Synthesis: 5 g of the siloxane core obtained in step S1 was dissolved in 20 ml of hexafluoroxylene. 45 g of the PFPE-Si(OMe)3 intermediate from step S2 was added, along with 1.0 g of dicyclohexylcarbodiimide (DCC) as a dehydrating agent and 0.2 g of 4-dimethylaminopyridine (DMAP) as a catalyst. The mixture was heated to 80 °C and reacted for 12 h. After the reaction was complete, the mixture was filtered, and the solvent was removed under reduced pressure to obtain a pale yellow, transparent, viscous liquid, which is the target product P1. Its 1H NMR spectrum is shown below. Figure 1 As shown, the chemical formula is Core-(SiO2)4-[O-Si(CH3)8-O-(CH2)3-NH-CO-PFPE2-CO-NH-(CH2)3-Si(OCH3)2-O]4.

[0044] Example 2

[0045] The molecular weight of the perfluoropolyether was adjusted to 3000, and the product was bifunctional. The remaining steps were the same as in Example 1, and product P2 was obtained.

[0046] Example 3

[0047] A method for preparing a highly branched perfluoropolyether siloxane includes the following steps:

[0048] S1. Preparation of star-shaped siloxane cores (POSS cores):

[0049] Add 8.7g of octavinyl POSS (C) to a 250ml three-necked flask equipped with a stirrer, reflux condenser, and thermometer. 40 H 72 O 12 Si8 (molecular weight ≈1168, approximately 7.45 mmol) and 50 ml of anhydrous toluene were added dropwise. Under nitrogen protection, a mixture of 1.5 ml of deionized water (0.083 mol), 0.15 ml of concentrated hydrochloric acid (pH ≈ 2.5), and 5 ml of tetrahydrofuran was slowly added dropwise. The mixture was heated to 70°C and stirred at this temperature for 8 hours.

[0050] During the reaction, some vinyl groups on the periphery of POSS undergo hydrolysis and condensation under acidic conditions to generate a star-shaped siloxane core containing multiple active silanol groups (Si-OH). After the reaction is complete, the pH is adjusted to neutral with saturated sodium bicarbonate solution, the organic phase is separated, dried over anhydrous sodium sulfate, filtered, and the solvent is removed by rotary evaporation at 60°C and -0.09 MPa to obtain a colorless, transparent, viscous liquid, which is the star-shaped POSS siloxane core.

[0051] Product characterization:

[0052] GPC: Number-average molecular weight Mn = 2,200 g / mol, molecular weight distribution PDI = 1.4 (narrower core distribution than that prepared by TEOS, due to the regular structure of POSS).

[0053] 29 Si NMR: Signal peaks appeared at -68 ppm and -58 ppm, attributed to the T³ structure [RSi(OSi)3] and the T² structure [RSi(OSi)2OH]. The T³ peak integral percentage was approximately 75%, indicating that the POSS cage structure remained intact while some active silanol groups were generated.

[0054] FT-IR: at 3400-3200 cm -1 A broad Si-OH peak appears, in the range of 1100-1020 cm⁻¹. -1 The characteristic absorption peak of Si-O-Si cage-like structure appears.

[0055] Degree of polymerization and functionality calculation:

[0056] POSS itself is an eight-sensory cage structure (eight vertices).

[0057] After acid hydrolysis, an average of about 4-5 vinyl groups are converted into silanol groups, which can be used as grafting sites.

[0058] Based on the GPC molecular weight (Mn=2,200, which is about 1,000 more than the 1,168 of the raw material POSS) and NMR data, it is estimated that the average functionality of the siloxane core of the POSS is x≈4-5 and the degree of polymerization is n≈8 (in terms of SiO2 units, since each POSS contains 8 silicon atoms).

[0059] S2. Preparation of trimethoxysilyl perfluoropolyether intermediates:

[0060] Dissolve 50 g of a dicarboxylated perfluoropolyether (Fluorolink® C10, 0.025 mol) with a molecular weight of 2000 in 100 ml of hexafluoroxylene, add 13.4 g of γ-aminopropyltrimethoxysilane (0.075 mol, PFPE-COOH:silane molar ratio = 1:3), add 0.2 g of titanium tetrafluoride (TiF4) as a catalyst, and react at 50°C for 6 hours under a nitrogen atmosphere to obtain a perfluoropolyether intermediate with a trimethoxysilane end group (—O—Si(CH3)2—O—(CH2)3—NH—C(O)—PFPE fragment).

[0061] S3. Final product synthesis:

[0062] The POSS siloxane core (5.0 g, approximately 2.27 mmol, functionality x≈4) obtained in step ① was dissolved in 25 ml of hexafluoroxylene, and the perfluoropolyether intermediate (40 g, approximately 18.2 mmol, molar ratio approximately 1:8, ensuring complete grafting) obtained in step ② was added. 1.0 g of dicyclohexylcarbodiimide (DCC) was added as a dehydrating agent and 0.2 g of 4-dimethylaminopyridine (DMAP) was added as a catalyst, and the mixture was heated to 80 °C and reacted for 6 hours.

[0063] After the reaction was completed, the mixture was cooled to room temperature and filtered to remove insoluble matter. The filtrate was then distilled under reduced pressure at 60°C and -0.095 MPa to remove the solvent and unreacted monomers, yielding a pale yellow, transparent, viscous liquid, which was the target product P3, with a yield of approximately 85% (based on POSS siloxane nuclei).

[0064] Product characterization:

[0065] FT-IR: 1720 cm -1 (Amide C=O), 1200-1140 cm -1 (CF), 1100-1020 cm -1 (Si-O-Si), simultaneously 3200-3400 cm -1 The Si-OH peak at the point was significantly weakened, indicating that the grafting reaction was complete.

[0066] 19 F NMR: Shows characteristic peaks of PFPE segments, consistent with the raw material PFPE.

[0067] GPC: Number-average molecular weight Mn = 11,500, Molecular weight distribution PDI = 1.5.

[0068] Thermogravimetric analysis (TGA): 5% thermogravimetric temperature Td5 = 385°C, which is higher than 360°C in Example 1, indicating that the thermal stability is further improved after the introduction of the POSS core.

[0069] Based on the characterization results, the chemical formula of the obtained product is (SiO2). n —[O—Si(CH3)2—O—(CH2)3—NH—C(O)—PFPE2] X Where n≈8 (POSS cage structure contains 8 silicon atoms), x≈4-5, and the molecular weight of PFPE chain is about 2000.

[0070] Comparative Example 1 (Commercially available linear products)

[0071] A commercially available linear perfluoropolyether siloxane anti-fingerprint agent, designated D1, was selected. This product has a single-end anchoring group structure.

[0072] Comparative Example 2 (Synthesized according to existing patents)

[0073] Following the method described in Example 1 of CN113912834B, a methoxysilane-terminated modified linear perfluoropolyether, denoted as D2, was synthesized.

[0074] Performance test data

[0075] Examples 1-2 and Comparative Examples 1-2 were prepared into 0.1 wt% hexafluoropropanol solutions, sprayed onto clean glass slides, and cured at 150°C for 30 minutes. The test performance is shown in Table 1.

[0076] Table 1

[0077]

[0078] Through Table 1 and Figure 2 The results show that the branched perfluoropolyether siloxanes prepared in Examples 1 and 2 of this invention exhibit significantly better wear resistance than existing linear products while maintaining a high initial contact angle. After 10,000 cycles of friction, the contact angles of Comparative Examples 1 and 2 have dropped below 100° (generally considered to have lost their anti-fingerprint effect), while the samples of this invention still maintain around 110°. This indicates that the star-shaped branched structure imparts higher mechanical durability to the coating. The reduction in the coefficient of kinetic friction also means a better smooth feel when fingers glide across the screen. Product P3, prepared in Example 3 using POSS as the core, exhibits superior thermal stability and wear resistance due to the higher rigidity and better regularity of the POSS cage structure. After 5,000 cycles of friction, the contact angle remains above 110°, showing the highest performance retention rate after high temperature and high humidity testing, making it suitable for applications with higher durability requirements (such as automotive displays, foldable devices, etc.).

[0079] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A highly branched perfluoropolyether siloxane for use in high-performance anti-fingerprint coatings, having the general structural formula (SiO2). n —[O—Si(R1)(R2)—O—(CH2) m —NH—C(O)—PFPE] X ,in, PFPE is a perfluoropolyether segment with a number average molecular weight of 1000-4000; R1 is selected from methyl or ethyl, R2 is selected from methyl or C3-C10 alkyl containing epoxy groups; n is an integer from 2 to 6, representing the degree of polymerization of the siloxane core; m is an integer from 1 to 5; x is an integer from 2 to 6, representing the functionality.

2. The method for preparing the highly branched perfluoropolyether siloxane for high-performance anti-fingerprint coating as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of star-shaped silicon core: Using polyhedral oligomeric silsesquioxane or tetraethoxysilane as precursors, a star-shaped siloxane core containing multiple active hydroxyl groups is prepared by hydrolysis and condensation under acidic conditions. S2. Activation of perfluoropolyether: Under an inert atmosphere, a perfluoropolyether with a carboxyl end group is reacted with a γ-aminopropyltrimethoxysilane coupling agent, wherein the molar ratio of the carboxyl end group perfluoropolyether to γ-aminopropyltrimethoxysilane is 1:1.5~1:3.0, to prepare a perfluoropolyether intermediate with a trimethoxysilane end group; S3. Grafting reaction: The star-shaped siloxane core from step S1 and the perfluoropolyether intermediate with a trimethoxysilane end group from step S2 are subjected to an amidation reaction at 40–65°C in the presence of a catalyst and a dehydrating agent. Simultaneously, the trimethoxysilane undergoes hydrolysis and condensation to form Si-O-Si bonds. After purification, a pale yellow to colorless transparent viscous liquid is obtained, which is the highly branched perfluoropolyether siloxane.

3. The preparation method according to claim 2, characterized in that, In step S1, the acidic condition is pH = 2-4.

4. The preparation method according to claim 2, characterized in that, In step S1, the hydrolysis-condensation reaction is carried out at a temperature of 40-80°C for 2-8 hours.

5. The preparation method according to claim 2, characterized in that, In step S1, the molar ratio of the star-shaped siloxane core to the perfluoropolyether intermediate with a trimethoxysilane end group is 1:(n+0.5~n+2.0), where n is an integer from 2 to 6, representing the degree of polymerization of the siloxane core.

6. The preparation method according to claim 2, characterized in that, In step S2, the catalyst for the reaction process is TiF4.

7. The preparation method according to claim 2, characterized in that, In step S3, the catalyst is 4-dimethylaminopyridine; the dehydrating agent is dicyclohexylcarbodiimide.

8. The preparation method according to claim 2, characterized in that, The amidation reaction is carried out at a temperature of 60-100℃ for a time of 8-24 h.

9. The preparation method according to claim 2, characterized in that, When the precursor is a polyhedral oligosilsesquioxane, the chemical structural formula of the resulting highly branched perfluoropolyether siloxane is shown in formula (Ⅰ). 。 10. The preparation method according to claim 2, characterized in that, When the precursor is tetraethoxysilane, the chemical structural formula of the resulting highly branched perfluoropolyether siloxane is shown in formula (II). 。 11. An anti-fingerprint material comprising a highly branched perfluoropolyether siloxane as described in claim 1 for a high-performance anti-fingerprint coating.

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