Silane coupling agent modified polytetrafluoroethylene, preparation method and application thereof, and lubricating protective coating

Abstract

The invention relates to the field of lubrication, in particular to silane coupling agent modified polytetrafluoroethylene, a preparation method and application thereof and a lubrication protective coating. The present invention provides a silane coupling agent modified polytetrafluoroethylene preparation method, which comprises: mixing a polytetrafluoroethylene emulsion, a phosphoric acid solution and a silane coupling agent, and modifying to obtain the silane coupling agent modified polytetrafluoroethylene. The preparation method is convenient in process, the bonding strength of PTFE and matrix resin in the coating can be improved, meanwhile, the molecular structure of PTFE is not damaged, and the lubricating protection characteristic of PTFE in the coating is kept.

Description

Technical Field

[0001] The invention relates to the field of lubrication, and in particular to a silane coupling agent modified polytetrafluoroethylene, a preparation method and application thereof, and a lubrication protective coating. Background Art

[0002] Polytetrafluoroethylene (PTFE) is known for its excellent high temperature resistance, corrosion resistance, self-lubricating properties and non-stick properties, and is widely used in chemical, mechanical and electronic fields. However, due to the lack of polar groups in the molecular structure of PTFE, its surface free energy is low, and it is not easy to form a strong interface with other substances, resulting in poor interface bonding. In the field of coatings, conventional binders are difficult to form effective chemical bonds with PTFE, which affects the durability of the coating and greatly limits the application range of PTFE as a high-performance coating material. Summary of the invention

[0003] The present invention provides a silane coupling agent modified polytetrafluoroethylene and a preparation method and application thereof, and a lubricating protective coating. The preparation method can conveniently modify the PTFE surface, improve the bonding strength between the PTFE and the matrix resin in the coating, and at the same time, does not destroy the molecular structure of the PTFE, and maintains its lubricating protective properties in the coating.

[0004] The present invention provides a method for preparing polytetrafluoroethylene modified by a silane coupling agent, comprising the following steps:

[0005] The polytetrafluoroethylene emulsion, acid solution and silane coupling agent are mixed and modified to obtain the silane coupling agent modified polytetrafluoroethylene.

[0006] Preferably, the mass ratio of polytetrafluoroethylene to the silane coupling agent in the mixed solution obtained after the mixing is (15-25):(2-10).

[0007] Preferably, the pH value of the mixed solution obtained after the mixing is 2-3.

[0008] Preferably, the modification temperature is 50-90° C. and the modification time is 4-9 hours.

[0009] Preferably, after the modification is completed, it also includes filtration, washing and drying in sequence.

[0010] The present invention also provides silane coupling agent modified polytetrafluoroethylene prepared by the preparation method described in the above technical scheme.

[0011] The present invention also provides the use of the silane coupling agent modified polytetrafluoroethylene described in the above technical solution in a lubricating protective coating.

[0012] The present invention also provides a lubricating protective coating, which comprises, by weight, 40 to 60 parts of silane coupling agent-modified polytetrafluoroethylene, 40 to 60 parts of a binder, and 0 to 10 parts of a curing agent;

[0013] The silane coupling agent modified polytetrafluoroethylene is the silane coupling agent modified polytetrafluoroethylene described in the above technical solution.

[0014] Preferably, the adhesive includes one or more of epoxy resin, polyurethane resin and polyamide-imide resin.

[0015] Preferably, the curing agent includes one or more of diaminodiphenyl sulfone, diaminodiphenyl ether and diaminodiphenylmethane.

[0016] The present invention provides a method for preparing polytetrafluoroethylene modified with a silane coupling agent, comprising the following steps: mixing a polytetrafluoroethylene emulsion, an acid solution and a silane coupling agent, and performing modification to obtain the polytetrafluoroethylene modified with the silane coupling agent. The preparation method of the present invention does not require the use of large-scale equipment, and the modification can be achieved through a simple modification process, which significantly reduces the cost, and does not destroy the molecular structure of PTFE, thereby maintaining its lubricating and protective properties in the coating. During the modification process, the hydrolysis product of the silane coupling agent will be coated on the surface of PTFE, and the interface bonding between PTFE and the base binder will be enhanced through the surface organic functional groups, thereby improving the performance of the PTFE coating. The simple hydrolysis process does not destroy the molecular structure of PTFE, so that the lubricating and protective properties of the coating are not affected by the surface modification. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The SEM images of the polytetrafluoroethylene described in Example 1 and the polytetrafluoroethylene modified by the silane coupling agent;

[0018] Figure 2 The infrared spectra of the polytetrafluoroethylene described in Example 1 and the polytetrafluoroethylene modified by the silane coupling agent;

[0019] Figure 3 is the friction coefficient of the lubricating protective coating described in Example 1;

[0020] Figure 4 is the friction coefficient of the lubricating protective coating described in Example 2;

[0021] Figure 5 is the friction coefficient of the lubricating protective coating described in Example 3. DETAILED DESCRIPTION

[0022] The present invention provides a method for preparing polytetrafluoroethylene modified by a silane coupling agent, comprising the following steps:

[0023] The polytetrafluoroethylene emulsion, acid solution and silane coupling agent are mixed and modified to obtain the silane coupling agent modified polytetrafluoroethylene.

[0024] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0025] In the present invention, the concentration of the polytetrafluoroethylene emulsion is preferably 0.8-1.5 g / mL, more preferably 1 g / mL. In an embodiment of the present invention, the concentration of the polytetrafluoroethylene emulsion may be 1 g / mL. In the present invention, the method for preparing the polytetrafluoroethylene emulsion is preferably to mix polytetrafluoroethylene and a solvent and then perform high-speed shearing to obtain the polytetrafluoroethylene emulsion. In the present invention, the solvent is preferably one or more of ethanol, acetone and N,N-dimethylformamide. In the present invention, the rotation speed of the high-speed shearing is preferably 2000-4000 rpm, more preferably 2500 rpm-3500 rpm; the time of the high-speed shearing is preferably 10-50 min, more preferably 20-40 min. In an embodiment of the present invention, the solvent may be ethanol, the rotation speed of the high-speed shearing may be 3000 rpm, and the time may be 30 min.

[0026] In the present invention, the acid solution is preferably a phosphoric acid solution or a hydrochloric acid solution; the mass concentration of the phosphoric acid solution is preferably 1% to 2%, more preferably 1%. In an embodiment of the present invention, the mass concentration of the phosphoric acid solution may be 1%. In the present invention, the acid solution functions to catalyze the hydrolysis of the silane coupling agent.

[0027] In the present invention, the silane coupling agent is preferably one or more of KH550, KH560, KH570 and KH540. When the silane coupling agent is two or more of the above specific selections, the present invention has no special limitation on the ratio of the above specific substances, and they can be mixed in any ratio.

[0028] In the present invention, the mass ratio of polytetrafluoroethylene to silane coupling agent in the mixed solution obtained after mixing is preferably (15-25): (2-10), more preferably (18-22): (4-8). In an embodiment of the present invention, the mass ratio of polytetrafluoroethylene to silane coupling agent in the mixed solution can be 3:1 or 10:7.

[0029] In the present invention, the mixing process is preferably to place the polytetrafluoroethylene emulsion in a three-necked flask, add the solvent, add the phosphoric acid solution under the condition of a constant temperature oil bath, and dropwise add the silane coupling agent under stirring. In the present invention, the amount ratio of the polytetrafluoroethylene emulsion to the solvent is preferably 1g: (1-3)mL, more preferably 1g: 2.5mL. In an embodiment of the present invention, the amount ratio of the polytetrafluoroethylene emulsion to the solvent is 2g: 5mL.

[0030] In the present invention, the pH value of the mixed solution obtained after the mixing is preferably 2 to 3, more preferably 2.5 to 3, and most preferably 2.7. In an embodiment of the present invention, the pH value of the mixed solution may be 2.7.

[0031] In the present invention, the modification temperature is preferably 50-90°C, more preferably 60-80°C; the modification time is preferably 4-9h, more preferably 5-7h. In an embodiment of the present invention, the modification temperature can be 70°C and the modification time can be 6h.

[0032] After the modification is completed, the present invention further preferably includes sequentially performing suction filtration, washing and drying; the present invention has no special limitation on the suction filtration and drying process, and the processes well known to those skilled in the art can be used. In the present invention, the washing is preferably performed 3 times with ethanol.

[0033] The present invention also provides silane coupling agent modified polytetrafluoroethylene prepared by the preparation method described in the above technical scheme.

[0034] In the present invention, the silane coupling agent modified polytetrafluoroethylene comprises polytetrafluoroethylene and silicon dioxide and polysiloxane grafted on the surface of the polytetrafluoroethylene.

[0035] The present invention also provides the use of the silane coupling agent modified polytetrafluoroethylene described in the above technical solution in a lubricating protective coating.

[0036] The present invention also provides a lubricating protective coating, which comprises, by weight, 40 to 60 parts of silane coupling agent-modified polytetrafluoroethylene, 40 to 60 parts of a binder, and 0 to 10 parts of a curing agent;

[0037] The silane coupling agent modified polytetrafluoroethylene is the silane coupling agent modified polytetrafluoroethylene described in the above technical solution.

[0038] Calculated by weight, the lubricating protective coating of the present invention includes 40 to 60 parts of silane coupling agent-modified polytetrafluoroethylene, preferably 45 to 55 parts.

[0039] Based on the mass fraction of the silane coupling agent modified polytetrafluoroethylene, the lubricating protective coating of the present invention includes 40 to 60 parts of a binder, preferably 40 to 50 parts. In the present invention, the binder preferably includes one or more of epoxy resin, polyurethane resin and polyamide-imide resin. When the binder is two or more of the above-mentioned specific selections, the present invention has no special restrictions on the ratio of the above-mentioned specific substances, and they can be mixed in any ratio.

[0040] In the present invention, the lubricating protective coating also preferably includes 0 to 10 parts of a curing agent, preferably 0 to 8 parts. In the present invention, the curing agent preferably includes one or more of diaminodiphenyl sulfone, diaminodiphenyl ether and diaminodiphenyl methane. When the curing agent is two or more of the above specific selections, the present invention has no special restrictions on the ratio of the above specific substances, and they can be mixed in any ratio.

[0041] In the present invention, the method for preparing the lubricating protective coating preferably comprises the following steps:

[0042] The silane coupling agent modified polytetrafluoroethylene, a binder and a solvent are mixed to obtain a coating;

[0043] After the coating is sprayed on the surface of the substrate, it is dried and cured in sequence to obtain the lubricating protective coating.

[0044] The invention mixes the silane coupling agent modified polytetrafluoroethylene, a binder and a solvent to obtain a coating.

[0045] In the present invention, the mixing method is preferably shear dispersion; the rotation speed of the shear dispersion is preferably 2000-4000 rpm, more preferably 2500-3500 rpm; the time of the shear dispersion is preferably 10-60 min, more preferably 10-30 min. In an embodiment of the present invention, the rotation speed of the shear dispersion can be 2000 r / min, and the time can be 15 min. When the lubricating protective coating includes a curing agent, the mixing is preferably mixing silane coupling agent modified polytetrafluoroethylene, a binder, a curing agent and a solvent.

[0046] After obtaining the coating, the present invention sprays the coating on the surface of the substrate, and then sequentially dries and solidifies the coating to obtain the lubricating protective coating.

[0047] The present invention does not have any special limitation on the spraying process, and the process well known to those skilled in the art can be used. In an embodiment of the present invention, the spraying can be performed using a spray gun.

[0048] In the present invention, the substrate is preferably a substrate cleaned by sandblasting.

[0049] The present invention does not have any special limitation on the drying process, and the drying process may be carried out using a process well known to those skilled in the art.

[0050] The present invention has no special limitation on the curing temperature and time, and the curing temperature and time can be conventionally selected according to the type of adhesive. In an embodiment of the present invention, the curing temperature can be 100° C. or 150° C., and the curing time can be 2 hours.

[0051] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Example 1

[0053] 30 g of PTFE was added to 30 mL of ethanol, and the mixture was emulsified by high-speed shear stirring (stirring speed was 3000 rpm, time was 30 min) to obtain an emulsion;

[0054] After adding 50 mL of ethanol to 20 g of the emulsion, 5 g of a dilute phosphoric acid solution with a mass concentration of 1% was added under a constant temperature oil bath at 70° C., 10 g of KH550 was added dropwise under stirring (rotation speed of 100 rpm), and after modification at 70° C. for 6 h, the mixture was filtered and washed with ethanol for 3 times, and then dried to obtain polytetrafluoroethylene surface-modified with a silane coupling agent;

[0055] Disperse 10g of the polytetrafluoroethylene surface-modified with the silane coupling agent, 10g of epoxy resin E51 and 3g of curing agent diaminodiphenyl sulfone in 90g of solvent (including 45g of acetone and 45g of ethanol), and shear and disperse at 2000r / min for 10min to obtain a coating;

[0056] The coating is sprayed on the surface of the substrate after sandblasting cleaning by using a spray gun, and then dried at room temperature and cured (150° C., 2 h) to obtain a lubricating protective coating;

[0057] The polytetrafluoroethylene and the polytetrafluoroethylene modified by the silane coupling agent were subjected to SEM test, and the test results are as follows: Figure 1 As shown, the upper figure is the SEM image of polytetrafluoroethylene, and the lower figure is the SEM image of polytetrafluoroethylene modified by silane coupling agent. Figure 1 It can be seen that the polytetrafluoroethylene modified by silane coupling agent has Si element compared with polytetrafluoroethylene, and has coupling agent modified products;

[0058] The polytetrafluoroethylene and the polytetrafluoroethylene modified by the silane coupling agent were subjected to infrared spectrum test, and the test results were as follows: Figure 2 As shown, the upper figure is the infrared spectrum of polytetrafluoroethylene, and the lower figure is the infrared spectrum of polytetrafluoroethylene modified by silane coupling agent. Figure 2 It can be seen that after modification, 1040cm -1 The Si-O-Si characteristic peak at

[0059] The friction coefficient of the lubricating protective coating was tested using a CSM friction machine. The test results are as follows: Figure 3 As shown by Figure 3 It can be seen that the average friction coefficient of the lubricating protective coating is about 0.083, which is much lower than the friction coefficient of the metal substrate, and has excellent anti-friction and anti-wear protective effects);

[0060] The substrate sprayed with the coating was placed in a salt spray test chamber. After 7 days, no large-scale rust was observed on the surface, indicating good corrosion protection effect.

[0061] Example 2

[0062] 30 g of PTFE was added to 30 mL of ethanol, and the mixture was emulsified by high-speed shear stirring (stirring speed was 2800 rpm, time was 20 min) to obtain an emulsion;

[0063] After adding 50 mL of ethanol to 20 g of the emulsion, 5 g of a dilute phosphoric acid solution with a mass concentration of 1% was added under a constant temperature oil bath at 70° C., 10 g of KH560 was added dropwise under stirring (rotation speed of 100 rpm), and after modification at 70° C. for 6 h, the mixture was filtered and washed with ethanol for 3 times, and then dried to obtain polytetrafluoroethylene surface-modified with a silane coupling agent;

[0064] Dispersing 10 g of the polytetrafluoroethylene surface-modified with the silane coupling agent and 10 g of the polyamide-imide resin in 90 g of N,N-dimethylformamide solvent, and shearing and dispersing at 2000 r / min for 10 min to obtain a coating;

[0065] The coating was sprayed on the surface of the substrate after sandblasting by using a spray gun, dried at room temperature and then cured (150°C, 2h) to obtain a lubricating protective coating (the friction coefficient of the lubricating protective coating was tested using a CSM friction machine, and the test results are as follows: Figure 4 As shown by Figure 4 It can be seen that the average friction coefficient is about 0.081, which is much lower than the friction coefficient of the metal substrate, and has excellent anti-friction and anti-wear protective effects);

[0066] The substrate sprayed with the coating was placed in a salt spray test chamber. After 7 days, no large-scale rust was observed on the surface, indicating good corrosion protection effect.

[0067] Example 3

[0068] 10 g of PTFE was added to 10 mL of ethanol, and the mixture was emulsified by high-speed shear stirring (stirring rate was 3000 rpm, time was 20 min) to obtain an emulsion;

[0069] After adding 50 mL of ethanol to 25 g of the emulsion, 5 g of a 1% dilute phosphoric acid solution was added under a constant temperature oil bath at 70° C., and 7 g of KH560 was added dropwise under stirring (rotation speed of 130 rpm). After modification at 70° C. for 6 h, the mixture was filtered and washed with ethanol for 3 times, and then dried to obtain polytetrafluoroethylene surface-modified with a silane coupling agent;

[0070] Dispersing 10 g of the polytetrafluoroethylene surface-modified with the silane coupling agent and 10 g of the polyurethane resin in 90 g of N,N-dimethylformamide solvent, and shearing and dispersing at 2000 r / min for 10 min to obtain a coating;

[0071] The coating was sprayed on the surface of the substrate after sandblasting by using a spray gun, dried at room temperature and then cured (100°C, 2h) to obtain a lubricating protective coating (the friction coefficient of the lubricating protective coating was tested using a CSM friction machine, and the test results are as follows: Figure 5 As shown by Figure 5 It can be seen that the average friction coefficient is about 0.080, which is much lower than the friction coefficient of the metal substrate, and has excellent anti-friction and anti-wear protective effects);

[0072] The substrate sprayed with the coating was placed in a salt spray test chamber. After 7 days, no large-scale rust was observed on the surface, indicating good corrosion protection effect.

[0073] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing polytetrafluoroethylene modified with a silane coupling agent, characterized in that: The following steps are involved: The polytetrafluoroethylene emulsion, acid solution and silane coupling agent are mixed and modified to obtain the silane coupling agent modified polytetrafluoroethylene.

2. The preparation method according to claim 1, characterized in that The mass ratio of polytetrafluoroethylene to the silane coupling agent in the mixed solution obtained after the mixing is (15-25): (2-10).

3. The preparation method according to claim 1, characterized in that: The pH value of the mixed solution obtained after the mixing is 2-3.

4. The preparation method according to claim 1, characterized in that: The modification temperature is 50-90° C. and the modification time is 4-9 hours.

5. The preparation method according to claim 1, characterized in that: After the modification is completed, the process further includes sequentially performing filtration, washing and drying.

6. Silane coupling agent modified polytetrafluoroethylene prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the silane coupling agent modified polytetrafluoroethylene according to claim 6 in lubricating protective coatings.

8. A lubricating protective coating, characterized in that: Calculated by weight, it includes 40 to 60 parts of silane coupling agent modified polytetrafluoroethylene, 40 to 60 parts of binder and 0 to 10 parts of curing agent; The silane coupling agent modified polytetrafluoroethylene is the silane coupling agent modified polytetrafluoroethylene according to claim 6.

9. The lubricating protective coating according to claim 8, characterized in that: The adhesive includes one or more of epoxy resin, polyurethane resin and polyamide-imide resin.

10. The lubricating protective coating according to claim 8, characterized in that: The curing agent includes one or more of diaminodiphenyl sulfone, diaminodiphenyl ether and diaminodiphenylmethane.

Images