A polytetrafluoroethylene release coating and a method for making the same

Abstract

The application discloses a polytetrafluoroethylene anti-adhesion coating and a preparation method thereof, and belongs to the anti-adhesion coating field and is mainly applied to the surface of a hot roller. The polytetrafluoroethylene anti-adhesion coating is prepared from a polytetrafluoroethylene concentrated emulsion, a polyamide-imide, water, an FC-4430 surfactant, alcohol ester twelve, Al2O3, a defoaming agent and nano boron nitride. The polytetrafluoroethylene dispersion emulsion prepared by the application uses a perfluoropolyether carboxylic acid ammonium salt emulsifier, the prepared anti-adhesion coating product has good stability, superior anti-adhesion, and the critical cracking thickness and glossiness meet the processing performance requirements in the anti-adhesion coating field, and the product is environment-friendly and can be degraded.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of anti-sticking coating, and particularly relates to a polytetrafluoroethylene anti-sticking coating and a preparation method thereof. BACKGROUND

[0002] In the industrial production process, when the surface material is hot-bonded with the master batch, the master batch will undergo the process of high-temperature melting and cooling to the solidification point. In the molten state, the master batch may be adhered to the hot roller due to its high temperature and softening, and bonded together. This bonding may cause serious damage to the equipment, for example, the surface of the hot roller is attached with the master batch, causing the roller temperature to rise and affecting the heating effect; or causing scratches or wear and tear, affecting the normal operation of the equipment. In addition, if the master batch is bonded with the hot roller and cannot be separated quickly, it may also cause production line blockage and shutdown and other production interruption problems.

[0003] The emulsifiers used in traditional anti-sticking coatings are mainly perfluorooctanoic acid (PFOS), ammonium perfluorooctanoate (PFOA) and alkyl phenol polyoxyethylene ether (such as NPEO). Perfluorooctanoic acid and its salts (such as ammonium salt and sodium salt) are not only one of the most difficult-to-degrade organic pollutants in the world, but also have been proven to be harmful to the human body. NPEO is not easily biodegradable and has problems such as carcinogenicity, teratogenicity and mutagenicity. The waste liquid discharged in the production process also contains emulsifiers, causing difficulties in sewage treatment and environmental pollution. SUMMARY

[0004] This section aims to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0005] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0006] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art and provide a polytetrafluoroethylene anti-sticking coating.

[0007] To solve the above technical problems, the present application provides the following technical solutions. The coating comprises, in mass parts,

[0008] 40-50 parts of polytetrafluoroethylene concentrated emulsion, 10-20 parts of polyamide imide, 3-7 parts of water, 10-15 parts of FC-4430 surfactant, 3-7 parts of alcohol ester twelve, 10-20 parts of Al2O3, 0.1-0.5 parts of defoaming agent, 1-3 parts of nano boron nitride, wherein the ratio of polytetrafluoroethylene concentrated emulsion to polyamide imide is 6:1-3.

[0009] The polytetrafluoroethylene concentrated emulsion is concentrated by mixing 5-10 parts of polytetrafluoroethylene dispersion mother liquor, 2-10 parts of isomeric alcohol polyoxyethylene ether and 0.1-1 parts of carbonate, wherein the polytetrafluoroethylene dispersion mother liquor comprises, in mass parts,

[0010] 250-350 parts of deoxygenated deionized water, 0.3-0.5 parts of emulsifier, 0.03-0.05 parts of initiator, 1-5 parts of stabilizer, 10-15 parts of tetrafluoroethylene monomer.

[0011] As a preferred scheme of the polytetrafluoroethylene release coating according to the application, the emulsifier comprises one or more of ammonium perfluoropolyether carboxylate, perfluoropolyether carboxylic acid, sodium perfluoropolyether carboxylate.

[0012] As a preferred scheme of the polytetrafluoroethylene release coating according to the application, the amount of the emulsifier is 3-5% of the tetrafluoroethylene monomer.

[0013] As a preferred scheme of the polytetrafluoroethylene release coating according to the application, the initiator comprises one or more of ammonium persulfate, potassium persulfate, disuccinyl peroxide, diperoxy glutaric acid, tert-butyl hydroperoxide, and the stabilizer comprises one or more of paraffin and silicone oil.

[0014] As a preferred scheme of the polytetrafluoroethylene release coating according to the application, the amount of the initiator is 0.3-0.5% of the tetrafluoroethylene monomer, and the amount of the stabilizer is 10-15% of the tetrafluoroethylene monomer.

[0015] As a preferred scheme of the polytetrafluoroethylene release coating according to the application, the isomeric alcohol polyoxyethylene ether is isomeric tridecanol polyoxyethylene ether.

[0016] As a preferred scheme of the polytetrafluoroethylene release coating according to the application, the carbonate comprises one of ammonium carbonate or ammonium bicarbonate.

[0017] Another object of the application is to provide a preparation method of polytetrafluoroethylene release coating to overcome the deficiencies in the prior art.

[0018] To solve the above technical problems, the application provides the following technical scheme, comprising,

[0019] The polytetrafluoroethylene concentrated emulsion and the polyamide-imide are mixed and added to water and stirred uniformly, ultrasonic dispersion treatment is performed for 5-10 min, FC-4430 surfactant, alcohol ester twelve, Al2O3 and defoaming agent are sequentially added and stirred uniformly, and nano boron nitride is added and stirred for 2-3 h to obtain the polytetrafluoroethylene release coating.

[0020] As a preferred scheme of the preparation method of the polytetrafluoroethylene release coating, the preparation method of the polytetrafluoroethylene concentrated emulsion comprises,

[0021] The polytetrafluoroethylene dispersion mother liquor is heated to a temperature 5-15℃ lower than the cloud point of the isomeric alcohol polyoxyethylene ether, the isomeric alcohol polyoxyethylene ether is added, stirred uniformly, then the carbonate is added, stirred uniformly again, the temperature is raised to the cloud point of the isomeric alcohol polyoxyethylene ether, and then the supernatant is separated after constant temperature standing for 1-10h, thereby obtaining the polytetrafluoroethylene concentrated emulsion.

[0022] As a preferred scheme of the preparation method of the polytetrafluoroethylene release coating, the preparation method of the polytetrafluoroethylene dispersion mother liquor comprises,

[0023] The deoxygenated deionized water, the emulsifier, the initiator and the stabilizer are mixed, vacuumized to-0.03 to-0.1MPa, then the tetrafluoroethylene monomer is introduced, and the free radical polymerization reaction is carried out under continuous stirring at a rotation speed of 200-800rpm, thereby obtaining the polytetrafluoroethylene dispersion mother liquor, wherein the reaction temperature of the free radical polymerization reaction is 70-90℃, and the reaction pressure is 0.7-3.0MPa.

[0024] The present application has the following beneficial effects:

[0025] The emulsion is usually strictly required to have a critical cracking film thickness when used as a topcoat. The PTFE dispersion emulsion prepared by the present application uses the ammonium salt of perfluoropolyether carboxylic acid emulsifier, and the prepared release coating product has good stability, superior release property, and meets the processing performance requirements in the field of release coating, and is degradable and friendly to the environment. DETAILED DESCRIPTION

[0026] In order to make the above objectives, features and advantages of the present application more apparent and comprehensible, the specific embodiments of the present application will be described in detail below with reference to the embodiments of the present application.

[0027] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other manners different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0028] Secondly, the "one embodiment" or "embodiment" referred to herein means that a specific feature, structure or characteristic can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is independent or alternative to other embodiments.

[0029] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0030] The material obtained in this embodiment of the invention was subjected to critical cracking thickness testing using the following method:

[0031] The prepared coating was sprayed onto an aluminum foil plate and sintered. Under microscopic observation, the coating thickness was measured at points on the uncracked area of ​​the sintered aluminum foil plate using a TIME ultrasonic thickness gauge. The thickness was measured at a depth of 150 cm. 2 In the area, 1 per 5cm 2 Density points were selected, and the maximum value was chosen as the critical cracking thickness of the sintered plate.

[0032] Example 1

[0033] This embodiment provides a method for preparing a polytetrafluoroethylene (PTFE) anti-stick coating, specifically as follows:

[0034] 1) Add 300 parts of deoxygenated deionized water, 0.35 parts of perfluoropolyether ammonium carboxylate, 0.04 parts of bis(2-)-peroxysuccinic acid and ammonium persulfate aqueous solution, and 1 part of paraffin to the fluorination polymerization reactor. Control the temperature of the polymerization reactor at 85℃, evacuate to -0.05MPa, introduce 10 parts of TFE monomer and maintain the pressure at 1.8MPa, stir for 2.5h to carry out free radical polymerization reaction, and obtain PTFE dispersion mother liquor;

[0035] 2) Add 7 parts of PTFE dispersion mother liquor to a beaker, heat to 55°C in a water bath, add 4.2 parts of isomeric tridecyl alcohol polyoxyethylene ether, stir evenly, add 0.52 parts of ammonium bicarbonate, stir evenly, heat to 63°C, stop stirring, keep warm for 3 hours, separate into layers, cool, and remove the supernatant to obtain PTFE concentrated emulsion.

[0036] 3) Weigh 45 parts of PTFE concentrate, 15 parts of polyamide-imide (PAI), and 5 parts of water, stir evenly, and then ultrasonically disperse for 8 minutes. Add 15 parts of Al2O3, 5 parts of alcohol ester dodecyl, 0.1 parts of defoamer, and 12.9 parts of FC-4430 surfactant, stir evenly, then add 2 parts of nano boron nitride, stir for 2.5 hours, and mix evenly to obtain polytetrafluoroethylene anti-stick coating.

[0037] Example 2

[0038] The difference between this embodiment and Example 1 is that the mass of bis(2-)-peroxide succinic acid and ammonium persulfate aqueous solution in the raw materials in step 1) is adjusted to 0.03 parts, that is, the initiator is 0.3% of the TFE monomer. The rest of the preparation process is the same as in Example 1, and a polytetrafluoroethylene anti-stick coating is obtained.

[0039] Example 3

[0040] The difference between this embodiment and embodiment 1 is that the mass of the peroxide disuccinic acid and the aqueous ammonium persulfate solution in the raw material of step 1) is 0.05 parts, i.e. the initiator is 0.5% of the TFE monomer, and the rest of the preparation process is the same as that of embodiment 1, to obtain the polytetrafluoroethylene release coating.

[0041] The performance of the coating prepared in the above embodiment is tested, and the comparison results with embodiment 1 are shown in Table 1.

[0042] Table 1

[0043] Example 1 Example 2 Example 3 Critical cracking thickness / μm 25.5 20 21.3 Average coefficient of friction 0.2 0.39 0.31

[0044] As can be seen from Table 1, adjusting the initiator in the raw material has an effect on the performance of the polytetrafluoroethylene release coating, because the addition amount of the peroxide disuccinic acid and the aqueous ammonium persulfate solution will affect the polymerization rate and the quality of the PTFE dispersion mother liquor. When the addition amount is too much, the peroxide will decompose to generate too many free radicals, resulting in too fast polymerization rate, producing uneven polymerization products or producing poor physical properties. Excessive free radicals can also cause side reactions, such as acid etching, yellowing or reducing the molecular weight, etc.; and insufficient addition amount will result in insufficient generation of free radicals, and the polymerization rate will be reduced, thereby affecting the performance of the polytetrafluoroethylene release coating. According to the results in Table 1, the initiator content in the present application is 0.35% of the TFE monomer, which can obtain the best technical effect.

[0045] Example 4

[0046] The difference between this embodiment and embodiment 1 is that the perfluoropolyether carboxylic acid ammonium in the raw material of step 1) is 0.3 parts, i.e. the perfluoropolyether carboxylic acid ammonium is 3% of the TFE monomer, and the rest of the preparation process is the same as that of embodiment 1, to obtain the polytetrafluoroethylene release coating.

[0047] Example 5

[0048] The difference between this embodiment and embodiment 1 is that the perfluoropolyether carboxylic acid ammonium in the raw material of step 1) is 0.5 parts, i.e. the perfluoropolyether carboxylic acid ammonium is 5% of the TFE monomer, and the rest of the preparation process is the same as that of embodiment 1, to obtain the polytetrafluoroethylene release coating.

[0049] The performance of the coating prepared in the above embodiment is tested, and the comparison results with embodiment 1 are shown in Table 2.

[0050] Table 2

[0051] Example 1 Example 4 Example 5 Critical cracking thickness / μm 25.5 19.8 20.5 Average coefficient of friction 0.2 0.32 0.36

[0052] As shown in Table 2, adjusting the content of emulsifier in raw materials has an effect on the performance of polytetrafluoroethylene release coating, which is because the ammonium perfluoropolyether carboxylate forms a micellar structure in the water phase, so that the interaction force between water and tetrafluoroethylene monomer (TFE) is reduced, thereby promoting the stable formation of the emulsion. The TFE monomer is uniformly dispersed in the water phase, providing a uniform reaction environment for the polymerization reaction. Too high or too low content will affect the stability of the emulsion and further affect the effect of the polymerization reaction. According to the results in the above table, the ammonium perfluoropolyether carboxylate in the present application can obtain the best technical effect when the content of TFE monomer is 4%

[0053] Example 6

[0054] The difference between this example and Example 1 is that the ratio of PTFE concentrate to PAI in step 3) is adjusted to 6:1, i.e. 7.5 parts of PAI are weighed, and the rest of the preparation process is the same as Example 1, to prepare polytetrafluoroethylene release coating.

[0055] Example 7

[0056] The difference between this example and Example 1 is that the ratio of PTFE dispersion emulsion to PAI in step 3) is adjusted to 2:1, i.e. 22.5 parts of PAI are weighed, and the rest of the preparation process is the same as Example 1, to prepare polytetrafluoroethylene release coating.

[0057] The performance of the materials prepared in the above examples is tested, and the comparison results with Example 1 are shown in Table 3.

[0058] Table 3

[0059] Example 1 Example 4 Example 5 Critical cracking thickness / μm 25.5 19 20.5 Average coefficient of friction 0.2 0.37 0.33

[0060] As shown in Table 1, adjusting the ratio of PTFE dispersion emulsion to PAI has an effect on the performance of polytetrafluoroethylene release coating, which is because the PTFE particles in the PTFE dispersion are uniformly dispersed in the liquid phase. When the PTFE dispersion is mixed with PAI, PAI can interact with PTFE particles to form a PAI / PTFE composite system. This composite system can increase the mechanical strength, abrasion resistance and chemical resistance of the polytetrafluoroethylene release coating. At the same time, a protective polymer layer is formed on the surface of the coating, adjusting the viscosity and flowability of the coating. According to the results in the above table, the ratio of PTFE dispersion emulsion to PAI in the present application can obtain the best technical effect when the ratio is 3:1.

[0061] Comparative Example 1

[0062] This comparative example provides a polytetrafluoroethylene coating, and the specific formula is as follows:

[0063] PTFE emulsion 56 parts, PPS 13 parts, perfluorooctanoic acid 4 parts, silane coupling agent 4 parts, tetraethyl orthosilicate 3 parts, water 20 parts, mixed uniformly to prepare a polytetrafluoroethylene coating.

[0064] Comparative Example 2

[0065] The difference between this example and Example 1 is that the mass of the peroxide disuccinic acid and the aqueous ammonium persulfate in the raw materials in step 1) is 0.1 part, i.e., the initiator is 1% of the TFE monomer, and the rest of the preparation process is the same as Example 1, to prepare a polytetrafluoroethylene release coating.

[0066] Comparative Example 3

[0067] The difference between this example and Example 1 is that the perfluoropolyether carboxylic acid ammonium salt in the raw materials in step 1) is 1 part, i.e., the perfluoropolyether carboxylic acid ammonium salt is 10% of the TFE monomer, and the rest of the preparation process is the same as Example 1, to prepare a polytetrafluoroethylene release coating.

[0068] Comparative Example 4

[0069] The difference between this example and Example 1 is that the ratio of PTFE concentrate to PAI in step 3) is 1:1, i.e., 45 parts of PAI are weighed, and the rest of the preparation process is the same as Example 1, to prepare a polytetrafluoroethylene release coating.

[0070] The materials prepared in the above comparative examples are tested for performance, and the comparison results with Example 1 are shown in Table 4.

[0071] Table 4

[0072] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Critical cracking thickness / μm 25.5 10 12.8 13.5 13.3 Average coefficient of friction 0.2 0.53 0.65 0.63 0.69

[0073] As can be seen from the above table, the polytetrafluoroethylene release coating prepared by the present application has a significant performance improvement compared with traditional coatings; and the average friction coefficient of the release coating outside the scope of the present application is large, and the release effect is poor.

[0074] In summary, the polytetrafluoroethylene release coating prepared by the present application uses perfluoropolyether carboxylic acid ammonium salt emulsifier, and the release coating product prepared has good stability, superior release property, and critical cracking thickness and gloss that meet the processing performance requirements in the release coating field, is biodegradable and environmentally friendly. The PAI and PTFE particles interact to form a PAI / PTFE composite system. This composite system can increase the mechanical strength, wear resistance and chemical resistance of the polytetrafluoroethylene release coating. At the same time, a protective polymer layer is formed on the surface of the coating, which adjusts the viscosity and flowability of the coating.

[0075] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A polytetrafluoroethylene release coating, characterized by: The coating comprises, in mass parts, 40~50 parts of polytetrafluoroethylene concentrated emulsion, 10~20 parts of polyamide-imide, 3~7 parts of water, 10~15 parts of FC-4430 surfactant, 3~7 parts of alcohol ester twelve, 10~20 parts of Al2O3, 0.1~0.5 parts of defoaming agent, and 1~3 parts of nano boron nitride, wherein the ratio of the polytetrafluoroethylene concentrated emulsion to the polyamide-imide is 6:1~3; The polytetrafluoroethylene concentrated emulsion is obtained by mixing 5~10 parts of polytetrafluoroethylene dispersion mother liquor with 2~10 parts of isomeric alcohol polyoxyethylene ether and 0.1~1 parts of carbonate, wherein the polytetrafluoroethylene dispersion mother liquor comprises, in mass parts, 250~350 parts of deoxygenated deionized water, 0.3~0.5 parts of emulsifier, 0.03~0.05 parts of initiator, 1~5 parts of stabilizer, and 10~15 parts of tetrafluoroethylene monomer. The amount of the emulsifier is 3~5% of the tetrafluoroethylene monomer. The amount of the initiator is 0.3~0.5% of the tetrafluoroethylene monomer. The emulsifier comprises one or more of ammonium perfluoropolyether carboxylate, perfluoropolyether carboxylic acid, and sodium perfluoropolyether carboxylate. The amount of the stabilizer is 10~15% of the tetrafluoroethylene monomer.

2. The polytetrafluoroethylene release coating of claim 1, wherein: The initiator comprises one or more of ammonium persulfate, potassium persulfate, disuccinatyl peroxide, dipentanedioic acid peroxide, and tert-butyl hydroperoxide, and the stabilizer comprises one or more of paraffin and silicone oil.

3. The polytetrafluoroethylene release coating of claim 1, wherein: The isomeric alcohol polyoxyethylene ether is isomeric tridecanol polyoxyethylene ether.

4. The polytetrafluoroethylene release coating of claim 1 wherein: The carbonate comprises one of ammonium carbonate or ammonium bicarbonate.

5. The method for preparing the polytetrafluoroethylene anti-stick coating as described in any one of claims 1 to 4, characterized in that: Comprises, The polytetrafluoroethylene concentrated emulsion is mixed with the polyamide-imide and stirred in water until uniform, is subjected to ultrasonic dispersion treatment for 5~10 min, and then the FC-4430 surfactant, alcohol ester twelve, Al2O3, defoaming agent are added in sequence and stirred until uniform, and then the nano boron nitride is added and stirred for 2~3 h to obtain the polytetrafluoroethylene release coating.

6. The method of claim 5, wherein the polytetrafluoroethylene release coating is prepared by: The preparation method of the polytetrafluoroethylene concentrated emulsion comprises, The polytetrafluoroethylene dispersion mother liquor is heated to a temperature that is 5~15℃ lower than the turbidity point of the isomeric alcohol polyoxyethylene ether, the isomeric alcohol polyoxyethylene ether is added, and then the carbonate is added after stirring until uniform, and then the temperature is raised to the turbidity point of the isomeric alcohol polyoxyethylene ether, and the mixture is kept at constant temperature for 1~10 h, and then the supernatant is separated to obtain the polytetrafluoroethylene concentrated emulsion.

7. The method of claim 6, wherein the polytetrafluoroethylene release coating is prepared by: The preparation method of the polytetrafluoroethylene dispersion mother liquor comprises, The deoxygenated deionized water, emulsifier, initiator, and stabilizer are mixed, vacuumized to -0.03~-0.1 MPa, and then the tetrafluoroethylene monomer is introduced, and the free radical polymerization reaction is carried out under continuous stirring at a rotation speed of 200~800 rpm to obtain the polytetrafluoroethylene dispersion mother liquor, wherein the reaction temperature of the free radical polymerization reaction is 70~90℃, and the reaction pressure is 0.7~3.0 MPa.