A composite coating and its application

Abstract

The present invention relates to a non-stick pan coating, and specifically relates to a composite coating and its application. The composite coating includes a surface layer and a bottom layer. The surface layer contains polytetrafluoroethylene, and the bottom layer contains a block copolymer. The block copolymer includes a polyethersulfone segment and a polyoxazoline segment. The composite coating of one embodiment of the present invention has good metal adhesion. When it is used in non-stick pan cookware, it can improve the durability of the cookware.

Description

Technical Field

[0001] The present invention relates to a composite coating, and particularly to a composite coating and its application. Background Art

[0002] The coating of a Teflon non-stick pan usually consists of three layers: polytetrafluoroethylene (PTFE) on the outer layer, polyamide-imide (PAI) in the middle, and polyethersulfone (PES) on the inner layer. Polyethersulfone is known for its excellent heat resistance and strong adhesion to the metal substrate, which enables it to tightly bond with the substrate of the cookware, providing long-lasting durability and ensuring that the coating is not easily peeled off. However, due to the poor compatibility between polyethersulfone and polytetrafluoroethylene, an intermediate PAI layer is required to achieve effective bonding between the two. This multi-layer structure increases the complexity of the manufacturing process and may cause peeling and discoloration of the coating during daily use, thereby affecting the service life and appearance of the cookware.

[0003] In addition, since polyethersulfone is hydrophobic, when it is used as the main component of the coating, organic solvents often need to be added as diluents, which not only increases the production cost but also causes environmental pollution. To enhance the compatibility between polyethersulfone and polytetrafluoroethylene, polyethersulfone needs to be processed into ultrafine powder, which not only increases the cost but also makes the production process more complex. Summary of the Invention

[0004] To overcome at least one defect of the above-mentioned prior art, in a first aspect, the present invention provides a composite coating, including a surface layer and a bottom layer. The surface layer contains polytetrafluoroethylene, and the bottom layer contains a block copolymer, and the block copolymer includes a polyethersulfone chain segment and a polyoxazoline chain segment.

[0005] In one embodiment, the weight-average molecular weight of the polyethersulfone chain segment is 40,000 - 100,000 g / mol; and / or,

[0006] In the block copolymer, the mass content of the polyoxazoline chain segment is 5 - 40%.

[0007] In one embodiment, the weight-average molecular weight of the polyethersulfone chain segment is 50,000 - 95,000 g / mol; and / or,

[0008] In the block copolymer, the mass content of the polyoxazoline chain segment is 15 - 40%.

[0009] In one embodiment, the polyoxazoline chain segment is a poly(2-ethyl-2-oxazoline) chain segment; and / or,

[0010] In the block copolymer, the mass content of the polyoxazoline chain segment is 28 - 40%; and / or,

[0011] The weight-average molecular weight of the polyethersulfone segment is 80,000 to 91,000 g / mol; and / or,

[0012] The polyethersulfone segment has the following structural units:

[0013] .

[0014] In one embodiment, the method for preparing the block copolymer comprises the following steps:

[0015] Prepare a polyethersulfone containing a -CH2X group on the terminal benzene ring, and then initiate the ring-opening polymerization reaction of the oxazoline monomer through the -CH2X group to obtain the block copolymer;

[0016] wherein, X is a halogen atom.

[0017] In one embodiment, the preparation process of the polyethersulfone containing a -CH2X group on the terminal benzene ring includes:

[0018] React the reaction mixture at 140 - 200 °C for 2 - 6 h, then react the reaction system at 160 - 230 °C for 2 - 48 h, and then add a capping agent to the system; wherein, the reaction mixture includes a first monomer, a second monomer and a salt-forming agent; and / or,

[0019] The process of the ring-opening polymerization reaction includes:

[0020] React the polyethersulfone containing a -CH2X group on the terminal benzene ring and the oxazoline monomer at 90 - 110 °C to obtain the block copolymer.

[0021] In one embodiment, X is a chlorine atom or a bromine atom; and / or,

[0022] The salt-forming agent includes one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, potassium carbonate, sodium carbonate, cesium carbonate, potassium bicarbonate, sodium bicarbonate; and / or,

[0023] The first monomer includes bisphenol S, and the second monomer includes one or more of dichlorodiphenyl sulfone, difluorodiphenyl sulfone; and / or,

[0024] The capping agent includes one or more of 4-chlorobenzyl chloride, 4-chlorobenzyl bromide, 4-fluorobenzyl bromide, 4-fluorobenzyl chloride, 2-fluoro-4-bromobenzyl bromide, 2-chloro-4-fluorobenzyl bromide.

[0025] In a second aspect, the present invention provides a cooking utensil including the above composite coating.

[0026] In a third aspect, the present invention provides a block copolymer including a polyethersulfone segment and a polyoxazoline segment.

[0027] In a fourth aspect, the present invention provides the use of the above block copolymer in the preparation of a Teflon composite coating or cookware.

[0028] The composite coating of the present invention has good metal adhesion. When it is used in non-stick cookware, it can improve the durability of the cookware. Detailed Description of the Invention

[0029] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments, all of which do not depart from the scope of the present invention, and the descriptions therein are for illustrative purposes in nature and not intended to limit the present invention.

[0030] An embodiment of the present invention provides a block copolymer comprising a polyethersulfone segment and a polyoxazoline segment.

[0031] In one embodiment, the block copolymer is a polyethersulfone- b -polyoxazoline diblock copolymer.

[0032] In one embodiment, the polyethersulfone segment contains a sulfone group (-SO2-) and an arylene group.

[0033] In one embodiment, the polyethersulfone has the following structural unit:

[0034] .

[0035] In one embodiment, the weight-average molecular weight of the polyethersulfone segment can be 40,000 to 100,000 g / mol, further can be 50,000 to 95,000 g / mol, and still further can be 80,000 to 91,000 g / mol, such as 60,000 g / mol, 70,000 g / mol, 75,000 g / mol, 85,000 g / mol, 88,000 g / mol, 89,000 g / mol, 90,000 g / mol.

[0036] In one embodiment, in the block copolymer of polyethersulfone and polyoxazoline, the mass content of the polyoxazoline segment can be 5 to 40%, further can be 15 to 40%, and still further can be 28 to 40%, such as 6%, 10.5%, 11%, 12%, 15%, 18%, 19%, 20%, 25%, 28%, 29%, 30%, 35%, 39%. Among them, the content or molecular weight of the polyoxazoline segment in the block copolymer can be adjusted by controlling the molar ratio of the oxazoline monomer to the polyethersulfone segment.

[0037] In one embodiment, the monomers for preparing the polyethersulfone segment include a first monomer and a second monomer. The first monomer includes bisphenol S, and the second monomer includes one or more of dichlorodiphenyl sulfone (such as 4,4'-dichlorodiphenyl sulfone) and difluorodiphenyl sulfone (such as 4,4'-difluorodiphenyl sulfone). Further, the polyethersulfone segment can be prepared by the nucleophilic substitution reaction of the monomers.

[0038] In one embodiment, the oxazoline monomer for preparing the polyoxazoline segment includes 2-ethyl-2-oxazoline.

[0039] In one embodiment, the preparation process of the block copolymer of polyethersulfone and polyoxazoline includes: first preparing a polyethersulfone with a -CH2X group on the terminal benzene ring, and then initiating the ring-opening polymerization reaction of the oxazoline monomer through the -CH2X group to obtain the block copolymer. The ring-opening polymerization reaction can be, for example, cationic ring-opening polymerization.

[0040] In one embodiment, X in the -CH2X group (benzyl halide) on the terminal benzene ring of the polyethersulfone is a halogen atom, such as chlorine or bromine.

[0041] One embodiment of the present invention provides a preparation method of the above block copolymer, including the following steps:

[0042] Prepare a polyethersulfone with a -CH2X group on the terminal benzene ring to obtain a polyethersulfone containing an initiating group;

[0043] Initiate the ring-opening polymerization reaction of the oxazoline monomer through the polyethersulfone containing an initiating group to obtain a polyethersulfone- b -polyoxazoline block copolymer;

[0044] wherein, X is a halogen atom (such as a chlorine atom or a bromine atom).

[0045] In one embodiment, the polyethersulfone is prepared by a nucleophilic substitution reaction, and at the same time, it is capped with a small molecule containing a specific group to obtain a polyethersulfone containing an initiating group. Further, the cationic ring-opening polymerization of the oxazoline monomer is initiated by the polyethersulfone to obtain a polyethersulfone- b -polyoxazoline amphiphilic block copolymer.

[0046] In one embodiment, the polyethersulfone can be prepared by the reaction of the first monomer and the second monomer. Further, the preparation process of the polyethersulfone with a -CH2X group on the terminal benzene ring (or the polyethersulfone containing an initiating group) includes:

[0047] React the reaction mixture at 140 - 200 °C (the first reaction temperature) for 2 - 6 h, then react the reaction system at 160 - 230 °C (the second reaction temperature) for 2 - 48 h, and then add a capping agent to the system; wherein, the reaction mixture includes the first monomer, the second monomer, and a salt-forming agent.

[0048] In one embodiment, the weight-average molecular weight of the polyethersulfone containing an initiating group is the same as that of the above polyethersulfone segment, and the molecular weight distribution of the polyethersulfone can be 1.70 to 1.75, such as 1.71, 1.72, 1.73, 1.74.

[0049] In one embodiment, the molar ratio of the first monomer to the second monomer can be 1:1.0 to 1:1.03; the amount of the salt-forming agent can be 1.05 to 1.3 times the amount of the first monomer, such as 1.1 times, 1.15 times, 1.2 times, 1.25 times.

[0050] In one embodiment, the reaction mixture for preparing the polyethersulfone containing an initiating group includes a first monomer, a second monomer, a salt-forming agent, and an organic solvent.

[0051] In one embodiment, the organic solvent used in the preparation process of the polyethersulfone containing an initiating group includes a first organic solvent.

[0052] In one embodiment, the organic solvent used in the preparation process of the polyethersulfone containing an initiating group includes a first organic solvent and a second organic solvent, and its preparation process may include the following steps:

[0053] Mix the first monomer, the second monomer, the salt-forming agent, the first organic solvent, and the second organic solvent to obtain a reaction mixture; and

[0054] Reflux the reaction mixture at 140 to 200 °C for 2 to 6 h, then distill out the second organic solvent, react the reaction system at 160 to 230 °C for 2 to 48 h, and then add a capping agent to the system.

[0055] In one embodiment, the first monomer, the second monomer, and the salt-forming agent can be immersed in the first organic solvent in sequence, and then the second organic solvent is added to the system under stirring.

[0056] In one embodiment, the amount of the first organic solvent is such that the solid content of the reaction system reaches 20 to 45 wt% (such as 25 wt%, 30 wt%, 35 wt%, 40 wt%), and the amount of the second solvent is 0 to 20 wt% of the amount of the first solvent (such as 1 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%).

[0057] In one embodiment, during the preparation process of the polyethersulfone or the polyethersulfone containing an initiating group, the first reaction temperature can be, for example, 145 °C, 150 °C, 155 °C, 160 °C, 170 °C, 180 °C, 190 °C, and the reaction time can be, for example, 3 h, 4 h, 5 h.

[0058] In one embodiment, during the preparation of polyethersulfone or polyethersulfone containing an initiating group, the second reaction temperature can be, for example, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, and the reaction time can be, for example, 3 h, 3.5 h, 4 h, 5 h, 6 h, 8 h, 10 h, 12 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h.

[0059] In one embodiment, during the preparation of polyethersulfone or polyethersulfone containing an initiating group, after the reaction at the first reaction temperature is completed, the second organic solvent in the reaction system can be distilled out by raising the temperature of the system.

[0060] In one embodiment, during the preparation of polyethersulfone or polyethersulfone containing an initiating group, after the reaction at the second reaction temperature is completed, a capping agent is added to the system, and then post-treatment is carried out. The post-treatment can include: pressure filtering the reaction solution, crushing, washing with water, and vacuum drying.

[0061] In one embodiment, the first monomer can be bisphenol S, the second monomer can be one or more of dichlorodiphenyl sulfone (such as 4,4'-dichlorodiphenyl sulfone), difluorodiphenyl sulfone (such as 4,4'-difluorodiphenyl sulfone), and the oxazoline monomer can be 2-ethyl-2-oxazoline.

[0062] In one embodiment, the salt-forming agent can include one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, potassium carbonate, sodium carbonate, cesium carbonate, potassium bicarbonate, and sodium bicarbonate. Further, the salt-forming agent can be potassium carbonate and / or sodium carbonate.

[0063] In one embodiment, the first organic solvent can include dimethyl sulfoxide, dimethyl sulfone, N , N -dimethylformamide, N , N -dimethylacetamide, N -N-methylpyrrolidone, sulfolane, or one or more thereof. Further, the first organic solvent can be N , N -dimethylacetamide, N -N-methylpyrrolidone, sulfolane, or one or more thereof.

[0064] In one embodiment, the second organic solvent can include one or more of toluene, xylene, o-xylene, and chlorobenzene.

[0065] In one embodiment, the capping agent can include one or more of 4-chlorobenzyl chloride, 4-chlorobenzyl bromide, 4-fluorobenzyl bromide, 4-fluorobenzyl chloride, 2-fluoro-4-bromobenzyl bromide, and 2-chloro-4-fluorobenzyl bromide.

[0066] In one embodiment, the process of the ring-opening polymerization reaction of the oxazoline monomer includes: reacting a polyether sulfone containing a -CH2X group on the terminal benzene ring and the oxazoline monomer at 90-110 °C to obtain a block copolymer.

[0067] In one embodiment, the temperature of the ring-opening polymerization reaction of the oxazoline monomer can be 92 °C, 95 °C, 98 °C, 100 °C, 102 °C, 105 °C, 108 °C; the time can be 0.5-6 h, such as 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h.

[0068] In one embodiment, under a nitrogen atmosphere, a polyether sulfone containing an initiating group is mixed with oxazoline, and the temperature is raised to 90-110 °C, and the above system is reacted under magnetic stirring to obtain a polyether sulfone- b -polyoxazoline block copolymer.

[0069] In one embodiment, the preparation reaction of the polyether sulfone segment and / or the ring-opening polymerization reaction of the oxazoline monomer can be carried out in a nitrogen atmosphere. The reaction vessel used can be baked and dried to remove water, and evacuated and filled with nitrogen multiple times.

[0070] One embodiment of the present invention provides a composite coating (or Teflon composite coating), including a surface layer and a bottom layer. The surface layer contains polytetrafluoroethylene, and the bottom layer contains the above-mentioned block copolymer.

[0071] In one embodiment, the composite coating is disposed on the surface of the cooking utensil through the bottom layer.

[0072] In one embodiment, the method for preparing the block copolymer film (or layer) includes the following steps:

[0073] Mix 15-35 parts by mass of polyether sulfone- b -polyoxazoline block copolymer, 35-55 parts by mass of water and 10-50 parts by mass of a third organic solvent to form a dispersion; dry the dispersion into a film at a temperature of 200-380 °C.

[0074] In one embodiment, the third organic solvent can be one or more of chloroform, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0075] In one embodiment, the thickness of the polyether sulfone- b -polyoxazoline block copolymer film can be 10-2000 μm, such as 50 μm, 100 μm, 200 μm, 250 μm, 300 μm, 350 μm, 500 μm, 1000 μm, 1200 μm, 1500 μm, 1800 μm.

[0076] In one embodiment, the polyether sulfone-b The yellowness index of the polyoxazoline block copolymer film is less than 10, and further can be 5-9, such as 5, 6, 7, 8, 9.

[0077] One embodiment of the present invention provides a cooking utensil, including the above-mentioned composite coating or the block copolymer of polyethersulfone and polyoxazoline (polyethersulfone- b -polyoxazoline block copolymer).

[0078] In one embodiment, the cooking utensil is an appliance for cooking (such as a non-stick pan), and the composite coating is disposed at least on the inner surface of the cooking utensil.

[0079] One embodiment of the present invention provides the application of the above-mentioned block copolymer of polyethersulfone and polyoxazoline (or the block copolymer film of polyethersulfone and polyoxazoline) in the preparation of a Teflon composite coating.

[0080] The block copolymer of polyethersulfone and polyoxazoline in one embodiment of the present invention is an amphiphilic copolymer containing a hydrophobic polyethersulfone chain segment and a hydrophilic polyoxazoline chain segment, which can be well dissolved in polar organic solvents or used to prepare waterborne coatings, and has good film-forming properties and biocompatibility.

[0081] The block copolymer of polyethersulfone and polyoxazoline in one embodiment of the present invention has the characteristics of good compatibility with polytetrafluoroethylene, low yellowness index, and excellent water dispersibility. When it is used in a Teflon coating, it can effectively improve the adhesion between the coating and the applied substrate (such as metal), and reduce the risk of coating peeling off.

[0082] The block copolymer film of polyethersulfone and polyoxazoline in one embodiment of the present invention has better metal adhesion and lower yellowness index compared with the polyethersulfone film.

[0083] The block copolymer film of polyethersulfone and polyoxazoline in one embodiment of the present invention has better hydrophilicity and adhesion, and lower yellowness compared with the polyethersulfone film.

[0084] In the composite coating of one embodiment of the present invention, the presence of the polyoxazoline chain segment improves the yellowing resistance of the coating, so that the coating can still maintain its original color after long-term use.

[0085] The composite coating of one embodiment of the present invention has good non-stick performance and metal adhesion, and can be used as a non-stick coating for cooking utensils.

[0086] The composite coating of one embodiment of the present invention has better metal adhesion and low yellowing coefficient at the same time, improving the durability and aesthetics of the coating or cooking utensil.

[0087] The preparation and application of a block copolymer of polyethersulfone and polyoxazoline according to an embodiment of the present invention will be further described below in conjunction with examples. Among them, the test methods involved in each example are as follows.

[0088] Test method

[0089] 1. Weight-average molecular weight and molecular weight distribution (PDI)

[0090] The molecular weight of polyethersulfone was determined by gel permeation chromatography (GPC). Dimethylformamide (DMF) containing 20 mmol of lithium bromide was used as the mobile phase, and polymethyl methacrylate (PMMA) was used as the standard sample. The chromatographic columns were Agilent MIXD C, MIXD D, and MIXD E in series, and the flow rate was 1.0 mL / min.

[0091] 2. Adhesion test with metal

[0092] The dispersion of polyethersulfone- b -poly(2-ethyl-2-oxazoline) was sprayed on the cleaned metal surface to form a coating, and the adhesion strength between the coating and the metal substrate was determined according to the cross-cut test method of ASTM D3359 standard.

[0093] 3. Yellowness test

[0094] The yellowness index was determined according to the method specified in ASTM E313.

[0095] Example 1

[0096] Preparation of polyethersulfone containing an initiating group

[0097] 51707 g of sulfolane was added to a 100 L reaction kettle. Then, 15016 g of bisphenol S (60 mol), 17230 g of dichlorodiphenyl sulfone (60 mol), and 9951 g of potassium carbonate (72 mol) were successively added to the sulfolane. Then, 10341 g of xylene was added to the reaction kettle under stirring, and the mixture was heated to 160 °C (the first reaction temperature) and refluxed for 5 h. When no water was produced, the temperature was raised to completely distill out the xylene in the reaction kettle. Subsequently, the reaction was carried out at 220 °C (the second reaction temperature) for 3 h, and then 4-chlorobenzyl chloride was added for capping. Finally, the reaction solution was pressure-filtered, crushed, washed with water, and vacuum-dried to obtain polyethersulfone containing an initiating group.

[0098] Polyethersulfone- b -poly(2-ethyl-2-oxazoline) block copolymer preparation

[0099] Under a nitrogen atmosphere, 100 g of the polyethersulfone containing an initiating group prepared above was added to a reaction flask, followed by the addition of 24 mL of 2-ethyl-2-oxazoline monomer. Subsequently, the temperature of the system was raised to 100 °C to initiate the bulk polymerization of oxazoline; after reacting for 2 h, the polymerization was terminated with 5 mL of an aqueous NaOH solution (0.2 mol / L). After vacuum drying to a constant weight, polyethersulfone- b -poly(2-ethyl-2-oxazoline) block copolymer (PES- b -PEOX) was obtained.

[0100] The polyethersulfone containing an initiating group prepared was tested according to the foregoing method, and its weight-average molecular weight was measured to be 90580 g / mol, and the molecular weight distribution was 1.71; it was calculated that the mass content of the poly(2-ethyl-2-oxazoline) chain segment in the polyethersulfone- b -poly(2-ethyl-2-oxazoline) was 19.3%.

[0101] Preparation of polyethersulfone- b -poly(2-ethyl-2-oxazoline) film

[0102] 25 parts by mass of the polyethersulfone- b -poly(2-ethyl-2-oxazoline) powder prepared above, 40 parts by mass of deionized water, and 35 parts by mass of N-methylpyrrolidone were mixed and stirred to form a uniform polyethersulfone- b -poly(2-ethyl-2-oxazoline) dispersion. The dispersion was dried into a film at a high temperature of 350 °C, and the thickness of the film was 300 μm.

[0103] According to the foregoing method, the polyethersulfone- b -poly(2-ethyl-2-oxazoline) dispersion was sprayed on the metal surface for adhesion testing. The results showed that the adhesion between the film and the metal reached the requirements of ASTM grade 5B. According to the foregoing method, the polyethersulfone- b -poly(2-ethyl-2-oxazoline) film was subjected to yellowness testing, and the yellowness index was 6, indicating that the film had good color stability and low yellowness.

[0104] Polytetrafluoroethylene was heated to a molten state, and the polyethersulfone- b -poly(2-ethyl-2-oxazoline) powder prepared above was added and stirred. The polyethersulfone powder could adhere to the surface of polytetrafluoroethylene without delamination, indicating good adhesion between polytetrafluoroethylene and polyethersulfone- b -poly(2-ethyl-2-oxazoline).

[0105] Example 2

[0106] In this example, polyethersulfone- b-Poly(2-ethyl-2-oxazoline) and its film, the difference is only that: in the preparation of polyethersulfone containing an initiating group, N-methylpyrrolidone is used instead of sulfolane; the second reaction temperature is 200 °C, the reaction time is 6 h; the amount of 2-ethyl-2-oxazoline used is 12 mL.

[0107] The polyethersulfone containing an initiating group prepared according to the foregoing method was tested, and its weight-average molecular weight was 90145 g / mol, and the molecular weight distribution was 1.70; it was calculated that the mass content of the poly(2-ethyl-2-oxazoline) segment in the polyethersulfone- b -Poly(2-ethyl-2-oxazoline) was 10.5%.

[0108] The adhesion test of polyethersulfone- b -Poly(2-ethyl-2-oxazoline) to metal was carried out by the same method as in Example 1, and the results showed that the requirements of ASTM grade 5B were met.

[0109] The yellowness test of the polyethersulfone- b -Poly(2-ethyl-2-oxazoline) film was carried out by the same method as in Example 1, and the yellowness index was 8, indicating that the film had good color stability and low yellowness.

[0110] The adhesion test of polyethersulfone- b -Poly(2-ethyl-2-oxazoline) to polytetrafluoroethylene was carried out by the same method as in Example 1. The polyethersulfone- b -Poly(2-ethyl-2-oxazoline) could adhere to the surface of polytetrafluoroethylene without delamination, indicating good adhesion between the two.

[0111] Example 3

[0112] In this example, polyethersulfone- b -Poly(2-ethyl-2-oxazoline) and its film were prepared with substantially the same raw materials and processes as in Example 1, the difference is only that: in the preparation of polyethersulfone containing an initiating group, toluene is used instead of xylene; the second reaction temperature is 230 °C, the reaction time is 2 h; the amount of 2-ethyl-2-oxazoline used is 40 mL.

[0113] The polyethersulfone containing an initiating group prepared according to the foregoing method was tested, and its weight-average molecular weight was 90890 g / mol, and the molecular weight distribution was 1.74; it was calculated that the mass content of the poly(2-ethyl-2-oxazoline) segment in the polyethersulfone- b -Poly(2-ethyl-2-oxazoline) was 28.5%.

[0114] The adhesion test of polyethersulfone- b- Adhesion test of poly(2-ethyl-2-oxazoline) to metal, and the results show that the requirements of ASTM grade 5B are met.

[0115] The same method as in Example 1 was used to conduct the yellowness test of polyethersulfone- b - poly(2-ethyl-2-oxazoline) film. The yellowness index is 5, indicating that the film has good color stability and low yellowness.

[0116] The same method as in Example 1 was used to conduct the adhesion test of polyethersulfone- b - poly(2-ethyl-2-oxazoline) to polytetrafluoroethylene. Polyethersulfone- b - poly(2-ethyl-2-oxazoline) can adhere to the surface of polytetrafluoroethylene without delamination, indicating good adhesion between the two.

[0117] Example 4

[0118] In this example, polyethersulfone- b - poly(2-ethyl-2-oxazoline) and its film were prepared using basically the same raw materials and process as in Example 1, except that: in the preparation of polyethersulfone containing an initiating group, sodium carbonate was used instead of potassium carbonate; the second reaction temperature was 210 °C, the reaction time was 5 h; and the amount of 2-ethyl-2-oxazoline was 65 mL.

[0119] The polyethersulfone containing an initiating group obtained was tested according to the foregoing method. Its weight-average molecular weight was 89950 g / mol, and the molecular weight distribution was 1.74; the mass content of the poly(2-ethyl-2-oxazoline) chain segment in polyethersulfone- b - poly(2-ethyl-2-oxazoline) was calculated to be 39.3%.

[0120] The same method as in Example 1 was used to conduct the adhesion test of polyethersulfone- b - poly(2-ethyl-2-oxazoline) to metal, and the results show that the requirements of ASTM grade 5B are met.

[0121] The same method as in Example 1 was used to conduct the yellowness test of polyethersulfone- b - poly(2-ethyl-2-oxazoline) film. The yellowness index is 5, indicating that the film has good color stability and low yellowness.

[0122] The same method as in Example 1 was used to conduct the adhesion test of polyethersulfone- b - poly(2-ethyl-2-oxazoline) to polytetrafluoroethylene. Polyethersulfone- b - poly(2-ethyl-2-oxazoline) can adhere to the surface of polytetrafluoroethylene without delamination, indicating good adhesion between the two.

[0123] Example 5

[0124] This example uses substantially the same raw materials and process as in Example 1 to prepare polyethersulfone- b -poly(2-ethyl-2-oxazoline) and its membrane, with the only difference being that in the preparation of polyethersulfone containing an initiating group, N,N -dimethylacetamide is used instead of sulfolane, the second reaction temperature is 160 °C, the reaction time is 48 h; the amount of 2-ethyl-2-oxazoline is 6 mL.

[0125] The polyethersulfone containing an initiating group prepared according to the foregoing method was tested, and its weight-average molecular weight was 90240 g / mol, and the molecular weight distribution was 1.73; it was calculated that the mass content of the poly(2-ethyl-2-oxazoline) chain segment in polyethersulfone- b -poly(2-ethyl-2-oxazoline) was 5.6%.

[0126] The adhesion test of polyethersulfone- b -poly(2-ethyl-2-oxazoline) to metal was carried out using the same method as in Example 1, and the results showed that the requirements of ASTM grade 5B were met.

[0127] The yellowness test of polyethersulfone- b -poly(2-ethyl-2-oxazoline) membrane was carried out using the same method as in Example 1, and the yellowness index was 9, indicating that the membrane had good color stability and low yellowness.

[0128] The adhesion test of polyethersulfone- b -poly(2-ethyl-2-oxazoline) to polytetrafluoroethylene was carried out using the same method as in Example 1. Polyethersulfone- b -poly(2-ethyl-2-oxazoline) could adhere to the surface of polytetrafluoroethylene without delamination, indicating good adhesion between the two.

[0129] Comparative Example 1

[0130] Preparation of polyethersulfone

[0131] This example uses substantially the same raw materials and process as in Example 1 to prepare polyethersulfone.

[0132] Preparation of polyethersulfone membrane

[0133] 25 parts by mass of the polyethersulfone powder prepared above, 40 parts by mass of water, and 35 parts by mass of N-methylpyrrolidone were mixed and stirred to form a polyethersulfone dispersion, and the dispersion was dried into a film at a high temperature of 350 °C, and the thickness of the film was 300 μm.

[0134] The adhesion test of the polyethersulfone dispersion was carried out according to the foregoing method, and the results showed that the requirements of ASTM grade 3B were met. The yellowness test of the polyethersulfone was carried out according to the foregoing method, and the yellowness index was 20.

[0135] The polytetrafluoroethylene was heated to a molten state, and polyethersulfone powder was added and stirred. The polyethersulfone powder could not adhere to the surface of the polytetrafluoroethylene, and the two showed stratification, indicating poor adhesion between the polytetrafluoroethylene and the polyethersulfone.

[0136] Table 1 lists the differences and performance parameters of the polymer membranes of each example and Comparative Example 1.

[0137] Table 1 Structural parameters and performance parameters of the polymer membranes of each example and Comparative Example 1

[0138]

[0139] According to the results of Example 1 and Comparative Example 1 in Table 1, compared with Comparative Example 1, in the examples of the present invention, by using a block copolymer of polyethersulfone and polyoxazoline as the bottom layer of the composite coating, the coating can have better adhesion and a low yellowness coefficient, improving the durability and aesthetics of the coating. Further, the main difference between Examples 1 to 5 lies in the different contents of the polyoxazoline chain segment in the block copolymer. According to the results of Table 1, the yellowness indices of Examples 1, 3, and 4 are lower than those of Examples 2 and 5. Thus, in the block copolymer of polyethersulfone and polyoxazoline, the mass content of the polyoxazoline chain segment is preferably 15-40%, more preferably 28-40%.

[0140] Unless otherwise specified, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0141] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the protection scope of the present invention. Those skilled in the art can make various other substitutions, changes, and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments but is only defined by the claims.

Claims

1. A composite coating, characterized in that, It includes a surface layer and a bottom layer. The surface layer contains polytetrafluoroethylene, and the bottom layer contains a block copolymer. The block copolymer includes a polyethersulfone segment and a polyoxazoline segment. In the block copolymer, the mass content of the polyoxazoline segment is 5-40%.

2. The composite coating according to claim 1, characterized in that, The weight-average molecular weight of the polyethersulfone segment is 40000-100000 g / mol.

3. The composite coating according to claim 1, characterized in that, The weight-average molecular weight of the polyethersulfone segment is 50000-95000 g / mol; and / or, In the block copolymer, the mass content of the polyoxazoline segment is 15-40%.

4. The composite coating according to claim 1, wherein The polyoxazoline segment is a poly(2-ethyl-2-oxazoline) segment; and / or, In the block copolymer, the mass content of the polyoxazoline segment is 28-40%; and / or, The weight-average molecular weight of the polyethersulfone segment is 80000-91000 g / mol; and / or, The polyethersulfone segment has the following structural units: 。 5. The composite coating according to claim 4, characterized in that, The preparation method of the block copolymer includes the following steps: Prepare a polyethersulfone containing a -CH2X group on the terminal benzene ring, and then initiate the ring-opening polymerization reaction of the oxazoline monomer through the -CH2X group to obtain the block copolymer; Wherein, X is a halogen atom.

6. The composite coating according to claim 5, wherein The preparation process of the polyethersulfone containing a -CH2X group on the terminal benzene ring includes: React the reaction mixture at 140-200 °C for 2-6 h, then react the reaction system at 160-230 °C for 2-48 h, and then add a capping agent to the system; wherein, the reaction mixture includes a first monomer, a second monomer, and a salt-forming agent; and / or, The process of the ring-opening polymerization reaction includes: React the polyethersulfone containing a -CH2X group on the terminal benzene ring and the oxazoline monomer at 90-110 °C to obtain the block copolymer.

7. The composite coating according to claim 6, characterized in that, X is a chlorine atom or a bromine atom; and / or, The salt-forming agent includes one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, potassium carbonate, sodium carbonate, cesium carbonate, potassium bicarbonate, and sodium bicarbonate; and / or, The first monomer includes bisphenol S, and the second monomer includes one or more of dichlorodiphenyl sulfone and difluorodiphenyl sulfone; and / or, The capping agent includes one or more of 4-chlorobenzyl chloride, 4-chlorobenzyl bromide, 4-fluorobenzyl bromide, 4-fluorobenzyl chloride, 2-fluoro-4-bromobenzyl bromide, and 2-chloro-4-fluorobenzyl bromide.

8. A cooking utensil, characterized in that, It includes the composite coating according to any one of claims 1 to 7.

9. Use of a block copolymer in the preparation of a Teflon composite coating, wherein, The block copolymer includes a polyethersulfone segment and a polyoxazoline segment. In the block copolymer, the mass content of the polyoxazoline segment is 5-40%.

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