CN119912847B - A composite coating and its application - Google Patents

Abstract

The invention relates to a non-stick pan coating, in particular to a composite coating and application thereof, the composite coating comprises a surface layer and a bottom layer, the skin layer comprises polytetrafluoroethylene and the bottom layer comprises a block copolymer comprising polyethersulfone segments and polyoxazoline segments. The composite coating of one embodiment of the invention has better metal adhesion, is used for non-stick cookware, and can improve the durability of the cookware.

Description

A composite coating and its application

Technical Field

The invention relates to a composite coating, in particular to a composite coating and application thereof.

Background Art

The coating of Teflon non-stick pans is usually composed of three layers: an outer layer of polytetrafluoroethylene (PTFE), a middle layer of polyamide-imide (PAI), and an inner layer of polyethersulfone (PES). Polyethersulfone is known for its excellent heat resistance and strong adhesion to metal substrates, which enables it to be closely bonded to the base material of the pan, providing long-lasting durability and ensuring that the coating is not easy to peel off. However, due to the poor compatibility between polyethersulfone and polytetrafluoroethylene, an intermediate layer of PAI is required to achieve an effective combination of 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, which in turn affects the service life and appearance of the pan.

In addition, due to its hydrophobicity, polyethersulfone, when used as the main component of coatings, often needs to add organic solvents as diluents, which not only increases production costs, but also causes environmental pollution. In order to enhance the compatibility of polyethersulfone with polytetrafluoroethylene, polyethersulfone needs to be processed into ultrafine powder, which not only increases costs, but also makes the production process more complicated.

Summary of the invention

To overcome at least one defect of the above-mentioned prior art, in a first aspect, the present invention provides a composite coating, comprising a surface layer and a bottom layer, wherein the surface layer comprises polytetrafluoroethylene, and the bottom layer comprises a block copolymer, wherein the block copolymer comprises a polyethersulfone segment and a polyoxazoline segment.

In one embodiment, the weight average molecular weight of the polyethersulfone segment is 40,000 to 100,000 g/mol; and/or,

In the block copolymer, the mass content of the polyoxazoline segment is 5 to 40%.

In one embodiment, the weight average molecular weight of the polyethersulfone segment is 50,000 to 95,000 g/mol; and/or,

In the block copolymer, the mass content of the polyoxazoline segment is 15 to 40%.

In one embodiment, 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 to 91000 g/mol; and/or,

The polyethersulfone segment has the following structural units:

.

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

preparing a polyethersulfone containing a -CH ₂ X group on the terminal benzene ring, and then initiating a ring-opening polymerization reaction of an oxazoline monomer through the -CH ₂ X group to obtain the block copolymer;

Here, X is a halogen atom.

In one embodiment, the preparation process of the polyethersulfone containing a -CH ₂ X group on the terminal benzene ring comprises:

The reaction mixture is reacted at 140-200° C. for 2-6 hours, and then the reaction system is reacted at 160-230° C. for 2-48 hours, and then a capping agent is added to the system; wherein the reaction mixture comprises a first monomer, a second monomer and a salt-forming agent; and/or,

The process of the ring-opening polymerization reaction comprises:

The polyethersulfone and oxazoline monomers containing a -CH ₂ X group on the terminal benzene ring are reacted at 90-110° C. to obtain the block copolymer.

In one embodiment, 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 end-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.

In a second aspect, the present invention provides a cooking utensil comprising the above-mentioned composite coating.

In a third aspect, the present invention provides a block copolymer comprising a polyethersulfone segment and a polyoxazoline segment.

In a fourth aspect, the present invention provides the use of the above-mentioned block copolymer in the preparation of Teflon composite coatings or cookware.

The composite coating of the invention has good metal adhesion and can be used in non-stick cookware to improve the durability of the cookware.

DETAILED DESCRIPTION

Typical embodiments that embody 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 changes in different embodiments without departing from the scope of the present invention, and the descriptions therein are essentially used as illustrations rather than to limit the present invention.

One embodiment of the present invention provides a block copolymer including a polyethersulfone segment and a polyoxazoline segment.

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

In one embodiment, the polyethersulfone segment comprises a sulfone group (—SO ₂ —) and an arylene group.

In one embodiment, the polyethersulfone has the following structural units:

.

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 further can be 80,000 to 91,000 g/mol, for example, 60,000 g/mol, 70,000 g/mol, 75,000 g/mol, 85,000 g/mol, 88,000 g/mol, 89,000 g/mol, and 90,000 g/mol.

In one embodiment, in the block copolymer of polyethersulfone and polyoxazoline, the mass content of the polyoxazoline segment can be 5-40%, further can be 15-40%, further can be 28-40%, for example 6%, 10.5%, 11%, 12%, 15%, 18%, 19%, 20%, 25%, 28%, 29%, 30%, 35%, 39%. Wherein, 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.

In one embodiment, the monomers for preparing the polyethersulfone chain 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 (e.g., 4,4'-dichlorodiphenyl sulfone) and difluorodiphenyl sulfone (e.g., 4,4'-difluorodiphenyl sulfone). Further, the polyethersulfone chain segment can be prepared by a nucleophilic substitution reaction of the monomers.

In one embodiment, the oxazoline monomer used to prepare the polyoxazoline segment includes 2-ethyl-2-oxazoline.

In one embodiment, the preparation process of the block copolymer of polyethersulfone and polyoxazoline includes: first preparing polyethersulfone containing _-CH2X group on the terminal benzene ring, and then initiating the ring-opening polymerization of oxazoline monomer by the _-CH2X group to prepare the block copolymer. The ring-opening polymerization reaction can be, for example, cationic ring-opening polymerization.

In one embodiment, X in the -CH ₂ X group (benzyl halide) on the terminal benzene ring of the polyethersulfone is a halogen atom, such as chlorine or bromine.

One embodiment of the present invention provides a method for preparing the above block copolymer, comprising the following steps:

preparing a polyethersulfone containing a -CH ₂ X group on a terminal benzene ring to obtain a polyethersulfone containing an initiating group;

The ring-opening polymerization reaction of oxazoline monomer is initiated by polyethersulfone containing an initiating group to obtain a polyethersulfone- b -polyoxazoline block copolymer;

Here, X is a halogen atom (eg, a chlorine atom or a bromine atom).

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

In one embodiment, the polyethersulfone can be prepared by reacting the first monomer and the second monomer. Further, the preparation process of the polyethersulfone containing a -CH ₂ X group on the terminal benzene ring (or the polyethersulfone containing an initiating group) includes:

The reaction mixture is reacted at 140-200° C. (first reaction temperature) for 2-6 hours, and then the reaction system is reacted at 160-230° C. (second reaction temperature) for 2-48 hours, and then a capping agent is added to the system; wherein the reaction mixture includes a first monomer, a second monomer and a salt-forming agent.

In one embodiment, the weight average molecular weight of the polyethersulfone containing the initiating group is the same as the molecular weight of the polyethersulfone segment, and the molecular weight distribution of the polyethersulfone may be 1.70 to 1.75, such as 1.71, 1.72, 1.73, and 1.74.

In one embodiment, the amount 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, for example, 1.1 times, 1.15 times, 1.2 times, or 1.25 times.

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.

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

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 the preparation process may include the following steps:

Mixing 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

The reaction mixture is refluxed at 140-200° C. for 2-6 hours, the second organic solvent is then evaporated, the reaction system is reacted at 160-230° C. for 2-48 hours, and then a capping agent is added to the system.

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

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

In one embodiment, during the preparation of polyethersulfone or 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, 3h, 4h, 5h.

In one embodiment, in the preparation process 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, 3h, 3.5h, 4h, 5h, 6h, 8h, 10h, 12h, 15h, 20h, 25h, 30h, 35h, 40h, 45h.

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 evaporated by increasing the system temperature.

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, followed by post-treatment. The post-treatment may include: filtering, crushing, washing, and vacuum drying the reaction fluid.

In one embodiment, the first monomer may be bisphenol S, the second monomer may be one or more of dichlorodiphenyl sulfone (eg, 4,4'-dichlorodiphenyl sulfone) and difluorodiphenyl sulfone (eg, 4,4'-difluorodiphenyl sulfone), and the oxazoline monomer may be 2-ethyl-2-oxazoline.

In one embodiment, the salt-forming agent may 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 may be potassium carbonate and/or sodium carbonate.

In one embodiment, the first organic solvent may include one or more of dimethyl sulfoxide, dimethyl sulfone, N , N -dimethylformamide, N , N -dimethylacetamide, N -methylpyrrolidone, and sulfolane. Further, the first organic solvent may be one or more of N , N -dimethylacetamide, N -methylpyrrolidone, and sulfolane.

In one embodiment, the second organic solvent may include one or more of toluene, xylene, o-xylene, and chlorobenzene.

In one embodiment, the capping agent may 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.

In one embodiment, the process of the ring-opening polymerization of the oxazoline monomer comprises: reacting a polyethersulfone having a -CH ₂ X group on the terminal benzene ring and an oxazoline monomer at 90-110° C. to obtain a block copolymer.

In one embodiment, the ring-opening polymerization reaction temperature 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 to 6 hours, for example 0.5h, 1h, 2h, 3h, 4h, 5h, 6h.

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

In one embodiment, the preparation reaction of the polyethersulfone chain segment and/or the ring-opening polymerization reaction of the oxazoline monomer can be carried out in a nitrogen atmosphere, and the reaction container used can be baked, dried and dehydrated, and vacuumed and filled with nitrogen multiple times.

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 comprises polytetrafluoroethylene, and the bottom layer comprises the above-mentioned block copolymer.

In one embodiment, the composite coating is disposed on the surface of the cookware through a primer layer.

In one embodiment, the method for preparing the block copolymer film (or layer) comprises the following steps:

15-35 parts by weight of polyethersulfone- b -polyoxazoline block copolymer, 35-55 parts by weight of water and 10-50 parts by weight of a third organic solvent are mixed to form a dispersion; the dispersion is dried at a temperature of 200-380°C to form a film.

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

In one embodiment, the thickness of the polyethersulfone- b -polyoxazoline block copolymer membrane can be 10 to 2000 μm, for example, 50 μm, 100 μm, 200 μm, 250 μm, 300 μm, 350 μm, 500 μm, 1000 μm, 1200 μm, 1500 μm, 1800 μm.

In one embodiment, the yellowness index of the polyethersulfone- b -polyoxazoline block copolymer film is less than 10, and may further be 5 to 9, such as 5, 6, 7, 8, or 9.

One embodiment of the present invention provides a cooker, comprising the above-mentioned composite coating or the above-mentioned block copolymer of polyethersulfone and polyoxazoline (polyethersulfone- b -polyoxazoline block copolymer).

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

One embodiment of the present invention provides the use of the above-mentioned block copolymer of polyethersulfone and polyoxazoline (or the block copolymer membrane of polyethersulfone and polyoxazoline) in the preparation of Teflon composite coating.

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

The block copolymer of polyethersulfone and polyoxazoline according to one embodiment of the present invention has the characteristics of good compatibility with polytetrafluoroethylene, low yellowness index and excellent water dispersibility. The use of the block copolymer in Teflon coating can effectively improve the adhesion between the coating and the applied substrate (such as metal) and reduce the risk of coating shedding.

The block copolymer membrane of polyethersulfone and polyoxazoline according to one embodiment of the present invention has better metal adhesion and lower yellowness index than the polyethersulfone membrane.

The block copolymer membrane of polyethersulfone and polyoxazoline according to one embodiment of the present invention has better hydrophilicity and adhesion, and lower yellowness than the polyethersulfone membrane.

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.

The composite coating according to one embodiment of the present invention has good non-stick properties and metal adhesion and can be used as a non-stick coating for cookware.

The composite coating of one embodiment of the present invention has better metal adhesion and low yellowness coefficient, thereby improving the durability and aesthetics of the coating or cookware.

Hereinafter, the preparation and application of the block copolymer of polyethersulfone and polyoxazoline according to one embodiment of the present invention will be further described in conjunction with examples. The test methods involved in each example are as follows.

Test Method

1. Weight average molecular weight and molecular weight distribution (PDI)

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

2. Adhesion test to metal

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 measured according to the cross-cut test method of ASTM D3359.

3. Yellowness test

Yellowness index The yellowness index was measured according to the method specified in ASTM E313.

Example 1

Preparation of polyethersulfone containing initiating groups

51707g of sulfolane was added into a 100L reactor, and then 15016g of bisphenol S (60mol), 17230g of dichlorodiphenyl sulfone (60mol), and 9951g of potassium carbonate (72mol) were added into the sulfolane in sequence, and then 10341g of xylene was added into the reactor under stirring, and the mixture was heated to 160°C (first reaction temperature) and refluxed for 5h. When no water was produced, the temperature was increased to completely evaporate the xylene in the reactor, and then the mixture was reacted at 220°C (second reaction temperature) for 3h, and then 4-chlorobenzyl chloride was added for end-capping. Finally, the reaction liquid was filtered, crushed, washed with water, and vacuum dried to obtain polyethersulfone containing initiating groups.

Preparation of polyethersulfone- b -poly(2-ethyl-2-oxazoline) block copolymer

Under a nitrogen atmosphere, 100 g of the polyethersulfone containing an initiating group prepared above was added to a reaction bottle, and then 24 mL of 2-ethyl-2-oxazoline monomer was added, and then the system was heated to 100° C. to initiate bulk polymerization of oxazoline; after reacting for 2 h, the polymerization was terminated with 5 mL of a NaOH aqueous solution (0.2 mol/L), and the mixture was vacuum dried to constant weight to obtain a polyethersulfone- b -poly(2-ethyl-2-oxazoline) block copolymer (PES- b -PEOX).

The obtained polyethersulfone containing initiating groups was tested according to the aforementioned method, and its weight average molecular weight was measured to be 90580 g/mol, and the molecular weight distribution was 1.71; the mass content of the poly(2-ethyl-2-oxazoline) segment in the polyethersulfone- b -poly(2-ethyl-2-oxazoline) was calculated to be 19.3%.

Preparation of polyethersulfone- b -poly(2-ethyl-2-oxazoline) membrane

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, and the dispersion was dried at a high temperature of 350°C to form a film with a thickness of 300 μm.

The polyethersulfone- b -poly(2-ethyl-2-oxazoline) dispersion was sprayed on the metal surface for adhesion test according to the above method, and the results showed that the adhesion between the film and the metal met the ASTM grade 5B requirements. The polyethersulfone- b -poly(2-ethyl-2-oxazoline) film was tested for yellowness according to the above method, and the yellowness index was 6, indicating that the film had good color stability and low yellowness.

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

Example 2

This embodiment uses basically the same raw materials and processes as those 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-methylpyrrolidone is used instead of cyclopentane sulfone; the second reaction temperature is 200°C, and the reaction time is 6h; and the amount of 2-ethyl-2-oxazoline used is 12mL.

The obtained polyethersulfone containing initiating groups was tested according to the aforementioned method, and its weight average molecular weight was 90145 g/mol, and the molecular weight distribution was 1.70; the mass content of the poly(2-ethyl-2-oxazoline) segment in the polyethersulfone- b -poly(2-ethyl-2-oxazoline) was calculated to be 10.5%.

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

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

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

Example 3

This embodiment uses basically the same raw materials and processes as Example 1 to prepare polyethersulfone- b -poly(2-ethyl-2-oxazoline) and its membrane, with the only difference being that toluene is used instead of xylene in the preparation of polyethersulfone containing an initiating group; the second reaction temperature is 230°C, and the reaction time is 2h; and the amount of 2-ethyl-2-oxazoline used is 40mL.

The polyethersulfone containing initiating groups prepared according to the aforementioned method was tested, and its weight average molecular weight was 90890 g/mol, and the molecular weight distribution was 1.74; the mass content of the poly(2-ethyl-2-oxazoline) segment in the polyethersulfone- b -poly(2-ethyl-2-oxazoline) was calculated to be 28.5%.

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

The yellowness test of the polyethersulfone- b -poly(2-ethyl-2-oxazoline) film was carried out in the same manner as in Example 1, and the yellowness index was 5, indicating that the film had good color stability and low yellowness.

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

Example 4

This embodiment uses basically the same raw materials and processes as Example 1 to prepare polyethersulfone- b -poly(2-ethyl-2-oxazoline) and its membrane, with the only difference being that sodium carbonate is used instead of potassium carbonate in the preparation of polyethersulfone containing an initiating group; the second reaction temperature is 210°C, and the reaction time is 5h; and the amount of 2-ethyl-2-oxazoline used is 65mL.

The polyethersulfone containing initiating groups prepared according to the aforementioned method was tested, and 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) segment in the polyethersulfone- b -poly(2-ethyl-2-oxazoline) was calculated to be 39.3%.

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

The yellowness test of the polyethersulfone- b -poly(2-ethyl-2-oxazoline) film was carried out in the same manner as in Example 1, and the yellowness index was 5, indicating that the film had good color stability and low yellowness.

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

Example 5

This embodiment uses basically the same raw materials and processes as those in Embodiment 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 cyclopentane sulfone, the second reaction temperature is 160°C, and the reaction time is 48h; and the amount of 2-ethyl-2-oxazoline used is 6mL.

The obtained polyethersulfone containing initiating groups was tested according to the aforementioned method, and its weight average molecular weight was 90240 g/mol, and the molecular weight distribution was 1.73; the mass content of the poly(2-ethyl-2-oxazoline) segment in the polyethersulfone- b -poly(2-ethyl-2-oxazoline) was calculated to be 5.6%.

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

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

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

Comparative Example 1

Preparation of polyethersulfone

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

Preparation of polyethersulfone membrane

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 at a high temperature of 350° C. to form a film with a thickness of 300 μm.

The polyethersulfone dispersion was subjected to an adhesion test according to the aforementioned method, and the results showed that it met the ASTM grade 3B requirements. The polyethersulfone was subjected to a yellowness test according to the aforementioned method, and the yellowness index was 20.

When polytetrafluoroethylene is heated to a molten state and polyethersulfone powder is added and stirred, the polyethersulfone powder cannot adhere to the surface of polytetrafluoroethylene and the two are separated into layers, indicating that the adhesion between polytetrafluoroethylene and polyethersulfone is poor.

Table 1 lists the differences and performance parameters of the polymer films of various embodiments and comparative example 1.

Table 1 Structural parameters and performance parameters of polymer films of various embodiments and comparative example 1

According to the result of Example 1 and Comparative Example 1 in Table 1, compared to Comparative Example 1, the embodiment of the present invention, by adopting the block copolymer of polyether sulfone and polyoxazoline as the bottom layer of composite coating, can make coating have better adhesion and low yellowness coefficient, improves the durability and aesthetics of coating. Further, the difference between Examples 1 to 5 is mainly that the content of polyoxazoline segment in the block copolymer is different. According to the result of Table 1, the yellowness index of Example 1,3,4 is lower than that of Example 2,5. Thus, in the block copolymer of polyether sulfone and polyoxazoline, the mass content of polyoxazoline segment is preferably 15～40%, more preferably 28～40%.

Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may 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 limited by the claims.

Claims (9)

1. The composite coating is characterized by comprising a surface layer and a bottom layer, wherein the surface layer comprises polytetrafluoroethylene, the bottom layer comprises a block copolymer, the block copolymer comprises a polyether sulfone chain segment and a polyoxazoline chain segment, and the mass content of the polyoxazoline chain segment in the block copolymer is 5-40%.

2. The composite coating of claim 1, wherein the polyethersulfone segment has a weight average molecular weight of 40000-100000 g/mol.

3. The composite coating according to claim 1, wherein the polyethersulfone segment has a weight average molecular weight of 50000-95000 g/mol and/or,

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

4. The composite coating of 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 chain segment is 28-40%, and/or,

The weight average molecular weight of the polyethersulfone chain segment is 80000-91000 g/mol, and/or,

The polyethersulfone segment has the following structural units:

。

5. the composite coating of claim 4, wherein the method of preparing the block copolymer comprises the steps of:

preparing polyether sulfone containing-CH ₂ X groups on a terminal benzene ring, and then initiating ring-opening polymerization reaction of oxazoline monomers through-CH ₂ X groups to prepare the block copolymer;

Wherein X is a halogen atom.

6. The composite coating according to claim 5, wherein the preparation of polyethersulfone comprising-CH ₂ X groups on the terminal benzene ring comprises:

Reacting the reaction mixture at 140-200 ℃ for 2-6 hours, then reacting the reaction system at 160-230 ℃ for 2-48 hours, and then adding a blocking agent into the system, wherein the reaction mixture comprises a first monomer, a second monomer and a salifying agent, and/or,

The process of the ring-opening polymerization reaction comprises the following steps:

And (3) reacting polyether sulfone and oxazoline monomers containing-CH ₂ X groups on the terminal benzene ring at the temperature of 90-110 ℃ to obtain the block copolymer.

7. The composite coating according to claim 6, wherein X is a chlorine atom or a bromine atom, and/or,

The salifying agent comprises 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 comprises bisphenol S, the second monomer comprises one or more of dichlorodiphenyl sulfone and difluorodiphenyl sulfone, and/or,

The end-capping agent comprises one or more of 4-chlorobenzyl chloride, 4-chlorobenzyl bromide, 4-fluorobenzyl chloride, 2-fluoro-4-bromobenzyl bromide and 2-chloro-4-fluorobenzyl bromide.

8. A cookware comprising a composite coating as claimed in any one of claims 1 to 7.

9. The application of a block copolymer in preparing a Teflon composite coating is disclosed, wherein the block copolymer comprises a polyether sulfone chain segment and a polyoxazoline chain segment, and the mass content of the polyoxazoline chain segment in the block copolymer is 5-40%.