CN108728784B

CN108728784B - Non-stick coating, preparation method thereof, cooker and cooking equipment

Info

Publication number: CN108728784B
Application number: CN201710278205.XA
Authority: CN
Inventors: 李兴航; 曹达华; 李康; 杨玲; 李洪伟; 屈雪平
Original assignee: Foshan Shunde Midea Electrical Heating Appliances Manufacturing Co Ltd
Current assignee: Foshan Shunde Midea Electrical Heating Appliances Manufacturing Co Ltd
Priority date: 2017-04-25
Filing date: 2017-04-25
Publication date: 2024-01-12
Anticipated expiration: 2037-04-25
Also published as: CN108728784A

Abstract

The invention relates to the technical field of electric heating appliances, and discloses a non-stick coating, a preparation method thereof, a cooker and cooking equipment. The method comprises the following steps: (1) pretreating a substrate; (2) Preheating the surface of the substrate obtained in the step (1); (3) Mixing ceramic powder and modified PFA powder to obtain a powder mixture, and performing plasma spraying treatment on the powder mixture to form a non-stick coating on the surface of a substrate; wherein 80% or more of the modified PFA powder has a sphericity of not less than 70%. The non-stick coating has the advantages of high surface hardness, high coating binding force, good scratch resistance, good corrosion resistance, good wettability, long service life and the like.

Description

Non-stick coating, preparation method thereof, cooker and cooking equipment

Technical Field

The invention relates to the technical field of electric heating appliances, in particular to a non-stick coating, a preparation method thereof, a cooker and cooking equipment.

Background

The conventional forming mode of the existing non-stick coating is mainly to adopt an air pressure spraying and electrostatic spraying mode and then sintering and solidifying at high temperature, the service life of the coating is generally only half a year to one year, the hardness of the coating is low (the Vickers hardness of the PTFE non-stick coating is 100-200HV, the Vickers hardness of the ceramic non-stick coating is 200-350 HV), the adhesive force of the coating is small (the bonding force of the PTFE non-stick coating is 2-10MPa, the bonding force of the ceramic non-stick coating is 2-5 MPa), the thickness of the coating is small (the thickness of the PTFE non-stick coating is 20-50 mu m, the thickness of the ceramic non-stick coating is 20-40 mu m), the acid-alkali resistance and the salt resistance are also generally, the coating can not be scraped, worn and corroded in the long-term use process, the coating can not fall off and fail, and the non-stick coating is not provided after the surface coating fails, so that the service life and application of the coating are limited to a great extent.

The existing cooking appliances, including frying pans, electric cookers, pressure cooker liners and the like, have widely used non-stick coatings, so that the coatings which are durable and non-stick and have excellent performance become key problems in the cooker industry.

Disclosure of Invention

The invention aims to overcome the problems in the prior art and provide a non-stick coating, a preparation method thereof, a pot and cooking equipment.

The inventor of the present invention creatively found in the research that the existing PFA powder, the particle size D50 of which is 5-30 μm, the sphericity of 90% or more is 10-30%, the flowability of which is 30-100s/50g, the purity of which is 90% -95%, the melting point of which is 300-400 ℃, the surface roughness Ra of which is 0.5-0.8 μm, is difficult to satisfy the manufacturing requirements of the thermal spraying (such as plasma spraying) process, and the coating has high surface hardness, high binding force of the coating, good scratch resistance, good corrosion resistance, good wettability, and long service life, and the PFA powder, which is not less than 80% of the sphericity of the powder after special treatment (according to a preferred embodiment, the particle size D50 of the modified powder is 20-100 μm, the sphericity of which is low, and the particle size distribution is relatively non-uniform, is difficult to satisfy the manufacturing requirements of the thermal spraying (such as plasma spraying), can not satisfy the requirements of the thermal spraying (such as plasma spraying) process, and the PFA powder, which has the coating has good scratch resistance, good wettability of which is not less than 70%, good adhesion resistance, good durability, and the coating of which is not good in use of the PFA material, can obtain the coating, and the coating has the good adhesion resistance of which has the performance of the thermal spraying (such as 50).

Accordingly, in order to achieve the above object, the present invention provides, in one aspect, a method of preparing a non-stick coating, the method comprising:

(1) Pretreating a matrix;

(2) Preheating the surface of the substrate obtained in the step (1);

(3) Mixing ceramic powder and modified PFA powder to obtain a powder mixture, and performing plasma spraying treatment on the powder mixture to form a non-stick coating on the surface of a substrate;

wherein 80% or more of the modified PFA powder has a sphericity of not less than 70%.

The second aspect of the invention provides a non-stick coating prepared by the method of the invention.

In a third aspect, the present invention provides a cookware comprising a substrate and a non-stick coating formed on the substrate, the non-stick coating comprising a mixed layer of ceramic and PFA; preferably, the non-stick coating is a non-stick coating according to the present invention.

According to a fourth aspect of the present invention, there is provided a cooking apparatus comprising a pan according to the present invention.

The non-stick coating is formed by uniformly mixing ceramic powder (preferably aluminum oxide powder and/or titanium oxide powder) with modified PFA powder with specific parameters, then adopting a plasma spraying process, depositing the mixture on a substrate at a high speed and in a molten state, melting the mixture at a high temperature and rapidly cooling the mixture, enabling the ceramic powder and the modified PFA powder to form a spherical molten state, then colliding the spherical molten state on the substrate at a high speed, flattening the spherical molten state, and uniformly mixing and stacking innumerable ceramic particles and modified PFA particles. The non-stick coating of the present invention has high hardness, high bonding strength, high scratch resistance, high corrosion resistance and good non-stick properties.

The structural schematic diagram of the arrangement mode of the particles forming the non-stick coating is shown in fig. 4, ceramic particles and modified PFA particles are distributed in a staggered manner, and the uniform distribution of the non-stick property, scratch resistance, corrosion resistance, wettability and other properties of the surface of the coating and the interior of the coating is ensured, namely, the coating has good hydrophobicity, good scratch resistance, good corrosion resistance and high coating adhesive force. In addition, compared with the conventional preparation method, the preparation mode of the coating has the advantages of short period, high efficiency, energy conservation and the like: the coating can be finished by spraying only once, and the thickness can reach 0.4mm at maximum, namely, the solidification forming is finished by depositing on a substrate; and by adopting an electrostatic spraying or air pressure spraying mode, spraying is required to be carried out firstly, then high-temperature sintering is carried out, and if the thickness of the prepared coating is too thick, the spraying and sintering processes are required to be repeated.

Specifically, in the method for producing a non-stick coating by plasma spraying technique of the present invention, a specific modified PFA powder is used, wherein, according to a preferred embodiment, the particle diameter D50 of the modified PFA powder is 20 to 100 μm (more preferably 40 to 100 μm, still more preferably 45 to 60 μm), the sphericity of 80% or more (preferably 90% or more) of the modified PFA powder is 70 to 99% (more preferably 90 to 99%), the fluidity is less than 30s/50g (more preferably 10 to 25s/50g, still more preferably 10 to 20s/50 g), the mixed powder of the modified PFA powder and the ceramic powder is sprayed with a non-stick coating on the surface of the substrate, which enables to obtain a non-stick coating excellent in performance, the obtained non-stick coating has good hydrophobic self-cleaning property, high surface hardness (Vickers hardness is 300-550HV, preferably 450-550 HV), high coating binding force (binding force is 30-50MPa, preferably 40-50 MPa), good scratch resistance (flat plate wear resistance 6000-14000 times, preferably 11500-14000 times), high spraying efficiency (25-70 s/pcs, preferably 30-40 s/pcs), low coating porosity (1-4.5%, preferably 1-2%), long service life, large coating thickness (30-400 mu m), good acid resistance (no whitening, foaming and other phenomena), good alkali resistance (no whitening, foaming and other phenomena), and salt resistance 13-21 cycles (preferably 20-21 cycles, the period 1 is as follows: 5 weight percent of salt water is continuously heated and boiled for 8 hours, and the temperature is kept for 16 hours at 80 degrees). In addition, the non-stick coating has good wettability inside after surface abrasion, and the wettability of the non-stick coating is kept good as long as the matrix is not exposed (when friction abrasion tests are carried out on three samples, namely the PTFE non-stick coating, the ceramic non-stick coating and the non-stick coating, the non-stick coating only has partial powder falling off in the friction abrasion process, the usability is not affected, the PTFE non-stick coating and the ceramic non-stick coating fall off between sheet layers, the difference is large), and the non-stick coating can be in direct contact with food, so that the food sanitation authentication is met.

Drawings

FIG. 1 is a microstructure of a modified PFA powder obtained in preparation example 1 of the present invention.

Fig. 2 is a microscopic topography of a prior art PFA powder.

Fig. 3 is a schematic structural view of the pot of the present invention.

FIG. 4 is a schematic structural view showing the arrangement of particles constituting the non-stick coating of the present invention, wherein the gray part is ceramic particles (e.g., alumina particles and/or titania particles) and the white part is PFA particles.

Description of the reference numerals

1 is a non-stick coating and 2 is a substrate.

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

In a first aspect, the present invention provides a method of preparing a non-stick coating, the method comprising:

(1) Pretreating a matrix;

(2) Preheating the surface of the substrate obtained in the step (1);

wherein 80% or more, preferably 90% or more, of the modified PFA powder has a sphericity of not less than 70%.

In the process of the present invention, it will be understood by those skilled in the art that sphericity is the ratio of the surface area of a sphere of the same volume as the particle to the surface area of the particle, sphericity of the sphere being equal to 1 and sphericity of the other asperities being less than 1. The sphericity of the modified PFA powder of 80% or more is not less than 70%, which means that the number or probability of particles of the modified PFA powder having sphericity of not less than 70% in the modified PFA powder sampled arbitrarily is 80% or more of the number or probability of particles of the modified PFA powder in the whole modified PFA powder sampled.

Preferably, 90% or more of the modified PFA powder has a sphericity of not less than 70%.

Preferably, the particle diameter D50 of the modified PFA powder is 20 to 100. Mu.m, more preferably 40 to 100. Mu.m, still more preferably 45 to 60. Mu.m.

Preferably, 80% or more, more preferably 90% or more of the modified PFA powder has a sphericity of 70 to 99%, still more preferably 90 to 99%.

Preferably, the fluidity of the modified PFA powder is less than 30s/50g, more preferably 10-25s/50g, still more preferably 10-20s/50g.

Preferably, the purity of the modified PFA powder is 95.5% to 99.99%, more preferably 99% to 99.99%.

Preferably, the melting point of the modified PFA powder is 350-420 ℃, and more preferably 400-420 ℃.

Preferably, the modified PFA powder has a surface roughness Ra of 0.1 to 0.45. Mu.m, more preferably Ra of 0.1 to 0.3. Mu.m.

In the method of the present invention, the modified PFA powder satisfying the foregoing parameter conditions is preferably prepared by a method comprising the steps of:

(a) Mixing PFA powder, a binder, a lubricant and water to prepare a slurry;

(b) And carrying out spray drying treatment on the slurry.

Preferably, in step (a), the PFA powder is present in an amount of 30 to 60 wt%, more preferably 38 to 55 wt%, based on the weight of the slurry; the content of the binder is 0.2 to 2 wt%, more preferably 0.2 to 0.5 wt%; the content of the lubricant is 0.5 to 3 wt%, further preferably 1 to 3 wt%; the water content is 35 to 68% by weight, more preferably 42 to 60% by weight.

Preferably, in step (a), the binder is at least one of polyvinyl alcohol, polyvinyl chloride and polyacrylate.

Preferably, in step (a), the lubricant is at least one of glycerin, paraffin wax and graphite.

Preferably, in step (b), the spray drying treatment is air-flow atomization drying, and the conditions of the air-flow atomization drying include: the atomization pressure is 0.3-0.6MPa, more preferably 0.3-0.5MPa; the flow rate of the atomized air flow is 1-4m ³ Preferably 1 to 3m ³ /h; the inlet temperature is 200-400 ℃, and more preferably 300-350 ℃; the temperature of the air outlet is 50-200 ℃, and more preferably 50-150 ℃.

In the method of the invention, the substrate can be a metal substrate such as a stainless steel substrate, an aluminum alloy substrate, a titanium alloy substrate and the like or a multi-layer (comprising two layers and more than three layers) metal composite substrate. Wherein, the multilayer metal composite matrix can be a stainless steel/aluminum matrix, a stainless steel/copper matrix, a stainless steel/aluminum/copper matrix, etc. Preferably, the thickness of the substrate is 0.5-6mm.

In the method of the present invention, the method of the pretreatment of step (1) may include a blasting treatment and a degreasing treatment, and the method of the blasting treatment and the degreasing treatment is not particularly limited, and may be various methods commonly used in the art, respectively. For example, the method of blasting includes: the air jet pressure is controlled to be 0.2-0.9MPa by adopting 60-150 mesh sand grains (such as glass sand, brown steel sand, black brown jade, white corundum, carborundum and the like), and the obtained roughness is about Ra 2-8 mu m. After the blasting treatment, the fine powder particles and the like remaining on the inner surface of the substrate are removed, and the method of removal is not particularly limited, and may be either cleaned by high-pressure air flow or removed by water washing, which are well known to those skilled in the art and will not be described in detail herein. For example, the degreasing treatment may include alkali washing, acid washing, water washing and high-temperature drying (e.g., drying at 200-450 ℃ C. For 10-15 min) in this order.

In the method of the present invention, preferably, in the step (2), the surface of the substrate obtained in the step (1) is preheated to 100 to 150 ℃.

In the method of the present invention, preferably, in the step (3), the weight ratio of the modified PFA powder to the ceramic powder in the powder mixture is 1: (2-6), further preferably 1: (3-5).

Preferably, the ceramic powder is an alumina powder and/or a titania powder, more preferably an alumina powder and a titania powder, still more preferably, the weight ratio of the alumina powder to the titania powder is 1: (0.05-0.4), and still more preferably 1: (0.2-0.3).

Preferably, the particle diameter D50 of the alumina powder is 5 to 80 μm (more preferably 5 to 30 μm), the sphericity of the alumina powder of 90% or more is 70 to 100%, and the flowability is 10 to 30s/50g.

Preferably, the particle diameter D50 of the titanium oxide powder is 5 to 80 μm (more preferably 5 to 25 μm), the sphericity of the titanium oxide powder of 90% or more is 70 to 100%, and the flowability is 10 to 30s/50g.

Preferably, in step (3), the conditions of the plasma spraying process include: the spraying power is 25-60kW, more preferably 35-45kW, still more preferably 38-42kW; the spraying distance is 60-100mm, more preferably 75-85mm; the spraying angle is 70-90 degrees, more preferably 75-85 degrees; the powder feeding amount is 3.5-10g/min, more preferably 5-7g/min; the PFA spraying temperature is 300-350 ℃, and is more preferably 315-335 ℃; the spraying temperature of the aluminum oxide and the titanium oxide is 2800-3200 ℃, and is more preferably 2900-3100 ℃; the spraying voltage is 50-70V, and more preferably 55-65V; the spraying current is 600-650A, more preferably 620-630A; the spray thickness is 30-400 μm, more preferably 150-300 μm; the main gas is hydrogen, the auxiliary gas is argon, the flow rate of the hydrogen is 2-6L/min, and the more preferable flow rate is 3-5L/min; the argon flow is 25-35L/min, and more preferably 28-32L/min. Wherein, before the plasma spraying treatment, the powder can be mixed and stirred for 1-2 hours, and then dried for 1-1.5 hours at 100-120 ℃.

In a second aspect, the invention provides a non-stick coating prepared by the method described above.

In a third aspect, as shown in fig. 3, the present invention provides a pot comprising a substrate 2 and a non-stick coating 1 formed on the substrate 2, the non-stick coating 1 comprising a mixed layer of ceramic and PFA. Wherein the mixed layer of the ceramic and the PFA is a coating formed by mixed powder of ceramic powder and PFA powder, namely a ceramic/PFA coating.

Preferably, as shown in fig. 4, in the non-stick coating layer, ceramic particles and PFA particles are arranged in a staggered manner.

Preferably, in the non-stick coating, the weight ratio of PFA to ceramic is 1: (2-6), further preferably 1: (3-5).

Preferably, the ceramic is alumina and/or titania, more preferably alumina and titania, still more preferably, the weight ratio of alumina to titania is 1: (0.05-0.4), and still more preferably 1: (0.2-0.3).

The substrate can be a metal substrate such as a stainless steel substrate, an aluminum alloy substrate, a titanium alloy substrate and the like or a multi-layer (comprising two layers and more than three layers) metal composite substrate. Wherein, the multilayer metal composite matrix can be a stainless steel/aluminum matrix, a stainless steel/copper matrix, a stainless steel/aluminum/copper matrix, etc.

Preferably, the thickness of the substrate is 0.5-6mm.

Preferably, the thickness of the non-stick coating is 30 to 400 μm, more preferably 50 to 300 μm, still more preferably 150 to 300 μm.

Preferably, the non-stick coating is a non-stick coating according to the present invention.

In a fourth aspect, the present invention provides a cooking apparatus comprising a pan according to the present invention. Preferably, the cooking device is a frying pan, air frying pan, frying and baking machine, bread machine, electric rice cooker, electric pressure cooker or soymilk machine.

The present invention will be described in detail by way of preparation examples and examples. In the following preparation examples and examples, each material used is commercially available and each method used is a method commonly used in the art unless otherwise specified.

Particle diameter D50 of the PFA powder was measured by a laser particle size analyzer (model KW510, available from Xiamen King electronics Co., ltd.).

Sphericity of PFA powder particles was determined using a particle image analyzer (available from zhuhai eumerk instruments limited, model PIP 8.1).

The flowability of the PFA powder was determined according to GB1482-84 using a Hall flowmeter.

The purity of the PFA powder was determined using an automatic polarimeter (available from Aituo China, model number AP-300).

The melting point of the PFA powder was determined using a micro-melting point tester (available from Jinan Heinai instruments Co., ltd., model MP-300).

The surface roughness Ra of the PFA powder was measured by a surface roughness meter (model TIME3201, available from peak technology limited in beijing age).

The contact angle measurement instrument (available from Shenzhen Xin Heng Sen trade Co., ltd., model XHSCZA-2) was used to measure the original contact angle and the post-friction contact angle, and the measurement range was 0-180 degrees.

The normal PFA powder was purchased from Dajinfu paint (Shanghai) Co., ltd, particle size D50 of 15 μm, sphericity of 95% powder of 18%, fluidity of 78s/50g, purity of 94%, melting point of 345℃and surface roughness of Ra 0.6. Mu.m.

Polyvinyl alcohol was purchased from Shanghai Fox spring technology Co., ltd, model number PVA1788.

Polyvinyl chloride was purchased from Shanghai Ji Ning, inc., model number K55-59.

Polyacrylate was purchased from Changzhou Chunjiang chemical company under the model number SL325.

Alumina powder was purchased from Beijing Yao technology development Co., ltd, particle size D50 of 25 μm,95% sphericity of 95% powder, flowability of 12s/50g.

Titanium oxide powder was purchased from Beijing Yao technology development Co., ltd, particle size D50 of 22 μm,95% of powder sphericity of 92%, flowability of 18s/50g.

Preparation example 1

(1) 47.6kg of ordinary PFA powder, 0.4kg of polyvinyl alcohol, 2kg of glycerin and 50kg of water were mixed to prepare a slurry;

(2) Carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.4MPa, and the flow rate of the atomization airflow is 2m ³ And/h, the inlet temperature is 320 ℃, the air outlet temperature is 100 ℃, and the modified PFA powder S1 is obtained.

As a result, the particle diameter D50 of the modified PFA powder was 52. Mu.m, the sphericity of 96% of the powder was 95%, the flowability was 15s/50g, the purity was 99.9%, the melting point was 410℃and the surface roughness was Ra 0.2. Mu.m. The microstructure of the modified PFA powder is shown in FIG. 1.

Preparation example 2

(1) 54.8kg of ordinary PFA powder, 0.2kg of polyvinyl chloride, 3kg of paraffin wax and 42kg of water were mixed to prepare a slurry;

(2) Carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.3MPa, and the flow rate of the atomization airflow is 1m ³ /h, inlet temperature of300 ℃ and the temperature of an air outlet is 60 ℃ to obtain modified PFA powder S2.

As a result, the particle diameter D50 of the modified PFA powder was 46. Mu.m, the sphericity of 95% of the powder was 93%, the flowability was 13s/50g, the purity was 99.5%, the melting point was 405℃and the surface roughness was Ra 0.15. Mu.m.

Preparation example 3

(1) 38.5kg of ordinary PFA powder, 0.5kg of polyacrylate, 1kg of graphite and 60kg of water were mixed to prepare a slurry;

(2) Carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.5MPa, and the flow rate of the atomization airflow is 3m ³ And/h, wherein the inlet temperature is 350 ℃, the air outlet temperature is 140 ℃, and the modified PFA powder S3 is obtained.

As a result, the particle diameter D50 of the modified PFA powder was 59. Mu.m, the sphericity of 95% of the powder was 98%, the flowability was 18s/50g, the purity was 99.9%, the melting point was 418℃and the surface roughness was Ra 0.28. Mu.m.

Preparation example 4

(1) A slurry was prepared by mixing 32.2kg of ordinary PFA powder, 1kg of polyvinyl alcohol, 1.8kg of glycerin and 65kg of water;

(2) Carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.58MPa, and the flow rate of the atomization airflow is 3.9m ³ And/h, the inlet temperature is 210 ℃, the air outlet temperature is 52 ℃, and the modified PFA powder S4 is obtained.

The particle diameter D50 of the modified PFA powder was measured to be 42 μm, the sphericity of 90% of the powder was 75%, the flowability was 12s/50g, the purity was 96%, the melting point was 352℃and the surface roughness was Ra 0.12. Mu.m.

Preparation example 5

(1) A slurry was prepared by mixing 58kg of ordinary PFA powder, 1.8kg of polyvinyl alcohol, 0.6kg of glycerin and 39.6kg of water;

(2) Carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.32MPa, and the flow rate of atomization airflow is 3.2m ³ And/h, wherein the inlet temperature is 390 ℃, the air outlet temperature is 195 ℃, and the modified PFA powder S5 is obtained.

As a result, the particle diameter D50 of the modified PFA powder was 98. Mu.m, the sphericity of 88% of the powder was 90%, the flowability was 24s/50g, the purity was 99.7%, the melting point was 415℃and the surface roughness was Ra 0.42. Mu.m.

Example 1

This example illustrates a method for preparing a non-stick coating using a plasma spray process.

(1) Pretreating an aluminum pot substrate, wherein the pretreatment method comprises the following steps: a) Deoiling at 55deg.C for 8 min; b) Washing with deionized water; c) Drying at 100deg.C for 5min; d) Adopting 60-80 mesh brown steel sand, carrying out sand blasting treatment on the inner surface of the aluminum pot body under the air jet pressure of 0.6MPa to ensure that the surface roughness of the inner surface is Ra 3 mu m, and then blowing out powder particles remained on the inner surface of the pot body by using air flow; e) Alkaline washing with 40 wt% NaOH solution at 80℃for 1 minute; f) Neutralizing with 20 wt% nitric acid solution for 3 min; g) Washing with deionized water, and drying at 300 ℃ for 12 minutes;

(2) Preheating the surface of the substrate obtained in the step (1) to 120 ℃;

(3) Mixing 160kg of alumina powder, 40kg of titanium oxide powder and 50kg of modified PFA powder S1, drying at 110 ℃ for 1h to obtain a powder mixture, and performing plasma spraying treatment on the powder mixture to form a non-stick coating Q1 on the surface of a substrate; wherein, the conditions of the plasma spraying treatment include: the spraying power is 40kW, the spraying distance is 80mm, the spraying angle is 80+/-1 degrees, the powder feeding amount is 6g/min, the PFA spraying temperature is 330 ℃, the aluminum oxide and titanium oxide spraying temperature is 3000 ℃, the spraying voltage is 60V, the spraying current is 625A, the spraying thickness is 180 mu m, the main gas is hydrogen, the auxiliary gas is argon, the hydrogen flow is 4L/min, and the argon flow is 30L/min.

Example 2

(1) Pretreating a stainless steel pot substrate, wherein the pretreatment method comprises the following steps: a) Deoiling at 55deg.C for 8 min; b) Washing with deionized water; c) Drying at 100deg.C for 5min; d) Adopting 60-80 mesh brown steel sand, carrying out sand blasting treatment on the inner surface of the stainless steel pot base body under the air jet pressure of 0.8MPa to ensure that the surface roughness is Ra 3 mu m, and then blowing out residual powder particles on the inner surface of the pot base body by using air flow; e) Alkaline washing with 40 wt% NaOH solution at 80℃for 1 minute; f) Neutralizing with 20 wt% nitric acid solution for 3 min; g) Washing with deionized water, and drying at 375 ℃ for 11 minutes;

(2) Preheating the surface of the substrate obtained in the step (1) to 100 ℃;

(3) Mixing 125kg of aluminum oxide powder, 25kg of titanium oxide powder and 50kg of modified PFA powder S2, drying at 100 ℃ for 1.5 hours to obtain a powder mixture, and performing plasma spraying treatment on the powder mixture to form a non-stick coating Q2 on the surface of a substrate; wherein, the conditions of the plasma spraying treatment include: the spraying power is 35kW, the spraying distance is 75mm, the spraying angle is 76+/-1 degrees, the powder feeding amount is 7g/min, the PFA spraying temperature is 315 ℃, the aluminum oxide and titanium oxide spraying temperature is 2900 ℃, the spraying voltage is 55V, the spraying current is 630A, the spraying thickness is 150 mu m, the main gas is hydrogen, the auxiliary gas is argon, the hydrogen flow is 3L/min, and the argon flow is 28L/min.

Example 3

(1) Pretreating a stainless steel pot substrate, wherein the pretreatment method comprises the following steps: a) Deoiling at 55deg.C for 8 min; b) Washing with deionized water; c) Drying at 100deg.C for 5min; d) Adopting 60-80 mesh brown steel sand, carrying out sand blasting treatment on the inner surface of the stainless steel pot base body under the air jet pressure of 0.8MPa to ensure that the surface roughness is Ra 4 mu m, and then blowing out residual powder particles on the inner surface of the pot base body by using air flow; e) Alkaline washing with 40 wt% NaOH solution at 80℃for 1 minute; f) Neutralizing with 20 wt% nitric acid solution for 3 min; g) Washing with deionized water, and drying at 450 ℃ for 10 minutes;

(2) Preheating the surface of the substrate obtained in the step (1) to 150 ℃;

(3) Mixing 192kg of alumina powder, 58kg of titanium oxide powder and 50kg of modified PFA powder S3, drying at 100 ℃ for 1.5 hours to obtain a powder mixture, and performing plasma spraying treatment on the powder mixture to form a non-stick coating Q3 on the surface of a substrate; wherein, the conditions of the plasma spraying treatment include: the spraying power is 45kW, the spraying distance is 85mm, the spraying angle is 84+/-1 degrees, the powder feeding amount is 5g/min, the PFA spraying temperature is 335 ℃, the aluminum oxide and titanium oxide spraying temperature is 3100 ℃, the spraying voltage is 65V, the spraying current is 620A, the spraying thickness is 250 mu m, the main gas is hydrogen, the auxiliary gas is argon, the hydrogen flow is 5L/min, and the argon flow is 32L/min.

Example 4

The procedure of example 1 was followed except that the modified PFA powder used in the plasma spray treatment was replaced with modified PFA powder S4.

Example 5

The procedure of example 1 was followed except that the modified PFA powder used in the plasma spray treatment was replaced with modified PFA powder S5.

Example 6

The procedure of example 1 was followed except that in step (3), the powder mixture was a mixture of 80kg of alumina powder, 20kg of titania powder and 50kg of modified PFA powder S1.

Example 7

The procedure of example 1 was followed except that in step (3), the powder mixture was a mixture of 240kg of alumina powder, 60kg of titania powder and 50kg of modified PFA powder S1.

Example 8

The procedure of example 1 was followed except that in step (3), the powder mixture was a mixture of 200kg of alumina powder and 50kg of modified PFA powder S1.

Example 9

The procedure of example 1 was followed except that in step (3), the powder mixture was a mixture of 200kg of titanium oxide powder and 50kg of modified PFA powder S1.

Example 10

The method according to example 1 is different in that, in the step (3), the conditions of the plasma spraying treatment include: the spraying power is 25kW, the spraying distance is 60mm, the spraying angle is 71+/-1 degrees, the powder feeding amount of powder is 3.5g/min, the PFA spraying temperature is 300 ℃, the aluminum oxide and titanium oxide spraying temperature is 2800 ℃, the spraying voltage is 50V, the spraying current is 600A, the spraying thickness is 100 mu m, the main gas is hydrogen, the auxiliary gas is argon, the hydrogen flow is 2L/min, and the argon flow is 25L/min.

Comparative example 1

According to the method of example 1, except that the PFA powder used was a normal PFA powder, the normal PFA powder would clog the spray gun during the plasma spraying, resulting in that the powder could not be delivered and a coating layer could not be formed.

Comparative example 2

The procedure of example 1 was followed except that the non-stick coating was formed in steps (3) - (4) as follows: performing electrostatic spraying treatment by adopting common PFA powder to form a PFA non-stick coating D1 on the surface of a substrate, wherein the conditions of the electrostatic spraying treatment comprise: powder spraying is carried out by adopting an electrostatic spray gun, the voltage is 35kV, the electrostatic current is 15 mu A, the flow speed pressure is 0.45MPa, the atomization pressure is 0.4MPa, the thickness of a sprayed coating is 40 mu m, the powder is dried in an infrared furnace after the spraying is finished, the powder is dried for 10min at a low temperature section of 120 ℃, and the powder is insulated for 20min at a high temperature section of 400 ℃.

Comparative example 3

Spraying a PTFE non-stick coating by adopting an air pressure spraying mode, wherein the coating comprises a bottom layer and a surface layer; the base oil comprises fluororesin, binder, pigment and auxiliary agent, and the surface oil comprises fluororesin, wear-resistant particles and film-forming auxiliary agent. The method comprises the following specific steps:

(1) Pretreating an aluminum pot substrate according to the step (1) of the embodiment 1;

(2) Preheating the surface of the substrate obtained in the step (1) to 85 ℃;

(3) And (3) spraying base oil: the spraying pressure is 0.3MPa, the spraying angle is 70 degrees, the spraying distance is 30cm, the thickness of the film layer is 20 mu m, the drying temperature is 130 ℃, and the heat preservation is carried out for 12min;

(4) Spraying surface oil: the spraying pressure is 0.4MPa, the spraying angle is 70 degrees, the spraying distance is 35 mu m, the film thickness is 30 mu m, the drying and curing temperature is 420 ℃, and the heat preservation is carried out for 15min.

Comparative example 4

Spraying a ceramic non-stick coating by adopting an air pressure spraying mode, wherein the coating comprises a bottom layer and a surface layer; the primer includes a binder, a pigment, and an auxiliary agent, and the topcoat includes silica and alumina. The method comprises the following specific steps:

(2) Preheating the surface of the substrate obtained in the step (1) to 60 ℃;

(3) And (3) spraying base oil: the spraying pressure is 0.3MPa, the spraying angle is 70 degrees, the spraying distance is 25cm, the thickness of a film layer is 25 mu m, the pre-drying temperature is 70 ℃, and the heat preservation is carried out for 10min;

(4) Spraying surface oil: the spraying pressure is 0.3MPa, the spraying distance is 25cm, the spraying angle is 70 degrees, the thickness of the film layer is 10 mu m, and the film layer is sintered at 280 ℃ after the spraying is finished and is kept for 15min.

Test examples

1. Coating surface hardness: the Vickers hardness of each coating was determined according to GB/T9790-1988 using a Vickers hardness tester (available from Shanghai rectangular optics, inc., model HX-1000). The results are shown in Table 1.

2. Coating binding force: coating binding force was measured according to G9 8642-88. The results are shown in Table 1.

3. Coating porosity: the porosity of the coating was determined according to the mechanical industry standard JB/T7509-94 of the people's republic of China. The results are shown in Table 1.

4. Coating spraying efficiency: according to the formula: spraying efficiency= (weight of workpiece after spraying-weight of workpiece before spraying)/(powder feeding amount, deposition rate), wherein the deposition rate was fixed at 70%. The calculation results are shown in Table 1.

5. Scratch resistance of the coating: the cleaning liquid is used for preparing the cleaning water with the concentration of 5 weight percent, the 3M (7447C) scouring pad bears a load of 2.5kgf, the scouring pad is swung left and right for 1 time once, the scouring pad is replaced for 250 times each time, whether the coating falls off or a substrate is exposed after each scraping or not is checked (the exposure of more than 10 lines is taken as a termination test), and the wear-resisting times are recorded. The results are shown in Table 1.

6. Acid, alkali, salt:

acid resistance: adding acetic acid solution with the concentration of 5 wt% into the inner pot until reaching the maximum scale water level of the inner wall of the inner pot, putting the inner pot into a corresponding pot, electrifying the inner pot, closing the cover, continuously heating and boiling (keeping the boiling state) for 10 minutes, then preserving heat at 100 ℃ and soaking for 24 hours, cleaning the inner pot after the test is finished, visually checking the surface change condition of the coating, and the result is shown in table 2.

Alkali resistance: adding 0.5 wt% sodium hydroxide solution into the inner pot until reaching the maximum scale water level of the inner wall of the inner pot, putting the inner pot into a corresponding pot, electrifying the cover, continuously heating and boiling (keeping boiling state) for 10 minutes, then preserving heat at 100 ℃ and soaking for 24 hours, cleaning the inner pot after the test is finished, and visually checking the surface change condition of the coating, wherein the result is shown in Table 2.

Salt resistance: adding sodium chloride solution with the concentration of 5 wt% into an inner pot until the maximum scale water level of the inner wall of the inner pot, putting the inner pot into a corresponding pot, electrifying a sealing cover, continuously heating and boiling for 8 hours (supplementing water 1 time every 2 hours, keeping the liquid level at the position at the beginning of the test), keeping the temperature at 80 ℃ for 16 hours as a period, visually checking the surface change condition of the coating after each period test, and recording the period number of the bad phenomena such as foaming, protruding points and the like of the coating, wherein the result is shown in Table 2.

7. Abrasion resistance and wettability: the frictional wear test was performed according to GB/T1768-79 (89), the contact angle (the original contact angle and the post-frictional contact angle, respectively) and the weight before and after the frictional wear test were measured and weighed, and the weight loss ratio was calculated according to the formula, wherein the weight loss ratio= (weight before friction-weight after friction)/weight before friction, and the results are shown in table 3. Wherein, the test result shows that: the non-stick coating of the invention has good wettability inside after surface abrasion, and the wettability is kept good as long as the substrate is not exposed, and the friction abrasion test is carried out on three samples, namely the PTFE non-stick coating, the ceramic non-stick coating and the non-stick coating of the invention, so that the following can be found: the non-stick coating of the invention only has partial powder falling off in the friction and abrasion process, the usability is not affected, and the PTFE non-stick coating and the ceramic non-stick coating are both flaky falling off between layers, and the difference is larger.

TABLE 1

Note that: -no detectable indication, the same is true below.

TABLE 2

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TABLE 3 Table 3

	Number of rubs	Loss ratio (%)	Original contact angle (°)	Contact angle after rubbing (°)
					Example 1	1000	1.2	105	100
Example 1	2000	2.2	105	98
					Example 1	3000	3.1	105	95
Example 2	1000	1.3	110	105
					Example 3	1000	1.15	100	96
Example 4	1000	2.1	98	82
					Example 5	1000	2.5	95	80
Example 6	1000	1.4	113	107
					Example 7	1000	1.0	99	90
Example 8	1000	1.8	103	95
					Example 9	1000	1.5	101	91
Example 10	1000	2.5	100	91
					Comparative example 1	--	--	--	--
Comparative example 2	1000	6.0	125	90
					Comparative example 3	1000	8.9	121	87
Comparative example 4	1000	4.8	110	78

As can be seen from the results in tables 1 to 3, in the method for preparing the non-stick coating by adopting the plasma spraying technology, a non-stick coating layer can be sprayed on the surface of a substrate by adopting the mixture of the specific modified PFA powder and the ceramic powder, the non-stick coating layer with excellent performance can be obtained, and the obtained non-stick coating layer has the advantages of high surface hardness, high coating binding force, good scratch resistance, good corrosion resistance, good wettability, long service life and the like.

Among them, comparing the results of examples 1 and 4 to 5, it is found that when the particle diameter D50 of the modified PFA powder is 45 to 60 μm, the sphericity of 80% or more of the powder is 90 to 99%, and the fluidity is 10 to 20s/50g, the surface hardness, coating binding force, scratch resistance, corrosion resistance, wettability and service life of the non-tacky coating can be further improved.

Comparing the results of example 1 and example 10, it is known that under specific plasma spraying treatment conditions (i.e., spraying power of 35-45kW, spraying distance of 75-85mm, spraying angle of 75-85 °, powder feeding amount of 5-7g/min, PFA spraying temperature of 315-335 ℃, spraying temperature of 2900-3100 ℃ for aluminum oxide and titanium oxide, spraying voltage of 55-65V, spraying current of 620-630A, spraying thickness of 150-300 μm, main gas of hydrogen and auxiliary gas of argon, hydrogen flow of 3-5L/min, and argon flow of 28-32L/min), the surface hardness, coating binding force, scratch resistance, corrosion resistance, wettability and service life of the non-adhesive coating can be further improved.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. A method of preparing a non-stick coating, the method comprising:

(1) Pretreating a matrix;

(2) Preheating the surface of the substrate obtained in the step (1);

wherein 80% or more of the modified PFA powder has a sphericity of not less than 70%,

the particle diameter D50 of the modified PFA powder is 20-100 mu m,

the fluidity of the modified PFA powder is less than 30s/50g.

2. The method of claim 1, wherein the modified PFA powder has a particle size D50 of 40-100 μm; and/or

80% or more of the modified PFA powder has a sphericity of 70-99%; and/or

The fluidity of the modified PFA powder is 10-25s/50g.

3. The method according to claim 2, wherein the modified PFA powder has a particle size D50 of 45-60 μm; and/or

More than 90% of the modified PFA powder has a sphericity of 90-99%; and/or

The fluidity of the modified PFA powder is 10-20s/50g.

4. The method of any of claims 1-3, wherein the purity of the modified PFA powder is 95.5% -99.99%; and/or

The melting point of the modified PFA powder is 350-420 ℃; and/or

The surface roughness of the modified PFA powder is Ra 0.1-0.45 mu m.

5. The method of claim 4, wherein the purity of the modified PFA powder is 99-99.99%; and/or

The melting point of the modified PFA powder is 400-420 ℃; and/or

The surface roughness of the modified PFA powder is Ra 0.1-0.3 mu m.

6. A method according to any one of claims 1-3, wherein the modified PFA powder is prepared by a process comprising the steps of:

(a) Mixing PFA powder, a binder, a lubricant and water to prepare a slurry;

(b) And carrying out spray drying treatment on the slurry.

7. The method of claim 6, wherein in step (a), the PFA powder is contained in an amount of 30 to 60% by weight based on the weight of the slurry; the content of the binder is 0.2-2 wt%; the content of the lubricant is 0.5-3 wt%; the water content is 35-68 wt.%.

8. The method of claim 7, wherein in step (a), the PFA powder is contained in an amount of 38 to 55 wt% based on the weight of the slurry; the content of the binder is 0.2-0.5 wt%; the content of the lubricant is 1-3 wt%; the water content is 42-60 wt.%.

9. The method of claim 6, wherein in step (b), the spray drying process is air-flow spray drying, and the conditions of the air-flow spray drying include: the atomization pressure is 0.3-0.6MPa; the flow rate of the atomized air flow is 1-4m ³ /h; the inlet temperature is 200-400 ℃; the temperature of the air outlet is 50-200 ℃.

10. According to claimThe method of claim 9, wherein in step (b), the conditions of the gas stream atomization drying include: the atomization pressure is 0.3-0.5MPa; the flow rate of the atomized air flow is 1-3m ³ /h; the inlet temperature is 300-350 ℃; the temperature of the air outlet is 50-150 ℃.

11. A method according to any one of claims 1 to 3, wherein in step (2) the substrate surface obtained in step (1) is preheated to 100-150 ℃.

12. A method according to any one of claims 1 to 3, wherein in step (3), the weight ratio of modified PFA powder to ceramic powder in the powder mixture is 1:2-6.

13. The method of claim 12, wherein in step (3), the weight ratio of the modified PFA powder to the ceramic powder in the powder mixture is 1:3-5.

14. A method according to any one of claims 1-3, wherein the ceramic powder is an alumina powder and/or a titania powder.

15. The method of claim 14, wherein the ceramic powder is an alumina powder and a titania powder.

16. The method of claim 15, wherein the weight ratio of alumina powder to titania powder is 1:0.05-0.4.

17. The method according to claim 15, wherein the alumina powder has a particle diameter D50 of 5 to 80 μm, a sphericity of 70 to 100% and a flowability of 10 to 30s/50g.

18. The method according to claim 15, wherein the particle diameter D50 of the titanium oxide powder is 5 to 80 μm, the sphericity of the titanium oxide powder of 90% or more is 70 to 100%, and the flowability is 10 to 30s/50g.

19. A method according to any one of claims 1 to 3, wherein in step (3), the conditions of the plasma spraying treatment comprise: the spraying power is 25-60kW; the spraying distance is 60-100mm; the spraying angle is 70-90 degrees; the powder feeding amount is 3.5-10g/min; the PFA spraying temperature is 300-350 ℃; the spraying temperature of the aluminum oxide and the titanium oxide is 2800-3200 ℃; the spraying voltage is 50-70V; the spraying current is 600-650A; the spraying thickness is 30-400 mu m; the main gas is hydrogen, the auxiliary gas is argon, and the flow rate of the hydrogen is 2-6L/min; the flow rate of argon is 25-35L/min.

20. The method of claim 19, wherein in step (3), the conditions of the plasma spray process comprise: the spraying power is 35-45kW; the spraying distance is 75-85mm; the spraying angle is 75-85 degrees; the powder feeding amount is 5-7g/min; the PFA spraying temperature is 315-335 ℃; the spraying temperature of the aluminum oxide and the titanium oxide is 2900-3100 ℃; the spraying voltage is 55-65V; the spraying current is 620-630A; the spraying thickness is 150-300 mu m; the main gas is hydrogen, the auxiliary gas is argon, and the flow rate of the hydrogen is 3-5L/min; the argon flow is 28-32L/min.

21. The method of claim 1, wherein 90% or more of the modified PFA powder has a sphericity of not less than 70%.

22. A non-stick coating prepared by the method of any one of claims 1-21.

23. A cookware comprising a substrate and a non-stick coating formed on the substrate, said non-stick coating comprising the non-stick coating of claim 22.

24. The pot of claim 23, wherein the ceramic particles and PFA particles in the non-stick coating are arranged in a staggered pattern.

25. The pan of claim 23, wherein in the non-stick coating, the weight ratio of PFA to ceramic is 1:2-6.

26. The pan of claim 25, wherein in the non-stick coating, the weight ratio of PFA to ceramic is 1:3-5.

27. The pan of claim 23, wherein the ceramic is alumina and/or titania.

28. The pan of claim 27, wherein the ceramic is alumina and titania.

29. The pan of claim 23, wherein the thickness of the base is 0.5-6mm.

30. The pan of claim 23, wherein the non-stick coating is 30-400 μιη.

31. The pan of claim 30, wherein the non-stick coating is 50-300 μιη.

32. The pan of claim 31, wherein the non-stick coating is 150-300 μιη.

33. A cooking device, characterized in that it comprises a pan according to any one of claims 23-32.

34. The cooking apparatus of claim 33, wherein the cooking apparatus is a wok, a fryer, an air fryer, a roaster, a bread maker, an electric rice cooker, an electric pressure cooker, or a soymilk machine.