CN108912563B

CN108912563B - Modified PFA powder, preparation method thereof, non-stick coating, pot and cooking equipment

Info

Publication number: CN108912563B
Application number: CN201710276939.4A
Authority: CN
Inventors: 李兴航; 曹达华; 李康; 李洪伟; 杨玲; 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: 2021-11-19
Anticipated expiration: 2037-04-25
Also published as: CN108912563A

Abstract

The invention relates to the technical field of electric heating appliances, and discloses modified PFA powder, a preparation method thereof, a non-stick coating, a pot and cooking equipment, wherein the sphericity of more than 80 percent of the modified PFA powder is not less than 70 percent. The modified PFA powder can meet the construction of new technologies such as hot spraying, cold spraying and the like at the same time, and the obtained non-stick coating with excellent performance has the advantages of high surface hardness, high coating bonding force, good scratch resistance, good corrosion resistance, long service life and the like.

Description

Modified PFA powder, preparation method thereof, non-stick coating, pot and cooking equipment

Technical Field

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

Background

At present, the inner containers of electric cookers and electric pressure cookers all use non-stick coatings to realize the easy cleaning function of cookers, the non-stick coatings are generally organic fluororesin or inorganic ceramic non-stick coatings, the existing fluororesin and ceramic non-stick coatings are mostly prepared by adopting an air pressure spraying mode, and the preparation mode has the advantages of batch production, high preparation efficiency and the like, but also has a plurality of defects, such as: the coating obtained by spraying compressed air and then sintering at high temperature has low binding force, generally the film layer cannot be too thick (20-50 mu m), the surface hardness is low, the scratch resistance is poor, and the coating is easy to lose effectiveness such as coating falling and bubbling in the using process (the cooking process of a user), thereby influencing the service life of electric cookers and electric pressure cookers. In addition, PFA non-stick coating can be prepared by electrostatic spraying with PFA powder (PFA is copolymer of tetrafluoroethylene and perfluoropropylethylene, also called soluble polytetrafluoroethylene, the existing PFA powder, the particle diameter D50 is 5-30 μm, the sphericity of more than 90% is 10-30%, the fluidity is 30-100s/50g, the purity is 90-95%, the melting point is 300-400 ℃, and the surface roughness is Ra 0.5-0.8 μm), and the coating thickness can reach 50-100 μm, but the coating surface hardness is too low, the bonding force is low, the cooking process is easy to scratch and lose efficacy (the Vickers hardness is 50-100HV, the bonding force is 5-10MPa, the spraying efficiency is 100-.

Therefore, a new non-stick coating is urgently needed to be developed to overcome the defects of low surface hardness, poor scratch resistance, short service life and the like of the non-stick coatings of fluorine resin and ceramics, and new requirements for the powder are required to be provided for realizing the performances, so that the development of a new PFA powder to meet the requirements has important practical significance and market application value.

Disclosure of Invention

The invention aims to overcome the defects of low surface hardness, poor scratch resistance, short service life and the like of a non-stick coating in the prior art, and provides a modified PFA powder, a preparation method thereof, the non-stick coating, a cooker and cooking equipment.

The inventor of the present invention has creatively found in research that, in the existing PFA powder, the particle size D50 is 5-30 μm, the sphericity of more than 90% is 10-30%, the fluidity is 30-100s/50g, the purity is 90-95%, the melting point is 300-, the particle size D50 of the modified PFA powder is 20-100 mu m, the sphericity of more than 80% of the modified PFA powder is 70-99%, and the fluidity of the modified PFA powder is less than 30s/50 g).

In order to achieve the above object, the present invention provides, in a first aspect, a modified PFA powder, 80% or more of which has a sphericity of not less than 70%.

In a second aspect, the present invention provides a method of preparing a modified PFA powder, the method comprising:

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

(2) and (4) carrying out spray drying treatment on the slurry.

In a third aspect, the present invention provides a modified PFA powder prepared by the above method.

In a fourth aspect, the present invention provides a non-stick coating prepared from a material comprising the modified PFA powder of the present invention.

In a fifth aspect, the invention provides a pot, which comprises a base body and a non-stick coating formed on the base body, wherein the non-stick coating is the non-stick coating provided by the invention.

In a sixth aspect, the invention provides a cooking apparatus comprising a pan according to the invention.

According to the modified PFA powder of the present invention, 80% or more of the powder has a sphericity of not less than 70% (spherical or nearly spherical in microscopic morphology), 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% (still more preferably 90 to 99%), the fluidity is less than 30s/50g (still more preferably 10 to 25s/50g, still more preferably 10 to 20s/50g), the non-stick coating can be applied by new techniques such as thermal spraying, cold spraying, etc., and the non-stick coating obtained has a high surface hardness (Vickers hardness of 75 to 550HV), and has a good non-stick property, High coating binding force (the binding force is 20-50MPa), good scratch resistance (3500 times of plate abrasion resistance and 12000 times), high spraying efficiency (25-70s/pcs, preferably 25-40s/pcs), low coating porosity (1-4.5%, preferably 1-2%), long service life, large coating thickness (30-500 μm), good acid resistance (no phenomena of whitening, foaming and the like), good alkali resistance (no phenomena of whitening, foaming and the like), 12-20 salt resistance cycles (preferably 18-20 cycles, 1 cycle is that 5 weight percent of saline water is continuously heated and boiled for 8 hours, 80 degrees of continuous heat preservation for 16 hours) and the like.

Drawings

FIG. 1 is a microscopic topography of a modified PFA powder of the present invention.

FIG. 2 is a microscopic morphology of a conventional PFA powder.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect, the present invention provides a modified PFA powder, 80% or more of which has a sphericity of not less than 70%.

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 a particle to the surface area of the particle, the sphericity of a sphere being equal to 1 and the sphericity of other convexities being less than 1. The sphericity of 80% or more of the modified PFA powder is not less than 70%, which means that the proportion of the number or probability of particles of the modified PFA powder having a sphericity of not less than 70% to the total number or probability of particles of the modified PFA powder in an arbitrarily sampled modified PFA powder is 80% or more.

Preferably, 90% 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 preferably 20 to 100. mu.m, more preferably 40 to 100. mu.m, and still more preferably 45 to 60 μm.

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

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

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

Preferably, the modified PFA powder has a melting point of 350-420 deg.C, more preferably 400-420 deg.C.

The surface roughness Ra of the modified PFA powder is preferably 0.1 to 0.45. mu.m, more preferably Ra 0.1 to 0.3. mu.m.

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

(2) and (4) carrying out spray drying treatment on the slurry.

In step (1), the content of the PFA powder is preferably 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% by weight, more preferably 0.2 to 0.5% by weight; the content of the lubricant is 0.5 to 3% by weight, more preferably 1 to 3% by weight; the content of water is 35 to 68% by weight, more preferably 42 to 60% by weight.

The binder and the lubricant are not particularly limited and may be a commonly used binder and lubricant, respectively, for example, the binder may be at least one of polyvinyl alcohol, polyvinyl chloride, and polyacrylate, and the lubricant may be at least one of glycerin, paraffin, and graphite.

Preferably, in step (2), the spray drying process is carried out by gas-flow atomization drying, and the conditions of the gas-flow atomization drying include: the atomization pressure is 0.3-0.6MPa, and the optimized pressure is 0.3-0.5 MPa; the flow rate of the atomized air flow is 1-4m³H, more preferably 1 to 3m³H; the inlet temperature is 200 ℃ to 400 ℃, and more preferably 300 ℃ to 35-0 ℃; the temperature of the air outlet is 50-200 ℃, and the preferable temperature is 50-150 ℃.

The method of forming the non-stick coating using the material comprising the modified PFA powder according to the present invention can be any of various methods that can be made into a non-stick coating, preferably a cold spray method or a thermal spray method.

Wherein, the cold spraying method preferably comprises the following steps:

(1) pretreating a substrate;

(2) preheating the surface of the substrate obtained in the step (1) to 100-150 ℃;

(3) performing cold spraying treatment by using modified PFA powder to form a PFA non-stick coating on the surface of the substrate, wherein the conditions of the cold spraying treatment comprise: the spraying gas is N₂The spraying distance is 30-40mm, the spraying airflow temperature (gas heating temperature) is 150-250 ℃, the spraying pressure is 2.5-3MPa, the spraying angle is 70-80 ℃, the powder feeding frequency is 15-25Hz, the powder feeding rate is 1-1.2L/min, the critical speed of the powder is 150-180m/s, and the spraying thickness is 150-250 mu m.

Wherein, preferably, the method of thermal spraying comprises:

(1) pretreating a substrate;

(2) preheating the surface of the matrix to 100-150 ℃;

(3) and mixing the aluminum oxide powder, the titanium oxide powder and the modified PFA powder to obtain a powder mixture, and carrying out plasma spraying treatment on the powder mixture to form the non-stick coating on the surface of the substrate.

Wherein the ratio of the weight of the modified PFA powder to the sum of the weights of the alumina powder and the titanium oxide powder is (1-2): (3-4); the weight ratio of the alumina powder to the titanium oxide powder is (90-95): (10-5).

Wherein the alumina powder has a particle diameter D50 of 5 to 80 μm (preferably 5 to 30 μm), a sphericity of 70 to 100% or more of the alumina powder, and a fluidity of 10 to 25s/50 g.

Wherein the titanium oxide powder has a particle diameter D50 of 5 to 80 μm (preferably 5 to 25 μm), a sphericity of 90% or more of the titanium oxide powder of 70 to 100%, and a fluidity of 10 to 25s/50 g.

Wherein, the plasma spraying treatment conditions comprise: the spraying power is 35-45kW, 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-.

In the cold spraying and hot spraying methods, the substrate may be a metal substrate such as a stainless steel substrate, an aluminum alloy substrate, a titanium alloy substrate, or a multi-layer (including two or more layers) metal composite substrate. Wherein, the multi-layer metal composite substrate can be a stainless steel/aluminum substrate, a stainless steel/copper substrate, a stainless steel/aluminum/copper substrate, and the like. Preferably, the thickness of the substrate is 0.5-6 mm.

Among them, in the above cold spray and thermal spray methods, the method of the pretreatment may include a sand blast treatment and a degreasing treatment, and the methods of the sand blast treatment and the degreasing treatment are 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 sand grains (such as glass sand, brown steel sand, black brown jade, white corundum, carborundum and the like) with 60-150 meshes, and the obtained roughness is about Ra 2-8 mu m. After the sandblasting, the residual fine powder particles on the inner surface of the substrate are removed, and the method for removing is not particularly limited, and the residual fine powder particles can be removed by blowing them clean with a high-pressure gas flow or by washing them with water, which are well known to those skilled in the art and will not be described herein. For example, the degreasing treatment may sequentially comprise alkali washing, acid washing, water washing and high-temperature drying (e.g. drying at 400 ℃ for 10-15min at 200-.

In a sixth aspect, the invention provides a cooking apparatus comprising a pan according to the invention. Preferably, the cooking device is a frying pan, an air fryer, a frying and baking machine, a bread maker, an electric cooker, an electric pressure cooker or a soybean milk maker.

The present invention will be described in detail below by way of preparation examples and examples. In the following preparations and examples, unless otherwise specified, the materials used are commercially available, and the methods used are those commonly used in the art.

The particle diameter D50 of the PFA powder was measured by a laser particle size analyzer (available from xiamen kowang electronics ltd., model number KW 510).

The sphericity of the PFA powder particles was determined using a particle image analyzer (available from Zhuhai Oumec instruments Ltd., model number PIP 8.1).

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

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

The melting point of the PFA powder was measured using a micro melting point apparatus (available from Atlantic Hainan instruments, Inc., model No. MP-300).

The surface roughness Ra of the PFA powder was measured by a surface roughness meter (model TIME3201, available from Peak technologies, Inc., of Beijing TIME).

A conventional PFA powder was purchased from Dajin Fluorine coating (Shanghai) Co., Ltd., particle diameter D50 was 15 μm, sphericity of 95% powder was 18%, fluidity was 78s/50g, purity was 94%, melting point was 345 ℃ and surface roughness was Ra 0.6. mu.m.

Polyvinyl alcohol was purchased from Shanghai Fusichunshi engineering and technology, Inc. and was designated PVA 1788.

Polyvinyl chloride was purchased from Shanghai Jinning industries, Inc. under the model number K55-59.

The polyacrylate was purchased from Heizhou Chunjiang chemical company under model number SL 325.

The alumina powder was purchased from Beijing Yao science and technology development Co., Ltd, and had a particle size D50 of 25 μm, 95% sphericity of the powder and fluidity of 12s/50 g.

The titanium oxide powder was purchased from Beijing Yao science and technology development Co., Ltd, and had a particle diameter D50 of 22 μm, a sphericity of 95% of the powder of 92%, and a flowability of 18s/50 g.

Preparation example 1

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

(2) and carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.4MPa, and the atomization airflow flow is 2m³And h, the inlet temperature is 320 ℃, and the outlet temperature is 100 ℃, so that the modified PFA powder S1 is obtained.

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

Preparation example 2

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

(2) and carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.3MPa, and the atomization airflow flow is 1m³And h, the inlet temperature is 300 ℃, and the outlet temperature is 60 ℃, so that the modified PFA powder S2 is obtained.

The modified PFA powder was found to have a particle diameter D50 of 46 μm, a 95% sphericity of 93%, a flowability of 13s/50g, a purity of 99.5%, a melting point of 405 ℃ and a surface roughness Ra of 0.15. mu.m.

Preparation example 3

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

(2) and carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.5MPa, and the atomization airflow flow is 3m³H, inlet temperature is 350 ℃, and air is dischargedThe mouth temperature was 140 ℃ to obtain modified PFA powder S3.

The modified PFA powder was found to have a particle diameter D50 of 59 μm, a 95% sphericity of 98%, a flowability of 18s/50g, a purity of 99.9%, a melting point of 418 ℃ and a surface roughness Ra of 0.28. mu.m.

Preparation example 4

(1) Mixing 32.2kg of ordinary PFA powder, 1kg of polyvinyl alcohol, 1.8kg of glycerin and 65kg of water to prepare slurry;

(2) and carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.58MPa, and the atomization airflow flow is 3.9m³And h, the inlet temperature is 210 ℃, the outlet temperature is 52 ℃, and the modified PFA powder S4 is obtained.

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

Preparation example 5

(1) Mixing 58kg of ordinary PFA powder, 1.8kg of polyvinyl alcohol, 0.6kg of glycerin and 39.6kg of water to prepare slurry;

(2) and carrying out airflow atomization drying treatment on the slurry, wherein the airflow atomization drying conditions comprise: the atomization pressure is 0.32MPa, and the atomization airflow flow is 3.2m³And h, the inlet temperature is 390 ℃, the outlet temperature is 195 ℃ to obtain the modified PFA powder S5.

The modified PFA powder was found to have a particle diameter D50 of 98 μm, a sphericity of 90% of 88%, a flowability of 24s/50g, a purity of 99.7%, a melting point of 415 ℃ and a surface roughness Ra of 0.42. mu.m.

Example 1

This example illustrates the preparation of a non-stick coating by cold spray.

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

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

(3) performing cold spraying treatment by using modified PFA powder S1 to form a PFA non-stick coating P1 on the surface of the substrate, wherein the conditions of the cold spraying treatment comprise: the spraying gas is N₂The spraying distance was 35mm, the spraying air flow temperature was 200 ℃, the spraying pressure was 2.8MPa, the spraying angle was 75 ° ± 1 °, the powder feeding frequency was 20Hz, the powder feeding rate was 1.1L/min, the critical rate of the powder was 160m/s, and the spraying thickness was 180 μm.

Examples 2 to 5

Following the procedure of example 1, except that the modified PFA powders used in examples 2-5 were modified PFA powders S2-S5, respectively, the PFA non-stick coatings P2-P5 were obtained, respectively.

Example 6

This example illustrates the preparation of a non-stick coating by thermal spraying.

(3) mixing 92kg of alumina powder, 8kg of titanium oxide powder and 50kg of modified PFA powder S1 to obtain a powder mixture, and carrying out plasma spraying treatment on the powder mixture to form a non-stick coating Q1 on the surface of a substrate; wherein, the plasma spraying treatment conditions comprise: the spraying power is 40kW, the spraying distance is 80mm, the spraying angle is 80 degrees +/-1 degrees, the powder feeding amount is 7g/min, the PFA spraying temperature is 330 ℃, the alumina and titanium oxide spraying temperature is 3000 ℃, the spraying voltage is 60V, the spraying current is 625A, the spraying thickness is 180 μm, the main gas is hydrogen, the auxiliary gas is argon, the hydrogen flow is 4L/min, and the argon flow is 30L/min.

Examples 7 to 10

Following the procedure of example 6, except that the modified PFA powders used in examples 7-10 were modified PFA powders S2-S5, respectively, the PFA non-stick coatings Q2-Q5 were obtained, respectively.

Comparative example 1

According to the method of example 1, except that the PFA powder in comparative example 1 is a conventional PFA powder, the coating deposition efficiency is low due to poor flowability of the conventional PFA powder, and the resulting coating D1 is thin and has extremely poor mechanical properties.

Comparative example 2

According to the method of example 6, except that the PFA powder in comparative example 2 was a normal PFA powder, the normal PFA powder clogged the spray gun during the plasma spraying, so that the powder could not be delivered and the coating layer could not be formed.

Comparative example 3

The process of example 1 was followed except that the non-stick coating was formed in steps (3) to (4) by: performing electrostatic spraying treatment by using common PFA powder to form a PFA non-stick coating D2 on the surface of the 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 muA, the flow velocity pressure is 0.45MPa, the atomization pressure is 0.4MPa, the thickness of the sprayed coating is 40μm, after the spraying is finished, the sprayed coating is dried in an infrared furnace, the dried coating is dried at the low temperature of 120 ℃ for 10min, and the heat is preserved at the high temperature of 400 ℃ for 20 min.

Test examples

1. Coating surface hardness: the Vickers hardness of each coating was determined according to GB/T9790-. The results are shown in Table 1.

2. Coating binding force: the coating cohesion is determined according to G98642-88. The results are shown in Table 1.

3. Porosity of the coating: and (3) determining the porosity of the coating 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: the spraying efficiency was calculated as (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: washing water with the concentration of 5 weight percent and 3M (7447C) scouring pad with the load of 2.5kgf are prepared by using the scouring liquid, the left-right swinging is carried out for 1 time, the scouring pad is replaced every 250 times, whether the coating falls off or the base material is exposed after each scraping is checked (the test is ended by exposing more than or equal to 10 lines), and the abrasion resistance times are recorded. The results are shown in Table 1.

6. Acid, alkali and salt resistance:

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

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

Salt tolerance: adding a sodium chloride solution with the concentration of 5 weight percent into the inner pot until the position of the maximum scale water level of the inner wall of the inner pot, putting the inner pot into a corresponding pot, electrifying and closing the cover, continuously heating and boiling for 8 hours (replenishing water for 1 time every 2 hours, keeping the liquid level at the position of the beginning of the test), keeping the temperature at 80 ℃ for 16 hours to form a period, visually checking the change condition of the surface of the coating after the test of each period, and recording the period number of the coating with the undesirable phenomena of foaming, salient points and the like, wherein the results are shown in Table 2.

TABLE 1

Note: - -means that it was not detectable.

TABLE 2

The results in tables 1-2 show that the modified PFA powder of the invention can meet the construction requirements of new technologies such as hot spraying, cold spraying and the like, and can obtain a non-stick coating with excellent performance, and the obtained non-stick coating has the advantages of high surface hardness, high coating binding force, good scratch resistance, good corrosion resistance, long service life and the like.

Wherein, when the particle diameter D50 of the modified PFA powder is 45-60 μm, the sphericity of more than 80 percent of the powder is 90-99 percent, and the fluidity is 10-20s/50g, the surface hardness, the coating bonding force, the scratch resistance, the corrosion resistance and the service life of the non-stick coating can be further improved.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A modified PFA powder for thermal spraying or cold spraying, characterized in that 80% or more of said modified PFA powder has a sphericity of not less than 70%, and said modified PFA powder has a particle diameter D50 of 40 to 100 μm;

wherein the sphericity is a ratio of a surface area of a sphere having the same volume as the particle to a surface area of the particle,

the preparation method of the modified PFA powder comprises the following steps:

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

(2) and (4) carrying out spray drying treatment on the slurry.

2. The modified PFA powder for thermal spray or cold spray according to claim 1, wherein 90% or more of the modified PFA powder has a sphericity of not less than 70%.

3. The modified PFA powder for thermal spray or cold spray according to claim 1, wherein 80% or more of the modified PFA powder has a sphericity of 70-99%; and/or

The modified PFA powder has a flowability of less than 30s/50 g.

4. The modified PFA powder for thermal spray or cold spray according to claim 3, wherein 90% or more of the modified PFA powder has a sphericity of 70-99%; and/or

The flowability of the modified PFA powder is 10 to 25s/50 g.

5. The modified PFA powder for thermal spray or cold spray according to claim 4, wherein the particle size D50 of the modified PFA powder is 45-60 μ ι η; and/or

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

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

6. The modified PFA powder for thermal spray or cold spray according to any one of claims 1-5, wherein the purity of the modified PFA powder is 95.5% to 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 μm.

7. The modified PFA powder for thermal spray or cold spray according to claim 6, 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 μm.

8. The modified PFA powder for thermal spray or cold spray according to claim 1, wherein in step (1), the PFA powder is present in an amount of 30 to 60 wt. -%, 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.%.

9. The modified PFA powder for thermal spray or cold spray according to claim 8, wherein in step (1), the PFA powder is present 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%.

10. The modified PFA powder for thermal spray or cold spray according to claim 1, wherein the binder is at least one of polyvinyl alcohol, polyvinyl chloride, and polyacrylate.

11. The modified PFA powder for thermal spray or cold spray according to claim 1, wherein the lubricant is at least one of glycerol, paraffin wax, and graphite.

12. The modified PFA powder for thermal spraying or cold spraying according to any one of claims 1, 8, 9, 10 and 11, wherein in step (2), the spray drying process is a gas flow spray drying process, and the conditions of the gas flow spray drying process include: the atomization pressure is 0.3-0.6 MPa; the flow rate of the atomized air flow is 1-4m³H; the inlet temperature is 200-400 ℃; go outThe tuyere temperature was 50-200 ℃.

13. The modified PFA powder for thermal spray or cold spray according to claim 12, wherein in step (2), the spray drying process is a gas flow spray drying process, and the conditions of the gas flow spray drying process include: the atomization pressure is 0.3-0.5 MPa; the flow rate of the atomized air flow is 1-3m³H; the inlet temperature is 300-350 ℃; the temperature of the air outlet is 50-150 ℃.

14. A method of preparing a modified PFA powder, the method comprising:

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

(2) carrying out spray drying treatment on the slurry;

wherein, in the step (1), the content of the PFA powder is 30-60 wt% 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% by weight,

wherein 80% or more of the modified PFA powder has a sphericity of not less than 70%, and the particle diameter D50 of the modified PFA powder is 40 to 100 μm;

sphericity is the ratio of the surface area of a sphere of the same volume as a particle to the surface area of the particle.

15. The method according to claim 14, wherein in step (1), the PFA powder is present in an amount of 38-55 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%.

16. The method of claim 14, wherein the binder is at least one of polyvinyl alcohol, polyvinyl chloride, and polyacrylate.

17. The method of claim 14, wherein the lubricant is at least one of glycerol, paraffin, and graphite.

18. The method according to any one of claims 14 to 17, wherein in the step (2), the spray drying treatment is carried out by gas flow atomization drying, and the conditions of the gas flow atomization drying comprise: the atomization pressure is 0.3-0.6 MPa; the flow rate of the atomized air flow is 1-4m³H; the inlet temperature is 200-400 ℃; the temperature of the air outlet is 50-200 ℃.

19. The method according to claim 18, wherein in the step (2), the spray drying process is carried out by gas flow atomization drying, and the conditions of the gas flow atomization drying comprise: the atomization pressure is 0.3-0.5 MPa; the flow rate of the atomized air flow is 1-3m³H; the inlet temperature is 300-350 ℃; the temperature of the air outlet is 50-150 ℃.

20. The method of claim 14, wherein 90% or more of the modified PFA powder has a sphericity of not less than 70%.

21. The method of claim 14, wherein 80% or more of the modified PFA powder has a sphericity of 70-99%; and/or

The modified PFA powder has a flowability of less than 30s/50 g.

22. The method of claim 21, wherein greater than 90% of the modified PFA powder has a sphericity of 70-99%; and/or

The flowability of the modified PFA powder is 10 to 25s/50 g.

23. The method of claim 22, wherein the particle size D50 of the modified PFA powder is 45-60 μ ι η; and/or

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

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

24. The method of any one of claims 14, 20, 21, 22, and 23, wherein the modified PFA powder has a purity of 95.5% to 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 μm.

25. The method of claim 24, 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 μm.

26. A modified PFA powder prepared by the process of any one of claims 14 to 25.

27. A non-stick coating prepared from a material comprising the modified PFA powder of any one of claims 1-13, 26.

28. A cookware, characterized in that it comprises a base and a non-stick coating formed on the base, said non-stick coating being the non-stick coating of claim 27.

29. A cooking appliance, characterized in that it comprises a pot according to claim 28.

30. The cooking appliance of claim 29, wherein the cooking appliance is a wok, a frying pan, an air fryer, a toaster, an electric cooker, an electric pressure cooker, or a soymilk maker.