KR880000640B1 - One-step cooting precess of p.t.f.e.resin aluminium plate - Google Patents

Abstract

According to the method, an aluminium plate whose surface is given an etching treatment to have a uniform distribution of pits is turned at 100-150 rpm to be applied with PTFE resin which drops for 3-6 seconds in a spin-flow coating method. The coated plate is dried for the final process. The composition of the aluminium plate comprises 0.1 wt.% Si, 0.5-0.6 wt.% Fe, 0.1 wt.% Cr, 0.901.00 wt.% Mn, 0.65-1.00 wt.% Mg, 0.07 wt.% Zn, 97.68-97.13 wt.% Al.

Description

One-step coating method of P.T.F.E. (Polytetrafluoroethylene) resin on aluminum plate

1 is a cross-sectional view of an aluminum sheet in which the P.T.F.E.resin is coated with one step after the aluminum material is corroded to form a uniform pit.

FIG. 2 is a cross-sectional view of a conventional aluminum sheet coated with a two-stage after obtaining the surface roughness by sandblasting as a physical method.

3 is one embodiment of a spin flow coating apparatus for coating the inner cylinder of the electronic rice cake in the present invention.

4 is an aging characteristic diagram of an HCl solution which is a chemical corrosion solution in the present invention.

5 to 7 are photographs and data showing the corrosion state in the present invention.

The present invention relates to a method for one-step coating of a PTFE resin on an aluminum sheet, and more particularly, to corrode the surface of the aluminum sheet to obtain an anchor effect, and to coat the PTFE resin with a one-step using a spinflow coating method. It is about a method.

The present invention is a one-step coating of PTFE resin on an aluminum plate as part of obtaining excellent properties of corrosion resistance, heat resistance, abrasion resistance, and non-adhesiveness, compared to the inner container of 1100 pure aluminum thermal insulation container without the PTFE (polytetrafluoroethylene) coating. In order to increase the adhesion between the PTFE resin and the aluminum plate, the conventional deep draw method is obtained by anchoring the surface of the aluminum plate using chemical and electrolytic corrosion methods and then coating the PTFE resin thereon. Adopted one-step coating method that has better adhesion than tous tap or three-tap coating method used for frying pan or thick aluminum material, which is not used, and the coating is spin-flow coatin method for uniform adhesion. One coat is coated, hot air dried and 10 minutes at 380 ℃ -400 ℃ After the water-cooling the plate material through a deep draw process Ying was the outer surface produces a thermally insulating inner craw for processing anode oxidation film.

In addition, by developing an alloy containing about 0.90-1.00 of manganese and about 0.65-0.75wt% of magnesium in a conventional 1100 pure aluminum material, it has increased the strength of pure aluminum while purifying grains. By reducing the thickness of 1.5-2.0mm used to 1.2mm, the material cost can be saved more than 20%.

Since the one-step P.T.F.E.coating technology of the present invention is a new technology applied for the first time to the aluminum material of the inner container, there is no similar conventional technology. However, in the case of a frying pan or a thick aluminum material that is not intended for deep-drawing, sandblasting the surface of the conventional material to give irregularities to the surface, and coating the PTFE resin directly has poor adhesion, so using a two-step using a primer Products are produced by coating primer → PTFE coating) or three taps (primer → PTFE coating → PTFE coating or PTFE coating containing metal powder). When the conventional method of sandblasting and coating a two-step or three-tab is applied to the P.T.F.E.Sutity coating of the inner container, the fundamental difference is as follows.

First, when the aluminum material of the inner bowl is deep drawn and sandblasted to coat by conventional two-step or three-tab method, the PTFE resin is sprayed onto the surface by the spraying method, and the PTFE is coated. Since the resin must be fired, the inner bowl is warped at this temperature due to the residual processing stress during deep drawing, causing a poor adhesion between the inner cylinder and the hot plate, resulting in a fire due to overheating. there was.

In addition, in the conventional sandblasted surface roughening method, in this case, the adhesion between the base and the coating layer is not excellent (see FIG. 2), which has a fatal effect on the durability, and the coating layer is peeled off, resulting in poor medical conditions. There was a serious flaw.

Second, similar to the patent application method, when the inner plate is coated with two- or three-tab before deep drawing, the distortion caused by the method of deep drawing after firing the coating member described in the first part is compensated for. When deflecting coated plate, large section shrinkage of material causes cracking or splatter of coating layer using primer and defects in penetration as well as foreign matter penetrates into crack gap during use. Due to the significant defects such as peeling off the coating layer was not actually used.

In addition, when the surface roughness is obtained by a sand blast by a conventional physical method, the cross section is shown as shown in FIG. 2, and a defect is caused by the stress field in the plane deformation state caused by the punch head during deep drawing. There was this.

In addition, as a material for the inner container of the thermal insulation container, 1100, 3003, 3004, etc., which are aluminum alloys for non-heat treatment and work hardening, are known. It is an alloy that is easy to cause poor contact with the hot plate and increases strength and corrosion resistance than 1100. 3003 alloy containing about 1.2% Mn and about 300% alloy containing about 1.2% Mn is added. However, 3003 has a lower strength than 3004, and the 3004 alloy has a drawability when drawn due to smaller elongation than 3003 or 1100.

In addition, in the 380-400 ℃ area, which is the temperature range during firing of the coated sheet, the annealing temperature is 413 ° C in the case of 3003 alloy, so that it is not possible to obtain the effect of complete annealing, and in the case of 3004 alloy, The annealing temperature was 345 ° C, which resulted in over anealing, which resulted in the growth of orange peel on the outer wall due to grain growth.

In addition, the conventional coating method, there is a spray method or a deposition method, but these coating methods are not uniform, the coating layer is made of a lot of processing, so there is a defect that causes poor adhesion when making the inner tube by deep drawing the original plate.

The present inventors have completed the present invention as a result of extensive research in order to eliminate the above-mentioned drawbacks.

The working process in this invention is as follows,

The one-step P.T.F.E.coating process and the firing process of the aluminum alloy material, the corrosion process, the spinflow coating method, which are the core technical contents in the manufacturing method of the present invention, will be described in detail.

1. Aluminum alloy material

The material required for the inner barrel of rice bowl is first, it must have strength enough to be easily deformed in small impact and not to cause poor contact with the hot plate, and secondly, it is corroded to aluminum material to have sufficient adhesion and adhesive strength when coated with PTFE. The treatment should have good anchoring effects as shown in FIG.

In other words, the anchor effect means that the inlet is small when PTFE liquid is pretreated and applied to the metal surface having roughness, and the pit is uniformly formed to widen as it enters. This is to prevent the peeling off.

In general, when Mn.Mg.Si.Fe is added to a known Al, the particles become finer, especially when Mn is contained, thereby increasing strength by strengthening dispersion, and Mg acts as an additional factor to the effect of Mn. .

In view of the above, the inventors of the present invention used the alloy containing Mn of 0.90-1.00% Mg and 0.65-0.75% of Mn in order to obtain strength problems, annealing treatment and fine drawing products suitable for the firing temperature range. At the same time, the aluminum plate was developed to reduce the material cost by more than 20% by reducing the thickness of the aluminum plate to 1.2 mm by increasing the strength.

A detailed component analysis table is as follows.

TABLE 1

Component Analysis Table (Analysis at Korea Research Institute of Chemical Technology)

2. Corrosion process

The surface roughness of the metal substrate is an important factor in order to obtain good adhesion when coating the PTFE resin on the metal substrate, and this method is obtained when the surface roughness by sand blast is obtained by conventional physical methods. As shown in FIG. 2, the cross section is shown. In this method, the punch head receives a stress field in a plane deformation state, and thus the coating part is peeled off.

In order to solve such a conventional defect, the present inventors have conducted extensive research to obtain an anchor effect by a chemical or electrolytic corrosion method, which is a novel method for aluminum plate, which is a metal material, and will be described in detail below.

The chemical corrosion method has obtained good results from 1100 pure aluminum and the aluminum alloy material adopted in the present invention, but it is difficult to manage the electrolyte solution and to set the working conditions due to the short life of the electrolyte solution.

On the other hand, the electrolytic corrosion method can be applied to all kinds of alloys and the cost of facility investment, while the uniformity of the work and the corrosion can be done in a short time and the problem of aging of the electrolyte is more advantageous than the chemical corrosion method.

During electrolytic corrosion, the surface roughness depends on the pattern and depth of the pit. The shape of the pit should be evenly distributed, and the proper roughness must be uniformly formed to show excellent adhesion.

Chemical corrosion and electrolytic corrosion are common methods of generating a formula, which is a corrosion process that locally develops pits on the surface of a metal and is a phenomenon that is common to both. Anion is adsorbed in this area with different electrical distribution on the back surface, so that local anion is adsorbed on this site, and the anion is concentrated inside the pit formed once, and as a result, metal ion is hydrolyzed to make acidic solution. The growth of the pit proceeds in the depth direction, thereby forming a pit that is small and wider in the inlet on the metal surface.

In the case of pure aluminum, pit formation is unevenly distributed along with surface corrosion in acidic solution.

Therefore, the present patent uses aluminum alloys containing 0.9% -1.0% and 0.65% -1.0% of Mn and Mg, respectively, to make uniform precipitates on the surface to facilitate the formation of pits and to uniformly distribute them. Corrosion in the Cl ^- can generate pits as imposing, SO ₄ ^-2 or more feed voltage potential generated by the negative ion solution Chengdu ^forced-man while the feet caused by the ion potential in the former pirate corrosion Cl ^- NO ₃ ions in addition to . The most sensitive to the formula is Cl ^- ions, the characteristic of the pit by Cl ^- ions is wide and deep inlet, the characteristic of the pit by NO ₃ ^- ions is very narrow and shallow in depth, SO ₄ ^-2 The pit entrance is very wide and the depth is very shallow. Therefore, the electrolytic corrosion method can control the shape of the pit by adjusting the composition of the solution.

In addition, since the pits are formed only by Cl ions in the chemical corrosion method, the distribution and size of the pits can be controlled by controlling the composition of the solution, temperature, corrosion time, additives, and alloying elements of the material.

[2-1 Chemical Corrosion Method]

The chemical corrosion solution was selected as HCl solution by citing that Cl ^- ion is very reactive with aluminum and acts as an autocatalytic and self-catalyzed catalyst for the formation and growth of fittings. Aging was determined, and the effects of HCl solution concentration, temperature, corrosion time and additives were investigated. Corrosion surface determinations were compared by cross-sectional photographs and roughness tests.

(1) HCl solution aging characteristics (see attached drawing 4)

(2) concentration of electrolyte

The change in concentration was investigated in the range of 3-20%. As the concentration increased, the reaction on the surface became violent, but it did not affect the depth of corrosion significantly. Even at high concentrations of 10% or more, the reaction occurred too much. The best effect of the solution in the range of 5-10% on the corrosion effect.

(3) HCl electrolyte temperature

Corrosion of aluminum is greatly affected by the temperature of HCl solution. In general, the reaction does not occur vigorously below 50 ° C and starts vigorously at temperatures above 70 ° C.

In the present invention, the temperature range of the solution in the experiment was the best range of 75 ℃-80 ℃.

(4) corrosion time

Corrosion time depends on the change in concentration and temperature, and shorter at high and high temperatures, and longer at low and low temperatures. The corrosion time of 5% HCl solution at 80 ℃ is 3-4 minutes.

(5) additive

The addition of CH ₃ COOH, HNO ₃ , FeCl ₃ , NaCl, H ₃ PO ₄ to a 5% HCl solution showed slightly better corrosion effects when saturated salts of FeCl ₃ , NaCl or Cl ^- ions were added. .

[2-2 Electrolytic Corrosion Method]

(1) degreasing

The surface is activated by degreasing for 0.5-2 minutes at 40-70 ° C. in 10-20% sulfuric acid solution. Excessive degreasing increases the active surface, which intensifies the corrosion, making it difficult to obtain desirable roughening and beautiful color, and when degreasing is insufficient, corrosion occurs locally.

(2) Electrolytic Corrosion

Corrosion is performed using a DC power source in a mixed electrolyte of 0.5-3% nitric acid and 0.5-1.5% hydrochloric acid.

The nitric acid concentration is in the range of 0.5-3%, but below 0.5% and above 3%, dissolution of aluminum is suppressed, so that uniform roughness cannot be obtained.

The effect of hydrochloric acid is deeper in pit than in nitric acid, its diameter is large, and its distribution is non-uniform, so that the surface roughness increases with increasing amount. The current density is 20 A / dm 2 or more, and the optimum adjustment is 60-100 A / dm 2, with little effect on the current density and the pit pattern or distribution.

The electrolysis time is determined by the surface roughness with respect to the current density.

Electrolysis temperature is 15-30 degreeC.

(3) Smut removal

In order to remove the smut generated during electrolytic corrosion, the smurt is removed by immersion for 5-10 minutes in 40% nitric acid solution.

Table of characteristics of chemical and electrolytic corrosion methods.

3. Coating process

As a P.T.F.E coating method on the inner surface of kitchen utensils, a technique that has been mainly used conventionally is a spray method or a deposition method. These coating methods have a defect in that the coating layer is not uniform and the coating layer has many pores, which results in poor adhesion due to deep drawing or expansion of pores remaining during use, or poor durability due to foreign matter penetration. .

In particular, P.T.F.E. Because about 60% of the loss was lost, the recovery was bad. Accordingly, the present inventors have developed and applied the "spinflow coating method", which is a method of coating by centrifugal force in view of the above points, to equalize the thickness of the coating layer, reduce porosity, and improve the P.T.F.E. The recovery rate of the stock solution was increased.

According to the spin flow method of the present invention, there is no uniformity and no pores, so there is no poor adhesion during deep drawing, and the PTFE raw liquid flowing out of the plate by centrifugal force of the disc wheel in the spin flow machine is moved to a facility as shown in FIG. About 90% recovery is possible.

Spin flow machine is shown in Figure 3, and can be applied anywhere in the coating of the plate-like material, in particular, the most suitable method for coating the inner container of the electronic container.

This method is based on the centrifugal force of P.T.F.E. The coating is spread by uniformly spreading the stock solution, which is advantageous in that there are no pores, the film thickness can be arbitrarily adjusted, and a uniform coating can be obtained.

As a technique for coating the inner container of the electric container, adjust the original plate of FIG. 3 to 100-150 RPM and drop the predetermined amount of PTFE stock onto the disc-shaped Al plate, hold it for 3-6 seconds, and then stop the plate. A uniform coating thickness can be obtained, and the recovery rate of the PTFE stock solution is about 90% or more superior to that of the spraying method, and an excellent coating layer which does not cause poor adhesion during deep drawing can be obtained.

4. Firing process

P.T.F.E. P.T.F.E.resin transitions from monomo to polymer by coating with one-step and then removing moisture by hot air drying and firing at 380 ° C-400 ° C.

P.T.F.E. In order to sinter the resin, a heat treatment furnace having a uniform temperature distribution should be used. Examples of heat treatment include an electric furnace, a gas furnace, and a far infrared furnace. In particular, electric furnaces, gas furnaces P.T.F.E. Since the atmosphere must be raised to a predetermined temperature in order to use for plastic firing, there are disadvantages in that a lot of power costs, material costs, and the working environment are bad.

Far-infrared heating was used to compensate for this drawback.

Far-infrared ray has a wavelength of 3-400 μm, and its transmittance is larger than that of visible light, and it has thermal action or fluorescent action.

In addition, since the heat transfer method transfers heat to the heating target material by radiation, heat absorption is easy and heat efficiency is excellent.

For example, using a far-infrared planar heater with a wavelength of 3-50 µm, P.T.F.E. By firing the resin, the work environment was improved, thermal efficiency was increased, and power cost was reduced.

Claims (5)

The surface of the aluminum sheet is corroded to form a uniformly distributed pit, and the one-step coating is performed by spin-flow coating method of dropping PTFE resin for 3-6 seconds while rotating the corroded sheet at 100-150 rpm. One-step coating method of PTFE resin on aluminum plate which consists of baking. The composition of claim 1, wherein the composition of the aluminum sheet is Si = 0.1wt%, Fe: 0.5-0.6wt%, Cr: 0.1wt%, Mn: 0.90-1.00wt%, Mg: 0.65-1.00wt%, Zn,: One-step coating method of PTFE resin on aluminum sheet of 0.07wt%, Al: 97.68-97.13wt%. The method of one-step coating of P.T.F.E.resin on an aluminum sheet according to claim 1, wherein the corrosion is a chemical corrosion which is treated for 3-10 minutes at a temperature of 60-80 ° C in a 3-10% hydrochloric acid solution. The aluminum sheet according to claim 1, wherein the corrosion is an electrolytic corrosion treatment in a mixed electrolyte solution of 0.5-3% nitric acid and 0.5-1.5% hydrochloric acid at a current density of 20 A / dm 2 and a temperature of 15-30 ° C. for 0.5-2 minutes. One step coating method of PTFE resin. The method of one-step coating of P.T.F.E.resin on an aluminum sheet according to claim 1, wherein the firing is far-infrared firing which is processed at a temperature of 380-400 ° C. for 10-15 minutes using a wavelength of 3-5 µm.

Images