WO2007068828A2

WO2007068828A2 - Process for manufacturing aluminium panels with improved corrosion resistance in aqueous media

Info

Publication number: WO2007068828A2
Application number: PCT/FR2006/002722
Authority: WO
Inventors: Laurent Poizat; Sandrine Dulac; Jean-Syvestre Safrany
Original assignee: Rubanox Chambery
Priority date: 2005-12-14
Filing date: 2006-12-13
Publication date: 2007-06-21
Also published as: EP1960153A2; WO2007068828A3; FR2894501B1; FR2894501A1

Abstract

The process for manufacturing aluminium panels comprises the surface preparation of two sheets made of aluminium alloy, the deposition on one of the sheets of an anti-weld ink in reserve zones corresponding to the circuit design, the bonding of the sheets to each other by rolling, and the expansion of the channels corresponding to the non-welded zones by means of a pressurized fluid. In this process, said ink comprises the following constituents: a) a mineral filler in the divided state, such as mica, a montmorillonite clay, talc, boron nitride, alumina or silica; b) an organic thickener (polymer); c) a corrosion resistance promoter in the form of a chemical adsorption or conversion agent (salt); d) a solvent comprising at least 50 wt.% water. The resulting panels have a high corrosion resistance without added graphite and can be used for making solar or heat-exchanging panels.

Description

Process for manufacturing aluminum panels with improved corrosion resistance in an aqueous medium.

Field of the invention

The invention relates to a method for manufacturing aluminum panels with an integrated circuit, generally known by the name of roll-bond, of the biface type with two deformed faces or of the single-sided type or OSF (one side flat) with a plane face and a deformed face. These panels are made from two sheets of aluminum or aluminum alloy, one of which is coated, on the areas to become the integrated circuit, an ink acting as an anti-welding material for prevent welding between the two sheets. The two sheets are then welded by bonding. The non-welded areas are then inflated hydraulically or pneumatically to form a circuit whose essential part is used as a heat exchanger, and especially as a cooling circuit of household refrigerators.

State of the art

The book "Aluminum", Volume 1 "Production - Properties - Alloys - Manufacture of semi-finished products - Auxiliary manufacturing", published by Editions Eyrolles, Paris 1964, pages 718 - 721, and the publication "Aluminum panels with integrated circuits: two complementary manufacturing lines for multiple products ", published in the Revue de l'Aluminum, February 1982, describe the principle of the roll-bond process for the manufacture of panels of two-sided type, and disclose the diagram of a line continuous manufacturing, as well as the alloys usually used for the manufacture of panels. In this continuous production line, the panels are formed from individual sheets (called "plates" in the book), which are transported manually or by mechanical conveying means through the various machines that make up the production line.

Patent FR 1347949 describes the principle of single-chip integrated circuit panels and proposes to make them from two sheets of different strength, one alloy 1100 and the other 1100 alloy with 0.12% zirconium addition . The patent FR 2561368 discloses a continuous manufacturing process of single-sided roll-bond panels from two sheets of aluminum or aluminum alloys.

Patent FR 1540436 discloses the preferential use of a mixture of graphite and potassium silicate as an anti-welding material.

The patent FR 2082814 discloses the use of a paste composed of zinc powder as an anti-welding material.

Patent FR 2270983 discloses the use of an anti-welding composition in aqueous medium comprising zinc nitride, bentonite, finely divided zinc.

Problems posed

The aluminum panels of the state of the art pose different types of problems:

- On the one hand, when the graphite is used in an anti-welding composition or an ink, it can occur corrosion, as indicated in the patent FR 2082814.

- On the other hand, when zinc is used to solve this problem of corrosion, it is possible to limit corrosion as long as zinc is present, zinc being a sacrificial material, so that its use is not suitable. when said panels are part of heat exchangers or facilities intended to have a long service life, and when the coolant is water-based, as for example in the case of heating installations using heat exchangers. heat, for example in the case of a solar heating installation. - In addition, there may be zinc particles, zinc not having ally surface aluminum, and these particles flowing with the heat transfer fluid of the circuit can cause erosion of the channels in the acute angles of the circuit.

- finally, it is important to have, both from the point of view of the cost of materials, and their implementation, a very economical process.

The object of the invention is to provide a method of manufacturing roll-bond panels, which uses an ink to solve the problems posed. Object of the invention

According to the invention, the method for manufacturing aluminum panels comprises the surface preparation of two aluminum alloy sheets, depositing on one of the sheets an anti-welding ink in reserved areas corresponding to the drawing of the circuit, the binding by rolling of the sheets on one another, and the inflation of the channels corresponding to the non-welded zones using a fluid under pressure. In this process, said ink comprises the following constituents: a) a mineral filler in the divided state, b) an organic thickening agent, c) a corrosion resistance promoter, d) a solvent comprising at least 50% of water by weight.

The inks according to the invention make it possible to solve the problems posed. Surprisingly, and as will be illustrated in the examples, the Applicant has found a very significant improvement in the corrosion resistance of the panels according to the invention, which has allowed to consider new uses for these panels.

Detailed description of the invention

According to the invention, the weight contents of said composition of said ink can be as follows: a) mineral filler: from 10 to 60% b) organic thickening agent: from 0.01% to 5% c) resistance promoter to the corrosion: from 0.05 to 5% d) solvent: complement to 100

Preferably, the weight content of said inorganic filler can range from 20% to 40%.

Preferably, the content of said organic thickening agent can range from 0.1% to 1%. Preferably, the content of the corrosion resistance promoter can range from 0.1% to 1%. Typically, said solvent may be water.

According to the invention, said weight content of organic thickening agent is chosen so as to have a viscosity, measured at 20 ° C, ranging from 5,000 centipoise to 100,000 centipoise, and preferably from 15,000 centipoise to 50,000 centipoise.

This viscosity range makes it possible to form said deposit on said sheet, said deposit being a spotted deposit typically formed by screen printing.

Said mineral filler can be a mineral filler in the divided state, with a maximum particle size of less than 500 μm, and preferably less than 100 μm, so that said ink can be applied by screen printing and said deposit is homogeneous. .

Said mineral filler may be a product with a laminated structure, for example mica, a phyllosilicate type clay such as, for example, montmorillonite, in the exfoliated state.

Said inorganic filler can also be an inert powder chosen from: talc, boron nitride, alumina, silica.

In addition, said inorganic filler can be a mixture of said laminated structure product and said inert powder.

According to the invention, said organic thickening agent may be chosen from organic polymers chosen from: anionic polymers, cationic polymers, polyethers and polyhydroxylated polymers, or mixtures of said organic polymers. Thus, said organic polymer may be an anionic polymer, typically a polyacrylate.

According to a variant of the invention, said corrosion resistance promoter may be an adsorption agent on said aluminum sheet chosen from the salts, typically of Na or K, of silicates, phosphates and phosphonates.

According to another variant of the invention, said corrosion resistance promoter may be a chemical conversion agent chosen from the salts of the elements. following chemicals: Cr, Ti, V, Zr, Co ₅ Ce, Mo, Hf and Mn, so as to form an oxide layer of said chemical element for implementing said method, and in particular during said rolling.

In addition, said corrosion resistance promoter may comprise a mixture of said absorption agent and said chemical conversion agent.

Advantageously, said corrosion resistance promoter is of the chromium-free type, because of the environmental problems related to the presence of chromium.

Another object of the invention is constituted by aluminum panels obtained by the process according to the invention.

In these panels, a so-called "outer" face of said panel may comprise a selective coating with maximum absorbance in the visible spectrum, and with minimal emittance in the infrared, at 100 ° C, so as to form to form a so-called solar panel ".

Another object of the invention is the use of such aluminum panels as heat exchangers in solar heating systems.

Examples of realization

A) The examples noted A to G were made by forming, by screen printing, said deposit on a so-called lower aluminum alloy strip 1050, from a series of inks denoted A to G, said deposit forming a plurality repetitive patterns, each pattern corresponding to the channels of a panel, then co-laminated at 400 ⁰ C said lower strip with a so-called upper aluminum alloy strip 1050, said upper band optionally comprising on its outer surface said coating selective. From the co-laminated web material, the web was then cut into web portions and the channels of each web portion were inflated with compressed air to obtain panels marked A a G. The inks A to G are aqueous inks of the following weight composition, the water forming the complement to 100, the inks E, F and G being according to the invention:

(*) Carbopol (Trademark) of the Noveon Company

B) Two corrosion tests were carried out on panels A to G: Test 1: the panel was immersed for 24 hours in a solution containing NH ₄ Cl at 53.5 g / l, NH ₄ NO ₃ at 20 g / l (NH-I) ₂ C ₄ H ₄ O ₆ at 1.8 g / l, H ₂ O ₂ (30% by volume) 10 ml / l.

Test 2: Each panel was circulated in the serpentine channel for 96 hours and at room temperature with the aid of a pump, and at a flow rate of 50. 1 / h, a commercially available solution. Antifrogen SOL (VP1981) from the company Clariant, in which copper nitrate at 1 .mu.g / l was introduced. At the end of these tests, a visual inspection of the channels was carried out in order to estimate the number of pits of corrosion and their depth and to a quotation with the following scale:

* excellent resistance to corrosion: 1

* good resistance to corrosion: 2

* poor corrosion resistance: 3

* very poor resistance to corrosion: 4

C) The results obtained are indicated in the following table:

D) Conclusions: panels E to G have good to excellent corrosion resistance. These tests show the decisive influence of the inks according to the invention.

Claims

claims

1. A method of manufacturing aluminum panels comprising the surface preparation of two sheets of aluminum alloy, the deposition on one of the sheets of an anti-welding ink in reserved areas corresponding to the circuit design, the connection by rolling the sheets together, and inflating the channels corresponding to the non-welded areas with a fluid under pressure, wherein said ink comprises the following constituents: a) a mineral filler at the divided state, b) an organic thickening agent, c) a corrosion resistance promoter, d) a solvent comprising at least 50% water by weight.

2. Method according to claim 1 wherein the weight contents of said composition of said ink are as follows: a) mineral filler: from 10 to 60% b) organic thickening agent: from 0.01% to 5% c) promoter corrosion resistance: 0.05 to 5% d) solvent: 100% supplement

3. The method of claim 2 wherein the weight content of said inorganic filler ranges from 20% to 40%.

4. Process according to any one of claims 2 to 3 wherein the content of said organic thickener is from 0.1% to 1%.

The method of any one of claims 2 to 4 wherein the content of corrosion resistance promoter is from 0.1% to 1%.

The process of any one of claims 1 to 5 wherein said solvent is water.

7. A process according to any one of claims 2 to 6 wherein said weight content of organic thickening agent is selected so as to have a viscosity, measured at 20 ⁰ C, ranging from 5,000 centipoise to 100,000 centipoise, and preferably from 000 centipoise to 50,000 centipoise.

The process according to any one of claims 1 to 7 wherein said inorganic filler is a mineral filler in the divided state, with a maximum particle size of less than 500 μm, and preferably less than 100 μm, so that said ink can be applied by screen printing and that said deposit is homogeneous.

9. Process according to any one of claims 1 to 8 wherein said inorganic filler is a product with a laminated structure, for example mica, a phyllosilicate clay such as, for example, montmorillonite, in the exfoliated state.

10. Process according to any one of claims 1 to 8 wherein said inorganic filler is an inert powder selected from: talc, boron nitride, alumina, silica.

The method of claims 9 and 10 wherein said inorganic filler is a mixture of said laminated structure product and said inert powder.

12. Process according to any one of claims 1 to 11 wherein said organic thickening agent is chosen from organic polymers chosen from: anionic polymers, cationic polymers, polyethers and polyhydroxylated polymers, or mixtures of said organic polymers.

The method of claim 12 wherein said organic polymer is an anionic polymer, typically a polyacrylate.

14. A method according to any one of claims 1 to 13 wherein said corrosion resistance promoter is an adsorbing agent on said aluminum sheet selected from salts, typically Na or K of silicates, phosphates and phosphonates.

The method of any one of claims 1 to 13 wherein said corrosion resistance promoter is a chemical conversion agent selected from the salts of the following chemical elements: Cr, Ti, V, Zr, Co, Ce, Mo, Hf and Mn, so as to form an oxide layer of said chemical element during the implementation of said method, and in particular during said rolling.

The method of claims 14 and 15 wherein said corrosion resistance promoter comprises a mixture of said absorption agent and said chemical conversion agent.

17. Aluminum panels obtained by the process according to any one of claims 1 to 16.

18. Panels according to claim 17 wherein an so-called "outer" face of said panel comprises a selective coating with maximum absorbance in the visible spectrum, and minimum emittance in the infrared, at 100 ° C, so as to form to form a panel called "solar".

19. Use of aluminum panels according to claim 18 as heat exchangers in solar heating systems.