WO2007085062A1

WO2007085062A1 - Production of perforated aluminium (in the form of sheet or foil) hard- or soft-rolled

Info

Publication number: WO2007085062A1
Application number: PCT/BA2007/000002
Authority: WO
Inventors: Zijad Cehic
Original assignee: Zijad Cehic
Priority date: 2006-01-27
Filing date: 2007-01-25
Publication date: 2007-08-02

Abstract

Perforated aluminium foil or sheet is produced electrochemically, so that the size of pores can be controlled by applying specific voltage on electrodes. In the presented technological process, the pore size ranges from 0.3 to 1.5 µ with stochastic distribution. The essence of the invention lies in the composition of electrolyte (HNO3 in pH=3-4 concentration) and in maintaining the concentration and voltage (12-13V) throughout the process. The anode is aluminium and cathode a chrome steel net. Perforated foil can be used in food industry for packaging.

Description

Zijad Cehic

Trnovska 7, 71000 Sarajevo, Bosna i Hercegovina

Production of perforated aluminium (in the form of sheet or foil) hard- or soft-rolled

Field of technology the invention refers to

The invention refers to aluminium foils or sheets that are perforated and can be classified as aluminium foil or sheet.

Technical problem

The technological problem arises as to how to perforate a finished aluminium foil or sheet, i.e. which procedure to use in order to perform the perforation in order to obtain a product that could be used in e.g. food industry for packaging.

State of art

The inventor is not aware of any technological solutions for the problem of foil or sheet perforation that are similar to the invention presented here.

Presentation of the essence of the invention

The production is based on electrochemical procedure, whereby micro-holes are being generate on the anode, which consists of aluminium, in the electrolyte (HNO₃ solution inpH=3-4 concentration), with the 12V-13V direct current voltage. The cathode is made of chrome steel net.

Short description of drawings

The accompanying drawings, i.e. pictures included in the description, which make up part of the inovation description, ilustrated the best way of invention execution presently discussed, and help to explain the basic principles of the invention.

Figure 1 - Represents the technological scheme of aluminium foil perforation, with the following characteristics or elements:

1. imperforated aluminium roll, 2. tub with electrodes and electrolyte, where teh perforation is performed, 3. tub for neutralization, 4. rinsing tub, 5. perforated aluminium roll.

Figure 2 - Represents the technological scheme of aluminium sheet production in a tub with electrodes.

Detailed description of the invention AI-foil perforation

Rolled Al-foil, 20 μ (μ = 0,001mm) thick and 1000mm wide is bought from a foil manufacturer (roll weight depends on the length). From the roll, Al-foil is drawn into the tub, with the known electrolyte, beneath the cathode, over the isolator distancer (the distance between anode and cathode is 15- 20mm), and with the known direct current voltage is kept for 15 minutes. It is then drawn into the second tub, where it is neutralized in NaOH solution with pH=8. Thus neutralized perforated aluminium foil is taken out of the second tub and placed into the third tub, where it is rinsed with 0.2-0.5 D⁰ water. The wet perforated aluminium foil, that has passed through these three tubs, is rolled. The current circle is then stopped and the roll is dried, i.e. it is unrolled and passed through a tunnel heated to 200 C, after which it is packed.

The perforation process is continuous, as shown on Figure 1.

Electrolyte concentration must be continually monitored, and the pH=3-4 value maintained by dozing the fresh electrolyte.

Following tub dimensions are needed for the production of 36 pieces of perforated foil (dimensions 8m x 0.33m):

-tub with electrodes and electrolyte: 28m x 1.4m x 0.80m,

-tub for neutralization: 5m x 1.4m x 0.80m,

-tub for rinsing: 3m x 1.4m x 0.80m.

The cathode consists of a 24m x Im chrome steel net, with 0.6mm x 0.6mm holes. Energy consumption: 5KW/hour for 36 foils.

Chemicals consumption: 20 litres OfHNO₃ in 62% concentration for electrolyte

5 litres NaOH 45% for neutralization 2000 litres softened water/hour for rinsing.

Following storage tanks are needed for hourly production of 36 pieces of perforated foil:

- for HNO₃ of 62% concentration cca 5m³,

- for NaON of 45% concentration cca 2m³,

- for electrolyte preparation, two 30m³ tanks,

- for NaOH preparation two 20m³ tanks,

- for waste water treatment, three pools with dimensions 10m x 7m x 2.5m.

Aluminium sheet perforation

The perforated aluminium sheet (2m x Im) production requires a tub with dimensions 2.5m x 1.4m x 0.5m.

The tub contains the already described electrolyte, where an aluminium bar as anode and a 2m x Im chrome steel net are vertically soaked. The distance between the electrodes is 15mm.

The perforation of lmm thick sheet requires a 13.5 hour-long electrochemical process, with permanent electrolyte dozing and maintaining the required pH. The current is then turned off, and the neutralization with ph=8 NaOH is done. The sheet is then rinsed with softened water and taken out of the tub.

The process is discontinued, as presented in the scheme no.2.

Energy consumption per a sheet bar with dimensions 2m x Im x lmm is 5.2KW.

Chemicals consumption: for electrolyte, 15 litres OfHNO₃ 62% for neutralization, 2 litres of NaOH 45% for rinsing, 3m³ softened water.

Claims

Zijad CehicTmovska 7, 71000 Sarajevo, Bosna i HercegovinaProduction of perforated aluminium (in the form of sheet or foil) hard- or soft-rolledPATENT CLAIMS

1. This invention claims protection of the sequence of technological operations for production of perforated aluminium (in the form of sheet or foil) hard- or soft-rolled, characterized by the composition of electrolytes (HNO₃ in pH=3-4 concentration), by defined voltage (12V — 13 V of direct current) and cathode type (chrome steel net).