Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N3/00—Preparing for use and conserving printing surfaces
  • B41N3/08—Damping; Neutralising or similar differentiation treatments for lithographic printing formes; Gumming or finishing solutions, fountain solutions, correction or deletion fluids, or on-press development
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N3/00—Preparing for use and conserving printing surfaces
  • B41N3/03—Chemical or electrical pretreatment
  • B41N3/034—Chemical or electrical pretreatment characterised by the electrochemical treatment of the aluminum support, e.g. anodisation, electro-graining; Sealing of the anodised layer; Treatment of the anodic layer with inorganic compounds; Colouring of the anodic layer
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F3/00—Electrolytic etching or polishing
  • C25F3/02—Etching
  • C25F3/04—Etching of light metals

Definitions

• the present invention relates to improvements in the process of electrograining (electroetching) aluminium.
• Aluminium is commonly used for the production of lithographic printing plates. For this purpose it is desirable that it should have a roughened surface characterised by the presence of very fine pits.
• hydrochloric acid electrolyte generally incorporates 2-20 gms hydrochloric acid per litre.
• the preparation of aluminium for use in lithographic printing comprises a three-stage process involving degreasing and pretreatment (usually etching in sodium hydroxide-based solutions) followed by electrograining and anodising.
• electrograining is conventionally carried out by applying alternating current to the aluminium whilst immersed in dilute aqueous hydrochloric acid. Since it is economically necessary to wash the aluminium in normal tap water (deionised water being too expensive for wash purposes) after the pretreatment stages, it is inevitable that the electrograining electrolyte will become progressively contaminated by whatever ions may be present in the wash water, carried over on the surface of the aluminium. Most natural waters contain more than parts per million sulphate ion.
• a very suitable concentration of orthophosphoric acid is 5 l0 gms/litre.
• EXAMPLE 1 A hydrochloric acid, containing 6 gms hydrochloric acid per litre, electrolyte was made up with deionised water 1 litre) and 5 gms orthophosphoric acid per litre was added.
• EXAMPLE 2 A 8 gms per litre hydrochloric acid electrolyte was made up, using tap water containing about ppm. of sulphate ion, and 8 gms per litre phosphoric acid was added. When panels of 99.7 percent aluminium were processed under the same conditions as Example 1, a finely pitted surface with pits ranging from l-5 microns in diameter were produced. A similar electrolyte was then made up without the addition of phosphoric acid and this produced a relatively irregular and coarsely pitted surface with pit sizes ranging from about 10 to 30 microns.
• EXAMPLE 3 Trials were carried out in a 50-gallon tank containing 8 gms/litre hydrochloric acid electrolyte made up with tap water containing about 100 ppm. of sulphate ion.
• a 99.7 percent aluminium sheet 480 mm X mm (19 in. X 5 in.) electrograined at room temperature at a constant current of amps (about 200 amps/sq. ft. at the treated face of the panel) with the applied ac. voltage rising from 10 to 12 volts over the 2-minute electrograining period, produced a surface with pits up to 20 by 30 microns in size.
• both electrodes may be formed of aluminium plates to be electrograined.
• the process may also be carried out on a continuous scale.
• a continuous strip of aluminium is drawn through a two-compartment cell, in each of which is a counterelectrode connected to an a.c. source, so that current flows between the counterelectrodes through the aluminium strip which is passed through an aperture in the partition between the two compartments and through the electrolyte between the electrodes and the adjacent portion of the strip.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Printing Plates And Materials Therefor (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=25667281

Family Applications (1)

Country Status (9)

Cited By (32)

Families Citing this family (2)

Citations (3)

• 1971
  • 1971-07-09 GB GB3243871A patent/GB1392191A/en not_active Expired
• 1973
  • 1973-05-24 CA CA172,192A patent/CA1009606A/en not_active Expired
  • 1973-05-25 SE SE7307392A patent/SE381683B/sv unknown
  • 1973-05-30 DE DE2327764A patent/DE2327764B2/de not_active Ceased
  • 1973-06-06 NL NL7307879A patent/NL7307879A/xx not_active Application Discontinuation
  • 1973-06-19 BE BE132431A patent/BE801114A/xx unknown
  • 1973-06-21 CH CH906273A patent/CH566401A5/xx not_active IP Right Cessation
  • 1973-07-09 FR FR7325067A patent/FR2237438A5/fr not_active Expired
  • 1973-09-27 US US401257A patent/US3887447A/en not_active Expired - Lifetime

Patent Citations (3)

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