Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/02—Inorganic compounds ; Elemental compounds
• • 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
  • B41N3/038—Treatment with a chromium compound, a silicon compound, a phophorus compound or a compound of a metal of group IVB; Hydrophilic coatings obtained by hydrolysis of organometallic compounds
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
  • C23G1/22—Light metals

Definitions

• the invention relates to a method of conditioning the surface of a work piece, in particular of a litho-strip or litho-sheet, consisting of an aluminium alloy.
• the above mentioned object is solved by a method of conditioning the surface of an aluminium work piece consisting of an aluminium alloy, which method comprises at least the step of degreasing the surface of the work piece with a degreasing medium, wherein the aqueous degreasing medium contains at least 1,5 to 3 % by weight of a composite of 5 - 40 % sodium tripolyphosphate, 3 - 10 % sodium gluconate, 3 - 8 % of a composite of non- ionic and anionic surfactants and optionally 0,5 % to 70 % soda, preferably 30 - 70 % soda, wherein sodium hydroxide is added to the aqueous degreasing medium such that the concentration of sodium hydroxide in the aqueous degreasing medium is 0,01 to 5 % by weight, preferably 0,1 to 1,5 % by weight, more preferably 1 to 2,5 % by weight .
• the combination of the use of the degreasing medium together with added sodium hydroxide ensures an increased manufacturing speed during surface roughening including electro-chemical graining with sufficient results despite of the fact that oxide particles are not removed completely during degreasing.
• the reason for the good results is seen in the fact that due to the addition of sodium hydroxide the degreasing medium has an increased pickling rate which removes more aluminium from the surface at the same time.
• the electro-chemical graining process of litho-strips can be done with a lower charge entry therefore enabling a higher manufacturing speed.
• the addition of 0,1 % to 1,5 % by weight sodium hydroxide is suitable even for lower manufacturing speeds during degreasing, with the addition of 1 % to 2,5 % by weight sodium hydroxide highest manufacturing speeds during degreasing are achievable ensuring at the same time high manufacturing speeds during plate manufacturing, i.e. during electrochemical graining.
• the optional addition of soda in an amount of 0,5 - 70 %, preferably 30 to 70 % by weight allows to control pH-value of the degreasing medium.
• the time of application of the degreasing medium to the surface of the aluminium work piece is at maximum 1 to 7 s, preferably at maximum 2 to 5 s . These application times ensure high production speeds at the same time ensuring that the oxide islands can easily be removed by surface roughening .
• the temperature of the degreasing medium is 50 to 85 0 C, preferably 65 0 C to 75 0 C.
• the pH-value of the aqueous degreasing medium is from 10 to 14, preferably 10 to 13,5.
• the work piece is a strip or a sheet, in particular a litho-strip or a litho-sheet.
• the necessary electrochemical graining process for manufacturing litho-strips or litho-sheets can be accomplished thoroughly within less time and the printing plate manufacturing speed can be increased. Furthermore, the charge entry needed can be reduced while providing a fully grained strip or sheet surface .
• the inventive conditioning method is accomplished subsequent the manufacturing of a strip, in particular a litho-strip, and the conditioned strip is reeled on a coil.
• a coil of a conditioned litho-strip can be provided comprising an optimum performance in further surface roughening processes used to manufacture lithographic printing plates.
• the above mentioned object is solved by a work piece consisting of an aluminium alloy conditioned by the inventive method.
• the inventive work piece provides a cleaned surface with an optimum performance for a subsequent electro-chemical graining process .
• the work piece is a strip or a sheet, in particular a litho-strip or a litho-sheet.
• Litho-strip or sheets are produced for lithographic printing plates and differ from "normal" sheets due to the aluminium alloy they consist of and their specific thickness, which is typically less than 1 mm, preferably 0,14 to 0,5 mm, more preferably 0,25 to 0,3 mm.
• the surface of litho-strips and sheets has to be prepared for a roughening process, since manufacturing of lithographic printing plates generally comprises an electro-chemical graining process to prepare the surface of the lithographic printing plates for the printing process.
• inventive sheets or strips in particular with the inventive litho-sheets or litho-strips, the necessary electro-chemical graining of the surface can be accomplished in shorter time with a reduced charge entry.
• the mechanical features and an improved graining structure during electro-chemical graining can be provided if the aluminium alloy of the work piece is one of the aluminium alloys AA1050, AAIlOO, AA3103 or AlMgO, 5.
• the aluminium alloys provide the mechanical strength needed for lithographic printing plates while enabling due to the low amount of alloying constituents a homogeneous graining of the surface.
• work pieces consisting of other aluminium alloys may provide the same advantages.
• impurities each less than 0,005% in sum max. 0, 15 %, rest Al.
• Work pieces consisting of one of the three aluminium alloys and conditioned with the inventive method have state of the art mechanical and graining properties, in particular if the work pieces are litho-strips which are grained electro-chemically after conditioning. It was surprisingly observed that in particular the latter aluminium alloys conditioned with the inventive conditioning method show a higher sensitivity in subsequent surface roughening processes. As a result despite of the inventive single step conditioning method, which reduces the expenses for the conditioning equipment significantly, an increase in plate manufacturing speed for litho-strips and sheets is achievable.
• Fig. 1 a microscopic view of the surface of a litho-strip degreased conventionally and Fig. 2 a microscopic view of the surface of a litho-strip degreased with the inventive method.
• the different aluminium alloys have the following compositions of alloying constituents in weight percent:
• impurities each less than 0,005 % in sum max. 0, 15 %, rest Al.
• Litho-strips made from the aluminium alloys mentioned above where tested with regard to their graining behaviour on industrial plate manufacturing lines.
• the degreasing medium used contains at least 1,5 to 3 % by weight of a composite of 5 to 40 % sodium tripolyphosphate, 3 to 10 % sodium gluconate, 30 to 70 % soda and 3 to 8 % of a composite of non-ionic and anionic surfactants, with an addition of sodium hydroxide in the amount of 1 % by weight.
• the comparative examples were degreased with the same conditions without the addition of sodium hydroxide to the degreasing medium. The results of the examples are shown in table 1
• the litho-strips degreased with the inventive method generally show a good appearance after electro-chemical graining even if the graining velocity was increased.
• litho-strips degreased with the inventive method show even better graining results, because the surface of the litho-strip grained with the inventive method have a finer, more homogeneous and more shallow graining structure.
• This graining structure provides improved printing characteristics of the inventive litho-strips.
• the inventive method provides said improved graining structure even at higher manufacturing speeds, as can be derived from the results of strip 1 and strip 2.
• Strip 1 degreased conventionally shows merely good appearance results after electro-chemical graining at a graining velocity of 50 m/min.
• strip 2 degreased with the inventive method allows 55 m/min graining velocity.
• Fig. 1 and Fig. 2 show, as already mentioned, a microscopic view of the surface of a litho-strip consisting of the aluminium alloy A degreased with the inventive method after electro-chemical graining.
• Fig. 1 shows the graining result of the same litho-strip degreased conventionally.
• the graining pattern achieved with the inventive method is finer and more shallow compared to the graining pattern achieved with a conventionally degreased litho-strip. As a result, the printing characteristics of the inventive litho-strips are improved significantly.
• the present embodiments of the invention has been achieved by the addition of 1 % per weight sodium hydroxide. It is expected that a higher concentration of sodium hydroxide combined with an decreased contact time of the strip with the degreasing medium will lead to similar results.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• General Chemical & Material Sciences (AREA)
• Metallurgy (AREA)
• Inorganic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Wood Science & Technology (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Printing Plates And Materials Therefor (AREA)
• Cleaning By Liquid Or Steam (AREA)

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Citations (11)

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• 2007
  • 2007-06-06 CN CN200780020973.XA patent/CN101460313B/zh active Active
  • 2007-06-06 EP EP07729960A patent/EP2024190B9/en active Active
  • 2007-06-06 JP JP2009513693A patent/JP5001359B2/ja active Active
  • 2007-06-06 WO PCT/EP2007/055586 patent/WO2007141300A1/en not_active Ceased
  • 2007-06-06 CN CN201410143321.7A patent/CN103924252B/zh active Active
  • 2007-06-06 ES ES12157831.4T patent/ES2528027T3/es active Active
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  • 2007-06-06 EP EP12157831.4A patent/EP2468525B1/en active Active
• 2012
  • 2012-09-14 US US13/617,552 patent/US8449689B2/en active Active

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