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
  • B41N3/03—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
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/20—Electrolytic after-treatment
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/24—Chemical after-treatment
  • C25D11/246—Chemical after-treatment for sealing layers

Definitions

• the invention relates to an aftertreatment process for roughened and anodically oxidized aluminum, in particular of support materials for offset printing plates with aqueous solutions containing alkali silicate.
• Carrier materials for offset printing plates are provided either by the consumer directly or by the manufacturer of precoated printing plates on one or both sides with a radiation-sensitive layer (reproduction layer), with the aid of which a printing image of a template is generated by photomechanical means.
• the layer support carries the image points which will guide the color during later printing and at the same time forms the hydrophilic background for the lithographic printing process at the non-image points (non-image points) during later printing.
• Aluminum, steel, copper, brass or zinc, but also plastic films or paper can be used as the base material for such layers. These raw materials are processed by suitable operations such as. B. grain, matt chrome plating, surface oxidation and / or application of an intermediate layer in layer support for offset printing plates.
• the carrier materials are often ins Special anodically oxidized carrier materials based on aluminum, to improve the layer adhesion, to increase the hydrophilicity and / or to facilitate the developability of the photosensitive layers, are subjected to a further treatment step before the application of a photosensitive layer, for example the following methods:
• the suitable aqueous solutions should contain at a pH of 5 to 6 citric acid, tartaric acid, gallic acid, sugar acid or their alkali, ammonium or alkaline earth salts; an application in the printing plate field is not mentioned.
• anodic oxidation in an aqueous electrolyte from an alkali silicate and an organic complexing agent is carried out.
• Phenols and glycols also salts of organic carboxylic acids such as maleic acid, fumaric acid, citric acid or tartaric acid.
• the electrolyte concentrations should preferably be between 0.1 and 15% by weight for the silicate and between 1 and 12% by weight for the complexing agent.
• the preferred process parameters are: the temperature between 15 and 40 ° C, the coating time between 0.5 and 5 min, the current density between 0.5 and 3 A / dm 2 .
• a printing plate support material was used in Example 9 in an electrolyte containing 9.2% by weight of sodium silicate, 6.3% by weight of monoethanolamine and 0.9% by weight of sodium potassium tartrate at a current density of 3 A / dm 2 anodized for 15 min and at 45 to 50 ° C.
• the process for the production of grain-like or grained surfaces on aluminum according to DE-AS 26 51 346 is carried out directly on aluminum with alternating current in an electrolyte which is 0.01 to 0.5 mol / l in aqueous solution an alkali metal or alkaline earth metal hydroxide or salt and optionally 0.01 to 0.5 mol / l of a barrier layer former.
• a coloring treatment is carried out, optionally after previous anodic oxidation.
• the barrier layer formers should also include citric acid, tartaric acid, succinic acid, lactic acid, malic acid or their salts.
• Example 5 No anodic oxidation of the aluminum is carried out before the grain-like or grained surface is produced.
• the aluminum substrate to be treated is hung vertically in the electrolytic bath in order to achieve the desired grain.
• an aqueous electrolyte with a content of 10 g / 1 of Na orthosilicate and 30 g / 1 of Na tartrate was used at a current density of 3 A / dm 2 for 15 minutes.
• the products produced in this way are said to be suitable for the production of window frames, wall panels (paneling) and decorative moldings for vehicles or household articles.
• the object of the present invention is to propose a method for the aftertreatment of flat aluminum, which can be carried out in addition to anodic oxidation of the aluminum and leads to a surface on the aluminum oxide produced in this way, which in particular meets the practical requirements of a high-performance printing plate described at the outset.
• the invention is based on the known method for the production of plate, film or tape-shaped Ma materials based on chemically, mechanically and / or electrochemically roughened and anodically oxidized aluminum or one of its alloys, the aluminum oxide layers of which are post-treated with an aqueous alkali silicate solution.
• the process according to the invention is then characterized in that the aftertreatment is carried out with an aqueous alkali silicate solution which additionally contains at least one aliphatic hydroxy mono-, di- or tricarboxylic acid, an aliphatic dicarboxylic acid or a water-soluble salt of these acids. Materials treated in this way are used in particular as supports for offset printing plates.
• the aliphatic carboxylic acids which can be used in the process according to the invention include, in particular, hydroxytricarboxylic acids such as citric acid, hydroxydicarboxylic acids such as tartaric or malic acid, hydroxymonocarboxylic acids such as glycolic, lactic or gluconic acid or dicarboxylic acids such as oxalic, malonic, maleic or succinic acid.
• hydroxytricarboxylic acids such as citric acid
• hydroxydicarboxylic acids such as tartaric or malic acid
• hydroxymonocarboxylic acids such as glycolic, lactic or gluconic acid or dicarboxylic acids
• oxalic, malonic, maleic or succinic acid oxalic, malonic, maleic or succinic acid.
• the corresponding water-soluble salts such as alkali metal or ammonium salts, are preferably used, since they only slightly change the pH of the aqueous alkali silicate solution; this
• the treatment can be carried out as an immersion treatment or electrochemically, the latter procedure often bringing an increase in the resistance to alkali.
• the electrochemical process variant is carried out in particular with direct or alternating current, trapezoidal, rectangular or triangular current or overlapping forms of these types of current; the current density is generally 0.1 to 10 A / dm 2 .
• the treatment of the materials can be carried out discontinuously or continuously in modern belt systems, the treatment times are expediently in the range from 5 to 120 seconds and the treatment temperatures are from 15 to 80 ° C., in particular from 40 to 75 ° C.
• the aqueous solution contains general 1 to 50 g / l, in particular 5 to 30 g / l, of an alkali silicate (such as sodium metasilicate or the sodium and tetrasilicates contained in the "water glass") and 3 to 50 g / l, in particular 5 to 20 g / l, one of the above acids and / or salts.
• the weight ratio of silicate to acid / salt is preferably in the range from 1: 1 to 4: 1.
• the aluminum support materials for printing plates found in practice are mechanically (e.g. by brushing and / or with abrasive treatments), chemically (e.g. by etching agents) or electrochemically (e.g. by alternating current treatment) before the photosensitive layer is applied roughened in aqueous HCl and / or HN0 3 solutions).
• Aluminum printing plates with electrochemical roughening are used in particular for the present invention.
• the process parameters in the roughening stage are in the following ranges: the temperature of the electrolyte between 20 and 60 ° C, the active substance (acid, salt) concentration between 5 and 100 g / l, the current density between 15 and 130 A / dm 2, the residence time between 10 and 100 sec and the Elektrolytströmungsge - velocity in continuous processes at the surface of the workpiece to be treated between 5 and 100 cm / sec; AC is usually used as the type of current, but modified types of current such as AC with different amplitudes of the current strength are also possible for the anode and cathode currents.
• the average roughness depth R z of the roughened surface is thereby in the range from about 1 to 15 ⁇ m, in particular in the range from 2 to 8 ⁇ m.
• the roughness depth is determined in accordance with DIN 4768 in the version from October 1970, the roughness depth R z is then the arithmetic mean of the individual roughness depths of five adjacent individual measuring sections.
• Direct current is preferably used for the anodic oxidation, but alternating current or a combination of these types of current (eg direct current with superimposed alternating current) can also be used; the electrolyte is in particular an aqueous solution containing H 3 PO 4 .
• the Layer weights of aluminum oxide range from 1 to 10 g / m 2 , corresponding to a layer thickness of approximately 0.3 to 3.0 pm.
• all layers are suitable as light-sensitive layers which, after exposure, optionally with subsequent development and / or fixation, provide an imagewise surface from which printing can take place. They are either applied to the substrate by the manufacturer of presensitized printing plates or directly by the consumer.
• Negative-working condensation products from aromatic diazonium salts and compounds with active carbonyl groups preferably condensation products from diphenylamine diazonium salts and formaldehyde, which are described, for example, in DE-PS 596 731, 1 138 399, 1 138 400, 1 138 401, 1 142 871, 1 154 123, U.S. Patents 2,679,498 and 3,050,502 and British Pat. No. 712,606.
• Negative-working mixed condensation products of aromatic diazonium compounds for example according to DE-OS 20 24 244, which each have at least one unit of the general types A (-D) n and B connected by a double-bonded intermediate member derived from a condensable carbonyl compound.
• A is the remainder of at least two aromatic carbocyclic and / or heterocyclic Nuclei-containing compound which is capable of condensing with an active carbonyl compound in an acidic medium at at least one position.
• D is a diazonium salt group attached to an aromatic carbon atom of A; n is an integer from 1 to 10; and B is the remainder of a compound free of diazonium groups and capable of condensing with an active carbonyl compound in an acidic medium at at least one position on the molecule.
• Positive-working layers according to DE-OS 26 10 842 which contain a compound which cleaves off on irradiation, a compound which has at least one COC group which can be cleaved by acid (for example an orthocarboxylic acid ester group or a carboxylic acid amide acetal group) and optionally a binder .
• Negative working layers made of photopolymerizable monomers, photoinitiators, binders and optionally other additives.
• the monomers used here are, for example, acrylic and methacrylic acid esters or reaction products of diisocyanates with partial esters of polyhydric alcohols, as described, for example, in US Pat. Nos. 2,760,863 and 3,060,023 and DE-OSes 20 64 079 and 23 61 041.
• Suitable photoinitiators include benzoin, benzoin ethers, multinuclear quinones, acridine derivatives, phenazine derivatives, quinoxaline derivatives, quinazoline derivatives or synergistic mixtures of various ketones.
• a large number of soluble organic polymers can be used as binders find, e.g. B. polyamides, polyesters, alkyd resins, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, gelatin or cellulose ether.
• Negative working layers according to DE-OS 30 36 077 which contain a diazonium salt polycondensation product or an organic azido compound as a photosensitive compound and a high molecular weight polymer with pendant alkenylsulfonyl or cycloalkenylsulfonylurethane groups as a binder.
• photoconductive layers such as z. B. in DE-PS 11 17 391, 15 22 497, 15 72 312, 23 22 046 and 23 22 047 are described, applied to the carrier materials produced according to the invention, whereby highly light-sensitive, electrophotographic printing plates are formed.
• the coated offset printing plates obtained from the carrier materials according to the invention are converted into the desired printing form in a known manner by imagewise exposure or irradiation and washing out of the non-image areas with a developer, preferably an aqueous developer solution.
• a developer preferably an aqueous developer solution.
• offset printing plates, the base support materials of which have been post-treated by the process according to the invention have a lower tendency than those plates in which the same base material has been post-treated with aqueous solutions containing only silicates, by an improved hydrophilicity of the non-image areas for color fog formation, an improved alkali resistance and the achievement of a steeper gradation (measured with a halftone step part).
• An aluminum foil is electrochemically roughened in dilute aqueous HN0 3 solution with alternating current and anodically oxidized in dilute aqueous H 2 S0 4 solution with direct current.
• the subsequent treatment is carried out either only with Na 2 SiO 3 .5H 2 0 (comparative examples V2, V3), only with KN tartrate (comparative example V4) or with a mixture of both components (examples 1 to 3) and with a film compared without any aftertreatment (comparative example VI).
• the test conditions and results can be found in the table below.
• the type of electrochemical treatment usually improves the resistance to alkali compared to a pure immersion treatment under otherwise identical conditions.
• Oxide layers produced in H 2 S0 4 solutions are attacked more strongly by silicate solutions at higher temperatures than oxide layers produced in H 3 P0 4 solutions, so that the treatment times and temperatures are severely restricted without the use of the mixture according to the invention.
• Examples 16 and 17 and Comparative Examples V18 to V21 An aluminum foil is electrochemically roughened in a dilute aqueous HC1 or HN0 3 solution using an alternating current and anodically oxidized in a dilute aqueous H 2 S0 4 solution.
• the subsequent treatment with an aqueous solution of a content of 40 g / 1 of Na 2 Si0 3 • 5 H 2 0 and 20 g / 1 at KNa-tartrate (Examples 16 and 17) performed with foils without any post-treatment ( V18 and V20) or with polyvinylphosphonic acid (PVPS) aftertreatment (V19 and V21).
• the test conditions and results can be found in the table below.
• the oxide layers aftertreated with aqueous polyvinylphosphonic acid solutions show good hydrophilicity and a good reduction in the sensitivity to color fog, but they are not yet satisfactory in all cases.
• An aluminum foil aftertreated according to Examples 16 and 17 is coated with the following positive-working light-sensitive mixture:
• Examples 18 to 61 and Comparative Examples V22 to V26 An aluminum foil is electrochemically roughened in dilute aqueous HCl or HN0 3 solution with an alternating current and anodically oxidized in dilute aqueous H 2 S0 4 solution. The subsequent treatment is carried out with an aqueous solution of Na 2 SiO 3 .5 H 2 0 (comparative examples) or a mixture of silicate / organic carboxylic acid or carboxylic acid salt - as can be seen from the table - carried out. Hydroxycarbon or dicarboxylic acids are used as carboxylic acids, ie carboxylic acids with one or more carboxyl groups and at least one hydroxyl group or carboxylic acids with two carboxyl groups.
• the pH of the resulting aqueous solutions drops by about 1.5 to 2.5 values, which in some cases leads to a reduction in the alkali resistance (measured by the gravimetric method).
• This effect can be compensated for by increasing the temperature or extending the treatment time; the use of the electrochemical process variant also brings improvements.
• a significant improvement in the alkali resistance to pure silicate solutions can be achieved by adjusting the pH values of the aqueous solutions to values which are in the range of the pH value of pure silicate solutions. This setting can be brought about by the direct use of salts (alkali metal or ammonium salts) of the carboxylic acids mentioned, or by adding bases, such as aqueous NaOH solution, to the aqueous silicate / acid mixtures. It is also possible to use alternating current instead of direct current in the electrochemical process variant.
• Examples 62 to 72 and Comparative Examples V27 to V36 An aluminum foil is electrochemically roughened in alternating current in dilute aqueous HCl or HN0 3 solution and anodically oxidized in dilute aqueous H 2 S0 4 solution.
• the subsequent treatment is no longer with Na 2 SiO 3 .5 H 2 0 (sodium metasilicate) with a ratio of Na 2 0: Si0 2 as 1. 1 carried out that used relatively aggressively affects the aluminum oxide layer without additive, but with water glass DAB VI with a solids content of about 33%, ie usually a mixture of sodium tri- and tetrasilicates with an approximate ratio of Na 2 0: Si0 2 as 3: 1.
• KN tartrate is added as the second component.
• Examples 73 to 76 and Comparative Examples V37 to V40 The procedure of the example groups 1 to 3 and V1 to V4 is followed, but with aluminum foil which is anodically oxidized in an aqueous electrolyte containing H 2 S0 4 and H 3 P0 4 (according to Teaching of DE-OS 28 36 803).

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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)
• General Chemical & Material Sciences (AREA)
• Printing Plates And Materials Therefor (AREA)
• Electrochemical Coating By Surface Reaction (AREA)

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• 1982
  • 1982-05-27 DE DE19823219922 patent/DE3219922A1/de not_active Withdrawn
• 1983
  • 1983-04-28 DE DE8383104145T patent/DE3377069D1/de not_active Expired
  • 1983-04-28 EP EP83104145A patent/EP0095581B1/fr not_active Expired
  • 1983-05-19 CA CA000428489A patent/CA1225613A/fr not_active Expired
  • 1983-05-24 JP JP58090139A patent/JPS58213894A/ja active Granted

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