Classifications

• • 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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F1/00—Etching metallic material by chemical means
  • C23F1/10—Etching compositions
  • C23F1/14—Aqueous compositions
  • C23F1/42—Aqueous compositions containing a dispersed water-immiscible liquid

Definitions

• This invention relates to the powderless etching of metals, and more particularly relates to a novel powderless etching method having a consistent high etch rate capability and high capacity for dissolving metal in the preparation and consistent obtention of quality etched products.
• a primary object of the present invention is to provide a novel method for increasing the etch rate and capacity for dissolving metal in producing magnesium base metal plates in powderless etching bath, While consistently obtaining high quality in substantially every plate etched thereby.
• a further object of the invention is to provide an increased capacity powderless etching bath having a high etch rate capability for producing quality etched products characterized by a more uniform and desirable shoulder profile.
• the novel method of the present invention comprises: in an etching machine; (1) impinging a powderless etching bath at a temperature within the range of from about 65 to about F. against a magnesium base metal plate having an acid resistant coated image pattern thereon, at a maximum force of impingement while yet avoiding detrimental under-cutting and loss of halftone and highlight dots, said powderless etching bath consisting essentially of (A) aqueous nitric acid, (B) a filming agent, (C) one or more organic liquids, and, as optional additional ingredients, (D) film controlling agents, (2) admixing with said bath after completion of the first and each successive plate etched, a bath extender composition com prising, by addition into the bath, from about .058 to 7104 gin, per gram of dissolved base metal, of a petroleum sul'fonate, from about .04 to .07 gm., per gram of dissolved base metal, of sodium ar-monochloro-ar'-dode
• the powderless etching bath composition employed in the present novel method consists essentially of the following components and amounts.
• Acid component is essentially nitric acid. Operable amounts of nitric acid range from about to about percent by volume (142 to 213 grams per liter) (based on 42 B. nitric acid, technical grade), and preferably about 10 to 12 percent (142 to 170 grams per liter). A particularly preferred amount is 12 percent by volume.
• filming agent component (B) Filming agent component
• the filming agent employed herein is principally sulfonated ar-monochloro-ar-dodecyldiphenyl oxide corresponding to the following formula:
• M in the sulfonic group is hydrogen, an alkali metal, an alkaline earth metal, ammonium, or a substituted ammonium radical, the presence of other chloro isomers not exceeding about percent, said filming agent comprising at least about 70 percent monosulfonate, there being up to about percent disulfonate, the alkyl group herein designated as dodecyl containing an average of 12 carbon atoms, but ranging from about 9 to about 15 carbon atoms, there being a preponderance of C material.
• the filming agents thus delineated are further characterized in that they must be soluble in the etching bath with partial solubility in each of the bath phases, viz., the aqueous and organic phases.
• the amounts of the filming agent employed can range from about 5 to about 12.5 gms. per liter of bath, a preferred range being from about 5.75 to 7.5 gms. per liter of bath. A particularly desirable amount is about 6.25 gms. per liter of bath.
• the filming agent is added to the bath as a 50 percent solution in an aromatic naphtha solvent such as Solvesso 150 (defined hereinafter).
• the solvent component of the powderless etching bath of the present novel method comprises an aromatic naphtha and an alkyl benzene mixture.
• the aromatic naphtha component is a hydrocarbon liquid characterized by a boiling range at 760 mm. of Hg starting at about 325 F., 50 percent distilled at 450 F., and dry point at 540 F. It is a mixture of aromatics from C to C plus some naphthalenes and contains 80 percent aromatics with the remainder being aliphatics, having a Kauri Butanol range of from about 100 to about 110.
• a particular aromatic naphtha found suitable for use in the invention is a commercial aromatic solvent sold under the tradename of Penola H.A.N. (Heavy Aromatic Naphtha), which contains 84 percent aromatics, has a flash point of 140 F. and a distillation temperature range at 760 mm. Hg: initial boiling point of 340 F.', 50 percent distilled at 446 F., and dry point at 532 F.
• Penola H.A.N. Heavy Aromatic Naphtha
• the alkyl benzene component is a branched chain bydrocarbon liquid with a distillation range at 760 mm. Hg: 5 percent recovery from about 525 to 545 F. and 95 percent recovery from about 550 to 575 F., and a Kauri Butanol value range of from about 40 to about 50.
• An alkyl benzene found particularly desirable for use in the invention consists of dodecyl benzene having a boiling range at 760 mm. of Hg: 5 percent recovery at about 533 F. and 95 percent recovery at 563 F.
• Such material is commercially available, as Chevron Alkylate 21, from the Chevron Chemical Co., Oronite Division.
• the amount of the aromatic naphtha liquid to be used ranges from about 9 to about 46 gms. of liquid per liter of bath, a preferred amount being about 28 gms. per liter of bath.
• the alkyl benzene liquid is used in an amount of from about 9 gms. to about 18 gms. of liquid per liter of bath, preferably about 13 gms. per liter of bath.
• the remainder or balance of the bath, other than the optional additional ingredients described hereinafter, is water but it should be understood that other materials may also be present in the bath.
• One reason for the presense of such other materials is that as a practical matter it is diflicult if not impossible to employ the aforementioned bath components in a pure state since they are not readily obtained pure.
• Another reason for the presence of other materials is that they may enhance the bath performance in some particular respect, or, as a convenience and facility in making additions.
• the solid filming agent sodium ar-monochloro-ar-dodecyldiphenyl oxide sulfonate
• SC-150 aromatic solvent
• Solvesso 150 is a trademark for a commercial aromatic solvent which is a mixture of approximately percent alkyl benzenes, 2 percent naphthalene, 8 percent naphthenes, a flash point of F., initial boiling point (at 760 mm. of Hg) of 330 F., 50 percent distilled at 378 F., and dry point at 415 F.
• the film-controlling agents which may be used in the powderless etching bath of the invention may be a single aliphatic dicarboxylic acid or a blend of such compounds which individually consist of only hydrogen, carbon and oxygen and have 4 to 10 carbon atoms. These compounds, by viture of the results achieved when they are employed in etching baths individually or in blends, are called film-controlling agents.
• etching baths By their use in the above-described etching baths, it is possible to increase the depths of etch at lower etch rates, e.g., at 0.004"/min., obtainable in small areas of penetration in combination photoengraving plates such as halftone areas where proper or adequate depths of etch are usually difficult to obtain by bath modulation, without, at the same time, adversely weakening the protection achieved in open line areas of the same plate. At higher etch rates, e.g., at 0.005"/min., benefits from the filmcontrolling agent component are minimal.
• Another film-controlling agent which may optionally be employed to enhance the etching action of the bath comprises one or more inorganic sulfates soluble in aque ous dilute nitric acid solution.
• inorganic sulfates include, for example, sulfuric acid, sodium sulfate, sodium acid sulfate, magnesium sulfate, aluminum sulfate, and ammonium sulfate. In general, most any inorganic sulfate may be used, except heavy metal sulfates.
• Amounts of the dicarboxylic acid film-controlling agent employed are surprisingly small for the results to be accomplished.
• the amount employed can range from about 0 to about 1.5 gm. per liter of bath but a preferred range is from 0.4 to 0.6 gram per liter of bath.
• suflicient amount of the material should beadded such that the sulfate (80 content of the solute ranges from about 0.1 to about 0.4 gram per liter of bath solution, the preferred range being from about 0.2 to about 0.3 gram per liter of bath.
• the machine in formulating the foregoing powderless etching bath in a powderless etching machine of a given capacity, e.g., in liters, the machine is normally first filled about half full with tap water, whereupon, the nitric acid is added. Thereafter, the filming agent and filmcontrolling agent are added, either singly or together, the filming agent being preferably added as aforesaid as a 50 percent solution with SC-150 organic liquid. The machine is then filled to the proper level with water for the particular machine. The bath is then brought to the desired temperature. Obtaining a homogeneous mixture of the bath so-formulated is important and is achieved by operating the machine for a few minutes before etching any plates.
• etching machines of various designs may be used, it is preferred to employ an etching machine of the type disclosed in US. Patent 2,669,048, issued Feb. 16, 1954.
• the plate to be etched is mounted with the surface to be etched in the machine facing the bath.
• the machine is then actuated to impinge the bath against the plate for a time sufficient to obtain the depth of etch desired, while controlling the temperature within a range of from about 65 to about 80 F., preferably from about 72 to about 78 F.
• the machine paddle speed, or force of impingement in nonpaddle machines, during etching is held sufiicient to obtain the maximum etch rate, as may be predetermined, without detrimental affect on plate quality such as, e.g., by loss of halftone dots, chipping of the image, and undercutting.
• the paddle speed of a paddle type machine may vary, e.g., from 400 to about 700 rpm, depending upon the particular design of the machine.
• Etching machines of the type disclosed in the aforesaid patent may be operated for example from about 550 to 625 rpm. in accordance with the present invention to get the maximum etch rate.
• the paddle speed or force of impingement of the particular powderless etching machine must be adjusted by a few simple test runs to determine the maximum r.p.m.s or force of impingement at which a maximum etch rate is obtained as well as consistent satisfactory quality plates suitable for the printing purpose intended for such plates.
• Extender composition The extender composition of the present invention consists essentially of a three component organic liquid mixture of a petroleum sulfonate, sodium ar-monochloroar-dodecyldiphenyl oxide disulfonate, and an aromatic solvent, and is added to the foregoing powderless etching bath as a liquid in an amount of each component within the range herein specified for each.
• the extended components are most conveniently added after each plate is etched by the bath.
• the petroleum sulfonate component of the extender is a petroleum sulfonate having a molecular weight of from about 350 to about 450.
• Petroleum sulfonates containing mineral oil may also be employed and are included in the meaning of the term petroleum sulfonates as used herein.
• Twitchell Oil (tradename avail able from Emery Industry, Inc.) designated No. 7231, may be employed. This material is approximately a 30 percent solution of petroleum sulfonate in mineral oil.
• the petroleum sulfonate undiluted with mineral oil is employed by addition to the bath in an amount of from about .058 to about .104 gram per gm. of dissolved base metal, and preferably about .083 gram per gm. of dissolved base metal.
• the sodium ar-monochloro-ar-dodecyldiphenyl oxide disulfonate component of the extender corresponds to the following formula:
• M in the sulfonic group is hydrogen, an alkali metal, an alkaline earth metal, ammonium, or a substituted ammonium radical, the presence of other chloro isomers not exceeding about percent, and said sodium ar-monochloro-ar-dodecyldiphenyl oxide disulfonate being essentially a disulfonate, and preferably at least about 90 percent disulfonate, the dodecyl alkyl group containing an average of 12 carbon atoms, but ranging from about 9 to about 15 carbon atoms, there being a preponderance of C material.
• This disulfonate material as an extender component is employed in an amount of by addition to the bath of from about 0.04 to about 0.07 gram of disulfonate material per gram of dissolved base metal in said bath,
• the disulfonate component of the extender is added as, e.g., a 25 percent solids solution in water.
• the aromatic solvent component of the extender is a material characterized as a high Kauri Butanol, low viscosity, solvent, immiscible with water, having a KB value of from about to about l30.
• the solvent is substantially unreactive with the acid component of the powderless etching bath to which it may be added and contains substantially no terminal functional groups but rather a preponderance of carbon and hydrogen atoms.
• the aromatic naphtha liquid component of the extender is employed in an amount of from about 0.715 to about 1.195 gram per gram of dissolved base metal in the bath, and preferably from about 0.9 to about 1.0 gram per gram of dissolved metal.
• Example I A powderless etching bath of liters volume was prepared in a Chemco powderless etching machine Model 510 B by mixing together 15,600 ml. of 42 B. nitric acid (170 grams per liter of bath), 1625 ml. of a 50 percent solution of sodium ar-monochloro-ar-dodecyldiphenyl oxide sulfonate (filming agent) in Solvesso (13 grams per liter of bath), 52 grams of adipic acid (0.4 gram/liter of bath), 3900 ml. of Penola H.A.N. aromatic solvent (28 grams per liter of bath), and 1950 ml.
• extender components were employed in the preferred amounts stated hereinbefore when conveniently added in 2 ml. portions per gram of dissolved base metal in the powderless etching bath.
• Table I presents the results of this etching sequence showing, in tabulated forms, additions of acid, extender solution, total etch time for each plate in minutes, the bath temperature, paddle speed, plate size, depth of etch in inches, metal lost, in grams, by each plate, etch rate, and an evaluation of plate quality by means of a visual qualitative inspection.
• shoulder angle or shoulder profile used herein as an indication of plate quality, is the angle, expressed in degrees, that the shoulder slope, formed by etching, makes with a line perpendicular to the plane of the printing plate commencing at the top edge of a relief image.
• the shoulder angle is determined by measuring the horizontal shoulder projection from the perpendicular line of the plane of the printing plate at the top edge of the relief image (shoulder width) and the depth of etch. Then the shoulder width is divided by the depth of etch which gives the tangent of the shoulder angle. The angle is then determined from the tangent.
• Etch depth is the depth of etching in the open areas measured in inches.
• Metal loss is grams of magnesium dissolved per plate.
• Etch rate is mils of metal dissolved per minute.
• the bath temperature was adjusted and a number of magnesium photoengraving grade metal sheets having an etch resist image coating thereon were etched in said bath until the bath was depleted. After each plate was etched and weighed, replenishment amounts of nitric acid were added. After the 3rd, 4th and 5th plates a conventional bath additive known as Dowetch Extender (not in accordance with the present invcntion) was added to the bath according to the con vcntional practice.
• Dowetch Extender not in accordance with the present invcntion
• Table II presents the results and conditions of this comparative etching sequence as additions of acid and of extender, total etch time per plate and the desired degree of quality on the etched product.
• a typical etch rate for conventional powderless etching baths is 1.5 to 2 mils per minute.
• the time savings attending the high etch rate of Example I when compared to the comparative example is also readily apparent.
• the total time to etch 9 plates in each bath is 95 /2 minutes for the Example I bath as compared to 141.5 minutes for the bath of the comparative example-0ver 30 percent less time. Such time savings are beneficial in meeting production deadlines.
• the bath capacity in dissolved metal i.e., ability to dissolve more magnesium per bath is greatly increased by the present invention as is further manifest from Example I in relation to the comparative example by comparing the columns headed plate size, etch depth, and metal loss.
• the total capacity of the bath in Example I in dissolving metal before being depleted is 1757 grams, whereas, in the comparative example the capacity is 1372 gramsapproxiamtely a 28 percent greater canacity in the Example I bath.
• Example I Both in the comparative example and in Example I, the plate quality was substantially at the same high level.
• the Example I bath gave a greater capacity in dissolving metal and at a much faster rate.
• Example I The novelty, usefulness, and unobviousness of the present invention are clearly revealed in a detailed comparison of Example I and the comparative example.
• Example I The outstanding increase in average etch rate of the Example I of 3.36 mils per minute, as compared to the average of 2.02 mils in the comparative example employing a conventional bath, is readily apparent. This represents an average increase of about 66.3 percent in etch rate.
• the etching conditions were maximized to obtain the highest etch rate without sacrificing quality in the etched plate.
• common practice in the industry is also to etch under conditions to obtain the highest etch rate Waterbalance to make up 137 liters, employing a powderless etching machine in accordance with US Patent 2,669,048.
• the powderless etching machine was operated at 600 r.p.m. paddle speed with a bath temperature of 75 F. An etch rate of 5 thousandths of an inch per minute was obtained and the quality of etch was good. No extender of any kind was added.
• Example III This example compares the desirable shoulder profile obtained in accordance with the present invention as obtained in Example I above with the less favorable shoulder profile obtained in etched plates made employing conventional powderless bath and methods such as, e.g., in comparative Example A.
• the present invention concerns a novel and unobvious method of powderless etching with an outstanding average increase in etch rate wherein a consistent high quality of etch product is obtained and an increased capacity in said powderless etching bath to dissolve metal.
• the method comprises an unobvious combination of etching bath ingredients,'conditions of operation, and process steps which together provide a peculiar and specific method not heretofore disclosed.
• conventional powderless" etching baths and methods were modified to, inter alia, increase the amount of nitric acid therein, and increase the bath temperature and paddle speed to obtain etch rates comparable to the present invention, poor if not unusable quality etched products would result, giving rise in effect, to little or no useful bath capacity.
• the present invention lies in a critical combination of ingredients and amounts, conditions of etching, and process steps.
• a method of etching comprising: in an etching machine, impinging a powderless etching bath at a temperature within the range of from about 65 to about 85 F. against an etchable magnesium base metal plate having an acid resistant coated image pattern thereon, said powderless etching bath comprising (A) from about to about volume percent of nitric acid, (B) from about 5.0 to about 12.5 grams per liter of bath of an ionic sulfonated ar-monochloro-ar-dodecyldiphenyl oxide consisting of at least about 70 percent by weight of the monosulfonate and the balance the disulfonate, (C) a liquid organic mixture consisting essentially of (1) an aromatic naphtha characterized by a mixture of aromatics from C to C in a concentration of at least about percent, and a Kauri Butanol value range of from about 100 to 110, and (2) an alkyl benzene branched chain hydrocarbon liquid characterized by a boiling range at 5 percent recovery of about
• the powderless etching bath includes as an optional additional component from about 0 to about 15 grams per liter of bath of an organic dicarboxylic acid consisting of only hydrogen, carbon and oxygen and having 4 to 10, inclusive, carbons.
• the powderless etching bath includes as an optional additional component an inorganic sulfate-containing compound soluble in aqueous dilute nitric acid solution in an amount sufficient such that the sulfate content of the bath ranges from about 0.1 to about 0.4 gram per liter of bath.
• a liquid organic mixture consisting essentially of (1) an aromatic naphtha characterized by a mixture of aromatics from C to C in a concentration of at least about 80 percent, and a Kauri Butanol value range of from about 100 to 110, and (2) an alkyl benzene branched chain hydrocarbon liquid characterized by a boiling range at 5 percent recovery of about 525 to about 545 F. and percent recovery at about 550 to 575 F. and a Kauri Butanol value range of from about 40 to about 50, said aromatic naphtha being employed in an amount of from about 9 to about 46 grams per liter of bath, said aliphatic substituted benzene being employed in an amount of from about 9 to about 18 grams per liter of bath;

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Citations (2)

• 1966
  • 1966-09-20 US US580622A patent/US3490968A/en not_active Expired - Lifetime
• 1967
  • 1967-08-29 NL NL6711856A patent/NL6711856A/xx unknown
  • 1967-09-14 DE DE19671621444 patent/DE1621444A1/de active Pending
  • 1967-09-19 NO NO169787A patent/NO117773B/no unknown
  • 1967-09-19 GB GB42646/67A patent/GB1143059A/en not_active Expired
  • 1967-09-19 SE SE12869/67A patent/SE300777B/xx unknown
  • 1967-09-20 BE BE704082D patent/BE704082A/xx unknown
  • 1967-09-20 CH CH1312067A patent/CH500294A/de not_active IP Right Cessation

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