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
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
  • C23F11/18—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using inorganic inhibitors
  • C23F11/184—Phosphorous, arsenic, antimony or bismuth containing 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/23—Condensed phosphates
• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/68—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous solutions with pH between 6 and 8
• • 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
  • C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
  • C23D3/00—Chemical treatment of the metal surfaces prior to coating
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/923—Physical dimension
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
  • Y10T428/12556—Organic component
  • Y10T428/12569—Synthetic resin
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12986—Adjacent functionally defined components
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/27—Web or sheet containing structurally defined element or component, the element or component having a specified weight per unit area [e.g., gms/sq cm, lbs/sq ft, etc.]
  • Y10T428/273—Web or sheet containing structurally defined element or component, the element or component having a specified weight per unit area [e.g., gms/sq cm, lbs/sq ft, etc.] of coating

Definitions

• the direct white enamelling of steel sheet has in recent years become a reliable production process.
• a consistent quality of the enamelled products combined with a reduction in the enamelling costs have been achieved by rationalizing the production program and introducing continuous, programmed production methods.
• Further simplification in the operational program in the enamelling plant is provided by the fact that the strip used for producing the blanks is already pretreated in the steel works to prepare it for the single layer enamelling, this pretreatment consisting e.g. of a suitable pickling process followed by nickel coating.
• the bonding surface thereby obtained which serves as a foundation for the single layer white enamelling must, of course, then be protected before the forming operation so that the layer applied to it will not be damaged.
• This protection can be achieved by the conventional process of pretreating the strips with an electrolytically applied layer of zinc (Belgian Patent specification No. 557,963 and French Patent specification No. 1,187,958).
• metal materials which are formed by drawing, pressing, pickling or other non-machining processes and are then provided with a firmly adhering metal or non-metallic layer are degreased and pickled immediately after they have been produced and are then provided with a covering which protects their surfaces but which can easily be removed.
• Metal coatings which are deposited by electrocoating or by chemical processes or stoving lacquers, dipping varnishes and other synthetic resin coatings also require a very clean foundation to ensure permanent protection of the surfaces. The problem of providing the metal worker with a starting material which is practically ready for use for the subsequent coating operation is, therefore, not confined to the enamelling industry.
• the process according to the invention is used advantageously in enamelling work and is particularly efficient for single layer enamelling which requires specially pretreated metal surfaces.
• the steel sheets which are to be shaped are advantageously degreased immediately after they have been produced, pickled and then covered with a layer of nickel.
• the surface treatment is carried out by conventional processes which may be either purely chemical, fully electrolytic or a combination of the two.
• an electrolytically degreased, electrolytically pickled and electrolytically nickel plated metal sheet may first be cleaned by a coarse alkaline degreasing operation.
• the sequence of pretreatment stages would in this case be as follows:
• the advantage of the electrolytic pretreatment compared with the purely chemical method lies in a shortening of the total time of stay by about 65 percent.
• the water-soluble polyphosphate is thereafter applied, e.g. by the immersion or spray process.
• the entire treatment, including the production of the sheet metal, can be carried out completely continuously.
• the degreasing, pickling and nickel plating are advantageously carried out electrolytically.
• the sheet metal provided with the covering layer can then be shaped by rolling, pressing or drawing or by other non-machining methods. After the shaping operation, the covering may be stripped off or washed off with water before the enamelling process without the surfaces which have been prepared for enamelling being in any way impaired.
• the covering of a polyphosphate used according to the invention acts as a lubricant in the shaping operation, especially if an organic auxiliary agent is added, and no impairment in the bonding of the enamel or in the enamel surface can be ascertained even if the covering is incompletely removed or not removed at all.
• the process according to the invention is not confined to enamelling processes but can also be applied to similar technical fields in which shaped metal articles are subsequently provided with a protective layer; in all these cases, however, if the protective layer is to be firmly bonded, a carefully cleaned and in some cases specially pretreated surface is necessary.
• the process affords advantages also for the production, for example, of metal articles which, after they have been shaped, are treated with an electrocoating or chemical process to metallize them or cover them with a synthetic resin coating.
• Polyphosphates which are suitable for the process of the invention are salts of polyphosphoric acids having the general formula: HO[HOPO H in which n is an integer of at least 10, and preferably more than 100.
• the hydrogen is replaced by monovalent cations such as Na, K, Li", NHf, or substituted ammonium ions; both polyphosphates which have only one type of ion and polyphosphates with different ions may be used.
• mixed salts such as Na/K salts are preferably used for the sake of solubility in a polar, preferably aqueous, medium.
• the polyphosphate solutions used for producing the protective layers according to the invention are prepared by conventional methods.
• the starting materials used are generally polyphosphates such as Kurolls salts, Madrells salts or Graham's salts, and, if they are insufficiently soluble in water, some of the cations are replaced by other types of cations.
• K-Kurollate K P which is insoluble in water may be suspended in water and then brought into solution by the addition of from 0.5 to 6 parts of a sodium phosphate such as sodium polyphosphate [NaPO or the phosphates Na P O Na P O (NaPOQ (sodium trimetaphosphate), (NaPO (sodium hexametaphosphate) and Na PO
• a sodium phosphate such as sodium polyphosphate [NaPO or the phosphates Na P O Na P O (NaPOQ (sodium trimetaphosphate), (NaPO (sodium hexametaphosphate) and Na PO
• the potassium polyphosphate may also be dispersed in water and some of the potassium ions may be replaced by sodium ions by means of an ion exchanger which contains sodium ions so that a soluble Na/K polyphosphate is obtained.
• the properties of the protective layers of polyphosphates can be influenced by the addition of organic substances of high or low molecular weight.
• the addition of water-soluble polymers of medium to low molecular weights may have a plasticizing effect which makes the coatings pliable, elastic and smooth and have a lubricating effect in the shaping operation carried out on sheet metal.
• a low molecular weight substance for example, the rate at which the protective coating dissolves when it is being removed prior to the enamelling can be increased.
• the effect on the films varies according to the molecular weight of the organic polymers added, the films becoming softer and more ductile when polymers of low molecular weight are added, whereas the addition of high molecular weight polymers influences the properties of the protective layers in the direction of the film properties of the organic polymers.
• Substances which although influencing the physical properties of the protective layers mainly exert their influence on the redissolution of the protective layers are mainly those which have a surface active effect, such as non-ionic, anionic or cationic emulsifiers.
• the following are mentioned as examples from this group of substances: polyglycol ethers, reaction products of phenols or alcohols with ethylene oxide, fatty acid salts, sorbitan esters, sulfonates such as alkylbenzene sulfonates and sulfuric acid semiesters of long chain alcohols.
• the rate of solution is, of course, also increased by the addition of oligomers or polymers of low molecular weight.
• the organic substances may, in principle, be added in any proportion, based on the polyphosphate.
• the desired effects are generally achieved with quantities of from about 1 to percent, whereas the emulsifiers are sometimes effective in very small quantities, i.e. in concentrations of from about 0.01 to 10%, based on the polyphosphate.
• the polyphosphates and the organic additives may be applied separately, in which case mixing may occur due to diffusion in the applied layers of solutions.
• the solutions of the polyphosphates to be applied and the organic additives are first mixed.
• small quantities of age resistors or stabilizers for the organic substances may be added.
• the coatings with the substances used according to the invention may be applied by conventional methods, e.g. by spraying, immersion and brush application.
• spraying e.g. by spraying, immersion and brush application.
• very thin films e.g. just a few molecules thick which corresponds to a surface coating of from 0.2 to 2 g of polyphosphate per m, it is advantageous to spray an aqueous or organic solution on to the surface and evaporate the solvent.
• EXAMPLE 1 A cold rolled steel sheet having the following approximate analytical composition:
• the polyphosphate solution was obtained by reacting (KPO with NaCl in the molar ration of 1:3 by adding NaCl in a proportion of 1:3 to a suspension of (KPO in water, separating the swelled precipitate after stirring for one hour, and dissolving the precipitate in pure water.
• the molecular weight of the polyphosphate is expressed in terms of its viscosity lrmr/c where c concentration in g/lOO ml of solvent.
• the polyphosphate contains 7.5 percent of potassium and 13.1 percent of sodium.
• EXAMPLE 2 A steel sheet having the analytical composition indicated in Example 1 was subjected to a preliminary alkaline degreasing operation, then thoroughly degreased electrolytically, rinsed, pickled electrolytically in a solution of 150 g of Na,SO -l0 11 0/1 and 5 ml of concentrated H 80 per liter at a current density of lOA/dm for 1 minute, rinsed and finally nickel coated in a solution of 80 g of NiSO -7 l'l O/l, 10 g of Nl-LCl/l, g of MgSO -7 H O/l and 5 g of H BO /l at a current density of0.5 A/dm for 1 minute.
• the sheet After rinsing, the sheet was coated with a 0.35 percent aqueous K-, Na-polyphosphate solution by immersion, dried and then shaped in a hydraulic press as conventionally used in enamelling works. After the shaping operation, the protective layer was removed by spraying with water and the article was dried and enamelled by direct white enamelling with a B-Ti white enamel of the composition described in Example 1. Both adherence and enamel surface were excellent.
• the same polyphosphate solution as in Example 1 was used.
• EXAMPLE 3 A steel sheet having the analytical composition indicated in Example 1 was pretreated as in Example 1.
• the pretreated sheet was brush coated with a 2 percent aqueous K-, Na-polyphosphate solution which contained 6 percent of K, Na-hexametaphosphate as foreign salt.
• the sheet was subjected to a shaping operation as conventionally carried out in enamelling works.
• the polyphosphate layer was then removed by spraying with water.
• the shaped sheet was enamelled by direct white enamelling with a B-Ti white enamel of the composition given in Example 1. Both adherence and enamel surface were excellent.
• the polyphosphate solution was obtained by stirring [K- P0 with (NaPO l :3) in water. Viscosity lnnr/c 9.1
• EXAMPLE 4 A steel sheet with the analytical composition indicated in Example 1 was pretreated as in Example 1.
• the pretreated sheet was spray coated with a 2 percent aqueous solution of K-, Na-polyphosphate solution which contained 5 percent of polyethylene glycol (molecular weight 1000) as plasticizer. After drying of the applied layer, the sheet was subjected to a powerful shaping operation in the enamelling works. The polymer coating was then removed by brushing under running water. The sheet was then enamelled by direct white enamelling with a B-Ti white enamel of the composition described in Example 1. Both adherence and enamel surface were excellent. The same K-, Napolyphosphate solution as in Example 3 was used.
• EXAMPLE 5 A steel sheet with the analytical composition indicated in Example 1 was pretreated as in Example 2.
• the pretreated sheet was spray coated with a 2 percent aqueous 14-, Na-polyphosphate solution which contained 6 percent of K-Na-hexametaphosphate as foreign salt and 8 percent of polyvinyl ethyl ether (molecular weight 1,500) as plasticizer.
• the sheet After drying of the applied layer, the sheet was subjected to a powerful shaping operation in the enamelling plant.
• the polyphosphate layer was then removed by spraying with water.
• the subsequent direct white enamelling with a B-Ti white enamel of the composition described in Example 1 yielded excellent results as regards adherence and enamel surface.
• the polyphosphate solution was the same as that used in Example 3.
• Example 6 A steel sheet with the analytical composition indicated in Example 1 was pretreated as in Example 1.
• the pretreated sheet was coated with a 2 percent aqueous K-, Na-polyphosphate solution containing 0.8 percent of oleic acid oxethane sulfonate (Na-salt of the sulfuric acid monoester with olcyl alcohol), using two rubber rollers. After drying of the applied layer, the sheet was pressed in the enamelling plant to form a cover plate of an electric stove available on the'market. The polymer coating was then removed by spraying with water. It was found that this coating could be washed off exceptionally quickly.
• EXAMPLE 7 Three thin metal sheets A, B and C having the analytical composition indicated in Example 1 were pretreated as described'in Example 2. Sheet A was shaped into the cover plate of an electric stove in the enamelling plant without a protective layer of polymer. The shaped metal sheet A was enamelled by direct white enamelling with a B-Ti white enamel of the composition described in Example 1. Both the adherence and the enamel surface were very poor.
• Sheet B was shaped exactly like sheet A but subsequently sprayed with water.
• Sheet C was spray coated with a 2 percent K-, Napolyphosphate solution (see Example 3) containing l.5 percent of nonylphenol polyglycol ether before it was shaped. After drying of the polymer layer, sheet C was shaped in the same way as sheets A and B. The polyphosphate layer was then removed by spraying with water. The shaped metal sheet C was then direct white enamelled with the B-Ti enamel of the composition described in Example 1. Both the adherence and the enamel surface were excellent, in contrast to sheets A and B.
• EXAMPLE 8 A steel sheet having the analytical composition indicated in Example 1 was pretreated as in Example 1.
• the pretreated sheet was spray coated with a 2 percent aqueous K-, Na-polyphosphate solution which contained percent of polyethylene gylcol (molecular weight 1,000) as plasticizer.
• the metal sheet was subjected to powerful shaping in the enamelling plant without previous drying of the applied layer.
• the polymer coating was then removed by brushing under running water. Direct white enamelling with a B-Ti white enamel of the composition described in Example 1 was then carried out. Both the adherence and the enamel surface were excellent.
• the same K-, Napolyphosphate solution as in Example 3 was used.
• a process for the temporary protection of a metal surface which has been freshly prepared which comprises covering said surface with a coating of at least about 0.2 grams per square meter of a water-soluble mixed sodium and potassium salt of a polyphosphoric acid of the formula HO(HOPO ),,H in which n is at least about 10, whereby said coating may be removed by water to expose the fresh metal surface.
• n is at least about 100.
• polyphosphate coating includes an organic water-soluble polymer, which polymer serves to plasticize the poly-phosphate.
• n is at least about 100, and wherein said polyphosphate coating includes an emulsifier and a film-forming organic water-soluble polymer.
• a shaped metal structure having an adherent protective layer comprising the steps of chemically or electrolytically pretreating a metal sheet to provide a fresh surface, shaping said sheet into a structure and providing an adherent, protective layer on said shaped structure, the improvement which comprises covering said fresh surface with a coating of at least about 0.2 grams per square meter of water-soluble mixed sodium and potassium salt of a polyphosphoric acid of the formula HO(H OPO ),,I-l in which n is at least about 10, before shaping w hereby said fresh surface is unimpaired during shaping and is directly ready for receipt of the adherent protective layer.
• a metal structure having a freshly prepared chemically or electrolytically treated surface and a protective coating of at least about 0.2 grams per square meter of a water-soluble mixed sodium and potassium salt of a polyphosphoric acid of the formula HO(HOPO in which n is at least about 10.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Chemistry (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Chemical Treatment Of Metals (AREA)
• Laminated Bodies (AREA)

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Citations (10)

• 1969
  • 1969-12-30 DE DE1965586A patent/DE1965586C3/de not_active Expired
• 1970
  • 1970-12-10 CH CH1827670A patent/CH567576A5/xx not_active IP Right Cessation
  • 1970-12-14 US US00098104A patent/US3723162A/en not_active Expired - Lifetime
  • 1970-12-18 SE SE17235/70A patent/SE368842B/xx unknown
  • 1970-12-22 GB GB60791/70A patent/GB1281135A/en not_active Expired
  • 1970-12-28 JP JP45119498A patent/JPS5230458B1/ja active Pending
  • 1970-12-29 NL NL7018967A patent/NL7018967A/xx unknown
  • 1970-12-29 ES ES386878A patent/ES386878A1/es not_active Expired
  • 1970-12-29 AT AT1171370A patent/AT305725B/de not_active IP Right Cessation
  • 1970-12-30 FR FR7047397A patent/FR2074488A5/fr not_active Expired
  • 1970-12-30 BE BE761066A patent/BE761066A/xx unknown

Patent Citations (10)

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