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
  • 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
  • C23C22/08—Orthophosphates
• • 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

Definitions

• the present invention relates to a novel surface treatment method for tin plated DI cans, i.e., cans formed by the drawing and ironing of tin plated steel sheet.
• the method imparts excellent corrosion resistance and paint ad- hesivity to the surface of the can prior to its being painted or printed, and also imparts the excellent slide- ability (low frictional resistance) that is required for smooth transport of the can by automatic conveying equip- ment, particularly modern high speed conveying equipment.
• the invention of Japanese Patent Application Laid Open [Ko ai or Unexamined] Number 1-100281 [100,281/89] is an example of a surface treatment liquid for tin plated DI cans.
• This teaching of the prior art employs a film form ⁇ ing liquid for the treatment of metal surfaces.
• This solu ⁇ tion has a pH of 2 to 6 and contains 1 to 50 gram per liter ("g/L") of phosphate, 0.2 to 20.0 g/L of oxyacid ions, 0.01 to 5.0 g/L of tin ions, and 0.01 to 5.0 g/L of condensed phosphate.
• Treatment with this conversion treatment solu ⁇ tion afforded a highly corrosion resistant phosphate film on the surface of tin-plated DI cans.
• Treatment methods intended to provide corrosion re ⁇ sistance and adhesivity through the use of water soluble resin are exemplified by the invention in Japanese Patent Application Laid Open Number 1-172406 [172,406/89].
• This invention provided as an example of the prior art comprises a method in which the metal surface is treated with a solu ⁇ tion which contains an effective derivative of a polyhydric phenol compound.
• the disclosed method does not generate a satisfactorily stable corrosion resistance.
• the metal can manufacturing process often suffers from a problem with transfer or transport: the slideability of the outer surface of the can during convey ⁇ or transport of the can may be poor due to a high friction coefficient of the outer surface, so that the can may be tipped over sideways.
• the invention of Japanese Patent Application Laid Open Number 64-85292 [85,292/89] comprises a method for improving this slideability.
• the reference teaches a surface treatment composition for metal cans which contains water-soluble organic material selected from phosphate esters, alcohols, monobasic, and polybasic fatty acids, fatty acid deriva ⁇ tives, and mixtures of the foregoing. While the disclosed method does in fact generate an increase in the slideabil- ity, it does not improve the corrosion resistance or paint adhesion.
• the principal goal of the invention is to provide a single treatment for DI cans that will result in increased corrosion resistance, good adhesion to subsequently applied paint or similar organic coatings, and a low coefficient of friction on the outside can surface, for efficient process- ing in automated can processing lines using high speed con ⁇ veyors and printers.
• a liquid treating composition is prepared by dissolv ⁇ ing in water an oligomer having a chemical composition specified by the general formula:
• n is a number with a value between 10 and 30 and each of X and Y independently represents hydrogen or a group Z, wherein Z has a chemical composition conforming to the general formula:
• each of R_ and is an alkyl or hydroxyalkyl group having from 1 to 5 carbon atoms, except that at least 25 % of the total of all the X and Y groups in the oligomer are Z rather than hydrogen.
• the pH of the surface treatment solution containing the oligomer described in item (1) is adjusted to a value between 4 and 6 by the addition of orthophos- phoric acid and/or condensed phosphoric acid.
• the surface treatment liquid as prepared in step (2) is heated to a temperature of at least 40 but prefer ⁇ ably to not more than 60 degrees Centigrade and the ably to not more than 60 degrees Centigrade and the heated surface treatment liquid is then sprayed on the cleaned surface of tin plated DI can for a time of at least 5 and preferably not more than 60 seconds.
• the aforesaid spray treatment is followed by thermal drying or by a water rinse and then thermal drying.
• the sprayed cans drain under the influence of gravity, and/or to remove some of the liquid from the can surface by mechanical means such as an air flow, rollers under slight pressure, or the like, to avoid the presence of excessive amounts of the surface treatment liquid on the surface during drying.
• n in the general formula given above for the oligomer dissolved in the surface treatment liquid is 10 to 30. At values of n below 10, little or no improve ⁇ ment in corrosion resistance will be observed on DI tin plated cans. A value of 31 or more for n results in a poorly stable aqueous solution which cannot readily be used in practical applications.
• R. and R repre ⁇ sent alkyl or hydroxyalkyl groups having 1 to 5 carbon atoms. When they contain six or more carbons, the stabil ⁇ ity of the aqueous solution is reduced.
• the introduction ratio for the group Z should be 25 to 100 mole % referred to the total number of X and Y groups in the oligomer.
• the water solubility of the oligomer may not be adequate when over 75 % of the total of X and Y groups present are hydro ⁇ gen.
• the oligomer solids content in the treatment liquid preferably is from 0.1 to 0.5 % by weight ("w/o") of the total liquid. Below 0.1 w/o, it is very difficult to form a stable film on a DI tin can surface. On the other hand, the treatment solution is costly above 0.5 w/o, with little or no additional technical benefit.
• the pH of the treatment solution should be adjusted to 4 to 6 through the use of orthophosphoric acid and/or a condensed phosphoric acid such as pyrophosphoric acid. Substantial etching of the can surface occurs at a pH below 4 and impairs film formation. At a pH above 6, the solu ⁇ tion has a short life because the oligomer tends to pre ⁇ cipitate and sediment.
• the pH can normally be adjusted into the range of 4 to 6 by the addition of 0.05 to 0.3 w/o orthophosphoric acid or 0.03 to 0.2 w/o pyrophosphoric acid referred to the total surface treatment liquid.
• Other con ⁇ densed phosphoric acids and mixtures of condensed acids or of condensed and orthophosphoric acids can also be used.
• the treatment liquid should be heated to at least 40 degrees Centigrade during use.
• the treatment liquid is poorly reactive below 40 degrees Centigrade, and this works against the formation of a highly corrosion re ⁇ sistant film.
• little or no benefit due to heating is observed when the liquid is heated to above 60 degrees Centigrade, and unnecessary heating is expen- sive.
• the spraying time should be at least 5 seconds. Only an inadequate reaction is obtained at less than 5 seconds, and a strongly corrosion resistant film is not developed. On the other hand, treatment times in excess of 60 seconds do not afford any increase in performance and increase the expense.
• a small sprayer was used for the degreasing and sur ⁇ face treatment of the cans. This small sprayer was de- signed to give spray conditions identical to those encount ⁇ ered in spray treatment with the can washers which are cur ⁇ rently in use in the can manufacturing industry.
• the corrosion resistance of a treated can was evaluat ⁇ ed through the iron exposure value ("IEV") , which was mea- sured according to the directions in United States Patent 4,332,646.
• IEV iron exposure value
• the paint adhesiveness was evaluated as follows: an epoxy-urea can paint was coated to a film thickness of 5 to 7 micrometers (microns) on the surface of the treated can, which was subsequently baked for 4 minutes at 215 degrees Centigrade; the can was then cut into a 5 x 150 millimeter (“mm") strip, onto which was hot-pressed polyamide film in order to afford a test specimen; and this was then peeled in a 180" peel test to give the peel strength. Higher peel strength values correspond to a better adhesiveness.
• n had an average value of 20 and X represented hydrogen.
• This oligomer was synthesized as follows: 100 grams ("g") of CellosolveTM solvent (the monoethyl ether of ethylene glycol) was introduced into a 1 liter reaction flask equipped with a condenser, nitrogen inlet tube, over- head stirrer, and thermometer, and 60 g of poly ⁇ 4-vinyl phenol ⁇ with an average molecular weight of 2,500 was added and dissolved; 40 grams of 2-methylamino ethanol and 100 g of deionized water were added, and the contents of the flask were heated to 50 degrees Centigrade; 40 g of 37% formaldehyde solution in water was added over 1 hour, fol ⁇ lowed by stirring at 50 degrees Centigrade for 2 hours and by further heating to 80 degrees Centigrade and stirring for an additional 3 hours at that temperature; the reaction product was cooled, 15 g of 85 % orthophosphoric acid was added, and 700 g of deionized water was also added
• Tin plated steel sheet was drawn and ironed to afford tin plated DI cans, which were spray-rinsed with a hot 1% aqueous solution of a weakly alkaline degreaser (FINE CLEANERTM 4361A from Ninon Parkerizing Company, Limited, Tokyo) and then rinsed with water.
• Cans were then sprayed for 40 seconds with surface treatment liquid 1 (described below) , heated to 50 degrees Centigrade, followed by a wash with tap water, then a 10 second spray with deionized water (with a specific resistance of at least 3,000,000 ohm*cm) , then drying for 3 minutes in a hot air dryer at 180 degrees Centigrade.
• Surface-treatment liquid 1 had the following composition: oligomer solids 0.2 weight % 75% orthophosphoric acid 0.1 weight % water 99.7 weight % pH 5.5
• Example 2 Example 2
• Tin plated DI cans werer cleaned as in Example 1, then spray treated for 40 seconds with surface treatment liquid
• Example 2 heated to 50 degrees Centigrade. This was followed by a water wash and drying as in Example 1.
• the composition of surface treatment liquid 2 was: oligomer solids 0.2 weight %
• the oligomer used was the same as in Example 1.
• Tin plated DI cans were cleaned as in Example 1, then spray treated for 10 seconds with the above described surface treatment liquid 1 (cf. Example 1) , which had been heated to 50 degrees Centigrade. This was followed by a water wash and drying as in Example 1.
• Tin plated DI can was cleaned as in Example 1, then spray treated for 40 seconds with the above described sur ⁇ face treatment liquid 1 (cf. Example 1) , which had been heated to 50 degrees Centigrade. This was followed by draining, without water rinsing, and then drying in a hot air dryer at 180 degrees Centigrade for 3 minutes.
• Tin plated DI cans were cleaned as in Example 1, spray treated for 40 seconds with comparison surface treat ⁇ ment liquid 1, heated to 50 degrees Centigrade, then washed with water and dried as in Example 1.
• Comparison surface treatment liquid 1 had the following composition: oligomer solids 0.2 weight % 75% orthophosphoric acid 1.5 weight % water 98.3 weight % pH 2.0 The oligomer used was the same as in Example 1.
• Comparison Example 2
• Tin plated DI cans were cleaned as in Example 1, spray treated for 2 seconds with the above described sur ⁇ face treatment liquid 1 (cf. Example 1) , which had been heated to 50 degrees Centigrade, then washed with water and dried as in Example 1.
• sur ⁇ face treatment liquid 1 cf. Example 1
• Tin plated DI cans were cleaned as in Example 1, then spray treated for 40 seconds with the Comparison surface treatment liquid 2, heated to 50 degrees Centigrade, then washed with water and dried as in Example 1.
• the composi ⁇ tion of Comparison surface treatment liquid 2 was: oligomer solids 0.2 weight %
• the oligomer used for Comparison surface treatment liquid 2 was not the same as that used for the Examples and the preceding Comparison examples, but instead had the ap- proximate formula:
• n has an average value of 20 and X represents hydrogen.
• S0_ liquid sulfur trioxide

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Paints Or Removers (AREA)
• Electroplating Methods And Accessories (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (4)

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Citations (4)

• 1990
  • 1990-01-10 JP JP320090A patent/JPH03207766A/ja active Pending
• 1991
  • 1991-01-10 CA CA002072258A patent/CA2072258A1/en not_active Abandoned
  • 1991-01-10 AU AU72243/91A patent/AU642468B2/en not_active Ceased
  • 1991-01-10 EP EP91903769A patent/EP0510105B1/en not_active Expired - Lifetime
  • 1991-01-10 ES ES91903769T patent/ES2063494T3/es not_active Expired - Lifetime
  • 1991-01-10 DE DE69104825T patent/DE69104825T2/de not_active Expired - Fee Related
  • 1991-01-10 WO PCT/US1991/000202 patent/WO1991010756A1/en active IP Right Grant
  • 1991-01-10 BR BR919105932A patent/BR9105932A/pt not_active IP Right Cessation

Patent Citations (4)

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