LIQUID COMPOSITION AND PROCESS FOR TREATING ALUMINIUM OR TIN CANS TO IMPART CORROSION RESISTANCE AND REDUCED FRICTION COEFFICIENT

Abstract: A corrosion resistant film with a low coefficient of friction that facilitates automatic conveying can be formed on the surface of tin-plated steel or of aluminum, particularly DI cans of one of these types of metal, by contacting the aluminum or the tin plated steel with an aqueous liquid composition having a pH in the range from 2.0 to 6.5 and containing: (A) from 1 to 30 g/L of phosphate ions, (B) from 0.1 to 10 g/L of condensed phosphate ions, and (C) from 0.1 to 20 g/L as solids of a water-soluble resin component selected from the group of resins, including mixtures of resins, having general chemical formula (I) wherein n is an integer within the range from 10 to 80 inclusive; each of X and Y is independently selected from hydrogen or a group "Z" with formula (II), except that at least 15 % the total of all of the X and Y groups in this component of the composition are Z rather than hydrogen; and (II) wherein each of R1 and R2 in each of the phenyl rings in the formula independently is selected from the group consisting of alkyl groups containing from 1 to 10 carbon atoms per group and hydroxyalkyl groups containing from 1 to 10 carbon atoms per group.

Description: LIQUID COMPOSITION AND PROCESS FOR TREATING ALUMINIU_ OR TIN CANS TO IMPART CORROSION RESISTANCE AND REDUCED FRICTION COEFFICIENT TECHNICAL FIELD The present invention relates to a novel liquid compo¬ sition for treating the surface of tin-plated steel and/or aluminum and alloys that are predominantly aluminum (both the pure metal and alloys being denoted hereinafter by the word "aluminum" unless the context requires otherwise) , particularly the surfaces of drawn-and-ironed (hereinafter "DI") cans made from these materials. The composition im¬ parts an excellent corrosion resistance and paint adhes- iveness to the surface of such a can after its formation by the drawing and ironing of metal sheet but before its painting or printing. This novel liquid composition also imparts the excellent mobility or slideability, i.e., low frictional resistance, which is required for the smooth conveyor transport of such a can. The composition also is relatively low in pollution potential, because it contains no deliberately introduced chromate or fluorine. The in¬ vention also relates to processes for using the composi¬ tion according to the invention. BACKGROUND ART In the field of liquid compositions for treating the surface of tin-plated DI can of the aforementioned type, one example is the invention disclosed in (1) Japanese Pat¬ ent Application Laid Open [Kokai or Unexamined] Number 01- 100,281 [100,281/89]. This particular invention comprises a film-forming liquid composition for the treatment of met¬ al surfaces in which the liquid composition has a pH of 2 to 6 and contains 1 to 50 g/L of phosphate ions, 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 ion. Treatment with this conversion treatment liquid composition lays down a strongly corrosion-resistant phosphate film on the surface of a tin-plated DI can. The inventions disclosed in (2) Japanese Patent Appli- cation Laid Open Number 01-172,406 [172,406/89] and U. S. Patent 4,457,790 are examples of a treatment method intend¬ ed to develop corrosion resistance and adhesiveness through the use of water soluble resin. These inventions teach methods for treating metal surfaces with a solution which contains a derivative of a suitable polyhydric phenol com¬ pound and an aminomethylene substituted phenolic polymer or oligomer respectively. The treatment baths previously employed to treat the surface of aluminum and aluminum alloy of the aforemen- tioned type can be generally classified into chromate types and non-chromate types. The chromate types typically take the form of chromic acid chromate conversion treatments and phosphoric acid chromate conversion treatments. Chromic acid chromate conversion treatments entered into practical application in about 1950, and these are still widely used for heat exchanger fin material and the like. This type of conversion treatment bath is based on chromic acid (CrO ) and hydrofluoric acid (HF) and also contains an accelerat¬ or. It lays down a film which contains modest quantities of hexavalent chromium. The phosphoric acid chromate conversion treatment de¬ rives from the invention in United States Patent Number 2,438,877 (1945), and this type of conversion treatment bath is based on chromic acid (CrO ) , phosphoric acid (H PO ) , and hydrofluoric acid (HF) . It forms a film whose principal component is hydrated chromium phosphate (CrPO '4H 2 0). As this film does not contain hexavalent chromium, it is currently widely employed as a paint under- coating treatment for the body and lid of beverage cans. The invention disclosed in Japanese Patent Application Laid Open [Kokai or Unexamined] Number 52-131937 [131,937/ 77] is a typical prior art example within the realm of non- chromate types of treatments for aluminum. The disclosed treatment bath comprises an acidic aqueous coating solution (pH = approximately 1.0 to 4.0) which contains zirconium or titanium or a mixture thereof, as well as phosphate and fluoride. The application of this conversion treatment bath exemplary of the prior art to the surface of aluminum generates a conversion film whose principal component is zirconium oxide or titanium oxide. While the absence of hexavalent chromium is an advantage associated with non- chromate type treatment baths, the corrosion resistance and paint adherence achieved with such baths in the prior art are inferior to those with chromate type treatments. Fur¬ thermore, both the chromate type treatments and non-chrom¬ ate type treatments contain fluorine, while environmental considerations have recently created demand for a fluorine- free surface treatment bath. Within the sphere of treatment methods which use wat¬ er-soluble resin in order to impart corrosion resistance and paint adherence to aluminum, the following are listed as exemplary of the prior art: Japanese Patent Applica¬ tion Laid Open Number 61-91369 [91,369/86] and Japanese Patent Application Laid Open Number 01-172406 [172,406/89]. In these methods, the metal surface is treated with a solu¬ tion which contains a useable derivative of a polyhydric phenolic compound. However, it is difficult with these methods to form an adequately stable film on the surface of aluminum, and this precludes the appearance of a satisfac¬ tory performance (corrosion resistance) . During the metal can manufacturing process, the high friction coefficient of the exterior can surface causes the can surface to have a poor slideability during conveyor transport of the can, which causes the can to tumble over sideways and thus impairs the transport operation. Can transportability is a particular issue with respect to transport to the printer in a high speed continuous manu¬ facturing plant. It is therefore important in the can man¬ ufacturing industry to reduce the static friction coeffi¬ cient of the exterior can surface without compromising the adhesiveness of any paint or lacquer to be coated on the can. The invention disclosed in (3) Japanese Patent Appli¬ cation Laid Open Number 64-85292 [85,292/89] is an example of a method for improving the slideability. This inven- tion concerns an agent for treating the surfaces of metal cans. This particular agent contains water-soluble organ¬ ic material selected from phosphate esters, alcohols, monovalent and polyvalent fatty acids, fatty acid deriva- tives, and mixtures of the preceding. DESCRIPTION OF THE INVENTION Problems to Be Solved by the Invention The above-described invention (1) does lead to the formation of a strongly corrosion-resistant phosphate film on conventional tin-plated DI can; however, the tin-plated DI can produced over the last few years has used smaller quantities of tin plating in response to economic pres¬ sures. This has necessitated surface treatments with a far better corrosion resistance than before, and this demand is not entirely satisfied by invention (1) . The other above described inventions do not always result in a satisfac¬ torily stable corrosion resistance with the tin-plated DI can produced over the last few years or with aluminum cans. Finally, the above-described invention (3) does in fact im- prove the slideability, but it sometimes does not improve the corrosion resistance or paint adhesiveness to an ade¬ quate degree. Thus, with respect to cans carrying small quantities of tin plating or aluminum cans, the prior art leaves prob- le s unsolved with regard to the formation of a highly cor¬ rosion resistant film and with regard to improvements in the slideability and paint adhesiveness. Summary of the Invention As a concrete means for solving the aforementioned problems which arise in the prior art, the present inven¬ tion provides a liquid composition for treating the surface of tin-plated DI can, said liquid composition being char¬ acterized by a pH of 2.0 to 6.5 and containing 1 to 30 g/L of phosphate ions, 0.1 to 5 g/L of condensed phosphate ion if used on tin plated steel or 0.1 to 10 g/L of condensed phosphate ions if used on aluminum, and 0.1 to 20 g/L (as solids) of water-soluble resin with the following general formula: where n is an integer within the range from 10 to 80 in¬ clusive; each of X and Y is independently selected from hy¬ drogen or a group "Z" with the formula given below, except that at leas 15 % of the total of all the X and Y groups in this component of the composition are Z rather than hy¬ drogen; and H R 1 ■ N H R where each of R and R independently is a C to C. _ alkyl and/or hydroxyalkyl group. Application of a surface-treatment liquid composition according to the present invention provides an aluminum or a tin-plated DI can surface with an- excellent corrosion re¬ sistance and paint adhesiveness prior to its painting or printing and also generates the excellent slideability nec¬ essary for smooth conveyor transport of the can. Finally, because the treatment bath according to the present inven¬ tion does not contain chromium or fluorine, the waste water treatment load is substantially reduced compared to most prior treatment baths, especially for aluminum. Details of Preferred Embodiments of the Invention The surface-treatment liquid composition according to the present invention is an acidic treatment liquid compo¬ sition whose essential components are phosphate ions, con¬ densed phosphate ions, and water-soluble resin of a par¬ ticular type. The phosphate ions can be introduced into the treat¬ ment liquid composition using phosphoric acid (H_PO.) , sod¬ ium phosphate (Na_PO ) , and the like. Its content should fall within the range preferably of 1 to 30 g/L and more preferably of 5 to 15 " g/L. At below 1 g/L, the reactivity is relatively poor and film formation generally will not be satisfactory. A good-quality film can be formed at values in excess of 30 g/L, but the cost of the treatment liquid composition is increased and the economics are therefore impaired. The condensed phosphate ions are selected from pyro- phosphate ions, tripolyphosphate ions, and tetrapolyphos- phate ions. The acid or salt can be used to introduce the condensed phosphate ions. For example, when pyrophosphate ions are to be introduced, pyrophosphoric acid (H.P_0 ) , sodium pyrophosphate (Na.P 0_) , and the like can be used. This component should be present at 0.1 to 5 g/L for treating tin plated steel or at 0.1 to 10 g/L for treating aluminum, and the range of 0.4 to 1 g/L for tin plate or 1.0 to 4.0 g/L for aluminum is particularly preferred. At values less than 0.1 g/L, a satisfactory film will not be formed because of weak etching activity. However, the etching activity is undesirably high at values in excess of 5 g/L on tin plate or 10 g/L on aluminum, and the film- forming reaction is inhibited. The water-soluble resin used by the present invention comprises polymers with the general formula already given above. The molecular weight is too low at values of n in this formula below 10, so that little or no improvement in corrosion resistance will normally be observed. At values for n of 81 and above, the aqueous solution has a reduced stability, which will normally generate problems in practi¬ cal applications. Functional groups R χ or R 2 containing 11 or more carbons usually would reduce the stability of an aqueous solution containing them. The group Z is prefer¬ ably -CH 2 N(CH 3 ) 2 or -CH 2 N(CH 3 )CH 2 CH 2 OH. When less than 15 % of the total of all the X's and Y's in the resin are Z, there are usually stability problems with the compositions that would otherwise be according to the invention. The water soluble resin should be present at a concen¬ tration of from 0.1 to 20 g/L on a solids basis. At values less than 0.1 g/L, stable film formation on the can surface highly problematic. Values in excess of 20 g/L are uneco¬ nomical due to the increased cost of the treatment solu¬ tion. The pH of the treatment liquid composition must be from 2.0 to 6.5. Etching is heavy and film formation is impaired at pH values less than 2.0. At values in excess of 6.5, the liquid composition life is shortened because the resin tends to precipitate and sediment. The pH can be adjusted through the use of an acid, for example, phos¬ phoric acid, nitric acid, hydrochloric acid, hydrofluoric acid (if waste water contamination with fluoride is not a problem) , and the like, or through the use of a base, for example, sodium hydroxide, sodium carbonate, ammonium hy¬ droxide, and the like. When metal ions (e.g., tin, aluminum, or iron) are introduced into the treatment liquid composition, precipi¬ tation may occur due to the formation of a resin/metal ion complex, and a chelating agent in addition to the resin as specified above should preferably be added to the treatment liquid composition in such cases. While this chelating agent is not specifically restricted, chelating agents use¬ ful within this context are exemplified by tartaric acid, ethanolamine, gluconic acid, oxalic acid, and the like. The method for preparing the surface-treatment liquid composition according to the present invention can be briefly described as follows. Prescribed quantities of phosphate ions and condensed phosphate ions as described above are dissolved in water with thorough stirring. When the pH of this liquid composition is not already less than 7, it is adjusted to below 7 using the appropriate acid as noted above. The water-soluble resin specified by the present invention is then added and completely dissolved while stirring, and the pH is adjusted if necessary as dis¬ cussed above. The film which is formed by means of the present in¬ vention's surface-treatment liquid composition is believed to be an organic and inorganic composite film which is com- posed primarily of the resin and phosphate salts (the main component is believed to be tin phosphate when tin plated substrates are treated) . While the invention is not limit¬ ed by any theory, it is believed that the substrate is etched by the phosphate ions and condensed phosphate ions, the pH at this time is locally increased at the interface, and phosphate salt is deposited on the surface. Moreover, the amino group in the resin has a chelating activity, and it may form a type of coordination compound with the fresh surface of the substrate generated by etching. The simul- taneous presence of the condensed phosphate ions is thought to promote formation of resin/metal coordination compounds, and this may make possible the stable formation of the com¬ posite film on the surface over a broad pH range. A process according to the invention for treating tin- plated DI can using a surface-treatment liquid composition of the present invention will now be considered. The pres¬ ent invention's treatment liquid composition can be applied by the following process sequence, which is a preferred se¬ quence for a process according to this invention. 1. Surface cleaning: degreasing (a weakly alkaline cleaner is typically used on tin-plated DI can, while an alkaline, acidic, or solvent based degreaser may be effectively used on aluminum cans.) 2. Tap water wash Film-formation treatment (application of the treatment liquid composition according to the present invention) treatment temperature: ambient to 80 ° C treatment method: spray treatment time: 2 to 60 seconds 4. Tap water wash . . . 5. Wash with de-ionized water 6. Drying A surface-treatment liquid composition according to the present invention can conveniently be used at treatment temperatures from room temperature up to 80 ° C; however, it is generally preferably used at 40 to 60 ° C. The spray time preferably should be 2 to 60 seconds. At less than 2 seconds, a highly corrosion-resistant film will not usually be formed. No improvement in performance is observed for treatment times in excess of 60 seconds, but the cost is increased. Accordingly, the preferable treatment time will fall in the range from 2 to 60 seconds. The practice of the invention and the superior per¬ formance of surface-treatment liquid composition according to the present invention may be further appreciated from the following working and comparison examples. Examples General Methods and Criteria for the Examples The corrosion resistance of treated tin plated cans was evaluated using the iron exposure value ("IEV") , which was measured in accordance with the teaching of United States Patent No. 4,332,646. The corrosion resistance is better at lower IEV values, and a score below 150 is gener¬ ally regarded as excellent. The corrosion resistance of aluminum DI cans was evaluated based on the resistance to blackening by boiling water. A treated aluminum DI can was immersed for 30 minutes in boiling tap water, and the de¬ gree of discoloration (blackening) was visually evaluated in order to determine the resistance to blackening by boil¬ ing water. The following scale was used to score the re- sistance to blackening by boiling water: no blackening = + +, blackening of part of the surface = +, blackening of the entire surface = x. The paint adhesiveness was evaluated based on the peel strength as follows: The surface of the treated can was coated with an epoxy/urea can paint to a film thickness of 5 to 7 micrometers; this was baked at 215 ° C for 4 min¬ utes; the can was then cut into a 5 x 150 mm strip; a test specimen was prepared by hot-press adhesion with polyamide film; and this was peeled by the 180 ° peel test method. Accordingly, the paint adhesiveness improves as the peel strength increases, and values in excess of 1.5 kilograms of force per 5 millimeters of width (hereinafter "kgf/5 mm-width") on tin plate or in excess of 4.0 kgf/5 mm-width on aluminum are generally regarded as excellent. The slideability was evaluated by measuring the static friction coefficient of the exterior surface of the can. Thus, the slideability improves as the static friction co¬ efficient declines, and values below 1.0 are generally re¬ garded as excellent. Tin-plated DI cans were prepared by drawing and iron¬ ing tin-plated steel sheet. They were cleaned with a 1% hot aqueous solution of a weakly alkaline degreaser (FINE CLEANER 4361A, registered brand name of Nihon Parkerizing Company, Limited) , then sprayed with a surface-treatment liquid composition according to the invention as described below for each specific example. Aluminum DI cans were prepared by drawing and ironing aluminum alloy (A3004) sheet. They were cleaned with a 3 % hot aqueous solution of an acidic degreaser (PARCLEAN™ 400, commercially available from Nihon Parkerizing Company, Ltd.), then sprayed a with surface-treatment liquid compo¬ sition according to the invention as described below for each specific example. Example 1 A tin-plated DI can was cleaned as described above, then sprayed with surface-treatment liquid composition 1 as described below, heated to 60 ° C, for 30 seconds, then washed with tap water, sprayed with de-ionized water (with a specific resistance of at least 3,000,000 ohm*cm) for 10 seconds, and, finally, dried in a hot air-drying oven at 180 ° C for 3 minutes. Surface-treatment liquid composition 1 75% phosphoric acid (H-PO.) : 10.0 g/L (P0 4 3 ~: 7.2 g/L) sodium pyrophosphate (Na.P-O-'lOH-O) : 1.0 g/L (P 2 0 7 4 ~: 0.4 g/L) resin solids: 2.0 g/L of water-soluble resin 1, in which n in the general formula given above for this resin averaged 40, half of the total of the X's and Y's in the formula were Z, and Z was -CH^N(CH 3 )CH 2 CH 2 OH pH = 4.0 (adjusted with sodium hydroxide) Water-soluble resin 1 was synthesized as follows. CELLOSOLVE solvent in an amount of 100 grams (hereinafter "g") was introduced into a 1,000 milliliter (" L") reaction flask equipped with a condenser, nitrogen inlet tube, over- head stirrer, and thermometer, and 60 g of poly{4-vinyl- phenol} with a molecular weight of 5,000 was added and dis¬ solved. Then 40 g of 2-methylaminoethanol and 100 g of de¬ ionized water were added, and this was reacted by heating to 50 ° C. Then 40 g of 37 % aqueous formaldehyde solution was added over 1 hour, followed by stirring at 50 ° C for 2 hours and by stirring for an additional 3 hours at 80 ° C. The reaction product was cooled, 15 g of 85% ortho- phosphoric acid was added, and 700 g of deionized water was also added. The resin was then precipitated by the addi- tion of 10 % aqueous sodium hydroxide solution until the pH of the reaction solution reached 8 to 9. The precip¬ itated resin was filtered off, washed with water, and dried. Example 2 Tin-plated DI can was cleaned using the same condi¬ tions as in Example 1 and was then treated with a 30 second spray of surface-treatment liquid composition 2, heated to 60 ° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 2 75% phosphoric acid (H_P0 ) : 10.0 g/L (PO- 3" : 7.2 g/L) sodium pyrophosphate (Na.P-O-'lOH-O) : 1.0 g/L (P 2 0 ? 4 ~: 0.4 g/L) resin solids: 0.4 g/L of water soluble resin 1 as in Example 1 pH = 5.0 (adjusted with sodium carbonate) Example 3 Tin-plated DI can was cleaned using the same condi¬ tions as in Example 1 and was then treated with a 30 second spray of surface-treatment liquid composition 3 heated to 60 ° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 3 75% phosphoric acid (H-PO.) : 20.0 g/L (P0 4 3" : 14.4 g/L) sodium pyrophosphate (Na.P 2 0 ? 'lOH-O) : 1.0 g/L (P 2 0 7 4_ : 0.4 g/L) resin solids: 8.0 g/L of water-soluble resin 1 as in Example 1 pH = 4.0 (adjusted with sodium hydroxide) Example 4 Tin-plated DI can was cleaned using the same condi¬ tions as in Example 1 and was then treated with a 30 second spray of surface-treatment liquid composition 4 heated to 60 ° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 4 75% phosphoric acid (H.PO.) : 15.0 g/L (P0 4 3 ~: 10.9 g/L) sodium pyrophosphate (Na.P 2 0 «10H 0) : 2.5 g/L (P 2 0 7 4_ : 1.0 g/L) resin solids: 4.0 g/L of water-soluble resin 1 as in Example 1 pH = 3.0 (adjusted with sodium carbonate) Example 5 Tin-plated DI can was cleaned using the same condi- tions as in Example 1 and was then treated with a 30 sec¬ ond spray of surface-treatment liquid composition 5 heated to 60 ° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 5 75% phosphoric acid (H_P0.) : 30.0 g/L (P0. 3 ~: 21.6 g/L) sodium tripolyphosphate (Na_P 3 0 10 ) : 0.6 g/L (P 3°10 5 ~ : ° *4 L) resin solids: 2.0 g/L of water-soluble resin 1 as in Example 1 pH = 3.5 (adjusted with sodium hydroxide) Example 6 Tin-plated DI can was cleaned using the same condi¬ tions as in Example 1 and was then treated with a 30 second spray of surface-treatment liquid composition 6 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 6 75% phosphoric acid (H 3 P0 4 ) : 10.0 g/L (P0 4 3 ~: 7.2 g/L) sodium pyrophosphate (Na.P 2 0 7 ' lOH^O) : 1.0 g/L (P 2 0 7 4" : 0.4 g/L) resin solids: 2.0 g/L of water-soluble resin 2 pH = 4.0 (adjusted with sodium hydroxide) Water soluble resin 2 was made in the same way as water soluble resin 1, except that the quantities of mater¬ ial used were 60 g of poly-4-vinylphenol, 20 g of 2-methyl- aminoethanol, and 40 g 37% formaldehyde solution. As a re¬ sult of these changes, n in the general formula given for the resin had an average value of about 40 as before, but only about 25 % of the total of all X's and Y's in the formula were of type Z. Example 7 Tin-plated DI can was cleaned using the same condi¬ tions as in Example 1 and was then treated with a 30 second spray of surface-treatment liquid composition 7 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 7 . 75% phosphoric acid (H 3 P0 4 ) : 10.0 g/L ( po 4 3 ~: 7.2 g/L) sodium pyrophosphate (Na.P.O «10H_O) : 1.0 g/L (P 2 0 7 4" : 0.4 g/L) resin solids: 2.0 g/L of water-soluble resin 3 pH = 6.0 (adjusted with sodium hydroxide) Water soluble resin 3 was made in the same way as water soluble resin 1, except that 24 g of dimethylamine were substituted for the 40 g of 2-methylaminoethanol used in making water soluble resin 1. As a result of this change the Z groups in water soluble resin 3 had the for - ula -CH N(CH ) , but the average value of n in the general formula remained about 40 and about 50 % of the total X's and Y's in the general formula were of type Z. Comparison Example 1 Tin-plated DI can was cleaned using the same condi- tions as in Example 1 and was then treated with a 30 second spray of surface-treatment liquid composition 8 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example l. Surface-treatment liquid composition 8 75% .phosphoric acid (H PO.) : 10.0 g/L (P0 4 3_ : 7.2 g/L) resin solids: 2.0 g/L of the same water-soluble resin as in Example 1. pH = 4.0 (adjusted with sodium carbonate) Comparison Example 2 Tin-plated DI can was cleaned using the same condi¬ tions as in Example 1 and was then treated with a 30 second spray of surface-treatment liquid composition 9 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 9 75% phosphoric acid (H 3 P0 ) : 1.0 g/L (P0 4 3_ : 0.72 g/L) resin solids: 2.0 g/L of the same water-soluble resin as in Example 1 pH = 7.0 (adjusted with sodium hydroxide) Comparison Example 3 Tin-plated DI can was cleaned using the same condi- tions as in Example 1 and was then treated with a 30 second spray of surface-treatment liquid composition 10 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 10 75% phosphoric acid (H 3 P0 ) : 10.0 g/L (P0 4 3" : 7.2 g/L) sodium pyrophosphate (Na.P O -10H O): 1.0 g/L (P 2 0 y 4 ~: 0.4 g/L) resin solids: 0.05 g/L of the same water-soluble resin as in Example l pH = 4.0 (adjusted with sodium carbonate) Comparison Example 4 Tin-plated DI can was cleaned using the same condi¬ tions as in Example 1 and was then treated with a 30 second spray of surface-treatment liquid composition 11 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 11 75% phosphoric acid (H PO ) : 1.0 g/L ( p °A 3_: °- 72 9/ L ) sodium pyrophosphate (Na P O -lOH-O): 1.0 g/L (P 2 0 7 4 ~: 0.4 g/L) resin solids: 2.0 g/L of water-soluble resin 4 pH = 4.0 (adjusted with sodium hydroxide) Water-soluble resin 4 had the chemical formula: The average value of n was about 40. Water-soluble resin 4 was synthesized as follows: 50 g of poly{4-vinylphenol> (molecular weight = about 5,000) was placed in a 1,000 mL reaction flask equipped with a condenser, nitrogen inlet tube, overhead stirrer, and ther¬ mometer, and 500 g of 1,4-dioxane was added for dissolu- tion. An amount of 80 g of liquid sulfur trioxide (SO_) was added over a time of 1 hour while the mixture was main¬ tained at around 10° C. This was followed by heating to 80° C and reaction for 4 hours while stirring. Neutrali¬ zation was carried out with 10 % sodium hydroxide solution and the solvent was distilled off. The results of the experiments and comparison experi¬ ments on tin plated DI cans are reported in Table l, and they confirm that the conditions according to the present invention afford an excellent corrosion resistance, adhes- iveness, and slideability, with all these factors being superior to those obtained in the comparison examples. An aluminum DI can was cleaned as described above, then sprayed with surface-treatment liquid composition 12 as described below, heated to 60 ° C, for 30 seconds, then washed with tap water, sprayed with de-ionized water (with a specific resistance of at least 3,000,000 ohm*cm) for 10 seconds, and, finally, dried in a hot air-drying oven at 180 ° C for 3 minutes. Surface-treatment liquid composition 12 75% phosphoric acid (H 3 P0 4 ) : 10.0 g/L (P0 4 3 ~: 7.2 g/L) sodium pyrophosphate (Na P 0 «10H_0) : 3.0 g/L (P 2 0 7 4_ : 1.2 g/L) resin solids: 2.0 g/L of water-soluble resin 1, in which n in the general formula given above for this resin averaged 40, half of the total of the X's and Y's in the formula were Z, and Z was -CH 2 N(CH 3 )CH 2 CH 2 0H pH = 4.0 (adjusted with sodium hydroxide) Water-soluble resin 1 was the same as in Example 1 Example 9 An aluminum DI can was cleaned using the same condi¬ tions as in Example 8 and was then treated with a 30 second spray of surface-treatment liquid composition 13, heated to 60 ° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 13 75% phosphoric acid (H 3 P0 4 ) : 10.0 g/L (P0 4 3 ~: 7.2 g/L) sodium pyrophosphate (Na 4 P_0 7 «10H ? 0) : 3.0 g/L (P 2 0 7 4 ~: 1.2 g/L) resin solids: 0.4 g/L of water soluble resin 1 as in Example 1 pH = 5.0 (adjusted with sodium carbonate) Example 10 An aluminum DI can was cleaned using the same condi- tions as in Example 8 and was then treated with a 30 second spray of surface-treatment liquid composition 14 heated to 60 ° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 14 75% phosphoric acid (H 3 P0 4 ) : 20.0 g/L (P0 4 3 ~: 14.4.g/L) sodium pyrophosphate (Na P O 7 «10H 0) : 6.0 g/L (P 2 0 7 _ : 2.4 g/L) resin solids: 8.0 g/L of water-soluble resin 1 as in Example 1 pH = 6.0 (adjusted with sodium hydroxide) Example 11 An aluminum DI can was cleaned using the same condi¬ tions as in Example 8 and was then treated with a 30 second spray of surface-treatment liquid composition 15 heated to 60 ° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 15 75% phosphoric acid (H 3 P0 4 ) : 15.0 g/L (P0 4 3_ : 10.9 g/L) sodium pyrophosphate (Na.P O„ ' 10H 2 O) : 5.0 g/L (P 2 0 7 4" : 2.0 g/L) resin solids: 4.0 g/L of water-soluble resin l as in Example 1 pH = 3.0 (adjusted with sodium carbonate) Example 12 An aluminum DI can was cleaned using the same condi¬ tions as in Example 8 and was then treated with a 30 sec¬ ond spray of surface-treatment liquid composition 16 heated to 60 ° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 16 75% phosphoric acid (H 3 P0 4 ) : 30.0 g/L (P0 4 3_ : 21.6 g/L) sodiu tripolyphosphate (Na 5 P 3 0 Q ) : 1.2 g/L resin solids: 2.0 g/L of water-soluble resin 1 as in Example 1 pH = 3.5 (adjusted with sodium hydroxide) Example 13 An aluminum DI can was cleaned using the same condi¬ tions as in Example 8 and was then treated with a 30 second spray of surface-treatment liquid composition 17 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 17 75% phosphoric acid (H 3 P0 ) : 10.0 g/L (P0 4 3_ : 7.2 g/L) sodium pyrophosphate (Na.P O.-IOH.O): 3.0 g/L (P 2 0 7 4" : 1.2 g/L) resin solids: 2.0 g/L of water-soluble resin 2 pH = 4.0 (adjusted with sodium hydroxide) Water soluble resin 2 was made in the same way as in Example 6. Example 14 An aluminum DI can was cleaned using the same condi- tions as in Example 8 and was then treated with a 30 second spray of surface-treatment liquid composition 18 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 18 75% phosphoric acid (H.,P0 4 ) : 10.0 g/L (P0 4 3 ~: 7.2 g/L) sodium pyrophosphate (Na 4 P_0 ? 'lOH-O) : 3.0 g/L (P 2 0 7 4 ~: 1.2 g/L) resin solids: 2.0 g/L of water-soluble resin 3 ' pH = 4.0 (adjusted with sodium hydroxide) Water soluble resin 3 was made in the same way as in Example 7. Comparison Example 5 An aluminum DI can was cleaned using the same condi- tions as in Example 8 and was then treated with a 30 second spray of surface-treatment liquid composition 19 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 19 75% phosphoric acid (H PO.) : 10.0 g/L (P0 4 3_ : 7.2 g/L) resin solids: 2.0 g/L of the same water-soluble resin as in Example 1. pH = 4.0 (adjusted with sodium carbonate) Comparison Example 6 An aluminum DI can was cleaned using the same condi¬ tions as in Example 8 and was then treated with a 30 second spray of surface-treatment liquid composition 20 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 20 75% phosphoric acid (H 3 P0 4 ) : 1.0 g/L (P0 4 3" : 0.72 g/L) resin solids: 2.0 g/L of the same water-soluble resin as in Example 1 pH = 7.0 (adjusted with sodium hydroxide) Comparison Example 7 An aluminum DI can was cleaned using the same condi¬ tions as in Example 8 and was then treated with a 30 second spray of surface-treatment liquid composition 21 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example l. Surface-treatment liquid composition 21 75% phosphoric acid (H 3 P0 4 ) : 10.0 g/L (P0 4 3" : 7.2 g/L) sodium pyrophosphate (Na.P 2 0 •lOH-O) : 1.0 g/L (P 2 0 7 4" : 0.4 g/L) resin solids: 0.05 g/L of the same water-soluble resin as in Example 1 pH = 4.0 (adjusted with sodium carbonate) Comparison Example 8 An aluminum DI can was cleaned using the same condi¬ tions as in Example 8 and was then treated with a 30 second spray of surface-treatment liquid composition 22 heated to 60° C. This treatment was followed with a water wash and drying using the same conditions as in Example 1. Surface-treatment liquid composition 22 75% phosphoric acid (H 3 P0 4 ) : 1.0 g/L (P0 4 3' : 0.72 g/L) sodium pyrophosphate (N 4 P 2 0 7 *10H 2 0) : l.o g/L (P 2 0 7 4_ : 0.4 g/L) resin solids: 2.0 g/L of water-soluble resin 4 pH = 4.0 (adjusted with sodium hydroxide) Water-soluble resin 4 was the same as for Comparison Example 4 above. Comparison Example 5 An aluminum DI can was cleaned under the same condi¬ tions as in Example 8 and was then treated with a 30 second spray of a 2 % aqueous solution (heated to 50° C) of a com- merci .al non-chromate agent (PARCOAT_M K 3761, from Ni•hon Parkerizing Company, Ltd.). This treatment was followed by a water wash and drying under the same conditions as in Example 1. The results of these examples and comparison examples on aluminum substrates are shown in Table 2. Benefits of the Invention Treatment of tin-plated or aluminum DI cans using a surface-treatment liquid composition with the composition given above imparts an excellent corrosion resistance and painting or printing. In addition, it also produces a film which has the excellent slideability necessary for smooth conveyor transport of the can. Moreover, when the condensed phosphate ions comprises at least one selection from pyrophosphate ions, tripoly- phosphate ions, and tetrapolyphosphate ions and when: H or a film is produced which evidences an even greater im¬ provement in the corrosion resistance, paint adhesiveness, and slideability. The treatment solution according to this invention is substantially free from chromium and fluoride and therefore has relatively low pollution potential.

Claims: CLAIMS 1. An aqueous liquid composition for treating the surface of tin-plated steel or of aluminum, said composition having a pH in the range from 2.0 to 6.5 and comprising: (A) from 1 to 30 g/L of phosphate ions, (B) from 0.1 to 5 g/L of condensed phosphate ions if used for tin-plated steel or from 0.1 to 10 g/L if used for aluminum, and (C) from 0.1 to 20 g/L as solids of a water-soluble resin component selected from the group of resins, including mixtures of resins, having the general chemical form¬ ula: —(CH—CH 2 ) n — wherein n is an integer within the range from 10 to 80 inclusive; each of X and Y is independently selected from hydrogen or a group "Z" with the formula given below, except that at least 15 % the total of all of the X and Y groups in this component of the composi¬ tion are Z rather than hydrogen; and R / z = C —N \ R wherein each of R and R 2 in each of the Z groups in the formula independently is selected from the group consisting of alkyl groups containing from 1 to 10 carbon atoms per group and hydroxyalkyl groups con¬ taining from 1 to 10 carbon atoms per group. 2. A liquid composition according to claim 1, wherein component (B) is selected from the group consisting of py¬ rophosphate ions, tripolyphosphate ions, tetrapolyphos- phate ions, and mixtures thereof. 3. A liquid composition according to claim 2, wherein, in the general chemical formula for the water soluble resin component, or 4. A liquid composition according to claim 1, wherein, in the general chemical formula for the water soluble resin component, or z = 5. A liquid composition according to claim 4, comprising from 5 to 15 g/L of component (A) . 6. A liquid composition according to claim 3, comprising from 5 to 15 g/L of component (A) . 7. A li.quid composi.tion according to claim 2, comprising from 5 to 15 g/L of component (A) . 8. A liquid composition according to claim 1, comprising from 5 to 15 g/L of component (A) . 9. A liquid composition according to claim 8, comprising from 0.4 to 1 g/L of component (B) when used on tin-plated steel or from 1.0 to 4.0 g/L of component (B) when used on aluminum. 10. A liquid composition according to claim 7, comprising from 0.4 to 1 g/L of component (B) when used on tin-plated steel or from 1.0 to 4.0 g/L of component (B) when used on aluminum. 11. A liquid composition according to claim 6, comprising from 0.4 to 1 g/L of component (B) when used on tin-plated steel or from 1.0 to 4.0 g/L of component (B) when used on aluminum. 12. A liquid composition according to claim 5, comprising from 0.4 to 1 g/L of component (B) when used on tin-plated steel or from 1.0 to 4.0 g/L of component (B) when used on aluminum. 13. A liquid composition according to claim 4, comprising from 0.4 to 1 g/L of component (B) when used on tin-plated steel or from 1.0 to 4.0 g/L of component (B) when used on aluminum. 14. A liquid composition according to claim 3, comprising from 0.4 to 1 g/L of component (B) when used on tin-plated steel or from 1.0 to 4.0 g/L of component (B) when used on aluminum. 15. A liquid composition according to claim 2, comprising from 0.4 to 1 g/L of component (B) when used on tin-plated steel or from 1.0 to 4.0 g/L of component (B) when used on aluminum. 16. A liquid composition according to claim 1, comprising from 0.4 to 1 g/L of component (B) when used on tin-plated steel or from 1.0 to 4.0 g/L of component (B) when used on aluminum. 17. A process for treating a drawn and ironed tin-plated steel or aluminum metal container by contact with an aque¬ ous liquid composition in order to form on the surface of the metal container a conversion coating layer that will increase the corrosion resistance of the container after subsequent painting or printing, characterized in that the aqueous liquid composition has a composition according to one of claim 1 - 16. 18. A process according to claim 17, wherein the time of contact is within the range from 2 to 60 seconds, contact is by spraying, and the temperature of the liquid co posi- tion during contact is between 20 and 80 ° C. 19. A process according to claim 18, wherein the temper¬ ature of the liquid composition during contact is between 40 and 60 ° C. 20. A process according to claim 19, comprising additional steps of first degreasing and then tap water washing the container surface before contacting with the aqueous liquid composition and, in order, tap water washing, washing with deionized water, and drying after contact with the aqueous liquid. 21. A process according to claim 18, comprising additional steps of first degreasing and then tap water washing the container surface before contacting with the aqueous liquid composition and, in order, tap water washing, washing with deionized water, and drying after contact with the aqueous liquid. 22. A process according to claim 17, comprising additional steps of first degreasing and then tap water washing the container surface before contacting with the aqueous liquid composition and, in order, tap water washing, washing with deionized water, and drying after contact with the aqueous liquid.

Inventors: AOKI TOMOYUKI, ASAI SHINICHIRO, IINO YASUO, TANAKA SHIGEO, YOSHIDA MASAYUKI, AOKI, TOMOYUKI, ASAI, SHINICHIRO, IINO, YASUO, TANAKA, SHIGEO, YOSHIDA, MASAYUKI
Applicants: HENKEL CORP, HENKEL CORPORATION
Application year: 1991
Main classification: C23C22
IPC codes: C23C22