Resin-coated A1 plate for drawn and ironed can with excellent luster and method for producing drawn and ironed can

Abstract

Disclosed is a resin-coated Al sheet with which a drawn and ironed can having a lustrous appearance can be formed. An upper limit of a thickness of an outer surface resin layer which covers an Al surface which becomes an outer surface of the can and has an arithmetical mean roughness (Ra) of 0.5 m or less with a thickness which falls within a range of 0.02 m to 6 m is determined based on an arithmetical mean roughness (Ra) of the Al surface, wherein the upper limit of the thickness of a coating outer-surface resin layer is decreased when the arithmetical mean roughness (Ra) is increased.

Claims

1. A resin-coated Al sheet for a drawn and ironed can exhibiting excellent luster, the resin-coated Al sheet to be formed into a can body by drawing and ironing, wherein an Al surface which forms an outer surface of the can and has an arithmetical mean roughness (Ra) of 0.5 m or less is covered with an outer surface resin layer having a thickness which falls within a range of 0.1 m to 2 m, the resin layer having a Martens hardness of 50 N/mm.sup.2 or more at 28 C. and a rapture elongation of 5% or more at 25 C. when measured in accordance with ASTM, D-882, and wherein a glass transition temperature of the outer surface resin layer is 40 C. or more; a regular reflectance of the outer surface of the drawn and ironed can is 28.4% or more; and wherein the Al surface has a plurality of recesses and protrusions where the recesses and the protrusions define a surface roughness profile and where the surface roughness profile has a center line; a number of unique pairs of recesses and protrusions meeting a criteria is no more than 10/mm, wherein the criteria for the unique pair is defined by the recess of the unique pair extending at least 0.1 m beneath the center line and the protrusion of the unique pair is when a following protrusion extends above the center line, such that each recess and protrusion belonging to the unique pair meeting the criteria is counted only once.

2. A method of manufacturing a drawn and ironed can exhibiting excellent luster, wherein a resin-coated Al sheet in which an Al surface which forms an outer surface of the can and has an arithmetical mean roughness (Ra) of 0.5 m or less is covered with an outer surface resin layer having a thickness which falls within a range of 0.02 m to 2 m, a Martens hardness of 50 N/mm.sup.2 or more at 28 C. and a rapture elongation of 5% or more at 25 C. when measured in accordance with ASTM, D-882, a glass transition temperature of 40 C. or more; is subjected to drawing and ironing thus forming the resin-coated Al sheet into a can body, wherein the drawing and ironing are performed such that regular reflectance of a barrel portion of the can body after working is 15% or more; and wherein the Al surface has a plurality of recesses and protrusions where the recesses and the protrusions define a surface roughness profile and where the surface roughness profile has a center line; a number of unique pairs of recesses and protrusions meeting a criteria is no more than 10/mm, wherein the criteria is defined by the recess of the unique pair extending at least 0.1 m beneath the center line and the protrusion of the unique pair is when a following protrusion extends above the center line, such that each recess and protrusion belonging to the unique pair meeting the criteria is counted only once.

Description

EXAMPLES

(1) The present invention is explained in detail hereinafter in conjunction with examples.

(2) (Evaluation Item)

(3) [Regular Reflectance of Barrel Portion]

(4) The barrel portion is cut out in the circumferential direction from the formed drawn and ironed can, wherein the cut-out barrel portion has a width of 20 mm starting from a position of 60 mm in height direction from a can bottom of the formed drawn can. The cut-out barrel portion having the width of 20 mm is cut in the can height direction such that the barrel portion is equally divided into eight pieces, and each divided piece is used as a measuring sample.

(5) With respect to a center portion of the measuring sample, using a spectral colorimeter (made by KONICA MINOLTA HOLDINGS, INC., type: CM-3500), total reflectance and diffuse reflectance are measured, and regular reflectance is calculated using a following formula.
regular reflectance (%)=total reflectance (%)diffuse reflectance (%)

(6) An average value of the regular reflectances of 8-equally-divided samples is calculated by rounding-off, and the rounded-off value is used as the regular reflectance of the barrel portion described in the examples and comparison examples.

(7) According to the present invention, by taking into account a recent demand for strong luster, it is determined that the barrel portion having the regular reflectance of 15% or more, preferably 25% or more has practicability. Further, the barrel portion having the regular reflectance of 40% or more is more preferable because that the barrel portion acquires the substantially equal luster as a can which exhibits favorable lustrous appearance among conventional formed cans made of a non-precoating material.

Example 1

(8) Chromate-phosphate treatment (16 mg/cm.sup.2 in terms of Cr) is applied to surfaces of an Al sheet (sheet thickness: 0.28 mm: 3104 alloy material) which becomes inner and outer surfaces of a can thus producing an Al sheet where the surface which becomes the outer surface of the can has an arithmetical mean roughness (Ra) of 0.50 m and the number of peaks of recessed portions having a depth of 0.1 m or more is 52 pieces/mm. The Al sheet is heated to a sheet temperature of 220 C., and a non-stretched isophthalic acid/terephthalic acid copolymer polyester film (melting point: 210 C., film thickness: 12 m) made by Toyo Kohan Co., Ltd. is applied to the surface of the Al sheet which becomes the inner surface of the can by coating and is cooled thus forming an inner surface resin layer, and urethane modified polyester resin having a glass transition temperature of 106 C. shown in Table 1 is applied to the surface of the Al sheet which becomes the outer surface of the can as a paint such that a dry thickness of the resin film becomes 2 m and, thereafter, the resin film is dried at a temperature of 150 C. for 30 seconds thus forming an outer surface resin layer whereby a resin coated Al sheet is obtained.

(9) 50 mg/m.sup.2 of glamour wax is applied to both surfaces of the resin coated Al sheet and, thereafter, drawing and ironing are applied to the resin coated Al sheet in dry atmosphere under the following forming conditions such that the inner surface of the can becomes the surface coated with the copolymer polyester film made by Toyo Kohan Co., Ltd. thus obtaining a drawn and ironed can.

(10) A result obtained by measuring regular reflectance of an outer surface of the drawn and ironed can by the above-mentioned method is shown in Table 1, wherein the regular reflectance of a can barrel portion is 17.2% so that the drawn and ironed can acquires favorable lustrous appearance.

(11) <Drawing and Ironing Conditions>

(12) 1. forming temperature: temperature of a punch immediately before forming: 45 C.

(13) 2. die temperature: 40 C.

(14) 3. blank diameter: 142 mm

(15) 4. drawing condition: 1.sup.st drawing ratio: 1.56, second drawing ratio: 1.38

(16) 5. ironing punch diameter: 66 mm

(17) 6. total ironing ratio: 63% (center portion of side wall)

(18) 7. can forming speed: 200 cpm

Example 2

(19) Except for that a thickness of an outer surface coating film is set to 0.25 m as shown in Table 1, a resin coated Al sheet is prepared in the same manner as the example 1, and drawing and ironing are applied to the resin coated Al sheet in the same manner as the example 1 thus obtaining a drawn and ironed can.

(20) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 1, wherein a can barrel portion exhibits regular reflectance of 38.2% which is far higher than the regular reflectance of the can barrel portion in the example 1 due to the reduction of a film thickness of the outer surface coating film so that the drawn and ironed can acquires favorable lustrous appearance.

Example 3

(21) Except for that an Al sheet where an arithmetical mean roughness (Ra) is 0.3 m and the number of peaks of the recessed portion is 45 pieces/mm is used, a resin coated Al sheet is prepared in the same manner as the example 1, and drawing and ironing are applied to the resin coated Al sheet in the same manner as the example 1 thus obtaining a drawn and ironed can.

(22) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 1, wherein a can barrel portion exhibits regular reflectance of 22.5% which is higher than the regular reflectance of the can barrel portion in the example 1 due to smoothing of the Al sheet so that the drawn and ironed can acquires favorable lustrous appearance.

Example 4

(23) Except for that an Al sheet where an arithmetical mean roughness (Ra) is 0.25 m and the number of peaks of the recessed portion is 43 pieces/mm is used, a resin coated Al sheet is prepared in the same manner as the example 1, and drawing and ironing are applied to the resin coated Al sheet in the same manner as the example 1 thus obtaining a drawn and ironed can.

(24) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 1, wherein a can barrel portion exhibits regular reflectance of 25.8% which is higher than the regular reflectance of the can barrel portion in the example 1 due to smoothing of the Al sheet so that the drawn and ironed can acquires favorable lustrous appearance.

Example 5

(25) Except for that an Al sheet where a thickness of an outer surface resin layer is 4 m is used, a resin coated Al sheet is prepared in the same manner as the example 4, and drawing and ironing are applied to the resin coated Al sheet in the same manner as the example 1 thus obtaining a drawn and ironed can.

(26) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 1, wherein although a can barrel portion exhibits regular reflectance lower than the regular reflectance in the example 4 due to the increase of a film thickness of an outer surface coating film, the can barrel portion exhibits regular reflectance of 20.5% so that the drawn and ironed can acquires favorable lustrous appearance.

Embodiments 6 to 8

(27) Except for that an Al sheet where an arithmetical mean roughness (Ra) is 0.2 m and the number of peaks of the recessed portion is 40 pieces/mm is used and a thickness of an outer surface resin layer is set to 2 m, 4 m and 0.25 m respectively as shown in Table 1, a resin coated Al sheet is prepared in the same manner as the example 1, and drawing and ironing are applied to the resin coated Al sheet in the same manner as the example 1 thus obtaining a drawn and ironed can.

(28) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 1, wherein can barrel portions exhibit regular reflectances of 27.8%, 18.7%, 42.2% respectively so that the drawn and ironed cans acquire favorable lustrous appearance respectively.

Embodiments 9 to 11

(29) Except for that an Al sheet where an arithmetical mean roughness (Ra) is 0.15 m and the number of peaks of the recessed portion is 38 pieces/mm is used and a thickness of an outer surface resin layer is set to 6 m, 2 m and 0.25 m respectively as shown in Table 1, a resin coated Al sheet is prepared in the same manner as the example 1, and drawing and ironing are applied to the resin coated Al sheet in the same manner as the example 1 thus obtaining a drawn and ironed can.

(30) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 1, wherein can barrel portions exhibit regular reflectances of 16.5%, 28.4%, 45.3% respectively so that the drawn and ironed cans acquire favorable lustrous appearance respectively.

Embodiments 12 to 13

(31) As shown in Table 1, except for that an Al sheet where an arithmetical mean roughness (Ra) is 0.03 m and the number of peaks of the recessed portion is 17 pieces/mm and 3 pieces/mm is used, a resin coated Al sheet is prepared in the same manner as the example 11, and drawing and ironing are applied to the resin coated Al sheet in the same manner as the example 1 thus obtaining a drawn and ironed can.

(32) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 1, wherein can barrel portions exhibit regular reflectances of 50.4%, 56.5% respectively so that the drawn and ironed cans acquire favorable lustrous appearance respectively.

Embodiments 14 to 17

(33) Except for that, in respective embodiments, an outer surface resin layer is made of a polyester resin having a glass transition temperature of 84 C., 40 C., 18 C. or a polyether sulfone resin having a glass transition temperature of 225 C. is used, a resin coated Al sheet is prepared in the same manner as the example 12, and drawing and ironing are applied to the resin coated Al sheet in the same manner as the example 1 thus obtaining a drawn and ironed can.

(34) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 1, wherein can barrel portions exhibit regular reflectances of 44.3%, 31.6%, 21.5%, 52.2% respectively. Although there is observed tendency that the high regular reflectance is acquired when the glass transition temperature is high and the regular reflectance is lowered when the glass transition temperature is low, all drawn and ironed cans can acquire favorable lustrous appearance respectively.

Example 18

(35) Except for that a thickness of an outer surface resin layer is set to 0.1 m as shown in Table 1, a resin coated Al sheet is prepared in the same manner as the example 12, and drawing and ironing are applied to the resin coated Al sheet in the same manner as the example 1 thus obtaining a drawn and ironed can.

(36) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 1, wherein a can barrel portion exhibits regular reflectance of 53.8% so that the drawn and ironed can acquires extremely favorable lustrous appearance.

Comparison Examples 1 to 4

(37) In the comparison example 1, except for that a thickness of an outer surface resin layer is 3 m, a drawn and ironed can is obtained by applying drawing and ironing to a resin-coated Al sheet in the same manner as the example 3. In the comparison example 2, except for that a thickness of an outer surface resin layer is 5 m, a drawn and ironed can is obtained by applying drawing and ironing to resin-coated Al sheet in the same manner as the example 7. In the comparison example 3, except for that a thickness of an outer surface resin layer is 7 m, a drawn and ironed can is obtained by applying drawing and ironing to resin-coated Al sheet in the same manner as the example 9. In the comparison example 4, except for that a thickness of an outer surface resin layer is 7 m, a drawn and ironed can is obtained by applying drawing and ironing to a resin-coated Al sheet in the same manner as the example 17.

(38) A result obtained by evaluating regular reflectance of the drawn and ironed can in the same manner as the example 1 is shown in Table 2, wherein can barrel portions exhibit regular reflectances of 13%, 12%, 9%, 9% respectively. None of drawn and ironed cans can acquire sufficient luster respectively.

(39) TABLE-US-00001 TABLE 1 Example outer surface resin layer Al glass regular number of film transition reflect- Ra peaks/mm kind of thickness temperature ance No. (m) (>0.1 m) resin (m) ( C.) (%) 1 0.5 52 urethane 2 106 17.2 modified polyester 2 0.5 52 urethane 0.25 106 38.2 modified polyester 3 0.3 45 urethane 2 106 22.5 modified polyester 4 0.25 43 urethane 2 106 25.8 modified polyester 5 0.25 43 urethane 4 106 20.5 modified polyester 6 0.2 40 urethane 2 106 27.8 modified polyester 7 0.2 40 urethane 4 106 18.7 modified polyester 8 0.2 40 urethane 0.25 106 42.2 modified polyester 9 0.15 38 urethane 6 106 16.5 modified polyester 10 0.15 38 urethane 2 106 28.4 modified polyester 11 0.15 38 urethane 0.25 106 45.3 modified polyester 12 0.03 17 urethane 0.25 106 50.4 modified polyester 13 0.03 3 urethane 0.25 106 56.5 modified polyester 14 0.03 17 polyester I 0.25 84 44.3 15 0.03 17 polyester 0.25 40 31.6 II 16 0.03 17 polyester 0.25 18 21.5 III 17 0.03 17 polyether 0.25 225 52.2 sulfone 18 0.03 17 urethane 0.1 106 53.8 modified polyester

(40) TABLE-US-00002 TABLE 2 Comparison example outer surface resin layer Al glass regular number of film transition reflect- Ra peaks/mm kind of thickness temperature ance No. (m) (>0.1 m) resin (m) ( C.) (%) 1 0.3 52 urethane 3 106 13 modified polyester 2 0.2 52 urethane 5 106 12 modified polyester 3 0.15 38 urethane 7 106 9 modified polyester 4 0.15 38 polyether 7 225 9 sulfone

INDUSTRIAL APPLICABILITY

(41) According to the resin-coated Al sheet for a drawn and ironed can and the method of manufacturing a drawn and ironed can of the present invention, the drawn and ironed can whose barrel portion exhibits the excellent luster can be formed by dry lubrication without using a liquid coolant and hence, the present invention has the extremely high industrial applicability.