Laminated steel having extremely low interface bubble rate and method for manufacturing same

Abstract

Laminated steel having a low interface bubble rate, comprising: a substrate with a surface roughness of 0.15-0.25 μm and a modified flexible polyester film thermally laminated onto the surface of the substrate. The modified flexible polyester film is obtained by copolymerization modification of ethylene terephthalate with a low-molecular-weight aliphatic polyester. A method for manufacturing the laminated steel having an extremely low interface bubble rate, comprising the steps of: (1) preheating and then heating the substrate; (2) uncoiling the modified flexible polyester film at room temperature, and then thermally laminating same onto the substrate; and (3) cooling and squeeze-drying. The laminated steel having a low interface bubble rate is made of the substrate with a low surface roughness and the modified flexible polyester thermally laminated onto the surface of the substrate, so that the laminated steel has the low interface bubble rate, high product surface quality, excellent adhesion property, and is applicable for forming into deep-drawn containers.

Claims

1. A film-laminated steel comprising: a substrate having a surface roughness of 0.15-0.25 μm and a modified flexible polyester film thermally laminated to a surface of the substrate, wherein the modified flexible polyester film is obtained by copolymerization modification of ethylene terephthalate with a hydroxy-terminated low-molecular-weight aliphatic polyester.

2. The film-laminated steel according to claim 1, wherein the hydroxy-terminated low-molecular-weight aliphatic polyester has a molar percentage of 6-17%.

3. The film-laminated steel according to claim 1, wherein the hydroxy-terminated low-molecular-weight aliphatic polyester has a molecular weight of 500-3000.

4. The film-laminated steel according to claim 1, wherein the hydroxy-terminated low-molecular-weight aliphatic polyester is prepared from an aliphatic diol and an aliphatic diprotic acid.

5. The film-laminated steel according to claim 4, wherein the aliphatic diol is selected from the group consisting of propanediol, butanediol, pentanediol, hexanediol, and neopentanediol.

6. The film-laminated steel according to claim 4, wherein the aliphatic diprotic acid is selected from the group consisting of oxalic acid, succinic acid, adipic acid, sebacic acid, decane dicarboxylic acid, maleic acid, fumaric acid and dimer acid.

7. The film-laminated steel according to claim 1, wherein the substrate is a tin-plated substrate or a chrome-plated substrate.

8. The film-laminated steel according to claim 1, wherein the film-laminated steel has an interface bubble rate of 2-7%.

9. The film-laminated steel according to claim 1, wherein the modified flexible polyester film has a mono-layer or multi-layer structure.

10. The film-laminated steel according to claim 1, wherein a surface of the modified flexible polyester film to be laminated to the substrate has a surface tension of ≥45 dyne.

11. A manufacturing method for the film-laminated steel according to claim 1, comprising steps: (1) preheating a substrate and then heating it; (2) uncoiling a modified flexible polyester film at room temperature, and then laminating the film to the substrate; and (3) cooling and squeeze-drying.

12. The manufacturing method according to claim 11, wherein in step (1), an induction heater is first used to preheat the substrate to 60-80% of a target film-laminating temperature, and then an induction heating roll is used to heat the substrate to the target film-laminating temperature.

13. The manufacturing method according to claim 11, wherein the target film-laminating temperature is 180-270° C.

14. The manufacturing method according to claim 12, wherein in step (2), an angle at which the modified flexible polyester film enters a roll gap between film-laminating rolls is controlled in the range of 30-70° C.

15. The manufacturing method according to claim 11, wherein in step (2), a film-laminating speed is controlled in the range of ≥150 m/min.

16. The manufacturing method according to claim 11, wherein in step (3), during cooling, the film-laminated steel is quickly cooled by spraying water, and then the film-laminated steel is immersed in a water quenching tank for cooling.

17. The manufacturing method according to claim 11, wherein the hydroxy-terminated low-molecular-weight aliphatic polyester of the film-laminated steel has a molar percentage of 6-17%, or a molecular weight of 500-3000.

18. The manufacturing method according to claim 11, wherein the hydroxy-terminated low-molecular-weight aliphatic polyester is prepared from an aliphatic diol and an aliphatic diprotic acid, wherein the aliphatic diol is selected from the group consisting of propanediol, butanediol, pentanediol, hexanediol, and neopentanediol, and the aliphatic diprotic acid is selected from the group consisting of oxalic acid, succinic acid, adipic acid, sebacic acid, decane dicarboxylic acid, maleic acid, fumaric acid and dimer acid.

19. The manufacturing method according to claim 11, wherein the substrate is a tin-plated substrate or a chrome-plated substrate, the film-laminated steel has an interface bubble rate of 2-7%, the modified flexible polyester film has a mono-layer or multi-layer structure, and/or a surface of the modified flexible polyester film to be laminated to the substrate has a surface tension of ≥45 dyne.

Description

DETAILED DESCRIPTION

(1) The film-laminated steel having an extremely low interface bubble rate according to the present disclosure and the method for manufacturing the same will be further explained and illustrated with reference to the specific examples. Nonetheless, the explanation and illustration are not intended to unduly limit the technical solution of the disclosure.

Examples 1-6 and Comparative Examples 1-4

(2) Table 1 lists the types of substrates and their surface roughness used for the film-laminated steel having an extremely low interface bubble rate in Examples 1-6 and the comparative film-laminated steel in Comparative Examples 1-4.

(3) TABLE-US-00001 TABLE 1 Surface Roughness (μm) Substrate Type Ex. 1 0.186 Chrome-plated substrate Ex. 2 0.232 Chrome-plated substrate Ex. 3 0.186 Chrome-plated substrate Ex. 4 0.232 Chrome-plated substrate Ex. 5 0.186 Tin-plated substrate Ex. 6 0.232 Tin-plated substrate Comp. Ex. 1 0.261 Chrome-plated substrate Comp. Ex. 2 0.365 Chrome-plated substrate Comp. Ex. 3 0.281 Chrome-plated substrate Comp. Ex. 4 0.375 Tin-plated substrate

(4) The flexible polyester films used for the film-laminated steel having an extremely low interface bubble rate in Example 1-6 were obtained by copolymerization modification of ethylene terephthalate with low-molecular-weight aliphatic polyesters. The films used for the comparative film-laminated steel in Comparative Examples 1-4 were mono-layer polyester flexible films obtained by copolymerization modification of ethylene terephthalate with hydroxy-terminated butanediol adipate (having a molecular weight of 1000, the same as the flexible polyester film used in Example 2).

(5) Table 2 lists the specific parameters of the modified flexible polyester films used for the film-laminated steel having an extremely low interface bubble rate in Examples 1-6.

(6) TABLE-US-00002 TABLE 2 Molar Molecular percentage weight of Low- of low- low- Structure molecular- molecular- molecular- of weight weight weight flexible Surface aliphatic aliphatic aliphatic polyester tension polyester polyester polyester film (dyne) Ex. Propanediol 7 500 Mono- 50 1 adipate layer structure Ex. Butanediol 10 1000 Mono- 50 2 adipate layer structure Ex. Hexanediol 10 1500 Mono- 47 3 adipate layer structure Ex. Butanediol 10 1500 Multi- 46 4 maleate layer structure Ex. Pentanediol 15 2000 Multi- 48 5 sebacate layer structure Ex. Butanediol 17 2500 Multi- 45 6 decane layer dicarboxylate structure Note: The low-molecular-weight aliphatic polyesters in Table 2 are all hydroxy-terminated low-molecular-weight aliphatic polyesters.

(7) The method for manufacturing the film-laminated steel having an extremely low interface bubble rate in Examples 1-6 and the comparative film-laminated steel in Comparative Examples 1-4 includes the following steps:

(8) (1) preheating a substrate listed in Table 1 and then heating it, wherein an induction heater was used to preheat the substrate to 60-80% of the target film-laminating temperature, and then an induction heating roll was used to heat the substrate to the target film-laminating temperature, wherein the target film-laminating temperature was 180-270° C.;

(9) (2) uncoiling the film at room temperature, and then thermally laminating a modified flexible polyester film listed in Table 2 to the substrate, wherein an angle at which the modified flexible polyester film entered a roll gap between film-laminating rolls was controlled to be 30-70°, and a film-laminating speed was ≥150 m/min; and

(10) (3) cooling and squeeze-dry: during cooling, the film-laminated steel was quickly cooled by spraying water, and then the film-laminated steel was immersed in a water quenching tank for cooling.

(11) Table 3 lists the specific process parameters for the method for manufacturing the film-laminated steel having an extremely low interface bubble rate in Examples 1-6 and the comparative film-laminated steel in Comparative Examples 1-4.

(12) TABLE-US-00003 TABLE 3 Target Angle of entry film- into roll gap Film- Final laminating between film- laminating cooling temperature laminating speed temperature (° C.) rolls (°) (m/min) (° C.) Ex. 1 180 30 150 80 Ex. 2 210 50 150 80 Ex. 3 225 50 180 80 Ex. 4 225 50 180 80 Ex. 5 225 60 200 80 Ex. 6 270 70 200 80 Comp. 210 50 150 80 Ex. 1 Comp. 210 50 150 80 Ex. 2 Comp. 210 50 200 80 Ex. 3 Comp. 210 50 200 80 Ex. 4

(13) Performance tests were performed on the film-laminated steel having an extremely low interface bubble rate in Examples 1-6 and the comparative film-laminated steel in Comparative Examples 1-4 using the following test methods. The test results finally obtained are listed in Table 4.

(14) Interface bubble rate: A laminate was observed with a high-resolution metallurgical microscope, wherein the bubble-like parts were viewed as the bubble. The area ratio of the bubble per unit area was calculated.

(15) Surface adhesion performance: Adhesion force after deformation was measured using a crosshatch-cupping-tape peeling method. A 10 cm×10 cm sample was taken from the film-laminated steel. A checkerboard pattern was scored on the flat sheet at intervals of 3 mm. After the film was cut through (care should be taken not to cut the substrate), the film was deformed by cupping, wherein the highest point of the punch was kept in the central zone of a check. Then, a specialized adhesive tape was intimately adhered to the scribed and cupped zone. The tape was peeled off by gripping an end of the tape and pulling rapidly in an inclined upward direction. The degree to which the film was released was observed to evaluate the surface adhesion performance of the film.

(16) Acid resistance performance: After the film-laminated steel was stamped into a can (can size 691), acid resistance performance evaluation was performed to represent corrosion resistance performance evaluation. The film-laminated steel can was filled with a 1.5% citric acid solution. After the can was capped, the solution was boiled at 121° C. for 30 min. After cooling, the sample was taken out, and spots corroded by the acid on the surface of the sample were observed to evaluate the acid resistance performance of the film-laminated steel.

(17) TABLE-US-00004 TABLE 4 Interface Surface Acid bubble adhesion resistance rate (%) performance performance Ex. 1 2 ⊚ ⊚ Ex. 2 5 ⊚ ⊚ Ex. 3 3 ⊚ ⊚ Ex. 4 6 ⊚ ◯ Ex. 5 5 ⊚ ◯ Ex. 6 7 ◯ ◯ Comp. 10 Δ Δ Ex. 1 Comp. 13 Δ Δ Ex. 2 Comp. 18 Δ X Ex. 3 Comp. 20 X X Ex. 4 Note: in Table 4, X means poor; Δ means fair; ◯ means good; ⊚ means very good.

(18) As can be seen from Table 4, the interface bubble rate of the film-laminated steel in the various examples of the present case is 2-7%, which is significantly lower than that of the comparative film-laminated steel of the various comparative examples, thus illustrating that the interface bubble rate of the film-laminated steel in the various examples of the present case is extremely low. In addition, the film-laminated steel in the various examples of the present case exhibits higher surface performances due to the extremely low interface bubble rate, especially in terms of surface adhesion performance and acid resistance performance, which are superior to the performances of the comparative film-laminated steel in the various comparative examples. This is because substrates having an extremely low roughness are used in the various examples of the present case, and thus the interface bubble rate can be maintained between 2% and 7% at a high speed of film lamination. Therefore, at the same speed, the bubble rate of the comparative film-laminated steel in the various comparative examples having a surface roughness that is higher than the surface roughness in the examples of the present case is significantly higher. Meanwhile, with the increase of the interface bubble rate, the surface adhesion performance of the highly deformed comparative film-laminated steel in the various comparative examples is gradually deteriorated. In the case of high deformation, bubbles will be stretched with the deformation. That is, the defects are magnified. In the acid resistance test where the can is filled with an acid and simulated cooking is performed, defects are spotted more strictly. As shown by Table 4, with the increase of the surface bubble rate, the acid resistance of the comparative film-laminated steel in the various comparative examples is gradually deteriorated. This indicates that, in order to obtain a film-laminated steel exhibiting better performances in applications involving high deformation, the interface bubble rate of the film-laminated steel should be controlled more strictly. The interface bubble rate of the film-laminated steel in the various examples of the present case is extremely low, and high surface performances are obtained.

(19) It's to be noted that the prior art portions in the protection scope of the present disclosure are not limited to the examples set forth in the present application file. All the prior art contents not contradictory to the technical solution of the present disclosure, including but not limited to prior patent literature, prior publications, prior public uses and the like, may all be incorporated into the protection scope of the present disclosure.

(20) In addition, the ways in which the various technical features of the present disclosure are combined are not limited to the ways recited in the claims of the present disclosure or the ways described in the specific examples. All the technical features recited in the present disclosure may be combined or integrated freely in any manner, unless contradictions are resulted.

(21) It should also be noted that the Examples set forth above are only specific examples according to the present disclosure. Obviously, the present disclosure is not limited to the above Examples. Similar variations or modifications made thereto can be directly derived or easily contemplated from the present disclosure by those skilled in the art. They all fall in the protection scope of the present disclosure.