Method for producing a polymer coated metal strip and polymer coated metal strip produced thereby

Patent metadata

Field	Value
Publication number	US-12042959-B2
Application number	US-201917297016-A
Country	US
Kind code	B2
Filing date	Dec 17, 2019
Priority date	Dec 21, 2018
Publication date	Jul 23, 2024
Grant date	Jul 23, 2024

Abstract

A method for producing a polymer coated metal strip in a continuous coating line, including the subsequent steps of:
laminating a thermoplastic polymer film onto at least one side of a metal strip to produce a polymer coated metal strip; post-heating the polymer coated metal strip to temperature sufficiently high to melt the thermoplastic polymer film to reduce orientation and crystallinity of the thermoplastic polymer film to target value; cooling the post-heated polymer coated metal strip; in-line illuminating the laminated polymer film with near-infrared light having one or more or all wavenumbers between 3500 and 9000 cm −1 ; in-line acquiring back-scattered near-infrared light with a near-infrared spectroscopy detector; calculating near-infrared spectrum from the back-scattered near-infrared light; comparing the calculated near-infrared spectrum to a reference material near-infrared spectrum to determine Conformity Index as measure of the laminated polymer film degree of crystallinity and/or molecular orientation.

First claim

The invention claimed is:

1. A method for producing a polymer coated metal strip in a continuous coating line, the method comprising the subsequent steps of:
providing a metal strip;
providing a thermoplastic polymer film for coating onto at least one side of the metal strip;
laminating the thermoplastic polymer film onto the metal strip to produce a polymer coated metal strip;
post-heating the polymer coated metal strip to a temperature sufficiently high to melt the thermoplastic polymer film in order to reduce the orientation and crystallinity of the thermoplastic polymer film to the target value;
cooling the post-heated polymer coated metal strip;
in-line illuminating the laminated polymer film with near-infrared light having one, more or all wavenumbers between 3500 and 9000 cm −1 ;
in-line acquiring back-scattered near-infrared light with a near-infrared spectroscopy detector;
calculating a near-infrared spectrum from the back-scattered near-infrared light;
determining the degree of crystallinity and/or the molecular orientation of the laminated polymer film by comparing the calculated near-infrared spectrum to a near-infrared spectrum of a reference material to determine a Conformity Index as a measure of the degree of crystallinity and/or the molecular orientation of the laminated polymer film.

2. The method according to claim 1 , wherein a polymer film is laminated onto both sides of the metal strip, and wherein the degree of crystallinity and/or the molecular orientation of both laminated polymer films is determined on both sides of the metal strip.

3. The method according to claim 1 , wherein the wavenumber of the infra-red light is between 3750 and 6000 cm −1 .

4. The method according to claim 1 , wherein the measured CI is lower than 0.5.

5. The method according claim 1 , wherein one or both of the post-heat set-point (T2) and the line speed of the continuous coating line is adjusted if the conformity index that is calculated on the basis of the back-scattered NIR-light is above 0.5.

6. The method according to claim 1 , wherein a plurality of near-infrared spectroscopy detectors is used to acquire back-scattered near-infrared light over the width of the strip, or wherein one or more scanning near-infrared spectroscopy detector(s) is (are) used to acquire back-scattered near-infrared light over the width of the strip.

7. The method according to claim 1 , wherein the metal strip is a steel strip.

8. The method according to claim 7 , wherein the steel strip is uncoated cold-rolled steel strip, tinplate, ECCS, TCCT, galvanised steel or aluminised steel strip.

9. The method according to claim 1 , wherein the thermoplastic polymer film is a single layer or multilayer polyester or polyolefin polymer film.

10. The method according to claim 1 , wherein the thermoplastic polymer film for coating onto the metal strip consists of two or more layers and is produced by:
melting thermoplastic polymer granules in two or more extruders to form the two or more layers;
forming the thermoplastic polymer film consisting of the two or more layers by passing the molten polymer or polymers through a flat co-extrusion die and/or two or more calendering rolls;
optionally followed by:
cooling the thermoplastic polymer film to form a solid thermoplastic polymer film;
optionally trimming the edges of the thermoplastic polymer film;
reducing the thickness of the solid thermoplastic polymer film by stretching the solid polymer film in a stretching unit by exerting a stretching force only in the longitudinal direction;
optionally trimming the edges of the stretched thermoplastic polymer film.

11. The method according to claim 1 , wherein the thermoplastic polymer film is biaxially oriented polymer film.

12. The method according to claim 1 , wherein the one or more thermoplastic polymer film is uniaxially oriented polymer film.

13. The method according to claim 1 , wherein the target value for the crystallinity of the laminated polymer film is at most 10 wt. %.

14. The method according to claim 1 , wherein the wavenumber of the infra-red light is at least 4100 cm−1.

15. The method according to claim 1 , wherein the wavenumber of the infra-red light is at most 4500 cm−1.

16. The method according to claim 1 , wherein the thermoplastic polymer film for coating onto the metal strip consists of one layer and is produced by:
melting thermoplastic polymer granules in one extruder to form the one layer;
forming the thermoplastic polymer film consisting of the one layer by passing the molten polymer or polymers through a flat extrusion die and/or two or more calendering rolls;
optionally followed by:
cooling the thermoplastic polymer film to form a solid thermoplastic polymer film;
optionally trimming the edges of the thermoplastic polymer film;
reducing the thickness of the solid thermoplastic polymer film by stretching the solid polymer film in a stretching unit by exerting a stretching force only in the longitudinal direction;
optionally trimming the edges of the stretched thermoplastic polymer film.

17. A method for producing a polymer coated metal strip in a continuous coating line, the method comprising the subsequent steps of:
providing a metal strip;
providing one or more thermoplastic polymer films for coating onto at least one side of the metal strip;
laminating the one or more thermoplastic polymer films onto the metal strip to produce a polymer coated metal strip;
post-heating the polymer coated metal strip to a temperature sufficiently high to melt the one or more thermoplastic polymer films in order to reduce the orientation and crystallinity of the one or more thermoplastic polymer films to the target value;
cooling the post-heated polymer coated metal strip;
in-line illuminating the one or more laminated polymer films with near-infrared light having one, more or all wavenumbers between 3500 and 9000 cm −1 ;
in-line acquiring back-scattered near-infrared light with a near-infrared spectroscopy detector;
calculating a near-infrared spectrum from the back-scattered near-infrared light;
determining the degree of crystallinity and/or the molecular orientation of the one or more thermoplastic polymer films by comparing the calculated near-infrared spectrum to a near-infrared spectrum of a reference material to determine a Conformity Index as a measure of the degree of crystallinity and/or the molecular orientation of the one or more thermoplastic polymer films.

18. The method according to claim 17 , wherein the one or more thermoplastic polymer films are biaxially oriented polymer films.

19. The method according to claim 17 , wherein the one or more thermoplastic polymer films are uniaxially oriented polymer films.

Assignees

• Tata Steel Ijmuiden Bv

Inventors

• Kondratiuk Dmitry
• Penning Jan Paul

Classifications

• G01N2021/4709

  Backscatter · CPC title

• G01N21/47

  Scattering, i.e. diffuse reflection (G01N21/25, G01N21/41 take precedence {G01N21/55 takes precedence}) · CPC title

• G01N21/35

  using infrared light (G01N21/39 takes precedence) · CPC title

• B29K2995/0053

  bi-axially · CPC title

• B29K2995/0051

  mono-axially · CPC title