Surface preparation and polymeric coating of continuous-strip flat-rolled steel and coated product

1. A polymeric coating process for producing composite-coated continuous-strip steel, comprising:

activating a first surface of a continuous-strip steel substrate;

presenting the activated first surface at ambient temperature for co-extrusion;

co-extruding a first coating on the activated first surface presented at ambient temperature, the first coating comprising a thermoplastic polymeric first contacting layer in contact with the activated first surface and a first bulk layer overlying the first contacting layer, the first contacting layer comprising anhydride-modified polypropylene, the first bulk layer comprising polypropylene and polybutylene; and

solidifying the first coating.

2. The process of claim 1 , further comprising:

melting the first contacting layer and the first bulk layer; and

rapidly cooling the first contacting and bulk layers through glass transition temperatures of the thermoplastic polymers.

3. The process of claim 1 , further comprising:

activating a second surface of the continuous-strip steel substrate;

presenting the activated second surface at ambient temperature for co-extrusion;

co-extruding a second coating on the activated second surface presented at ambient temperature, the second coating comprising a thermoplastic polymeric second contacting layer in contact with the activated second surface and a second bulk layer overlying the second contacting layer, the second contacting layer comprising anhydride-modified polypropylene, the second bulk layer comprising polypropylene and polybutylene; and

solidifying the second coating.

4. The process of claim 3 , further comprising:

melting the first and second coatings; and

rapidly cooling the first and second coatings through glass transition temperatures of the thermoplastic polymers.

5. The process of claim 1 , wherein the continuous-strip steel substrate has a thickness in a range of 5 mils to 15 mils.

6. A polymeric coating process for producing composite-coated continuous-strip steel, comprising:

activating a first surface of a continuous-strip steel substrate;

presenting the activated first surface at ambient temperature for co-extrusion;

co-extruding a first coating on the activated first surface presented at ambient temperature, the first coating comprising a thermoplastic polymeric first contacting layer in contact with the activated first surface, a first intermediate bulk layer overlying the first contacting layer, and a first outer surface layer overlying the first intermediate bulk layer, the first contacting layer comprising anhydride-modified polypropylene, the first intermediate bulk layer comprising polypropylene and polybutylene, the first outer surface layer comprising polypropylene and polybutylene; and

solidifying the first coating.

7. The process of claim 6 , wherein the first intermediate bulk layer has a polybutylene content of 15 to 25 weight percent, and wherein the first outer surface layer has a polybutylene content of 5 to 10 weight percent.

8. The process of claim 6 , further comprising:

melting the first contacting layer, the first intermediate bulk layer, and the first outer surface layer; and

rapidly cooling the first coating through glass transition temperatures of the thermoplastic polymers.

9. The process of claim 6 , further comprising:

activating a second surface of the continuous-strip steel substrate;

presenting the activated second surface at ambient temperature for co-extrusion;

co-extruding a second coating on the activated second surface presented at ambient temperature, the second coating comprising a thermoplastic polymeric second contacting layer in contact with the activated second surface, a second intermediate bulk layer overlying the second contacting layer, and a second outer surface layer overlying the second intermediate bulk layer, the second contacting layer comprising anhydride-modified polypropylene, the second intermediate bulk layer comprising polypropylene and polybutylene, the second outer surface layer comprising polypropylene and polybutylene; and

solidifying the second coating.

10. The process of claim 9 , wherein the first and second intermediate bulk layers each have a polybutylene content of 15 to 25 weight percent, and wherein the first and second outer surface layers each have a polybutylene content of 5 to 10 weight percent.

11. The process of claim 9 , further comprising:

melting the first and second coatings; and

rapidly cooling the first and second coatings through glass transition temperatures of the thermoplastic polymers.

12. Polymeric coating process for producing composite-coated continuous-strip flat-rolled steel, comprising:

A) supplying continuous-strip flat-rolled steel substrate for continuous-line travel presenting opposed substantially-planar surfaces extending width-wise between longitudinally-extending lateral edges of said substrate;

B) pre-treating a single surface at-a-time of said substrate so as to activate said surface for polymeric adhesion;

C) delivering said substrate, at ambient temperature, presenting an activated surface for polymeric coating;

D) pre-heating and pressurizing multiple-selected thermoplastic polymeric materials for molten extrusion under pressure;

E) extruding said thermoplastic polymeric materials as adherent thin-film layers, and

F) depositing said adherent thin-film layers for travel in said continuous-line associated with a single activated surface, while providing for selecting from the group consisting of

(i) depositing said adherent thin-film layers of polymeric coating materials for association solely with one said activated surface,

(ii) depositing adherent thin-film layers of polymeric coating materials, separately on separately-activated opposed surfaces in said continuous-line, each for travel associated with its respective separately-activated opposed surface,

G) selecting said multiple thermoplastic polymeric materials for extruding as adherent thin-film layers, to include

(i) an anhydride-modified polypropylene layer, and

(ii) at least one layer combining polybutylene, in a selected percentage by weight range, with the balance polypropylene; while providing for

H) contacting said selected separately activated substrate surface first with said anhydride-modified polypropylene layer.

13. The process of claim 12 , including

I) supplying said continuous-strip flat-rolled steel substrate, so as to be substantially-free of iron oxide, on said opposed surfaces, for coating with said polymeric materials, by

protecting said opposed planar surfaces against corrosion by selecting a metallic corrosion-protective coating from the group consisting of

(i) cathodic-dichromate,

(ii) electrolytic plating combining chrome and chrome oxide,

(iii) electrolytic tinplating,

(iv) electrolytic zinc plating, and

(v) hot-dipped zinc-spelter coating.

14. The process of claim 13 , in which said pre-treating, of a single surface substantially free of iron-oxide, is carried out by selection from the group consisting of:

(i) impinging an open-flame,

(ii) ionizing gaseous atmosphere contiguous to said single surface, and

(iii) combinations of (i) and (ii),

for depositing said adherent thin-film layers for travel with a separately-activated surface, as selected in Paragraph F above.

15. The process of claim 14 , including providing for

J) extruding said thin-film polymeric materials

a) extending across full surface width of said strip, and, in addition

b) extending width-wise beyond each said longitudinally-extending lateral edge of said surface, resulting in

c) forming a width-wise extending polymeric overhang along each said lateral edge of said strip;

K) solidifying said polymeric coating materials, including said polymeric overhang, while said strip is traveling in-line, then

(i) trimming said solidified polymeric overhang from each said lateral edge of said strip, for

(ii) facilitating achieving substantially-uniform polymeric coating thickness, associated with a single activated surface as selected above, between said lateral edges of said strip while traveling in-line.

16. The process of claim 15 , in which

selecting said multiple polymeric materials, to include

(a) an anhydride-modified polypropylene for first-contacting said activated surface;

(b) an intermediate layer, combining polypropylene and polybutylene, in which polybutylene is selected in the range of about fifteen to about twenty-five percent by weight, and,

(c) an outer surface layer combining polypropylene and polybutylene is which polybutylene is included in the range of five to ten percent by weight; and, in which

selecting said pre-treating steps, to include

restricting oxygen-based content of said impinging open flame,

(b) utilizing corona discharge, free of arcing, ionizing said gaseous atmosphere.

17. The process of claim 16 , further including

L) measuring solidified polymeric coating thickness across strip width, by selecting from the group consisting of

at least one location intermediate lateral edges of such strip, and

a plurality of locations intermediate lateral edges of such strip.

18. The process of claim 17 , including

M) responding to said thickness measuring for maintaining substantially-uniform polymeric thickness per activated surface, by selecting from the group consisting of

(i) quantitatively adjusting pressurized feed of said molten extrusion,

(ii) adjusting said nozzle opening; and,

(iii) adjusting said line speed; and

N) selecting a polymeric thickness per activated surface in a thickness range of above about 0.2 mil to about 4.0 mils.

19. The process of claim 18 , further including

O) finishing-processing of said polymeric coating materials, by

(i) heating to within a temperature range for melting said adherent layers of polymeric materials,

(ii) maintaining said heated condition for a selected interval of strip travel, for implementing polymeric material contact with, and covering of, surface topography, as presented by a selected activated surface, and

P) rapidly cooling said polymeric coating materials, through respective glass-transition temperatures, fixedly establishing substantially-uniform amorphous characteristics throughout said multiple layers of polymeric coating materials.