Zinc-coated steel cord with improved fatigue resistance

1. A steel cord adapted for the reinforcement of thermoplastic elastomers, said steel cord comprising more than one strand, the strands comprising two or more steel filaments, at least some of said steel filaments being provided with a zinc coating, wherein said zinc coating has a thickness lower than two micrometers and a zinc-steel alloy layer is present between the zinc coating and the steel.

2. A steel cord according to claim 1 wherein said zinc coating has a thickness lower than one micrometer.

3. A steel cord according to claim 1 , wherein said steel cord comprises a cord core and three or more outer strands twisted around said cord core and contacting said cord core.

4. A steel cord according to claim 3 wherein said cord core is a plastic material.

5. A steel cord according to claim 3 wherein said cord core is a core strand with two or more filaments.

6. A steel cord according to claim 5 , wherein said steel cord is a steel cord with a core strand and six outer strands according to the formula:

d 1 +6 ×d 2 +6×( d 2 +6 ×d 3 )

with

d 1 >1.05×d 2 and

d 2 >1.05×d 3 .

7. A composite comprising a thermoplastic elastomer as matrix material and a steel cord according to claim 1 as reinforcing material.

8. A composite according to claim 7 wherein said composite is a belt.

9. A composite according to claim 8 wherein said belt is a grooved belt.

10. A composite according to claim 7 , wherein said thermoplastic elastomer is a polyurethane.

11. A method of manufacturing a steel cord according to claim 1 , comprising the following actions:

(a) obtaining a steel filament;

(b) passing the steel filament through a bath of molten zinc such that the steel filament leaves the bath under a small angle with respect to a horizontal line and is coated with zinc, and mechanically wiping the steel filament coated with zinc, wherein, after wiping, the steel filament has a zinc-steel alloy layer covered by a zinc coating having a thickness lower than one micrometer; and

(c) forming a steel cord according to claim 1 with steel filaments coated with zinc obtained by actions (a)-(b).

12. A method of manufacturing a steel cord according to claim 2 , comprising the following actions:

(a) obtaining a steel filament;

(b) passing the steel filament through a bath of molten zinc such that the steel filament leaves the bath under a small angle with respect to a horizontal line and is coated with zinc, and mechanically wiping the steel filament coated with zinc, wherein, after wiping, the steel filament has a zinc-steel alloy layer covered by a zinc coating having a thickness lower than one micrometer; and

(c) forming a steel cord according to claim 2 with steel filaments coated with zinc obtained by actions (a)-(b).

13. A method of manufacturing a composite according to claim 7 , comprising the following actions:

(a) obtaining a steel filament;

(b) passing the steel filament through a bath of molten zinc such that the steel filament leaves the bath under a small angle with respect to a horizontal line and is coated with zinc, and mechanically wiping the steel filament coated with zinc, wherein, after wiping, the steel filament has a zinc-steel alloy layer covered by a zinc coating having a thickness lower than one micrometer; and

(d) forming the composite according to claim 7 with steel filaments coated with zinc obtained by actions (a)-(b).

14. A method of manufacturing a composite according to claim 8 , comprising the following actions:

(a) obtaining a steel filament;

(b) passing the steel filament through a bath of molten zinc such that the steel filament leaves the bath under a small angle with respect to a horizontal line and is coated with zinc, and mechanically wiping the steel filament coated with zinc, wherein, after wiping, the steel filament has a zinc-steel alloy layer covered by a zinc coating having a thickness lower than one micrometer; and

(d) forming the composite according to claim 8 with steel filaments coated with zinc obtained by actions (a)-(b).