Reinforced coreless tube extrusion systems and methods
Methods of coating a base tube are disclosed. Various methods include passing a hollow base tube into a coating die while maintaining a chamber pressure outside the hollow base tube that is lower than a pressure within an inner lumen of the hollow base tube. Such methods can include extruding coating material onto the hollow base tube to form a coated hollow tube by delivering coating material into the coating die. Vacuum may be formed within the coating die proximate a point of impingement where the coating material is applied to the hollow base tube.
1. A method of coating a hollow base tube, the method comprising:
passing a hollow base tube into a coating die configured to maintain a chamber pressure outside the hollow base tube that is lower than an internal pressure within an inner lumen of the hollow base tube;
extruding coating material onto the hollow base tube using the coating die to form a coated hollow tube by delivering coating material into the coating die, wherein a vacuum is maintained within the coating die proximate a point of impingement where the coating material is applied to the hollow base tube,
passing the hollow base tube through a first vacuum chamber, wherein the first vacuum chamber is configured to maintain a first pressure within the first vacuum chamber that is lower than an ambient pressure outside the first vacuum chamber; and
passing the hollow tube through a second vacuum chamber that is downstream from the first vacuum chamber, wherein the second vacuum chamber is configured to maintain a second pressure within the second vacuum chamber that is lower than the first pressure, the coating die being in fluid communication with the second vacuum chamber.
2. The method of claim 1 , wherein the hollow base tube includes a reinforcing layer.
3. The method of claim 1 , wherein the hollow base tube includes a reinforcing layer comprising one or more strands of reinforcing material formed into at least one of a braided, coiled, spiral wound, and helical pattern.
4. The method of claim 1 , wherein the hollow base tube has a continuous inner layer defining an inner surface of the hollow base tube.
5. The method of claim 1 , further comprising maintaining the internal pressure inside the hollow base tube as the coating material is applied to the hollow base tube.
6. The method of claim 1 , wherein maintaining the chamber pressure outside the hollow base tube at a pressure that is lower than the internal pressure within the inner lumen of the hollow base tube provides radial support to the hollow base tube as the hollow base tube passes through the coating die.
7. The method of claim 1 , further comprising extruding coating material onto the hollow base tube within the coating die such that the coating material forms a seal between the coating die and an outer surface of the hollow base tube such that the vacuum is applied between the coating material and the outer surface of the hollow base tube during application of the coating material to the hollow base tube.
8. The method of claim 1 , further comprising selecting the chamber pressure relative to a wall thickness and a durometer of the hollow base tube such that a dimensional stability of the hollow base tube is maintained.
9. The method of claim 1 , further comprising controlling a tension along the hollow base tube to maintain a dimensional stability of the hollow base tube as the coating material is applied to the hollow base tube.
10. The method of claim 1 , further comprising controlling the chamber pressure outside the hollow base tube and a tensile force along the hollow base tube such that a dimensional stability of the hollow base tube is maintained as the coating material is applied to the hollow base tube.
11. The method of claim 1 , wherein passing the hollow base tube through the first vacuum chamber and passing the hollow base tube through the second vacuum chamber having the second pressure that is lower than an internal pressure within the inner lumen of the hollow base tube provides increased radial strength to the hollow base tube relative to a radial strength of the hollow base tube prior to being passed through the first vacuum chamber.
12. The method of claim 1 , wherein the coated hollow tube is characterized by a substantially smooth inner surface at a magnification of 100×.
13. The method of claim 1 , wherein the coated hollow tube is characterized by an inner surface having an average surface roughness (Ra) of 0.04 μm or less.
14. The method of claim 1 , wherein the coated hollow tube is characterized by an inner surface having an average surface roughness (Ra) of 0.01 μm or less.
15. The method of claim 1 , wherein the coated hollow tube is characterized by a count of less than 450 particles over 10 μm in size on a sample having an inner diameter of about 0.2 cm or greater, and a length of about 30 cm or greater.
16. The method of claim 1 , wherein the coated hollow tube is characterized by a count of less than 25 particles over 25 μm in size on a sample having an inner diameter of about 0.2 cm or greater, and a length of about 30 cm or greater.
17. The method of claim 1 , wherein the hollow base tube is a reinforced tube having an open inner lumen and the coated hollow tube is substantially free of voids between the coating material and the reinforced tube.
18. The method of claim 1 , wherein the hollow base tube is a reinforced tube having an open inner lumen and the coated hollow tube is substantially free of voids within the coating material.