Method and apparatus for degassing coating material

1. A method for degassing coating material comprising the steps of:

supplying coating material to a first stage of a single degassing apparatus having the first stage in a first compartment and a second stage contained in a second compartment of the same single degassing apparatus;

degassing the coating material in the first stage in the first compartment by forming a vacuum therein;

forming a vacuum in the second compartment containing the second stage;

feeding the degassed coating material from the first stage to a bottom part region of a drum rotating in the second compartment around an essentially vertical axis, the second compartment having an inner wall, the vertical axis defining a radial direction and a height direction, and wherein the drum has an inner wall;

rotating the drum to cause the coating material to rise up the inner wall of the drum and to discharge from an upper edge of the drum as a thin film against the inner wall of the second compartment so that the coating material flows downwards along the second compartment inner wall; and

conducting the coating material out of the second compartment.

2. The method of claim 1 wherein the step of degassing the coating material in the first stage in the first compartment comprises:

feeding the coating material to a bottom part region of a drum rotating in the first compartment around an essentially vertical axis, the first compartment having an inner wall, the vertical axis defining a radial direction and a height direction, and wherein the drum has an inner wall;

rotating the first stage drum to cause the coating material to rise up the inner wall of the drum and to discharge from an upper edge of the drum as a thin film against the inner wall of the first compartment so that the coating material flows downwards along the first compartment inner wall; and

conducting the coating material out of the first compartment to the bottom part region of the drum rotating in the second compartment.

3. An apparatus for degassing coating material, comprising:

a first container part, the first container part defining a first inside portion, the first inside portion connected to a first source of vacuum, so that coating material in the inside portion is degassed;

a first coating material inlet arranged to feed coating material to the first inside portion of the first container part and a first coating material outlet arranged to discharge coating material from the first container part;

a second container part mounted to the first container part, the second container part defining a second inside portion and an inner wall of the second inside portion, the second inside portion connected to a second source of vacuum, so that coating material in the second inside portion is degassed;

a second coating material inlet connected to the first coating material outlet to supply coating material from the first inside portion to the second inside portion;

a drum mounted for rotation around an essentially vertical axis in the second inside portion of the second container part, the drum having a bottom part region, a drum inner wall, and a drum upper edge, wherein the second coating material inlet is arranged in coating material supplying relation to the second container part drum bottom part region, and the drum inner wall is in coating material receiving relation to the drum bottom part region so when the drum is driven to rotate, coating material passes from the drum bottom part region to the drum inner wall, to the drum upper edge and then to the inner wall of the second inside portion; and

a second coating material outlet arranged to discharge coating material flowing from the inner wall of the second inside portion.

4. The apparatus of claim 3 wherein the drum inner wall rises in a stepped manner forming at least two steps and at least two step levels, so that when the drum is driven to rotate, coating material passes from the drum bottom part region to the drum inner wall to the drum upper edge, so that the coating material will form a thin, veil-like film on each of the at least two different step levels.

5. The apparatus of claim 3 wherein the first source of vacuum and the second source of vacuum are at an absolute pressure of about 1 kPa to 15 kPa.

6. The apparatus of claim 5 wherein the first source of vacuum, and the second source of vacuum are at an absolute pressure of about 3 kPa to 15 kPa.

7. The apparatus of claim 3 further comprising:

a nozzle part connected to the second coating material inlet, the nozzle part being arranged in the vicinity of a central region of the bottom part region of the drum; and

an annular protective part positioned around the nozzle part and arranged to prevent the coating material from splashing sideways from the nozzle part.

8. The apparatus of claim 3 wherein a first part drum is arranged inside the first container part and mounted for rotating around an essentially vertical axis, the first part drum having an inner wall and a bottom part region arranged in coating material receiving relation to the first coating material inlet, such that rotating motion of the first part drum causes coating material to rise up the inner wall of the drum and to discharge from a top edge of the drum as a thin film against an inner wall of the first container part, such that the coating material flows downwards to the first coating material outlet.

9. The apparatus of claim 8 further comprising:

a nozzle part connected to the first coating material inlet, the nozzle part being arranged in the vicinity of a central region of the bottom part region of first part drum ; and

an annular protective part positioned around the nozzle part and arranged to prevent the coating material from splashing sideways from the nozzle part.

10. The apparatus of claim 8 , wherein the first part drum inner wall rises in a stepped manner forming at least two steps and at least two step levels, so that when the first part drum is driven to rotate, coating material passes from the first part drum bottom part region to the drum inner wall to the drum upper edge, so that the coating material will form a thin, veil-like film on each of the at least two different step levels.

11. The apparatus of claim 3 , wherein inside the first container part is arranged a cyclone to cause gas to be separated from the coating material.

12. The apparatus claim 3 wherein inside the first container part are arranged spraying parts arranged to feed coating material into the first container part in droplet form.

13. A method for degassing coating material comprising the steps of:

supplying coating material to a first stage of a single degassing apparatus having the first stage in a first compartment and a second stage contained in a second compartment of the same single degassing apparatus;

degassing the coating material in the first stage in the first compartment by forming a vacuum therein;

forming a vacuum in the second compartment containing the second stage;

feeding the degassed coating material from the first stage to a bottom part of a drum rotating in the second compartment around a drum axis which is essentially vertical, the second compartment having an inner wall, and wherein the drum axis defines a radial direction and a height direction, defined as extending vertically parallel to the vertical axis, wherein the drum has an inner wall with a plurality of steps, each step defining a level, which step levels ascend in the height direction as the steps progress outwardly in the radial direction;

using forces created by rotating motion of the drum to cause the coating material to rise up the inner wall of the drum and flow over at least two of the plurality of steps;

veiling the coating material over a front edge of each step to form a radially extending veil-like thin film of the coating material spaced from the inner wall of the drum, which extends between said front edge of the step to the inner wall of the drum;

causing the coating material to discharge from an upper edge of the drum as a thin film against the inner wall of the second compartment so that the coating material flows downwards along the second compartment inner wall; and

conducting the coating material out of the second compartment.

14. An apparatus for degassing coating material, comprising:

a first container part, the first container part defining a first inside portion, the first inside portion connected to a first source of vacuum, so that coating material in the first inside portion is degassed;

a first coating material inlet arranged to feed coating material to the first inside portion of the first container part and a first coating material outlet arranged to discharge coating material from the first container part;

a second container part mounted to the first container part, the second container part defining a second inside portion and an inner wall of the second inside portion, the second inside portion connected to a second source of vacuum, so that coating material in the second inside portion is degassed;

a second coating material inlet connected to the first coating material outlet to supply coating material from the first inside portion to the second inside portion;

a drum mounted for rotation around a vertical axis in the second inside portion of the second container part, the vertical axis defining a radial direction and a height direction defined as extending vertically parallel to the vertical axis, the drum having a bottom part region, a drum inner wall, and a drum upper edge, wherein the second coating material inlet is arranged in coating material supplying relation to the second container part drum bottom part region, and the drum inner wall is in coating material receiving relation to the drum bottom part region so when the drum is driven to rotate, coating material passes from the drum bottom part region to the drum inner wall, to the drum upper edge and then to the inner wall of the second inside portion; and

wherein the drum has an inner surface which has at least two steps, each step defining a level, which step levels ascend in the height direction as the steps progress outwardly in the radial direction, the steps formed of successive concave sections, defining front edges which determine an elevation of the step levels in the height direction, the front edges arranged such that the coating material rising upwards due to the effect of rotation of the drum will form a thin veil-like film of the coating material spaced from the inner wall of the drum, which extends between said front edges of the step levels to the inner wall of the drum; and

an outlet mounted to the tank for discharging the coating material from the tank.

15. The apparatus of claim 14 wherein a first part drum is arranged inside the first container part and mounted for rotating around an essentially vertical axis, the first part drum having an inner wall and a bottom part region arranged in coating material receiving relation to the first coating material inlet, such that rotating motion of the first part drum causes coating material to rise up the inner wall of the drum and to discharge from a top edge of the drum as a thin film against an inner wall of the first container part, such that the coating material flows downwards to the first coating material outlet.

16. The apparatus of claim 15 wherein the first part drum inner wall rises in a stepped manner forming at least two steps and at least two step levels, so that when the drum is driven to rotate, coating material passes from the drum bottom part region to the drum inner wall to the drum upper edge, so that the coating material will form a thin, veil-like film on each of the at least two different step levels.

17. The apparatus of claim 14 wherein inside the first container part is arranged a cyclone to cause gas to be separated from the coating material.

18. The apparatus of claim 14 wherein inside the first container part are arranged spraying parts arranged to feed coating material into the first container part in droplet form.

19. The apparatus of claim 14 further comprising:

a nozzle part connected to the second coating material inlet, the nozzle part being arranged in the vicinity of a central region of the bottom part region of the drum; and

an annular protective part positioned around the nozzle part and arranged to prevent the coating material from splashing sideways from the nozzle part.