METHOD FOR WELDING MOLDED BODIES

Abstract

A process for welding a first molding to a second molding. The process uses an implement including first and second external surfaces. Each external surface further includes a duct. An end of the first molding is heated by a hot gas while the end is at a distance from the duct-entry plane in the range from 3 mm outside the duct to 10 mm inside the duct. A junction area of the second molding is heated by a hot gas while the junction area is at a distance from the duct-entry plane in a range from 3 mm outside the duct to 10 mm inside the duct. The heated end and the heated junction area are then brought into contact with one another and cooled, forming a weld between the first molding and the second molding. Also disclosed is a welded molding obtainable by the process of the invention.

Claims

1. A process for the welding of a first molding (1a) to a second molding (1b), where the first molding (1a) comprises a first lateral area (3a), a second lateral area (4a) and an end (2a), which comprises a first thermoplastic polymer, and where the second molding (1b) comprises a junction area (2b) which comprises a second thermoplastic polymer, comprising the steps of a) provision of the first molding (1a), b) provision of the second molding (1b), c) provision of an implement (5) which has a first external area (6a) and a second external area (6b), where the first external area (6a) comprises a duct (7a), and where the duct (7a) has a floor (10a), a first duct wall (8a) with a first highest point (12a) and a second duct wall (9a) with a second highest point (13a), where the floor (10a) comprises a means (11a) for the introduction of gas into the duct (7a), where a duct-entry plane (14a) runs through the first highest point (12a) parallel to the first external area (6a) and where the location of an exterior duct region (17a) is between a projection line (15a) from the first highest point (12a) along a direction running perpendicularly to the duct-entry plane (14a) and a projection line (16a) from the second highest point (13a) along a direction running perpendicularly to the duct-entry plane (14a), where the second external area (6b) comprises a duct (7b), and where the duct (7b) has a floor (10b), a first duct wall (8b) with a first highest point (12b) and a second duct wall (9b) with a second highest point (13b), where the floor (10b) comprises a means (11b) for the introduction of gas into the duct (7b), where a duct-entry plane (14b) runs through the first highest point (12b) parallel to the second external area (6b) and where the location of the exterior duct region (17b) is between a projection line (15b) from the first highest point (12b) along a direction running perpendicularly to the duct-entry plane (14b) and a projection line (16b) from the second highest point (13b) along a direction running perpendicularly to the duct-entry plane (14b), d) positioning of the first molding (1a), where a distance (Xa) of the end (2a) from the duct-entry plane (14a) in a direction running perpendicularly to the duct-entry plane (14a) is in the range from 3 mm outside the duct (7a) to 10 mm inside the duct (7a), where if the distance (Xa) is in the range from >0 mm to 3 mm outside the duct (7a), the location of the end (2a) is at least to some extent in the exterior duct region (17a), and if the distance (Xa) is in the range from 0 mm to 10 mm inside the duct (7a), a minimal distance (Y1a) of the first lateral area (3a) from the first duct wall (8a) is in the range from 0.2 to 5 mm, and a minimal distance (Y2a) of the second lateral area (4a) from the second duct wall (9a) is in the range from 0.2 to 5 mm, e) positioning of the second molding (1b), where a distance (Xb) of the junction area (2b) from the duct-entry plane (14b) in a direction running perpendicularly to the duct-entry plane (14b) is in the range from 3 mm outside the duct (7b) to 10 mm inside the duct (7b), where if the distance (Xb) is in the range from >0 mm to 3 mm outside the duct (7b), the junction area (2b) is at least to some extent in the exterior duct region (17b), and if the distance (Xb) is in the range from 0 mm to 10 mm inside the duct (7b), the second molding (1b) additionally has a first lateral area (3b) and a second lateral area (4b) and a minimal distance (Y1b) of the first lateral area (3b) from the first duct wall (8b) is in the range from 0.2 to 5 mm, and where a minimal distance (Y2b) of the second lateral area (4b) from the second duct wall (9b) is in the range from 0.2 to 5 mm, f) introduction of a hot gas via the means (11a) for the introduction of gas into the duct (7a), where the temperature of the end (2a) of the first molding (1a) increases to a temperature T.sub.1a and where the first thermoplastic polymer comprised in the end (2a) melts, g) introduction of a hot gas via the means (11b) for the introduction of gas into the duct (7b), where the temperature of the junction area (2b) of the second molding (1b) increases to a temperature T.sub.1b and where the second thermoplastic polymer comprised in the junction area (2b) melts, h) removal of the first molding (1a) from the position achieved in step d), i) removal of the second molding (1b) from the position achieved in step e), j) bringing of the heated end (2a) of the first molding (1a) into contact with the heated junction area (2b) of the second molding (1b) and cooling of the heated end (2a) of the first molding (1a) to a temperature T.sub.2a and of the heated junction area (2b) of the second molding (1b) to a temperature T.sub.2b while the heated end (2a) and the heated junction area (2b) are in contact with one another to form a weld between the first molding (1a) and the second molding (1b).

2. The process according to claim 1, wherein the temperature (T.sub.1a) to which the temperature of the end (2a) of the first molding (1a) increases in step f) is above the glass transition temperature (T.sub.G1) of the first thermoplastic polymer comprised in the end (2a) if the first thermoplastic polymer is an amorphous thermoplastic polymer, and is above a the melting point (T.sub.M1) of the first thermoplastic polymer comprised in the end (2a) if the first thermoplastic polymer is a semicrystalline thermoplastic polymer, and/or the temperature (T.sub.1b) to which the temperature of the junction area (2b) increases in step g) is above the glass transition temperature (T.sub.G2) of the second thermoplastic polymer comprised in the junction area (2b) if the second thermoplastic polymer is an amorphous thermoplastic polymer, and is above the melting point (T.sub.M2) of the second thermoplastic polymer comprised in the junction area (2b) if the second thermoplastic polymer is a semicrystalline thermoplastic polymer.

3. The process according to claim 1, wherein the first thermoplastic polymer comprised in the end (2a) is selected from the group consisting of polyamides, polyoxymethylenes, polysulfone, polyphenyl sulfone and polybutylene terephthalates, and/or the second thermoplastic polymer comprised in the junction area (2b) is selected from the group consisting of polyamides, polyoxymethylenes, polysulfone, polyphenyl sulfone and polybutylene terephthalates.

4. The process according to claim 1, wherein the first thermoplastic polymer comprised in the end (2a) and the second thermoplastic polymer comprised in the junction area (2b) are identical.

5. The process according to claim 1, wherein the temperature (T.sub.1a) to which the temperature of the end (2a) of the first molding (1a) increases in step f) is in the range from 0 to 300 C. above the glass transition temperature (T.sub.G1) of the first thermoplastic polymer comprised in the end (2a) if the first thermoplastic polymer is an amorphous thermoplastic polymer, and is in the range from 0 to 300 C. above the melting point (T.sub.M1) of the first thermoplastic polymer comprised in the end (2a) if the first thermoplastic polymer is a semicrystalline thermoplastic polymer, and/or the temperature (T.sub.1b) to which the temperature of the junction area (2b) of the second molding (1b) increases in step g) is in the range from 0 to 300 C. above the glass transition temperature (T.sub.G2) of the second thermoplastic polymer comprised in the junction area (2b) if the second thermoplastic polymer is an amorphous thermoplastic polymer, and is in the range from 0 to 300 C. above the melting point (T.sub.M2) of the second thermoplastic polymer comprised in the junction area (2b) if the second thermoplastic polymer is a semicrystalline thermoplastic polymer.

6. The process according to claim 1, wherein the first external area (6a) of the implement (5) provided in step c) is opposite to the second external area (6b) of the implement (5).

7. The process according to claim 1, wherein the orientation of the first duct wall (8a) of the duct (7a) of the first external area (6a) is in essence parallel to the second duct wall (9a) of the duct (7a) of the first external area (6a) and/or the orientation of the first duct wall (8b) of the duct (7b) of the second external area (6b) is in essence parallel to the second duct wall (9b) of the duct (7b) of the second external area (6b).

8. The process according to claim 1, wherein the first molding (1a) is positioned in step d) in such a way that if the distance (Xa) is in the range from >0 mm to 3 mm outside the duct (7a), the location of the end (2a) is entirely in the exterior duct region (17a) and/or the second molding (1b) is positioned in step e) in such a way that if the distance (Xb) is in the range from >0 mm to 3 mm outside the duct (7b), the location of the junction area (2b) is entirely in the exterior duct region (17b).

9. The process according to claim 1, wherein the first molding (1a) is positioned in step d) in such a way that the distance (Xa) is in the range from 0 to 10 mm inside the duct (7a).

10. The process according to claim 1, wherein the hot gas which is introduced in step f) is selected from the group consisting of CO.sub.2, N.sub.2 and air and/or the hot gas which is introduced in step g) is selected from the group consisting of CO.sub.2, N.sub.2 and air.

11. The process according to claim 1, wherein the temperature of the hot gas which is introduced in step f) is in the range from 100 to 600 C. and/or the temperature of the hot gas which is introduced in step g) is in the range from 100 to 600 C.

12. The process according to claim 1, wherein the temperature (T.sub.2a) to which the heated end (2a) of the first molding (1a) is cooled in step j) is below the glass transition temperature (T.sub.G1) of the first thermoplastic polymer comprised in the end (2a) if the first thermoplastic polymer is an amorphous thermoplastic polymer, and is below the melting point (T.sub.M1) of the first thermoplastic polymer comprised in the end (2a) if the first thermoplastic polymer is a semicrystalline thermoplastic polymer, and/or the temperature (T.sub.2b) to which the junction area (2b) of the second molding (1b) is cooled in step j) is below the glass transition temperature (T.sub.G2) of the second thermoplastic polymer comprised in the junction area (2b) if the second thermoplastic polymer is an amorphous thermoplastic polymer, and is below the melting point (T.sub.M2) of the second thermoplastic polymer comprised in the junction area (2b) if the second thermoplastic polymer is a semicrystalline thermoplastic polymer.

13. The process according to claim 1, wherein the thickness of the weld formed in step j) between the first molding (1a) and the second molding (1b) is in the range from 20 to 500 m.

14. (canceled)

Description

EXAMPLES

[0254] Molding (1a, 1b) used in inventive example IE1 and comparative example CE2 was a PA 6 GF 30 sheet (polyamide 6 with 30% of glass fiber) with thickness 4 mm.

Inventive Example IE1

[0255] An implement (5) was used with the first external area (6a) opposite to the second external area (6b) and with the duct (7a) of the first external area (6a) opposite to the duct (7b) of the second external area (6b). The orientation of the first duct wall (8a, 8b) and of the second duct wall (9a, 9b) was respectively perpendicular to the floor (10a, 10b) and parallel to one another, the distance between the first duct wall (8a, 8b) and the second duct wall (9a, 9b) being respectively 6 mm. The floor (10a, 10b) comprised nozzles as means (11a, 11b) for the introduction of gas into the duct (7a, 7b). The moldings (1a, 1b) were positioned at a distance (X) of 3.5 mm from the duct-entry plane (14a, 14b) inside the duct (7a, 7b), and the distance (Y1) of the first lateral area (3a, 3b) of the moldings (1a, 1b) from the first duct wall (8a, 8b) and the distance (Y2) of the second lateral area (4a, 4b) of the moldings (1a, 1b) from the second duct wall (9a, 9b) was respectively 1 mm. The distance of the end (2a, 2b) of the moldings (1a, 1b) from the highest point of the means (11a, 11b) for the introduction of gas (the nozzles) was 5 mm.

Comparative Example CE2

[0256] An implement (5) was used with the first external area (6a) opposite to the second external area (6b) and with the duct (7a) of the first external area (6a) opposite to the duct (7b) of the second external area (6b). The orientation of the first duct wall (8a, 8b) and of the second duct wall (9a, 9b) was respectively perpendicular to the floor (10a, 10b) and parallel to one another, the distance between the first duct wall (8a, 8b) and the second duct wall (9a, 9b) being respectively 16 mm. The floor (10a, 10b) comprised nozzles as means (11a, 11b) for the introduction of gas into the duct (7a, 7b). The moldings (1a, 1b) were positioned at a distance (X) of 3.5 mm from the duct-entry plane (14a, 14b) inside the duct (7a, 7b), and the distance (Y1) of the first lateral area (3a, 3b) of the moldings (1a, 1b) from the first duct wall (8a, 8b) and the distance (Y2) of the second lateral area (4a, 4b) of the moldings (1a, 1b) from the second duct wall (9a, 9b) was respectively 6 mm. The distance of the end (2a, 2b) of the moldings (1a, 1b) from the highest point of the means (11a, 11b) for the introduction of gas (the nozzles) was 5 mm.

[0257] The thickness (d) of the layer of molten first thermoplastic polymer formed when the end (2a) of the first molding (1a) was heated was determined. To this end the first molding (1a) and the second molding (1b) were respectively positioned as described above in the duct (7a) of the first external area (6a) and the duct (7b) of the second external area (6b). Only the end (10a) of the first molding (1a) was then heated, nitrogen at a temperature of 430 C. being introduced here into the duct (7a) of the first external area (6a) through the nozzle at a flow rate of 1 l/min per nozzle. The time (t in s) during which the gas was introduced is also termed plastification time. This was varied. The melt layer thickness (d in mm) was then determined as a function of the plastification time by bringing the end (2a) of the first molding (1a) into contact with the junction area (2b) of the second molding (1b) and pressing the two entities together, the compression force being 1180 N. The displacement occurring when the first and second molding (1a, 1b) were pressed together was determined, and is also termed junction displacement. It corresponds to the melt layer thickness (d). The junction area (2b) of the second molding (1b) was therefore not melted in order to determine the melt layer thickness (d).

[0258] The results for inventive example IE1 can be seen in table 1, and the results for comparative example CE2 can be seen in table 2.

TABLE-US-00001 TABLE 1 t [s] d [mm] 3 0.09 5 0.30 10 0.83 15 1.34 20 1.71 25 2.04

TABLE-US-00002 TABLE 2 t [s] d [mm] 5 0.13 10 0.53 15 1.04 20 1.36 25 1.66 30 1.91

[0259] FIG. 5 moreover shows the melt layer thickness (d) as a function of the plastification time (t). It can be seen that a greater thickness of the melt layer is achieved more rapidly by the process of the invention, i.e. the first thermoplastic polymer comprised in the end (2a) and, respectively, the second thermoplastic polymer comprised in the junction area (2b) melt more rapidly when the process of the invention is used than when processes of the type described in the prior art are used. The melt layer is moreover more homogeneous.