METHOD FOR THE MANUFACTURE OF A FOAMED EXTRUDATE

Abstract

A method for producing a foamed extrudate comprises a device containing a main melting device and an auxiliary melting device. A first melt is generated in the main melting device, a second melt is generated in the auxiliary melting device from a meltable starting material. At least one reactive additive is added to the meltable starting material, wherein the at least one reactive additive being selected from the group consisting of a chemical blowing agent and an active nucleating agent is mixed in the auxiliary melting device with the second melt, so that an additive-containing second melt is obtained in the auxiliary melting device which is added to the first melt.

Claims

1. A method for producing a foamed extrudate, comprising a main melting device and an auxiliary melting device, wherein a first melt is generated in the main melting device, wherein a second melt is generated in the auxiliary melting device from a meltable starting material, wherein at least one reactive additive is added to the meltable starting material, wherein the at least one reactive additive is selected from the group consisting of a chemical blowing agent and an active nucleating agent or wherein the reactive additive is contained in the meltable starting material, wherein the meltable starting material and the reactive additive are melted in the auxiliary melting device to form the second melt, so that an additive-containing second melt containing the reactive additive is obtained in the auxiliary melting device, which is added to the first melt produced in the main melting device.

2. The method of claim 1, wherein the auxiliary melting device is configured as a single-screw extruder.

3. The method of claim 1, wherein the meltable starting material of the auxiliary melting device is added via a feed device as a powder or as a granulate.

4. The method of claim 1, wherein the reactive additive is added as a powder, a granulate or as a masterbatch.

5. The method of claim 1, wherein a metering ratio of the second melt and the first melt is less than 1 to 10.

6. The method of claim 1, wherein the additive-containing second melt is added to the first melt in the main melting device or downstream of the main melting device.

7. The method of claim 1, wherein the main melting device contains a degassing opening, wherein the additive-containing second melt is added downstream of the degassing opening.

8. The method of claim 1, wherein a chemical reaction of the reactive additive takes place partially in the auxiliary melting device.

9. The method of claim 1, wherein the temperature of the second melt or the additive-containing second melt in the auxiliary melting device reaches a value of more than 160 degrees Celsius at least in a section of the auxiliary melting device.

10. The method of claim 1, wherein the temperature of the second melt or the additive-containing second melt is higher than the temperature of the first melt before the first melt and the additive-containing second melt are mixed.

11. The method of claim 1, wherein at least one element from a group consisting of a first mixing device and a first cooling device is arranged downstream of the main melting device.

12. The method of claim 1, wherein at least one element from a group consisting of a second mixing device and a second cooling device is arranged between the auxiliary melting device and the feed to the first melt.

13. The method of claim 12, wherein the additive-containing second melt is mixed or cooled before it is brought into contact with the first melt.

14. The method of claim 1, wherein the active nucleating agent contains at least one substance from the group consisting of a sodium bicarbonate, a citric acid, and a citric acid derivative.

15. The method of claim 1, wherein a metered amount of the reactive additive is controlled by an angular velocity of a rotatable conveying device arranged in the auxiliary melting device.

16. The method of claim 1, wherein an angular velocity of a rotatable conveying device of the auxiliary melting device is regulated by a throughput-dependent set variable of the main melting device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The method according to the invention is illustrated below with the aid of a few exemplary embodiments. It is shown in

[0037] FIG. 1 a diagram of a method according to a first embodiment,

[0038] FIG. 2 a diagram of a method according to a second embodiment,

[0039] FIG. 3 a diagram of a method according to a third embodiment.

DETAILED DESCRIPTION

[0040] FIG. 1 shows a device 10 for carrying out a method for producing a foamed extrudate according to a first embodiment. The device 10 contains a main melting device 1 and an auxiliary melting device 2, a first melt 11 being generated in the main melting device 1. In the auxiliary melting device 2, a second melt 12 is produced from a meltable starting material 3. The meltable starting material 3 can be in the form of a powder or a granulate. A reactive additive 4 is added to the meltable starting material 3. The reactive additive 4 can, for example, be in the form of a powder, a granulate or a masterbatch. A masterbatch can also be used without any further meltable starting material 3. The meltable starting material 3 is melted together with the reactive additive 4 in the secondary melting device 2 to form the second melt 12, so that an additive-containing second melt 14 containing the reactive additive 4 is obtained in the auxiliary melting device 2, which is mixed with the first melt 11 generated in the main melting device 1. The main melting device 1 can also be charged with a meltable starting material 5 which is present as a solid, for example as a powder or granulate. According to an embodiment not shown, the main melting device 1 is supplied with a melt instead of a solid.

[0041] For example, the main melting device 1 is configured as a main extruder. For example, the auxiliary melting device 2 is configured as a secondary extruder, in particular as a single-screw extruder. Due to the simple construction, the auxiliary melting device 2 can be obtained inexpensively in the configuration as a single-screw extruder; in addition, an auxiliary melting device 2 can simply be connected to a main melting device 1 or retrofitted.

[0042] According to an embodiment, at least one of the reactive additives 4 is added to the auxiliary melting device 2 as a powder or as a granulate. The reactive additive 4 can already be added to the meltable starting material 3 in the feed device 16. If a masterbatch is processed by means of the auxiliary melting device 2, the reactive additive 4 can be contained in the masterbatch.

[0043] According to an embodiment, the metering ratio of the second melt 12 with respect to the first melt 11 is less than 1 to 10. According to an embodiment, the metering ratio is less than 1:20. According to an embodiment, the metering ratio is less than 1:50.

[0044] According to the embodiment shown in FIG. 1, the additive-containing second melt 14 is added to the first melt 11 in the main melting device 1. In particular, a chemical reaction of the reactive additive 4 can partially take place in the auxiliary melting device 2. In particular, the additive-containing second melt 14 can reach a temperature higher than 160 degrees Celsius at least in a section of the auxiliary melting device 2. According to an embodiment, the additive-containing second melt 14 can reach a temperature higher than 180 degrees Celsius at least in a section of the auxiliary melting device 2. According to an embodiment, the additive-containing second melt 14 can reach a temperature higher than 200 degrees Celsius at least in a section of the auxiliary melting device 2. The temperature of the additive-containing second melt 14 can be higher than the temperature of the first melt 11 before the first melt 11 and the second melt 12 or the additive-containing second melt 14 are mixed.

[0045] According to the present embodiment, an optional first mixing device 7 is arranged downstream of the main melting device 1. Optionally, a first cooling device 9 is additionally arranged downstream of the main melting device 1. The first cooling device 9 is shown by way of example in FIG. 3.

[0046] According to the embodiment shown in FIG. 1, an optional second mixing device 8 and an optional second cooling device 19 are arranged downstream of the auxiliary melting device 2 so that the additive-containing second melt can be mixed or cooled before it is brought into contact with the first melt 11.

[0047] FIG. 2 shows a device 20 for carrying out a method for producing a foamed extrudate according to a second embodiment. The same reference numerals as in FIG. 1 are used for elements that are the same or have the same effect.

[0048] The device 20 contains a main melting device 1 and an auxiliary melting device 2, a first melt 11 being generated in the main melting device 1. In the auxiliary melting device 2, a second melt 12 is produced from a meltable starting material 3, which is present, for example, as a powder or as a granulate. A reactive additive 4 is added to the meltable starting material 3 or the reactive additive 4 is already contained in the meltable starting material 3. The meltable starting material 3 is melted together with the additive 4 in the auxiliary melting device 2 to form the second melt 12, so that in the auxiliary melting device 2 an additive-containing second melt 14 containing the reactive additive 4 is obtained, which is mixed with the first melt 11 generated in the main melting device 1. The main melting device 1 can also be charged with a meltable starting material 5 which is present as a solid, in particular as a powder or granulate. According to an embodiment not shown, the main melting device 1 can be supplied with a melt instead of a solid.

[0049] According to an embodiment, the auxiliary melting device 2 is configured as a secondary extruder, in particular as a single-screw extruder. Due to the simple construction, the auxiliary melting device 2 can be obtained inexpensively in the configuration as a single-screw extruder; in addition, this auxiliary melting device 2 can simply be connected to an existing main melting device 1 or retrofitted.

[0050] According to an embodiment, at least the reactive additive 4 is added to the auxiliary melting device 2 as a powder, as a granulate or as a masterbatch. The reactive additive 4 can already be added to the meltable starting material 3 in the feed device 16. If a masterbatch is processed by means of the auxiliary melting device 2, the reactive additive 4 can be contained in the masterbatch.

[0051] According to an embodiment, the metering ratio of the second melt 12 with respect to the first melt 11 is less than 1 to 10. According to an embodiment, the metering ratio is less than 1:20. According to an embodiment, the metering ratio is less than 1:50.

[0052] In particular, a chemical reaction of the reactive additive 4 can partially take place in the auxiliary melting device 2. In particular, the additive-containing second melt 14 can reach a temperature higher than 160 degrees Celsius at least in a section of the auxiliary melting device 2. According to an embodiment, the additive-containing second melt 14 can reach a temperature higher than 180 degrees Celsius at least in a section of the auxiliary melting device 2. According to an embodiment, the additive-containing second melt 14 can reach a temperature higher than 200 degrees Celsius at least in a section of the auxiliary melting device 2. The temperature of the additive-containing second melt 14 can be higher than the temperature of the first melt 11 before the first melt 11 and the second melt 12 or the additive-containing second melt 14 are mixed.

[0053] According to the embodiment shown in FIG. 2, the additive-containing second melt 14 is added to the first melt 11 downstream of the main melting device 1.

[0054] According to this embodiment, the main melting device 1 contains a degassing opening 13, the additive-containing second melt 14 containing the reactive additive 4 being added downstream of the degassing opening 13. According to this embodiment, the additive-containing second melt 14 is added downstream of the outlet end 15 of the main melting device 1, for example in a conduit 6.

[0055] According to an embodiment (not shown), the additive-containing second melt 14 can also be added to a section of the main melting device 1 which is located between the degassing opening and the outlet end 15. Mixing devices 7, 8 or a cooling device 9 can be provided as in the first embodiment. A mixing device and/or a cooling device can follow after the main melting device.

[0056] FIG. 3 shows a device 10 for carrying out a method for producing a foamed extrudate according to a third embodiment. The device 10 contains a main melting device 1 and an auxiliary melting device 2, a first melt 11 being generated in the main melting device 1. In the auxiliary melting device 2, a second melt 12 is produced from a meltable starting material 3. The meltable starting material can be in the form of powder or a granulate. A reactive additive 4 is added to the meltable starting material 3. The reactive additive 4 can, for example, be in the form of a powder, a granulate or a masterbatch. A masterbatch can also be used without any further meltable starting material 3. The plastic 3 is melted together with the reactive additive 4 and a physical blowing agent 17 in the auxiliary melting device 2 to form the second melt 12, so that an additive-containing second melt 14 containing the reactive additive 4 and the physical blowing agent 17 is obtained in the auxiliary melting device 2, wherein the first melt 11 generated in the main melting device 1 is mixed therewith. The main melting device 1 can also be charged with a meltable starting material 5 which is present as a solid, for example as a powder or a granulate. According to an embodiment not shown, the main melting device 1 is supplied with a melt instead of a solid.

[0057] For example, the main melting device 1 is configured as a main extruder. For example, the auxiliary melting device 2 is configured as a secondary extruder, in particular as a single-screw extruder. Due to the simple construction, the auxiliary melting device 2 can be obtained inexpensively in the configuration as a single-screw extruder; in addition, an auxiliary melting device 2 can simply be connected to a main melting device 1 or retrofitted.

[0058] According to an embodiment, at least one of the reactive additives 4 is added to the auxiliary melting device 2 as a powder or as a granulate. The reactive additive 4 can already be added to the meltable starting material 3 in the feed device 16. If a masterbatch is processed by means of the auxiliary melting device 2, the reactive additive 4 can be contained in the masterbatch.

[0059] According to an embodiment, the metering ratio of the second melt 12 with respect to the first melt 11 is less than 1 to 10. According to an embodiment, the metering ratio is less than 1:20. According to an embodiment, the metering ratio is less than 1:50.

[0060] According to the embodiment shown in FIG. 3, the additive-containing second melt 14 is added to the first melt 11 in the main melting device 1. In particular, a chemical reaction of the reactive additive 4 can partially take place in the auxiliary melting device 2. In particular, the additive-containing second melt 14 can reach a temperature higher than 160 degrees Celsius at least in a section of the auxiliary melting device 2. According to an embodiment, the additive-containing second melt 14 can reach a temperature higher than 180 degrees Celsius at least in a section of the auxiliary melting device 2. According to an embodiment, the additive-containing second melt 14 can reach a temperature higher than 200 degrees Celsius at least in a section of the auxiliary melting device 2. The temperature of the additive-containing second melt 14 can be higher than the temperature of the first melt 11 before the first melt 11 and the second melt 12 or the additive-containing second melt 14 are mixed.

[0061] According to the present embodiment, an optional first cooling device 9 is arranged downstream of the main melting device 1. In addition, as in FIG. 1, a first mixing device 7 can be provided, which is not shown in the drawing. In addition, as in the embodiment shown in FIG. 1, an optional second mixing device 8 and an optional second cooling device 19 can be arranged between the auxiliary melting device 2 and the main melting device 1, so that the additive-containing second melt 14 can be mixed or cooled before it is brought into contact with the first melt 11.

[0062] Alternatively, according to an embodiment not shown, a physical blowing agent can be metered into the first melt the main melting device 1 or downstream of the main melting device 1.

[0063] It is obvious to a person skilled in the art that many further variants are possible in addition to the embodiments described without departing from the inventive concept. The subject matter of the invention is therefore not restricted by the preceding description and is determined by the scope of protection which is defined by the claims. The broadest possible reading of the claims is authoritative for the interpretation of the claims or the description. In particular, the terms “contain” or “include” are to be interpreted in such a way that they refer to elements, components, or steps in a non-exclusive meaning, which is intended to indicate that the elements, components, or steps can be present or are used that they can be combined with other elements, components or steps that are not explicitly s mentioned. When the claims relate to an element or component from a group which may consist of A, B, C to N elements or components, this formulation should be interpreted in such a way that only a single element of that group is required, and not combination of A and N, B and N, or any other combination of two or more elements or components of this group.