Process for producing solid particles

Abstract

Process for the production of solid particles comprising a material with melting point from −20 to 300° C. at atmospheric pressure, characterized in that a mixture comprising: a1) the material in molten form and a2) the material in solid form is mixed by means of an extruder to give a paste, this is forced through a pelletizing die to give strands, and the strands are comminuted.

Claims

1. A process for the production of solid particles comprising a material with a melting point of −20 to 300° C. at atmospheric pressure, the process comprising: Mixing within an extruder a1) the material in molten form, and a2) the material in solid form to give a paste, forcing the paste through a pelletizing die to form strands, and comminuting the strands into solid particles, wherein the material is caprolactam, laurolactam or a mixture thereof.

2. The process as claimed in claim 1, wherein the paste comprises at least 80% by weight of the material.

3. The process as claimed in claim 1, wherein the solid particles have a spherical or cylindrical shape.

4. The process as claimed in claim 1, wherein the solid particles have a size of 0.2 to 20 mm.

5. The process as claimed in claim 1, wherein: the components a1) and a2) are mixed at a ratio of a1) to a2) of 1:1 to 1:4.

6. The process as claimed in claim 5, wherein the comminuting is done by means of mechanical force.

7. The process as claimed in claim 1, wherein: the paste further comprises a catalyst and/or an activator.

8. The process as claimed in claim 1, wherein the mixing step comprises at least one of: i) separately feeding the components a1) and a2) into the extruder; or ii) feeding the component a2) into the extruder and producing the component a1) within the extruder via heating and/or via introduction of energy from conveying elements and/or shear elements of the extruder, to reach a temperature in the extruder at which some of component a2) has melted; or iii) feeding the component a1) into the extruder and producing the component a2) within the extruder via cooling of the extruder to a temperature at which some of the component a1) solidifies.

9. The process as claimed in claim 8, wherein the conveying elements and/or shear elements are screws of the extruder.

10. The process as claimed in claim 1, wherein: the components a1) and a2) are mixed at a ratio of a1) to a2) of 1:1 to 1:4; and the paste comprises at least 80% by weight of the material.

11. The process as claimed in claim 10, wherein: the melting point of the material at atmospheric pressure is 50 to 160° C.; the material has a molar mass of less than 1000 g/mol; the material, in molten form, has a viscosity at the melting point under atmospheric pressure of less than 1×10.sup.4 Pa.Math.s; the ratio of a1) to a2) is 1:1.5 to 1:4.

12. The process as claimed in claim 11, wherein the mixing step comprises one of: i) separately feeding the components a1) and a2) to the extruder; or ii) feeding the component a2) into the extruder, and producing component a1) within the extruder via heating and/or via introduction of energy from screws of the extruder, to reach a temperature in the extruder at which some of component a2), previously present in solid form, melts to give component a1); or iii) feeding component a1) into the extruder and producing component a2) within the extruder via cooling of the extruder to a temperature at which some of the component a1) solidifies.

13. The process as claimed in claim 12, wherein: the paste further comprises a catalyst and/or an activator; the ratio of a1) to a2) is 1:2.3 to 1:4; the paste comprises at least 90% by weight of the material; and the solid particles have a spherical shape with an aspect ratio of 1 to 3 or cylindrical shape with a diameter of 0.2 to 30 mm and a length of 0.3 to 30 mm.

Description

EXAMPLES

Example 1

(1) Extruder used: twin-screw extruder (Leistritz ZSE 27 Maxx-480)

(2) Heating zones: 11 (L/D: 48)

(3) Pelletizing die: 1 conical holes with 3.2 mm diameter

(4) Machine parameters: screw rotation rate: 80 UpM

(5) Temperatures: all zones 68° C. except for zone 1 (66° C.) and zone 11 (67° C.)

(6) The strands discharged through the pelletizing die of the pelletizing unit were chopped by a mechanical chopper unit and collected after from 1 to 3 seconds after a flight time in dry air. Cooling of the particles during this time was sufficient to prevent caking.

(7) FIG. 1 is a diagram of the procedure, where the individual components are as follows: (1) Material intake (2) Extruder (3) Manual mixer with wire-basket mixing head (4) Flight path of chopped paste particles (5) Collection container.

(8) Specifically, the discharged caprolactam strands were chopped with the aid of a conventional manual mixer with a wire-basket stirrer in a manner that projected them along a parabolic flight path into a collection container 2 m away from the die. The substantially spherical or cylindrical particles of size from 3-4 mm were cooled to room temperature and, by virtue of their good flowability, could very easily be poured from one container to another. They also exhibited very good resistance to caking after packaging in sacks and exposure of these to mechanical stress during storage. Furthermore, absolutely no fines were produced.

(9) About 50 g of each mixture was stored in a gastight jar with screw cap.

Example 2

(10) As example 1, but a premix made of 96% by weight of caprolactam and 4% by weight of Addonyl Kat NI from Rhein Chemie Rheinau GmbH (18% by weight of sodium caprolactamate in caprolactam) was used as starting material. The intake region of the extruder was inertized with nitrogen.

Example 3

(11) As example 1, but a premix made of 98% by weight of caprolactam and 2% by weight of Addonyl 8120 from Rhein Chemie Rheinau GmbH (caprolactam-blocked hexamethylene diisocyanate with a proportion of up to 2.5% by weight of caprolactam) was used as starting material. The intake region of the extruder was intertized with nitrogen.

Example 4

(12) As example 1, but a premix made of 93% by weight of caprolactam, 2% by weight of Addonyl 8120 and 5% by weight of Addonyl 8112 (low-temperature impact modifier) from Rhein Chemie Rheinau GmbH was used as starting material. The intake region of the extruder was inertized with nitrogen.

Example 5

(13) After one week, the containers from examples 2 and 3 were separately melted in vacuum, and the melts were combined and poured into a glass beaker controlled to a temperature of 160° C.

(14) Anionic polymerization began after about 1 minute, and a polyamide 6 was produced with 1.2% by weight residual monomer content.

Example 6

(15) After one week, the containers from examples 2 and 4 were separately melted in vacuum, and the melts were combined and poured into a glass beaker controlled to a temperature of 160° C.

(16) Anionic polymerization began after about 1 minute, and a polyimide 6 was produced with 1.4% by weight residual monomer content.