METHOD FOR PRODUCING MOULDED PARTS

Abstract

A process is presented and described for the production of moldings, comprising the steps of (a) providing a polymer composition comprising from 1 to 99% by weight of polyhydroxyalkanoate and from 1 to 99% by weight of starch-containing polymer; (b) homogenizing the polymer composition with use of thermal and/or mechanical energy; (c) introducing the polymer composition into a mold; (d) molding the molding in the mold; and (e) removing the molding from the mold. The process described is in particular suitable for the production of hard capsules.

Claims

1. A process for the production of a molding, comprising: a. providing a polymer composition comprising from 1 to 99% by weight of polyhydroxyalkanoate and from 1 to 99% by weight of starch-containing polymer; b. homogenizing the polymer composition with use of thermal and/or mechanical energy; c. introducing the polymer composition into a mold; d. molding a molding in the mold; e. removing the molding from the mold.

2. The process as claimed in claim 1, characterized in that the polymer composition comprises from 5 to 95% by weight, in particular from 10 to 90% by weight or from 20 to 80% by weight or from 30 to 70% by weight, of polyhydroxyalkanoate.

3. The process as claimed in claim 1 or 2, characterized in that the polymer composition comprises from 5 to 95% by weight, in particular from 10 to 90% by weight or from 20 to 80% by weight or from 30 to 70% by weight, of starch-containing polymer.

4. The process as claimed in any of the preceding claims, characterized in that the homogenization of the polymer composition is carried out at a temperature of from 80 to 220° C.

5. The process as claimed in any of the preceding claims, characterized in that the homogenization of the polymer composition is carried out in an extruder.

6. The process as claimed in any of the preceding claims, characterized in that the starch or functionalized starch present in the starch-containing polymer is in essence destructured during the homogenization.

7. The process as claimed in any of the preceding claims, characterized in that the starch-containing polymer is selected from the group consisting of native starch, thermoplastic starch, functionalized starch, starch monophosphate, starch diphosphate, starch sulfate, starch ester, starch ether, hydroxypropylstarch, carboxymethylstarch, starch acetate and mixtures thereof.

8. The process as claimed in any of the preceding claims, characterized in that the polymer composition comprises less than 10% by weight, in particular less than 6 or less than 4% by weight, based on the total weight of starch and plasticizer, of a carbon-containing plasticizer with molar mass 500 g/mol or less, in particular 300 g/mol or less, for example glycerol and/or sorbitol.

9. The process as claimed in any of the preceding claims, characterized in that, before the introduction of the polymer composition into the mold, the water content of the polymer composition is adjusted to less than 10% by weight, in particular less than 7 or less than 5% by weight, based on the total weight of the polymer composition.

10. The process as claimed in any of the preceding claims, characterized in that the polyhydroxyalkanoate of the polymer composition comprises repeating monomer units of the formula (1)
[—O—CHR—CH.sub.2—C(O)—]   (1), where R is an alkyl group of the formula C.sub.nH.sub.2n+1 and n is an integer from 1 to 15, in particular from 1 to 6.

11. The process as claimed in any of the preceding claims, characterized in that the polyhydroxyalkanoate of the polymer composition is selected from the group consisting of poly(3-hydroxybutanoate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and mixtures thereof.

12. The process as claimed in any of the preceding claims, characterized in that the polyhydroxyalkanoate of the polymer composition is a copolymer.

13. The process as claimed in any of the preceding claims, characterized in that the weight-average molar mass of the polyhydroxyalkanoate of the polymer composition is from 60 000 to 500 000 g/mol, in particular from 120 000 to 300 000 g/mol.

14. The process as claimed in any of the preceding claims, characterized in that the melting point of the polyhydroxyalkanoate of the polymer composition is from 120 to 200° C., in particular from 150 to 180° C.

15. The process as claimed in any of the preceding claims, characterized in that the molding is molded by injection molding in the steps c. and d.

16. The process as claimed in any of the preceding claims, characterized in that the pressure with which the polymer composition is injected into the molding in step c. is more than 1 bar, in particular more than 100 bar.

17. The process as claimed in any of the preceding claims, characterized in that the pressure with which the polymer composition is injected into the molding in step c. is from 150 to 3000 bar.

18. The process as claimed in any of the preceding claims, characterized in that the temperature of the polymer composition when said composition is injected into the mold in step c. is above 23° C., in particular above 50° C.

19. The process as claimed in any of the preceding claims, characterized in that the temperature of the polymer composition when said composition is injected into the mold in step c. is from 80 to 200° C.

20. A molding obtainable by a process as claimed in any of claims 1 to 19.

21. A hard capsule comprising a dimensionally stable capsule body and a dimensionally stable capsule cap with respectively at least one side wall and one closed end, where the capsule body and/or the capsule cap has/have been produced by a process as claimed in any of claims 1 to 19.

22. The hard capsule as claimed in claim 21, characterized in that the capsule body and the capsule cap can be coaxially inserted into one another.

23. The hard capsule as claimed in claim 21 or 22, characterized in that the capsule body and the capsule cap have, in the respective at least one side wall in the vicinity of their open end, a closure device which fits together and/or produces a connection which cannot be separated after the capsule parts have been pushed together.

24. The hard capsule as claimed in any of claims 21 to 23, characterized in that the capsule body comprises more than one compartment.

25. A molding (1) comprising a frustoconical body (2) with a rim (3), a side wall (4) and an inlet wall (5), where the inlet wall (5) comprises a flat or convex portion (6), and an adjunct wall (7) which is situated at a lower position and which seals the rim (3), where the flat or convex portion (6) has a recessed or profiled structure (8), where this recessed or profiled structure (8) facilitates puncture of this structure by blades which belong to the injection device and follows a substantially circular course (9), the diameter of which is defined by the diameter of the blades, the arrangement of which is likewise circular, where the frustoconical body (2) is obtainable by a process as claimed in any of claims 1 to 19.

Description

[0100] The process of the invention is moreover suitable for the production of moldings which have particularly good suitability as containers or capsules for coffee in the appropriate coffee machines. This particularly preferred embodiment of the moldings of the invention is described in more detail below with reference to the following drawings.

[0101] FIG. 1 is a schematic diagram of a particularly preferred embodiment of the moldings of the invention in plan view.

[0102] FIG. 2 is a schematic diagram of a particularly preferred embodiment of the moldings of the invention in cross-sectional view.

[0103] FIG. 1 is a plan view of a particularly preferred embodiment 1 of the moldings of the invention, comprising a frustoconical body 2 with a rim 3, a side wall 4, and an inlet wall 5, where the inlet wall 5 can comprise a flat or convex portion 6, and with an adjunct wall 7 which is situated at a lower position and which seals the rim 3, where the flat or convex portion 6 has a recessed or profiled structure 8, where this recessed or profiled structure 8 facilitates puncture of this structure by blades which belong to the injection device and follows a substantially circular course 9, the diameter of which is defined by the diameter of the blades, the arrangement of which is likewise circular, where in particular the frustoconical body 2 of the molding is obtainable by the process of the invention.

[0104] FIG. 2 is a cross section of a particularly preferred embodiment 1 of the moldings of the invention, comprising a frustoconical body 2 with a rim 3, a side wall 4, and an inlet wall 5, where the inlet wall 5 can comprise a flat or convex portion 6, and with an adjunct wall 7 which is situated at a lower position and which seals the rim 3, where the flat or convex portion 6 has a recessed or profiled structure 8, where this recessed or profiled structure 8 facilitates puncture of this structure by blades which belong to the injection device and follows a substantially circular course, the diameter of which is defined by the diameter of the blades, the arrangement of which is likewise circular, where in particular the frustoconical body 2 of the molding is obtainable by the process of the invention.

[0105] The adjunct wall 7 situated at a lower position advantageously seals the rim 3 of the capsule in a manner that is in essence gastight. It is moreover in particular possible that the frustoconical body 2 and/or the adjunct wall 7 of the embodiment 1 has/have been coated, advantageously with a gastight coating, for example by metallization, as described above. Gastight packaging prolongs the shelf life of oxidizable substances present in the capsule.

[0106] In a particularly preferred embodiment of the moldings of the invention, both the frustoconical body 2 and the adjunct wall 7 situated at a lower position are biodegradable in accordance with EN 13432, preferably completely biodegradable, so that the entirety of this embodiment of the moldings of the invention is biodegradable.

[0107] The principle of the invention will be explained in more detail below by reference to examples.

[0108] The following materials were used for the embodiment: poly(hydroxybutyrate-co-hexanoate), PHBH (AONILEX X 151 A, KANEKA); native potato starch (EMSLANDSTÄRKE); starch-containing polymer blend, GF106 (BIOPLAST GF106/02, BIOTEC); thermoplastic starch, TPS (BIOPLAST TPS, BIOTEC)

EXAMPLE 1 (TWO-STAGE PROCESS)

[0109] A Werner & Pfleiderer (COPERIOIV) ZSK 40 (corotating) twin-screw extruder, screw diameter 40 mm, L/D=42, was used to compound the following formulation A (metered proportions in percent by mass):

TABLE-US-00001 TABLE 1 Formulation A PHBH 69.8 Starch 30.2

[0110] The compounding parameters maintained here were as follows:

TABLE-US-00002 TABLE 2 ZSK 40 temperature profile Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Die 25° C. 170° C. 170° C. 160° C. 160° C. 160° C. 160° C. 160° C. 150° C.
Melt temperature on discharge from die: 155° C.
Rotation rate: 140 min.sup.−1
Throughput: 40 kg/h
Devolatilization: active (vacuum, zone 7)
Water content: smaller than 1% by weight
(measured after discharge from the extruder)

[0111] The polymer composition was initially isolated in the form of pellets.

[0112] The pellets were then processed to give two-part hard capsules in an ARBURG ALLROUNDER 270 M type injection-molding system.

[0113] The processing parameters set here were as follows:

TABLE-US-00003 TABLE 3 Processing parameters for injection molding Zone 1 Zone 2 Zone 3 Zone 4 25° C. 160° C. 160° C. 160° C.
Mold temperature: 45° C.
Cycle time: 30 s

Pressure: 300 bar

[0114] The resultant two-part hard capsules featured a smooth surface and excellent dimensional stability. In particular, it was easy to achieve sealing of the resultant hard capsules.

EXAMPLE 2 (TWO-STAGE PROCESS)

[0115] A Werner & Pfleiderer (COPERION) ZSK 40 (corotating) twin-screw extruder, screw diameter 40 mm, L/D=42, was used to compound the following formulations B to I (metered proportions in percent by mass):

TABLE-US-00004 TABLE 4 Formulations B C D E F G H I PHBH 98.5 94.5 89.5 74.5 98.5 94.5 89.5 74.5 GF106  1.5  5.5 10.5 25.5 — — — — TPS — — — —  1.5  5.5 10.5 25.5

[0116] The compounding parameters maintained here were as follows:

TABLE-US-00005 TABLE 5 ZSK 40 temperature profile Formulation Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Die B, F 25° C. 170° C. 170° C. 170° C. 170° C. 170° C. 165° C. 165° C. 155° C. C, G 25° C. 170° C. 170° C. 170° C. 165° C. 165° C. 165° C. 160° C. 150° C. D, H 25° C. 170° C. 170° C. 165° C. 165° C. 165° C. 160° C. 160° C. 150° C. E, I 25° C. 170° C. 170° C. 165° C. 160° C. 160° C. 160° C. 160° C. 150° C.
Melt temperature on discharge from die: from 153° C. to 158° C.
Rotation rate: 140 min.sup.−1
Throughput: 40 kg/h
Devolatilization: active (vacuum, zone 7)
Water content: smaller than 1% by weight
(measured after discharge from the extruder)

[0117] Polymer compositions B to I were initially isolated in the form of pellets.

[0118] The pellets B to I were then melted in a COLLIN 30 (DR. COLLIN) single-screw extruder, screw diameter 30 mm, L/D=33, and further processed by means of a MABAG slot die with slot width 30 cm to give flat films with thickness respectively 0.75 mm.

[0119] The processing parameters set here for the pellets B to I were as follows:

TABLE-US-00006 TABLE 6 COLLIN 30 temperature profile Zone 1 Zone 2 Zone 3 Zone 4 Die 165° C. 170° C. 170° C. 170° C. 165° C.
Rotation rate: 53 min.sup.−1

Slot die gap: 30 cm

[0120] Melt temperature on discharge from die: 157° C.
Film thickness: 750 μm

[0121] The flat films were then subjected to forming on an ILLIG KFG37 sheet thermoforming line to give coffee capsules. For this, the flat films were cut into relatively small pieces, and these were respectively exposed for 15 seconds to radiant heaters providing heat from above reaching a temperature of 500° C., and were then subjected to forming in the mold at a gauge pressure of −0.8 bar, relative to a reference pressure of 1 bar, thus forming the coffee capsules.