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 and such that the polyhydroxyalkanoate and the starch-containing polymer together constitute at least 90% by weight of the polymer composition; b. homogenizing the polymer composition with use of thermal and/or mechanical energy and adjusting the water content of the polymer composition to less than 5% by weight of the polymer composition, wherein starch or functionalized starch present in the starch-containing polymer is destructured during the homogenization; c. introducing the homogenized polymer composition into a mold; d. molding the homogenized polymer composition in the mold to form a molding that consists essentially of the homogenized polymer composition; and e. removing the molding from the mold.

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

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

4. The process as claimed in claim 1, wherein the homogenization of the polymer composition is carried out at a temperature of from 80 to 220° C.

5. The process as claimed in claim 1, wherein the homogenization of the polymer composition is carried out in an extruder.

6. The process as claimed in claim 1, wherein 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.

7. The process as claimed in claim 1, wherein the polymer composition comprises less than 10% by weight, or less than 6% by weight, 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, or 300 g/mol or less.

8. The process as claimed in claim 1, wherein, before the introduction of the homogenized polymer composition into the mold, the water content of the polymer composition is adjusted to less than 1% by weight, based on the total weight of the polymer composition.

9. The process as claimed in claim 1, wherein 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, or from 1 to 6.

10. The process as claimed in claim 1, wherein 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.

11. The process as claimed in claim 1, wherein the polyhydroxyalkanoate of the polymer composition is a copolymer.

12. The process as claimed in claim 1, wherein the weight-average molar mass of the polyhydroxyalkanoate of the polymer composition is from 60,000 to 500,000 g/mol, or from 120,000 to 300,000 g/mol.

13. The process as claimed in claim 1, wherein the melting point of the polyhydroxyalkanoate of the polymer composition is from 120 to 200° C., or from 150 to 180° C.

14. The process as claimed in claim 1, wherein introducing the homogenized polymer composition into the mold and molding the homogenized polymer composition comprise injection molding.

15. The process as claimed in claim 14, wherein the pressure with which the polymer composition is injected into the mold is more than 1 bar, or more than 100 bar.

16. The process as claimed in claim 14, wherein the pressure with which the polymer composition is injected into the mold is from 150 to 3000 bar.

17. The process as claimed in claim 14, wherein the temperature of the polymer composition when said composition is injected into the mold is above 23° C., or above 50° C.

18. The process as claimed in claim 14, wherein the temperature of the polymer composition when said composition is injected into the mold is from 80 to 200° C.

19. The process as claimed in claim 1, wherein the polymer composition is formed into 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.

20. The process as claimed in claim 19, wherein the capsule body and the capsule cap are manufactured so as to be coaxially inserted into one another.

21. The process as claimed in claim 19 wherein, 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.

22. The process as claimed in claim 19, wherein the capsule body comprises more than one compartment.

23. The process as claimed in claim 1, the molding comprising a frustoconical body with a rim, a side wall and an inlet wall, where the inlet wall comprises a flat or convex portion, where the flat or convex portion has a recessed or profiled structure.

24. 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 and such that the polyhydroxyalkanoate and the starch-containing polymer together constitute at least 90% by weight of the polymer composition; b. homogenizing the polymer composition with use of thermal and/or mechanical energy and adjusting the water content of the polymer composition to less than 5% by weight of the polymer composition, wherein starch or functionalized starch present in the starch-containing polymer is destructured during the homogenization; c. forming the homogenized polymer composition from step b. into a sheet or film consisting essentially of the polymer composition; d. thermoforming the sheet or film consisting essentially of the polymer composition in a mold to form a molding; and e. removing the molding from the mold.

25. 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, wherein the polyhydroxyalkanoate and the starch-containing polymer are together included in an amount of from 90% to 100% by weight of the polymer composition, wherein the polymer composition comprises less than 10% by weight, based on the total weight of starch and plasticizer, of a carbon-containing plasticizer with molar mass 500 g/mol or less; b. homogenizing the polymer composition with use of thermal and/or mechanical energy and adjusting the water content of the polymer composition to less than 5% by weight of the polymer composition; c. injection molding the homogenized polymer composition in a mold to form a molding that consists essentially of the polymer composition; and d. removing the molding from the mold.

Description

(1) 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.

(2) FIG. 1 is a schematic diagram of a particularly preferred embodiment of the moldings of the invention in plan view.

(3) FIG. 2 is a schematic diagram of a particularly preferred embodiment of the moldings of the invention in cross-sectional view.

(4) 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.

(5) 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.

(6) 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.

(7) 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.

(8) The principle of the invention will be explained in more detail below by reference to examples.

(9) 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)

(10) A Werner & Pfleiderer (COPERION) 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):

(11) TABLE-US-00001 TABLE 1 Formulation A PHBH 69.8 Starch 30.2

(12) The compounding parameters maintained here were as follows:

(13) 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)

(14) The polymer composition was initially isolated in the form of pellets.

(15) The pellets were then processed to give two-part hard capsules in an ARBURG ALLROUNDER 270 M type injection-molding system.

(16) The processing parameters set here were as follows:

(17) 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

(18) 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)

(19) 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):

(20) 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

(21) The compounding parameters maintained here were as follows:

(22) 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)

(23) Polymer compositions B to I were initially isolated in the form of pellets.

(24) 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.

(25) The processing parameters set here for the pellets B to I were as follows:

(26) 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
Melt temperature on discharge from die: 157° C.
Film thickness: 750 μm

(27) 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.