MOLD COMPOSITION COMPRISING A SUGAR COMPONENT

Abstract

A moulding composition comprising at least one sugar component in a weight proportion of at least 20% in relation to the weight of the moulding composition, and at least one aggregate as well as a mould for a moulding process, wherein the mould is a compact three-dimensional structure made of the moulding composition, and a process for moulding a workpiece with the mould.

Claims

1. A moulding composition comprising at least one sugar component in a weight proportion of at least 20%, in relation to the weight of the moulding composition, and at least one aggregate.

2. A moulding composition according to claim 1, wherein the at least one sugar component is selected from the group consisting of monosaccharides, disaccharides, oligosaccharides, sugar alcohols derived from a monosaccharide, a disaccharide or an oligosaccharide, hydrates thereof and mixtures thereof.

3. A moulding composition according to claim 1, wherein the at least one sugar component is a compound of the general formula I
C.sub.(n*a)H.sub.(n*a*2)+2b-2cO.sub.(n*a)-c  (I), wherein n is 1 to 10, preferably 1 or 2, a is 4, 5 or 6, b is 0 or 1, and c is n−1 or n, a hydrate of a compound of general formula I or a mixture of at least two compounds of general formula I and/or hydrates thereof.

4. A moulding composition according to claim 1, wherein the at least one sugar component is selected from the group consisting of sucrose, D-fructose, D-glucose, D-trehalose, cyclodextrins, erythritol, isomalt, lactitol, maltitol, mannitol, xylitol and mixtures thereof, particularly preferably D-trehalose, isomalt, erythritol, lactitol, mannitol and eutectic mixtures of sucrose and D-glucose.

5. A moulding composition according to claim 1, wherein the at least one sugar component has a melting point and a decomposition temperature range, wherein the melting point is below the decomposition temperature range.

6. A moulding composition according to claim 1, wherein the moulding composition furthermore comprises water, preferably water in a weight proportion of at most 10% in relation to the weight of the moulding composition.

7. A moulding composition according to claim 1, wherein the at least one sugar component is not hygroscopic or is hygroscopic only above a relative humidity of 80%.

8. A moulding composition according to claim 1, wherein the at least one aggregate is included in a weight proportion of at most 20%, preferably at most 10%, in relation to weight of the moulding composition.

9. A moulding composition according to claim 1, wherein the at least one aggregate is powdery or fibrous.

10. A moulding composition according to claim 1, wherein the at least one aggregate is selected from the group consisting of cellulose, charcoal, glass fibre, aramid, aluminium oxide, silicon dioxide and polyethylene, preferably cellulose and charcoal.

11. A mould for a moulding process, wherein the mould is a compact three-dimensional structure made of a moulding composition according to claim 1.

12. A mould according to claim 11, wherein the structure is a melt or a compressed structure of the moulding composition.

13. A mould according to claim 11, wherein the mould is a heterogeneous structure in which the aggregate is present as a dispersed phase, being distributed in the sugar component.

14. A process for moulding a workpiece, comprising the steps of providing at least one mould according to claim 11, contacting the mould with a material to be moulded, hardening the material to be moulded in order to obtain the workpiece, removing the mould from the workpiece.

15. A process according to claim 14, wherein the structure of the mould is destroyed during removing.

16. A process according to claim 15, wherein destroying the structure of the mould is effected by melting the sugar component by heating and removing, in particular pouring off, the moulding composition, dissolving the moulding composition with a hydrophilic solvent, preferably water, decomposing the sugar component by heating and optionally removing residues of the moulding composition, or a combination of those measures.

17. A process according to claim 14, wherein during contacting the at least one mould comes to lie within the material to be moulded and, optionally, a further mould is contacted with the material to be moulded from the outside.

18. A process according to claim 14, wherein the process for moulding a workpiece is used in the course of a production of a ceramic mould shell for investment casting, a lost core injection moulding process, a powder injection moulding process, a pressing process, or a production of a fibre-plastic composite material by means of lamination.

19. A process according to claim 14, wherein hardening to obtain the workpiece occurs mechanically, preferably by exerting pressure on an arrangement of the mould and the material to be moulded, which arrangement is created by contacting the mould with the material.

20. A moulding composition according to claim 1, wherein at least one sugar component is in a weight proportion of at least 50%, in relation to the weight of the moulding composition.

Description

[0121] The figures show stages of a process for moulding a workpiece, in detail:

[0122] FIG. 1 shows, in a side view, two moulds, namely an internally located mould and an external mould,

[0123] FIG. 2 shows, in cross-section, the moulds being contacted with a material to be moulded before hardening (A), after hardening (B) and removing the external mould, and after post-hardening (C) and complete removal of the mould from the workpiece (D), and

[0124] FIG. 3 shows the moulded workpiece in a side view.

EXAMPLE 1—PRODUCTION AND CHARACTERIZATION OF MOULDS

[0125] A. Production of Moulds (Test Bars)

[0126] Two different types of sugar were used for the test measurements. Commercially available isomalt (“Isomalt ST-M”, Beneo GmbH), on the one hand, and a mixture of sucrose (“Wiener Feinkristallzucker”, Agrana Zucker GmbH) and glucose (“Dextropur”, Dextro Energy GmbH & Co. KG), on the other hand, were used.

[0127] Isomalt ST-M contains approx. 2.5 wt % of water and was melted at 155° C. over night in closed aluminium containers in order to keep the water content constant during the melting process. The sucrose/glucose mixture was mixed with water at a ratio of 62 wt % of sucrose, 14 wt % of glucose and 24 wt % of water (known as “sugar boiling”). The sugar mixture was heated up to a temperature of 150° C. in a beaker (1000 ml, low-form) on a heatable laboratory magnetic stirrer under vigorous stirring (with considerable amounts of water evaporating), and then the resulting melt was processed further immediately. The melt thus obtained typically contains 2-3 wt % of water.

[0128] On the basis of those two sugar melts (“Isomalt ST-M” and sucrose/glucose), test bars having dimensions of 4.7 cm×2.5 cm×1.0 cm (haptic tests) and 7.0 cm×3.8 cm×3.5 cm (measurement of strengths and modulus of deformability) were then produced in series, with commercially available silicone moulds being used as negative moulds.

[0129] B. Characterization of Moulds without Aggregate

[0130] It was found that especially Isomalt ST-M was very brittle after casting and cooling so that the test bodies obviously had very high strengths (breaking by hand impossible), but after scratching or punctually damaging the surface with a sharp object, the test body could be broken very easily; furthermore, after a short and fast blow with a hard object (e.g., with a screwdriver), the test body shattered into numerous pieces just like glass. In this connection, it was also observed that test bodies made of Isomalt ST-M exhibited very strong variations with regard to those properties as described, which might indicate thermal stresses.

[0131] Therefore, an attempt was then made to remove those stresses by tempering. For this purpose, the produced test bodies were cooled once under ambient conditions (room temperature), once kept at 40° C. (24 h) and once hardened in the refrigerator (4° C., 24 h) in order to highlight differences. The hardness of the differently produced test bodies was evaluated haptically (breaking by hand, scratching the surface and breaking by hand, fast blow). However, tempering the test bodies obviously had no positive effect on the hardness and brittleness as well as the variations of those properties of the examined test bodies.

[0132] In a further test series, Isomalt ST-M was melted in a closed vessel and mixed with water in order to obtain water contents of 5 wt % or 10 wt %, respectively. Furthermore, Isomalt ST-M was melted in an open vessel in order to obtain a water content of 0 wt %. With the different types of Isomalt ST-M (0, 2.5, 5, 10 wt % of water), test bodies were produced, which, in turn, were subsequently assessed haptically for their hardness. The test bodies with higher water contents (5 wt % or 10 wt % respectively) were significantly softer than standard Isomalt ST-M, obviously no longer brittle, but unfortunately no longer strong enough, either, because they could be deformed or broken by hand comparatively easily. The test bodies without water were highly susceptible to impacts or mechanical stress, which suggests increased brittleness.

[0133] In a further analogous test series with a sucrose/glucose mixture, the same effect or, respectively, trend was observed as with Isomalt ST-M.

[0134] Furthermore, when working with and storing test bodies made of Isomalt ST-M in comparison to sucrose/glucose mixtures, significant differences could be determined with regard to hygroscopicity: While, in practice, the former showed a negligible tendency to absorb water, a sticky consistency was observed on sucrose/glucose test bodies within a short time upon contact with the open atmosphere, which sticky consistency led to a progressive plasticization of the surface of the test bodies within hours so that they became unusable. In practice, moulds made of sucrose/glucose would therefore have to be processed immediately or packaged in an airtight manner for storage, especially in case of increased air humidity.

[0135] C. Haptic Specification of Moulds Made of a Moulding Composition with an Aggregate

[0136] In a test series, the various aggregates (Table 4) were examined with Isomalt ST-M and sucrose-glucose (as described above) as the matrix (sugar component).

TABLE-US-00004 TABLE 4 Examined aggregates Aggregate Source of supply activated carbon Norit ® CASPF Cabot Corporation, Alpharetta Georgia, USA aramid-fibre filler F AR 700/250 Schwarzwälder Textil-Werke, Schenkenzell, (1.5 mm) Germany calcium carbonate powder, no. 21060 Merck KGaA, Darmstadt, Germany.sup.1 carbon-filler SFR 0.20 MFC (0.2 mm) Schwarzwälder Textil-Werke, Schenkenzell, Germany carbon-short cut SFC 3 EPB (3 mm) Schwarzwälder Textil-Werke, Schenkenzell, Germany cellulose fibre medium, no. C6288 Merck KGaA, Darmstadt, Germany.sup.1 glass fibre-short cut FGCS ECR 416/3 Schwarzwälder Textil-Werke, Schenkenzell, (3 mm) Germany glass fibre ground no. 2101101 (0.2 mm) R&G GmbH, Waldenbruch, Germany glass fibre cuttings no. 2101001 (3 mm) R&G GmbH, Waldenbruch, Germany carbon fibre ground no. 2101351 R&G GmbH, Waldenbruch, Germany (0.2 mm) carbon fibre cuttings no. 210137-NA-2 R&G GmbH, Waldenbruch, Germany (3 mm) polyethylene powder, no. 434272 Merck KGaA, Darmstadt, Germany.sup.1 polytetrafluoroethylene powder, no. Merck KGaA, Darmstadt, Germany.sup.1 430935 polyvinylidene fluoride powder, no. Merck KGaA, Darmstadt, Germany.sup.1 182702 titanium (IV) oxide powder, no. T8141 Merck KGaA, Darmstadt, Germany.sup.1 silica gel 60 powder, no. 60738 Merck KGaA, Darmstadt, Germany.sup.1 aluminium oxide powder, no. 06320 Merck KGaA, Darmstadt, Germany.sup.1 .sup.1ordered via Sigma-Aldrich, Inc.

[0137] For the production of the moulding composition, an appropriate amount of Isomalt ST-M was melted as described above, provided with the appropriate amount of aggregate and carefully distributed evenly in a beaker with a glass rod. The amount of aggregate was restricted to a maximum of 10 wt %, but some aggregates could only be distributed evenly in the sugar matrix in smaller quantities.

[0138] In order to prevent premature hardening of the material, the produced mixture was quickly poured into appropriate silicone moulds and small test bars were produced (4.7 cm×2.5 cm×1 cm). The mechanical properties of the test bars were haptically evaluated analogously to the process described above (breaking by hand, scratching the surface and breaking by hand, fast blow) and compared to the properties of the corresponding mould made of the sugar component alone (Table 5).

TABLE-US-00005 TABLE 5 Results of the haptic-mechanical testing of sugar bars with various aggregates. comparison to a sugar Composition matrix without aggregate Isomalt ST-M + 10 wt % of activated carbon strongly improved properties Isomalt ST-M + 0.5 wt % of aramid improved properties Isomalt ST-M + 10 wt % of calcium carbonate improved properties Isomalt ST-M + 2 wt % of carbon-filler SFR strongly improved properties Isomalt ST-M + 2 wt % of carbon-short cut strongly improved properties Isomalt ST-M + 10 wt % of cellulose fibre strongly improved properties Isomalt ST-M + 10 wt % of glass fibre (0.2 mm) improved properties Isomalt ST-M + 10 wt % of glass fibre (3 mm) improved properties Isomalt ST-M + 10 wt % of carbon fibre (0.2 mm) strongly improved properties Isomalt ST-M + 2 wt % of carbon fibre (3 mm) strongly improved properties Isomalt ST-M + 10 wt % of polyethylene strongly improved properties Isomalt ST-M + 10 wt % of polytetrafluoroethylene substantially poorer properties Isomalt ST-M + 10 wt % of polyvinylidene fluoride substantially poorer properties Isomalt ST-M + 10 wt % of titanium(IV)oxide improved properties Isomalt ST-M + 10 wt % of silica gel 60 powder strongly improved properties Isomalt ST-M + aluminium oxide powder strongly improved properties sucrose-glucose + 10 wt % of cellulose strongly improved properties

[0139] D. Mechanical Specification of Moulds Made of a Moulding Composition with an Aggregate

[0140] Larger test bars (7.0 cm×3.8 cm×3.5 cm) were produced from some candidates that had performed better in the haptic tests compared to the sugar matrix without additives. Compressive strength, flexural strength and modulus of deformability were measured for each of those as described. A test system from Form & Test Prfsysteme was used for determining the compressive strengths (www.formtest.de). Model: DigiMaxx C-20, max. piston stroke 15 mm, max. force 600 kN, and feed pressure 1 MPa/s according to DIN EN 993-5 (1998). For the measurements, test bars with the following dimensions were cast: 7 cm×3.8 cm×3.5 cm.

[0141] For determining the flexural strength or, respectively, the modulus of deformability, a flexural strength machine from Messphysik (www.messphysik.com, Model Midi 5) with a measuring cell of up to 500 kN was used. In this case, the operation was performed with a feed pressure of 0.15 MPa/s (according to DIN EN 993-6, 1995). The def-modulus (also modulus of deformability) is related to the modulus of elasticity and, like the modulus of elasticity, is the first derivative of the stress with respect to expansion or, respectively, deformation. In this connection, the modulus of deformability is determined by establishing a regression line in the area of the curve at ε.sub.Br/2, wherein ε.sub.Br is the deformation that occurs at break.

[0142] The results of the corresponding measurements are shown in Table 6 below:

TABLE-US-00006 TABLE 6 Results for compressive and flexural strengths and modulus of deformability (±standard deviation absolute and relative) for various moulding compositions (measured as bars) compressive flexural modulus of strength strength deformability Composition [N/mm.sup.2] [N/mm.sup.2] [N/mm.sup.2] Isomalt ST-M  4.4 ± 2.5 (±57%) 14.0 ± 15.3 (±109%) 2464 ± 2549 (±103%) Isomalt ST-M + 10 wt % 29.9 ± 17.7 (±59%) 13.4 ± 4.1 (±31%) 2381 ± 1562 (±66%) of cellulose Isomalt ST-M + 10 wt % 49.6 ± 12 (±24%)  7.2 ± 4.3 (±60%) 2060 ± 883 (±42%) of glass fibre (0.2 mm) Isomalt ST-M + 10 wt % 42.3 ± 6.7 (±16%)  7.2 ± 0.7 (±10%) 1990 ± 146 (±7%) of glass fibre (3 mm) Isomalt ST-M + 10 wt % 79.9 ± 13.2 (±17%) 20.5 ± 3.8 (±19%) 3596 ± 1294 (±36%) of carbon fibre (powder) Isomalt ST-M + 2 wt % 27.7 ± 9.6 (±35%)  8.8 ± 0.4 (±5%) 3435 ± 451 (±13%) of carbon fibre (3 mm) Isomalt ST-M + 0.5 wt % 11.1 ± 5.1 ( 46%)  5.7 ± 2 (±35%) 3686 ± 2266 (±61%) of aramid filler Isomalt ST-M + 10 wt % 20.2 ± 8.8 (±43%)  3.2 ± 0.4 (±13%) 1335 ± 212 (±16%) of polyethylene sucrose-glucose  9.9 ± 8.9 (±90%)  5.3 ± 0.7 (±13%)  290 ± 231 (±80%) sucrose-glucose + 10 37.7 ± 5.7 (±15%)  7.7 ± 1.5 (±19%) 1377 ± 469 (±34%) wt % of cellulose

[0143] 4-Fold Determination, Isomalt ST-M 10-Fold Determination

[0144] It was observed that, in comparison to the pure sugar component—but also in comparison to a moulding composition made of a sugar component and water—the compressive strength is increased for all examined aggregate and, respectively, sugar components. The moulding compositions according to the invention are therefore more suitable for processes in which a high compressive strength is required.

[0145] The flexural strength shows a very high scattering for moulds made of isomalt, which is indicative of mechanical stresses within the mould. By means of the aggregates, even though a quantitative effect on the flexural strength is not achieved for all materials, it was found that the variation was reduced between different measurements. The better reproducibility of the flexural strength amounts to an optimization of the mechanical properties of the moulds in comparison to those without an aggregate. For some moulding compositions (with cellulose and powdered carbon fibres), flexural strengths are achieved that are comparable in terms of magnitude to the tensile strengths of metallic fusible alloys (cf. Table 1).

[0146] The addition of an aggregate shows different effects on the modulus of deformability, depending on the sugar component. For isomalt, the modulus of deformability tends to decrease, i.e., elasticity is increased, but especially a reduction in the variation is achieved also in this case. For sucrose/glucose, the aggregate (10 wt % of cellulose) has an opposite effect. In both cases, however, the modulus of deformability achieved with an aggregate is in the order of magnitude of the modulus of elasticity specified for plastic materials that are used as lost moulds (cf. Table 2).

EXAMPLE 2—PROCESS FOR MOULDING A CERAMIC WORKPIECE

[0147] Technical ceramics are often produced using isostatic pressing (see also point 3 above). The mould according to the invention was used in such a process as an internally located mould within the ceramic pressed part, which is to be described herein in further detail with reference to the figures.

[0148] At first (FIG. 1), a mould 1 according to the invention was produced, as described in Example 1, from a moulding composition by means of melting and casting into a silicone mould with isomalt STM as the sugar component and carbon fibre (ground carbon fibre) as the aggregate. The moulding composition was brought to 160° C. in a controlled manner (5 hours), stirred with a simple laboratory mixer and poured out into a new silicone mould (20×15×120 mm). Upon cooling of the melt, a high-strength and stiff cast arises, i.e., the bar-shaped mould 1. In addition, an external rubber mould 2 was provided, in which the mould according to the invention is arranged centrally.

[0149] In the second step (FIG. 2A), a ceramic granulate material 3 was poured into the external mould as the material to be moulded so that an arrangement according to FIG. 2B was created. The external mould is filled up to the edge. The ceramic granulate material was based on alumina graphite with a resin binder.

[0150] The rubber mould is closed with a complementary rubber mould and wrapped in a waterproof sheet. The arrangement was then pressed by means of water pressure of 360 bar.

[0151] The rubber mould 2 could be removed easily due to its flexibility. The ceramic mass 3 encloses the mould 1 after the pressing process without any visible deformation of the mould (FIG. 2 B)

[0152] In order to remove the mould 2, the arrangement is heated to 240° C. in a hardening oven and, in doing so, the moulding composition 4 flows out of the workpiece 3 to be moulded incompletely, with the mould 2 being lost. The residues can be dissolved in the water or only after the subsequent firing.

[0153] Hardening is followed by firing, wherein the product is heated to 1000° C. under reductive conditions. In doing so, all of the residues evaporate for the most part, and only small amounts of ash remain in the product 5 (FIG. 2 D). They can be removed easily by means of a water jet.

[0154] The final product 5 (see also FIG. 3) can assume an internal geometry of varying complexity by means of this technology. The slight shrinkage of the resulting cavity is due to the shrinkage of the ceramic material used, rather than due to the deformation of the meltable tool. Therefore, the shrinkage can be taken into account when planning the final geometry in order to achieve a precise geometry.