MOLD FOR MANUFACTURING A BODY MADE OF A POROUS MATERIAL

Abstract

A mold for manufacturing a body made of a porous material derived from precursors of the porous material in a sol-gel process carried out within the mold can have a lower part defining an interior volume for receiving the precursors of the porous material, wherein the interior volume defines the shape of the body to be manufactured, and at least a first opening through which the body is removable from the lower part. Surfaces of the lower part facing the interior volume are at least partially provided with a coating made of a material that is electrically dissipative and non-sticky to a gel formed from the precursors of the porous material and/or the body.

Claims

1-15. (canceled)

16. A mold configured for manufacturing a body made of a porous material derived from one or more precursors of the porous material in a sol-gel process carried out within the mold, the mold comprising: a lower part defining an interior volume, configured for receiving the precursors of the porous material, the interior volume defining a shape of the body to be manufactured; and a first opening configured for removal of the body from the lower part, wherein surfaces of the lower part facing the interior volume at least partially comprise a coating comprising a material that is electrically dissipative and non-sticky to a gel formed from the precursors of the porous material and/or the body, wherein the material of the coating has an electrical resistivity of not more than 10.sup.8 Ωm.

17. The mold of claim 16, wherein the lower part comprises the first opening.

18. The mold of claim 16, wherein the lower part is made of metal or polymer.

19. The mold of claim 16, wherein the interior volume defines a cuboid shape for the body.

20. The mold of claim 19, wherein the shape has a length in a range of 10 cm to 100 cm and a width in a range of 10 cm to 100 cm and/or a height of the shape is variable.

21. The mold of claim 16, further comprising: a cover part configured to close the first opening; a second opening; and a lid configured to close the second opening.

22. The mold of claim 21, wherein the lower part comprises the second opening.

23. The mold of claim 21, wherein the first opening comprises a first opening area, wherein the second opening comprises a second opening area, and wherein the second opening area smaller than the first opening area.

24. The mold of claim 21, further comprising: a first sealing configured to be arranged between the lower part and the cover part, wherein the first sealing is configured to provide a gas tight closing of the first opening with the cover part.

25. The mold of claim 16, wherein the lower part comprises a bottom and side walls extending from the bottom, and wherein an upper rim of the side walls opposite to the bottom defines the first opening.

26. The mold of claim 16, wherein the surfaces of the lower part comprise the coating at portions configured for contacting the gel formed from the precursors of the porous material.

27. The mold of claim 16, wherein the material of the coating is non-corroding.

28. The mold of claim 16, wherein the coating comprises a halogen-comprising polymer and an inorganic filler.

29. The mold of claim 16, wherein the coating is reusable.

30. The mold of claim 16, wherein the lower part comprises a metal.

31. The mold of claim 16, wherein the lower part comprises a polymer.

32. The mold of claim 21, wherein the cover part comprises the second opening.

33. The mold of claim 16, wherein the coating comprises an inorganic filler, and a polytetrafluoroethylene, perfluoro alkoxy polymer, and/or a fluorinated ethylene propylene polymer.

34. The mold of claim 16, wherein the coating is reusable for at least 50 cycles of the sol gel process.

Description

SHORT DESCRIPTION OF THE FIGURES

[0182] Further features and embodiments of the invention will be disclosed in more detail in the subsequent description, particularly in conjunction with the dependent claims. Therein the respective features may be realized in an isolated fashion as well as in any arbitrary feasible combination, as a skilled person will realize. The embodiments are schematically depicted in the figures. Therein, identical reference numbers in these figures refer to identical elements or functionally identical elements.

[0183] In the Figures:

[0184] FIG. 1 shows a perspective view of a mold according to the present invention in an open state; and

[0185] FIG. 2 shows a perspective view of the mold in a closed state.

DETAILED DESCRIPTION

[0186] As used in the following, the terms “have”, “comprise” or “include” or any arbitrary grammatical variations thereof are used in a non-exclusive way. Thus, these terms may both refer to a situation in which, besides the feature introduced by these terms, no further features are present in the entity described in this context and to a situation in which one or more further features are present. As an example, the expressions “A has B”, “A comprises B” and “A includes B” may both refer to a situation in which, besides B, no other element is present in A (i.e. a situation in which A solely and exclusively consists of B) and to a situation in which, besides B, one or more further elements are present in entity A, such as element C, elements C and D or even further elements.

[0187] Further, it shall be noted that the terms “at least one”, “one or more” or similar expressions indicating that a feature or element may be present once or more than once typically will be used only once when introducing the respective feature or element. In the following, in most cases, when referring to the respective feature or element, the expressions “at least one” or “one or more” will not be repeated, non-withstanding the fact that the respective feature or element may be present once or more than once.

[0188] Further, as used in the following, the terms “particularly”, “more particularly”, “specifically”, “more specifically” or similar terms are used in conjunction with additional/alternative features, without restricting alternative possibilities. Thus, features introduced by these terms are additional/alternative features and are not intended to restrict the scope of the claims in any way. The invention may, as the skilled person will recognize, be performed by using alternative features. Similarly, features introduced by “in an embodiment of the invention” or similar expressions are intended to be additional/alternative features, without any restriction regarding alternative embodiments of the invention, without any restrictions regarding the scope of the invention and without any restriction regarding the possibility of combining the features introduced in such way with other additional/alternative or non-additional/alternative features of the invention.

[0189] The term “mold” as used herein refers to a hollowed-out block or container that is configured to be filled with a liquid or pliable material for a sol-gel process provided by precursors of a sol gel. Particularly, the sol-gel process is carried out within the mold. During the sol-gel process the precursors form a sol which subsequently starts to gel. Thus, the liquid hardens or sets inside the mold, adopting its shape defined by the interior volume thereof. The mold is basically used to carry out the sol-gel process. However, it is to be noted that the solvent may be removed from the thus formed gel with the gel remaining within the mold or with the gel removed from the mold. In the present invention, the mold may consist of more than one part, wherein the interior volume is defined by a lower part.

[0190] The term “sol-gel process” as used herein refers to a method for producing solid materials from small molecules. In the present case, the method is used for the fabrication of porous materials such as aerogels, xerogels and/or kryogels. The process involves conversion of monomers as precursors into a colloidal solution, the so-called sol, that subsequently reacts to an integrated network, the so-called gel, of either discrete particles or network polymers. In this chemical procedure, the sol gradually evolves towards the formation of a gel-like diphasic system containing both a liquid phase and solid phase whose morphologies range from discrete particles to continuous polymer networks. This gel-like diphasic system is called gel. Particularly, the gel encapsulates or surrounds the solvent within pores which are connected to one another, i.e. the pores form an interpenetrating network. Removal of the remaining liquid phase, i.e. the solvent, requires a drying process, which is typically accompanied by a certain amount of shrinkage and densification. The rate at which the solvent can be removed is ultimately determined by the distribution of porosity in the gel. The ultimate microstructure of the final component will clearly be strongly influenced by changes imposed upon the structural template during this phase of processing.

[0191] The term “body” as used herein refers to a solid object formed by an identifiable collection of matter, which may be constrained by an identifiable boundary, and may move or may be moved as a unit by translation or rotation, in 3-dimensional space.

[0192] The term “porous” as used herein refers to material characteristics of having pores. As the solvent may be removed from the gel either with the gel being or remaining within the mold or after the gel is removed from the mold, the term “porous” covers both pores being filled with a liquid, particularly, the solvent, or a gas such as air. The pores may be connected to one another so as to form a type of network.

[0193] The term “coating” as used herein refers a covering that is applied to the inner surfaces of the lower part of the mold. Particularly, the coating may be applied at least to those areas of the lower part intended to come into contact with the precursors of the porous material and the body made thereof. Needless to say, the coating may be applied to the total inner surfaces of the lower part defining the interior volume.

[0194] The term “electrically dissipative” as used herein refers to material characteristics, wherein electric charges are allow to flow to ground but more slowly in a more controlled manner if compared to electrically conductive materials.

[0195] The term “non-sticky” as uses herein refers to characteristics wherein one part does not adhere to another part. Thus, both parts are in loose contact to one another. According to the present invention, the coating does not stick to the gel formed or resulting from the precursors filled into the mold. In case the solvent used with the sol gel process is removed with the gel being within the mold, the coating is configured not to stick to the thus formed body in order to allow the body being removed from the mold.

[0196] The terms “width” and “length” of the shape of the body as used herein refer to dimensions perpendicular to a height or thickness of the shape of the body.

[0197] The term “opening area” as used herein refers to the area of an opening defined by the boundary of the opening.

[0198] The term “sealing” as used herein refers to a device that helps join two parts together by preventing leakage, containing pressure, or excluding contamination.

[0199] The term “gas-tight” as used herein refers to characteristics of a material to be impermeable to gases. Needless to say, the impermeability is not feasible to a complete or absolute extension but the impermeability is to be understood in the sense of an extension as far as technically feasible.

[0200] FIG. 1 shows a perspective view of a mold 10 for manufacturing a body made of a porous material derived from precursors of the porous material in a sol-gel process carried out within the mold 10 according to the present invention. The mold 10 is shown in an open state. The mold 10 comprises a lower part 12. The lower part 12 is made of metal. The lower part 12 defines an interior volume 14 for receiving the precursors of the porous material. The interior volume 14 defines the shape of the body to be manufactured. Particularly, the lower part 12 comprises a bottom 16 and side walls 18 extending from the bottom 16. The interior volume 14 is defined by the bottom 16 and the side walls 18. The mold 10 further comprises at least a first opening 20 through which the body is removable from the lower part 12. In the present example, the lower part 12 comprises the first opening 20. Particularly, an upper rim 22 of the side walls 18 opposite to the bottom 16 defines the first opening 20.

[0201] Surfaces 24 of the lower part 12 facing the interior volume 14 are at least partially provided with a coating 26 made of a material being electrically dissipative and non-sticky to a gel formed from the precursors of the porous material and/or the body. More particularly, the surfaces 24 of the lower part 12 comprise the coating 26 at least at areas intended for coming into contact with the gel formed from the precursors of the porous material. With other words, the coating 26 does not need to cover the complete surfaces 24 of the lower part which face the interior volume 14 but may only cover those portions or areas which are intended to come into contact with the precursors of the porous material. The material of the coating 26 comprises an electrical resistivity of not more than 10.sup.8 Ωm such as 10.sup.6 Ωm. The material of the coating 26 is non-corroding. The material of the coating 26 comprises a shore hardness in a range of D60 to D80 such as D70. The coating 26 comprises a thickness in a range of 20 μm to 70 μm such as 50 μm. The coating 26 is a reusable coating. Particularly, the coating 26 is reusable for at least 50 and preferably at least 100 cycles of the sol gel process. The coating preferably comprises at least one halogen-containing polymer and at least one inorganic filler. More preferably, the halogen-containing polymer is a fluorinated polymer such as for example polytetrafluoroethylene, a perfluoro alkoxy polymer or a fluorinated ethylene propylene polymer. The coating preferably comprises at least one inorganic filler and at least one polymer selected from the group consisting of polytetrafluoroethylene, perfluoro alkoxy polymers and fluorinated ethylene propylene polymers. Particularly preferred are fluorinated ethylene propylene polymers such as perfluoro ethylene propylene. In the present embodiment, the coating 26 is made of a fluorinated polymer with conductive additive and anti-scratch additive. Such a material is commercially available under the name Rhenolease MK IIIG clear SiC/leitf. (hereinafter called Rhenolease) from the company Rhenotherm Kunststoffbeschichtungs GmbH, 47906 Kempen, Germany.

[0202] Basically, the interior volume 14 may define any shape for the body such as round, oval, elliptical, polygonal, polygonal with rounded edges. In the present example, the interior volume 14 defines a cuboid shape for the body. The shape has a length 28 in a range of 10 cm to 100 cm such as 60 cm and a width 30 in a range of 10 cm to 100 cm such as 40 cm. A height 32 of the shape is variable and may be adjusted by means of the filling level of the precursors within the lower part 12.

[0203] The mold 10 further comprises a cover part 34 configured to close the first opening 20, a second opening 36, and a lid 38 configured to close the second opening 36. In the present example, the cover part 34 comprises the second opening 36. The first opening 20 comprises a first opening area and the second opening 36 comprises a second opening area. The second opening area is smaller than the first opening area. The mold 10 further comprises at least a first sealing 40 configured to be arranged between the lower part 12 and the cover part 34. The first sealing 40 is configured to provide a gas tight closing of the first opening 20 by means of the cover part 34. Optionally, the mold 10 may further comprises a second sealing (not shown in detail) configured to be arranged between the lid 38 and the cover part 34 and configured to provide a gas tight closing of the second opening 36 by means of the lid 38.

[0204] FIG. 2 shows a perspective view of the mold 10 in a closed state. Particularly, the cover part 34 is arranged on the lower part 12 such that the first opening 20 is closed. The cover part 34 is removably mounted to the lower part 12. For example, the cover part 34 may be connected to the lower part 12 by means of a snap-fit connection, screws, hooks or the like. Further, the lid 38 closes the second opening 36.

[0205] The mold 10 may be used as follows. The cover part 34 is disposed onto the lower part 12 with the first opening 20 being closed. The precursors of the porous material, which are solved in a solvent, are filled into the lower part 12 up to a predetermined amount through the second opening 36. Subsequently, the second opening 36 is closed by the lid 38. Thereby, any solvent vapor is prevented from leaking or releasing from the mold 10. Then, the sol-gel reaction takes place wherein the precursors first form a sol with the solvent and subsequently form a gel. After gelling, the gel is hardened for a predetermined time such as at least 2 hours and preferably at least 8 hours. The hardening causes a kind of ageing of the gel which is necessary for the sol-gel reaction to proceed far enough such that the gel can be removed from the mold. If the sol-gel reaction was not to proceed far enough, the gel might not be sufficiently mechanically stable for handling, particularly for drying, or unreacted material could leak out of the gel during drying or could cause other problems such as negative impact on performance, e.g. fire behavior, unwanted emissions. After hardening, the cover part 34 is removed from the lower part 12. Thereby, the first opening 20 is exposed again. Then, the solvent is removed from the gel. The solvent may be removed by drying the gel in an oven or the like. It is to be noted that the solvent may be removed while the gel is in the lower part 12 or the gel may be removed from the lower part 12 before the gel is dried. After the solvent is removed from the gel, the body is formed. If the gel has been dried within the lower part 12, the body may subsequently be removed from the mold 10 and lower part 12, respectively. Due to the specific coating 26, neither the gel formed from the precursors within the lower part 12 nor the body sticks to the mold 10. If it is intended to remove the solvent with the gel being removed from the lower part 12 of the mold 10, the material of the coating may be selected such that it merely does not stick to the formed gel.

[0206] The mold 10 may be modified as follows. The lower part 12 may be made of a polymer. The coating 26 may completely cover the surfaces 24 facing the interior volume 14 or may even cover the complete lower part 12. The mold 12 may be used without the cover part 34 if an excessive release of any solvent vapor is otherwise prevented. The second opening 36 may be provided at the lower part 12. The shape of the body may be any shape such as square, rounded or the like. The mold 10 may comprise more parts than the lower part 12 and the cover part 34 such as an intermediate part arrangeable between the lower part 12 and the cover part 34.

EXAMPLES

[0207] The mold 10 and more particularly the material of the coating 26 are specified in further detail as follows.

[0208] The following components were prepared:

[0209] Component 1: To methylethylketone were added 3-4% MDEA, 1.5-2.5% potassium sorbate solution (20% in monoethylene glycol), 1.8-3.5% n-butanol.

[0210] Component 2: To methylethylketone were added 15-20% polymeric MDI.

[0211] Components 1 and 2 were combined at room temperature and directly poured into a mold to form a gel slab. The mold was covered to prevent evaporation of the solvent from the gel. After 1 h, the cover was removed and the mold was inverted on a flat surface to demold the gel slab.

[0212] Table 1 gives a brief summary of the analyzed molds and coatings as well as the results of the analyzed examples. The bodies have been produced from the components described above.

[0213] In the first column from the left, the respective materials of the lower part 12 and the coating 26, respectively, are given. In the second column from the left, the respective dimensions of the analyzed molds are given. In the third column from the left, other comments on the molds and coatings, respectively, are given. In the fourth column from the left, the number the bodies were removable from the lower part 12 due to the coating 26 is given. In the fifth column from the left, it is given whether the respective materials of the lower part 12 and the coating 26 are robust to scratching or not. In the sixth column from the left, it is given whether the respective materials of the lower part 12 and the coating 26 are electrically dissipative or not. In the seventh column from the left, remarks on the demolding characteristics are given. As can be taken from the last line of Table 1, using a fluorinated polymer with conductive additive and anti-scratch additive as is present with Rhenolease provides significant advantages as the number of removals is significantly higher than with the other materials, it is robust to scratching and electrically dissipative.

TABLE-US-00001 TABLE 1 Number of successful Resistant to Electrically Material/Coating Gel dimensions gel removals* scratching dissipative Result/remarks Polyethylene foil in 60 × 40 × 1 cm 1 No No Gel demolds, imperfect PE polymer or metal mold foil alignment with mold will lead to marks in gel Polyethylene 60 × 50 × 1.3 cm 0 No No Gel sticks (5 mm thickness) Polypropylene 50 × 35 × 1.5 cm 1 No No Gel demolds once, sticks afterwards Aluminum mold 60 × 40 × 1 cm 0 Yes Yes Gel sticks Aluminum mold pre- 60 × 40 × 1 cm 0 Yes Yes Gel sticks coated with PTFE spray Steel mold 60 × 40 × 1 cm 0 Yes Yes Gel sticks Steel mold pre-coated 60 × 40 × 1 cm 0 Yes Yes Gel sticks with PTFE spray Polytetrafluoroethylene 60 × 40 × 1 cm 1-6  No No Gel demolds 6 times, (PTFE)-coated steel mold sticks afterwards Emaille-coated steel mold 39 × 26 × 1 cm 0 Yes Yes Gel sticks Ceramic mold diameter 20 cm 1 Yes No Gel demolds once, sticks afterwards Perfluoro alkoy alkane 60 × 40 × 1.3 cm 1-10 No No Gel demolds 10 times, (PFA) mold sticks afterwards Methyl 2-fluoroacrylate 60 × 40 × 1.3 cm 1-10 No No Gel demolds 10 times, (MFA) mold sticks afterwards Steel mold with fluorinated 60 × 40 × 1.5 cm >150   Yes Yes Gel demolds more than polymer coating with 150 times conductive additive and anti-scratch additive (Rhenolease)

CITED LITERATURE

[0214] WO 00/24799