Patent Application
20200063335
Priority is claimed to German Patent Application No. DE 10 2018 120 713.1, filed on Aug. 24, 2018, the entire disclosure of which is hereby incorporated by reference herein.
The invention relates to a thermally-conductive material which simultaneously has effective sound absorption properties, and to its use.
Particularly in modern buildings, it is often desirable to air condition the rooms of the building by removing heat from or supplying heat to the building, even in moderate climate zones. Heat dissipation is important in particular for rooms that are much frequented by people and/or equipped with numerous electronic appliances, since these have a significant heat output within the triple-digit watt range. The same applies, for example, to production halls, where machines and installations emit considerable amounts of heat which must be removed from the building.
In principle, there are different possibilities for heat removal, wherein extensive air-conditioning elements based upon the heat radiation principle have proven to be particularly suitable. For air conditioning rooms—in particular, for room cooling—thermal conduction devices or air-conditioning elements known from the prior art are used. Such air-conditioning elements are also suitable, in principle, for room heating by reversing the direction of thermal conduction.
The prior art already discloses ceiling or wall elements that have a frame, which can be fastened to the ceiling or the wall, with a base plate and a heating or cooling register arranged in the frame. DE 20 2007 010 215 U1, for example, discloses a wall or ceiling covering with a heating or cooling register in the form of pipelines which are fastened to thermally-conductive profiles. The thermally-conductive profiles rest on the rear side of a covering surface formed by covering panels. The covering panels are fastened to support rails having a U-shaped cross-section. The support rails and the covering panels attached thereto thus form a frame which can be fastened to a ceiling or wall and has a base formed by the covering panels. The thermally-conductive profiles are arranged in the interior of this frame and adjoin the covering panels. The thermally-conductive profiles and the pipelines attached thereto form the heating or cooling register. In order to produce an effective thermal conduction contact between the pipelines and the covering surface, retainers are arranged transversely to the elongated, thermally-conductive profiles and hold at least two adjacent, thermally-conductive profiles against the covering panel under spring tension.
On their rear side, the thermally-conductive profiles have an approximately semicircular extension in which the pipelines are arranged. Depending upon the intended use as heating or cooling lines, a heating or cooling medium flows through the pipelines, such as, for example, fresh or cold water. The thermally-conductive profiles are generally made of metal—for example, aluminum. The covering panels can, for example, be gypsum board panels or perforated metal tiles made of steel or aluminum.
In order to enable a more efficient thermal conduction between the heating or cooling register and the space to be heated or cooled, DE 10 2009 055 440 A1 proposes a ceiling or wall element for fastening to a ceiling or a wall, wherein the ceiling or wall element has a frame, which can be fastened to the ceiling (or the wall), with a base in which a heating or cooling register is arranged, and wherein a fleece and a graphite film is arranged between the base of the frame and the heating or cooling register. The perforated graphite film is intended to ensure good thermal contact between the heating or cooling register and the bottom panel of the ceiling or wall element, and the fleece is intended to improve the sound absorption of the covering or wall element. In the case of the fleece, a carbon fiber fleece is shown as being preferred, since this has a high thermal conductivity. Preferably, the fleece and the perforated graphite film disposed thereon are a composite which can be produced by calendering.
A disadvantage of the thermally-conductive material described is that the thermal conduction in a vertical direction must be done via the carbon fiber fleece, since the graphite film only allows a planar heat conduction. Carbon fiber fleeces are, however, undesirable for health reasons in building applications and are unattractive in terms of price. Moreover, the use of a film has the disadvantage that it must be perforated in order to be sound-permeable and acoustically effective. As a result, films quickly tear and are brittle.
EP 2 468 974 A2 is also based upon the aim of achieving an improvement in the thermal conduction of heating or cooling elements. For this purpose, this publication proposes a construction for a heating or cooling element—in particular, for an air-conditioning ceiling—comprising a perforated, thermally-conductive carrier panel, on the rear side of which lines of a heating or cooling register run, which are in thermally-conductive contact with the carrier panel, wherein the rear side of the carrier panel and the heating or cooling lines are covered by a cover sheet which has a textile or lattice-like structure and consists of a thermally-conductive material or is coated with a thermally-conductive material.
A fleece consisting of graphite or coated with graphite can be used, for example, as the covering web. This fleece has no particular acoustic properties. Therefore, in order to improve acoustics, it is proposed to additionally laminate an acoustic nonwoven onto the rear side of the cover sheet.
EP 2 191 058 B1 describes a layer, for use in a metal ceiling, with a basis weight of at most 45 g/m2, comprising a fiber mixture, which is present in a proportion of at most 30 g/m2, and a flame retardant which is present in a proportion of at most 10 g/m2. The layer exhibits good acoustic properties, since it has a high and defined porosity. Owing to its high porosity, the layer is, however, only suitable to a limited extent for applications in which the thermal conduction is in the foreground.
In an embodiment, the present invention provides a thermally-conductive material, comprising: a textile fabric; and a graphite-containing, thermally-conductive coating, in which graphite is present in a proportion of 5 wt % to 50 wt % relative to a total weight of the thermally-conductive material, wherein the thermally-conductive material has a flow resistance of 60 Pa*s/m to 400 Pa*s/m.
In an embodiment, an aim of the invention is to provide a material which, with a simple design, combines very good thermal conduction properties with very good acoustic properties and can therefore be used for thermal conduction and sound absorption—for example, in the above-mentioned thermal conduction devices.
This aim is achieved by a thermally-conductive material with a flow resistance of 60 Pa*s/m to 400 Pa*s/m—more preferably, of 100 Pa*s/m to 300 Pa*s/m, and, even more preferably, of 120 Pa*s/m to 250 Pa*s/m—which has a textile fabric and a graphite-containing, thermally-conductive coating, wherein the graphite is present in a proportion of 5 wt % to 50 wt %, relative to the total weight of the thermally-conductive material.
Surprisingly, it has been found that, with the thermally-conductive material according to the invention, very good thermal conduction properties can be combined with very good acoustic properties. The thermally-conductive material can have a very simple and thin construction.
In a preferred embodiment, the proportion of graphite with respect to the thermally-conductive coating is more than 50 wt %, e.g., 50 to 100 wt %—preferably, 60 to 100 wt %, more preferably, 70 to 100 wt %, and, even more preferably, 80 to 100 wt %. This is advantageous, since the thermal conduction properties of the textile fabric can be significantly improved in this way. Accordingly, good thermal conductivity can thus also be realized with small application amounts. Small application amounts are in turn advantageous, since this influences the porosity and the air permeability of the textile fabric less.
In contrast, thermally-conductive coatings of textile fabrics known from the prior art usually have a smaller amount of graphite, since the graphite layer generally contains more than 50 wt % binder.
The advantage of using a thermally-conductive coating in comparison to films is that they can at least partially penetrate into the textile material. The advantage of penetrating the material is that the thermal conduction in the direction of the surface normals is improved. Accordingly, in a preferred embodiment, the thermally-conductive coating at least partially penetrates into the textile fabric.
An advantage of the thermally-conductive coating over perforated metal sheets is that improved adhesiveness can be achieved due to the faster and more uniform distribution of heat in the textile fabric that it makes possible.
In a preferred embodiment of the invention, adjusting the high proportion of graphite in the thermally-conductive coating is achieved by the textile fabric having fibers of a hydrophilic fibrous material. Without specifying a mechanism, it is assumed that the hydrophilic fiber material has a high affinity and, associated therewith, a particularly good adhesion to the graphite. This makes it possible to keep the proportion of binder very low in the thermally-conductive coating and/or between the thermally-conductive coating and the textile fabric.
Nevertheless, the thermally-conductive coating may contain binders. Exemplary binders are polymer binders from the group of acrylates, vinyl acrylates, vinyl acetates, ethylene vinyl acetates (EVA), acrylonitrile butadiene (NBR), styrene butadienes (SBR), acrylonitrile butadiene styrenes (ABS), vinyl chlorides, ethylene vinyl chlorides, polyvinyl alcohols, polyurethanes, starch derivatives, cellulose derivatives, and mixtures and/or copolymers thereof. In a preferred embodiment of the invention, the proportion of polymer binder, and in particular of the aforementioned polymer binders, in the thermally-conductive coating and/or between the thermally-conductive coating and the textile fabric is less than 50 wt %, e.g., 1 to 50 wt %—preferably, less than 40 wt %, e.g., 1 to 40 wt %, more preferably, less than 30 wt %, e.g., 1 to 30 wt %, and, in particular, less than 20 wt %, e.g., 1 to 20 wt %. The advantage of using only a slight proportion of polymer binder or entirely dispensing with it is an improved burning behavior of the material in case of a fire, and improved acoustic properties.
In a preferred embodiment of the invention, the proportion of graphite relative to the total weight of the thermally-conductive material is 10 wt % to 50 wt %—preferably, 10 wt % to 35 wt %, and, even more preferably, 10 wt % to 20 wt %.
In a further preferred embodiment of the invention, the thermally-conductive coating is present in the form of a pattern on the textile fabric. This means that regions of the surface of the textile fabric are covered with the thermally-conductive coating, and other areas are not. The thermally-conductive coating may also at least partially penetrate into the textile fabric. The advantage of forming a pattern is that the covered regions provide the thermally-conductive material with a high thermal conductivity, while the uncovered regions are particularly active acoustically, since their porosity is not reduced by being furnished with the thermally-conductive coating. The pattern may be a geometric or an irregular pattern. The degree of surface coverage of the thermally-conductive coating with respect to the surface of the thermally-conductive material is, advantageously, 1 to 95%, preferably 10 to 60%, and, particularly preferably, 30 to 50%. In a preferred embodiment, the pattern at least partially has continuous lines—preferably, with a line width >0.5 mm, preferably 2.0 to 10.0 mm, and, particularly preferably, 4.0 to 7.0 mm. A good thermal conductivity in the surface of the thermally-conductive material can be achieved by the penetrability.
In a further preferred embodiment, the pattern at least partially has discrete points, rods, and/or non-continuous areas—preferably, with a size of <100 mm2, more preferably, 1.0 to 50 mm2, and, in particular, 2.0 to 10 mm2. Practical tests have shown that this leads to rapid thermal conduction through the thickness of the material, i.e., perpendicular to the plane of the textile fabric.
The thermally-conductive material according to the invention is further distinguished by excellent acoustic properties. Thus, the thermally-conductive material has a flow resistance of 60 Pa*s/m to 400 Pa*s/m—more preferably, 100 Pa*s/m to 300 Pa*s/m, and, even more preferably, 120 Pa*s/m to 250 Pa*s/m. The flow resistance is measured in accordance with DIN EN 29053-A: 1993-05. The negative influence of the thermally-conductive coating on the acoustic properties of the material is reduced by reducing the proportion of the polymer binder or by entirely dispensing with it. Completely sealing the surface can thus be prevented, so that sufficient porosity is maintained for acoustic effectiveness. The flow resistance can be adjusted in a manner known to the person skilled in the art, e.g., by suitably selecting the fiber materials in coordination with the selected parameters in the production and coating of the textile fabric. It has been found that particularly good sound absorption is achievable with the selected flow resistances according to the invention. The degree of sound absorption α(0) of the thermally-conductive material according to the invention, measured in the impedance tube at 1,600 Hz, is preferably more than 0.55, e.g., 0.55 to 1.0, more preferably greater than 0.60, e.g., 0.6 to 1.0, and, in particular, more than 0.65, e.g., 0.65 to 1.0. The degree of sound absorption is determined in accordance with DIN EN ISO 10534-1: 2001-10 with the parameters given in Example 2.
According to the invention, the textile fabric preferably contains fibers selected from the group consisting of glass fibers, polyolefins, polyesters—in particular, polyethylene terephthalate, polybutylene terephthalate; polyamide—in particular, polyamide 6.6 (Nylon®), polyamide 6.0 (Perlon®), aramide, wool, cotton, silk, hemp, bamboo, kenaf, sisal, cellulose, soy, flax, glass, basalt, carbon, viscose and mixtures thereof. According to the invention, the fiber material particularly preferably contains glass fibers, cellulose and/or mixtures thereof—in particular, glass fibers and cellulose.
The textile fabric may also contain conductive fibers, such as metal fibers, ceramic fibers, carbon fibers, etc., to further improve thermal conductivity.
Cellulose fibers are particularly preferred according to the invention. Cellulose fibers are to be understood as fibers having cellulose, viscose, and/or fine-fiber or fibrillated cellulose components—so-called fiber pulp or cellulose. The fibers, particularly preferably, substantially consist of the aforementioned components, i.e., their proportion is more than 80 wt %.
In a preferred embodiment of the invention, the textile fabric contains a proportion of at least 30 wt %, e.g., 30 to 100 wt % and/or 30 to 95 wt %—preferably, 50 to 100 wt % and/or 50 to 90 wt %, more preferably, 60 to 95 wt %, and, in particular, 65 to 85 wt %—of cellulose fibers, relative in each case to the total amount of fibrous material in the textile fabric.
In a further preferred embodiment of the invention, the textile fabric contains glass fibers—preferably, in an amount of 5 to 80 wt %, more preferably, 5 to 70 wt %, more preferably, 10 to 60 wt %, in particular, 20 to 40 wt %—respectively relative to the total amount of fibrous material in the textile fabric. By adding glass fibers, the textile fabric can be provided with particularly high structural stability and low thermal shrinkage.
Most preferably, the textile fabric contains cellulose fibers—preferably, in a proportion of 30 to 95 wt %, more preferably 50 to 90 wt %, in particular, 65 to 85 wt %—and glass fibers—preferably, in a proportion of 5 to 70 wt %, more preferably, 10 to 50 wt %, in particular, 15 to 35 wt %—respectively relative to the total amount of fibrous material in the textile fabric.
The textile fabric could be in the form of fleece, nonwoven, or paper. A nonwoven, such as DIN EN ISO 9092, is preferably used according to the invention.
To produce the nonwoven, a nonwoven can be laid dry in a carding process, a wet-laid, nonwoven process, or in a spun-bonded, nonwoven process, in a manner known to the person skilled in the art. Preferably, the nonwoven is laid in a wet-laid, nonwoven process or carding process. A particularly high degree of uniformity can thereby be achieved, which is decisive for the acoustic properties. Accordingly, the nonwoven is preferably a wet-laid nonwoven or a carded nonwoven. The nonwoven is particularly preferably laid in a wet-laid, nonwoven process—in particular, with an oblique screen—since it is thereby possible to obtain nonwovens with particularly high uniformity.
The fiber mixture in the wet-laid, nonwoven process could also have fine fibrous or fibrillated cellulose components—so-called fiber pulp or cellulose. These components allow very effective harmonization of the acoustic effectiveness of the textile fabric. In a preferred embodiment, the nonwoven is thus a wet-laid nonwoven which contains fiber pulp—in particular, cellulose pulp—and/or cellulose—preferably, in a proportion of at least 30 wt %, e.g., 30 to 100 wt % and/or 30 to 95 wt %, preferably, 50 to 100 wt % and/or 50 to 90 wt %, more preferably, 60 to 95 wt %, and, in particular, 65 to 85 wt %—respectively relative to the total amount of fibrous material in the wet-laid nonwoven.
Against this background, it is conceivable that the wet-laid nonwoven contains two or more different types of fiber pulp and/or cellulose which differ in terms of their fineness. As a result, a particularly precise setting of the porosity is attainable and, associated therewith, a textile fabric with a particularly effective acoustic flow resistance. It is also conceivable for the wet-laid nonwoven to contain finely-ground, synthetic pulps—for example, of viscose, polyolefin, and/or aramide fibers.
The fleece can, in a known manner, be solidified mechanically, chemically, and/or thermally to form the nonwoven. Chemical bonding with the aid of a polymer binder is particularly preferred. Preferred fiber binders are polyacrylates, polyvinyl acrylates, polystyrene acrylates, polyvinyl acetates, polyethylene vinyl acetates (EVA), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), acrylonitrile butadiene styrene rubber (ABS), polyvinyl chlorides, polyvinyl ethylene vinyl chlorides, polyvinyl alcohols, polyurethanes, starch derivatives, cellulose derivatives, and copolymers and/or mixtures thereof. Accordingly, the nonwoven is preferably a chemically-bonded nonwoven. The fiber binder can be used to obtain the textile fabric with a high strength and good aging resistance. The application of the fiber binder can be carried out by impregnation, spraying, or by means of otherwise customary application methods.
The fiber binder can additionally contain customary additives such as a flame retardant, e.g., metal hydroxides such as aluminum hydroxide, diammonium hydrogen phosphate or other nitrogen and/or phosphorus-based flame retardants, such as ammonium polyphosphates or nitrogen-containing phosphoric acid salts. This can also be introduced into the impregnation mixture for fiber bonding via the fiber binder.
The proportion of fiber binder including the additives in the thermally-conductive material is preferably 10 to 70 wt %, more preferably, 20 to 50 wt %, and, in particular, 30 to 40 wt %, relative to the total weight of the thermally-conductive material.
The textile fabric can additionally contain anti-corrosive agents; this is because condensation moisture when using the cooling lid can in fact lead to damage of the metal elements, e.g., aluminum profiles, etc. The addition of an anti-corrosive agent can counteract this.
In addition, the textile fabric can be provided with an antimicrobial finish with the aid of a biocidal additive. In fact, condensation moisture during use can lead to bacteria and fungi growth in the textile fabric, which can be prevented by such finishing.
The basis weight of the thermally-conductive material is preferably 20 to 100 g/m2, more preferably, 40 to 70 g/m2, and, in particular, 45 to 60 g/m2, in each case measured according to ISO 9073-1. A material with low basis weights, i.e., a low use of material, is recommended for good fire behavior and good acoustic properties.
The thickness of the thermally-conductive material is preferably 0.1 to 0.5 mm, more preferably, 0.15 to 0.4 mm, and, in particular, 0.2 to 0.3 mm, measured in each case according to ISO 9073-2. An advantage of a thin material which at the same time has good acoustic properties is that the processing, i.e., lamination of the material in perforated metal covers, is facilitated.
The air permeability of the thermally-conductive material is preferably 100 to 3,000 L/m2/s, more preferably, 200 to 1,000 L/m2/s, and, in particular, 300 to 700 L/m2/s, measured in each case in accordance with DIN EN ISO 9237 at 100 Pa air pressure. These air permeabilities result in particularly good acoustic properties.
The tensile strength in at least one direction—preferably in the machine direction—of the thermally-conductive material is preferably 20 to 300 N/5 cm, more preferably 30 to 150 N/5 cm, and, in particular, 50 to 100 N/5 cm, measured in each case according to ISO 9073 to 3.
In a preferred embodiment of the invention, the textile fabric is metallized. The metallization can be effected, for example, by a vacuum deposition process or electrochemical deposition (electroplating). Aluminum, copper, copper alloys, stainless steel, gold, and/or silver have proven to be particularly suitable metals. Special preference is given to finishing with stainless steel, since this gives the textile fabric a particularly high aging resistance. In addition, finishing with a corrosion-inhibiting agent can take place.
According to the invention, the thermally-conductive material has a graphite-containing, thermally-conductive coating. In addition to graphite in the narrower sense, “graphite” is also to be understood according to the invention as graphite-analogous compounds such as, in particular, expanded graphite, graphene, and hexagonal boron nitride. In a preferred embodiment, the graphite is selected from graphite in the form of a material having several crystal planes and graphene, i.e., a material having only a single crystal plane. The graphite is preferably in particulate form. The average size of the graphite particles can preferably be 0.5 to 10 micrometers—particularly preferably, 1 to 3 micrometers. Practical tests have shown that this results in a good compromise between processability and thermal conductivity. Large graphite particles are advantageous for good thermal conduction, but are, however, more difficult to process, and preferably remain on the surface of the textile fabric. This leads to a low penetration depth of the graphite into the thermally-conductive material, which leads to a reduced conductivity perpendicular to the surface plane.
In one embodiment of the invention, the coating weight of the thermally-conductive coating is 1 to 50 g/m2—preferably, 2 to 30 g/m2, and, more preferably, 5 to 15 g/m2. Practical tests have shown that, even with a low graphite coating weight, a significant improvement in the thermal conductivity can be observed. At the same time, good acoustic properties can be achieved, since the porosity of the material is maintained.
The thermally-conductive coating is preferably applied by finishing the textile fabric with an aqueous graphite dispersion and then drying it.
A binder, e.g., a polymer binder, may be added to the graphite dispersion in order to improve the bonding of the textile fabric, e.g., polyacrylates, polyvinyl acrylates, polyvinyl acetates, polyethylene vinyl acetates (EVA), acrylonitrile butadiene (NBR), styrene butadienes (SBR), vinyl chlorides, ethylene vinyl chlorides, polyvinyl alcohols, polyurethanes, starch derivatives, cellulose derivatives, and mixtures and/or copolymers thereof.
Further additives may be added to the graphite dispersion, e.g., defoamers, wetting agents, surfactants which facilitate processing, bases and/or acids for adjusting the pH, flame retardants, corrosion inhibitors, and/or biocides. A wetting agent is preferably selected from the group consisting of: glycerin, propylene glycol, sorbitol, trihydroxystearine, phospholipids, ethylene oxide/fat alcohol ethers, ethoxylates of propylene oxide with propylene glycol, esters of sorbitol and/or of glycerol, alkylsulfonates, alkylsulfosuccinates and docusates and mixtures thereof.
Practical tests have shown that when a proportion of the wetting agent relative to the total amount of the graphite dispersion is in the range of 0.1 to 5 wt %—preferably 1 to 4 wt %, and, in particular, 1.5 to 3.5 wt %—a particularly uniform and homogeneous wetting and particularly good penetration into the material take place.
Furnishing can be carried out by all customary finishing methods for fabrics, e.g., by impregnation, e.g., by means of Foulard; by printing, e.g., flat or screen printing, rotary stencil printing; kiss coating, doctor blade, etc.; and spraying; the finishing can take place on one side or on both sides. Coating, e.g., printing—in particular, in screen printing or rotary stencil printing—is particularly preferred. The thermally-conductive coating can thus be applied, for example, as a pattern print to the textile fabric. The thermally-conductive material then has a high thermal conductivity locally in the printed region, while the unprinted regions are acoustically particularly active, since their porosity is not impaired by a finish with the thermally-conductive coating. The degree of surface coating of the thermally-conductive material by the thermally-conductive coating in the form of a pattern is preferably 1 to 100%, preferably 10 to 60%, and, particularly preferably, 30 to 50%. In a preferred embodiment, the printing is carried out at least partially in the form of continuous lines—preferably with a line width of >0.5 mm, preferably of 2.0 to 10.0 mm, and, particularly preferably, of 4.0 to 7.0 mm. This causes a rapid distribution of the heat in the plane of the textile fabric.
In a further preferred embodiment, the printing can take place at least partially in the form of discrete dots, rods, and/or non-continuous surfaces—preferably with a size of <100 mm2, particularly preferably of 1.0 to 50 mm2, and, in particular, of 2.0 to 10 mm2. Practical tests have shown that this leads to rapid thermal conduction through the thickness of the material, i.e., perpendicular to the plane of the textile fabric.
Drying can be carried out by all customary drying methods, e.g., contact drying with a roller drier; circulating air or through-air drying with a belt dryer; IR or microwave drying, etc. Through-air drying is preferred in order to maintain the porosity of the material and thus the good acoustic properties. The material can additionally be post-treated by compression rolling in order to further improve the contact of the graphite particles with one another and thus the thermal conductivity of the material.
In a preferred embodiment of the invention, the thermally-conductive material has an additional, preferably discontinuous, adhesive material coating. The adhesive material coating preferably consists of a hot-melt adhesive. The discontinuous nature of the adhesive material coating is advantageous in that it does not substantially impair the acoustic effectiveness of the thermally-conductive material. The adhesive coating can be applied, for example, by scattering a hot-melt adhesive powder onto the thermally-conductive material and then thermally fixing the powder to the thermally-conductive material. The hot-melt adhesive advantageously has a melting point of <125 C°.
The basis weight of the adhesive material coating is preferably 5 to 50 g/m2, more preferably 10 to 40 g/m2, and, especially preferably, 12 to 25 g/m2.
The adhesive material coating preferably substantially consists of a thermoplastic polymer, e.g., a largely amorphous polyester or copolyester, a polyamide or copolyamide, a polyurethane, a polyolefin, polyethylene vinyl acetate and/or mixtures, copolymers or terpolymers thereof. In this case, “substantially” is a proportion of at least 70 wt %—preferably more than 80 wt %—relative to the total mass of the adhesive material coating.
The adhesive material coating can additionally be furnished with thermally-conductive additives, e.g., by compounding the thermoplastic polymer with thermally-conductive fillers (for example, carbon black, graphite, metal powders, metal oxides, boron nitride, ceramic compounds, etc.) in order to further increase the thermal conductivity of the thermally-conductive material according to the invention.
If the adhesive material coating is applied to the textile fabric in the form of a powder, the powder can be processed as a mixture with other thermally-conductive powders (for example, metal powders, fine metal spheres, metal oxide powders, ceramic powders, etc.) in order to further increase the thermal conductivity of the thermally-conductive material. The adhesive material coating can also contain a ceramic reactive adhesive which has, for example, reactive silane groups.
The thermally-conductive material according to the invention is outstandingly suitable for thermal conduction and simultaneous sound absorption in ceiling and/or wall elements—in particular, comprising a frame which can be fastened to the ceiling and/or the wall and has a base in which a heating and/or cooling element is arranged. The thermally-conductive material according to the invention is preferably arranged between the base of the frame and the heating or cooling element.
The ceiling and/or wall elements may be used in suspended, perforated, and/or slotted metal ceiling and/or wall systems (inter alia, also in wood or gypsum board ceilings). It is also conceivable to use the thermally-conductive material according to the invention in the construction of raised floors.
The invention is explained in more detail below with reference to several examples.
For the production of a thermally-conductive material according to the invention, first, a textile fabric is produced in the form of a wet-laid nonwoven. The overall basis weight of the wet-laid nonwoven is 48 g/m2. In this case, the textile fabric has a fiber mixture of 70 wt % cellulose and 30 wt % glass fibers. The fiber mixture contributes a total of 25 g/m2 to the basis weight of the textile fabric. The textile fabric further has a fiber binder consisting of polyacrylate binder and flame retardant that contributes 23 g/m2 to the basis weight.
A commercially available graphite dispersion having an average particle diameter of 2.5 micrometers and a solids content of 18 wt % is used to produce the thermally-conductive coating. Application takes place by means of rotary stencil printing and drying in a flow-through oven. A rectangular diamond pattern is selected as a template pattern. The average width of the printed lines on the wet-laid nonwoven is 5.0 mm, and the surface coverage by the thermally-conductive coating is 52%. The proportion of graphite in the thermally-conductive coating, measured according to Example 4, is 80 wt %, which corresponds to a proportion of 14 wt %, relative to the total weight of the thermally-conductive material.
The resulting thermally-conductive material has a total weight of 57 g/m2, a thickness of 0.23 mm, a tensile strength in the machine direction of 65 N/5 cm, an air permeability at 100 Pa of 550 L/m2/s, and a flow resistance of 190 Pa*s/m.
The thermally-conductive material was furnished with an adhesive material coating for tests in the impedance tube. The adhesive material consists of epsilon polycaprolactone, which is powdered onto the thermally-conductive material as ground powder having an average grain size of 150 micrometers and sintered in the furnace. The applied amount is 15 g/m2 in this case.
The thermally-conductive material furnished with the adhesive material coating is then ironed onto a perforated, painted steel sheet with a thickness of 0.5 mm, a proportion of perforated surface of 15%, and a perforation diameter of 2.3 mm. The degree of sound absorption on the composite material is determined, and α(0) specified at a frequency of 1,600 Hz.
At 1,600 Hz, a degree of sound absorption of α(0)=0.7 is determined.
The thermal conductivity of the thermally-conductive material was investigated in comparison with the textile fabric without a thermally-conductive coating. The measurements were carried out by the plate method in accordance with DIN 52612 on 6 stacked test specimens, and according to the hot disk method with a single layer pursuant to ISO 22007-2.2:2008, Part 2.
A qualitative identification of the graphite was performed by means of x-ray diffraction (XRD) pursuant to DIN EN 13925-2 2003-07. For this purpose, X-ray diffractograms of the thermally-conductive material were recorded with CoKα radiation at 40 kV and 35 mA within an angular range of 5° to 60° (2 theta). A unique identification can be made by the sharp reflections at 30.78° (3.37 Å); 49.69° (2.13 Å); 52.19° (2.04 Å); 64.37° (1.68 Å); 93.21° (1.23 Å). A quantitative determination of the proportion of graphite in the thermally-conductive material or the thermally-conductive coating can be carried out by means of thermogravimetric analysis (TGA) according to DIN EN ISO 11358 2014-10. The sample is first heated in an inert nitrogen atmosphere to 1,000° C. and cooled back down to 300° C. This is followed by heating the sample again to 1,000° C. under oxygen. In this last combustion stage, the graphite and (if available) the carbon black are burned. In this case, carbon black burns within a temperature range of 380° C. to 700° C., and graphite burns at temperatures greater than 700° C. If the combustion of the carbon black is not completely separated from that of the graphite, the derivation of the thermogravimetry curve, which then shows a reversal point at 700° C., is used to determine the temperature ranges to be evaluated.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments.
The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102018120713.1 | Aug 2018 | DE | national |
