Microporous thermal insulation body

Abstract

The present invention relates to a thermal insulation body comprising a plate-shaped thermal insulation layer made of a microporous material, which is integrally connected on at least both main sides to a needle-punched nonwoven made of glass or ceramic fibers.

Description

[0001] The present invention relates to a microporous thermal insulation body with a low thermal conductivity.

[0002] Thermal insulation bodies can be found in many areas of technology, for example, as high-performance thermal insulation bodies in the aerospace industry, the automotive industry, fuel cells, temperature-controlled packaging, and the general and construction industries. They are used wherever low weight, compact dimensions, and high-performance thermal insulation with very steep temperature gradients are required.

[0003] Such thermal insulation bodies can easily withstand temperatures up to 1,100°C and are therefore suitable for use as back-up insulation in the steel, aluminum, and glass industries. The (high-performance) thermal insulation molded bodies can be quite complexly shaped to provide efficient thermal insulation in the tightest spaces and under the most challenging conditions. Such thermal insulation layers are pressed at pressures of 5 to 20 bar, resulting in thicknesses between 2 mm and 35 mm. Typically, the thermal insulation layers are formed in strip or plate form, but they can also be pre-pressed and bent, for example, to enclose pipelines and other spatially curved bodies.

[0004] Such thermal insulation bodies can also be designed as vacuum insulation panels (VIPs), which have particularly good insulating properties, down to thermal conductivity values ​​of 5 mW / (mK) and below. However, these VIPs are not the subject of the invention.

[0005] Thermal insulation bodies have a thermal insulation layer containing an insulating material, such as highly dispersed, microporous silica. In addition to these insulating materials, other additives are commonly used in the various thermal insulation bodies, particularly IR opacifiers, moisture scavengers, and fiber filaments to support the three-dimensional structure when using highly dispersed silica. Opacifiers include silicon carbide, rutile, ilmenite, and zirconium silicate. Viscose and cellulose are used as fiber filaments, as are textile glass fibers and ceramic fibers.

[0006] With the exception of VIPs, such thermal insulation layers are relatively easy to process with commercially available tools and machines, particularly drilling, sawing, milling, or cutting. Due to the dustiness of the thermal insulation material, fumed silica, dust extraction is essential. This strong tendency to generate dust is due not least to the fact that the frequently used fumed silica has primary particle sizes of 5 to 50 nm, thus behaving almost gasfully and being respirable. Even the aggregated silica particles still have sizes of 100 nm to 100 µm. The surfaces of thermal insulation layers made of fumed silica are considered rather sensitive due to their chemical and physical properties. The same applies to thermal insulation layers made of the other materials mentioned above.

[0007] It has therefore long been an aim to protect the surfaces of thermal insulation layers and thermal insulation moldings containing these thermal insulation layers from abrasion and mechanical damage, in particular from the ingress of water, which destroys the pore structure.

[0008] It is known from the prior art to pour fiber-infused bitumen as a casting agent over microporous thermal insulation layers. However, bitumen is highly viscous and therefore difficult to handle. Furthermore, bitumen penetrates very deeply into the thermal insulation material, particularly by more than one millimeter, which leads to significantly impaired insulating properties.

[0009] From DE 20 2007 013 688 U1 it is known to provide thermal insulation bodies with a covering made of a pressed, rolled, extruded foam or fiber material, in particular with a covering made of plastics or of GRP based on polyester resins or PA, where appropriate adhesives based on water glass, silica sols or similar are used.

[0010] From EP 0 829 346 A2 a thermal insulation body is known in which the pressed thermal insulation layer consists of a highly dispersed silica aerogel, which is located between a co-pressed upper and lower layer of ceramic fiber material such as ceramic paper, nonwoven, felt, cardboard, wherein this pressed multi-layer thermal insulation layer is accommodated in a shrinkable plastic film.

[0011] DE 20 2022 002 799 U1 discloses a multi-layer thermal insulation body made of a microporous material. DE 10 2012 105 425 A1 discloses a molded part made of sheet-like fiber structures and binding agents as an acoustically effective molded part. Finally, DE 199 41 746 A1 discloses an insulating molded body in which microporous material is surrounded by a film-like covering.

[0012] The disadvantage of these known thermal insulation bodies is that they are complex to produce and difficult to form after production.

[0013] It is therefore an object of the invention to provide a formable thermal insulation body with a low thermal conductivity.

[0014] This object is achieved by a thermal insulation body according to claim 1. Surprisingly, it has been shown that a material-to-material bond with at least one needle-punched nonwoven layer results in the previously pressed thermal insulation layer being formable after bonding with the needle-punched nonwoven layer without breaking. This advantage is particularly evident when the thermal insulation layer is provided with a needle-punched nonwoven layer on both of its main sides in the manner of a sandwich bond.

[0015] According to the invention, a material bond is provided between the needle-punched nonwoven layer and the thermal insulation layer, so that an adhesion promoter layer, in particular an adhesive layer, is required. The needle-punched nonwoven layer therefore does not adhere due to purely physical interactions; therefore, it cannot be attached in situ to the thermal insulation molded body according to the invention at its place of use. The invention provides the following adhesion promoters, individually or in combination: water glass, a two-component coating consisting of a phyllosilicate and an inorganic binder, and a colloidal silica such as silica sol. These adhesion promoters or adhesives are preferably rolled or sprayed onto the pressed thermal insulation layer before the needle-punched nonwoven layer is applied.

[0016] According to the invention, the needle-punched nonwoven layer comprises silicate glass fibers, in particular mechanically needle-punched silicate glass fibers without the addition of binders, with a filament diameter of > 6 µm and / or a ceramic fiber made of aluminum oxide or silicon carbide. These fibers are resistant to both temperature and thermal shock and form an intimate bond with the highly dispersed material of the insulating layer. According to the invention, the needle-punched nonwoven layer has a thickness of 2 to 8 mm.

[0017] According to the invention, the thermal insulation layer has a thickness of 2-10 mm, or in a further development of the invention, between 3-5 millimeters. These thicknesses ensure adequate thermal insulation while maintaining good formability.

[0018] According to the invention, the thermal insulation layer comprises a highly dispersed, microporous thermal insulation material, selected individually or as a mixture from the group consisting of: fumed silica, precipitated silica, and arc-cured silica. Fumed silica is preferred. However, this is particularly difficult to coat, since a top layer material with too low a viscosity destroys the structure of the silica by penetrating too deeply, and a more viscous top layer material is difficult to apply.

[0019] In a further development of the invention, it is provided that the needle felt layers form the thermal insulation layer

[0020] Finally, in one embodiment of the invention, the needle-punched nonwoven layer has a thickness of 3 to 5 mm, most preferably 3 mm. These thicknesses represent a compromise between formability and mechanical protection of the thermal insulation layer. Examples of implementation:

[0021] In all examples shown in the table below, a pressed, plate-shaped microporous thermal insulation layer was used. The thickness of the thermal insulation layer, the type, thickness, and coverage of the nonwoven mat, as well as the type and application method of the adhesion promoter were varied.

[0022] The first column indicates the thickness of the thermal insulation layer in mm. In the second column, fleece type 1 stands for a needle-punched fleece made of silicate glass fibers without the addition of binders and with a filament diameter of > 6 µm, and fleece type 2 stands for a needle-punched fleece made of ceramic fibers of aluminum oxide and silicon carbide. The number after the hyphen indicates whether one or two main sides of the thermal insulation layer have been coated with a fleece layer. The adhesion promoter types are: A: water glass, B: a two-component coating made of layered silicate and an inorganic binder, and C: colloidal silica sol. All of these adhesion promoters ultimately lead to the formation of silicification and thus to water-insoluble silica. The bending radius indicates the minimum bending radius that can be achieved at which the thermal insulation layer remains compact, i.e., does not crumble or tear.The “+” in the last column of Table 1 means a surface treatment of the thermal insulation layer as described below.

[0023] Embodiments not according to the invention are marked with an *. Table 1; Layers [mm] Nonwoven type - nonwoven layers Adhesion promoter Bending radius [mm] 1 3 1-1 C 10 * 2 3 1-2 A 10 3 3 2-1 B 12 * 4 5 1-1 C 15 + * 5 5 1-2 A 15 + 6 5 2-1 B 18 + * 7 10 1-2 C 100 +

[0024] Each exemplary embodiment was carried out using two different methods of applying the adhesion promoter. One application was by roller, the other by linear application. No differences were observed in the achieved bending radii and the strength of the bond between the thermal insulation layer and the fleece layer. Pressing the thermal insulation layer and fleece layer did not result in a significantly improved bond, so that such pressing can advantageously be omitted, which simplifies the manufacturing process of the thermal insulation bodies according to the invention. The surface treatment was carried out by creating grooves with a groove depth of approximately 50% of the material thickness of the thermal insulation layer, in particular a plurality of equidistant parallel grooves.

[0025] Even with only one main side covered, the thermal insulation layer could be bent with the mentioned minimal radii without crumbling. This is possibly due to the fact that multiple wrappings of the object to be insulated also result in a sequence of (fleece-thermal insulation layer-) n and thus provides sufficient mechanical protection for the thermal insulation layer.

[0026] With great advantage, the partial wrapping of the thermal insulation layer with the aforementioned fleeces also allows the thermal insulation body to be inserted into narrower installation spaces, as the fleeces can be compressed, which even creates a certain holding force.

[0027] A great advantage is that even vibrations, such as those expected in the thermal insulation of automotive components, do not lead to damage to the thermal insulation layer, even after long periods of operation, because the surrounding fleece layers also dampen vibrations. This is especially true when fleece mats with greater thicknesses of 6 mm or 10 mm are used. The best results were achieved with a thermal insulation body with a 3 mm thermal insulation layer and two Type A fleece layers, each 4 mm thick.

[0028] Tests with a complete envelopment of the thermal insulation layer did not result in any deviations in the bending radii. Complete envelopment is achieved by using larger nonwoven layers, so that their edges extend beyond the thermal insulation layer and are directly bonded to each other using the same bonding agent.

Claims

[1] Thermal insulation body, comprising a pressed, plate-shaped thermal insulation layer made of a microporous material, individually or as a mixture selected from the group formed by: pyrogenic silica, precipitated silica, arc silica, characterized bythat it is formed in the manner of a sandwich connection on both its main sides with a needle-punched nonwoven made of glass or ceramic fibers, wherein an adhesion promoter layer is provided which is selected individually or in combination from water glass, a two-component coating made of a layered silicate and an inorganic binder as well as a colloidal silica, and wherein the thermal insulation body only has the layers mentioned, and wherein the needle-punched nonwoven layer has silicate glass fiber with a filament diameter of > 6 µm and / or a ceramic fiber made of aluminum oxide or silicon carbide, and wherein the thermal insulation layer has a thickness of 2-10 mm, and wherein the thermal insulation layer has an area of material weakening in the form of grooves with a groove depth of around 50% of the material thickness of the thermal insulation layer, and wherein the needle-punched nonwoven layer has a thickness of 2 to 8 mm. [2] Thermal insulation body according to claim 1, characterized bythat the thermal insulation layer has a thickness of 3-5 mm, most preferably 3 mm. [3] Thermal insulation body according to claim 1 or 2, characterized by that the needle-punched nonwoven layer has a thickness of 3 to 5 mm, particularly preferably 4 mm.