JPH0346304B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composite board for low-temperature insulation suitable for insulation of low-temperature tanks or tankers such as LNG or LPG. The purpose is to prevent cracks from occurring and the gap between joints to maintain dimensions even at extremely low temperatures.
We propose a low-temperature, heat-insulating composite board that has high shape stability and can be attached to curved surfaces. Conventionally, a composite board made by laminating plywood or the like on a rigid polyurethane foam has been used as a low-temperature heat insulating material. However, at extremely low temperatures below -100°C, the foam shrinks and cracks occur along the grain of the plywood, which causes cracks in the internal foam, resulting in a reduction in insulation. In addition, in order to prevent this drawback, a proposal was made to interpose a fiber layer between the foam and the plywood to prevent cracks in the plywood (1983-
110925) is also available. However, even with this method, the absorption of shrinkage stress within the foam is insufficient and the occurrence of cracks within the foam cannot be completely prevented. Moreover, it is difficult to form a curved surface of a composite board made by laminating plywood, and it has the disadvantage that it is not possible to form a heat-insulating surface in a spherical or cylindrical shape. This invention was made with attention to the above-mentioned problems, and its gist is that a synthetic resin layer reinforced with plywood, glass fiber, or synthetic fiber is laminated and integrated on at least one surface of a hard synthetic resin foam. The foam has a density of 35 to 100 Kg/m ³ ,
When the thickness direction is the Y axis, and the width and length directions are the X and Z axes, the water vapor permeability in the Y axis direction Py≦1.5 [g/m ²
hr], the elongation at break in the X-axis and Y-axis directions Ex and Ey are 60
This is a composite board for low temperature insulation using a foam layer with ≧Ex≧8 and 60≧Ey≧8 (%). This composite board uses a hard synthetic resin foam as a heat insulating layer, but it also has a high elongation foam layer with an elongation of 8 to 60% in the width and length directions. The shrinkage stress is absorbed and relaxed within the high elongation foam layer and no cracks occur, and the shrinkage is reduced by being constrained by the shrinkage ability of the laminated plywood or the synthetic resin layer reinforced with glass fiber or synthetic fiber. Since it approaches the coefficient of linear expansion of the heat insulating material, it is difficult for joints to open when it is laid, and a heat insulating layer without defects can be formed. If a reactive synthetic resin (for example, a two-component urethane adhesive) is applied to the foam as a synthetic resin layer and formed and cured by pressing or sandwiching, it can be applied to curved surfaces such as cylindrical and spherical shapes. It can be molded, and in addition to the rigidity of the hardened synthetic resin layer, it also has excellent shape retention, making it easy and reliable to insulate curved surfaces. At the same time, it is lightweight, has high compressive strength, is easy to install, has high creep resistance, and can withstand high loads over long periods of time, making it particularly suitable for forming heat insulating layers over large areas such as the bottoms and side walls of LNG tanks. This composite plate will be explained below using the drawings. In FIG. 1, a layer 2 (hereinafter referred to as surface material) made of a synthetic resin layer reinforced with plywood, glass fiber, or synthetic fiber is formed on one surface of a hard synthetic resin foam 1 (hereinafter simply referred to as foam) made of polystyrene. ) are laminated and integrated via an adhesive 3 to form a composite board for low-temperature insulation 4 (hereinafter simply referred to as composite board).
is configured. In FIG. 2, a composite plate 4 is constructed by laminating and integrating surface materials 2, 2 on both surfaces of a foam 1 via adhesives 3, 3. The foam 1 constituting these two composite plates 4 has a density of 35 to 100 kg/m ³ , and when the thickness direction is the Y-axis direction, the elongation at break in the X and Z-axis directions perpendicular to this is
Ex and Ey are each in the range of 8% to 60%,
Water vapor transmission rate in the Y-axis direction Py≦1.5 [g/m ²・hr],
Must be. If the density is less than 35 Kg/m ³ , sufficient compression resistance, creep resistance, heat insulation and moisture permeability cannot be imparted for low-temperature insulation. Rigidity is higher than 100Kg/ ^m3 , Ex, Ez
It becomes difficult to make it 8% or more. From the viewpoint of compression resistance, the density is more preferably 40 Kg/m ³ or more. Water vapor transmission rate Py is 1.5 or less. If maintaining long-term insulation performance is important, it is more suitable for Py to be 1.0 or less. The elongation rates Ex and Ez are 8 to 60%.
If it is less than 8%, the absorption and relaxation of shrinkage force at low temperatures will be insufficient, and if it is more than 60%, the water vapor permeability and mechanical performance of the foam will be significantly reduced, which is not preferable. Usually 40
The object of this invention can be achieved if the elongation rate is less than %. As the surface material, plywood with a thickness of 5 to 20 mm, synthetic resin (0.3 to 2 mm) reinforced with a net made of glass fiber or synthetic fiber, etc. can be used, and is selected depending on the purpose. Polyurethane-based adhesives with excellent adhesive strength and low-temperature properties are used as adhesives for foam and plywood.
Epoxy or the like is used, and the synthetic resin layer is preferably one that has adhesive strength with the above-mentioned foams. This composite plate has the above-mentioned structure, and the composite plate 4 shown in FIG. 1 is attached to a low-temperature object to insulate the foam 1.
Alternatively, the composite board 4 shown in FIG. 2 is heat-insulated by attaching the surface material 2 on one side to a low-temperature object. The composite board has
A temperature gradient occurs where the cold object side is cold and the opposite side is the outside temperature. Therefore, a shrinkage difference occurs between the low-temperature side and the high-temperature side, and strain stress acts on one layer of the foam, but this strain stress is absorbed and relaxed by Ex and Ez, thereby preventing the occurrence of cracks in the foam. At the same time, interfacial peeling with the surface material does not occur. If a fiber-reinforced resin or the like is used for the surface material 2 of this composite board, the composite board of FIGS. As shown in Figures 3 and 4, it can form a curved surface with an arcuate cross section, and can form an insulating surface for cylindrical tanks, etc.
As shown in FIG. 5, it is possible to form a curved surface in the shape of a spherical shell and a heat insulating surface for a spherical tank, etc. FIG. 6 shows an embodiment in which a reinforcing surface material 2 is provided on one side, and multiple layers (foam layers 1a and 1b) are used when the insulation performance is insufficient with a single foam layer as shown in FIG. It is something that Depending on the temperature of the object to be insulated, the performance of the insulation material, and the required insulation conditions, a thick insulation layer can be formed by laminating and integrating the foam layers with an adhesive. The adhesive is preferably a urethane-based or epoxy-based adhesive that has excellent low-temperature properties. If necessary, a mesh such as glass fiber may be inserted between each foam layer to reinforce the adhesive layer. The term "hard synthetic resin foam" as used in the present invention refers to a foam made of a hard synthetic resin such as polystyrene, methyl methacrylate, vinyl chloride, or the like. In particular, when compressive strength and long-term compression creep resistance are required of the foam itself, it is more beneficial to use a foam made by using a styrene resin and foaming it by a known extrusion foaming method. Polystyrene, which constitutes extruded polyethylene foam, is a resin whose main component is styrene.
Instead of styrene, other styrenic monomers such as a-methylstyrene, vinyltoluene, and chlorostyrene may be used. Also included are copolymers obtained by copolymerizing monomers copolymerizable with the above styrene monomers, such as acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, maleic anhydride, acrylamide, vinylpyridine, acrylic acid, and methacrylic acid. . Furthermore, the above-mentioned styrene-based polymer may be blended with other polymers to the extent that its properties are not impaired. Extruded polystyrene foam, whose main component is styrene, is rich in closed cells and has excellent heat insulation, moisture permeation resistance, compressive strength, long-term compression creep resistance, and low water vapor permeability, but generally has a break elongation of 5. % or less, and in order to be used in the composite plate of the present invention, it is necessary to give it an elongation of 8 to 60% in the Ex and Ez directions, so that it can absorb thermal stress at extremely low temperatures and has a cylindrical shape or It is difficult to mold into a spherical shape. The heat insulating board for a composite board of the present invention can be achieved by compressing in the X axis (length direction) and Z axis (width direction) as described below. As shown in FIG. 7, a drive speed difference is provided between the two pairs of upper and lower clamping drive levels 6, 7 and 8, 9, and the foam 10 is fed between them, and the speed difference allows the transport direction to be adjusted, e.g. Perform compression processing in the X-axis direction. Depending on the drive speed difference and the number of processing operations, elongation of 8 to 60% can be imparted. Similarly, the foam is compressed in the Z-axis direction to obtain a foam with high elongation. This elongation makes it possible to absorb thermal strain generated in the foam layer at low temperatures and to press-form it into a cylindrical or spherical shape that conforms to the shape of the body to be insulated. Processing means for using this composite plate (FIGS. 1 and 2) as a cylindrical or spherical composite plate will be described below. As the surface material, a reactive synthetic resin with excellent adhesion to the foam and excellent mechanical properties at low temperatures is selected, reinforced with glass fiber mesh. A two-component urethane adhesive is applied to the entire surface of the foam (example of conditions: polystyrene type) that has been pressed using the device shown in Figure 7. Next, a reinforcing layer is placed, and the same adhesive is applied over it. and fill in the above reinforcing layer,
With this reinforcing adhesive layer in an uncured state, the composite board is pressed or clamped onto the surface of a cylindrical or spherical mold with a curvature similar to that of the object to be insulated to a temperature of 60 to 90°C, preferably 70 to 80°C. After curing the synthetic resin under heated conditions, it is cooled and removed from the mold. Depending on the curing conditions of the synthetic resin layer, this can be performed cold to form a curved surface. But 60～
Heating to 90°C is more preferable because the curing time is shorter and the bending strain of the foam is completely relaxed. The measurement method and evaluation of each characteristic referred to in the present invention were performed as follows. (1) Density; [Kg/m ³ ] Take a 5 cm x 5 cm x 5 cm cube from the foam, calculate it from the weight [g] and volume (cm ³ ), and calculate the average value of the 5 pieces as the density (Kg/m 3 ). ³ ). (2) Compressive strength; [Kg/m ³ ] The compressive strength was measured based on ASTM D1621 in the thickness direction (Y-axis direction) of the 5 cm x 5 cm x 5 cm test piece whose density was measured, and the average value of 5 pieces was calculated. represent. The compression strain rate is 5%. However, if a yield phenomenon occurs within 5%, the yield value is taken as the compressive strength and evaluated based on the following criteria.

[Table] (3) Elongation at break [%] Amount of strain (amount of elongation) when a test piece is pulled in the specified directions (X and Z) and broken based on the tensile strength measurement method, ASTM D 1623 B method. Measure [mm] and calculate and evaluate using the following formula. A total of 5 test pieces were taken from each direction. Test piece; 50mm x 50mm x 50mm Elongation at break (Ex or Ez) = Elongation at break [mm] / Thickness of test piece [mm] x 100 [%] (4) Water vapor transmission rate; WVTR [g/ m ²・hr〕 Take 3 test pieces of 25mm x 80φ and ASTM
Measure according to C 355. At 25mm thickness
WVTR is calculated using the following formula. However, the method is to use distilled water. WVTR [g/m ²・hr] = G / A ・t G: Weight change [g] t: Time span during which G occurred (hr) A: Transmission area (m ² ) (5) Thermal conductivity over time Rate of Change A test piece with a thickness of 25 mm, a width of 200 mm, and a length of 200 mm is taken from the top of the pressed product as shown in Figure 8, and measured using the apparatus shown in Figure 9. Water 14 at 27° C. is poured into a container 11 equipped with a temperature controller 13 surrounded by a heat insulating material 12, and the opening side of the container is covered with the gasket 1 using the sample piece 15.
occlude via 6. At this time, the sample piece is placed so that there is a distance of about 30 mm between the bottom surface of the sample and the water surface in the container. Further, the upper surface of the test piece 15 is in close contact with a cooling plate 19 that is cooled to 2° C. by cooling water circulated from circulation water ports 17 and 18. After being left in this condition for 14 days, the surface of the sample piece was wiped lightly with gauze, and the thermal conductivity λ' of this sample was measured in accordance with ASTM C 518, and was previously measured under the same conditions before the test. Rate of change from thermal conductivity λ λ′/λ
Calculate and evaluate according to the table below.

[Table] (6) Panel cryogenic resistance A test plate of 50 mm x 300 mm x 300 mm was taken, and after cutting the top and bottom surfaces, the top and bottom surfaces of the test foam 21 with the X-axis and Z-axis directions clearly marked as shown in Figure 10. 12mm×
300mm x 300mm plywood (JAS standard product) 23, 24
Polyurethane-based two-component cryogenic adhesive (manufactured by Sumitomo Bakelite Co., Ltd.: Sumitaku EA90177) 22
The test panel 20 was prepared and three test panels were prepared and tested by adhering and aging and curing under a pressure of 0.5 Kg/cm ³ for 24 hours at 23°C. (1) Cryogenic temperature: -160℃ test As shown in Figure 11, the above test panel 2
0 is suddenly placed in a cryogenic chamber 25 whose internal temperature is controlled to -160°C±5°C, and after being left for 5 hours, it is quickly taken out to room temperature and left to stand for 1 hour. This operation is repeated 4 times, and the cryogenic chamber 25 is heated for the fourth time.
Immediately after taking out the test panel 20 from the test foam board 21, the four sides of the test foam board 21 are observed to confirm the presence or absence of cracks and the direction in which they occur. Plywood 2 after 1 hour
3, 24. Slice with a single-tooth slicer along the boundary surface of the test foam board 21, and further divide the sample into 5 slices with a thickness of about 10 mm toward the inside of the test foam board 21, and divide each slice into 5 slices. Water mixed with a surfactant and coloring ink is applied to the surface of the sample, and the presence or absence and direction of cracks on the sample surface are investigated and recorded. The temperature inside the cryogenic chamber 25 is controlled by connecting the liquid nitrogen cylinder 26 to the liquid nitrogen pipe 2.
7 to the jet nozzle 29 at the top of the tank, where it is vaporized while contacting the perforated barrier plate 30, and the gas exits from the outlet 32 to lower the temperature inside the tank. The flow rate of liquid nitrogen is adjusted by opening and closing an automatic flow rate control valve 28 by a control device in which a thermometer 31 in the tank and a timer are linked. (2) Cryogenic temperature: -196°C test As shown in FIG. 12, the test panel 20 described above is tested in a liquid nitrogen immersion device 34 sealed with a heat insulating material 33. After introducing liquid nitrogen 36 directly from the liquid nitrogen cylinder into the stainless steel deep-bottom tray 35 via the liquid nitrogen piping 27 and liquid nitrogen introduction valve 37, the test panel 20 is rapidly and sufficiently immersed in the liquid nitrogen 36. After placing the iron weight 38, which has been cooled in liquid nitrogen in advance, on the iron support 39 and immersing it continuously for 30 minutes, the test panel 20 is taken out into the atmosphere and left for 1 hour while being ventilated. . This operation was repeated four times, and the existence and direction of cracks on the outer and inner surfaces of the foam were investigated and recorded using the same equipment and method as used in the cryogenic -160°C test. Each test temperature condition will be evaluated according to the following criteria based on the results of the investigation records of the three test panels.

【table】

[Table] (7) Cleave resistance Take 8 test pieces of 50 mm x 50 mm x 50 mm from the test foam. Five pieces were selected from among them, and the compressive strength in the thickness direction (Y axis) was measured according to ASTM D 1621, and the average compressive strength (Kg/cm ³ ) was determined, and this was set as σ _c . The remaining three specimens were used as test specimens 45 for cleave measurement, and as shown in FIG. 13, plywood boards 41 and 42 with a thickness of 5 mm were bonded and cured by pressure on the upper and lower surfaces in the thickness direction via adhesives 43 and 44. is defined as the creep measurement composite 40. The thickness of the test piece 45 for creep measurement in the thickness direction (Y axis) is accurately measured to the nearest 1/100 mm, and this dimension is defined as T ₀ . As shown in FIG. 14, the cleave measurement complex 40 is gently set between the weight mount 48 of the creep measurement device 46 and the device mount 50, and then a value of 1/3 of the average compressive strength σc determined above is set. Weight W _{2 (W 2 =} 25 x
σc/3−W ₁ ) is loaded gently to avoid shock. Immediately after loading, the scale of the dial gauge 47 is set to zero. After 1000 hours at 23°C, read the scale _T1 of the dial gauge 47, that is, the creep amount (mm) for 1000 hours, in units of 1/100 mm, calculate the creep amount (%) according to the following formula, and calculate the creep amount (%) according to the following criteria. Evaluate creep resistance. Creep amount (%) = T ₁ / T ₀ ×100

[Table] Example, Comparative Example 1 Figure 7 shows an extruded polystyrene foam board (manufactured by Asahi Dow Co., Ltd.; Styrofoam) and a polyvinyl chloride foam board with a density of 35 to 100 Kg/m ³ and a thickness of 100 mm. First, press X using a pressing device according to the manufacturing method described in the text.
Axial direction (length direction), then Z-axis direction (width direction)
Press-processed. At this time, among the pressing conditions shown in Table 3, only the compression ratio and the number of times of pressing were selected as appropriate, and the other conditions were the same, to create a foam board with high elongation. (Experiment Nos. 1 to 14) For comparison, extruded polystyrene foam boards with densities of 28 to 100 kg/m ³ (manufactured by Asahi Dow Co., Ltd.; Styrofoam, unprocessed polyvinyl chloride foam boards, and Those processed only in the axial direction and those processed in both the X and Z axes were also created.For each foam, the density, elongation at break in the X-axis and Z-axis directions, and water vapor permeability in the Y-axis direction were determined using the method described in the text. Focusing on changes in thermal conductivity over time and cryogenic resistance (-160°C), evaluations were made using the methods and criteria described in the text, and the results of each and the comprehensive evaluation are shown in Table 1.Overall The evaluation criteria were as follows: ◎; All characteristics marked with ○ (satisfied with the highest standards) ○: △ but with many ○ marks (satisfied with the purpose of the present invention) ×; Items with at least one x mark (items that do not achieve the purpose) According to the results in Table 1, low-temperature insulation foams for LNG tanks, etc. are hard synthetic resin foams with a density of 35~
100Kg/m ³ , elongation at break in X-axis and Z-axis directions is 8~
60%, water vapor transmission rate in the Y-axis direction is 1.5g/m ²・hr
It turns out that it has to be less than or equal to.

[Table] Example, Comparative Example 2 This comparison was made from the perspective of investigating the characteristics that the insulation material inside the LLNG underground tank should have in applications where high loads are applied for a long period of time at extremely low temperatures. This is an example of an experiment. That is, the density is 35
~100Kg/m ³ A polystyrene extruded foam board (manufactured by Asahi Dow Co., Ltd.; Styrofoam) with a cell size of 0.6 to 0.1mm and a thickness of 100mm was first prepared using the extrusion device shown in Figure 7 according to the manufacturing method described in the text. was extruded in the X-axis direction (length direction) and then in the Z-axis direction (width direction).
At this time, only the medium compression ratio and the number of pressing processing conditions shown in Table 3 were selected as appropriate, and the other conditions were the same, and changes over time in density, compressive strength, elongation at break, water vapor permeability, and thermal conductivity were performed. Materials were created for evaluation of panel resistance, cryogenic resistance, creep resistance, etc. (Experiment Nos. 15 to 28) For comparison, extruded polystyrene foam board (Asahi Dow Co., Ltd.; Styrofoam) with a density of 28 to 100 kg/m ³ was used, unprocessed and processed only in the X-axis direction. We also manufactured products that were machined on both the X and Z axes. In addition, for comparison of foam materials, commercially available polystyrene bead foam board, polyvinyl chloride extrusion foam board, molded board (thickness: 20 mm), and polymethyl methacrylic acid extrusion foam board (asahi Dow Co., Ltd. prototype; thickness 20 mm) were used. ) with and without processing, and general-purpose rigid polyurethane (No.
47) Semi-rigid polyurethane (No. 48-50) formulated as an LNG underground tank insulation material was added as an evaluation material. For each foam, the density at break elongation in the X- and Z-axis directions, the water vapor permeability in the Y-axis direction, the change in thermal conductivity over time, the compressive strength and creep resistance in the Y-axis direction, and and cryogenic resistance (−
(160°C and -196°C), the results were evaluated using the methods and criteria described in the text, and Table 2 shows the results for each and the overall evaluation. The criteria for the overall evaluation were as follows. ◎; All characteristics are marked with ○ (satisfying the highest standards) ○: There are △ marks, but there are many ○ marks (satisfying the purpose of the present invention) ×; Those with at least one × mark ( According to the results in Table 2, the foam that satisfies the purpose of being used as an internal insulation material for tanks such as LNG according to the present invention is extruded polystyrene foam with a density of 35 to 100.
[Kg/m ³ ], elongation at break in X-axis and Z-axis directions is 8 to 60
%, water vapor transmission rate in the Y-axis direction is 1.5 [g/m ² hr]
It turns out that it must be less than or equal to. Furthermore, LNG
Enhances the function of underground tank insulation, allowing temperatures to reach -196℃
The foam of the present invention, which is considered as a cold insulator for liquid nitrogen and has other properties of the highest standard, has a density of 40 to 100.
[Kg/m ³ ], elongation at break in the X-axis and Z-axis directions Ex,
Ez is 12-40%, water vapor transmission rate in Y-axis direction is 1.0
It can be seen that it must be less than [g/m ² hr].

【table】

【table】 Table 3 Processing conditions Aging days until processing: 1 day Processing thickness: 100mm Processing speed (inlet belt): 12mm/sec Compression ratio (inlet/outlet belt speed ratio): 1.05 to 1.33 Pressing distance (distance between input and exit belt axes): 200mm Pressure fixing time: 3.6 seconds Number of processing: 1 to 3 times

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views of the composite plate of the present invention, Figures 3 and 4 are Figure 1 and Figure 4, respectively.
Figure 2 is a perspective view of the composite plate shown in Figure 1 bent into a cylindrical shape, Figure 5 is a perspective view of the composite plate shown in Figure 1 bent into a spherical shape, and Figure 6 is the composite plate shown in Figure 1. , a cross-sectional view showing an embodiment in which the heat insulating layer is formed into multiple layers when the thickness of the heat insulating material is required,
Fig. 7 is a schematic diagram showing a state in which the foam is compressed and given a high elongation rate, Fig. 8 is a diagram showing sampling positions and dimensions for measuring the rate of change in thermal conductivity over time;
Figure 9 is a principle diagram of an apparatus for accelerated moisture absorption for evaluating the temporal change characteristics of thermal conductivity, Figure 10 is a diagram showing a panel for evaluating cryogenic resistance, and Figures 11 and 12 are panels. Figure 11 is a diagram of the principle of the device for evaluating cryogenic resistance at -160
12 is a schematic diagram showing a test device immersed in liquid nitrogen;
The figure shows a composite body for measuring the amount of creep, and FIG. 14 is a schematic diagram showing a creep measuring device. 1... Foam, 2... Surface material, 3... Adhesive,
4, 4'... Composite board, 5... Reinforcing fiber layer, 6, 7,
8, 9... Clipping drive belt, 10... Foam, 1
1... Container, 12... Insulating material, 13... Temperature controller, 14... Water, 15... Test piece, 16... Packing, 17, 18... Circulating water inlet/outlet, 19... Cooling plate, 20 ...Cryogenic resistance test panel, 21...
...Test foam, 22...Urethane cryogenic adhesive, 23, 24...Plywood, 25...Cryogenic tank, 2
6...Liquid nitrogen cylinder, 27...Liquid nitrogen piping,
28...Liquid nitrogen flow rate automatic control valve, 29...Liquid nitrogen jet nozzle, 30...Perforated jammer plate, 31...
...Thermometer, 32...Nitrogen gas outlet, 33...Insulation material, 34...Liquid nitrogen immersion test device, 35...
Deep tray, 36...Liquid nitrogen, 37...Liquid nitrogen introduction valve, 38...Iron weight, 39...Iron support, 40...Creep measurement complex, 41, 4
2... Plywood, 43, 44... Adhesive, 45... Test piece for creep measurement, 46... Creep measuring device, 47... Dial cage, 48... Weight mount, 49... Weight, 50... ...Creep measuring device mount.

Claims (1)

[Scope of Claims] 1. A synthetic resin layer reinforced with plywood, glass fiber, or synthetic fiber is laminated and integrated on at least one surface of a hard synthetic resin foam,
The foam has a density of 35 to 100 kg/ ^m3 , with the thickness direction being the Y axis,
When the width and length directions are the X and Z axes, the water vapor permeability in the Y-axis direction Py≦1.5 [g/m ² hr], the elongation at break Ex and Ez in the X-axis and Z-axis directions is 60≧Ex≧ 8, 60≧Ex
A composite board for low-temperature insulation, characterized in that a foam layer of ≧8 (%) is provided.