Flexible PCM Sheet Materials

Abstract

The invention relates to flexible PCM sheet materials having a high latent thermal energy storage density for the purpose of heat management. The flexible PCM sheet material includes a flexible supporting structure and phase-change-material elements arranged thereon separately in a specific geometry. The phase-change-material elements are geometrically defined structures composed of polymer-bound phase-change material. The flexible PCM sheet materials are characterized by a high latent heat storage capacity and optimized thermal conductivity, are dimensionally stable even in the event of temperature changes and after phase transitions, can be rolled, folded, wound, or cut to size without problems, and can be transported, stored processed, or used in a single layer or in multiple layers.

Claims

1. A flexible PCM sheet material with high latent thermal energy storage capacity comprising a flexible 2-dimensional carrier structure having separately arranged, geometrically defined structures of a polymer-bound phase change material applied on the surface thereof and connected firmly to the earlier structure, the phase change material being bound by at least two polymers, of which at least one polymer is selected from the group of styrene-containing, block copolymers and at least one polymer is selected from the group of styrene-free ethylene/butylene copolymers, wherein the sheet material is dimensionally stable even on phase change, has a latent thermal energy storage capacity of 100 to 250 J/g and/or 300 to 1000 kJ/m.sup.2, and is processible in rolled, folded, wound, cut-to-size or multi-ply form.

2. The flexible PCM sheet material as claimed in claim 1, wherein the carrier structure comprises webs, nonwovens, knitwear, knittings, braids of fibers or yarns or slit films, films or membranes.

3. The flexible PCM sheet material as claimed in claim 2, wherein the material of the carrier structure comprises polyamide, polyester, polypropylene, cellulose, carbon, metal, glass, natural fibers or mixtures of these materials.

4. The flexible PCM sheet material as claimed in claim 1, wherein said PCM sheet material comprises 1 to 10% by weight of carrier structure and 90 to 99% by weight of geometrically defined structures of the polymer-bound phase change material applied to said carrier structure. cm 5. The flexible PCM sheet material as claimed in claim 1, wherein the polymer-bound phase change material comprises 10 to 30% by weight of carrier polymers and 90 to 70% by weight of phase change material.

6. The flexible PCM sheet material as claimed in claim 1, wherein said PCM sheet material contains 5 to 20% by weight of inorganic or organic additives, based on the weight of the total cast-on material.

7. The flexible PCM sheet material as claimed in claim 1, wherein said PCM sheet material is coated superficially with a layer 3 to 10 m thick of polymeric, metallic or ceramic material or covered with a textile sheet comprising said materials.

8. The flexible PCM sheet material as claimed in claim 1, wherein the polymer-bound phase change material has a weight per unit area of 1 to 4 kg/m.sup.2.

9. The flexible PCM sheet material as claimed in claim 1, wherein said PCM sheet material is flow-permeable by liquid or gaseous thermal media.

10. A method for producing flexible PCM sheet materials with high latent thermal energy storage capacity as claimed in claim 1, comprising fixing a plastified mass of a polymer-bound phase change material firmly in geometrically defined structures on a fabric-like carrier material, by applying melt-liquefied, polymer-bound phase change material to the carrier material as spherical, square, rectangular or polygonal separate shaped elements having a thickness of 1 to 10 mm by injection molding, spraying, spread-coating or unpressurized casting by means of a forming apparatus in a continuous or discontinuous process.

11. Buildings, heat sinks in electrical engineering, vehicles, or single-ply or multi-ply jacketing for pipelines comprising the flexible PCM sheet material as claimed in claim 1 for storing heat and cold and for thermal regulation.

12. The flexible PCM sheet material as claimed in claim 2, wherein the carrier structure comprises webs having a large mesh size or porous or braided structures.

13. A method for producing flexible PCM sheet materials with high latent thermal energy storage capacity as claimed in claim 10, wherein the spherical, square, rectangular or polygonal separate shaped elements have a thickness of 1 to 5 mm.

Description

EXAMPLE 1

[0024] Using a ZSE 40 twin-screw extruder from Leistritz) having an l/d ratio of 52:1, PCM polymer pellets are first formed from the following starting materials: [0025] 80% by weight of PCM material (Nacolether 12 from Sasol GmbH, long-chain dialkyl ether having a m.p. of 32 C.) [0026] 10% by weight of styrene block copolymer SEEPS (polystyrene-b-poly(ethylene-ethylene/propylene)-b-polystyrene; Septon 4055 from Kuraray Co. Ltd.) [0027] 5% by weight of OH-terminated. styrene to copolymer (SeptonHG 252 from Kuraray Co. Ltd.) [0028] 5% by weight of crystalline ethylene-butylene copolymer (type 6201 B from JSR Dynaron).

[0029] The extrusion die was connected via an adapter plate to the cutting head of a Gala underwater pelletizer (Gala Inc.). Pellets having a diameter of 4 to 5 mm were obtained.

[0030] The thermal storage capacity of the resulting pellets at the phase change temperature of the PCM with a switching temperature of 32 C. was 215 J/g.

[0031] The PCM polymer pellets were dried in a forced air drying cabinet at room temperature of 25 C. These pellets were then melted in a vertical single-screw extruder at 120 C., and the PCM polymer melt was supplied via an adapter to a die having multiple conical cuboidal or conical cylindrical openings, and the very low-viscosity PCM polymer melt was cast through the cuboidal or cylindrical openings onto a wide-meshed polyamide net 15 cm wide which was located directly beneath the multiple casting die. After the PCM polymer melt castings had cooled, the casting die was raised and the polyamide fabric was moved on, on a conveyor belt in each case, after which a further casting was carried out via the melt die.

[0032] By this way a polyamide net tape was obtained with PCM polymer blocks or PCM polymer cylinders applied closely thereto. The minimum distances between the PCM polymer blocks or PCM polymer cylinders were 1 mm. The height of the PCM polymer blocks or PCM polymer cylinders was 3 mm. The PCM polymer blocks had an edge length of 10 mm, and the PCM polymer cylinders had a diameter of 10 mm. The weight per unit area of the obtained polyamide fabric coated by the applied PCM polymer blocks or PCM polymer cylinders was 1950 and 1850 g/m.sup.2, accordingly. The thermal storage capacity of the obtained polyamide fabric/PCM polymer assemblies was 200 J/g or, on an area basis, 390 KJ/m.sup.2 and 370 KJ/m.sup.2.

[0033] The cuboidal or cylindrical PCM polymer castings were joined very firmly to the woven polyamide fabric, even at the corresponding phase change temperature. The resultant mats of polyamide fabric and PCM polymer castings applied thereon (see FIGS. 1 and 2) could be wound up as cylinders or placed one on top of another in the form of multiple plies, and tests of loading with warm air and water showed that these mat constructions presented only a very low flow resistance to the entering and emerging thermal flows.

[0034] A particular advantage of the invention is that these PCM sheet materials can also be deformed in the cold state at any time to form rolled and stacked articles, even if using PCM castings with a high phase transition temperature. The stiffness of the relatively hard PCM castings is not a disruptive factor here, since the PCM sheet materials are very flexibly deformable at the edge intermediate spacings.

[0035] In a test chamber, a number of pieces of these polyamide fabric/PCM polymer mats were clamped firmly into two lateral frames and so arranged closely one behind the other. Hot air at 40 C. was passed through the test chamber, in order to load the polyamide fabric/PCM polymer mats with heat, and to melt the PCM they contained (Nacol ether 12) at 32 C. At this phase transition temperature, the polyamide fabric/PCM polymer mats remained firmly clamped in, and did not sag or flap, as otherwise observed in the case of relatively thick PCM polymer films and PCN polymer plates.

EXAMPLE 2

[0036] Similar as indicated in example 1, PCM polymer pellets of the following composition: [0037] 80% by weight of PCM material (Nacolether 12 from Sasol GmbH, long-chain dialkyl ether) [0038] 10% by weight of styrene block. copolymer SEBS (polystyrene-b-poly(ethylene/butylene)-b-polystyrene; Septon 8004 from Kuraray Co. Ltd.) [0039] 5% by weight of OH-terminated styrene block copolymer (Septon HG 252 from Kuraray Co. Ltd.) [0040] 5% by weight of crystalline ethylene-butylene copolymer (type 6201 B from JSR Dynaron)

[0041] were again produced in a Leistritz ZSE 40 twin-screw extruder and downstream underwater pelletizer, then dried and applied to a wide-meshed polyamide fabric in a single-screw extruder using a special casting die.

[0042] The polyamide fabric with the PCM polymer castings (cuboidal or cylindrical) was then sprayed on both sides with a 5% by mass PA solution (of Ultramid 1C) and the excess solvent was evaporated at room temperature. The thickness of the PA coating was about 5 m. It proved to be a 100% barrier against the exudation of PCM.

EXAMPLE 3

[0043] Much as indicated in example 1, PCM polymer pellets were again produced in the Leistritz ZSE 40 twin-screw extruder and downstream underwater pelletizer, then dried and subsequently applied to a wide-meshed polyamide fabric in a single-screw extruder, using a special casting die.

[0044] The material composition of the PCM polymer was altered in this case, however: [0045] 70 weight % of PCM material (Nacolether 16 from Sasol GmbH, long-chain dialkyl ether) [0046] 8% by weight of styrene block copolymer SEEPS (Septon 4055 from Kurarav Co, Ltd.) [0047] 4% by weight of OH-terminated styrene block copolymer (Septon HG 252 from Kuraray Co. Ltd.) [0048] 3% by weight of crystalline ethylene-butylene copolymer (type 6021 B from JSR Dynaron) [0049] 15 weight % of zinc oxide powder produced in the Leistritz ZSE 40 twin-screw extruder and downstream underwater pelletizer, then dried and applied to a wide-meshed polyamide fabric in a single-screw extruder, using a special casting mould.

[0050] The zinc oxide did not only improve the thermal conductivity of 0.2 W/mK (pure PCM polymer compound) to a value of 0.6 W/mK, but also resulted in a sharp reduction in the exudation of paraffin at phase transition, of the PCM.

[0051] The resulting polyamide fabric/PCM polymer mats were provided with an additional thin cotton coating by making up process, in order to meet requirements of various application-related aspects.

[0052] The thermal storage capacity of the resulting PCM polymer 2.0 pellets was 175 J/g, and the thermal capacity of the resulting polyamide fabric/PCM polymer sheet material was 160 J/g. On an area basis, this was 341 KJ/m.sup.2 for castings having a PCM polymer block structure and 323 KJ/m.sup.2 for PCM polymer castings having a cylinder structure.

EXAMPLE 4

[0053] For predetermined shapes and dimensions of the PCM polymer castings and thermal storage capacities of the PCM, the packing parameters of the carrier material by the PCM polymer castings can he calculated and presented in table form. With the aid of such tables it is possible to calculate the packing configuration required for an application. The calculations in this example were based on a synthetic paraffin having a phase change enthalpy of 248 kJ/kg*15 K. The compounding reduces this capacity by 20%. A full-area plate with a height of 5 mm based on this formula would have a capacity of 794 kJ/m.sup.2.

[0054] This figure was employed as a baseline comparison figure for the calculation of the remaining fraction.

[0055] If, for example, a capacity of 600 kJ/m.sup.2 is required (presettings: height: 5 mm, compound described above), the following is evident from table 1:

[0056] 1. circular base form not possible

[0057] 2. square base form offers the required capacity with a distance between 1-2 mm.

[0058] 3. calculation:

600 (kJ/m.sup.2)/198 kJ/kg*15K=3.03 kg of PCM (of above specification)

3.03 kg of PCM/0.8 (g/cm.sup.3)=3.79 dm.sup.3=3790 cm.sup.3

3790 cm.sup.3/0.5 cm.sup.3=7580 pieces

7580=87, rounded down to 87

100 (cm)/87=1.15 mm

[0059] The distance between the PCM castings must be 1.15 mm for a thickness of 5 mm and edge length of 1 cm in order to achieve a capacity of 600 kJ/m.sup.2

TABLE-US-00001 TABLE 1 comparison of the thermal storage capacity of carrier structures loaded with separate PCM polymer castings to form PCM sheet materials with continuous PCM coating. Casting height = 5 mm Distance Capacity in between % relative the PCM Capacity/ Form of base to full-area Particles in m.sup.2 area of coverage mm in J castings (5 mm) 0.5 716 suuare 90 1 643 square 81 2 547 square 69 3 458 square 58 0.5 562 circular 71 1 505 circular 64 2 479 circular 54 3 360 circular 45

[0060] As can be seen from the table, a greater capacity per unit area can be achieved using square base areas. Circular base areas produce Smaller unit-area capacities. When staggered, these figures do become a little better, but do not achieve the same figures as the square areas.

[0061] The column Capacity in % relative to full-area coverage indicates how much capacity is left over with different geometries (square or circular) and distance dimensions relative to a full-area PCM layer.

[0062] Assumption of the height of the castings and height of the PCM layer is 5 mm; on reduction of the height, the capacity decreases linearly and is therefore not recorded in the table.

[0063] In the case of the loading figures in %, there are gentle jumps. These jumps are a result of the fact that, depending on element spacing, whole rows do no longer come about at the edge. In practice, they could be cut mechanically, and then the ratios would be linear. All other base geometries (e.g., triangle, rectangles, etc.) are situated in each case between the figures for square and circle, in terms of utilization of loading per unit area, and are therefore not listed further in the table.