SELF-COOLING FOAM-CONTAINING COMPOSITE MATERIALS

Abstract

Provided herein is a composite material that includes at least one thermoresponsive polymer and at least one organic foam material. Further provided herein is a method for producing the composite material and also to the use of the composite material for cooling and for regulating temperature.

Claims

1. A composite material comprising components: (A) at least one thermoresponsive polymer, (B) at least one organic foam material, the component (A) having a lower critical solution temperature (LCST), the lower critical solution temperature (LCST) being in the range from 5 to 70 C. and wherein component (B) is selected from polyurethane foam materials, wherein the composite material further comprises a component, and (C) at least one clay mineral, wherein component (C) is a layered silicate and wherein the lower critical solution temperature (LCST) being the temperature at which component (A) and water exhibit a miscibility gap.

2. The composite material according to claim 1, wherein component (A) is selected from the group consisting of poly(meth)acrylates, poly(meth)acrylamides, poly(meth)acryloylpyrrolidines, poly(meth)acryloylpiperidines, poly-N-vinylamides, polyoxazolines, polyvinyloxazolidones, polyvinylcaprolactones, polyvinylcaprolactams, polyethers, hydroxypropylcelluloses, polyvinyl ethers, and polyphosphoesters.

3. The composite material according to claim 1, wherein component (B) is open-cell to an extent of at least 50%.

4. The composite material according to claim 1, wherein component (C) is selected from the group consisting of montmorillonites and kaolinites.

5. The composite material according to claim 1, wherein the composite material comprises in the range from 0.5 to 50 wt % of component (A), in the range from 25 to 99.49 wt % of component (B), and in the range from 0.01 to 50 wt % of component (C), based in each case on the sum of the weight percentages of components (A), (B), and (C).

6. A method for producing a composite material according to claim 1, comprising the steps of: a) providing a mixture (M) that comprises the at least one thermoresponsive polymer (A), and b) preparing the at least one organic foam material (B) in the presence of the mixture (M) provided in step a) to give the composite material, wherein the mixture (M) provided in step a) further comprises at least one clay material (C).

7. The method according to claim 1, wherein the providing of the mixture (M) in step a) comprises a polymerization of at least one monomer selected from the group consisting of (meth)acrylates, (meth)acrylamides, (meth)acryloylpyrrolidines, (meth)acryloylpiperidines, N-vinylamides, oxazolines, vinyloxazolidones, vinylcaprolactones, vinylcaprolactams, alkylene oxides, vinyl ethers, and phosphoesters, to give the at least one thermoresponsive polymer (A).

8. The method according to claim 1, wherein the providing of the mixture (M) in step a) comprises the following steps: a1) providing a first dispersion that comprises the at least one clay mineral (C), a dispersion medium selected from the group consisting of water and an organic solvent, at least one monomer selected from the group consisting of (meth)acrylates, (meth)acrylamides, (meth)acryloylpyrrolidines, (meth)acryloylpiperidines, N-vinylamides, oxazolines, vinyloxazolidones, vinylcaprolactones, vinylcaprolactams, alkylene oxides, vinyl ethers, and phosphoesters, a2) polymerizing the at least one monomer present in the first dispersion provided in step a1), in the first dispersion, to give the at least one thermoresponsive polymer (A), to give a second dispersion that comprises the at least one clay mineral (C), the dispersion medium, and the at least one thermoresponsive polymer (A), and a3) drying the second dispersion obtained in step a2) to give the mixture (M).

9. The method according to claim 1, wherein the at least one clay mineral (C) is present in a swollen state during the polymerization in step a2).

10. The method according to claim 1, wherein the providing of the mixture (M) in step a) comprises a spray drying of the at least one thermoresponsive polymer (A) in the presence of the at least one clay mineral (C).

11. The method according to claim 1, wherein the mixture (M) provided in step a) comprises the at least one thermoresponsive polymer (A) in the form of particles and comprises the at least one clay mineral (C) in the form of particles, the particles of the at least one thermoresponsive polymer (A) having a D50 in the range from 200 nm to 5 mm, and the particles of the at least one clay mineral (C) having a D50 in the range from 50 nm to 3 mm, determined by light scattering and/or sieving.

12. A method of using a composite material according to claim 1 for cooling buildings, electrical assemblies, primary batteries or secondary batteries, exterior facades of buildings, of interiors, for production of medical products, and for regulating the heat in furniture for sitting, in vehicles, in footwear, and in apparel.

13. (canceled)

Description

EXAMPLES

[0239] Preparation of a Mixture (M) from Components (A) and (C)

[0240] The following components were used:

[0241] Monomers:

[0242] N-Isopropylacrylamide (NiPAAm) from Wako Chemicals and from TCl Chemicals

[0243] N,N-Methylenebisacrylamide (BIS) from AppliChem and Merck KGaA

[0244] [3-(Methacryloylamino)propyl]trimethylammonium chloride solution (MAPTAC; 50 wt % in water) from ABCR GmbH

[0245] Clay Mineral:

[0246] Sodium bentonite: EXM757 from Sd-Chemie

[0247] Initiators:

[0248] N,N,N,N-Tetramethylethylenediamine (TEMEDA) from ABCR GmbH

[0249] Potassium peroxodisulfate (KPS) from Sigma-Aldrich

[0250] Ammonium peroxodisulfate (APS) from Grssing GmbH Analytica

[0251] Sodium bentonite (162 g, 113 mmol of sodium) was swollen in deionized water (2 l). Then further deionized water was added, giving the dispersion a volume of 12 liters in total. NiPAAM (1000 g, 8840 mmol), BIS (50 g, 324 mmol, 5 wt % based on NiPAAM), and MAPTAC (50 g of a 50 wt % strength solution in water, 113 mmol, 5 wt % based on NiPAAM) were added to the dispersion, to give the first dispersion. After devolatilization with nitrogen, the first dispersion was heated to 80 C. and KPS (20 g, 74 mmol, 2 wt % based on NiPAAM) was added in order to initiate the polymerization of the monomers. The polymerization was carried out at 80 C. for 6 hours. After cooling had taken place, 5 liters of deionized water were added in order to reduce the viscosity of the resulting second dispersion. The particles of the mixture (M) present in the second dispersion had a diameter in the range from 1 to 2 mm. The water fraction of the second dispersion was 90 wt %, based on the overall weight of the second dispersion.

[0252] The second dispersion was subsequently dried by different methods.

[0253] a) Spray Drying of the Second Dispersion

[0254] Spray drying was carried out using a Nubilosa LTC-ME laboratory spray dryer. The entry temperature was set at 165 C., the exit temperature was regulated at 85 to 90 C. by means of the injected second dispersion. The second dispersion was atomized with compressed air (5 bar) through a two-component nozzle (diameter 2 mm). The residual moisture content of the resulting mixture (M) was 3 wt %. The mixture (M) obtained by spray drying is referred to below as (M-S).

[0255] b) Centrifugation and Subsequent Drying at Room Temperature

[0256] The resulting second dispersion was centrifuged at 4200 rpm in a CEPA LS laboratory centrifuge with a polyamide filter bag. The resulting mixture was subsequently dried at room temperature for 5 days and finally ground. The residual moisture content of the mixture (M) obtained was 6 wt %. The mixture (M) obtained by centrifugation and subsequent drying at room temperature is referred to below as (M-C).

[0257] In order to determine the morphology of the particles present in M-S and M-C, the particles were analyzed by environmental scanning electron microscopy (ESEM 2020 from ElectroScan), equipped with a GSED (gaseous secondary electron detector). The results are shown in FIGS. 1a and 1b for (M-S) and 2a and 2b for (M-C).

[0258] It can be seen that significantly smaller particles having a diameter of around 100 m are obtained by the spray drying (FIGS. 1a and 1b), in comparison to centrifuged and subsequently dried particles, whose diameter is around 300 m (FIGS. 2a and 2b). The particles of the clay mineral are disposed on the surface of the thermoresponsive polymer.

[0259] Production of Organic Foam Material and Composite Material

[0260] The organic foam material and the composite material were produced using the following components:

[0261] Polyols: [0262] P1 mixture of 95 parts by weight polyetherol P1a (obtained from the propoxylation of glycerol and subsequent ethoxylation (OH number=28 mg KOH/g, 15% EO content)) and 5 parts by weight polyetherol P1b (obtained from the propoxylation of glycerol and subsequent ethoxylation (OH number=42 mg KOH/g, 70% EO content)). [0263] P2 mixture of 42.5 parts by weight polyetherol P2a (obtained from the propoxylation of glycerol and subsequent ethoxylation (OH number=35 mg KOH/g)), 57 parts by weight polyetherol P2b (obtained from the propoxylation of glycerol and subsequent ethoxylation (OH number=27 mg KOH/g)), and 0.5 part by weight triethanolamine. [0264] P3 mixture of 66.5 parts by weight polyetherol P3a (obtained from the propoxylation of sucrose and glycerol (OH number=490 mg KOH/g)) and 33.5 parts by weight polyetherol P3b (obtained from the ethoxylation of trimethylolpropane (OH number=600 mg KOH/g)). [0265] P4 mixture of 61 parts by weight polyetherol P4a (obtained from the propoxylation of sucrose and glycerol (OH number=450 mg KOH/g)), 25.5 parts by weight polyetherol P4b (obtained from the ethoxylation/propoxylation of vicinal toluenediamine)), and 13.5 parts by weight polyetherol P4c (obtained from the propoxylation of trimethylolpropane (OH number=160 mg KOH/g)).

[0266] Catalysts:

[0267] K1: diazabicyclo[2.2.2]octane (DABCO)

[0268] K2: N,N-dimethylcyclohexane

[0269] Stabilizer:

[0270] Silicone surfactant DABCO DC 193, Air Products

[0271] Blowing Agents:

[0272] Water and cyclopentane (Merck KGaA)

[0273] Superabsorbent (SAP):

[0274] Luquasorb 1010 from BASF SE, polyacrylate, crosslinked

[0275] Isocyanate: [0276] Iso 1: mixture of 2,4-methylenediphenyl isocyanate (2,4-MDI), 4,4-methylenediphenyl isocyanate (4,4-MDI), and polymeric MDI (polymeric methylenediphenyl isocyanate), NCO content: 33% [0277] Iso 2: uretonimine-modified isocyanate prepolymer based on methylenediphenyl isocyanate (MDI), NCO content=28 wt % [0278] Iso 3: polymeric MDI (polymeric methylenediphenyl isocyanate) (Lupranat M 20 W, BASF SE), NCO content=32 wt %

[0279] Mixture (M):

[0280] M-S (Spray-Dried)

[0281] To produce the organic foam material, the polyol, the catalyst, the stabilizer, and the blowing agent were premixed with thorough stirring in a disposable container in the quantities reported in table 1, after which the isocyanate was added and the mixture was homogenized by vigorous stirring within 5 seconds. The reaction mixture was then immediately transferred to a metal mold with dimensions of 404040 cm, in which it foamed and cured.

[0282] The resulting cubes of the organic foam material were then cut into slices 2 cm thick and used for the passive cooling tests.

[0283] To produce a composite material additionally comprising the mixture (M) or the superabsorbent (SAP) as well as the organic foam material, the organic foam material was produced as described above, but the mixture (M) or the superabsorbent (SAP) was first dispersed together with the polyol, catalyst, stabilizer, and blowing agent before the isocyanate was added.

[0284] The start time, the gelling time, and the rise time, and also the density, of the resultant organic foam materials and composite materials are reported in table 1.

[0285] The start time is the time from the start of the mixing of polyol, catalyst, stabilizer, blowing agent, and isocyanate until a change in or marked increase in the viscosity of the reaction mixture becomes visually perceptible.

[0286] The gelling time is the timespan from the start of the mixing of polyol, catalyst, stabilizer, blowing agent, and isocyanate until the state is reached in which the product mixture is no longer fluid. The gelling time is determined by contacting a wooden stick with the rising foam, and corresponds to the point in time at which strings can be observed for the first time when the wooden stick is being extracted.

[0287] The rise time is the time from the start of the mixing of polyol, catalyst, stabilizer, blowing agent, and isocyanate up to the end of the rising process.

[0288] It is apparent that the superabsorbent provides a significant increase in particular in the start time and the gelling time and also in the density of the composite materials contained, relative to pure organic foam materials. The mixture (M) exhibits virtually no effect on the start time and gelling time and also the density.

[0289] The organic foam materials and composite materials of examples V1, B2, B3, B4, V5, and V6 are flexible foam materials (open-cell); the organic foam materials and composite materials of examples V7, B8, and B9 are semirigid foam materials; the organic foam materials and composite materials of examples V10, B11, and B12 are water-foamed rigid foam materials (closed-cell), and the organic foam materials and composite materials of examples V13, B14, B15, B16, V17, and V18 are rigid foam materials (closed-cell) foamed with water/cyclopentane.

TABLE-US-00001 TABLE 1 P1 P2 P3 P4 K1 K2 Stabi- Cyclo- Iso 1 Iso 2 Iso 3 Gel- [parts [parts [parts [parts [parts [parts lizer Water pentane (M-S) SAP [parts [parts [parts Start ling Rise Den- by by by by by by [parts [parts [parts by [parts [parts by by by time time time sity wt.] wt.] wt.] wt.] wt.] wt.] by wt.] by wt.] wt.] by wt.] by wt.] wt.] wt.] wt.] [s] [s] [s] [g/l] V1 96.2 0.5 0.3 3 46 16 119 180 52 B2 96.2 0.5 0.3 3 3 46 16 119 180 51 B3 96.2 0.5 0.3 3 14 46 17 119 180 52 B4 96.2 0.5 0.3 3 25 46 18 119 180 54 V5 96.2 0.5 0.3 3 1.5 46 22 200 280 84 V6 96.2 0.5 0.3 3 4.8 46 32 220 290 95 V7 95 0.8 1.3 2.9 62 12 56 61 49 B8 95 0.8 1.3 2.9 14 62 12 56 83 56 B9 95 0.8 1.3 2.9 25 62 14 57 91 60 V10 95.9 0.1 0.5 1 2.5 140 24 71 90 50 B11 95.9 0.1 0.5 1 2.5 7 140 24 70 91 51 B12 95.9 0.1 0.5 1 2.5 14 140 26 73 93 51 V13 92.4 1.4 0.7 3 2.5 13 134 8 47 78 27 B14 92.4 1.4 0.7 3 2.5 13 3 134 8 47 79 26 B15 92.4 1.4 0.7 3 2.5 13 14 134 9 49 80 29 B16 92.4 1.4 0.7 3 2.5 13 25.6 134 9 50 78 29 V17 92.4 1.4 0.7 3 2.5 13 3 134 19 200 288 63 V18 92.4 1.4 0.7 3 2.5 13 25.5 134 35 250 340 122

[0290] Water Absorption of the Composite Materials

[0291] Four cuboidal blocks with edge lengths of 662 cm, made from the different organic foam materials and the composite materials (specimens), were each first weighed, then placed into deionized water, and taken out after 1 hour and again after 91 hours. The water absorption, determined as the average value from four measurements, corresponded in this case to the weight increase after drip-drying of the specimens, minus the original dry weight of the specimen. The water content of the specimens was then calculated relative to the total weight of the specimen, in wt %.

[0292] The water content of the various specimens is reported in table 2.

TABLE-US-00002 TABLE 2 Water content Water content after 1 h [wt %] after 91 h [wt %] V1 77 87 B2 68 94 B3 69 94 B4 69 92 V5 76 90 V6 80 91 V7 68 86 B8 73 93 B9 70 91 V10 20 36 B11 34 48 B12 70 82 V13 34 51 B14 32 60 B15 43 70 B16 55 74 V17 44 61 V18 70 90

[0293] It can be seen that rigid foam materials exhibit the lowest water absorption, while the flexible foam materials exhibit the highest water content. This can be attributed to the open-cell nature of the flexible foam materials.

[0294] On the basis of the water content after 1 hour and after 91 hours, it is apparent that, while the composite materials of the invention do absorb water more slowly than the pure organic foam material and also than the composite materials which comprise a superabsorbent, they nevertheless have at least the same or else higher proportions of water after 91 hours than the comparative materials. An exception is comparative experiment V18. The high superabsorbent content of the material ensures a likewise high water absorption and hence a high water content, but the foam has a very coarse, heterogeneous foam structure and also a high density. The disadvantages which result from these facts, in terms of mechanical and insulation properties, make the material an unattractive one for subsequent application as composite material.

[0295] Passive Cooling

[0296] For determination of the passive cooling behavior of the composite materials produced in comparison with pure organic foam materials, sample specimens of the materials with dimensions of 662 cm were placed at an angle of 40 and at a distance of 35 cm from an infrared lamp (500 W halogen). A constant stream of air was passed over the sample specimens at a flow rate of 0.1 m/s. An infrared camera was used to determine the temperature profile on the surface of the materials.

[0297] In order to determine the change in water content, the sample specimens of the composite material and of the comparative materials were placed on a balance and the weight of the sample specimens was determined as a function of time.

[0298] In order to determine the cooling effect of the composite material and of the comparative materials, a sample specimen of the composite material or of the comparative material was placed on a panel of a pure organic foam material and, between the panel of the organic foam material and of the composite material or of the comparative material, a thermocouple was introduced, which determined the temperature on the reverse of the sample specimens to be tested.

[0299] a) Surface Temperature and Water Content

[0300] The surface temperatures and also the water content of the composite material of example B3 and of the comparison material of example V1 were determined over a period of 360 minutes. The initial water content of the samples (94 wt % for B3 and 87 wt % for V1; see table 2) was set at 100% and the percentage decrease in weight of both samples over time was monitored.

[0301] FIG. 3 shows the results of this test.

[0302] It can be seen that at the start of the measurement, the rate of evaporation of the water is identical in both examples B3 and V1. After about 30 minutes, already more water has evaporated from the composite material of example B3. Over the entire measurement period, more water evaporates from the material of example B3 than from the comparison material V1, and so a smaller water content property is left in the case of example B3. At the same time, owing to the greater rate of evaporation, the inventive composite material B3 exhibits a lower surface temperature and hence a greater cooling effect.

[0303] b) Two-Layer Measurements

[0304] For the measurements on flexible foam materials, the comparative material employed was the organic foam material of comparative example V1; the composite material used was that of example B3, and the composite material of comparative example V6 was also used. The plate of organic foam material on which the composite material and the comparative materials V1 and V6 were placed was an organic foam material as per comparative example V1.

[0305] For the measurement on rigid foam materials, the organic foam material of comparative example V13 was employed as composite material, as was the composite material of example B16 and the composite material of comparative example V18. The plate of organic foam material on which the composite material was placed was the organic foam material as per comparative example V13.

[0306] The results are reported in FIGS. 4a and 4b for the flexible foam materials and in FIGS. 5a and 5b for the rigid foam materials.

[0307] FIGS. 4a and 5a each show the surface temperature over the measurement period, with FIGS. 4b and 5b each showing the reverse temperatures.

[0308] From FIGS. 4b and 5b it is apparent that the reverse temperature of the composite material of the invention is lower in each case than that of the comparative examples. With the composite material of the invention, therefore, a higher cooling effect is achieved than with the materials of the comparative examples.