Appliances having sound and thermal insulation based on viscoelastic polyurethane

Abstract

Thermal and acoustic insulation is provided to an appliance or a component thereof through a layer of a viscoelastic polyurethane foam. The selection of a viscoelastic foam of this density provides efficient thermal insulation as well as acoustic insulation.

Claims

1. An appliance comprising at least one thermally and acoustically insulated component, wherein the insulated component has an insulation structure applied to at least one surface thereof, the insulation structure including at least one layer of a viscoelastic polyurethane foam having a thickness of 17 to 50 mm and an areal density of 3000 to 7500 g/m.sup.2, the viscoelastic polyurethane being characterized in that: a) the viscoelastic polyurethane foam has a resiliency value of at most 20% as measured according to ASTM 3574; b) the viscoelastic polyurethane foam has a recovery time of at least 3 seconds as measured according to ASTM D3574 Test M; c) the viscoelastic polyurethane foam has a lambda value of less than 0.075 W/m- K as measured according to EN 12667; and d) the viscoelastic polyurethane foam is made in the reaction of an aromatic polyisocyanate with a mixture of isocyanate-reactive materials that includes at least 20 weight-percent, based on the combined weight of all isocyanate-reactive materials in the mixture, of at least one polyol having a molecular weight of at least 750, a hydroxyl equivalent weight of 225 to 450 and 2 to 4 hydroxyl groups per molecule, and water in an amount of at least 0.2 parts per 100 parts by weight of the mixture of isocyanate-reactive materials, wherein the isocyanate index is 60 to 100; wherein the appliance is a dishwasher, oven, refrigerator, freezer, clothes washing machine, clothes dryer, garbage disposal, trash compactor, vacuum cleaner or HVAC device.

2. The appliance of claim 1, which is a dishwasher.

3. The appliance of claim 1, wherein the thermally and acoustically insulated component is a housing for a motor, pump, fluid handling system or a part of such a housing; a cabinet that encloses functional components of the appliance; a bottom, top, vertical wall or door of such a cabinet; or a functional component or device that forms part of the appliance.

4. The appliance of claim 1, the volume density of the viscoelastic polyurethane foam is 250 to 500 kg/m.sup.3, the resiliency value of the foam is at most 15%, and the mixture of isocyanate-reactive materials includes at least 50 weight-percent, based on the combined weight of all isocyanate-reactive materials in the mixture, of the polyol having a molecular weight of at least 750, a hydroxyl equivalent weight of 225 to 450 and 2 to 4 hydroxyl groups per molecule.

5. The appliance of claim 1 wherein the viscoelastic polyurethane foam has a resiliency of at most 8% and a recovery time of at least 10 seconds.

6. The appliance of claim 1 wherein the viscoelastic foam layer constitutes the entire insulation structure.

7. The appliance of claim 1 wherein insulation structure includes one or more layers of additional acoustic and/or thermal insulating material.

8. The appliance of claim 7 wherein the additional layer(s) is one or more of a high density polymer foam; one or more layers of a mastic; one or more layers of a fiber batt; or one or more layers of a low density polymer foam.

9. A method of insulating an appliance, comprising applying an insulation structure to at least one component of the appliance, wherein the insulation structure includes at least one layer of a viscoelastic foam having a thickness of 17 to 50 mm and an areal density of 3000 to 7500 g/m.sup.2, the viscoelastic polyurethane being characterized in that: a) the viscoelastic polyurethane foam has a resiliency value of at most 20% as measured according to ASTM 3574; b) the viscoelastic polyurethane foam has a recovery time of at least 3 seconds as measured according to ASTM D3574-08 Test M; c) the viscoelastic polyurethane foam has a lambda value of less than 0.075 W/m- K as measured according to EN 12667; and d) the viscoelastic polyurethane foam is made in the reaction of an aromatic polyisocyanate with a mixture of isocyanate-reactive materials that includes at least 20 weight-percent, based on the combined weight of all isocyanate-reactive materials in the mixture, of at least one polyol having a molecular weight of at least 750, a hydroxyl equivalent weight of 225 to 450 and 2 to 4 hydroxyl groups per molecule, and water in an amount of at least 0.2 parts per 100 parts by weight of the mixture of isocyanate-reactive materials, wherein the isocyanate index is 60 to 100; wherein the appliance is a dishwasher, oven, refrigerator, freezer, clothes washing machine, clothes dryer, garbage disposal, trash compactor, vacuum cleaner or HVAC device.

10. The method of claim 9, wherein the appliance is a dishwasher.

11. The method of claim 9, wherein the thermally and acoustically insulated component is a housing for a motor, pump, fluid handling system or a part of such a housing; a cabinet that encloses functional components of the appliance; a bottom, top, vertical wall or door of such a cabinet; or a functional component or device that forms part of the appliance.

12. The method of claim 9, wherein the aromatic polyisocyanate and mixture of isocyanate-reactive materials are applied directly to the component and cured thereof to form the viscoelastic polyurethane foam.

13. The method of claim 9 wherein the viscoelastic polyurethane foam is foamed apart from the component, and then affixed to the component.

14. The method of claim 9 wherein the viscoelastic polyurethane foam has a resiliency of at most 8% and a recovery time of at least 10 seconds.

15. The method of claim 9 wherein the viscoelastic foam layer constitutes the entire insulation structure.

16. The method of claim 9 wherein insulation structure includes one or more layers of additional acoustic and/or thermal insulating material.

17. The method of claim 16 wherein the additional layer(s) is one or more of a high density polymer foam; one or more layers of a mastic; one or more layers of a fiber batt; or one or more layers of a low density polymer foam.

Description

(1) The following examples are provided to illustrate the invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated. In the following examples:

(2) MEG is monoethylene glycol.

(3) The Cell Opener is a high molecular weight copolymer of propylene oxide and a major amount of ethylene oxide.

(4) DEOA is diethanolamine.

(5) Catalyst A is a commercially available bis(2-dimethylaminoethyl)ether solution.

(6) Catalyst B is a commercially available triethylenediamine solution.

(7) Catalyst C is a commercially available tin catalyst.

(8) Surfactant A is a silicone surfactant commercially available as Ortegol 501 from Evonik.

(9) Surfactant B is a silicone surfactant commercially available as Tegostab B8715 LF2 from Evonik.

(10) Polyol A is a nominally trifunctional poly(propylene oxide), having a molecular weight of about 1000 and a hydroxyl equivalent weight of about 335.

(11) Polyol B is a nominally trifunctional, 5000 molecular weight ethylene oxide-capped poly(propylene oxide).

(12) Polyol C is a nominally trifunctional, 450 molecular weight poly(propylene oxide).

(13) The Isocyanate is prepolymer of a high molecular weight trifunctional polyether polyol and a mixture of MDI and PMDI. The Isocyanate has an average isocyanate functionality of 2 to 3 and an isocyanate equivalent weight of approximately 140 g/mol.

(14) To produce the following examples, viscoelastic foams are prepared from the following formulations:

(15) TABLE-US-00001 Parts By Weight Component Formulation 1 Formulation 2 Formulation 3 MEG 0.585 0.6 0.573 Glycerin 0.195 0.2 0.191 DEOA 0.78 0.8 0.763 Cell Opener 3.9 0 3.817 Catalyst A 0.146 0.150 0.219 Catalyst B 1.949 4.200 3.053 Catalyst C 0.195 0.33 0.315 Water 0.224 0.500 0 Polyol A 75.458 77.420 70.076 Polyol B 9.747 10 9.542 Polyol C 4.873 5 4.771 Surfactant A 1.95 0 1.91 Surfactant B 0 0.8 0 Zeolite 0 0 4.77 Isocyanate To 75 index To 75 index To 75 index % Water based on 0.23% 0.52% 0 isocyanate- reactive materials Volume Density 500 kg/m.sup.3 300 kg/m.sup.3 >800 kg/m.sup.3

(16) Viscoelastic foams made from Formulations 1 and 2 have resiliency values below 15% as measured according to ATM 3574 and recovery times greater than 3 seconds as measured according to ASTM D3574-08 Test M.

(17) Test specimens are prepared as follows: All components except the Isocyanate are mixed to form a curative. The curative and Isocyanate are processed through a spray robot to form a reaction mixture that is sprayed onto steel plates (5005000.5 mm, weighing 650 g) and cured on the steel plates. The weights of the coated plates and the foam thickness are measured in each case.

(18) The thermal conductivities of the coated plates are determined in accordance with EN 12667.

(19) Sound transmission loss is measured according to EN ISO 15186:2010. Transmission loss (TL) is calculated according to the relationship:
TL=L.sub.p,sL.sub.l,r6DB.
wherein L.sub.p,s is the sound pressure level in decibels (DB) in the room containing the sound source and L.sub.l,r is the measured sound pressure in DB in the room containing the test specimen. Sound transmission loss is measured in the frequency range 50 to 10,000 Hz.

(20) Damping loss is measured by suspending the coated plate using two elastic strings so it is free to vibrate. The suspended plate is suspended by striking it with a hammer. The hammer is a PCB 086D05 impact hammer controlled by a PCB 353 B18 accelerometer. The acceleration is measured at a point close to a bottom corner, and five excitation points are chosen in different areas of the plate. For each excitation point, three measurements are made using an 8 channel Samurai Sound Book and Software. Structural reverberation time is calculated in the .sup.rd octave frequency bands from 100 to 800 Hz. Results are averaged to obtain a reverberation time RT, calculated from a decay of 20 DB but referred to a standardized decay of 60 DB. Tests are conducted at room temperature.

(21) Examples 1-5 are made by coating the steel plates with either Formulation 1 or Formulation 2, at coating weights as indicated in Table 1. Comparative Sample A is the uncoated steel, and Comparative Sample B is a steel panel coated with a bitumen layer. Comparative C is made by coating a steel plate with Formulation 3. Test results from these various samples are as indicated in Table 1.

(22) TABLE-US-00002 TABLE 1 Approx. Coating Areal coating Desig- Descrip- Mass Mass, Density thickness Lamdba Damping Transmission nation tion g g g/m.sup.2 mm W/m- K. Factor Loss, DB A* Uncoated 650 0 N/A 0 N/A 0.003 24.4 Steel B Steel, 1584 934 3736 4 0.18 0.18 33.6 Bitumen coating 1 Steel + 2080 1430 5720 11 0.07 0.14 36.4 Form. 1 2 Steel + 2800 2150 8600 17 0.07 0.18 36.9 Form. 1 3 Steel + 1460 810 3240 11 0.05 0.16 32.6 Form. 2 4 Steel + 1515 865 3460 11.5 0.05 0.17 32.2 Form. 2 5 Steel + 1780 1130 4520 15 0.05 0.18 32.5 Form. 2 C Steel + 3580 2930 11720 11 0.16 0.16 39.2 Form. 3 *Not an example of the invention.

(23) Comparative Sample A represents a baseline case from which the acoustic and thermal insulation abilities of the coatings can be assessed. In Comparative Sample B, the conventional bitumen coating increases the damping factor and transmission loss very significantly, but is a poor thermal insulator. The dense polyurethane elastomer coating of Comparative Sample C performs similarly to Comparative Sample B, with good acoustic properties but poor thermal properties.

(24) Examples 1-5 show the highly beneficial effect of a viscoelastic foam layer. Damping and transmission loss are comparable to those of Comparative Samples A and B. Unlike Comparative Samples A and B, Examples 1-5 exhibit very low lambda values, indicating that the viscoelastic foams provide excellent thermal resistance in addition to excellent acoustic properties.

(25) In Examples 6-10, particulate additives are included in Formulations 1, and therefore are incorporated into the foam. Comparative Samples D, E and F are made using Formulation 3, in each case modified with a particulate additive. The additives in each case are:

(26) TABLE-US-00003 Foam Designation Formulation Additive 6 1 Core-shell rubber particles (13.1% based on foam weight) 7 1 Barium sulfate (27.3% based on foam weight) 8 1 Barium sulfate (27.3% based on foam weight) 9 1 Recycled tires (18.4% based on foam weight) 10 1 Recycled tires (18.4% based on foam weight) D 3 Core-shell rubber particles (13.2% based on foam weight) E 3 Barium sulfate (27.6% based on foam weight) F 3 Recycled tires (18.6% based on foam weight)

(27) For each of Examples 6-8 and Comparative Samples D and E, layers of the foam material are applied to steel plates by spraying the filled formulation onto the plates, and curing the formulation on the plates. For examples, 9 and 10 and Comparative Sample E, the filler material is mixed manually into the foam formulation, which is then spread onto the plates and cured. This results in somewhat higher volume densities for these samples. Results of the testing of these samples are as indicated in Table 2.

(28) TABLE-US-00004 TABLE 2 Approx. coating Vol. Area Coating thickness, Density.sup.1, Density.sup.2, Lambda, Damping Transmission Design. Coating Mass, g mm kg/m.sup.3 g/m.sup.2 W/m- K. Factor Loss, DB 6 Form. 1, 1410 15 326 5640 0.07 0.19 36.1 core-shell rubber 7 Form. 1, 1435 11 379 5720 0.07 0.16 34.6 barium sulfate 8 Form. 1, 2155 15 418 8620 0.07 0.20 37.8 barium sulfate 9 Form. 1, 2400 10 783 9600 0.07 0.15 37.5 recycled tires 10 Form. 1, 3150 20 514 12,600 0.07 0.23 39.8 recycled tires D* Form. 3, 2570 11 831 10,280 0.16 0.17 38.6 core-shell rubber E* Form. 3, 4160 10 1,204 16,640 0.16 0.26 39.8 barium sulfate F* Form. 3, 2850 11 843 11,400 0.16 0.17 37.7 recycled tires .sup.1Volume densities exclude the weight of the fillers. .sup.2Areal densities include filler weights.

(29) Examples 6-10 all provide excellent thermal and acoustic insulation. The additives in these cases have almost no effect on thermal insulation properties, but improve the acoustic properties compared to Examples 1-5. The acoustic properties of Examples 6-10 are comparable to Comparative Samples D, E and F. Comparative Examples D, E and F have poor thermal insulating properties.

(30) In Examples 11-17, the insulating system includes a first layer of viscoelastic foam (Formulation 1 or 2) and a second layer of a nearly compact polyurethane foam (Formulation 3). In making these Examples, the viscoelastic foam layer is applied and cured as before, and then Formulation 3 is sprayed atop the viscoelastic foam layer and cured to produce the final sample. Results from testing these Examples are as indicated in Table 3.

(31) TABLE-US-00005 TABLE 3 Approx. Approx. Visco- coating coating Applied Trans- Desig- elastic thickness, Compact thickness, Coating Lambda Damping mission nation Foam mm Layer mm Weight W/m- K. Factor Loss, DB 11 Form. 1 10 Form. 3 5 3270 0.07 0.21 39.5 12 Form. 1 10 Form. 3 5 3340 0.07 0.13 40.4 13 Form. 2 10 Form. 3 5 2460 0.07 0.16 38.5 14 Form. 2 15 Form. 3 5 2695 0.07 0.17 39.9 15 Form. 2 10 Form. 3 10 4170 0.07 0.20 40.8 16 Form. 1 10 Form. 3, 5 3520 0.07 0.13 40.6 BaSO.sub.4 17 Form 1 10 Form. 3, 5 3880 0.07 0.22 40.9 BaSO.sub.4

(32) Examples 11-17 show that even better acoustic properties can be obtained, without loss of thermal insulation properties, by applying a two-layer insulation system including a viscoelastic foam layer and a nearly compact polyurethane overcoat.

(33) Example 18

(34) Viscoelastic foam formulations 4, 5 and 6 are made by making small adjustments to foam formulation 2 to lower the volume density and, in the case of formulation 6, reduce the tensile modulus. Foams 4, 5 and 6 have the following properties:

(35) TABLE-US-00006 Property Foam 4 Foam 5 Foam 6 Volume Density, g/L (ASTM D3574) 213 107 116 Lambda, 20/40 C (mW/K*m) 53 41 40 Resiliency, % (ASTM D3574) 17 12 8 50% Compression Set (%) ASTM D3574 4.2 1.8 11.9 Tear Str., N/m, ASTM D3574 0.18 0.13 0.10 Elongation at Break, % ASTM D3575 127 102 129

(36) These foams have recovery times greater than 3 seconds as measured according to ASTM D3574-08 Test M.

(37) Each of foam formulations 4, 5 and 6 is separately applied to the drum and the door of a commercial household dishwasher, by applying the foam formulation directly on top of the external surface of the drum and door, respectively, and permitting the applied formulation to cure at room temperature and form a foam layer adhered to the underlying metal. In the case of foam formulation 4, the amount of foam applied is 11 kg. In the case of each of foam formulations 5 and 6, the amount of foam applied is 5.9-6.7 kg. The surface area covered by the foam is approximately 1.7 m.sup.2. Areal density for foam formulation 4 is 6470 g/m.sup.2, and 3470-3941 g/m.sup.2 for each of formulations 5 and 6. Average foam layer thickness is about 30.4 mm for foam formulation 4, 32.4-36.8 mm for foam formulation 5, and 29.9-34.0 mm for foam formulation 6. When operated, the dishwashers release significantly less noise than when untreated, and use less energy due to the reduced amount of heat lost through the drum and the door.