WO2008121419A1

WO2008121419A1 - Self-sealing coating, article and method of manufacture

Info

Publication number: WO2008121419A1
Application number: PCT/US2008/004250
Authority: WO
Original assignee: Defens Tech International Inc.
Priority date: 2007-03-30
Filing date: 2008-03-31
Publication date: 2008-10-09

Abstract

A self-sealing coating that provides leak mitigation to structures suffering puncture wounds and a self-sealing article are disclosed. The self-sealing coating includes at least one two-part polyurea elastomer applied to a surface of the structure. The self-sealing article includes at least one wall including the at least one two-part polyurea elastomer.

Description

SELF-SEALING COATING, ARTICLE AND METHOD OF MANUFACTURE

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of priority from U.S. Provisional

Patent Application Serial. No. 60/921238 filed on March 30, 2007 the entire disclosure of which is expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0002] The present invention generally relates to self-sealing coatings and articles and more particularly to a self-sealing polyurea elastomer coating and article for providing leak mitigation.

2. Description of Related Art

[0003] Self-sealing compositions, coatings and articles are well known in the art. For example U.S. Patent No. 5,011 ,726 discloses a self-sealing composition for roofing shingles. A pressure sensitive self-sealing composition for making pneumatic tires puncture resistant is disclosed in U.S. Patent No. 4,743,497. A self-sealing coating formed of liquid reaction substances that react with hydrocarbon fuel to imbibe the fuel and produce volume swelling of the imbibing material is disclosed in U.S. Patent No. 7,004,166. A self-sealing container comprising an elastomeric laminate having a sealant composition positioned in said laminate to effect sealing on contact with fuel is disclosed in U.S. Patent No. 3,801 ,425. Other related prior art includes U.S. Patent No. 3,506,224, U.S. Patent No. 3,563,846, U.S. Patent No. 3,577,314, U.S. Patent No. 3,664,904, U.S. Patent No. 3,787,279, and U.S. Patent No. 3,935,050. [0004] The use of self-sealing compositions and coatings finds particular applicability in the area of leak mitigation of structures suffering puncture wounds in which the structure is perforated or ruptured. Such structures include liquid containers such as fuel storage tanks, vehicle fuel tanks, fuel cells, fuel lines, and vehicle transfer cases. The liquid containers may be part of military vehicles such as tanks, helicopters, airplanes, drones, and Humvees. Puncture wounds may be inflicted by projectile intrusions including ballistic projectile intrusions.

SUMMARY OF THE INVENTION

[0005] The present application discloses a novel self-sealing coating that provides leak mitigation to structures suffering puncture wounds and a self-sealing article for containing a liquid.

[0006] In one aspect of the invention, the self-sealing coating includes at least one two-part polyurea elastomer applied to a surface of a liquid container to mitigate leakage from the liquid container following a puncture wound to the liquid container. [0007] In another aspect of the invention, the self-sealing coating includes a single layer of the polyurea elastomer applied to the surface of the liquid container. [0008] In another aspect of the invention, the self-sealing coating includes more than one layer of polyurea elastomer applied to the surface of the liquid container, successive layers being applied upon one another. [0009] In another aspect of the invention, the self-sealing coating includes a first layer of a first polyurea elastomer mechanically bonded to the surface of the liquid container and a second layer of a second polyurea elastomer mechanically bonded to the first layer. The fist layer insulates the second layer from elevated temperatures. [0010] In another aspect of the invention, the self-sealing coating includes a sandwich structure having a first layer of a first polyurea elastomer mechanically bonded to the surface of the liquid container, a second layer of a second polyurea elastomer mechanically bonded to the first layer, and a third layer of the first polyurea elastomer mechanically bonded to the second layer. [0011] In another aspect of the invention, the self-sealing coating is mechanically bonded to a primed surface of the liquid container.

[0012] In yet another aspect of the invention, a self-sealing article includes a vessel having walls formed from at least one two-part polyurea elastomer. [0013] In another aspect of the invention, the self-sealing article includes walls formed from a first layer of a first polyurea elastomer and a second layer of a second polyurea elastomer mechanically bonded to the first layer. [0014] In another aspect of the invention, the self-sealing article includes walls having a sandwich structure having a first layer of a first polyurea elastomer, a second layer of a second polyurea elastomer mechanically bonded to the first layer, and a third layer of the first polyurea elastomer mechanically bonded to the second layer. [0015] In another aspect of the invention, injection molding forms the self-sealing article.

[0016] In another aspect of the invention, the self-sealing article is formed by spraying the at least one two-part polyurea elastomer onto a mold. [0017] There has been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended herein. [0018] In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of components and to the arrangements of these components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. [0019] As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other coatings and articles for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent coatings and articles insofar as they do not depart from the spirit and scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] These and other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures, wherein:

[0021] FIG. 1 is a perspective view of a vehicle having a fuel tank coated with a self-sealing coating in accordance with the invention;

[0022] FIG. 2 is a cross sectional view of the fuel tank of FIG. 1 showing a first embodiment of the self-sealing coating in accordance with the invention;

[0023] FIG. 2A is a cross sectional view of the fuel tank of FIG. 2 showing a second embodiment of the self-sealing coating in accordance with the invention;

[0024] FIG. 3 is a cross sectional view of the fuel tank of FIG. 1 showing a third embodiment of the self-sealing coating in accordance with the invention; [0025] FIG. 4 is a cross sectional view of the fuel tank of FIG. 1 showing a fourth embodiment of the self-sealing coating in accordance with the invention;

[0026] FIG. 5 is a fragmentary view of the fuel tank of FIG. 1 showing a perforating puncture wound and the self-sealing coating in accordance with the invention; [0027] FIG.6 is a cross sectional view of the fuel tank showing the perforating puncture wound and the self-sealing coating in accordance with the invention; and

[0028] FIG. 7 is a perspective view of a self-sealing article in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and examples below are not meant to limit the scope of the present invention. Where certain elements of the present invention can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention. Further, the present invention encompasses present and future known equivalents to the components referred to herein by way of illustration.

[0030] The present invention provides a self-sealing coating that provides leak mitigation to liquid containers suffering puncture wounds. Depending upon the composition of the self-sealing coating and the thickness thereof, leak mitigation may be complete or sufficient to provide enough time for the vehicle to drive to safety. [0031] In addition to providing leak mitigation, the self-sealing coating provides a protective, waterproof coating to the liquid container. The self-sealing coating also prevents corrosion of the walls of the liquid container. The self-sealing coating further provides an abrasion resistant and chemical resistant coating to the walls of the liquid container.

[0032] With reference to FIG. 1 , a vehicle 100 includes a fuel tank 110. The fuel tank 110 is shown disposed in an exposed position for illustration purposes only and would normally be protected from exposure. [0033] The fuel tank 110 includes a self-sealing coating 120 on an outside surface 115 of a substrate or wall 113 thereof. In a first embodiment of the invention and with reference to FIG. 2, the self-sealing coating 120 includes a single layer 200 of a two-part polyurea elastomer mechanically bonded to the outside surface 115 of the fuel tank wall 113. The two-part polyurea elastomer comprises the product sold under the name Defends-X, DTLS-75 (DTLS-75) available from DefensTech International Inc. of Huntington Beach, CA. DTLS-75 has the following properties and characteristics:

[0034] The two components may be brought together under pressure using a heated spray gun and sprayed on the outside surface 115 to form the self-sealing coating 120. Alternatively, the two components may be brushed or rolled on the outside surface 115. Additionally, the outside surface 115 may be coated by immersion. Once fully cured, the self-sealing coating 120 provides toughness, flexibility, high impact and tear resistance along with chemical and water resistance.

[0035] The self-sealing coating 120 of the first embodiment preferably has a thickness of between 125 and 500 mils (thousands of an inch). Experimental results show that the sealing capability of the self-sealing coating 120 is directly proportional to the thickness thereof. A thinner coating exhibits larger leak rates than thicker coatings. A leak rate of near zero is achievable with the self-sealing coating 120 of the first embodiment having a thickness of 240 mil when challenged using a 12.7mm API round leaded to 2500 feet per second. The self-sealing or healing process of the self-sealing coating 120 of the first embodiment occurs in a timeframe on the order of milliseconds under ambient conditions.

[0036] To improve the adhesion of the layer 200 to the outside surface 115 of the wall 113 and to prevent delamination of the self-sealing coating 120, the outside surface 115 is preferably sanded and primed. A 2-4 mil profile is preferable. The primer may include the product sold as Futura-Bond 610HS and available from ITW Futura Coatings of St. Louis, Mo. In accordance with a second embodiment of the invention, a layer of primer 200a is shown disposed between the outside surface 115 and the layer 200 of polyurea elastomer in FIG. 2A wherein the relative thickness of the layer of primer 200a has been exaggerated for illustration purposes only. [0037] A third embodiment of the invention is shown in FIG. 3. The self-sealing coating 120 includes a first layer 300 of a first two-part polyurea elastomer mechanically bonded to the outside surface 115 of the wall 113 and a second layer 310 of a second two-part polyurea elastomer mechanically bonded to the first layer 300. Preferably the first layer 300 has a thickness between 20 and 125 mils and the second layer 310 has a thickness between 125 and 500 mils. The first layer 300 insulates the second layer 310 from elevated temperatures present in the fuel tank 110. The first two-part polyurea elastomer comprises the product sold under the name Defends-X, DTLS-223 (DTLS- 223) available from DefensTech International Inc. DTLS-223 has the following properties and characteristics:

[0038] The two components of the DTLS-223 may be brought together under pressure using a heated spray gun and sprayed on the outside surface 115 to form the first layer 300. Alternatively, the two components may be brushed or rolled on the outside surface 115. Additionally, the outside surface 115 may be coated by immersion. [0039] The second two-part polyurea elastomer comprises DTLS-75. The two components of the DTLS-75 are applied to the first layer 300 to form the second layer 310. The two components of the DTLS-75 may be brought together under pressure using a heated spray gun and sprayed on the first layer 300 to form the second layer 310. Alternatively, the two components may be brushed or rolled on the first layer 300. Additionally, the first layer may be coated by immersion. The second layer 310 is mechanically bonded to the first layer 300. [0040] As in the case of the first embodiment, experimental results show that the sealing or healing capability of the self-sealing coating 120 of the second embodiment is directly proportional to the thickness thereof. A thinner coating exhibits larger leak rates than thicker coatings. While a near zero leak rate is achievable with a thicker coating, the increased weight of the thicker coating must be taken into account and acceptable leak rates evaluated. As in the case of the self-sealing coating 120 of the first embodiment, the self-sealing or healing process of the self-sealing coating 120 of the second embodiment occurs in a timeframe on the order of milliseconds under ambient conditions.

[0041] As between the two layers 300 and 310, the second layer 310 of DTLS-75 exhibits better self-sealing or healing properties than the first layer 300 of DTLS-223. While the stiffer DTLS-223 exhibits self-sealing, the softer DTLS-75 is more effective in closing a puncture wound and mitigating leakage. Advantageously though, the first layer 300 of DTLS-223 insulates the second layer 310 from elevated temperatures present in the fuel tank 110 to improve the performance of the second layer 310. [0042] A fourth embodiment of the invention is shown in FIG. 4. The self-sealing coating 120 includes a sandwich structure having a first layer 400 of a first two-part polyurea elastomer mechanically bonded to the outside surface 115 of the fuel tank wall 113, a second layer 410 of a second two-part polyurea elastomer mechanically bonded to the first layer 400, and a third layer 420 of the first two-part polyurea elastomer bonded to the second layer 410. Preferably the first layer 400 has a thickness between 125 and 500 mils, the second layer 410 has a thickness between 20 and 125 mils, and the third layer 420 has a thickness between 125 and 500 mils. The first two-part polyurea elastomer comprises DTLS-75 and the second two-part polyurea elastomer comprises DTLS-223.

[0043] The first layer 400 may be applied to the outside surface 115 of the fuel tank wall 113 by any of the methods previously described for the application of two-part polyurea elastomers. The second layer 410 is applied to the first layer 400 to form a mechanical bond therebetween. Finally the third layer 420 is applied to the second layer 410 to form a mechanical bond therebetween.

[0044] As in the case of the previously described embodiments, experimental results show that the sealing or healing capability of the self-sealing coating 120 of the fourth embodiment is directly proportional to the thickness thereof. A thinner coating exhibits larger leak rates than thicker coatings. While a near zero leak rate is achievable with a thicker coating, the increased weight of the thicker coating must be taken into account and acceptable leak rates evaluated. As in the case of the self- sealing coating 120 of the previously described embodiment, the self-sealing or healing process of the self-sealing coating 120 of the fourth embodiment occurs in a timeframe on the order of milliseconds under ambient conditions. [0045] With reference to FIG. 5 and to FIG. 6, a perforating puncture wound 500 is shown formed through the wall 113 of the fuel tank 110. A wound 510 formed in the self-sealing coating 120 is shown in a sealed configuration. As previously noted, the degree of leak mitigation is dependant upon several factors including the thickness of the self-sealing coating 120, the softness of the polyurea elastomer forming the self- sealing coating 120, and temperature and pressure conditions within the fuel tank 110. [0046] A fifth embodiment of the invention is shown in FIG. 7 and includes a self- sealing article 700 having at least one self-sealing wall formed from at least one two- part polyurea elastomer. The self-sealing article 700 is shown as a liquid containing vessel or tank 710. The self-sealing vessel 710 may include walls 720 formed from a single layer of polyurea elastomer (e.g., DTLS-75) or from a first layer of a first polyurea elastomer (e.g., DTLS-223) and a second layer of a second polyurea elastomer (e.g., DTLS-75) mechanically bonded to the first layer. The walls 720 may alternately have a sandwich structure having a first layer of a first polyurea elastomer (e.g., DTLS-75), a second layer of a second polyurea elastomer (e.g., DTLS-223) mechanically bonded to the first layer, and a third layer of the first polyurea elastomer mechanically bonded to the second layer. The walls 720 may be formed by conventional methods including molding and injection molding and have thicknesses in the range described above with regard to the self-sealing coatings 120. [0047] While the embodiments of the invention have been described in terms of preferred two-part polyurea elastomers, other two-part elastomers having equivalent properties may be used. For example, Defend-X, DTLS-45 (having an elongation of 760%) may be substituted for DTLS-75 and Defend-X, DTLS-40 (having an elongation of 220%) may be substituted for DTLS-223. Furthermore, the substrate surfaces to which any of the described self-sealing coatings are applied may be prepared to increase adhesion thereto as described with reference to the second embodiment of the invention. [0048] The self-sealing coating in accordance with the invention provides leak mitigation to liquid tanks to which it is applied. Depending upon the thickness of the self-sealing coating applied, near zero leak rates are achievable in a cost-effective manner. [0049] The self-sealing article in accordance with the invention provides a liquid vessel or tank having self-sealing walls providing leak mitigation. [0050] It is apparent that the above embodiments may be altered in many ways without departing from the scope of the invention. Further, various aspects of a particular embodiment may contain patentably subject matter without regard to other aspects of the same embodiment. Still further, various aspects of different embodiments can be combined together. Accordingly, the scope of the invention should be determined by the following claims and their legal equivalents.

Claims

What is claimed is: 1. A self-sealing coating for application to a surface of a substrate comprising: a layer of a two-part polyurea elastomer mechanically bonded to the surface of the substrate.

2. The self-sealing coating of claim 1 , wherein the layer has a thickness between 125 and 1000 mils.

3. The self-sealing coating of claim 1 , wherein the layer has a thickness of 240 mils.

4. A self-sealing coating for application to a prepared surface of a substrate comprising: a layer of a two-part polyurea elastomer mechanically bonded to the prepared surface of the substrate.

5. The self-sealing coating of claim 4, wherein the prepared surface comprises a sanded and primed surface.

6. The self-sealing coating of claim 4, wherein the layer has a thickness between 125 and 1000 mils.

7. The self-sealing coating of claim 4, wherein the layer has a thickness of 240 mils.

8. A self-sealing coating for application to a surface of a substrate comprising: a first layer of a first two-part polyurea elastomer mechanically bonded to the surface of the substrate; and a second layer of a second two-part polyurea elastomer mechanically bonded to the first layer.

9. The self-sealing coating of claim 8, wherein the first layer has a thickness between 20 and 125 mils and the second layer has a thickness between 125 and 500 mils.

10. The self-sealing coating of claim 8, wherein the first two-part polyurea elastomer has a lower elongation than the second two-part polyurea elastomer.

11. A self-sealing coating for application to a prepared surface of a substrate comprising: a first layer of a first two-part polyurea elastomer mechanically bonded to the prepared surface of the substrate; and a second layer of a second two-part polyurea elastomer mechanically bonded to the first layer.

12. The self-sealing coating of claim 11 , wherein the prepared surface comprises a sanded and primed surface.

13. The self-sealing coating of claim 11 , wherein the first layer has a thickness between 20 and 125 mils and the second layer has a thickness between 125 and 500 mils.

14. The self-sealing coating of claim 11 , wherein the first two-part polyurea elastomer has a lower elongation than the second two-part polyurea elastomer.

15. A self-sealing coating for application to a surface of a substrate comprising: a first layer of a first two-part polyurea elastomer mechanically bonded to the surface of the substrate; a second layer of a second two-part polyurea elastomer mechanically bonded to the first layer; and a third layer of the first two-part polyurea elastomer mechanically bonded to the second layer.

16. The self-sealing coating of claim 15, wherein the first layer has a thickness between 125 and 500 mils, the second layer has a thickness between 20 and 125 mils, and the third layer has a thickness between 125 and 500 mils.

17. The self-sealing coating of claim 15, wherein the first two-part polyurea elastomer has a greater elongation than the second two-part polyurea elastomer.

18. The lead frame-based discrete power inductor of claim 14, wherein the leads of the top lead frame first and second set of leads are planar, and the leads of the bottom lead frame first and second set of leads are planar.

19. A self-sealing coating for application to a prepared surface of a substrate comprising: a first layer of a first two-part polyurea elastomer mechanically bonded to the surface of the substrate; a second layer of a second two-part polyurea elastomer mechanically bonded to the first layer; and a third layer of the first two-part polyurea elastomer mechanically bonded to the second layer.

20. The self-sealing coating of claim 19, wherein the prepared surface comprises a sanded and primed surface.

21. The self-sealing coating of claim 19, wherein the first layer has a thickness between 125 and 500 mils, the second layer has a thickness between 20 and 125 mils, and the third layer has a thickness between 125 and 500 mils.

22. The self-sealing coating of claim 19, wherein the first two-part polyurea elastomer has a greater elongation than the second two-part polyurea elastomer.

23. A self-sealing article comprising: at least one wall including a layer of a two-part polyurea elastomer.

24. The self-sealing article of claim 23, wherein the article is a liquid tank.

25. A self-sealing article comprising: at least one wall including a first layer of a first two-part polyurea elastomer; and a second layer of a second two-part polyurea elastomer mechanically bonded to the first layer.

26. The self-sealing article of claim 25, wherein the article is a liquid tank.

27. A self-sealing article comprising: at least one wall including a first layer of a first two-part polyurea elastomer; a second layer of a second two-part polyurea elastomer mechanically bonded to the first layer; and a third layer of the first two-part polyurea elastomer mechanically bonded to the second layer.

28. The self-sealing article of claim 27, wherein the article is a liquid tank.