Abstract:
A device for retaining a fluid is disclosed. The device includes a fuel tank having a multi-layer structure including an inner layer having a first surface that defines a cavity of the fuel tank, an outer layer having a second surface that defines a contour of the fuel tank, and a gas that is exposed to one or more of the first and second surfaces to define a fuel permeation barrier of the fuel tank. The gas seeps into one or more of the first and second surfaces to define the fuel permeation barrier having a depth. A method is also disclosed.

Description:
RELATED APPLICATION 
       [0001]    This disclosure claims the benefit of Provisional Patent Application No. 60/813,319, filed on Jun. 13, 2006. 
     
     FIELD OF THE INVENTION 
       [0002]    The disclosure relates to fuel tanks and to sulfonated fuel tanks. 
       DESCRIPTION OF THE RELATED ART 
       [0003]    It is known in the art that vehicles may include a fuel tank that stores fuel. It is known in the art that fuel tanks may comprise plastic. Plastic fuel tanks, however, may have several drawbacks. One drawback may include, for example, the emission of hydrocarbons into the atmosphere. Accordingly, there is a need in the art to reduce or eliminate the emission of hydrocarbons from a plastic fuel tank that stores fuel. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The disclosure will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0005]      FIG. 1  is a perspective view of a fuel tank in accordance with an exemplary embodiment of the invention 
           [0006]      FIG. 2  is a partial cross-sectional view of the fuel tank according to line  2 - 2  of  FIG. 1  in accordance with an exemplary embodiment of the invention; 
           [0007]      FIG. 3  is another partial cross-sectional view of the fuel tank in accordance with an exemplary embodiment of the invention; 
           [0008]      FIGS. 4A-4C  each illustrate a method for sulfonating a fuel tank in accordance with an exemplary embodiment of the invention; 
           [0009]      FIG. 5  is a partial cross-sectional electron microscope atomic scan image of the fuel tank according to  FIG. 2  in accordance with an exemplary embodiment of the invention; and 
           [0010]      FIG. 6  is an enlarged view of  FIG. 3  according to line  6 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    The Figures illustrate an exemplary embodiment of a sulfonated fuel tank in accordance with an embodiment of the invention. Based on the foregoing, it is to be generally understood that the nomenclature used herein is simply for convenience and the terms used to describe the invention should be given the broadest meaning by one of ordinary skill in the art. 
         [0012]    Referring to  FIG. 1 , a fuel tank is shown generally at  10  according to an embodiment. In an embodiment, the fuel tank  10  comprises plastic. The fuel tank  10  may include any desirable plastic material, such as, for example, high density polyethylene (HDPE). By utilizing plastic in the manufacture of the fuel tank  10 , an overall weight reduction for a vehicle (not shown) may be achieved, which results in a more efficient operation of the vehicle. 
         [0013]    Referring to  FIG. 2 , the fuel tank  10  may be defined to include a multi-layer structure  12  that defines a fuel tank volume or cavity, C, relative to atmosphere, A. The multi-layer structure  12  is defined to include an inner layer  14 , an outer layer  16 , and, if desired, any amount of intermediate layers  18   a - 18   d.    
         [0014]    According to an embodiment, the inner layer  14  may comprise virgin HDPE. According to an embodiment, the virgin HDPE inner layer  14  may define approximately 40% (±10%) of the overall thickness of the multi-layer structure  12 . 
         [0015]    According to an embodiment, the outer layer  16  may comprise virgin HDPE. If desired, the outer layer  16  may also include a dye/colorant to provide any desirable pigmentation. If desired, the outer layer  16  may also include an additive for ultraviolet protection. According to an embodiment and without limitation, an exemplar dye/colorant with ultraviolet protection is commercially available and sold under the trade-name POLYBLACK®. According to an embodiment, the virgin HDPE outer layer  16  may define approximately 16% (±10%) of the overall thickness of the multi-layer structure  12 . 
         [0016]    According to an embodiment, the intermediate layer  18   a  may comprise recycled material. The recycled material of the intermediate layer  18   a  may be recovered from a grinder. Accordingly, the recycled material recovered from a grinder that comprises the intermediate layers  18   a  may be referred to hereinafter as regrind layer  18   a . If desired, the regrind layer  18   a  may be melted and extruded, injected, or otherwise formed with the inner and outer layers  14 ,  16 . 
         [0017]    According to an embodiment, the regrind layer  18   a  may include recycled HDPE. In an embodiment, the regrind layer  18   a  may include a plurality or mixture of recycled materials. According to an embodiment and without limitation, the regrind layer  18   a  may include one or more of the materials identified in the multilayer structure  12  as discussed in this disclosure. According to an embodiment, the intermediate regrind layer  18   a  may define approximately 38% (±10%) of the overall thickness of the multi-layer structure  12 . By including the regrind layer  18   a , the overall cost of the fuel tank  10  may be reduced by utilizing recycled materials. 
         [0018]    According to an embodiment, the intermediate layers  18   b  and  18   d  may comprise an adhesive. According to an embodiment, the intermediate adhesive layers  18   b ,  18   d  may include linear low density polyethylene (LLDPE). According to an embodiment, the LLDPE adhesive layers  18   b ,  18   d  may be co-extruded between approximately 200° C. and 230° C. through, for example, a spiral die. 
         [0019]    Once the adhesive layers  18   b ,  18   d  have cooled, the LLDPE adhesive layers  18   b ,  18   d  thermally bond the HDPE inner layer  14 , regrind layer  18   a , and intermediate layer  18   c . According to an embodiment and without limitation, an exemplar LLDPE adhesive layer  18   b ,  18   d  is sold under the trade-name ADMER®. According to an embodiment, the intermediate adhesive layers  18   b ,  18   d  may each define approximately 3% (±2%) of the overall thickness of the multi-layer structure  12 . 
         [0020]    According to an embodiment, the intermediate layer  18   c , which is shown disposed between the adhesive layers  18   b ,  18   d , may comprise a barrier layer of ethylene vinyl alcohol polymer (EVOH). The EVOH barrier layer  18   c  limits fuel emissions and functions as an internal hydrocarbon barrier layer. According to an embodiment, the intermediate EVOH barrier layer  18   c  may define approximately 3% (±2%) of the overall thickness of the multi-layer structure  12 . Although the illustrated embodiment shown at  FIG. 2  includes the regrind layer  18   a , intermediate EVOH layer  18   c  and adhesive layers  18   b ,  18   d , it will be appreciated that the fuel tank  10  is not limited or required to include the layers  18   a - 18   d  and that the fuel tank  10  may include the inner and outer layers  14 ,  16 . 
         [0021]    According to an embodiment, a surface  20  of the inner layer  14  generally defines an inner surface/geometry (i.e. the cavity, C) of the fuel tank  10  for storing a fluid, F, such as, for example, fuel (e.g. gasoline). According to an embodiment, a surface  22  of the outer layer  16  generally defines the outer surface/geometry of the fuel tank  10  that is exposed to atmosphere, A. 
         [0022]    Referring to  FIG. 3 , the one or more layers  14 - 18   d  of the multi-layer structure  12  may be defined to include several pinched portions  24 , which may be referred to in the art as “pinch areas.” Pinch portions  24  may be found about the surfaces  20 ,  22  as a result of a forming/molding operation or the like. The cross-section of a pinched portion  24  may be defined by an irregularity in the contour or thickness of the fuel tank  10  as compared to a portion of the multi-layer structure  12  that does not include a pinched portion  24  (i.e., as shown in  FIG. 2 ). In addition, as described in greater detail below, the cross-section of the fuel tank  10 , as defined by pinched portions  24 , may also further define a reduced thickness or absence of any one of the intermediate layers  18   a - 18   d , such as, for example, the EVOH barrier layer  18   c  (see, e.g.,  FIG. 6 ). 
         [0023]    Referring to  FIG. 1 , the fuel tank  10  may also include one or more components  26 . The one or more components  26  may be formed integrally with the multi-layer structure  12 , or, alternatively, be connected to the fuel tank  10  by way of any desirable fastening methodology, such as, for example, welding. If formed integrally or connected to the fuel tank  10 , the one or more components  26  may be defined by a multi-layer structure substantially similar to the multi-layer structure  12  of the fuel tank  10 . Functionally, the one or more components  26  may include, for example, a connector, nozzle, or the like that provides fluid communication with, for example, a valve, pump, or the like (not shown). 
         [0024]    According to an embodiment, one or more of the layers  14 - 18   d  of the multi-layer structure  12 , which may include, for example, the one or more components  26 , may be defined to include a fuel permeation barrier (see, e.g.,  FIG. 5 ) that prevents the fluid, F, in the cavity, C, as well as vapors (e.g. hydrocarbon vapors, H) associated with the fluid, F, in the cavity, C, from escaping from the fuel tank  10  and into atmosphere, A. According to an embodiment, the fuel permeation barrier improves the fluid barrier properties of the fuel tank  10 . 
         [0025]    Referring to  FIGS. 4A-4C , according to an embodiment, the fuel permeation barrier is provided by sulfonating the fuel tank  10  with a gas, G. According to an embodiment, the gas, G, may include sulfur trioxide (SO 3 ). 
         [0026]    According to an embodiment, a portion, some, or all of the layers  14 - 18   d  of the multi-layer structure  12  of the fuel tank  10  is sulfonated by exposing at least a portion of the fuel tank  10  to the SO 3  gas, G. According to an embodiment, depending on the geometry, structure, and configuration of the fuel tank  10 , the multi-layer structure  12  may be sulfonated for approximately 90-minutes to achieve a desired permeation of the gas, G, into the multi-layer structure  12 . 
         [0027]    Referring to  FIG. 4A , the fuel tank  10  may be placed in an enclosed chamber  100  that is in fluid communication with a supply  104  of SO 3  gas, G, by way of a conduit  102 . Prior to being placed in the chamber  100 , the fuel tank  10  may be sealed such that SO 3  gas, G, may not enter the cavity, C. Thus, according to an embodiment, the surface  22  of HDPE outer layer  16  of the fuel tank  10  may be sulfonated with the SO 3  gas, G, while the fuel tank  10  is placed in the chamber  100 . 
         [0028]    Alternatively, referring to  FIG. 4B , the cavity, C, of the fuel tank  10  may be in fluid communication with the supply  104  of SO 3  gas, G, by way of the conduit  102 . The cavity, C, may be sealed such that the exposure of the SO 3  gas, G, to the fuel tank  10  is limited to the surface  20  of HDPE inner layer  14 . 
         [0029]    Alternatively, referring to  FIG. 4C , the fuel tank  10  may be placed in the chamber  100  such that SO 3  gas, G, is provided from the supply  104  for exposure to both of the surfaces  20 ,  22  of the fuel tank  10  as shown and described in  FIGS. 4A and 4B . Accordingly, both the inner and outer HDPE layers  14 ,  16  may be sulfonated with the SO 3  gas, G. Although the fuel tank  10  is shown having both of its surfaces  20 ,  22  being sulfonated simultaneously, it will be appreciated that the surfaces  20 ,  22  may be sulfonated individually as shown and described in  FIGS. 4A and 4B . 
         [0030]    Referring to  FIG. 5 , a cross-sectional electron microscope atomic scan image of a permeation barrier is shown according to an embodiment. According to an embodiment, the HDPE inner layer  14  is illustrated as a layer of the multi-layer structure  12  that is sulfonated with the SO 3  gas, G (i.e., as shown in  FIG. 4B ). However, the scanned image of  FIG. 5  is not limited to the HDPE inner layer  14 , and, as such, it will be appreciated that other layers, such as, for example, the HDPE outer layer  16  may be sulfonated with the SO 3  gas, G (i.e., as shown in  FIG. 4A ), and define a substantially similar image as that shown in  FIG. 5  as related to the HDPE inner layer  14 . 
         [0031]    According to an embodiment, the SO 3  gas, G, may be quantified by seeping into the HDPE inner and/or outer layer(s)  14 ,  16  through the surface(s)  20 ,  22  to a depth, D. The depth, D, generally defines the fuel permeation barrier that prevents, for example, hydrocarbons, H, associated with fuel, F, stored in the cavity, C, from escaping into atmosphere, A. The depth, D, may range between approximately, for example, 25-50 microns. Although the SO 3  gas, G, is described to permeate the inner and outer layers  14 ,  16 , at a depth, D, it will be appreciated that the thickness of the layers  14 - 18   d  may be increased or decreased to limit or otherwise promote the permeation of the SO 3  gas, G, to one of, some, or all of the layers  14 - 18   d  of the fuel tank  10 . 
         [0032]    Referring back to  FIGS. 2 and 3 , it will be appreciated that although the inner and/or outer layer(s)  14 ,  16  are sulfonated with the SO 3  gas, the EVOH barrier layer  18   c  may also function in a substantially similar manner as the sulfonated HDPE inner and/or outer layer(s)  14 ,  16  by preventing hydrocarbons, H, stored in the cavity, C, from escaping into atmosphere, A. As such, referring to  FIG. 2 , if, for example, escaping hydrocarbons, H, are not blocked or prevented by the inner layer  14  from escaping to atmosphere, A, one or more of the EVOH barrier layer  18   c  and sulfonated outer later  16  may serve to supplement the hydrocarbon-blocking properties of the inner layer  14 . 
         [0033]    Referring to  FIGS. 3 and 6 , when the fuel tank  10  is formed to include pinched portions  24 , a pinched zone  25  may define a reduced thickness, or, alternatively, an absence of the thickness of the EVOH barrier layer  18   c . According to an embodiment, if, for example, the pinched zone  25  includes a reduced thickness/absence of the EVOH barrier layer  18   c , and, if for example, the HDPE inner layer  14  is not sulfonated as described in  FIG. 2 , hydrocarbons, H, that may otherwise escape toward atmosphere, A, through the HDPE inner layer  14  and pinched zone  25  may be otherwise prevented from escaping into atmosphere, A, by the outer layer  16 , as shown in  FIG. 3 . Thus, the sulfonating of the outer layer  16  may serve to supplement the hydrocarbon-blocking properties of one or more of the inner layer  14  and/or the barrier layer  18   c.    
         [0034]    The present invention has been described with reference to certain exemplary embodiments thereof. However, it will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the exemplary embodiments described above. This may be done without departing from the spirit of the invention. The exemplary embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is defined by the appended claims and their equivalents, rather than by the preceding description.