Abstract:
The present invention relates packaging webs having at least one surface comprising a product-release coating composition which is capable of easily separating from a food product without tearing the web or changing the appearance of the food product, where the product-release coating composition includes a compound of the following formula (I):

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to packaging material and more particularly relates to packaging materials for use in packaging foods, with improved release properties. 
         [0002]    It is desirable to wrap certain foods in a packaging material prior to distribution. However, various types of foods tend to be hydroscopic in nature, for example some types of candy, chocolates, or baked goods, such as nutrition or breakfast bars, and stick or cling to the packaging material when the consumer attempts to remove the packaging material prior to consumption due to moisture absorption by the food. Such sticking or clinging is undesirable in that it may lead to food wastage or tearing of the packaging material. 
         [0003]    Various materials have been used on the interior surface of packaging materials to prevent blocking. Blocking is defined as undesired adhesion between touching layers of a packaging material such as occurs under moderate pressure conditions which occur during storing or wrapping operations. For example, it is known to provide a thin coating of dry granular starch on the packaging material. Such coating of dry granular starch, however, is not satisfactory in effecting release of the packaging material from the food product that is wrapped therein. 
         [0004]    Accordingly, it is an object of the present invention to provide an improved packaging material. It is another object of the present invention to provide a packaging material with improved release properties when used for food products. It is further object of the present invention to provide a coating which provides easy release of the packaging material from the food products at the time of consuming. 
         [0005]    These and other objects of the present invention will become more clear from the following detailed disclosure. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is directed to packaging webs having at least one surface comprising a product-release coating composition which is capable of easily separating from a food product without tearing the web or changing the appearance of the food product, where the product-release coating composition includes a compound of the following formula (I): 
         [0000]    
       
                 
         
             
             
         
       
     
         [0007]    wherein R 1  and R 2  are each independently a straight, branched or cyclic alkyl group having from 1 to 13 carbon atoms, and X +  is a metal cation selected from Al, Ca, Mg, K or Na. 
         [0008]    Another embodiment of the present invention is directed to a packaging web which will inhibit moisture loss or absorption by the food product contained therein which includes at least one surface having a product-release coating composition comprising a compound of the above Formula (I) 
         [0009]    A further embodiment of the present invention is directed to a packaging web having a controlled product release strength provided by a printable product-release coating composition comprising a compound of the above Formula (I). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which: 
           [0011]      FIG. 1  illustrates a schematic view of one embodiment of a packaging web according to the present invention. 
           [0012]      FIG. 2  illustrates a schematic view of another embodiment of a packaging web according to the present invention, 
           [0013]      FIG. 3  illustrates a transverse cross-sectional view of one embodiment of a packaging web illustrated in  FIG. 1 , taken through section A-A of  FIG. 1   
           [0014]      FIG. 4  illustrates a schematic view of another embodiment of a packaging web according to the present invention. 
           [0015]      FIG. 5  illustrates a transverse cross-sectional view of one embodiment of a packaging web illustrated in  FIG. 4 , taken through section B-B of  FIG. 4 . 
           [0016]      FIG. 6  illustrates a transverse cross-sectional view of another embodiment of a packaging web illustrated in  FIG. 4 , taken through section B-B of  FIG. 4 . 
           [0017]      FIG. 7  illustrates a schematic view of another embodiment of a packaging web according to the present invention. 
           [0018]      FIG. 8  illustrates a transverse cross-sectional view of another embodiment of a packaging web illustrated in  FIG. 7 , taken through section C-C of  FIG. 7 . 
           [0019]      FIG. 9  illustrates a package formed from a packaging web according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The product-release coating composition of the present invention includes a compound of the following formula (I): 
         [0000]    
       
                 
         
             
             
         
       
     
         [0021]    wherein the compound illustrated above is a sulfosuccinate that includes R 1  and R 2  groups which are each independently a straight, branched or cyclic alkyl group having from 1 to 13 carbon atoms, and X +  is a metal cation selected from Al, Ca, Mg, K or Na The R 1  and R 2  can be the same or different. Preferably. however; R 1  and R 2  will be the same. Preferably, R 1  and R 2  groups include isobutyl, pentyl (amyl), cyclohexyl, octyl and tridecyl. In a preferred embodiment of the present invention, X +  is Na Preferably, the product-release coating composition includes at least one sulfosuccinate sodium salt of the following formulae (II)-(VI). 
         [0000]    
       
                 
         
             
             
         
       
     
         [0022]    The chemical name of the compound of formula (II) is sodium diisobutyl suifosuccinate formula (III) is sodium d pentyl suifosuccinate or sodium dianyi sulfosuccinate; formula (IV) is sodium dicyclohexyl sulfosuccinate; formula (V) is sodium dioctyl sulfosuccinate; and formula (VI) is sodium ditridecyl sulfosuccinate. A non-limiting example of a commercially available product-release coating composition of formula (V) is INXClear anti-fog 1309444 supplied by INX International Ink Company (Appleton, Wis., U.S.A.). In a preferred embodiment, the product-release composition is a mixture of a 7% (wt.) INXClear anti fog 1309444 and 93% (wt) ethanol. After applying the product-release composition to the packaging web, it is dried to remove any residual solvent. Other commercially available sulfosuccinate compounds contemplated for use in the present invention include those sold under the trademark TRITON™ supplied by the Dow Chemical Company (Midland, Mich., U.S.A,), Nekal Wt-27 supplied by Phenomenex Inc. (Torrance, Calif., U.S.A.); AEROSOL TR, OT, GPG and PG families of surfactants supplied by Cytec Industries (Woodland Park, N.J., U.S.A.); and those sold under the trademark ASTROWET® supplied by Arkem Speciality Polymers (Kwazulu Natal, South Africa). 
         [0023]    In accordance with the practice of the present invention, a representative packaging web as described herein is shown in  FIG. 1 . Packaging web  10  comprises a first side edge  11  and an opposing second side edge  12 , a third side edge  13  and opposing fourth side edge  14 , and an inner surface  21  and an outer opposing surface  22  (not shown). Web  10  also includes a sealing border  30  positioned adjacent to the first, second, third and fourth side edges which comprises a cold-seal adhesive coating  40  and a product-release coating  50  applied in an area  60  circumscribed by the sealing border  30  In a preferred embodiment, product-release coating  50  is present on the inner surface  21  of web  10  in an amount of between 0.02 lb/ream and 0.50 lb/ream (9 gram/ream and 227 gram/ream), It should be understood that the range of amounts of product-release coating  50  present on the inner surface  21  represents its dried weight (or % solids after deposition and drying). 
         [0024]    Inner surface  21  of web  10  may be formed from any substrate which includes, but is not limited to, mono-layer or multilayer thermoplastic films which will be described in more detail below. Cold-seal adhesives are an established class of commercial adhesives characterized by being coated onto plastic films or other substrates to form layers that have the capability of strongly bonding to themselves when pressure is applied, but lacking adhesion to low energy surfaces, e.g., plastic films, coated papers, etc. In some cases, such flexible webs bearing these cold-seal adhesives layers may be formed into rolls without significant blocking, i.e., without sticking together. Cold-seal adhesives are based on mixtures of natural and/or synthetic rubber and are well known in the art. These mixtures can be water and/or solvent based rubber compositions. Preferably, cold-seal adhesive coating  40  and a product-release coating  50  are each applied to inner surface  21  of web  10  by standard printing methods known in the art, including flexographic and rotogravure printing techniques. In a preferred embodiment, cold-seal adhesive coating  40  is printed on inner surface  21  of web  10  in registration with product-release coating  50  and graphics printed on opposing surface  22  in a succession printing operations. Non-limiting examples of suitable cold-seal adhesive coatings include COSEAL™ 30080M which is a water based emulsion adhesive formulation supplied by Rohm and Haas Company (Elgin, Ill., U.S.A.); LIOFOL CS® 22-861US1 which is a water based natural rubber latex adhesive supplied by Henkel Corporation (Buffalo, N.Y. U.S.A.); and TURBO-SEAL® C2978B and C7222 adhesives both supplied by Bostik, Inc, (Wauwatosa, Wis., U.S.A.), 
         [0025]    Sealing border  30  may be printed as a contiguous or non-contiguous strip of cold-seal adhesive coating  40  extending around the periphery of web  10   FIG. 1  depicts one embodiment comprising a sealing border  30  having a contiguous strip of cold-seal adhesive coating  40 . The width of a contiguous strip of cold-seal adhesive coating  40  may vary depending upon the size and shape of the product. In one preferred embodiment, the contiguous strip of cold-seal adhesive coating  40  has a width of between 0.5 in and 0.63 in (12.7 mm and 15.88 mm). Although web  10  is depicted as having a rectangle shape in  FIGS. 1, 2, 4, and 7 , it should be understood that web  10  may have any shape depending upon the size and shape product packaged therein. As illustrated in  FIG. 1 , product-release coating  50  may be applied as a contiguous pattern  51  covering the entire area  60  encompassed by sealing border  30 . Alternatively, product-release coating  50  may be applied as a non-contiguous pattern  52  covering the entire area  60  encompassed by sealing border  30  as illustrated in  FIG. 2 . Such non-contiguous coating may include a pattern of multiply strips, blocks, circles or dots and combinations thereof printed in registration onto inner surface  21  of web  10 . 
         [0026]    In at least one embodiment, inner surface  21  of web  10  is formed from a polymer layer  25  of polyamide, polyethylene, polyethylene terephthalate or polypropylene. In one embodiment, web  10  will be a mono-layer film having a polymer layer of polyamide, polyethylene, polyethylene terephthalate or polypropylene. Alternatively, web  10  will be a multilayer film having an inner surface  21  formed from a polymer layer  25  (see  FIG. 3 ) of polyamide, polyethylene, polyethylene terephthalate or polypropylene. In a preferred embodiment, the polymer layer is an oriented polyamide, oriented polyethylene terephthalate or oriented polypropylene. Exemplary of commercially available oriented polypropylene free-standing films include those sold under the trademark Bicor™ supplied by Jindal Films, Films Americas LLC (Albany, N.Y., U.S.A.). One particular example of such films include Bicor™ 75 CSR-2 which is characterized as a 0.75 mil (19.05 μm) film designed for cold seal release. 
         [0027]      FIG. 3  illustrates a cross-sectional view of packaging web  10  taken along line A-A of  FIG. 1  depicting polymer layer  26 , cold-seal adhesive coating  40  positioned adjacent to first side edge  11  and an opposing second side edge  12 , and a product-release coating  50  therebetween. In this embodiment, the product-release coating  50  abuts with sealing border  30  (see also  FIGS. 1 and 2 ). Alternatively, in some embodiments, inner surface  21  may have an adhesive-free margin  61  separating the sealing border  30  from the product-release coating  50  as is illustrated in  FIG. 4 .  FIG. 5  illustrates a cross-sectional view of packaging web  10  having the adhesive-free margin  61  taken along line B-B of  FIG. 4 . Because the release properties of product-release coating  50  may interfere with the adhesive properties of the cold-seal adhesive coating  40 , margin  61  significantly reduces the risk of mixing of these two materials. In some embodiments, it may be beneficial to include an additional cold-seal adhesive release layer  70  such as a cold-seal release coating on opposing surface  22  of web  10  as illustrated in  FIG. 6 . FIG,  6  illustrates a cross-sectional view of packaging web  10  taken along line B-B of  FIG. 4 . In this illustration, web  10  includes an adhesive-free margin  61 , product-release coating  50  and cold-seal adhesive coating  40  on inner surface  21 , and cold-seal adhesive release layer  70  on opposing surface  22 . 
         [0028]    It is also contemplated the inner surface  21  of web  10  may further include a second adhesive-free margin  62  separating the first side edge  11  and the sealing border  30 , and a third adhesive-free margin  63  separating the opposing second side edge  12  and the sealing border  30  as illustrated in  FIG. 7 . 
         [0029]    In some embodiments, that various combinations of layers can be used in the formation of packaging webs according to the invention. Since the inventive webs may advantageously be used to hold oxygen or moisture sensitive articles, it is preferred to use a combination of layers which includes one or more oxygen and/or moisture barrier layers. The terms “barrier” or “barrier layer” as used herein means a layer of a multilayer web which acts as a physical barrier to moisture or oxygen molecules. For example, the oxygen and/or moisture barrier material may include metal foils, such as aluminum foil and barrier coatings deposited onto a polymer layer such as metal, silica, alumina and the like, The phrase “barrier coating” refers to a coating that may be applied to one or both surfaces of a film by any known method such as sputtering, vacuum deposition or electroplating (all of which involve some act or method of “depositing” a continuous inorganic material, metal, metal oxide, metal alloy, silicon or silicon oxide layer onto the surface of a polymer substrate). The metal used can vary, though aluminum, zinc, gold, silver or appropriate alloys of such are preferred, with aluminum or aluminum-containing alloys being particularly preferred. As will be recognized by those skilled in the art, while the metal coating predominantly consists of the identified metal (such as aluminum), amounts of other additives may be present to improve assorted physical and optical properties of the deposited metal layer. In one preferred embodiment as depicted in  FIG. 8 , packaging web  10  includes a five layer structure with polymer layer  25 , a barrier layer  45 , a laminating adhesive layer  55 , an printed ink layer  65 , and cold-seal adhesive release layer  70 .  FIG. 8  illustrates a cross-sectional view of packaging web  10  taken along line C-C of  FIG. 7  depicting cold-seal adhesive coating  40  positioned spaced apart from first side edge  11  by second adhesive-free margin  62  and spaced apart from an opposing second side edge  12  by third adhesive-free margin  63 , In this embodiment, the product-release coating  50  is applied contiguously within the sealing border  30  to adhesive-free margin  61 . In this embodiment, web  10  includes an inner surface formed from polymer layer  25 , a barrier layer of deposited metal  45 , a layer of laminating adhesive  55 , a layer in printed ink  65 , a layer of oriented polypropylene, oriented polyethylene terephthalate or oriented polyimide  75 , and a cold-seal adhesive release coating  70 . 
         [0030]    The above description and the following examples illustrate certain embodiments of the present invention and are not to be interpreted as limiting. Selection of particular embodiments, combinations thereof, modifications, and adaptations of the various embodiments, conditions and parameters normally encountered in the art will be apparent to those skilled in the art and are deemed to be within the spirit and scope of the present invention. 
       WORKING EXAMPLES 
       [0031]    In all the following examples, all film structures were produced using a cast coextrusion apparatus and method which are well known to those skilled in the art. The cast coextrusion film apparatus includes a multi-manifold flat die head for film through which the film composition is forced and formed into a flat sheet. The sheet is immediately quenched e.g., via cooled water bath, solid surface and/or air, and then ultimately collapsed and formed into a film. 
         [0032]    Specifically, the multilayer films of the present invention and comparative films had the following structures, from the inner (sealing or food contact) layer to the outer (skin or non-food contact) layer 
       Example 1 
       [0033]    Example 1 is one embodiment of a packaging film of the present invention illustrated in  FIGS. 7 and 8  having a structure and layer compositions as described below: 
         [0034]    Layer  70  is 100% of a cold-seal adhesive release coating. 
         [0035]    Layer  75  is 100% of an oriented polypropylene. 
         [0036]    Layer  65  is an ink layer 
         [0037]    Layer  55  is 100% of an urethane acrylic water-based laminating adhesive. This material is commercially available and sold under the trademark Purethane™ A-1090 supplied by Ashland Inc, (Covington, Ky. USA). 
         [0038]    Layer  45  is 100% of a barrier layer of deposited aluminum metal. 
         [0039]    Layer  25  is 100% of an oriented polypropylene. 
         [0040]    Coating  50  is 100% of a product-release coating. This coating is commercially available and sold under the tradename INXClear anti-fog 1309444 by INX International Ink Company (Appleton, Wis., U.S.A.). 
         [0041]    Coating  40  is 100% of an acrylic cold-seal adhesive coating. This adhesive is commercially available and sold under the trademark Turbo-Seal C2978B by Bostik, Inc, (Wauwatosa, Wis., U.S.A.), 
         [0042]    Layers  70  and  75  were purchased as a single multilayer free-standing film. A non-limiting example of such films is sold under the trademark Bicor™ 75 CSR-2 from Jindal Films, Films Americas LLC (Albany, N.Y., U.S.A.), It is characterized as having a thickness of 75 gauge (19.05 micron), a bulk layer of oriented polypropylene (OPP) and an outer layer of cold-seal release coating. This film will be referred to as freestanding film #1. 
         [0043]    Layers  45  and  25  were purchased as a single two-ply free-standing film. A non-limiting example of such films is available under the trademark Metallyte® 50 TSPM OPP Film from Jindal Films, Films Americas LLC (Albany, N.Y., U.S.A.). This film is a 50 gauge high barrier, non-sealable oriented polypropylene (OPP) film having an aluminum metallized first side and an opposing treated second side. This film will be referred to as freestanding film #2. 
         [0044]    The film structure as depicted in  FIGS. 7 and 8  was produced using methods and techniques generally known in the art. The freestanding film #1 was first reverse printed on the face opposite the release coating. The urethane acrylic water-based laminating adhesive  65  was then applied to layer  66  of freestanding film #1, and was then laminated to the metal layer  45  of freestanding film #2. The product-release coating  50  was then applied to surface  21  of inner layer  25  using standard printing techniques in registration with the printed graphics of film #1 in an amount of 1.7 lbs/ream wet. The product-release coating  50  was dried to remove any residual solvent to a dry weight of between 0.04 and 0.2 lb/ream. Lastly, using standard printing techniques, the acrylic cold-seal adhesive coating  40  was applied to surface  21  of layer  25  in registration with the product release coating  50 . 
         [0045]      FIG. 9  depicts one embodiment of a package  100  fabricated from the packaging webs of the present invention. A horizontal or vertical flow wrap machine may be used to produce the package as depicted in FIG,  9 , Preferably, a horizontal flow wrapper machine is used. Once the food product is placed on the flat packaging web where the product-release coating has been applied, the web passes through a forming collar where it is formed into a tube. A set of sealing wheels makes a longitudinal seal  101  by pressing the inner surfaces of the tube together where the cold-seal adhesive coating has been applied thereby forming a fin seal  102 . Two cross seals or end seals  103  and  104  are formed through the tube by cross-sealing jaws and the tube is cut above and below each cross seal to individualize the finished package.