Abstract:
Sealing (peel seal) membranes for packaging aggressive or chemically reactive products such as hair colorants over long periods without seal failure are described. Advantageously, the membranes and other packaging components have a high resistance to chemical attack and exhibit other advantageous characteristics, such as good barrier properties that minimize or eliminate interaction with the external environment, chemical inertness with respect to the product, and desirable heat sealing properties for prolonged adhesion without cracking and/or product leakage. The membranes comprise an inner bonding layer comprising a blend of polyethylene (PE) with an anti-cohesion additive, and a barrier layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority of U.S. Provisional Application Ser. No. 61/228,274, filed Jul. 24, 2009, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the packaging of products including hair colorants comprising reactive ingredients such as acidic, basic, and/or oxidizing compounds. A sealing membrane having an inner layer made of polyethylene (PE) with an anti-cohesion additive, used to cover an opening such as a dispensing orifice of the product container, provides chemical resistance for long-term storage of the packaged product. 
       DESCRIPTION OF RELATED ART 
       [0003]    Membranes for sealing plastic or laminate containers, particularly so-called, easily removable “peel seal” membranes or structures, are used for storage of a number of products, including foods, cosmetics, and dentifrices. Ideally, these membranes are engineered to provide a lasting barrier that prevents contact of the product with oxygen, prior to use. Heat sealing of the membrane to the container opening, for example, promotes high membrane/container adhesion and thereby mitigates product leakage and/or air exposure over prolonged storage periods. Other important characteristics of such membranes are their inertness with respect to the contained product and ease of removal by the user with only manual force (i.e., without the need for scissors, a knife, or other instrument). 
         [0004]    A particular type of removable “peel seal” membrane conventionally used utilizes an ionomer such as Surlyn® for bonding with the container and covering its dispensing opening or orifice. Ionomers exhibit a number of desirable properties including good sealing/adhesion, ease of manufacture based on a broad “operating window” of seal temperature and pressure, and reasonable peel forces required to separate the ionomer layer from the container, even for relatively small areas of bonding or contact between this layer and the container mouth (e.g., at a circular ridge around the container opening). 
         [0005]    However, such “peel seal” membranes are generally not used for sealing containers containing “aggressive” or chemically reactive products, such as hair dye products, which may comprise acidic, basic, and/or oxidizing ingredients. Indeed, the containment of such products lead to the failure of the sealing material of the membrane during product storage over extended periods and/or under conditions (e.g., elevated temperatures) that accelerate chemical degradation/attack of the sealing layer. 
         [0006]    For these reasons, hair dye products, and in particular permanent dyes, have for many years been sold in aluminum dispensing tubes due to the high bather properties of such containers and their ability to resist chemical attack from such reactive products. Such tubes are manufactured by impact extrusion, so as to form a complete container, including a thin layer of aluminium covering the orifice area. In other words such aluminium tubes exhibit an integrated “membrane” closing the container. To open such tubes, the membrane must first be pierced by the consumer. 
         [0007]    However, there is an ongoing market need for new, innovative and hence improved packaging systems, and in particular containers made primarily from plastic materials. An example would be those utilizing laminate tube manufacturing technology. Such tubes, manufactured from a multilayerd structure, or “web” provide considerable marketing advantages. However, it has traditionally been impossible to manufacture such tubes or containers with sufficient chemical resistance to envisage using them for very aggressive products. In particular, their manufacturing technology requires the orifice of the container to be sealed after manufacture in order to prevent the reactive contents from being altered by contact with air, and at the same time be chemically resistant enough to withstand prolonged contact with aggressive contents. Sealing the orifice requires application of a sealing membrane, and preferably a membrane that can be manually pealed from the container by the consumer before use. Until now no such “peal seal” membrane has been found for storing aggressive or chemically reactive products such as hair dyes. 
       SUMMARY OF THE INVENTION 
       [0008]    Despite some favorable qualities of conventional sealing membranes, for example those utilizing an ionomer layer, it has been determined that long-term chemical resistance to aggressive products remains an issue. Hence, they cannot be used in the presence of aggressive products, for example hair dyes and others that are normally dispensed by squeezing them through an opening in a collapsible tubular container, as they are not chemically inert in the presence of significantly acidic, basic, and/or oxidizing ingredients. Such aggressive product formulations therefore pose significant challenges in terms of providing suitable packaging components having extended storage capability. For example, conventional ionomer bonding layers are subject to chemical attack by products containing ammonium hydroxide, leading to leakage of the product after time and/or even complete seal failure. 
         [0009]    The present invention is associated with the discovery of packaging components exhibiting unexpected chemical stability to aggressive or chemically reactive products (e.g., containing acidic, basic, and/or oxidizing ingredients). These packaging components, including the container and sealing membrane, also provide excellent sealing/adhesion between these components as well as other properties required for extended storage of such products, prior to use. Particular aspects of the invention are associated with the finding of sealing (particularly peel seal) membranes, typically having multiple layers, used to cover the opening of product containers. These sealing membranes advantageously have a high resistance to chemical attack, as required for the packaging of aggressive products without seal failure. The sealing membranes also exhibit other important characteristics, such as good barrier properties that minimize or eliminate interaction with the external environment, chemical inertness with respect to the product, and desirable heat sealing properties for prolonged adhesion without cracking and/or product leakage. 
         [0010]    The containers themselves, to which the sealing membrane is adhered (e.g., by heat sealing at its inner layer), may comprise plastic or have a multi-layer laminate structure. According to a particular embodiment, the container does not comprise aluminum or an aluminum layer, as used in conventional packaging of hair dyes and other aggressive products. An additional aspect of the invention is therefore associated with the discovery of laminate containers (e.g., tubes) having the same functional performance as conventional containers comprising aluminum and demonstrating compatibility with, and protection of, aggressive products during storage. 
         [0011]    Particular embodiments of the invention are directed to packaged products having the packaging components of a container and sealing membrane, in which the interface bond between the membrane and the container orifice is improved, relative to conventional packages, to obtain superior performance characteristics, including good sealing at elevated temperatures and/or extended storage times, high adhesion, and long-term chemical resistance. The sealing membrane used to cover the opening of the container advantageously comprises an inner layer made of a blend of polyethylene (PE), in particular a low density polyethylene, with an anti-cohesion additive, in contact with the container, as well as a barrier layer (e.g., an aluminum layer) to provide an effective chemical barrier. The overall sealing membrane is therefore easily removed by peeling yet highly resistant to chemical attack/degradation. According to some embodiments, a conventional ionomer (or ionomer layer) is absent from the sealing membrane. In any event, the container and sealing membrane cooperate to form a package that is suitable for containing aggressive products (e.g., hair colorants) and particularly those comprising one or more reactive ingredients selected from inorganic hydroxides (e.g., ammonium hydroxide), inorganic halides (e.g., aluminum chloride), and peroxides (e.g., hydrogen peroxide). 
         [0012]    Particular sealing membrane structures are those having a low cohesive strength that allow the user to peel the sealing membrane from the container opening of the packaged product with manual (digital) forces, for example in the case of removal of a sealing membrane with an inner PE layer from a PE container. Layered sealing membranes having a low molecular weight PE inner layer are particularly suitable due to their peel strength performance. Due to the presence of an anti-cohesion additive in the inner layer, the locus of failure during peeling of such membranes is internally, or within the film, rather than at the membrane/container interface. The peel force is therefore determined by the mechanical properties of the blend of PE and anti-cohesion additive itself instead of the quality of the sealing operation. In addition to an inner layer of PE, the sealing membrane can comprise, as an exemplary barrier layer, an aluminum foil layer in contact with (e.g., disposed directly adjacent to or above) the inner layer. Optionally, an external support layer, for example a polyester layer, such as a polyethylene terephthalate (PET) layer, can be used for enhancing rigidity or a printing (e.g., paper) or embossing layer for providing decorative features. The PE-based sealing membranes described herein combine excellent seal performance in manufacturing with excellent chemical resistance to acid, basic, or oxidizing environments, at both ambient and elevated storage temperatures. 
         [0013]    Further embodiments of the invention are directed to packages for dispensing aggressive products, comprising a container having an opening and a sealing membrane, as described herein, covering the opening and adhered thereto (e.g., as the result of heat sealing). Yet further embodiments are directed to methods for dispensing such products comprising peeling the membrane from the container opening and squeezing the container to dispense the product, using manual (digital) forces for both removal of the membrane and dispensing of the aggressive product. Still further embodiments are directed to sealing membranes, as described herein, for covering an opening of a container having an aggressive product disposed therein. Even further embodiments are directed to methods of making packaged products comprising adhering the inner layer of a sealing membrane as described herein to a container to cover its opening, with the container having an aggressive product disposed therein. The adhering may be performed, for example, by heat sealing. Preferably, the inner layer of the sealing member is adhered such that manual peeling forces are sufficient to remove the sealing membrane from the container. 
         [0014]    These and other embodiments and aspects of the invention are apparent from the following Detailed Description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  depicts a representative packaged product with a tubular container and sealing membrane as packaging components. 
           [0016]      FIG. 2  depicts a representative structure used for a multi-layer sealing membrane. 
           [0017]      FIG. 3  depicts another representative structure used for a multi-layer sealing membrane. 
           [0018]      FIGS. 4A-4C  depicts failures associated with conventional sealing membranes and tubular containers, used for storing aggressive products over an extended period. 
       
    
    
       [0019]    The features of the packaged products and multi-layer structures are not necessarily drawn to scale and should be understood to present an illustration of the invention and/or principles involved. Some features depicted in the figures may be enlarged or distorted relative to others, in order to facilitate explanation and understanding. The same reference numbers are used in the figures for similar or identical components or features shown. Packaged products and sealing membrane structures will have configurations and components determined, in part, by the intended application and also the environment in which they are used. 
       DETAILED DESCRIPTION 
       [0020]    “Aggressive products” as described herein, such as hair colorants (or hair dyes), are chemically reactive and generally contain one or more acidic, basic, and/or oxidizing ingredients. These ingredients often fall within the chemical classes of inorganic hydroxides, inorganic halides, and peroxides. Inorganic hydroxides include ammonium hydroxide as well as alkali and alkaline earth metal hydroxides (e.g., potassium hydroxide and calcium hydroxide). Inorganic halides include fluorides, chlorides, bromides, and iodides of ammonium and metals such as transition metals, alkali metals, and alkaline earth metals. Aluminum chloride, potassium chloride, and ammonium fluoride are specific examples. Peroxides include hydrogen peroxide, urea peroxide (carbamide), and alkali and alkaline earth metal peroxides (e.g., sodium peroxide). Representative aggressive products have pH values of less than about 4 (e.g., in the range from about 1 to about 4, or from about 1 to about 3) or otherwise pH values of greater than about 9 (e.g., in the range from about 10 to about 13, or from about 10 to about 12), and often greater than about 11 (e.g., in the range from about 11 to about 14). 
         [0021]    As discussed above, the present invention is associated with the packaging of hair colorants and other aggressive products using a particular combination of packaging components, including a container and sealing membrane that can effectively contain the product over long periods.  FIG. 1  depicts a representative packaged product  100  comprising a tubular container  2  and sealing membrane  4  covering the opening of container  2 . Peeling of sealing membrane  4  with manual force may be facilitated using pull tab  6  to separate it from container  2  at the ring-shaped area of contact between sealing membrane  4  and container  2  (partially defined by the dashed, inner circle in  FIG. 1 ). Container  2  can have a circular or oval-shaped cross section in any plane perpendicular to its axis  8 , generally extending through the center of sealing membrane  4 . In the embodiment depicted in  FIG. 1 , tubular container  2  is flared, such that the cross-sectional area from the container opening to crimped end  10  gradually increases. In other embodiments, this cross-sectional area may be substantially constant with respect to axial position or may even taper or decrease. Threads  7  may be used to engage a removable screw cap (not shown) for covering the container opening. 
         [0022]    Normally, tubular dispensing containers of this type, in which the product is to be dispensed by the application of manual pressing forces, have a restricted opening for greater control of the flow, amount, and placement of dispensed product. According to particular embodiments, therefore, the container opening generally has an area of less than about 50%, typically less than about 40%, and often less than about 25%, of a cross-sectional area, measured at any plane perpendicular to the axis of the container (e.g., which may also be any plane parallel to the opening). This embodiment contrasts with conventional containers used, for example, for storing food products with wide openings that allow removal using eating utensils. A representative container is a laminate having a PE inner layer, an aluminum foil middle layer, and a PE outer layer. The surface of the PE outer layer may be printed to provide decorative effects and/or convey product information. Adhesive, tie, or compatibility layers may be incorporated between the inner and middle layers and/or the middle and outer layers, to provide the laminate structure. In this manner, the use of a PE/Aluminum/PE structure creates a “continuity” of chemical resistance between the container and a sealing membrane also having the PE (e.g., modified PE) and aluminum layers. This is especially important for providing resistance from chemical attack around the container opening/sealing membrane junction, which has been found to be a key weak area of the overall package and an important consideration for aggressive products in particular. As discussed above, in other particular embodiments of the invention, the container does not include aluminum (e.g., as an aluminum layer). According to further embodiments of the invention, the container does not include PET or at least does not include a PET external or outer layer. 
         [0023]    A representative multi-layer structure for a sealing membrane  4  is shown in  FIG. 2 . As discussed above, inner layer  20  of sealing membrane comprises a blend of PE and an anti-cohesion additive, the inner layer  20  typically having a thickness from about 10 to about 60 microns, and often from about 25 to about 40 microns. Suitable anti-cohesion additives may be polymer-based fillers such as polypropylene or polybutadiene that during film production become spherical or create discrete nodules. Inorganic additives include metallic oxides and carbonates (e.g., TiO 2  and CaCO 3 ), often in powder form, and other materials that can be incorporated as fillers. Polybutene may also be used, as well as combinations of any of the additives discussed above. Those having skill in the art, with knowledge of the present disclosure, will be able to adjust the addition level of any additive or combination of additives to obtain a desired peel force, with this force generally decreasing as additive rate is increased. Typically, the inner layer may comprise between 5 to 50% by weight of anti-cohesion additive, preferably between 10 and 15% by weight without affecting the chemical stability of the inner layer. 
         [0024]    According to particular embodiments illustrated on  FIG. 2 , the PE of the inner layer is of a relatively low or medium density, with the anti-cohesion additives often being non-compatible particles. A representative density range is from about 0.91 to about 0.93 g/cm 3 . The weight of the inner layer normally ranges from about 10 to about 50 grams per square meter (g/m 2 ), and often from about 20 to about 45 g/m 2 . Adjacent to, and in contact with, inner layer  20  is middle barrier layer  30 , which may comprise aluminum foil or other suitable barrier material that provides high resistance to chemical attack. The thickness of middle barrier layer  30  normally ranges from about 12 to about 45 microns, and often from about 15 to about 40 microns. Adjacent to, and in contact with, middle barrier layer  30 , is an external support layer  40  which may comprise a polymer such as polyethylene terephthalate (PET) for enhancing rigidity, or otherwise a printing (e.g., paper) or embossing material for providing designs and/or product information. External layer  40 , when made from PET, typically has a weight from about 1 to about 15 g/m 2 . When paper is used, this weight can increase depending on the paper grade and hence paper weight used. 
         [0025]    According to other embodiments illustrated in  FIG. 3 , the inner and barrier layers, and/or barrier and external layers are separated by an adhesive, tie, or compatibility layer  25  and/or  35  therebetween, to provide the sealing membrane. 
         [0026]    The sealing membrane can be adhered (e.g., by heat sealing) to the mouth or opening of a container to provide packaging for an aggressive product. Good sealing strength is obtained with high density polyethylene (HDPE) substrates (e.g., container materials) over a broad range of sealing temperatures. A substantially constant sealing strength of between 10 and 12 Newton is obtained for a heat sealing temperature range of 180° C. to 240° C. During storage of the packaged product, the seal between the sealing membrane and container is essentially leak proof, and the membrane is advantageously essentially chemically inert with respect to the product, at room temperature (e.g., 20° C.) or even at elevated temperatures (e.g., in the range from 25-50° C.). 
         [0027]    Other advantageous properties of the sealing membrane may include any one, any combination, or all of the following: a total weight from about 100 to about 200 grams per square meter (g/m 2 ), often from about 125 to about 170 g/m 2  (as measured using standard test method ISO 536) a total thickness from about 50 to about 200 microns (μ), often from about 65 to about 150μ (as measured using standard test method ISO 534); a tensile strength from about 35 to about 75 newtons/15 mm (N/15 mm), often from about 40 to about 55 N/15 mm (as measured using standard test method ISO 1924); an elongation from about 5 to about 10%, often from about 7 to about 9% (as measured using standard test method ISO 1924); a burst strength from about 300 to about 500 kPa, often from about 350 to about 475 kPa (as measured using standard test method ISO 2758); a bending value from about 3 mm to about 20 mm, often from about 5 mm to about 15 mm; a water vapor transmission of less than about 0.05 g/m 2 ·day, often less than about 0.02 g/m 2 ·day (as measured using standard test method ASTM ES6); and an O 2  permeability of less than about 0.05 cc/m 2 ·day·bar, often less than about 0.02 cc/m 2 ·day·bar (as measured using standard test method ASTM D3985). A representative example of a sealing membrane structure for providing a peal seal is Aluthene® 40 II E 133/6 (Alcan Packaging, Selestat, France). 
         [0028]    The sealing membranes described herein allow hair colorants, and particularly permanent hair dye formulations that are highly reactive due to their substantial content of ammonium hydroxide, as well as other aggressive products, to be stored in plastic and laminate tubes. Those having skill in the art, with the knowledge gained from the present disclosure, will recognize the applicability of the packages, containers, sealing membranes, and associated methods described herein to the storage and dispensing of various other aggressive products including acidic or alkaline products, or otherwise industrial or household products such as solvents (e.g., drain cleaner) and cleaning products (e.g., mildew removers). It will also be appreciated that various changes can be made in these compositions and methods without departing from the scope of the present disclosure. The subject matter described herein is therefore representative of the present invention and its associated advantages and is not to be construed as limiting the scope of the invention as set forth in the appended claims. 
         [0029]    The following examples are set forth as representative of the present invention. These examples are not to be construed as limiting the scope of the invention as these and other equivalent embodiments will be apparent in view of the present disclosure and appended claims. 
       Comparative Example 1 
       [0030]    “Peel seal” membranes structures, comprising an ionomer inner layer and aluminum barrier layer, were tested for their ability to store hair colorant product containing ammonium hydroxide over extended periods. These membranes were heat sealed to tubes made of high density polyethylene and containing the product, and the sealed tubes were maintained either at ambient temperature or at 45° C. in an oven. The condition of the tubes was observed after 1 month, 2 months, and 3 months of storage. 
         [0031]    Systematically, the peel seal lost adhesion and “delaminated” from the tube orifice or opening. The result was a leaking tube and seal failure. Moreover, before delamination some discoloration was observed on the outside of the tube head that may be explained by migration of components of the hair colorant formulation into and across the peel seal, likely at the edges in the zone of adhesion between the membrane and the tube orifice. Neither of these failure modes (catastrophic delamination, or leakage) was observed immediately after manufacture, but instead became apparent after weeks or months of storage at both ambient temperature and at the elevated temperature, in the “accelerated” testing. The delaminated and discolored seal membranes are shown in  FIGS. 4A and 4B . The discolored tubular containers are shown in  FIG. 4C . 
       Example 1 
       [0032]    Replacement of the ionomer based seal membrane, described above in Comparative Example 1, with a seal membrane made of Aluthene® 40 II E 133/6 (Alcan Packaging, Selestat, France) resulted in successful storage of the same hair colorants tested in this comparative example, for comparable time periods at both ambient and elevated temperatures. The tested seal membrane comprises an inner layer comprising a blend of a low density polyethylene having a density of 0.92 g/cm 3  and polypropylene as an anti-cohesion additive, and having a weight of 30 g/m 2 , a middle bather layer comprising soft aluminum having a thickness of 37 micrometers, an adhesive layer having a thickness of 3 micrometers, and an external layer made of a polyester film having a thickness of 12 micrometers. The sealing membrane and tubular container failure modes illustrated in  FIGS. 4A ,  4 B, and  4 C were not observed. The sealing membrane/container package was acceptable for storage of the aggressive hair colorant, based on no observed (i) discoloration, (ii) delamination of the inner layer or sealing membrane generally, and (iii) migration of the product to inside the sealing membrane.