Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-12-07
2003-04-15
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S161000, C524S538000, C524S540000, C524S606000
Reexamination Certificate
active
06548572
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to non-aqueous coating and ink formulations for use on flexible film or paper packages for food, which require aseptic packaging conditions. Printed and coated packaging materials, and methods of aseptic packaging, as well as the aseptic packages are also disclosed.
DESCRIPTION OF THE PRIOR ART
Foods are generally packaged in portion sizes, which may be single serving portions or multiple serving portions. Disposable packaging is used extensively in all areas of the food industry. The ability to print information directly on such packages offers cost savings, but the packaging processes to which the materials must be subjected are demanding. Typically foods such as milk and juice require packaging under aseptic or sterile conditions, which means that any coatings and/or printing inks used to label such packaging must also endure such conditions. The main product packaging materials comprise flexible films, such as polyethylene alone or in combination with other polymer resins. However, paper-based laminated packaging materials usually comprising paper, polyethylene and aluminum foil are also employed.
Examples of paper-based laminated packaging materials are well known in the art, and include, for example the materials disclosed in U.S. Pat. No. 5,635,011 issued Jun. 3, 1997 to Rosen; U.S. Pat. No. 5,531,060 issued Jul. 2, 1996 to Fayet et al; U.S. Pat. No. 4,495,016 issued Jan. 28, 1985 to Viberg et al; U.S. Pat. No. 4,461,667 issued Jul. 24, 1984 to Pupp; and U.S. Pat. No. 4,424,260 issued Jan. 3, 1994 to Pupp.
Examples of flexible film packaging, heat-sealable polymeric films are typically fabricated into disposable packages for containing flowable materials including for example liquids such as milk, fruit juices and the like. The preferred form of package is a pillow-shaped pouch that is often manufactured on a vertical form, fill and seal apparatus with the flowable material being placed in the pouch as part of its manufacture. It is often the practice to place multiples of such pouches into larger bags upon which product information may be printed. In such instance, the larger bag is not in direct contact with the food that is packaged and as a result the ink requirements are substantially different from those where the pouch itself contains printed matter about product contents and the printed film is in contact with the food.
Thus, where a food product is to be packaged and sterilized, the film used to make the pouch or package for such product must also be sterilized. In addition, the printed film must be capable of not only withstanding the aseptic packaging conditions required for sterilized food products, but also must be capable of withstanding the rigours of manufacture, transport, storage and handling from packaging to the point of sale. These requirements also apply to products that are not sterilized but are subjected to aseptic packaging conditions.
The requirements for an ink for applying to the surface of polymer films are very much dependent on the manufacturing conditions and the product being packaged. The printed film must endure any converting operations, such as printing, laminating, coating, and slitting into rolls of correct width. Previously, in order to produce printed packages that would be capable of sterilization in, for example, a solution of hot hydrogen peroxide, an extra layer of film was applied via a lamination step to cover and protect the surface of the printed film.
The inks and coatings for use with aseptic packaging materials, in particular film pouches must meet a number of different requirements and hence the development of suitable formulations has posed a challenge. For example the peroxide used to sterilize printed film can cause the ink to debond from the polymer surface, dissolve, fade or bleed so that the graphic image on the pouch deteriorates unacceptably. Components in the ink may cause the peroxide sterilant to decompose at an accelerated rate that will shorten its useable life and may pose a serious safety hazard if the containing vessel is not well vented.
Most ink systems, whether solvent-based or water-based, are not suited for printed films which are sterilized in hot peroxide. A number of criteria for identifying suitable ink systems are as follows. The printed films must have the following properties: scuff-resistance; bleed-resistance and colourfastness in the presence of hot hydrogen peroxide solutions; safe for packaging liquid foods like milk, juice and water over a lifetime of ingestion of the fluid product; and non-reactive with hot hydrogen peroxide solution nor catalyze its decomposition reaction.
A wide variety of flexible packaging printing inks and coatings has been proposed in the patent literature and are available commercially. Typically, these inks are printed by rotary letter press printing using flexible rubber plates or by gravure printing using engraved chrome plated cylinders on a wide variety of substrates including plastic films selected from polyolefins, polyesters, polystyrene, cellophane, cellulose acetate and the like. See, for example, U.S. Pat. No. 5,338,785 issued Aug. 16, 1994 to Catena, et al.; U.S. Pat. No. 5,658,968 issued Aug. 19, 1997 to Catena, et al.; and U.S. Pat. No. 4,321,185 to Benitez issued Mar. 23, 1982.
Coating and ink formulations for printing on paper-based laminated aseptic packaging materials are also known. This type of packaging material is sold commercially by Tetra Pak International AB and by Combibloc Inc. An example of a package made from such material is a carton that may be a reclosable aseptic carton. Normally the carton is pre-sterilized and milk after being subjected to an ultra-high temperature (UHT) process is placed in the carton and then hermetically sealed to prevent any contamination.
Typically the laminated packages or cartons are composed of three materials: paper (70%), polyethylene (24%) and aluminum foil (6%). The paper provides stiffness, strength and the block shape. The polyethylene used on the innermost layer seals the package. The aluminum foil provides light and oxygen barrier. A protective polyethylene coating on the exterior keeps the carton dry and covers the printed surface. This coating may be laminated or extrusion coated. The printing of the carton surface may be by roto-flexo printing which requires a laminating and cutting step after the printing.
Examples of paper-based laminated packaging materials can be found in the patent literature. These materials are used to produce aseptic packages. Examples of typical materials are disclosed in U.S. Pat. No. 4,424,260 issued Jan. 3, 1984 to Pupp; U.S. Pat. No. 4,416,667 issued Jul. 24, 1984 to Pupp and U.S. Pat. No. 4,495,016 issued Jan. 22, 1985 to Viberg et al. The last patent references a printed layer but the structure of the packaging material and the process does not involve exposing the printed layer to the sterilizing conditions used in the packaging operation. The process is rendered more complicated because this must be avoided.
SUMMARY OF THE INVENTION
An important aspect of the ink and coating formulations of the present invention is that while polyamide resins, and co-solvent type polyamide resins have previously been incorporated as base varnishes in ink and coating systems, no one has previously recognized the necessity for incorporating such resins with high functionality conducive to good oxidizing conditions, in particular H
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. While manufacturers of such polyamide resins make suggestions as to how their products should be employed, these suggestions are merely starting points and do not provide instructions, which can be carried out on a routine basis to formulate a suitable ink or coating formulation. It has been found that the particular combination of components proposed for the present ink or coating formulation of the present invention allows the production of a surface printed or coated film or paper-based packaging material, which may be subjected to the conditions that exist in a typical aseptic food packagin
Breck Alan Keith
Davids Michael A.
Cain Edward J.
DuPont Canada Inc.
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