Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2001-09-04
2003-09-02
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S141000, C428S143000, C428S147000, C428S337000, C428S339000, C428S343000, C428S346000, C428S347000, C428S348000, C428S349000, C428S354000, C428S446000, C428S448000, C428S450000, C428S482000
Reexamination Certificate
active
06613430
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method for creating a release product by means of coating a polyester film with a release coating containing a polyolefinic wax and a cross-linkable acrylic. The polyester-compatible release coating and coated film are also disclosed.
2. Description of Related Art
Release films are desirable for many applications. Silicone-coated polymer films are well known and commercially available for use as release films. These release films are often used as backer sheets for adhesive-coated stock, including labels, pressure sensitive tapes, decorative laminates, transfer tapes and the like. The adhesive easily releases from such surfaces with minimal force. Release coatings can also be used in contact with food items, to prevent sticking and to promote release of all of the food from the surface of the film.
Cold seal adhesives are desirable for many applications. These adhesives are capable of bonding to themselves under pressure at ambient temperatures. Typically, cold seal adhesives are used where the item being packaged is heat sensitive. Examples of such heat sensitive items are food items, such as candy. Many non-food items are also heat sensitive and preferably contain or are packaged using cold seal adhesives. Frequently, the packaging material used in conjunction with cold seal adhesives is a film substrate, to which a cold seal adhesive can be applied. Film bearing a cold seal adhesive is usually wound into a roll by the manufacturer or converter before being formed into a package and filled. However, the cold seal adhesive will tend to bond to the opposite side of the wound roll during storage unless a separate layer having cold seal release properties is placed between the front and back faces, or unless the opposite side itself has cold seal release properties.
Cold seal packaging films known in the market are polyolefin based. Biaxially oriented polypropylene film is commercially available as a cold seal film. Migrating additives and propylene-based coatings have been disclosed for use on the face of the polypropylene film opposite the face bearing the cold seal adhesive. These additives and coatings are intended to provide a cold seal release capability to the film to prevent adhesion of the rolled layers. However, these additives and coatings have been adapted for use on polypropylene film. Their compatibility with or suitability for use on polyester film has not been established.
Release film is also used in the capacitor industry. Capacitors are typically coated with a ceramic-type coating during manufacture. This coating must later release from the substrate to permit use in the finished capacitor. Many other uses of release film are contemplated. For example, release films are commonly used as protective coatings on building products such as plastic or metal sheets or formed items, such as window films, faucets, decorative hardware and the like. Such films also are used to protect automobile finishes during transport.
In addition, polyester film coatings containing cross-linkable acrylics or polyolefin waxes are known. However the combination of the two, and their surprising release properties when combined, are not disclosed in the art.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a release coating suitable for application to a base polyester film.
It is a further object of the present invention to provide a release surface having a release force of less than about 100 grams per inch (about 40 grams per cm), preferably for cold seal adhesive release.
It is another object of the present invention to provide a release surface having low haze.
It is a further object of the present invention to have a release coating suitable for use with cold seal adhesives.
It is a further object of the present invention to have little to no adhesive deadening or reduction in adhesive properties due to the transfer of the release coating.
It is a further object of the present invention to have little to no adhesive transfer to the release surface.
It is a further object of the present invention to provide a reclaimable polyester film having cold seal release properties.
It is another object of the present invention to provide a release surface suitable for use with ceramic coated capacitors.
It is a further object of the present invention to achieve a coefficient of friction in the range of about 0.20 to about 0.35.
It is a further object of the present invention to achieve a surface energy level of about 15 to about 40 dynes/cm.
The present invention has accomplished these objectives by providing in a preferred embodiment a coated polymer film having a release coating including a cross-linkable acrylic and a polyolefin wax, the coating used therewith, and the method of applying such coating to film.
DETAILED DESCRIPTION OF THE INVENTION
The present inventors have surprisingly found that excellent release properties are provided by a coating that includes a polyolefin wax and a cross-linkable acrylic.
The release coating of the present invention preferably includes a polyolefin wax. Without intending to be bound by theory, it is believed that the polyolefin wax acts to provide the proper degree of release properties to the film in relation to the cold seal adhesives. Preferred waxes include polypropylene and polyethylene waxes, either alone or in combination. An oxidized homopolymer of ethylene wax commercially available from Michelman as ME18325 wax is most preferred for use herein, in part due to the fact that it does not yellow during the reclamation process. Polytetrafluoroethylene wax is also preferred for use herein, alone or in combination with other waxes. Other waxes such as carnauba, paraffin, montan and combinations of the foregoing may be combined with the polyolefin wax if desired, or used without the polyolefin wax.
The polyolefin wax is preferably present at about 0.05 to about 15 percent by weight of the coating solution, and in an alternate preferred embodiment, it is present at about 1 to about 4 percent by weight of the coating solution. Optimally, the wax is present at about 2 to about 3 percent by weight of the coating solution.
It is also preferred that the release coating of the present invention include a cross-linkable acrylic. Without intending to be bound by theory, it is believed that the cross-linkable acrylic forms three-dimensional nodules on the surface of the film, thus texturing it and controlling the coefficient of friction of the resulting surface. Preferred cross-linkable acrylics include methacrylate-based polymers, including those described in U.S. Pat. Nos. 5,096,784 and 5,114,739 to Culbertson et al. (commonly assigned), the disclosures of which are incorporated herein by reference. Preferably, the cross-linkable acrylic includes methylmethacrylate, ethyl acrylate, N-methylol acrylamide, methacrylamide, external crosslinking agents such as melamines, aziridines and the like, or combinations of the foregoing. As described in the '784 patent, a preferred acrylic terpolymer comprises 80 mole percent methyl methacrylate, 15 mole percent ethyl acrylate and 5 mole percent N-methylol acrylamide, with 0.2 percent by weight sodium lauryl sulfate and 5.0 percent by weight octylphenol ethoxylate. Thus surfactants are also preferably included in the compositions of the present invention.
The cross-linkable acrylic is preferably present at about 0.05 to about 5 percent by weight of the coating solution, and in an alternate preferred embodiment, it is present at about 0.2 to about 0.3 percent by weight of the coating solution. It is believed that other polymeric binders will also function with or in place of the cross-linkable acrylic. Optimally, the cross-linkable acrylic is present at about 0.25 percent by weight of the coating solution.
A resulting wax to acrylic ratio of about 1:1 to about 30:1 is preferred, and in an alternate preferred embodiment it is present at a ratio of about 5:1 to about 15:1.
Alfaro Jose F.
Culbertson Edwin C.
Gust Stephen J.
Heberger John M.
Muschelewicz Kenneth J.
Mitsubishi Polyester Film LLC
Ribar Travis B
Seidleck James J.
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