Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-02-27
2003-05-20
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S275500, C156S275700, C156S277000, C156S314000, C428S141000, C428S343000, C428S345000, C428S346000, C428S352000
Reexamination Certificate
active
06565697
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
FIELD OF THE INVENTION
This invention relates to adhesive articles with positionable and repositionable bonding properties, and more particularly to adhesive articles having a discontinuous layer of non-adhesive material applied onto a layer of adhesive material.
BACKGROUND OF THE INVENTION
Traditional pressure sensitive adhesive (PSA) sheets, films, and tapes are sometimes difficult to apply because of the inherently tacky adhesive surface. Specifically, precise positioning of a tacky or “quick stick” adhesive product is difficult once adhesive contact has been made with a mounting surface, because it is difficult to slide or reposition the product. Also, air entrapment between the PSA article and mounting surface is a problem with dimensionally large PSA products. Additionally, “blocking” or adhesive-to-adhesive contact is problematic for dimensionally large products or thin gauge PSA products during pre-application handling.
The term “positionable” is used herein to indicate a PSA article with a sufficiently low degree of tack (or no tack) to allow the adhesive surface to be slid across the mounting surface without sticking or grabbing. The term “repositionable” is used herein to indicate a PSA article that can be engaged with pressure to the mounting or application surface in a final manner, then removed therefrom, and then reapplied without significant degradation of positionable feature.
In some instances consumers may desire special PSA functional properties. For example, when using a PSA sheet, film, or tape as a protective covering, a consumer may want to selectively “activate” only certain areas of the adhesive surface with pressure (i.e., just the edges of the PSA product) rather than across the entire adhesive surface of the PSA product. This feature would be applicable for wrapping or sealing applications. Additionally, consumers often desire a repositionability feature, allowing the product to be used a number of times while retaining the initial low-tack or no-tack properties.
Several methods and configurations have been developed to make application of PSA films and tapes easier. Frequently, application aids such as detergent and water have been used to reduce initial tack and impart positionable features in a typically non-positionable PSA product. Formulations vary, but typically include water, a surfactant or lubricant, and/or a solvent (generally an alcohol) that speeds bond formation and drying. The liquids tend to form a film between the adhesive and substrate, thus preventing contact and preadhesion. Unfortunately, the liquid is difficult to remove and is seldom completely removed. Additionally, most application aids affect the adhesive properties and prevent rapid formation of a strong bond between adhesive and substrate. The application aids may also mar or stain the mounting surface.
Some methods involve PSA products with reduced initial contact tack, but with more permanent long-term bonding. U.S. Pat. No. 5,346,766 discloses a positionable and repositionable PSA product which has an initially non-tacky surface. These characteristics are achieved by intimately mixing a detackifying resin and detackifying particulate into the adhesive film layer. After application, adhesion does build with passage of time or from heating. However, a product that provides a rapid increase in tack and adhesion properties is often more desirable to reduce installation time. Additionally, this product has a relatively narrow range of application temperatures.
Alternatively, discontinuous coatings of non-tack or low-tack materials projecting from the adhesive surfaces have been used to prevent premature contact (i.e., adhesion before it is wanted or expected) between the adhesive and substrate. The height of these discontinuous coatings or materials creates an air gap between the adhesive layer and the substrate. At the time of application, pressure is applied to initiate adhesion. There are several variations of this general technique described in the art.
U.S. Pat. No. 4,054,697 discloses deformable particles that recover their original shape after pressure is removed. However, U.S. Pat. No. 4,054,697 points out that with resilient particles, a sufficiently strong bond must be formed to the support surface to “prevent the deformed particles from recovering to their undeformed dimensions,” which “would cause the sheet material to come away from the support surface”. U.S. Pat. No. 4,054,697 further points out that “it may be desirable for the pressure sensitive adhesive to be curable after the sheet material has been adhered” to “overcome any tendency of the deformed particles to recover.”
U.S. Pat. Nos. 3,331,729; 3,314,838; and 6,020,062 disclose using glass microspheres, micro-particles, or micro-balloons which are either partially or fully embedded in the adhesive layer. In these constructions, application pressure to the adhesive article crushes and/or embeds the microspheres into the adhesive layer. Crushing and/or embedding the microspheres into the adhesive layer permits the bulk of the adhesive to contact the mounting surface and instantly form a strong bond. Unfortunately, the destructive nature of the application process hinders re-use or repositioning of the product.
U.S. Pat. Nos. 4,376,151; 4,556,595; and 5,008,139 disclose non-adhesive solid particles, hollow particles, powders, or talcs which are either applied on the surface of the adhesive or embedded partially in the adhesive. Once a threshold application pressure is applied, the non-adhesive solids migrate into the adhesive layer and surface adhesion increases. Again, once the solids have migrated into the adhesive layer, such products lose the repositionable features.
Alternatively, discontinuous coatings of non-tacky materials that project from a relatively planar adhesive surface have also been used to prevent preadhesion of a PSA layer during application. These adhesive films and tapes have no adhesion when placed lightly against the mounting surface. Such films are disclosed in U.S. Pat. Nos. 3,554,835; 4,023,570; 4,054,697; 4,151,319; 5,008,139; and U.K. Patent No. 1,541,311. Manufacturing methods described in these references are often somewhat complex, involving the use of relatively expensive embossed release liners or multiple drying steps.
U.S. Pat. No. 5,591,290 discloses modifying the adhesive properties of a pre-manufactured laminate or label stock by applying a discontinuous layer of non-adhesive material to the PSA article. This process involves stripping a liner off a pre-manufactured adhesive laminate, applying a non-adhesive coating, and then re-laminating the liner. Although this method may be effective for small volume production, it is costly to add this additional manufacturing step. Additionally, with this manufacturing method it is difficult to control the three dimensional shape of the non-adhesive.
Other methods for handling preadhesion include formation of brittle plastic projections on a PSA article surface, such as disclosed in U.S. Pat. No. 3,301,741, or formation of small discrete clusters of particles protruding from the adhesive surface, such as disclosed in U.S. Pat. No. 5,141,790. For example in U.S. Pat. No. 5,141,790, the particles are tacky adhesive microspheres that provided weak bonding to a substrate when applied using light application pressure and strong bonding when applied using higher application pressures. However, this multi-adhesive construction tends to be more difficult to construct and adhesive particle transfer can be a problem.
In addition, U.S. Pat. Nos. 3,691,140 and 4,166,152 disclose microsphere and patterned adhesives exhibiting repositionable properties, and U.S. Pat. No. 4,735,837 discloses deformable microspheres which provide a rough or pebble-like surface and repositionable bond. In all these cases, the adhesive films readily form weak, repositionable bonds to a substrate, but do not form a strong, permanen
Ball Michael W.
Haran John T.
Quarles & Brady LLP
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