Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-04-13
2001-04-03
Berman, Susan W. (Department: 1711)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S272200, C156S275300, C156S275500, C156S275700, C522S039000, C522S044000, C522S046000, C522S053000, C522S109000, C522S110000, C522S120000, C522S121000, C525S098000, C525S297000, C525S304000, C525S305000
Reexamination Certificate
active
06210517
ABSTRACT:
TECHNICAL FIELD
The subject invention relates generally to radiation curable adhesive compositions and, more particularly, to a non-blocking, heat activated adhesive coating compositions and methods for using same.
BACKGROUND OF THE INVENTION
By way of background, radiation curable adhesive compositions are well known in the art as exemplified by U.S. Pat. No. 5,104,921 to Erickson et al.; U.S. Pat. No. 4,483,951 to Brenner; U.S. Pat. No. 5,695,837 to Everaerts et al.; U.S. Pat. No. 5,747,551 to Lewandoski et al.; U.S. Pat. No. 5,284,091 to Kon et al.; U.S. Pat. No. 5,244,962 to Plamthottam et al.; and U.S. Pat. No. 4,952,435 to Okita. These patents disclose adhesive compositions wherein at least a portion of the composition is cured or cross-linked by the application of radiation generally in the form of ultraviolet radiation or electron beam radiation.
The trend in the adhesive coating industry has been to move towards adhesive compositions which are solventless. The Brenner '951 patent exemplifies this movement towards the use of adhesive compositions containing no solvents. The elimination of solvents eliminates air pollution problems, solvent toxicity problems, and can also offer both energy and labor saving since solventless adhesive compositions are capable of curing in much shorter time periods than solvent-based adhesive compositions and can also be cured without the application of external heat which can cause damage to the underlying article or substrate.
The Brenner '951 patent discloses adhesive compositions which are comprised of an elastomer, a chemically compatible ethylenically unsaturated monomer, a tackifier, and an adhesion promotor, and optionally, pigments, fillers, thickeners, and flow control agents, which are converted from the liquid to the solid state by exposure to high energy ionizing radiation such as that from an electron beam. The constituents of the adhesive compositions disclosed in the Brenner '951 patent are common to this class of adhesives, that being, a polymerizable monomer component, an elastomeric component, and a tackifier.
The composition disclosed in the Brenner '951 patent are taught as being primarily useful as an adhesive for the assembly of composite structures or laminates of, for example, a rubber sheet and a metal base. The adhesive composition can be applied to the elements comprising the composite laminate structure and then the laminate can be built up upon the adhesive layers. The laminate is then subjected to an electron beam to cure the adhesive composition. While certain manufacturing or processing schemes may be adequately accomplished using a radiation cured polymer composition such as that disclosed in the Brenner '951 patent wherein the adhesive composition is applied to the components to be adhered together and thereafter the components are irradiated to cure the composition, there exists a need for a radiation cured, heat activated adhesive coating which can be applied to a multiplicity of articles, cured by the application of radiation, the coated articles then stacked or rolled upon each other without adhering to one another, and the coating can later be activated by the application of heat to allow the coated articles to be adhered to a desired substrate.
The prior art is devoid of any teachings or suggestions for an adhesive composition which can be applied or coated onto a multiplicity of articles, the articles then being radiation cured, and then stacked or rolled upon one another without forming a block or adhering to one another at room temperature thus becoming useless for their designated purpose. While the prior art teaches a number of radiation cured adhesive compositions, the prior art does not disclose an adhesive composition which, after being radiation cured, is non-blocking at room temperature and which remains heat activatable to allow a coated, cured article to be affixed to a substrate upon the application of heat thereto.
Accordingly, it would be advantageous and desirable to have a radiation curable coating composition for the preparation of a non-blocking, heat activatable heat adhesive which, following radiation curing, is non-blocking at room temperature but which also remains heat activable and able to subsequently become adhesive.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a radiation curable precursor coating composition for the preparation of a non-blocking heat activable adhesive which comprises a curable acrylic material, a curable elastomeric material, and a hydrocarbon tackifier material having a softening temperature ranging from approximately 50° C. to approximately 200° C. wherein when the acrylic material and the elastomeric material are cured to produce an adhesive coating composition, the adhesive coating composition is non-blocking at room temperature, but when the cured adhesive composition is heated to a temperature above the softening temperature of the hydrocarbon tackifier, the precursor composition becomes adhesive.
Also in accordance with the present invention, there is provided a method for attaching a first article to a second article which comprises providing a radiation curable, adhesive precursor for preparing a non-blocking, heat activable adhesive. The adhesive comprises a curable acrylic material, a curable elastomeric material, and a hydrocarbon tackifier. The method further includes coating the first article with the adhesive precursor, curing the adhesive precursor so as to produce a cured coating of the adhesive on the first article wherein the cured coating is solid and non-blocking at room temperature. The cured coating on the first article can then be contacted with the second article and heated to a temperature above both the Tg of the adhesive coating and the softening temperature of the hydrocarbon tackifier so as to activate the hydrocarbon tackifier whereby the first article is adhesively affixed to the second article.
DETAILED DESCRIPTION OF THE INVENTION
The adhesive composition of the present invention is a radiation curable precursor coating composition for the preparation of a non-blocking heat activable adhesive and comprises a curable acrylic material, a curable elastomeric material, and a hydrocarbon tackifier material having a softening temperature ranging from approximately 50° C. to approximately 200° C. When the acrylic material and the elastomeric material are cured, the hydrocarbon tackifier remains relatively unchanged and the precursor coating composition is non-blocking and essentially “non-tacky” at room temperature, but when the cured precursor composition is heated to a temperature above the softening temperature of the hydrocarbon tackifier, the hydrocarbon tackifier becomes sticky or tacky but does not melt and the precursor composition becomes adhesive. Upon cooling, a tight adhesive bond can be formed.
The resultant adhesive is resistant to common household detergents, humidity, common solvents, stable against freeze/thaw cycling, heat stable, and can be stored at room temperature.
As described herein, the term “room temperature” is defined as an ambient temperature ranging from between approximately 10° C. and 32° C. but is preferably between approximately 17° C. and 27° C. That is, “room temperature” includes the ambient temperature at which a factory or a warehouse may be commonly maintained.
As defined herein, the term “non-blocking” is defined as the inability of cured adhesive to adhere, at room temperature, to itself, or a substrate upon which it is disposed so as to form a block of relatively solid material which is unusable for its intended purpose. That is, after an article which has been coated with the precursor coating composition of the present invention and then radiation cured, several of these coated articles may be stacked or rolled upon one another without the cured coating adhering to another or an adjacent article.
The term “curing” is typically used as a synonym for cross-linking but can also refer to a combination of additional polyme
Chang David Wen-Lung
Chi Weichen
Chung Mooil
Eadara Rajan
Berman Susan W.
Diversified Chemical Technologies, Inc.
Gifford, Krass, Groh Sprinkle, Anderson & Citkowski, P.C.
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