Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-11-24
2001-08-14
Henderson, Christopher (Department: 1713)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C106S316000
Reexamination Certificate
active
06273989
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is directed to three-dimensional polymeric adhesive materials and methods for producing such materials.
During the past quarter century, the rapid growth of the electronic circuits industry has resulted in the development of higher performance construction materials. However, the development of high performance adhesive materials and systems to bond the construction materials together has not kept pace. This lack of higher performance adhesive materials is particularly felt in the assembly of electronic components for use in severe environmental conditions, such as under-the-hood automotive and military applications. Adhesive materials and systems that are currently available meet some of the requirements for such properties as peel strength, chemical resistance, moisture resistance, high temperature stability, dimensional stability, especially in the Z-axis direction, and ease of processing. However, these materials and systems typically fail to meet one or more of these requirements. Therefore, a need exists for an adhesive material that meets all of the requirements for use under severe environmental conditions while retaining ease of application.
SUMMARY
We have developed a three-dimensional adhesive material and a process for preparing it that meets these needs and provides an improved adhesive for use under severe environmental conditions, particularly in the assembly of electronic components.
One aspect of the present invention is a process for producing a three-dimensional polymeric adhesive material. The process comprises:
(1) reacting a starting polymer containing an active hydrogen or hydroxy function with a polyfunctional nucleophile to form an adduct product; and
(2) reacting the adduct product with a polyelectrophile to generate a three-dimensional polymeric adhesive material.
The starting polymer can contain an active hydrogen and have a maximum acid value of 2. Such a starting polymer can be selected from the group consisting of polycarboxylic acids, polyesters, polyamides, polyacrylics, polyfunctional phenolic resins, and mixtures thereof. Preferably, in this alternative, the starting polymer is a high molecular weight polyester.
Alternatively, the starting polymer can be a polyfunctional hydroxy-containing polymer having a hydroxy number of at least 10. Preferably, the polyfunctional hydroxy-containing polymer is selected from the group consisting of polyols, polyesters, polyurethanes, and mixtures thereof.
Preferably, the polyfunctional nucleophile is a polyfunctional nitrogen-containing compound. More preferably, the polyfunctional nitrogen-containing compound is selected from the group consisting of polyamines, polyaziridines, polyisocyanates, and mixtures thereof. Most preferably, the polyfunctional nitrogen-containing compound is a polyisocyanate.
Preferably, the polyelectrophile comprises at least one polyepoxide. More preferably, the polyepoxide is selected from the group consisting of bisphenol A-epichlorohydrin epoxies, novolac epoxies, and mixtures thereof. Most preferably, the polyexpoxide comprises a mixture of bisphenol A-epichlorohydrin epoxies and novolac epoxies.
Preferably, when the polyelectrophile comprises at least one polyepoxide, the step of reacting the adduct product with the at least one polyepoxide comprises heating a mixture of the adduct product and the at least one polyepoxide to a temperature between about 250° F. and about 400° F.
Preferably, when a high molecular weight polyester and at least one polyepoxide are used to form the three-dimensional polymeric material, the high molecular weight polyester comprises from about 50% to about 90% by weight of the three-dimensional polymeric adhesive material and the polyepoxide comprises from about 10% to about 50% by weight of the three-dimensional polymeric adhesive material.
Another aspect of the present invention is a process for bonding at least two substrates. The process comprises the steps of:
(1) reacting a starting polymer containing an active hydrogen or hydroxy function with a polyfunctional nucleophile to form an adduct product;
(2) mixing the adduct product with a polyelectrophile to generate a bonding precursor;
(3) applying the bonding precursor between the substrates prior to the reaction between the adduct product and the polyelectrophile; and
(4) reacting the adduct product with the polyelectrophile to generate a three-dimensional polymer adhesive material between the substrates, thereby bonding the substrates.
Typically, the substrates are selected from the group consisting of film substrates, foil substrates, and hardboard substrates.
Another aspect of the present invention is a three-dimensional adhesive produced by the process described above. In general, the adhesive comprises:
(1) at least two linear polymer moieties, each moiety comprising a polymer containing nucleophilic nitrogen atoms capable of reaction with an electrophile; and
(2) cross-links between the nitrogens of the polymer moieties, each cross-link comprising a polymer linked to the nitrogen atoms of the polymer moieties through reaction of an electrophile with the nitrogen atoms.
Preferably, the linear polymer moieties are selected from the group consisting of polycarboxylic acids, polyesters, polyamides, polyacrylics, polyfunctional phenolic resins, and mixtures thereof.
Preferably, the linear polymer moieties are formed by reaction of a hydroxy-containing polymer with a polyfunctional nitrogen-containing nucleophile.
Preferably, the polyfunctional nitrogen-containing nucleophile is selected from the group consisting of polyamines, polyaziridines, polyisocyanates, and mixtures thereof.
One preferred version of the three-dimensional polymeric adhesive of the present invention comprises:
(1) at least two linear urethane linked polymer moieties, each moiety comprising a hydroxy-terminated polyester linked in urethane linkage by an aromatic isocyanate; and
(2) cross-links between the nitrogens of the urethane linked polymer moieties, each cross-link comprising a phenyl-containing polymer linked to the nitrogen atoms of the urethane linkages by —CH
2
—CHOH—linkages, with the methylene groups of the linkages being bonded directly to the nitrogen atoms such that the cross-links form a three-dimensional polymeric structure.
In this version, the cross-links preferably comprise at least one polyepoxide selected from the group consisting of bisphenol A-epichlorohydrin epoxies, novolac epoxies, and mixtures thereof.
More preferably, the polyepoxide comprises a mixture of bisphenol A-epichlorohydrin epoxies having the formula
and novolac epoxies having the formula
wherein n is an integer from 1 to about 20, n being independently chosen for the bisphenol A-epichlorohydrin epoxies and for the novolac epoxies.
The adhesive material of the present invention can be used to bond at least two substrates, thereby forming a composite structure. A composite structure formed according to the invention comprises:
(1) at least two bondable substrates; and
(2) a three-dimensional polymeric adhesive material in adhesive contact with each of the substrates such that each of the substrates is bonded to at least one other substrate by the adhesive material, the adhesive material comprising:
(a) at least two linear polymer moieties; each moiety comprising a polymer containing nucleophilic nitrogen atoms capable of reaction with an electrophile; and
(b) cross-links between the nitrogens of the polymer moieties, each cross-link comprising a polymer linked to the nitrogen atoms of the polymer moieties through reaction of an electrophile with the nitrogen atoms.
DESCRIPTION
I. The Adhesive Production Process
One aspect of the present invention is a process for producing a three-dimensional polymeric adhesive material. The polymeric adhesive material produced by this process has improved peel strength, chemical resistance, moisture resistance, high temperature stability, and dimensional stability. It is easy to process and is particularly suitable for use with electronic construction mat
Gardeski Thomas F.
Novak Diane
Anderson Denton L.
Henderson Christopher
Sheldon & Mak
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