Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1996-03-15
2001-09-18
Gallagher, John J. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S331400, C524S507000, C525S903000
Reexamination Certificate
active
06290803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a new water-based adhesive formulation. Specifically, a formulation having enhanced characteristics such as excellent adhesion without heat activation. More specifically, it relates to a one-component aqueous sulfonated polyurethane adhesive formulation having enhanced properties for use in applications where use of heat for activation is undesirable or unavailable.
2. Description of the Prior Art
Aqueous polyurethane dispersions have received a great deal of attention recently. These dispersions are compatible with many other water-based polymers, and adhesives made from them usually exhibit improved performance. Examples of these activities can be found in JP 57030776 and JP 83046277. These patents disclose heat curing, water-resistant and stable adhesive compositions comprising dispersions of partially saponified polyvinyl acetate, aqueous solutions of polyurethanes and dispersable polyisocyanate compounds. The adhesive properties of these compositions are generated with a heat curing cycle.
JP 6256749 discloses another adhesive composition prepared by adding polyisocyanate crosslinking agents to a blend of aqueous polyurethane resins and polyvinyl latex. This polyurethane based adhesive composition is reported to exhibit high adhesion, and excellent heat and water resistance.
German Utility Model patent no. 9304018 discloses an adhesive comprising at least a two component polyurethane dispersion having a pot life of 12 hours. This water-based formulation describes a polymer blend of polyurethane dispersions, EVA's or methacrylic derivatives, characterized in that it comprises one essentially non-hydrophobic plasticizer.
A draw back for these prior art compositions is the need for heat activation, making them unsuitable for use where heat for activation is either unavailable or destructive to the substrates or parts being bonded together.
The present inventors have now discovered a one-component sulfonated aqueous polyurethane dispersion based adhesive formulation having excellent adhesive properties, good green strength, solvent resistance, and capable of forming moisture and heat resistant bonds without heat activation.
SUMMARY OF THE INVENTION
The present invention is directed to a novel adhesive formulation comprising plasticized aqueous polyurethane dispersion blends. The formulations of the invention provide excellent adhesion properties upon pressurized joining of coated substrates. This adhesion property, without heat activation, and the unexpected heat resistant properties of the resulting bonds on aging, are believed to be unique properties for polyurethane dispersion adhesive formulations. The inventive adhesive formulations have properties superior to polychloroprene (e.g. Neoprene®) based contact adhesives, have good green strength and moisture resistance and can be spray-coagulated with acids (e.g. by HYDROpHUSE™ process).
The preferred formulations of the invention, when used with a crosslinker, have very long pot-lives, in some cases up to a month or more after addition of the crosslinker. Surprisingly, such formulations even after a month exhibit excellent green strength characteristics without heat activation. This allows formulations containing crosslinking additives to be shipped by the manufacturer as one-component compositions, and provides a substantially improved convenience to the end user.
The applied adhesive films have a useful life or “open time” (time between the making of said films and the using of said films to form the bonded structure) ranging from about an hour to a few hours, depending on the composition of the dispersion and the crosslinkers chosen.
The invention is also directed to the use of the inventive formulations as adhesives and to an adhesively bonded structure comprising said formulation as the adhesive.
The inventive adhesive formulations comprise:
a) at least one hydrophobic plasticizer, for instance a member of the group consisting of alkyl and aryl sulfonamides, benzoate esters, phthalate esters, adipates, citrates, and mixtures thereof; and
b) an aqueous polyurethane dispersion blend comprising:
1) at least one hard sulfonated polyester urethane;
2) at least one soft non-sulfonated polyester urethane; and
3) at least one polar non-polyurethane water-based polymer or copolymer.
A high molecular weight non-sulfonated polyurethane polymer and/or a crosslinker, such as a dispersable polyisocyanate crosslinker, are optional components employed in preferred embodiments of the invention.
The invention also relates to a polyurethane dispersion based adhesive formulation containing an interpenetrating network having crosslinked matrixes for improved heat, moisture and solvent resistance, and to the process of manufacture and use of the same.
DETAILED DESCRIPTION OF THE INVENTION
In the inventive adhesive formulations an aqueous polyurethane dispersion blend is employed which includes at least one “hard” sulfonated polyester urethane, at least one “soft” non-sulfonated polyester urethane; and at least one polar non-polyurethane water-based polymer or copolymer.
The “hard” sulfonated polyester polyurethane is a relatively high molecular weight anionic sulfonated polyester urethane polymer which is characterized by a shear storage modulus (G′) having a value of from about 10
9
to about 10
10
dynes/cm
2
at 25° C. and a frequency of 10 radians/sec. The relatively high molecular weight, polyurethane useful as the hard polyurethane in the aqueous polyurethane dispersion blends of the present invention can be linear aliphatic, cyclic aliphatic, or aromatic sulfonated polyester urethanes, preferably formed from at least one sulfonated polyamine or polyol and one or more diisocyanates. A suitable example of such a sulfonated polyester polyurethane dispersion is Dispercoll™ KA-8464, sold by Mobay Corporation, Pittsburgh, Pa. The hard polyurethane dispersion solids may comprise from about 15 parts to about 35 parts, preferably from about 20 parts to about 30 parts, based on 100 parts total solids.
The “soft” non-sulfonated polyurethane component of the inventive blends is a relatively low molecular weight polyurethane polymer characterized by a shear storage modulus (G′) having a value of from about 10
6
dynes/cm
2
to about 10
8
dynes/cm
2
at 25° C. and 10 radians/sec. It can be formed from linear aliphatic, cyclic aliphatic, or aromatic non-sulfonated polyester urethanes, preferably formed from diisocyanates such as isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tetramethylxylylene diisocyanate (TMXDI), and mixtures thereof. Such polymers are tacky and give the final adhesive composition added tack and improved initial green strength characteristics. The soft polyurethane dispersion solids are present from about 15 parts to about 35 parts and preferably from about 20 parts to about 30 parts, based on 100 parts total solids.
The blended dispersion also includes a polar, non-polyurethane water-based polymer or copolymer component. Addition of at least one such polar, water-based polymer or copolymer can improve the sprayability of the dispersion. Examples of these polymers or copolymers include vinyl acetate-ethylene copolymers, acrylic polymers, vinyl acetate polymers and other vinyl polymers. The polar, non-polyurethane water-based polymer or copolymer solids comprise from about 5 parts to about 40 parts, and preferably from about 5 parts to about 15 parts, based on 100 parts total solids.
The inventive formulations also include a hydrophobic plasticizer. The hydrophobic plasticizers enhance the water resistance properties of the adhesive. They can be selected from the group consisting of alkyl and aryl sulfonamides, benzoate esters, phthalate esters, adipates, citrates, and mixtures thereof. Particularly preferred are alkyl sulfonamides, aryl sulfonamides, alkylene glycol benzoates, dialkylene glycol benzoates, and mixtures thereof. The amount of plasticizer present in the adhesive composition can vary from about 1 par
Dochniak Michael
Haider Gary
Jannusch Leonard
Maksymkiw Mike
Wade Paul
Gallagher John J.
H. B. Fuller Licensing & Financing Inc.
Quan Nancy
LandOfFree
Bonding method for water-based formulations having enhanced... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bonding method for water-based formulations having enhanced..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bonding method for water-based formulations having enhanced... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2469985