Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-12-20
2003-11-18
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06649679
ABSTRACT:
FIELD OF THE INVENTION
This invention belongs to the field of emulsion chemistry. In particular, it relates to stable waterborne polymer compositions useful in a variety of adhesive formulations.
BACKGROUND OF THE INVENTION
In an increasing number of industries, aqueous coating compositions continue to replace traditional organic solvent-based coating compositions, as the use of solvents other than water is becoming more and more undesirable due to solvent expense and the cost and hazards involved in controlling solvent vapors. Paints, inks, sealants, and adhesives such as pressure sensitive or laminating adhesives, for example, previously formulated with organic solvents, are now formulated as aqueous compositions. This reduces potentially harmful exposure to volatile organic compounds (VOC's) commonly found in solvent-based compositions. While the move from organic solvent-based to aqueous compositions brings health and safety benefits, loss of one or more physical properties may often result from substitution of waterborne latexes or hot melts for solvent-based polymer systems. Accordingly, the aqueous coating compositions must meet or exceed the performance standards expected from solvent-based compositions. The need to meet or exceed such performance standards places a premium on the characteristics and properties of waterborne polymer compositions used in aqueous coating compositions, such as adhesives.
Waterborne polymers having various functional groups have been used to impart and achieve desired properties to a particular coating composition. For example, a coating composition should exhibit good film formation, print and block resistance, as well as adhesion and tensile properties. Polymers having acetoacetoxy- and enamine-functional groups represent one example of waterborne polymers which have such properties, may carry different functional groups, and are useful in aqueous coating compositions.
For example, U.S. Pat. No. 5,296,530 discloses a quick-curing coating prepared from a polymer having acetoacetyl groups, in which substantially all of the acetoacetyl groups have been converted to enamine functional groups. This conversion occurs, for example, by treatment with ammonia or a primary amine. Coatings so prepared cure more quickly under sunlight or ultraviolet light than coatings which contain the acetoacetyl functional polymer but which have not been converted to an enamine form.
U.S. Pat. Nos. 5,484,975 and 5,525,662 describe the preparation of polymers containing functional acetoacetate groups and then, following the polymerization, reacting the acetoacetate group with a functional amine to form an enamine. The resulting polymers are reported to have a variety of uses including coatings, sealants, adhesives, and saturant applications.
U.S. Pat. No. 5,498,659 discloses polymeric formulations comprising an aqueous carrier, at least one polymeric ingredient, a non-polymeric polyfunctional amine, and a base. The polymeric ingredient has both acid-functional and acetoacetoxy-type functional moieties. The aqueous polymeric formulations produce crosslinked polymeric surface coatings on a substrate.
Japanese Patent Application No. 61-21171 describes a fast-curing adhesive of two separate liquids. The first liquid is an aqueous solution and/or aqueous emulsion of a polymer compound containing an acetoacetyl group. The second liquid consists of polyethylenimine. However, according to this disclosure, in order to achieve fast-curing adhesive properties, the adhesive must be applied as two separate liquids.
U.S. Pat. No. 5,362,816 describes a pressure-sensitive adhesive containing an acetoacetate functional monomer in a low Tg emulsion polymer. The pressure sensitive adhesive is a polymer prepared by free radical emulsion polymerization having a Tg below about 0° C. and has pendent acetoacetate functional groups. The pendent acetoacetate groups are reacted with ammonia or a primary amine to form an enamine-containing composition at a pH greater than 9.
U.S. Pat. No. 5,278,227 describes inherently tacky, emulsion pressure-sensitive adhesive polymers prepared from a specified mixture of monomers. The monomer mixture comprises about 35 to about 65 percent by weight alkyl acrylates, about 15 to about 35 percent vinyl esters, about 20 to about 35 percent by weight diesters of a dicarboxylic acid, and up to about 5 percent by weight of an unsaturated carboxylic acid. The glass transition temperature of the polymer is less than about −30° C.
Even with current waterborne polymer formulations, a need remains for improved aqueous adhesive compositions and waterborne polymers for use in those compositions. In particular, a need exists for waterborne polymer compositions which may formulate as a single, stable composition but which undergo crosslinking upon film formation imparting one or more desired properties to the resulting coating. The present invention meets such needs.
SUMMARY OF THE INVENTION
This invention provides stable waterborne polymer compositions which are stabilized against gelling, comprising a stable waterborne polymer composition comprising an acetoacetoxy-type functional polymer, a poly(alkylenimine), and a nonionic surfactant having a hydrophilic-lipophilic balance (HLB) of at least about 17.5.
These stable waterborne polymer compositions are useful in a variety of coating formulations such as, for example, paints, inks, sealants, and adhesives. When used in coating formulations, the stable waterborne polymer compositions of the invention provide adhesion and crosslinking in the final film or coating. The film or coating may be cured at ambient temperatures or may be thermally cured. Methods of preparing stable waterborne polymer compositions are also disclosed, along with methods of stabilizing latex compositions against gelling upon addition of a poly(alkylenimine).
The stable waterborne polymer compositions according to the invention have beneficial adhesive and shear strength properties. Particularly suitable adhesive compositions comprise a mixture of (a) the stable waterborne polymer composition discussed above and (b) a non-acetoacetoxy functional polymer. In this embodiment, the waterborne polymer composition (a) has a glass transition temperature (Tg) of greater than about 0° C. and the non-acetoacetoxy functional polymer (b) has a Tg of from about 20° C. or lower.
Indeed, it has been discovered that the stable waterborne polymer compositions of the present invention can be used in combination with polymer compositions which lack good shear and/or cohesiveness to provide adhesive compositions with improved shear and cohesiveness. Accordingly, the invention also relates to a method for improving the shear and/or cohesion of an adhesive composition comprising an effective amount of a stable waterborne polymer composition (a).
The adhesive compositions according to the invention are particularly suitable for use as pressure sensitive and laminating adhesives. Accordingly, in another embodiment, the invention relates to pressure sensitive adhesives and laminating adhesives comprising the adhesive compositions of the invention discussed above.
The invention also relates to improved methods employing laminating adhesives and pressure sensitive adhesives. In particular, the invention relates to an improved method for laminating a first substrate to a second substrate comprising applying an adhesive composition to a surface of the first substrate and pressing the surface of the first substrate against the second substrate. The improvement is that the adhesive composition comprises a mixture of (a) a stable waterborne polymer composition having a Tg of greater than about 0° C. and comprising an acetoacetoxy-type functional polymer, a poly(alkylenimine), and a nonionic surfactant having a hydrophilic-lipophilic balance (HLB) of at least about 17.5 and (b) a non-acetoacetoxy functional polymer having a Tg of about 20° C. or lower. Alternatively, the adhesive composition may be simultaneously applied to both substrates while the substrates are press
Raynolds Peter Webb
Scott Duane Allan
Stockl Rebecca Reid
Carrier Michael K.
Eastman Chemical Company
Graves Bernard
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