Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-07-27
2002-08-13
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C424S059000, C424S061000, C424S063000, C424S064000, C424S069000, C424S070100, C424S070700, C424S070110, C424S078370, C424S401000, C424S405000, C524S839000, C524S840000, C528S071000
Reexamination Certificate
active
06433073
ABSTRACT:
TECHNICAL FIELD
The present invention pertains to a cold seal adhesive composition in the form of a stable polyurethane dispersion in alcohol-water system.
BACKGROUND
Polyurethane is a generic term used to describe polymers prepared by the reaction of a polyfunctional isocyanate with a polyfunctional alcohol to form urethane linkages. The term “polyurethane” has also been used more generically to refer to the reaction products of polyisocyanates with any polyactive hydrogen compound including polyfunctional alcohols, amines, and mercaptans. Polyurethanes are used in a variety of applications including as elastomers, adhesives, coatings, and impregnating agents.
For coating applications, polyurethane polymers can be dispersed in water by incorporating stabilizing groups into their backbone. Anionic, cationic, and non-ionic dispersion stabilizing groups have been used. Various aqueous polyurethane dispersions have been prepared by those skilled in the art. For example, U.S. Pat. No. 3,479,310 (Dieterich et al.) discloses water-dispersed polyurethane polymers suitable for use as waterproof coatings. The polymer is prepared from polyhydroxy compounds, polyisocyanates, optional chain lengthening agents, and a sufficient amount of a component having an ionic salt-type group. U.S. Pat. No. 4,307,219 (Larson) discloses water dispersible polyurethane resin prepared by reaction of hydrophilic diols, hydrophobic diols, diisocyanates, and, optionally, chain extenders. Such a urethane resin can be used as protective coatings, primers, and binders.
Although aqueous dispersions of polyurethanes have been widely disclosed, the inventors are not aware of any references to stable polyurethane dispersions in alcohol-water solvent systems, particularly in the absence of hydrophilic stabilizing moieties. Stable polyurethane dispersions in hydro-alcohol (i.e., alcohol-water) systems are especially difficult for at least two reasons.
First, the addition of lower alcohols (e.g., C
1
to C
4
) to water decreases the surface tension of the solvent system. For example, a 40% by weight ethanol in water system has a surface tension of about 31 dyne/cm compared to a pure water system, which has a surface tension of about 72 dyne/cm at about 20° C. A 60% by weight ethanol in water system has a surface tension of 27 dyne/cm at about 20° C. The reduction in surface tension can affect the ability to self assemble hydrophilic and hydrophobic domains during the dispersion preparation. Secondly, many of the polyurethane components (i.e., the starting reactants) are soluble in hydro-alcohol solvent systems, which result in solutions and not dispersions. Polymer solutions have substantially higher viscosity than polymer dispersions, making the solutions harder to process in certain operations, such as coating and spraying operations. Polymer solutions also tend to achieve lower percent solids when compared to polymer dispersions, making the former less attractive during coating operations and during shipping. Lower solids solutions also require longer drying times than dispersions both because of the greater amount of solvent present and the higher affinity of the polymer for that solvent. Furthermore, the molecular weight of soluble polymers is often much lower than that of dispersions.
U.S. Pat. No. 4,507,430 (Shimada et al.) discloses a water-based polyurethane emulsion that comprises a hydrogenated polyalkadiene polyol component and a polyisocyanate component. Shimada discloses that the materials are useful as an adhesive or coating material for a polyolefin resin, and can be applied wet and dried or bonded by dry lamination requiring heat and pressure. There was no disclosure of polyurethane dispersions in hydro-alcohol solvent system.
U.S. Pat. No. Re. 34,730 (Salatin et al.) discloses waterborne basecoat compositions comprising (a) an anionic polyurethane resin comprised of (i) a polyester resin component produced by reaction of a carboxylic acid component comprised of at least 50% by weight C
18-60
long chain acid and a polyol and (ii) a mixture of at least one multifunctional compound having at least one active hydrogen functionality and at least one carboxylic acid functionality neutralized with an amine, (b) a polyisocyanate combined with a crosslinking agent, and (c) a rheology control agent. U.S. Pat. No. 5,326,815 (Serdiuk et al.) discloses a coating composition comprising (a) an aqueous medium, (b) a water-dispersible polyurethane resin that is the reaction product of (i) a hydroxy-functional polyester resin component that is the reaction product of a carboxylic acid component comprising at least two carboxylic acids, a C
36
dimer fatty alcohol, and a short-chain polyol, (ii) a multifunctional compound having at least one active hydrogen group and at least one water-stabilizing group, (iii) an active hydrogen-containing capping or chain extending agent, and (iv) a polyisocyanate, and (c) an aminoplast crosslinking agent. The active hydrogen-containing capping agent is used in excess to terminate the isocyanate functional prepolymer, providing terminal hydroxyl groups for reaction with the crosslinking agent. Other patents describing the use of dimer fatty alcohols or polyesters derived from dimer acid in waterbased polyurethane dispersions for basecoat compositions include U.S. Pat. No. 4,423,179 (Guagliardo), U.S. Pat. No. 5,334,650 (Serdiuk et al.), and U.S. Pat. No. 5,370,910 (Hille et al.). None of the above references disclose a polyurethane dispersion in alcohol-water system.
U.S. Pat. No. 5,672,653 (Frisch et al.) discloses an anionic waterborne polyurethane dispersion prepared by (a) forming a prepolymer from hydroxy terminated polybutadiene resin, an aliphatic isocyanate, and a diol containing acid groups; (b) neutralizing the acid; dispersing it in water; and (c) chain extending the prepolymer with a diamine.
Cold seal properties in adhesives have been discussed by those skilled in the art. For example, U.S. Pat. No. 5,616,400 (Zhang) discloses a sheet material coated with a dry cold seal adhesive consisting essentially of the reaction product of 50 to 80% polyester polyol, 15-25% aliphatic diisocyanate, and 3 to 6% dimethylol propionic acid neutralized with a base, said reaction product having a T
g
between about −20° and 5° C. U.S. Pat. No. 5,981,650 (Zhao et al.) discloses an aqueous cold-seal adhesive dispersion containing 30% to 55% of a polyurethane ionomer with a T
g
between −50° C. and 10° C., which is the reaction product of a polyester polyol and polyether polyol blend, an aliphatic diisocyanate, and dimethylol propionic acid, with 0.05% to 4% colloidal amorphous silica reacted in situ with an organic NCO containing moiety. The use of an alcohol insoluble oligomeric diol is not disclosed in these patents, nor is the importance of controlling molecular weight through the use of chain terminators to give cold seal adhesive properties.
Water-soluble or water-dispersible polyurethanes have been disclosed for use in cosmetic formulations. EP 656,021 B1 (Son et al.), WO 96/14049 (Emmerling et al.), U.S. Pat. No. 5,643,581 (Mougin et al.), U.S. Pat. No. 5,874,072 (Alwattari et al.), U.S. Pat. No. 5,972,354 (de la Poterie et al.), WO 99/43289 (Ohta et al.), EP 938,889 A2 (Son et al.), and U.S. Pat. No. 5,968,494 (Kukkala et al.) are representative. None use oligomeric alcohol insoluble polyactive hydrogen compounds, such as oligomeric alcohol insoluble diols, in preparing the polyurethane.
None of the technologies discussed above recognize the importance of controlling molecular weight through the use of chain terminators to give cold seal adhesive properties, nor do they suggest the use of these materials in cosmetic or medical formulations.
A need exists in the art for polyurethane dispersions stable in alcohol-water solvent systems, where the dispersion has one or more of the following properties: capable of forming stable dispersions in hydro-alcohol systems, capable of rapidly forming films on skin or hair by simple ambient evaporation, and capable of achieving high
Kantner Steven S.
Lewandowski Kevin M.
Scholz Matthew T.
3M Innovative Properties Company
Sergent Rabon
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