MXPA00005450A

MXPA00005450A - Waterborne polyurethanes with urea-urethane linkages

Info

Publication number: MXPA00005450A
Application number: MXPA/A/2000/005450A
Authority: MX
Inventors: Ramalingam Balasubramaniam
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1997-12-04
Filing date: 2000-06-02
Publication date: 2001-07-03

Abstract

Waterborne polyurethanes possessing urea-urethane linkages that are not separated by any intervening carbon atoms may be obtained by using hydroxylamine as a chain extender. Isocyanate-terminated prepolymer possessing ionized or easily ionizable groups is reacted with NH2OH to form a polyurethane possessing urea-urethane linkages corresponding to formula (I). The waterborne polyurethanes are useful in adhesive, coating and ink formulations and in the flexible package industry.

Description

POLYURETHANES COATED IN WATER WITH UREA-URETANQ LINKS FIELD OF THE INVENTION This invention relates to waterborne polyurethanes having urea-urethane linkages not separated by carbon atoms intervening, to a method for preparing the polyurethanes carried in water and to adhesive compositions, of coating and ink containing polyurethanes carried in water. Waterborne polyurethanes exhibit excellent mechanical strength and adhesion on a wide range of substrates and can be used in the flexible packaging industry. BACKGROUND OF THE INVENTION The commercial utility of polyurethanes in general and of aqueous polyurethane dispersions in particular is due substantially to the ability of urethane groups in the sense of allowing hydrogen bonds. In addition to improving mechanical strength, urethane groups promote adhesion on many substrates by virtue of their ability to exhibit hydrogen bonding. The processes for making the polyurethanes carried in water are well known. A review of the chemical syntheses of waterborne polyurethanes and of patents and relevant publications in this field can be found in Advances in Poiyurethane Science and Technology, Technomic Publishing Co., Inc., Lancaster, PA. , United States of America, volume 10, pages 121-162, whose contents are incorporated herein by reference. The polyurethanes carried in water are obtained by first preparing a prepolymer having ionized groups or easily ionizable groups and reactive isocyanate groups. The prepolymer is produced by the reaction of a polyhydroxy compound such as, for example, polyether, polyester, polycarbonate, and the like, having at least two hydroxyl groups reactive with a stoichiometric excess of an aliphatic, aromatic or cycloaliphatic polyisocyanate having at least two isocyanate groups and an organic compound having at least two active hydrogens and at least one ionized or easily ionizable group. The organic compound reacts with the polyhydroxy compound and the polyisocyanate compound to produce an isocyanate-terminated prepolymer containing ionized or easily ionizable groups in the prepolymer structure. In a second step, the length of the prepolymer chain is extended by the reaction of the isocyanate end groups with difunctional or polyfunctional agents and the resulting polyurethane is dispersed in water by neutralization or removal of the ionized or easily ionizable groups. The chain extension reaction is a crucial step. In order to obtain polyurethane dispersions possessing useful physical properties, the polymer must have an optimum molecular weight. The ability of the isocyanate groups to react relatively easily with water makes the chain extension step a competition reaction. Care must be taken to control the course of the reaction. The reactivity of the isocyanate, the chain extension agent, the hydrophilicity of the polymer structure, concentration, temperature and mechanical conditions such as the speed of mixing play an important role. A chain extension approach includes the use of aliphatic diamines that react several orders of magnitude faster than water. Examples of such amines include ethylenediamine, isophoronediamine, and the like. A problem with the diamine chain extenders is that the diamines exhibit a very high reactivity and cause a rapid increase in molecular weight which in turn adversely affects the dispersion capacity of the resulting polyurethane. Another approach includes the blocking of the isocyanate groups with easily isociable functionalities such as oximes and then their thermal unblocking for chain extension. Initially, a good dispersion is produced and the molecular weight is increased. U.S. Patent Nos. 4,240,942, 4,387,181 and the references cited therein describe such methods. However, said unblocking reactions often produce undesirable small volatile compounds such as aldehydes or ketones. Another approach includes the use of hydrazine as a chain extension agent. It is known that the resulting polyurethanes have better mechanical properties compared to polyurethanes produced from extended diamine chain systems. However, the carcinogenicity associated with hydrazine and its derivatives limits its use in sensitive areas. Another approach includes the use of hydrogen peroxide as a chain extender. However, the resulting polyurethanes decompose to slightly elevated temperatures.

In addition, hydrogen peroxide can be used only in water and can not be added directly as part of the polyol composition during prepolymer formation since hydrogen peroxide is unstable in the temperature range. Likewise, the reactivity of hydrogen peroxide in its two terminals is the same. Organic hydroxylamine compounds, such as for example aminoethanol, the aminopropanols, the aminobutanoles, the aminohexanols, the inodecanols, the methylethanolamine, the aminocyclohexanols, the indobenzyl alcohol, and the like have been presented as chain extenders in polyurethane synthesis. See US Pat. Nos. 2,871,227, 3,939,126, 4,066,591 and 5,155,163. However, it is believed that the inorganic hydroxylamine, ie, NH 2 OH, has not been used to date for the synthesis of polyurethanes carried in water. The use of inorganic hydroxylamina as a chain extender results in the formation of urea-urethane linking groups that are not separated by any intervening carbon atoms. In contrast, the use of organic hydroxylamine compounds such as for example ethanolamine results in the formation of linking groups in which the urea groups and urethane groups are separated by carbon atoms. The urea-urethane linking groups obtained through the use of inorganic hydroxylamine confer special properties to the polyurethane of this invention as will be discussed in more detail below. COMPENDIUM OF THE INVENTION This invention relates to an aqueous dispersion of polymers comprising a polyurethane containing a plurality of urea-urethane bonds corresponding to the formula: 0 or 1! -NH-C-HN-O-C-NH- and a process for the preparation of the aqueous dispersion of polymers comprising the reaction of an isocyanate-terminated prepolymer having ionized or easily ionizable groups with hydroxylamine for forming a polyurethane containing a plurality of bonds corresponding to the formula: 0 O 1 I -NH-C-HN-O-C-NH-.

The dispersions of this invention are stable and homogeneous and contain polyurethane resins having excellent physical, chemical, and dispersion or emulsion properties. The polyurethane dispersions obtained according to the present invention are known as self-dispersible emulsions, which do not contain an emulsifier. However, known emulsifiers can also be added to the dispersion of the present invention in order to further improve the stability of the dispersions, provided that the amount of the emulsifier employed does not adversely affect the properties of the polyurethane polymer or the adhesion properties. of the dispersion. The present invention also features the use of aqueous polyurethane dispersions, either by itself or with other reactive and / or non-reactive chemical additives for adhesive, coating and ink applications. The present invention further discloses new flexible packages comprising several flexible substrates bonded together by an adhesive comprising a polyurethane containing several bonds corresponding to the formula: 0 O 1 I -NH-C-HN-O-C-NH- In addition, the invention provides a method for forming flexible packages comprising the supply of an adhesive comprising an aqueous dispersion of a polyurethane containing a plurality of bonds corresponding to the formula: \ O O I I -NH-C-HN-O-C-NH-, ^ providing at least one flexible substrate, applying a layer of the adhesive on at least one selected section of the substrate and forming at least one junction between the selected section of the substrate and another section of the same substrate or of a different substrate by sandwiching the adhesive between them. All the amounts presented here, except in the examples, should be understood as modified by the term "approximately". DESCRIPTION OF THE PREFERRED MODALITIES The chain extension agent used in the practice of the present invention is hydroxylamine, ie NH2OH (CAS 7803-49-8). This compound is readily soluble in water and available in the form of the free amine or as its acid salts. It can be released from the latter by treatment with ammonia or the like. Since one end of the hydroxylamine is the amino functional group, a rapid reaction with isocyanates occurs. The other end of hydroxylamine is a primary hydroxyl functional group and, even though it has a slower reaction than the amino terminus, it continues to react more rapidly than water. (A list of relative reactivity can be found in the Encyclopedia of Chemical Technology, Kirk-Othmer, 3rd edition, volume 13, page 213). The difference in reactivity between the amino and hydroxyl end groups of 17a hydroxylamine allows sufficient time to be obtained for the formation of a better dispersion that can subsequently be extended through the hydroxyl end, however, the undesirable reaction with water is avoided in an essential way. If desired, the reaction can be carried out in such a manner that only the amino end group of the hydroxylamine reacts. (Industrial Organic Nitrogen Compound, Reinhold Publishing Corporation, New York, page 290). The hydroxyl end group can be further reacted with a second component such as, for example, melamines, epoxies, titanates or organic zirconates. The unique structure of hydroxylamine allows the formation of extensive sites of hydrogen bonding in the resulting polyurethanes. The process of chain elongation through hydroxylamine can be represented as follows: O C N N C O H, N O H 2 where Ri represents the structure of an isocyanate-terminated prepolymer, the structure contains ionized or easily ionizable groups (not shown) and n is from 1 to about 20, preferably from 1 to about 4. It can be seen that a polyurethane is provided which has a plurality of urea-urethane bonds that are not separated by any carbon atom intervening. In each of these links, the potential for hydrogen bond or positive ion association exists. The isocyanate-terminated prepolymer is prepared by the reaction of an organic isocyanate compound with a polyol or a mixture of suitable polyols, and an organic compound containing at least two active hydrogens and at least one ionized or easily ionizable group in solvent (s). ) inert organic (s) fs) which can easily solubilize the reactants at the suitably high concentration and at the required reaction temperature. Suitable solvents include l-methyl-2-pyrrolidone, acetone, methyl ethyl ketone and the like. The total amount of the solvent that is used for the synthesis is within the range of from about 0 to about 25, preferably from about 0 to 10, more preferably from about 0 to about 5% by weight, based on the weight of the prepolymer The amount of organic solvent that is used in the synthesis of isocyanate-terminated prepolymer depends on the concentration of the reactant and the reaction temperature. The reaction is carried out at a temperature that is within the range of about 20 to about 150 ° C, for a period of time from about one half hour to about four hours, depending on the temperature of the reaction and the reactivity of the reagents Preferably, the temperature of the reaction is within the range of about 50 to about 70 ° C, and the reaction time period is from about 1 hour to about 2 hours. The preferred organic isocyanate compounds (aromatics, aliphatics or cycloaliphatics) are polyisocyanates containing at least two isocyanate groups. Suitable diisocyanates that can be employed in this invention include aromatic, aliphatic or cycloaliphatic diisocyanates, such as, for example, 4,4'-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate and 2,6-toluene (TDI), ditolyl diisocyanate (TODI), 1,5-naphthalene diisocyanate, diisocyanate 4-dibenzyl, m- or p-xylene diisocyanate, 1,3-phenylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethylene diisocyanate , and similar. The polyol can be any of a wide range of oligomeric or polymeric polyols, with polyester, polyether, polycarbonate or caprolactone-based polyols containing at least two hydroxyl groups being preferred. In one embodiment of the present invention, the polyols are crystalline with a crystalline melting point or melting range of from about 30 ° C to about 100 ° C, preferably from about 0 ° C to about 70 ° C. The polyol may have a slow or rapid crystallization rate but moderate to fast crystallization rates are preferred. Amorphous or non-crystalline polyols as well as mixtures of crystalline and amorphous polyols can also be used, however. The polyols employed in this process include polyols that are predominantly linear and having a molecular weight that ranges from about 300 to about 5,000, preferably from about 1,000 to approximately 2,000. Particularly preferred polyols include polyether polyols including thioethers, polyester polyols including hydroxyl-containing polyhydroxypoliesteramides and polycaprolactones as well as hydroxyl-containing acrylic interpolymers. Any suitable polyether polyol can be employed including those having the following general structural formula: where the substituent R is hydrogen or mixed substituents including lower alkyl, and n is typically from 2 to 6 and m is from 2 to 100 or even more. Poly (oxytetramethylene) glycols, poly (oxyethylene) glycols, polypropylene glycols and the products of the reaction of difunctional alcohols with propylene oxide and ethylene oxide (either as a mixture, to form substantially random copolymers, or sequentially to form copolymers) are included. of blocks or segmented). Also useful are polyether polyols formed from the oxyalkylation of various polyols, for example, glycols such as ethylene glycol, 1,6-hexanediol, bisphenol A, and the like, or higher polyols, for example trimethylolpropane, pentaerythritol, and the like. Polyols of higher functionality that can be used as indicated can be made, for example, by the oxyalkylation of compounds such as sorbitol or sucrose. One oxyalkylation method commonly employed is by reacting a polyol with an alkylene oxide, for example, ethylene or propylene oxide, in the presence of a double-acid or basic metal cyanide complex catalyst. The organic compound having at least two active hydrogens and at least one ionized or easily ionizable group is known and is presented, for example, in U.S. Patent No. 4,066,591, the content of which is incorporated herein by reference. Preferred organic compounds include amine or diol compounds containing carboxyl groups capable of forming salts. These organic compounds contain at least two amines or two hydroxyl groups, and at least one comparatively unreactive carboxyl group in a lateral or terminal position, either in the salt form or in a form capable of forming salts by neutralization with a adequate base or a salt-generating agent. Such compounds include alpha, alkanedimethylol alkanoic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolpentanoic acid, and the like. A preferred alpha, alkanedimethylolalkanoic acid is 2,2-dimethylolpropionic acid (DMPA). Catalyst compounds that can be used to facilitate the reaction of prepolymers include organotin compounds or tertiary amine compounds. The reactions to form the prepolymer can be carried out with or without a catalyst. The preferred catalyst compounds for the reaction are organotin compounds; Dibutyltin dilaurate is especially preferred. The bases employed in this invention to convert the ionized or easily ionizable groups into their respective salts by neutralization of the groups, are either organic bases or inorganic bases. Suitable bases employed in this invention are organic compounds containing basic tertiary amines which can neutralize carboxylic groups. Examples are N-alkyl dialkanolamines (e.g., N-methyldiethanolamine), N-N-dialkylalkanolamines (e.g., N-N-diethylethanolamine), trialkylamines (e.g., triethylamine), and the like, the preferred base is triethylamine. The base can be added to the reaction medium containing the prepolymer in a temperature range from about 30 to about 90 ° C, more preferably from about 40 to about 70 ° C. The ionic groups formed provide self-emulsifying properties to the polyurethane. The amount of ionic or easily ionizable groups in the polymer chain is within the range of about 10 to about 100 milliequivalents per 100 grams of the polymer, more preferably within the range of about 30 to about 60 milliequivalents per 100 grams of the polymer. Water is added to the prepolymer under vigorous stirring conditions to form a dispersion. The water temperature can be within a range of about 20 ° C to about 100 ° C, more preferably water is used at room temperature. The present solvent can be removed, if desired, by distillation from the final aqueous dispersion. For chain extension of the prepolymer, hydroxylamine is added to the reaction medium containing prepolymer before, during or after the reaction step of the prepolymer with the base. Preferably, the dispersion and chain extension reactions are carried out simultaneously by mixing hydroxylamine and the base used for the salt formation with the water and by adding these materials to the reaction medium containing prepolymer. When the hydroxylamine level is below the stoichiometric amount required to react with the free isocyanates, foaming may be observed during the strand / chain extension step as a result of reactions between free isocyanate groups and water. This can be overcome by the addition of a foam remover to the reaction medium containing the prepolymer prior to dispersion or during or after the dispersion / chain extension process. The polyurethane dispersion obtained in this way can be diluted with water in order to obtain the required percentage levels of solids. The aqueous polyurethane dispersions obtained by the process of the present invention may contain up to about 60% solids and the viscosity of the emulsion may be within a range of about 10 to about 200 centipoise or more. If necessary, the viscosity of the emulsion can be adjusted using a suitable thickener to provide a stable viscosity that will not present interference with the properties of the dispersion. The thickener will typically be one of two types, i.e., a water soluble gum or an associative thickener. The precise levels of the thickener in the dispersion will vary according to the nature and efficiency of the thickener and the desired viscosity of the dispersion, but will generally be within a range of from about 0.1% to about 10%, based on the total weight of the system. thicken, more typically from about 0.1% to about 5%. The viscosity of the dispersions without adding thickener will typically be within a range of 10 to 200 centipoise. The amount of thickener will typically be sufficient to provide the dispersion with a viscosity greater than 100 centipoise, for example, from about 150 centipoise to about 5,000 centipoise. Water-soluble gums are described in the Encyclopedia of Polymer Science and Engineering, volume 7, pages 589-613 (John Wiley & amp; amp; amp;; Sons, Inc., N.Y., N.Y. 1987), the disclosure of which is incorporated herein by reference. These materials are high molecular weight polymers, typically polysaccharides, which are soluble in water. and present a thickening activity by polymer chain entanglement. Examples of such polymers include hydroxyethylcellulose and carboxymethylcellulose. Synthetic polymers that exhibit a thickening activity also by chain entanglement are also available. Examples include acrylic polymers swellable with alkaline elements, for example copolymers of low alkyl acrylate esters (for example methyl, ethyl or butyl) with acrylic or methacrylic acid. These polymers typically thicken the water at a neutral or alkaline pH, for example, a pH greater than about 6. The associative thickeners are so named because the mechanism by which they can thicken may involve hydrophobic associations between the hydrophobic species in the thickener molecules and other hydrophobic surfaces, either in other thickener molecules or in molecules in the system to be thickened. The different types of associative thickeners include, but are not limited to, hydrophobically modified polyurethanes, hydrophobically modified polyethers, emulsions soluble in hydrophobically modified alkaline agents, hydrophobically modified hydroxyethylcellulose or other products and hydrophobically modified polyacrylamide. The molecular weight and HLB of these associative thickeners, usually water-soluble or water-dispersible polymers, are chosen in such a way that they are high enough to provide the desired rheological properties to an aqueous composition containing the thickener. Typically, the polymer has a structure such that a solution containing up to 2-3% by weight of this polymer will have a viscosity of at least 5,000, preferably at least 15,000, and more preferably at least 2,000 centipoise (in accordance with the measurement in a Brookfield viseometer with a spindle number 3 at 10 RPM at a temperature of 25 ° C). The aqueous polyurethane dispersions obtained have particles of an indicated size within a range of about 10 nm to about 10 microns, preferably within the range of about 0.05 mm to about 1 mm, and more preferably within the range of about 0.1 mm. Look at about 0.5 miera. The sizes of the particles can vary according to the reactants and the reaction parameters. The molecular weight of the polymers is generally within a range of about 5,000 to about 15,000 according to the parameters of the reaction and according to the chain extension reaction. Dry polymer films frequently exhibit melting and / or glass transition temperatures. Melting peaks can generally occur within a range of about 30 to about 100 ° C, glass transition temperatures are within a range of about -50 ° C to about -10 ° C. These dispersions can be used directly, without other additives, for adhesive, coating or ink applications. Other onents can be added to the polyurethane dispersions for formulation for a particular application, for example, thickeners, fillers, pigments, wetting agents, foam removers, and the like. In applications where high thermal resistance and / or high moisture resistance is required, the polyurethane dispersion can be mixed with ounds that can react with the polymer to form a crosslinked polymer. { thermosetting). These reactive ounds can be mixed with the dispersion before application. The reaction may occur in the polymer film - during the film drying process or at the time of heat application to the polymer coating. The cross-linking of the polyurethane causes better thermal, moisture and chemical resistance. The aqueous polyurethane dispersions of this invention are prepared without the use of emulsifiers. If desired, the emulsifiers can be added to the dispersion to further stabilize the anti-coagulation dispersion caused by the addition of ounds external to the dispersion, or against external conditions. The chosen emulsifiers should be those that do not affect the properties of the polymer. The aqueous polyurethane dispersion can be formed with up to about 15% by weight, preferably from about 5 to about 15% by weight, of ercially available melamine resins, for example, "Cy 301" by American Cyanamid, or resins epoxies, for example, vEpon 828"from Shell Chemical Co. Dispersions can also form ounds with up to about 15% by weight of vinyl ounds, for example, vinyl acetate, methyl acrylate, styrene, etc., as well as polymers containing vinyl groups Typically, the aqueous polyurethane dispersions of the present invention, when used as adhesives, are applied, for example, by the use of a draw bar, on a film, sheet or other flexible substrate for provide a coating weight of approximately 1 to 2 pounds per 3000 square yards of substrate surface The coated substrate is dried to substantially remove the total water. The sticky surface is then bonded onto a second or the same substrate by applying pressure to provide good contact between them. The aqueous polyurethane dispersion of the present invention can be used advantageously as a binder osition in an aqueous coating osition such as for example an engraving or flexographic ink osition. The binder osition is prepared by dispersing a flexographic / gravure ink pigment in the polyurethane dispersion of the invention. The purpose of the pigment or dye is to provide contrast between the color of the coated substrate and the color of the ink osition in order to provide a visually identifiable mark on the substrate. Pigments useful in this invention typically include white, black, organic red, organic yellow, inorganic red, inorganic yellow, and organic blue as well as violet, orange, green, brown, and other organic yellow and red dyes.

Useful pigments include, for example, ferrite yellow oxide, red iron oxides, ferric iron oxide coffee (which is a mixture of red, yellow and black iron oxides), cinnamon oxide (which is a similar mixture), siena bruta and burned sienna, dark burnt and burnt dark ocher, green and blue copper phthalocyanine, DNA orange (dinitroaniline orange # 5), lamp black, lamp black, toluidine red, parachloro red, yellow hansa (red burned and red coffee) which are coupling azo of metaparanitrotoluidieno and red of quinacridona, magenta and violet. The pigment can be any of those typically used in flexographic inks such as yellow monoazo (for example, Cl Pigment Yellows 3, 5, 98); yellow diarylurides (for example, Cl Pigment Yellow 12, 13, 14); Pyrazolone Orange, Per anent Red 2G, Lithol, Rubine 4B, Rubine 2B, Red Lake C, Lithol Red, Permanent Red R, Phthalocyanine Green, Phthalocyanine Blue, Permanent Violet, titanium dioxide, carbon black, etc. Opacity pigments can be added to the polyurethane dispersion to form the binder composition of this invention. Opacity pigments are generally pigments that have a refractive index of at least about 1.8. Typical white opacity pigments include rutile and anatazatitanium dioxide.

The binder composition may further contain non-opacifying fillers or extender pigments commonly known in the art as inerts and include clays such as kaolin, silica, talc, nickel, barite, calcium carbonate and other conventional filler pigments. . All filler or extension pigments have relatively low refractive indices and can generally be described as pigment other than opacity pigment. Metal flake pigments are used for the production of what are known as "glamorous metallic" finishes. Suitable metallic pigments include, in particular, aluminum flakes, bronze copper flakes as well as mica with metal oxide coating. The binder composition of this invention may contain filler / extender pigments as well as dye pigments to provide an aqueous dispersion having a desired total PVC pigment volumetric content. The volumetric content of pigment will typically be from about 5 to about 80% by weight. The binder composition of this invention can be prepared in the following manner. The pigment is mixed with the polyurethane dispersion of the invention and, at an appropriately adjusted viscosity level, is dispersed with a ball mill, sand mill, high shear fluid flow mill, Coles Dissolve, Katy Mili , or similar. The dispersion process de-agglomerates the pigment particles and the binder resin in dispersion causes the deagglomerated pigment particles to be wetted with the aqueous polyurethane dispersion. This wetting therefore prevents the re-agglomeration of the pigment particles. This invention also relates to printing inks comprising the binder composition of this invention and to a method for the preparation thereof. The method for preparing printing inks comprises diluting the binder composition of this invention with an aqueous composition comprising a binder resin and essentially free of volatile organic solvents. The inks will typically be formed from approximately equal quantities of binder composition and aqueous composition, ie, the weight ratio between the binder composition and the aqueous composition will be within a range of from about 2: 1 to about 1: 2. The aqueous composition will typically be formed of a larger amount (i.e., at least 50% by weight) of water and a smaller amount of resin solids (eg, at least about 5% by weight, more typically from about 10 to about 40%, and still more typically from about 20 to about 35%). The aqueous composition will also typically be essentially free of volatile organic solvents. Thus, a printing ink comprising a binder composition and an aqueous composition is also provided by this invention, said ink composition being essentially free of volatile organic solvents. In certain embodiments, the resin in the aqueous composition is a polyurethane resin identical or similar to the polyurethane resin in the binder. In other embodiments, the aqueous composition is an acrylic emulsion, for example, a water dispersible acrylate resin prepared by the suspension polymerization of one or more monomers selected from the group consisting of alkyl acrylates, alkyl methacrylates and mixtures of a higher amount by weight of an alkyl acrylate or alkyl methacrylate with a minor amount by weight of one or more copolymerizable comonomers, in the presence of a support resin. Thus, the printing inks of this invention may also contain, as the binder resin, an acrylate polymer. Examples of such acrylate polymers and methods for their preparation are presented in U.S. Patent No. 5,714,526, the content of which is incorporated herein by reference.

If desired, the ink composition may contain other optional materials well known in the printing ink art. These compositions include cross-linking agents, surfactants, flow control agents, thixotropic agents, fillers, anti-fouling agents, organic co-solvents, catalysts, and other customary auxiliaries. These materials can constitute up to 40% by weight of the total weight of the coating composition. The coating compositions of the present invention can be applied to various substrates to which they adhere, including wood, metals, glass, cloth, plastic, foam, elastomeric substrates, and the like. The compositions may be applied by conventional means including brushing, dipping, flow coating, spraying, and the like, but are applied more frequently by spraying. The usual spray techniques and the usual equipment for air spraying and electrostatic spraying and either manual or automatic methods can be used. During the application of the coating composition on the substrate, the ambient relative humidity can be within a range of about 30 to about 80%. The coating composition of the present invention is particularly advantageous when applied at a relative ambient humidity that is within a range of about 30 to about 60%, providing very smooth coatings. A coating film is formed on the substrate during the application of the coating composition on the substrate. Typically, the thickness of the coating will be within a range of 0.1 to 5 mils (from 2.54 to 127 microns), preferably 0.4 to 1.5 mils (from 10.16 to 38.1 microns) in thickness. The following examples illustrate the practice of the present invention: EXAMPLE 1 0.5 equiv. Of a solution was placed in a reaction flask equipped with a stirrer and a heating jacket. 4,4'-dicyclohexylmethylene diisocyanate (Desmodur-W, Bayer Corporation) and 0.15 equivalent of polyoxypropylene glycol with a molecular weight of 2,000, (PPG 2000, Union Carbide Corp) and 8 drops of dibutyltin dilaurate as a catalyst. The mixture was maintained at a temperature of 80 ° C for 1 hour with good mixing. The temperature was then brought to 80 ° C and 0.25 equivalent of hydroxyl of dimethylolpropionic acid (DMPA) was added to the reaction medium by mixing x. The temperature was maintained within a range of 75 to 80 ° C. In a separate 1-liter beaker, a calculated amount of deionized water and 0.1 equivalent of hydroxylamine (BASF Corp) were placed as a chain extender with 0.125 equivalent of triethylamine as the base. After 5.5 hours, when the% NCO had reached a value of less than 2% (as measured by titration), the prepolymer was added to the one liter laboratory beaker with vigorous stirring. The resulting fine dispersion had a solids content of about 32%, a pH of about 7.0, and a viscosity of 150 to 200 cps at room temperature. EXAMPLE 2 The procedure of Example 1 was repeated except that 0.5 equivalent of isophorone diisocyanate (Desmodur I, Bayer Corporation) was used. The prepolymer was dispersed as in Example 1 to provide a dispersion of 40% solids, whose pH was 7.1 and whose viscosity was 50 to 150 cps at room temperature. EXAMPLE 3 The procedure in Example 1 was repeated except that 0.25 equivalent of isophorone diisocyanate (Desmodur I, Bayer Corporation) and 0.25 equivalent of toluene diisocyanate (TDI) were used in place of Desmodur W. The prepolymer was dispersed as in the Example 1 to provide a white-colored dispersion of milky appearance with 32% solids with a pH of 6.9 and a viscosity of 50 to 100 cps at room temperature. EXAMPLE 4 The procedure of Example 2 was repeated using 0.1 equivalent of polypropylene glycol of a molecular weight of 3000 (PPG 3025, ARCO Chemical Company) and 0.05 equivalent of hexanediol adipate (Rucoflex 105-36, Ruco Corporation) in place of PPG 2000. The resulting dispersion had a pH of 6.9 and a viscosity of 150 cps at room temperature. COMPARATIVE EXAMPLE 1 __ 0.5 equiv. Of 4,4 'diisocyanate (Desmodur-W, Bayer Corporation) and 0.15 equivalent of polyoxypropylene glycol with a molecular weight of 0.4% were added to a reaction bottle equipped with a stirrer and heating jacket. 2000 (PPG 2000, Union Carbide Corp) and 8 drops of dibutyltin dilaurate as a catalyst. The mixture was maintained at a temperature of 80 ° C for 1 hour with good mixing. The temperature was then brought to 80 ° C and 0.25 equivalent of hydroxyl of dimethylolpropionic acid (DMPA) was added to the reaction medium by mixing. The temperature was maintained at a level located within a range of 75 to 80 ° C. A calculated amount of deionized water and 0.1 equivalent of ethanolamine with 0.125 equivalent of triethylamine was placed in a separate 1-liter laboratory beaker. After 5.5 hours, when the% NCO had reached a value less than 2% (titration), the prepolymer was added to the 1 liter beaker with vigorous stirring. The resulting fine dispersion had a solid content of about 30%, a pH of about 7.2, and a viscosity of 1500 to 1700 cps at room temperature. This viscosity is too high to be used in an adhesive formulation. EXAMPLE 5 The dispersion of Example 2 was employed to make laminations typically employed in the flexible packaging industry. 1.0 pound / ream (3000 square feet) was applied to a primary film through an application rod. After drying for 1 minute at a temperature of 180 ° F, the secondary film and the primary film were laminated together at a temperature of 140 ° and at a pressure of 50 psi in a table laminator. The initial adhesion and the 1-week adhesion of the laminates were measured in an Instron tension tester. These data appear in table 1 below. Table 1 Film film union initial union to 1 week secondary primary (grams / inch) (grams / inch) OPP OPPcoex 275 400 MOPP PE 150 250 (50% MD) OPP PE 300 600 (PE Elongation) OPP = oriented polypropylene MOPP = metallized oriented polypropylene OPPcoex = co-extruded oriented polypropylene PE = polyethylene MD = metal delamination It can be seen from the results of table 1 that the laminates produced from the dispersion of Example 2 exhibited strong initial bonds and improved strength of the bonds after 1 week. EXAMPLE 6 A laminating adhesive formulation was produced from a mixture of the dispersion of Example 4 and a water dispersible epoxy resin (WD 510, Shell Corporation) at a mixing ratio of 100: 10. The mixed material was used for lamination of a size 48 polyester film provided by Dupont under the trade name Mylar with a polyethylene film supplied as SL 1 by the same company. The dry coating weight of the adhesive was 1.5 pounds / ream. The fully cured laminate after one week was sealed in a bag and filled with water. The bag filled with water was boiled for 30 minutes in a laboratory glass filled with water. The bag maintained its integrity after this boil test.

Claims

CLAIMS. A composition comprising a polyurethane carried in water containing a plurality of urea-urethane bonds corresponding to the formula: 0 O 1 I -NH-C-HN-O-C-NH-. The composition according to claim 1 further comprising at least one component selected from the group consisting of resins, thickeners, renderers, pigments, wetting agents, foam removers, emulsifiers, crosslinking agents, and mixtures thereof. . The composition according to claim 2 wherein the resin is a melamine resin, epoxy resin, or a polymer containing a vinyl group. The composition according to claim 1 further comprising at least one pigment. The composition according to claim 4 further comprising at least one filler. A coating composition comprising the composition according to claim. The coating composition of claim 6 further comprising at least one component selected from the group consisting of a crosslinking agent, surfactant, flow control agent, thixotropic agent, filler, gas antiforming agent, organic co-solvent, catalyst and mixtures thereof. An adhesive comprising the composition of claim 1. The adhesive according to claim 8 further comprising one of the components selected from the group consisting of resins, thickeners, fillers, pigments, wetting agents, foam removers, emulsifiers. , crosslinking agents, and mixtures thereof. . The adhesive according to claim 9 wherein the resin is a melamine resin, an epoxy resin or a polymer containing vinyl groups. . An aqueous dispersion of polyurethane produced by the process comprising the step of reacting an isocyanate-terminated prepolymer having ionized groups or groups easily ionizable with hydroxylamine to form a polyurethane containing a plurality of urea-urethane bonds corresponding to the formula: O O! I-NH-C-HN-O-C-NH-. . The aqueous polyurethane dispersion according to claim 11 wherein the isocyanate-terminated prepolymer is obtained by the reaction of an organic isocyanate compound having at least two isocyanate groups with a polyol and an organic compound having at least two hydrogen atoms active and at least one ionized or easily ionizable group. . The aqueous polyurethane dispersion according to claim 11 produced by the process further comprising the step of reacting the polyurethane with a base to neutralize or remove the ionized or easily ionizable groups. . The aqueous polyurethane dispersion according to claim 13 wherein the step of reacting the polyurethane with a base is carried out in the presence of water. . The aqueous polyurethane dispersion according to claim 12 wherein the organic isocyanate is selected from the group consisting of 4,4 '-diphenylmethane diisocyanate (MDI), 2,4- and 2,6-toluene diisocyanate (TDI) , ditolyl diisocyanate (TODI), 1,5-naphthalene diisocyanate, 4,4-dibenzyl diisocyanate, m- or p-xylene diisocyanate, 1,3-phenylene diisocyanate, 1,6-hexamethylene diisocyanate, diisocyanate of isophorone, 1,4-cyclohexanediisocyanate, 4,4'-dicyclohexylmethylene diisocyanate, and mixtures thereof. 16. The aqueous polyurethane dispersion according to claim 12 wherein the polyol is selected from the group consisting of polyester polyols, polyether polyols, polycarbonate polyols, caprolactone-based polyols, and mixtures thereof. 17. The aqueous polyurethane dispersion according to claim 12 wherein the organic compound is selected from the group which consists of diamine and diol compounds containing carbonyl groups capable of forming salts. 18. The aqueous polyurethane dispersion according to claim 13 wherein the base is a tertiary amine. 19. A process for making a polyurethane carried in water comprising the step of reacting an isocyanate-terminated prepolymer having ionized or easily ionizable groups with hydroxylamine to form a polyurethane containing a plurality of urea-urethane bonds corresponding to the formula : 0 O 1 I -NH-C-HN-O-C- H-. 0. The process according to claim 19, wherein the isocyanate-terminated prepolymer is obtained by the reaction of an organic isocyanate compound having at least two isocyanate groups with a polyol and an organic compound having at least two active hydrogen atoms and at least one ionized or easily ionizable group. . The method according to claim 19 produced by the method also includes the step of reacting the polyurethane with a base to neutralize or remove the ionized or easily ionizable groups. . The method according to claim 21 wherein the step of reacting the polyurethane with a base is carried out in the presence of water. . The process according to claim 20 wherein the organic isocyanate is selected from the group consisting of 4,4'-diphenylmethane diisocyanate (MDI), 2,4- and 2,6-toluene diisocyanate (TDI), diisocyanate ditolyl (TODI), 1,5-naphthalene diisocyanate, 4,4-dibenzyl diisocyanate, m- or p-xylene diisocyanate, 1,3-phenylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethylene diisocyanate, and mixtures thereof. The process according to claim 20 wherein the polyol is selected from the group consisting of polyester polyols, polyether polyols, polycarbonate polyols, caprolactone-based polyols, and mixtures thereof. 25. The process according to claim 20 wherein the organic compound is selected from the group consisting of diamine and diol compounds containing carboxyl groups capable of forming salts. 26. The process according to claim 21 wherein the base is a tertiary amine. 27. The aqueous polyurethane dispersion produced by the process comprising: reacting an organic isocyanate compound containing at least two isocyanate groups with a polyol and an organic compound having at least two active hydrogens and at least one ionized group or easily ionizable to provide an isocyanate-terminated prepolymer; reacting the isocyanate-terminated prepolymer with hydroxylamine to provide a polyurethane containing a plurality of urea-urethane bonds corresponding to the general formula: 0 O 1 I -NH-C-HN-O-C-NH reacting the polyurethane with a base to neutralize or remove the ionized or easily ionizable group. . The aqueous polyurethane dispersion according to claim 27 wherein the isocyanate-terminated prepolymer reacts with hydroxylamine in the presence of water. . The aqueous polyurethane dispersion according to claim 27 wherein the polyurethane reacts with a base in the presence of water. . An aqueous polyurethane dispersion produced by the process comprising: reacting an organic isocyanate compound having at least two isocyanate groups with a polyol and an organic compound possessing at least two active hydrogen and at least one ionized or easily ionizable group for provide an isocyanate-terminated prepolymer; reacting the isocyanate-terminated prepolymer with a base to neutralize or remove the ionized or easily ionizable group; and reacting the isocyanate-terminated prepolymer with hydroxylamine to provide a polyurethane containing a plurality of urea-urethane bonds corresponding to the formula: 0 O 1 t -NH-C-HN-O-C-NH- 31. The aqueous polyurethane dispersion according to claim 30 wherein the isocyanate-terminated prepolymer reacts with a base in the presence of water. 32. The aqueous polyurethane dispersion according to claim 30 wherein the isocyanate terminated prepolymer reacts with hydroxylamine in the presence of \ X water. 33. The aqueous polyurethane dispersion according to claim 30 wherein the isocyanate-terminated prepolymer reacts simultaneously with hydroxylamine and base in the presence of water. 34. A flexible packaging comprising a plurality of flexible substrates bonded together by an adhesive comprising a polyurethane containing a plurality of bonds corresponding to the formula: O O I I -NH-C-HN-O-C-NH-. 35. The flexible packaging according to claim 34 wherein the substrates comprise a non-porous film or sheet. 36. The flexible packaging according to claim 34 wherein the substrates comprise a polyolefin film. . The flexible packaging according to claim 36 wherein the polyolefin film is a polyethylene film. . The flexible packaging according to claim 34, wherein said flexible packaging is a bag. . A method for forming a flexible package comprising the supply of an adhesive comprising an aqueous dispersion of a polyurethane containing a plurality of urea-urethane bonds corresponding to the general formula: 0 O 1 I -NH-C-HN-O-C-NH-; provide at least one flexible substrate; applying a layer of adhesive on at least one selected section of the substrate; and forming at least one junction between the selected section of the substrate and another section of the same substrate or of a different substrate by sandwiching the adhesive therebetween.