MXPA99002602A - Water-based vacuum forming laminating adhesive - Google Patents

Abstract

A water-based vacuum forming laminating adhesive includes an ionic water-dispersed polyurethane, a carbodiimide and/or an aziridine, and optionally a vinyl acetate polymer. The polyurethane is characterized by a high polydispersity index, which provides a combination of adhesion and thermal stability. The polyurethane is made by chain extending an isocyanate functional urethane prepolymer with polyamine and ketimine.

Description

LAMINANT ADHESIVE WATER BASED VACUUM FORMATOR BACKGROUND OF THE INVENTION The present invention relates to water-based adhesives especially useful for the lamination of plastic films by vacuum forming techniques. This technique is used to make parts for the automotive and furniture industries. Vacuum formation is a known process, particularly in the automotive industry. For example, a thermoplastic material (eg, flexible polyvinyl chloride sheet) can be laminated onto automotive components such as consoles, instrument panels, door panels and other interior surfaces using vacuum forming. The substrates may be any commonly known materials, such as acrylonitrile-butadiene-styrene (ABS) terpolymer or "hardboard." The process includes coating the substrate with a laminate adhesive, heating the thermoplastic material above its softening point, and coating the thermoplastic material on the substrate, then vacuum is applied through the substrate to draw the thermoplastic material to the contours of the substrate.The use of organic solvent-based adhesives in vacuum formation is common in the industry. The use of organic solvents in the atmosphere is a cause for concern, and the reduction of the volatile organic content of the adhesive compositions is very desirable to comply with government regulations.These adhesives present occupational hazards typically associated with organic solvents.A water-based thermoforming adhesive it is described in United States patents number 4.76 2,880 and 4,853,061. These patents disclose the use of an adhesive having an aqueous emulsion or dispersion of aromatic polyurethane and a water-dispersible crosslinking agent, such as an unblocked organic isocyanate compound. The compositions described in these patents are stable only for several hours and within about seven hours recognizable decreases in performance are observed. The stability of the adhesive compositions is an important factor in determining its usefulness. For example, compositions with stability comparable to those described in the patents identified above should be stored in such a manner that the reactive components are separated and mixed only immediately prior to application. Such handling requirements impose additional costs. In addition, such compositions are especially expensive if, for example, a stop occurs in a production line. In such a case, a complete batch of adhesive can react sufficiently during the delay, it being necessary to discard the batch. In view of the above explanation, a single package, water-based, vacuum-forming laminating adhesive composition which is highly stable and provides excellent adhesive properties is needed. U.S. Patent No. 5,430,094 (Gola et al.) Discloses an aqueous adhesive composition that includes a polymer of vinyl acetate, an ionic polyurethane dispersed in water, and an aziridine. Said patent discloses a composition that is required to have less than about 0.2 milliequivalents of titratable acid, more particularly less than about 0.1 milliequivalents of titratable potentiometric acid, and very particularly less than about 0, 05 milliequivalents of titratable potentiometric acid. It would be desirable to be free of such a restriction as regards the acid content. Aqueous epoxy coating compositions are disclosed in U.S. Patent No. 5,227,414, wherein mono- or polyketymine compounds are reacted with another functional group with an isocyanate-terminated polyurethane prepolymer. In such a composition, the ratio of total hydrogen atoms of the primary amino group to epoxide groups is from about 0.9 to 2.

COMPENDIUM OF THE INVENTION The present invention is a stable, water-based adhesive composition which includes a cationic polyurethane dispersed in water, carbodiimide and / or an aziridine. Typically, the compositions also include a substantial amount of a vinyl acetate polymer as a blender resin to reduce the cost of the adhesive. In particular, the invention is characterized by the new polyurethane used in the composition. The polyurethane is water dispersible and has an exceptionally high polydispersity index of at least 20, most preferably at least 25. The polyurethane is made by reacting, in solvent, at least one polyisocyanate and at least one polyol to make an isocyanate urethane prepolymer functional. The chain of the resulting urethane prepolymer is then extended by reacting some of the remaining isocyanate groups with a polyamine to obtain the polyurethane. It has been found to be advantageous to achieve the desired polydispersity to use as the chain extender a polyamine compound having at least two primary amino groups, preferably at least three primary amino groups, thereby producing a substantial amount of high molecular weight polymer . Simultaneously, to ensure a substantial amount of relatively low molecular weight polymer, the chain extension polyamine is used in combination with a compound capable of closing chain development by reacting with a portion of the isocyanate groups in the prepolymer. It has been found that it is very advantageous to use ketimines as the chain sealing compound, preferably diketimines. The secondary amines in the ketimines react with the isocyanate groups, thereby terminating the chain development. Upon subsequent introduction of water, the imine groups are hydrolyzed, producing primary amino groups that are available for cationic salt formation, thus making the polymer dispersible in water. After dispersion in water, the organic solvent used during the polymer synthesis can be extracted. Excellent adhesion and stability is achieved without the need to maintain a particularly low level of titratable acid.

DETAILED DESCRIPTION OF THE INVENTION The vinyl acetate polymer of the present invention may be polyvinyl acetate, or a polymer derived from polyvinyl acetate such as a polyvinyl alcohol produced by alcoholysis of a polyvinyl acetate, or a polyvinyl acetal produced by condensation of a polyvinyl alcohol with an aldehyde, acetaldehyde, formaldehyde or butyraldehyde. Polyvinyl acetals include polyvinyl acetal, polyvinyl formal and polyvinyl butyral. The vinyl acetate polymer of the present invention also includes copolymers produced from vinyl acetate monomers and other monomers. For example, such comonomers include alpha olefins such as ethylene, acrylates such as methyl acrylate, maleates such as diethyl maleate, fumarates such as dimethyl fumarate, and vinyl monomers such as vinyl chloride. The polymerization of vinyl acetate and vinyl acetate and copolymerizable monomers can be carried out by methods known in the art. For example, bulk and solution polymerization, emulsion polymerization and suspension polymerization can be used. The preferred vinyl acetate polymer of the present invention is a vinyl acetate homopolymer. The vinyl acetate polymer of the present invention is typically present in the composition in an amount between about 8 weight percent and about 48 weight percent, more preferably between about 18 weight percent and about 38 percent by weight, and most preferably between about 24 weight percent and about 32 weight percent based on the total weight of resin solids. A suitable commercially available vinyl acetate homopolymer is known as RHOPLEX VA 2113, by Rohm and Haas. RHOPLEX VA 2113 is a homopolymer emulsion of vinyl acetate with a solids content of 55%, a pH of 4.5 at 25 ° C, a viscosity at 25 ° C of 1100 cps, an average particle size of 0.20 microns, a specific emulsion gravity at 25 ° C of 1.11, and a Tg of 29 ° C. Another suitable vinyl acetate product is AIRFLEX 300, AIRFLEX 400 or AIRFLEX 440, which are ethylene / vinyl acetate copolymers commercially available from Air Products and Chemicals, Inc. Another suitable product is ROVACE 3357, acetate polymer. vinyl sold by Rohm & Haas. The polyurethane dispersed in water of the present invention is preferably cationic. The polyurethane can be prepared by methods known in the art, and is typically prepared by reaction of a polyisocyanate with a compound having a plurality of hydroxyl groups to form an isocyanate-functional urethane prepolymer. The polyisocyanates for preparing the urethane prepolymer can be aliphatic or aromatic isocyanates. Representative examples are aliphatic isocyanates such as trimethylene, tetramethylene, pen-tamethylene, hexamethylene, 1,2-propylene, 1,2-butylene, 2,3-butylene, and 1,3-butylene diisocyanates; cycloalkylene compounds such as diisocyanates of 1,3-cyclopentane, 1,4-cyclohexane, 1,2-cyclohexane and isophorone diisocyanates; aromatic compounds such as m-phenylene, p-phenylene, 4,4'-diphenyl, 1,5-naphthalene and 1,4-naphthalene diisocyanates; aliphatic-aromatic compounds such as 4,4'-diphenylenemethane, 2,4- or 2,6-tolylene, or mixtures thereof, 4,4'-toluidine and 1,4-xylylene diisocyanates; the substituted nuclear aromatic compounds such as dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate and chlorodiphenylene diisocyanate; triisocyanates such as triphenyl methane-4,4'4"-triisocyanate, 1,3,5-triisocyanate benzene and 2,4,6-triisocyanate toluene, and tetraisocyanates such as 4,4'-dimethyldiphenyl methane-2, 2'-5, 5'-tetraisocyanate: polymerized polyisocyanates such as tolylene diisocyanate dimers and trimers, and the like Polyhydroxy compounds useful for reacting with polyisocyanates for preparing urethane prepolymers are typically hydroxy-terminated polyethers or polyesters. The polyethers are typically poly (oxyalkylene) derivatives of polyhydric alcohols, such as glycerol, trimethylolpropane, 1,2,6-hexanetriol, sorbitol, ma-nitol pentaerythritol or sucrose, suitable polyesters are typically prepared from the reaction of a carboxylic acid and a polyol, for example, the reaction between adipic acid or phthalic acid and ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, diethylene glycol, 1, 2,6-hexanotriol, trimethylolpropane, or trimethylolethane. The urethane prepolymer prepared by reacting a polyisocyanate with a polyhydroxy compound is provided with cationic groups to make the polymer dispersible in water. Polymers containing suitable salt precursors can be converted into the cationic salts by adding a quaternizing or neutralizing agent to the polymer. In the present invention, the amino-containing compounds serve to introduce salt forming groups and to extend the urethane prepolymer chain to form a polyurethane resin containing a wide range of molecular weights. In order to extend the chain of the urethane prepolymers, polyamines are reacted with at least two primary amino groups, preferably at least three amino groups, with the isocyanate groups of the urethane prepolymer. Alkylene polyamines can be used, but especially preferred are the triamines sold under the name JEFFAMINE® by Texaco, characterized by the structure: R1- [0 (R20) nCH2NH2] 3 where R1 and R2 are alkyl groups with 1 to 3 carbon atoms . The polyamine ketimines which can be used together with the polyamines during the chain extension step are derived from the reaction of a polyamine with a ketone. Preferred polyamines for making ketimines are alkylene polyamines and substituted alkylene polyamines. Especially preferred polyamines are selected from those having the following formula: H2NRNHRNH2 where R is a difunctional aliphatic group containing from 2 to about 48 carbon atoms. R can represent identical or different radicals in any polyamine compound. There may be inert or non-interfering groups in the R group. Especially preferred are the polyamines in which R is a group of aliphatic hydrocarbons. It is still more preferred that R is an alkylene group of 2 to 6 carbon atoms. Typical examples of preferred polyamines for making the ketimines include diethylene triamine and the higher homologs of polyethylene polyamine, as well as the corresponding propylene and bu polyn amines. Other amines that may be employed include primary-secondary amines such as N-aminoethyl piperazines or amines corresponding to the formula: RNH-R-NH2 Said polyamines are converted to ketimines by reaction with ketones of the following formula: R1-C-R ^ wherein Rx and R2 are organic radicals and each is substantially inert to the ketimine formation reaction. Preferably Ri and R2 are short chain alkyl groups (1 to 4 carbon atoms). It is often preferred to use a ketone that boils below or near the boiling point of water or that easily distils with water. Preferred examples include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, ethyl isopropyl ketone, cyclohexanone, cyclopentanone, acetophenone and the like. Especially preferred are acetone, methyl ethyl ketone and methyl isobutyl ketone. Ketones react with the primary amino groups of the polyamines (m-NH2) as follows: O m-N (m-NH2) + Rx - d - R2? R1 - C - R2 + H20 When the polyamine includes two primary amino groups, each polyamine may react with two ketones to form a diketimine. When the ketimines are included in the chain extension step, the secondary amino groups in the ketimines are reacted with a portion of the isocyanate groups contained in the urethane prepolymers, thereby partially closing the chain development. Simultaneously, chain development progresses by the reaction of other isocyanate groups with the polyamine chain extension agent. As a result, the resulting extended chain polyurethane has a combination of a substantial portion of relatively high molecular weight polymers and a substantial portion of relatively low molecular weight polymers. Thus, the polyurethane of the present invention exhibits the high polydispersity index (at least 20, most preferably at least 25) which has been found to be advantageous for use in adhesive compositions. On the basis of equivalents of isocyanate-reactive groups, the ratio of polyamine to ketimine used in the chain extension step can be in the order of 1: 1 to 4: 1, preferably 1.1: 1 to 3: 1. In preferred specific embodiments, a ratio of 2: 1 has been found to be satisfactory. Substantially all isocyanate groups are reacted during the chain extension step. The polydispersity index is the number derived from dividing the average molecular weight by the number of average molecular weight. Relatively low molecular weights can be considered as those in the range of 3,000 to 10,000. Some molecules with molecular weights below 3,000 may be present in the polyurethane of the present invention, but their amounts are not significant, nor is their presence considered useful. It can be considered that relatively high molecular weights are greater than 30,000 and in particular those greater than 100,000. The polyurethanes of the present invention have a substantial content of polymers having molecular weights greater than 30,000 and greater than 100,000. Expressed differently, the polyurethanes of the present invention are composed of at least 10 percent (preferably at least 15 percent) of polymers having molecular weights (basis by weight) greater than 100,000 and at least 10 percent (preferably at minus 15 percent) polymers having molecular weights (basis by weight) less than 10,000. The high molecular weight portion provides the polymer with temperature resistance, and the low molecular weight portion provides the polymer with bond strength. It is significant that the synthesis of the polyurethane through the chain extension step is carried out in an organic solvent medium, in which the imine groups of the ketimines are stable. After the chain extension step, water is introduced into the system, whereby the imine groups hydrolyze and become groups of cationic salts that help disperse the polyurethane in water. Thus, the ketimines do in fact provide blocked amino groups during chain extension, thereby partially closing the molecular weight growth as well as providing amino groups for the next step of aqueous dispersion. A special utility for the aqueous polyurethanes of the present invention is in adhesive compositions, in particular those used in the vacuum formation of laminates. The next portion of the description refers to formulating this type of adhesive using the polyurethane of the present invention. The polyurethane resin of the present composition is typically present in vacuum forming adhesive compositions in amounts of between about 24 weight percent and about 64 weight percent, more preferably between about 34 weight percent and about 54 weight percent. weight percent, and most preferably between about 40 weight percent and about 48 weight percent based on the total weight of resin solids. A second component that is considered useful in the adhesive compositions of the present invention is carbodiimide, which is a wetting agent and provides greater coverage of the composition on a substrate. It is also considered to contribute to the adhesion and thermal stability of the compositions. As used herein, the term carbodiimide refers to carbodiimide and substituted carbodiimides. Typically, a carbodiimide is present in the composition in amounts of between 0.5 percent by weight and 10 percent by weight, more preferably between 1 percent by weight and 8 percent by weight, and most preferably between about 2 percent by weight and about 5 weight percent based on the total weight of resin solids. A commercially available multifunctional carbodiimide which has been found useful can be obtained from Union Carbide under the name UCARLINK XL 29SE. Other analogous materials include hydrogen cyanamide, dicyandiamide. Some embodiments of vacuum forming adhesive compositions further include an aziridine compound, although it is not required for the desired performance properties. The aziridine compound serves primarily as a blender resin, that is, to reduce the overall cost of the adhesive compositions. In some formulations, it is believed that heat resistance also improves in some circumstances. As used herein, the term "aziridine" refers to any alkyleneimine and includes any compound based on the following structure: R "R" R - C - C - R x / NH where R 1 is hydrogen, an alkyl radical with 1 to 3 carbon atoms, phenyl or combinations thereof. Preferably, aziridine is based on the following structure: R1 R1 R x C - C R 1 / NR "2 wherein R 1 is as described above and R 2 is hydrogen or an alkyl radical having 1 to 4 carbon atoms, such aziridines include ethyleneimine, ethylethylenimine and pro-phenylimine. The present invention also includes polyfunctional aziridines The especially useful polyfunctional aziridines include trimethyltolpropane-tris- (β- (n-aziridinyl) propionate) and pentaerythritol-tris- (β- (N-aziridinyl) propionate). The aziridine of the adhesive composition is typically present in amounts between 0 percent by weight and 10 percent by weight When aziridine is used, it is preferably included in amounts between 1 weight percent and 6 weight percent, and very typically between 2 weight percent and 5 weight percent based on the total weight of resin solids in the adhesive The two polyfunctional aziridine curing agents specified above can be obtained from the Virgi market nia Chemicals of Portsmouth, Virginia as XAMA-2 and XAMA-7, respectively. XAMA-2 has a solids content of 100%, an aziridine content of 6.00 to 7.00 milliequivalents per gram, an aziridine functionality of about 2.7, a density at 25 ° C of 1.109 grams / ml, a viscosity at 25 ° C of 125-500 cps, a freezing point below -15 ° C, a vapor pressure of less than 0.1 mm, and a solubility in water of 6.5% by weight. XAMA-7 has a solids content of 100%, an aziridine content of 6.35-6.95 milliequivalents / gram, an aziridine functionality of about 3.3, a density at 25 ° C of 1.185 grams / ml, a viscosity at 25 ° C of 1,200-2,000, a freezing point below -10 ° C, and it is completely miscible in water. The present composition also optionally includes other additives. An additive is a plasticizer of butylbenzenesulfonamide. This compound and other similar compounds are useful as wetting agents and to improve the flow of the composition. Typically, the butylbenzenesulfonamide plasticizer is present in the composition in amounts between 0 percent by weight and about 33 percent by weight, more preferably between 5 percent by weight and 20 percent by weight, based on the total weight of solids. resin. A commercially available butylbenzenesulfonamide plasticizer can be obtained from The C.P. Hall Company as PLASTHALL BSA, which has a solids content of 100%. Another class of compounds useful in this regard are melamine derivatives such as the alkoxylated melamine resins sold under the name CYMEL® by Cytec Technologies Corp. For example, CYMEL® 303 hexamethioxymethyl melamine has been used. The present composition may also optionally include propylene glycol and other similar compositions for use as a plasticizer. Typically, when propylene glycol is used, it is present in the composition in amounts between about 0.5 weight percent and about 6 weight percent, more preferably between about 1 weight percent and about 5 weight percent, and most preferably between about 2 weight percent and about 4 weight percent based on the total weight of resin solids. Typically, the adhesive compositions include water in an amount of between about 25 weight percent and about 75 weight percent, more preferably between about 40 weight percent and about 60 weight percent, most preferably between about 45 percent in weight and approximately 53 weight percent based on the total weight of the composition. The adhesive compositions of the present invention are characterized by stability before use. In particular, are sufficiently stable to be useful as a single component adhesive or "a package" in which all components are combined substantially before application without gelation of the composition and without unacceptable increases in viscosity before use. Once a composition gels, it is no longer possible to use it as an adhesive. If the viscosity of a composition increases to the point of being difficult to spray, but the composition does not gel, additional solvent may be added to reduce the viscosity to acceptable levels. Stability can be measured as an increase in viscosity over time at a given temperature. Several standard tests can be used to measure the viscosity. For example, a Brookfield viscometer measures the resistance found by a spindle that is rotated through a container of material being evaluated. The stability of a composition for use as a single component composition can be evaluated by comparing the viscosity of a fresh composition with the same composition after a given time at a given temperature. The composition of the present invention is formulated in such a way that with an initial viscosity of about 1,000-3,000 centipoise (cps), after about 30 days, more preferably after about 60 days, and most preferably after about 90 days, a At room temperature, the composition has less than about 50% viscosity gain, more preferably less than about 35% gain and most preferably less than about 25% gain, the viscosity being measured with a Brookfield viscometer with a spindle number 5. The ambient temperature is considered to be less than about 28 ° C and more typically at about 25 ° C. It should be noted that the stability of the present composition is determined at ambient temperatures and that, at elevated temperatures, it can not achieve high stability characteristics. Although a preferred embodiment of the process of the present invention is specifically adapted to adhere thermoplastic material to structural parts in automobiles, the compositions are useful in applying material to virtually any structural or decorative substrate. Typically, the substrate may be terpolymers of acrylonitrile-butadiene-styrene (ABS), high impact polystyrene (HIPS), styrene-acrylonitrile (SAN) copolymers, polyvinyl chloride (PVC or "vinyl"), polycarbonate (PC), high density polyethylene (HDPE), polyphenylene oxide (PPO) and hardboard. The thermoplastic material can be any material known to those skilled in the art. Such material includes, without limitation, polyvinyl chloride, polyolefin, fabric, and polyurethane. The application of the adhesive can be accomplished in a manner known to those skilled in the art, and includes, for example, spraying the adhesive onto the substrate. The adhesive is typically applied in film thickness of between about 1 mils to about 15 mils (25.4 microns "μ" to 381 μ), and more typically from about 3 mils to about 7 mils. inch (76.1 to 177.8 μ). The composition is then dried on the substrate. Drying can be achieved by allowing the coated substrate to air dry at room temperature or by actively drying the composition at elevated temperatures. Depending on the temperature, humidity and film thickness, the drying of the composition on the substrate can last from several minutes to one hour or more. For example, a film with a thickness of about 5 mils (127 μ) can be dried in a 71 ° C oven in about 3 to 5 minutes. After drying the composition or during the drying of the composition, the flexible material to be laminated to the substrate is heated to soften the material. Typically, the material is heated to a temperature between about 43 ° C and about 82 ° C. The heated material is then contacted with the dried composition. Very typically The material is brought into contact by dropping the heated flexible material on the substrate. Then vacuum is applied to the flexible material on the substrate to draw the material to all the recessed areas of the substrate. Typically, vacuum is aspirated for at least about 10 seconds. In the case of non-porous substrates, holes are made in the substrate so that the vacuum can drag the flexible material over the substrate. In the case of porous materials, such as some hard board, vacuum can be directly achieved through the substrate without making holes in the substrate. After the application of vacuum, the adhesive compositions described herein cure at room temperature in about 8-16 hours. The curing can be accelerated by heating the laminated substrate.

The following examples are intended to illustrate the best mode of carrying out the present invention and are not intended to limit the scope of the invention. EXAMPLE 1 Charged in a stirred reaction vessel maintained under a nitrogen blanket was 102 ppp (parts by weight) of isophorone diisocyanate, 79.94 ppp of toluene diisocyanate, 179.13 ppp of CARBOWAX MPGE 2000 pellets (polyethylene glycol monomethyl ether) obtainable from Union Carbide Chemicals and Plastics Company), and 851.00 ppi of FORMREZ 44-56 melt (1,4-butanediol adipate, molecular weight approximately 2000, from Witco Corporation). Each of the above charges, except CARBOWAX, was followed by a rinse of 61.98 ppi of methyl isobutyl ketone. These reagents were heated to 50-55 ° C under agitation until all the raw materials melted to become a uniform mixture; then the temperature was raised to 90-93 ° C and maintained until the isocyanate equivalent weight of 1562.06 was reached. Then 944.07 ppp of acetone was charged and the flask air cooling was started to lower the temperature to below 50 ° C. A load of 49.24 ppp of acetone, 93.55 ppp, was introduced into the flask. JEFFAMINE t-403 { Trimethylol propane poly (oxypropylene) triamine), molecular weight approximately 440, Texaco.}., And 100.69 ppp diketimine (reaction product of diethylene triamine and methyl isobutyl ketone) over a period of 15 minutes, followed by a rinse of 82.09 acetone.The reaction mixture was maintained at 50-55 ° C until no isocyanate peak was observed by infrared spectrometry.

They were inversely diluted 2. 633 ppp of the reaction product to 2. 167, 02 ppp of deionized water and 38, 30 ppp of methylene sulfonic acid. The solvent was then removed from the dispersion to achieve 38 weight percent solids. EXAMPLE 2 Three vacuum forming adhesive formulations were prepared according to the present invention as indicated in Table 1. The ingredients were added in series in the order shown with mixing. TABLE i Adhesive formulations? J. To Ej. B Ex. C Parts Parties Parties Weight in weight by weight Polyurethane (Example 1) 192.23 197, 83 203.2 Ethylene / vinyl acetate11 131.48 135.31 0 Vinyl acetate2 0 0 143.32 Plasticizer3 37, 13 0 37, 13 Lastly4 0 27.7 0? Aziridi crosslinker .nnaa55 2.19 2.19 2.19? Carbodiiimmiiddaa crosslinker66 15.17 15.17 12.36 Thickener7 0.84.04. 0.84 Dye blue8 0.96 0.96 0.96 Deionized water 20 20 20 1 AIRFLEX 400 ethylene / vinyl acetate copolymer from Air Products and Chemical, Inc. 2 ROVACE 3357 vinyl acetate polymer from Rohm & Haas. 3 PLASTHALL BSA butylbenzenesulfonamide plasticizer obtainable from The C.P. Hall Company. KFLEX UD-320W water soluble urethane diol plasticizer available from King Industries, Norwalk, Connecticut. XAMA-2, trimethylolpropane-tris- (β- (N-aziridinyl) propionate), obtainable from Virginia Chemicals. 6 UCARLINK XL-29SE carbodiimide crosslinker from Union Carbide. 7 RM 8 associative urethane thickener obtainable from Rohm & Haas. 87AKROSPERSE E-98 blue dye from Arcochem Corp. The performance of the formulations of Examples AC were checked according to the test procedures set forth below, and the results are shown in Table 2. SURLYN-binding test procedure Plates were cleaned of DYLARK resin (3 inches by 4 inches) (7.6 by 10.2 cm) with isopropyl alcohol and coated with adhesive by spraying a coating weight (dry) from 0.2 to 0.3 gram per 12 square inches (77.5 cm2). The adhesive-coated plates were baked for six minutes at 158 ° F (70 ° C), then cooled. A 5 mil (127 μ) thick SURLYN resin film was attached to each surface of the 5 inch (12.7 cm) vacuum-coated adhesive plate in a vacuum forming device (Formech 450 vacuum former ). The film on each plate was cut into two 1-inch (2m54 cm) wide strips along the panel. A strip, after aging for 1 hour at room temperature, it was started at 180 ° with a force gauge (force gauge model Omega #DFG 51-50) at a rate of 90 inches (228.6 cm) / minute. The second strip was torn in the same way after aging for 24 hours. The results are indicated for each test in pounds of maximum force used. Tissue bonding test procedure DYLARK resin panels (2.75 inches by 1.0 inch) (7 by 2.54 cm) were cleaned with isopropyl alcohol.

Thirteen pound canvas fabric specimens were cut (5.88 kg) (4.0 inches by 1.0 inch) (10.16 by 2.54 cm). Test specimens were prepared by spraying adhesive on the plastic panels and the canvas fabric, and then the fabric was attached to the panel with a 5 pound (2.26 kg) metal roller laminating 10 passes. The sandwich was baked at 158 ° F (70 ° C) for 7 minutes and then aged for 72 hours at room temperature. The specimen was placed in a test frame and a weight was attached to the fabric so that the force was applied at an angle of approximately 60 degrees. The frame with the specimen and weight in position was heated in an oven at 180 ° F (82 ° C) for one hour. The temperature rose 20 degrees and was maintained for an additional hour. Incremental increases in temperature were continued until the temperature reached 240 ° F (115.5 ° C). In each interval, the canvas fabric separation point of the substrate was marked. It was observed that the fabric torn off from the plastic or plastic underwent sufficient heat distortion and had to be separated from the frame. The results are indicated in terms of percentage of the total length moved in each temperature range.

Test procedure of ABS-trilaminate Test plates (4 inches by 6 inches) (10.16 by 15.24 cm) of acrylonitrile-butadiene-styrene resin (ABS) were coated with tensile adhesive with a tensile bar 6 mils (152.4 μ). The plates were boiled by dehydration for 5 minutes at 158 ° F (70 ° C) and cooled. Tri-laminate strips (imitation leather, consisting of a support layer, textured layer, and cover sheet) were preheated to 180 ° F (82 ° C) for 10 to 20 minutes and the ABS plates were placed in the oven for 4 minutes. The vinyl strips were attached to the ABS plate covering each plate with trilamine-do, placing the sandwich in a Carver press (Carver press model 2697), and attaching with 14.6 square pounds for 11 seconds. The samples were cooled for one hour and then resistance to peel was tested at 180 ° using the digital force gauge (Omega DFG 51-50 digital force gauge). The peel strength test was repeated at 24 hours. The results of the maximum peel strength at 1 hour and 24 hours in pounds / linear inch (multiplied by 178.58 to obtain grams / cm) of sample width are indicated. After 72 hours, the plate was placed in a test frame to measure peel strength with hanging weight at 190 ° F (87.8 ° C) as a function of time. A weight of 150 grams was placed on the trilaminate sample and left hanging at an angle slightly deviated from the plane of the plate. The separation position between the substrate and the trilaminating layer was marked and the sample was placed in an oven at 190 ° F (87.8 ° C).

The position of the separation was marked after one hour and after five hours. For the hanging weight test at 190 ° F (87.8 ° C), the time to failure (if it is less than 5 hours) or the distances traveled in one hour and five hours were indicated. TABLE 2 RESULTS OF THE TEST OF ACCESSION INITIAL RESULTS EXAMPLE / PAST A / 1 A / 2 B / l B / 2 C / l C / 2 % solids in 51.3 49 49.9 application Brookfield 750 650 1,200 RVF, n ° 3 @ 20 RPM PH 6.90 6.80 7.20 Substrate bonding SURLYN EXAMPLE / PAST A / 1 A / 2 B / l B / 2 C / l C / 2 Peeling values (lbs / Inches) / g / cm) 1 h 2.60 / 2.88 / 0.75 / 0.72 / 1.72 / 1.76 / 464.3 514.3 133, 9 128 , 6 528, 3 314.3 24 h 2.42 / 2.42 / 0.24 / 0.24 / 2.56 / 1.60 / 432.2 432.2 42, 9 42.9 457.2 285.7 Bonding to canvas cloth substrate-DYLARK EXAMPLE / PAST A / 1 A / 2 B / l B / 2 C / l C / 2 % movement @ 29% 71% 71% 55% Failed Failed 180 ° F (82 ° C) (10 min) (10 min)% movement @ 44% Fail Fail 71% 200 ° F (93.3 ° C) (20 (52 min) min)% movement @ 51% 35% 220 ° F (104, 4 ° C)% movement @ 51% * Failed 240 ° F (115, 5 ° C) (30 min) TABLE 2 (CONT.) Bonding to ABS substrate - trilaminate EXAMPLE / PAST A / 1 A / 2 B / l B / 2 C / l C / 2 Peel Values (lbs / Inch / (g / cm X 102) 1 h 25, 2 / 15.7 / 11.54 / 45 28 20.6 24 h 24.9 / 22.4 / 17.62 / 44.5 40 31.5 Movement 1 HO 190 ° F (87.8 ° C) 3 mm 15 mm 6 mm Movement 5 H @ 190 ° F (87, 8 ° C) 44 mm 42 mm 12 mm TEST RESULTS AT 24 HOURS ® 119 ° F (43.4 ° C) EXAMPLE / PASS A / 1 A / 2 B / l B / 2 C / l C / 2 Brookfield, 700 500 800 RVF, no. 3 @ 20 RPM pH 6.70 6.60 6.90 Bonding to substrate SURLYN (pounds / linear inch) EXAMPLE / PAST A / 1 A / 2 B / l B / 2 C / l C / 2 Peel Values (lbs / Inch) / (g / cm X 102) 1 h 3.12 / 3.34 / 0.42 / 0.42 / 0.58 / 0.60 / 557 596 75 75 104 107 24 h. 3.34 / 3.38 / 0.24 / 0.28 / 0.60 / 0.92 / 596 604 42.9 50 107 164 TABLE 2 (CONT.) Bonding to canvas cloth substrate-DYLARK EXAMPLE / PAST A / 1 A / 2 B / l B / 2 C / l C / 2 % movement 0% 0% 2% 24% Failed Failed @ 180 ° F (9 (9 (87.8 ° C) min) min) % movement 2% 2% 4% 33% @ 200 ° F (93.3 ° C)% movement 2% 2% 7% 38% @ 220 ° F (104, 4 ° C)% movement 4% * 4% * 96% * 40% * @ 240 ° F (115, 5 ° C) Bonding to ABS-trilaminate substrate EXAMPLE / PAST A / 1 A / 2 B / l B / 2 C / l C / 2 Peel Values (lbs / Inch) / (g / cm X 102) 1 h 22.16 / 20.60 / 7.7 / 39.6 36.8 13.8 24 h 22, 92/28, 06/10 , 4/40, 9 50, 1 18, 6 Movement at 2 mm 40 mm 26 min 1 h @ 190 ° F (87, 8 ° C) Movement at 10 mm 1 h 45 min 5 h @ 190 ° F (87.8 ° C) * Substrate integrity failed. As can be seen from Examples A-C, the adhesive formulations of the present invention have excellent adhesive properties and provide strong adhesion with good heat resistance. The formulations according to the present invention are highly stable and can be used as packaged adhesive formulations. The following example D is an adhesive formulation within the scope of the present invention that does not include aziridine. This composition exhibited a desirable combination of stability and adhesion strength.

Example D Material Parts by weight Polyurethane (Example 1) 147.76 Ethylene / vinyl acetate 1 124.36 Plasticizer 2 37.20 Thickener 3 0.42 Aziridine cross-linker 0 Carbodiimide cross-linker 15,20 Dye5 0.52 Deionized water 20 1 AIRFLEX 300 ethylene / vinyl acetate copolymer from Air Products and Chemicals, Inc. 2 PLASTHALL B = A butylbenzenesulfonamide plasticizer obtainable from C.P. Hall Company. 3 RM 8 associative urethane thickener obtainable from Rohm & Haas. 4 UCARLINK XL-29SE carbodiimide crosslinker from Union Carbide. 5 AKROSPERSE E-98 blue dye from Arcochem Corp ..

It should be understood that the invention has been set forth with reference to specific embodiments for the purpose of describing the best mode of carrying out the invention, but it is intended that other variations and modifications that are apparent to those skilled in the art fall within the scope of the invention. of the scope of the invention defined by the claims.

Claims (5)

R e i v i n d i c a on i s

1 - . 1 - A water-based adhesive composition, including: (a) a cationic polyurethane dispersed in water having a polydispersity index of at least 20; and (b) a carbodiimide.

2. The composition of claim 1, further comprising an aziridine curing agent.

3. The composition of claim 1, further including a polymer of vinyl acetate or copolymer. 4. The composition of claim 1, wherein the polyurethane (a) includes cationic groups derived from amino groups. 5. The composition of claim 4, wherein the polyurethane (a) is the reaction product of a urethane prepolymer containing isocyanate groups reacted in solvent with isocyanate-reactive ketimide and polyamine, followed by hydrolysis of the ketimine and neutralization to form cationic amino groups . 6. The composition of claim 5, wherein ce-thymine is a diketimine. 7. The composition of claim 5, wherein the polyamine is a triamine. 8. The composition of claim 1, wherein said composition is stable for at least 30 days at 23 ° C. 9. The composition of claim 1, further including a plasticizing agent. 10. The composition of claim 8, including: 2

4-64 weight percent of a polyurethane dispersed in ionic water (a) based on the weight of resin solids; 0-48 weight percent vinyl acetate based on the weight of resin solids; 0-10 weight percent aziridine based on the weight of resin solids, 0.

5-10 weight percent carbodiimide; and 0-33 weight percent plasticizer based on the weight of resin solids. 11. The composition of claim 2, wherein said aziridine is trimethylolpropane-tris- (β- (n-aziridinyl) propionate). 12. The composition of claim 1, wherein the polydispersity index of the polyurethane is at least 25. 13. A water-borne polyurethane which is the reaction product of a urethane prepolymer containing isocyanate groups reacted in solvent with isocyanate-reactive ketimine and polyamine, wherein the ratio of polyamine to ketimine is in the order of 1: 1 to 4: 1 based on to equivalents of isocyanate-reactive groups, followed by hydrolysis of the ketimine and neutralization to form cationic amino groups. 14. The composition of claim 13, wherein the ketimine is a diketimine. 15. The composition of claim 13, wherein the polyamine is a triamine. 16. The composition of claim 13, wherein the polydispersity index of the polyurethane is at least 20. 17. The composition of claim 13, wherein the polydispersity index of the polyurethane is at least 25.