Patent Application
20220228045
The invention relates to moisture curable adhesive compositions useful for bonding glass into vehicles and buildings. In particular, the invention relates to moisture curable isocyanate terminated prepolymer adhesive compositions coupled with a separate cure accelerator having two curatives components having different cure kinetics, one having faster curing kinetics resulting an increase in bead stability within the first minutes and a with slower curing kinetics allowing for sufficient open time and yet a fast strength build up.
One-part moisture curing adhesive compositions have been used to bond windows into buildings and vehicles. Examples of adhesives useful for these applications are described in U.S. Pat. Nos. 4,374,237; 4,687,533; 4,780,520; 5,063,269; 5,623,044; 5,603,798; 5,922,809; 6,015,475; 6,512,033; 6,657,035; 6,709,539; 7,101, 950; 7,226,523; 7,361,292; 8,236,891; CA 2,564,992; and WO 2015/171307. In automobile factories windows are installed using robots and computer-controlled processing which facilitates the use of a variety of high-performance adhesives, for instance, nonconductive adhesives and high modulus adhesives. The speed of cure is not a significant issue because new vehicles are not driven any significant distance for several days after window installation.
In contrast, when a vehicle needs a window replaced, it is often driven shortly after. The replacement is often performed in a remote location by an installer working from a vehicle or otherwise under uncontrolled conditions. Consequently, speed of cure is important as the vehicle owner desires to drive the vehicle as soon as possible after installation of the window. One-part moisture curing adhesives useful in replacing windows for vehicles which facilitate fast drive away times have been described in U.S. Pat. Nos. 5,976,305; 6,709,539 and 7,226,523. Even though these adhesives have built up enough integrity to be driven away in a short time, they still have required much longer times to fully cure and inconsistently cured depending on the ambient conditions such as temperature and relative humidity.
Two-part compositions containing isocyanate functional compounds or prepolymers in one part and compounds and/or prepolymers having isocyanate reactive components have also been used. It is understood that the two parts commonly referred to as the A and B side have essentially the same volume. Examples of two-part compositions containing isocyanate functional compounds or prepolymers in one part and compounds and/or prepolymers having isocyanate reactive components in the other part are disclosed in EP 1,524,282, and U.S. Pat. Nos. 5,852,103; 6,709,539; 7,101,950 and 7,361,292. These tend to suffer, however, from complex delivery systems, to keep the two parts separate as well as requiring sufficient mixing when dispensing to realize a uniform product. Likewise, two-part adhesive compositions tend to react quickly and may form skins resulting in insufficient working time to allow proper positioning of the replacement window under certain conditions (higher temperatures and higher relative humidity). Thus, even though a two-part composition may allow automobiles with replacement windows to be driven within 30 minutes of bonding the window into the automobile, they have not in general allowed any quicker drive away times and care must be taken to ensure a uniform adhesive bead.
More recently, a two-part dual cure adhesive composition comprised of isocyanate terminated prepolymers in one part and an acrylic acrylate monomer in the other part has been described in WO 2012/151085. In this composition one part contains an isocyanate terminated polyether prepolymer and the other part contains a hydroperoxide compound and acrylic or acrylate monomer, where the hydroperoxide compound is reduced upon mixing with the other part forming free radicals to realize sufficient integrity from the development of an initial polyacrylic or polyacrylate matrix to allow relatively fast drive away times. However, the working time, consistency of the bead, workability, ultimate cure properties were less than desirable.
Thus, it would be desirable to have a rapid drive away adhesive for bonding glass into a structure that cures sufficiently to allow for driving away in a short amount of time such as even 15 minutes while also providing for consistent uniform adhesive beads and sufficient workability (time where the glass may be placed and manipulated and still have adequate adhesion) under varying ambient conditions.
In one embodiment, the present invention is an adhesive system comprised of, consisting essentially of, consisting of a moisture curable adhesive comprised of, consisting essentially of, consisting of: A) an isocyanate terminated prepolymer and B) a cure accelerator comprised of, consisting essentially of, consisting of: i) an isocyanate reactive compound comprising: 1) a primary, secondary or tertiary amino group, or a primary thiol group and 2) an OH, NH, and/or SH functionality of 2 to 7 and ii) a polyol not having a primary, secondary or tertiary amino group, or a primary thiol group wherein the polyol is selected from a diol and/or triol, preferably wherein component B) is essentially free of water.
In a preferred embodiment of the invention, the isocyanate reactive compound (i) has an OH, NH, and/or SH functionality of 2 to 4.5 and is present in an amount less than 5% by weight of the cure accelerator (B).
Another embodiment of the present invention is a method of accelerating the cure of an adhesive composition comprising, consisting essentially of, consisting of the steps of: a) providing a moisture curable adhesive composition comprised of: A) an isocyanate terminated prepolymer and B) a cure accelerator comprised of: i) an isocyanate reactive compound comprising: 1) a primary, secondary or tertiary amino group, or a primary thiol group and 2) an OH, NH, and/or SH functionality of 2 to 7 and ii) a polyol not having a primary, secondary or tertiary amino group, or a primary thiol group wherein the polyol is selected from a diol and/or triol, preferably wherein component B) is essentially free of water, wherein the isocyanate terminated prepolymer and cure accelerator are separately provided; b) mixing the cure accelerator and the isocyanate terminated prepolymer to form an adhesive mixture; c) applying the adhesive mixture to at least a portion of a first substrate; d) contacting the substrate having the adhesive mixture thereon with a second substrate such that the adhesive mixture is therebetween; and e) allowing the adhesive mixture to cure bonding said substrates together, preferably wherein the first substrate is a substrate wherein at least a portion of the substrate is optically transparent and the second substrate is a vehicle or building, more preferably wherein the first substrate has an opaque portion where the adhesive mixture is applied and contacted with the second substrate, preferably wherein the first substrate is glass or polycarbonate.
The present invention is the formulation of an accelerated polyurethane adhesive which cures independent of humidity and a method to use said accelerated polyurethane adhesive. The inventive adhesive shows the curing performance of a 2K adhesive in combination with application performance of a 1K adhesive using a standard 1K application gun typically used for 1K polyurethane adhesive cartridges or sausages or automated application equipment from drums.
In one embodiment, the inventive adhesive is applied using a 2 K packaging solution such as a peeler cartridge or a sausage in sausage solution both of which can be used in standard 1K application gun in combination with a static mixer, for example see U.S. Pat. No. 9,821,512, which is incorporated herein by reference. The use of a static mixer necessitates a low viscosity of both adhesive components to allow a sufficiently fast application speed.
In conventional adhesives, low viscosity of both components to allow for mixing with a static mixer typically resulted in a low stability of the bead against subsiding of a window, sometimes referred to as the decking performance. This invention addresses the use of a low viscosity adhesive formulations which build up strength quickly to allow shortly after adhesive application to deck the window onto the adhesive while at the same time, the buildup strength does not negatively affect the open time of the adhesive. This results in a length of time starting when the adhesive has sufficient strength to hold a window (decking height ≤5.5mm) and the time at which the strength of the adhesive bead becomes too high to squeeze the window into the adhesive bead (decking height ≥1.7 mm) to be at least 10 min or greater. This is achieved in the inventive adhesive by formulating the polyol component with two curatives having different kinetics, one which is “fast” resulting an increase in bead stability within the first minutes and a second curative which has a “slow” curing kinetic allowing for sufficient open time and yet still a fast strength build up. The fast curative is an isocyanate reactive compound, preferably a polyol comprising an amine, preferably a primary, secondary or tertiary amino group and/or a thiol, preferably a primary thio group, wherein the isocyanate reactive compound preferably has an OH, NH, and/or SH functionality of 2 to 7. The slow curative is a polyol not having a primary, secondary or tertiary amino group, or a primary thiol group selected from a diol or a triol, for example a polyether diol or an alkyldiols (e.g., 1,4-butanediol).
It has been discovered that the moisture curable adhesive composition of the present invention comprising an isocyanate terminated prepolymer may be cured in substantially less time while still having sufficient working time and final cured properties desired for installing aftermarket glass when repairing chipped or broken glass in vehicles. Illustratively, the adhesive mixture may have a working time on the order of 5, 8, 10, or even 15 minutes, while being essentially cured in 60 minutes. Likewise, the method of the present invention allows for consistent application of these moisture curable adhesives under widely different ambient conditions.
The adhesive system of the invention may be used to bond a variety of substrates together. Examples of substrates include plastic, glass, wood, ceramics, metal, and coated substrates, such as plastics coated with an abrasion resistant coating. The adhesive system of the invention may be used to bond similar and dissimilar substrates together. The adhesives are especially useful for bonding glass or a plastic with an abrasion resistant coating disposed thereon to other substrates such as vehicles (e.g., automobiles) and buildings. The compositions of the invention are also useful in bonding parts of modular components together, such as vehicle modular components. The glass or plastic coated with an abrasion resistant coating may be bonded to coated and uncoated portions of vehicles.
The compositions of the invention are especially useful in bonding replacement windows into structures. The adhesive is pumpable, sag resistant and bonds parts together at temperatures between −10° C. and 45° C. Preferably, the composition has a sag of an uncured sample of less than 2 mm and decking force of between 1.5 pounds and 15 pounds under typical ambient conditions (i.e., temperatures of −10° C. to 35° C. and relative humidities of 25% to 75%). Preferably, the decking height between the time when the adhesive has sufficient strength to hold a window to the time at which the strength of the adhesive bead is high enough to squeeze the window into the adhesive bead is equal to or less than 5.5mm to equal to or greater than 1.0 mm.
This allows the adhesives prepared from the composition of the invention to be applied at a wide range of ambient temperatures. Heating the material is not necessary for the application of the adhesive. It has been surprisingly discovered that the adhesive system can offer the unique combination of realizing a suitable decking force to allow placement of the windshield shortly after application and for a sufficient time to allow repositioning coupled with a fast cure allowing for a vehicle to be driven away even after only 30 minutes.
“Nominal” as used with respect to functionality means the theoretical functionality, generally this can be calculated from the stoichiometry of the ingredients used. Generally, the actual functionality is different due to imperfections in raw material, incomplete conversion of the reactants and formation of bi-products.
Preferable polyisocyanates for use in preparing the prepolymer include those disclosed in U.S. Pat. No. 5,922,809 at col. 3, line 32 to column 4, line 24, incorporated herein by reference. Preferably, the polyisocyanate is an aromatic or cycloaliphatic polyisocyanate such as diphenylmethane-4,4′-diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, and is most preferably diphenylmethane-4,4′-diisocyanate. The diols and triols are generically referred to as polyols.
The prepolymers are made from polyols such as diols and triols such as those described in U.S. Pat. No. 5,922,809 at column 4, line 60 to column 5, line 50. The polyols (diols and triols) are preferably polyether polyols and more preferably polyoxyalkylene oxide polyols. The most preferred triols are ethylene oxide-capped polyols prepared by reacting glycerin with propylene oxide, followed by reacting the product with ethylene oxide.
It is also understood that a small amount of other polyols may be used to form the polyether prepolymer such as a polyester polyol such as those known in the art. Typically, such other polyols may be present in an amount of up to 5% by weight of the polyols used to make said prepolymer. However, said prepolymer may be made in the absence of such polyols.
The isocyanate terminated prepolymers may be prepared by any suitable method, such as bulk polymerization and solution polymerization. The reaction to prepare the prepolymer is carried out under anhydrous conditions, preferably under an inert atmosphere such as a nitrogen blanket and to prevent crosslinking of the isocyanate groups by atmospheric moisture. The reaction is preferably carried out at a temperature between 0° C. and 150° C., more preferably between 25° C. and 90° C., until the residual isocyanate content determined by titration of a sample is very close to the desired theoretical value. “Isocyanate content” means the weight percentage of isocyanate moieties to the total weight of the prepolymer. The reactions to prepare the prepolymer may be carried out in the presence of urethane catalysts. Examples of such include the stannous salts of carboxylic acids, such as stannous octoate, stannous oleate, stannous acetate, and stannous laurate. Also, dialkyltin dicarboxylates such as dibutyltin dilaurate and dibutyltin diacetate are known in the art as urethane catalysts, as are tertiary amines and tin mercaptides. Preferably, the reaction to prepare the prepolymer is catalyzed by stannous octoate. The amount of catalyst employed is generally between 0.005 and 5 parts by weight of the mixture catalyzed, depending on the nature of the isocyanate. Preferably, the reaction is carried out in admixture with a plasticizer further described below.
The moisture curable adhesive generally is also comprised of a filler such as a carbon black. The carbon blacks depending on their structure and the molecular weight of the prepolymers may range over a wide range of structures as given by oil absorption number (ASTM D-2414-09). For example, the carbon black typically desirably has an oil absorption number (OAN) of 80 to 200 ccs per 100 grams. Preferably, the oil absorption of the carbon is at least 90, more preferably at least 100, and most preferably at least 110 to preferably at most 180, more preferably at most 165 and most preferably at most 150 ccs/100 grams.
The amount of carbon black suitable may be determined for a given carbon black. Typically, the amount of carbon black is at least in ascending desirability, 10%, 15%, to at most, in ascending desirability, 38%, 35%, 32%, 30% or 28% by weight of the adhesive composition.
The carbon black used may be a standard carbon black which is not specially treated to render it nonconductive. Standard carbon black is carbon black which is not specifically surface treated or oxidized. Alternatively, one or more nonconductive carbon blacks may be used exclusively or in conjunction with the standard carbon black. Suitable standard carbon blacks include RAVEN™ 790, RAVEN™450, RAVEN™ 500, RAVEN™ 430, RAVEN™ 420 and RAVEN™ 410 carbon blacks available from Colombian and CSX carbon blacks such as ELFTEX S5100 and S7100 and MONARCH 120, 570, and 590 available from Cabot, and PRINTEX™ 30 carbon black available from Evonik Industries, Mobile, Ala. Suitable non-conductive carbon blacks include RAVEN™ 1040 and RAVEN™ 1060 carbon black available from Colombian Chemicals Company, Marietta, Ga.
The moisture curable adhesive may also be comprised of reactive silicon. The reactive silicon may be present as a separate molecule such as a silane. It may be present within the backbone or as a terminal group in the prepolymer described above. The reactive silicon generally is one that can undergo hydrolysis such as described at column 4, lines 25 to 55 of U.S. Pat. No. 6,613,816. Other illustrative reactive silicones are described in USP Publication 2002/0100550 paragraphs 0055 to 0065 and Hsieh, U.S. Pat. No. 6,015,475, column 5, line 27 to column 6, line 41.
The amount of reactive silicon, when present in the moisture curable adhesive is, generally, 0.001% to 2% by weight of the total weight of the adhesive composition. The amount of the reactive silicon (note, the weight of the silicon itself and does not include, for example, the organic groups appended thereto), may be at least 0.005%, 0.01%, 0.02%, 0.04%, 0.06%, 0.08% or 0.1% to at most 1.8%, 1.6%, 1.4%, 1.2%, 1%, 0.8%, 0.5% of the adhesive composition.
The moisture curable adhesive may also be comprised of one or more organic based polymers dispersed therein. Preferably, the organic based polymer is included in the prepolymer by inclusion of a dispersion triol having dispersed therein particles of an organic based polymer. Dispersion triols typically understood to have at least a portion of the particles being grafted with the polyol. The preferable dispersion triols are disclosed in Zhou, U.S. Pat. No. 6,709,539 at column 4, line 13 to column 6, line 18, incorporated herein by reference. Preferably, the triol used to disperse the organic particles is a polyether triol and more preferably a polyoxyalkylene based triol. Preferably, such polyoxyalkylene oxide triol comprises a polyoxypropylene chain with a polyoxyethylene end cap. Preferably, the triols used have a molecular weight of 3,000 or greater, more preferably 4,000 or greater and most preferably 5,000 or greater. Preferably, such triol has molecular weight of 8,000 or less and more preferably 7,000 or less. It is understood that the polyol of the dispersion polyol (e.g., triol) is included in the polyol to make the prepolymer composition described herein, where the copolymer particles of the dispersion polyol are understood to be fillers in the composition.
The moisture curable adhesive typically is further comprised of a plasticizer. The plasticizers may be used so as to modify the rheological properties to a desired consistency. Such materials should be free of water and be inert to isocyanate groups. The plasticizers may be common plasticizers useful in polyurethane adhesive applications and well known to those skilled in the art and are referred to hereinafter as low polar plasticizers. The plasticizer is present in an amount sufficient to disperse the isocyanate terminated prepolymer. The plasticizer can be added to the prepolymer either during preparation of the prepolymer or during compounding of the prepolymer prior to being placed into the first compartment. Preferably, the plasticizer is present in 1 percent by weight or greater of the prepolymer formulation (prepolymer plus plasticizer), more preferably 20 percent by weight or greater and most preferably 30 percent by weight or greater. Preferably, the plasticizer is present in 45 percent by weight or less of the prepolymer formulation and more preferably 35 percent by weight or less.
Preferably two plasticizers are used, with one being a high polar plasticizer and one being a low polar plasticizer. A high polar plasticizer is a plasticizer with a polarity greater than the polarity of the aromatic diesters, such as the phthalate esters. A low polar plasticizer is a plasticizer which has a polarity the same as or less than the aromatic diesters.
Suitable high polar plasticizers include one or more of alkyl esters of sulfonic acid, alkyl alkylethers diesters, polyester resins, polyglycol diesters, polymeric polyesters, tricarboxylic esters, dialkylether diesters, dialkylether aromatic esters, aromatic phosphate esters, and aromatic sulfonamides. More preferred high polar plasticizers include aromatic sulfonamides, aromatic phosphate esters, dialkyl ether aromatic esters and alkyl esters of sulfonic acid. Most preferred high polar plasticizers include alkyl esters of sulfonic acid and toluene-sulfamide. Alkyl esters of sulfonic acid include alkylsulphonic phenyl ester available from Lanxess under the trademark MESAMOLL. Aromatic phosphate esters include PHOSFLEX™ 31 L isopropylated triphenyl phosphate ester, DISFLAMOLL™ DPO diphenyl-2-ethyl hexyl phosphate, and DISFLAMOL™ TKP tricresyl phosphate. Dialkylether aromatic esters include BENZOFLE™ 2-45 diethylene glycol dibenzoate. Aromatic sulfonamides include KETJENFLE™ 8 o and p, N-ethyl toluenesulfonamide.
Suitable low polar plasticizers include one or more aromatic diesters, aromatic triesters, aliphatic diesters, epoxidized esters, epoxidized oils, chlorinated hydrocarbons, aromatic oils, alkylether monoesters, naphthenic oils, alkyl monoesters, glyceride oils, parraffinic oils and silicone oils. Preferred low polar plasticizers include alkyl phthalates, such as diisononyl phthalates, dioctylphthalate and dibutylphthalate, partially hydrogenated terpene commercially available as “HB-40”, epoxy plasticizers, chloroparaffins, adipic acid esters, castor oil, toluene and alkyl naphthalenes. The most preferred low polar plasticizers are the alkyl phthalates.
The amount of low polar plasticizer in the adhesive composition is that amount which gives the desired rheological properties, and which is sufficient to disperse the catalyst in the system. The amounts disclosed herein include those amounts added during preparation of the prepolymer and during compounding of the adhesive. Preferably, low polar plasticizers are used in an amount of 5 parts by weight or greater based on the weight of moisture curable adhesive, more preferably 10 parts by weight or greater, and most preferably 18 parts by weight or greater. The low polar plasticizer is preferably used in an amount of 40 parts by weight or less based on the total amount of moisture curable adhesive, more preferably 35 parts by weight or less and most preferably 30 parts by weight or less.
The amount of high polar plasticizer in the moisture curable adhesive is that amount which gives the desired rheological properties and the acceptable sag and string properties of the dispensed moisture curable adhesive. Preferably, if used, the high polar plasticizers are used in the moisture curable adhesive in an amount of 0.2 parts by weight or greater based on the weight of moisture curable adhesive, more preferably 0.5 parts by weight or greater, and most preferably 1 part by weight or greater. The high polar plasticizer is preferably used in an amount of 20 parts by weight or less based on the total amount of the moisture curable adhesive, more preferably 12 parts by weight or less and most preferably 8 parts by weight or less.
The moisture curable adhesive may further comprise a polyfunctional isocyanate, for example, to improve the modulus of the composition in the cured form or adhesion of the adhesion composition to particular substrates such as painted substrates. “Polyfunctional” as used in the context of the isocyanates refers to isocyanates having a functionality of 2 or greater. The polyisocyanates can be any monomeric, oligomeric or polymeric isocyanate having a nominal functionality of 2 or greater. More preferably, the polyfunctional isocyanate has a nominal functionality of 2.7 or greater. Preferably, the polyfunctional isocyanate has a nominal functionality of 5 or less, even more preferably 4.5 or less and most preferably 3.5 or less.
The polyisocyanates may be monomeric; trimeric isocyanurates or biurets of monomeric isocyanates; oligomeric or polymeric, the reaction product of several units of one or more monomeric isocyanates. Examples of preferred polyfunctional isocyanates include trimers of hexamethylene diisocyanate, such as those available from Bayer under the trademark and designation DESMODUR N3300 and N100, and polymeric isocyanates such as polymeric MDI (methylene diphenyl diisocyanates) such as those marketed by The Dow Chemical Company under the trademark of PAPI, including PAPI 580N polymeric isocyanate. The polyfunctional isocyanates, when present are typically present in an amount sufficient to impact the modulus of the cured compositions of the invention or improve the adhesion to certain substrates described above.
The polyfunctional isocyanate, when present, is preferably present in an amount of 0.5 parts by weight or greater based on the weight of the moisture curable adhesive, more preferably 1.0 parts by weight or greater and most preferably 2 parts by weight or greater. The polyfunctional isocyanate is preferably present in an amount of 12 parts by weight or less, based on the weight of the moisture curable adhesive, more preferably 8 parts by weight or less and most preferably 4 parts by weight or less.
The moisture curable adhesive may also be comprised of a catalyst that catalyzes the reaction of isocyanate moieties with water or an active hydrogen containing compound. Such compounds are well known in the art. The catalyst can be any catalyst known to the skilled artisan for the reaction of isocyanate moieties with water or active hydrogen-containing compounds. Among preferred catalysts are organotin compounds, metal alkanoates, and tertiary amines. Mixtures of classes of catalysts may be used. A mixture of a tertiary amine and a metal salt is preferred. Even more preferred are tertiary amines, such as dimorpholino diethyl ether or triethylenediamine, and a metal alkanoate, such as bismuth octoate or dimethyltin dineodecanoate. Included in the useful catalysts are organotin compounds such as alkyl tin oxides, stannous alkanoates, dialkyl tin carboxylates and tin mercaptides. Stannous alkanoates include stannous octoate. Alkyl tin oxides include dialkyl tin oxides, such as dibutyl tin oxide and its derivatives. The organotin catalyst is preferably a dialkyltin dicarboxylate or a dialkyltin dimercaptide. Dialkyltin dicarboxylates with lower total carbon atoms are preferred as they are more active catalysts in the compositions of the invention. The preferred dialkyl dicarboxylates include 1,1-di-methyltin dilaurate, 1,1-dibutyltin diacetate and 1,1-dimethyl dimaleate. Preferred metal alkanoates include bismuth octoate or bismuth neodecanoate.
The organotin or metal alkanoate catalyst, as percentage of the total weight of the moisture curable adhesive, is present, generally, in an amount of 60 parts per million or greater, preferably 120 parts by million or greater to at most 1.0 percent, preferably 0.5 percent by weight and more preferably 0.1 percent.
Useful tertiary amine catalysts include dimorpholinodialkyl ether, a di((dialkylmorpholino)alkyl) ether, bis-(2-dimethylaminoethyl)ether, triethylene diamine, pentamethyldiethylene triamine, N,N-dimethylcyclohexylamine, N,N-dimethyl piperazine 4-methoxyethyl morpholine, N-methylmorpholine, N-ethyl morpholine and mixtures thereof. A preferred dimorpholinodialkyl ether is dimorpholinodiethyl ether. A preferred di((dialkylmorpholino)alkyl) ether is (di-(2-(3,5-dimethylmorpholino)ethyl)ether). Tertiary amines, if used, are preferably employed in an amount, based on the weight of the moisture curable adhesive of 0.01 parts by weight or greater, more preferably 0.05 parts by weight or greater, even more preferably 0.1 parts by weight or greater and most preferably 0.2 parts by weight or greater and 2.0 parts by weight or less, more preferably 1.75 parts by weight or less, even more preferably 1.0 parts by weight or less and most preferably 0.4 parts by weight or less.
The moisture curable adhesive may be formulated with fillers other than the carbon black and additives known in the prior art for use in adhesive compositions. By the addition of such materials, physical properties such as viscosity flow rates and the like can be modified. However, to prevent premature hydrolysis of the moisture sensitive groups of the isocyanate terminated prepolymer, fillers should be thoroughly dried before admixture therewith. Other exemplary fillers include clay, titanium dioxide, calcium carbonate, surface treated silica, titanium oxide, fumed silica, talc, wollastonite, and the like. In one embodiment, more than one reinforcing filler may be used.
The moisture curable adhesive may also have a stabilizer that inhibits and prevents premature crosslinking of the isocyanates in the adhesive. Stabilizers known to the skilled artisan for moisture curing adhesives may be used. Examples of stabilizers include diethylmalonate, alkylphenol alkylates, paratoluene sulfonic isocyanates, benzoyl chloride and orthoalkyl formates. Stabilizers are typically used in an amount of 0.1 parts by weight or greater based on the total weight of moisture curable adhesive, preferably 0.5 parts by weight or greater and more preferably 0.8 parts by weight or greater. Such stabilizers are used in an amount of 5.0 parts by weight or less based on the weight of the adhesive, more preferably 2.0 parts by weight or less and most preferably 1.4 parts by weight or less.
Other components commonly used in adhesive compositions may be used in the moisture curable adhesive. Such materials are well known to those skilled in the art and may include ultraviolet stabilizers, antioxidants, heat stabilizers and the like.
The moisture curable adhesive may be formulated by blending the components together using means well known in the art. Generally, the components are blended in a suitable mixer. Such blending is preferably conducted in an inert atmosphere in the absence of oxygen and atmospheric moisture to prevent premature reaction. In embodiments where a substantial amount of polyester-based isocyanate functional prepolymer is used, the adhesive compositions may be blended at a temperature above the melting point of the polyester-based isocyanate functional prepolymer and below a temperature at which significant side reactions occur. In this embodiment, the temperatures utilized are from 40° C. to less than 90° C., and more preferably 50° C. to 70° C. Once the adhesive composition is formulated, it is packaged in a suitable container such that it is protected from atmospheric moisture and oxygen. Contact with atmospheric moisture and oxygen could result in premature crosslinking of the polyurethane prepolymer-containing isocyanate groups.
The adhesive system is also comprised of a fast cure accelerator comprised of an isocyanate reactive compound, such as a polyether or a polyol, having an amino group in the backbone of the polyol. Said isocyanate reactive compound may have terminal OH groups and at least one amino group in its backbone. The isocyanate reactive compound having an amino group generally has an average OH functionality (total moles OH/total moles polyol) of greater than 2 to 5. The average OH functionality is preferably equal to or greater than 2.2, 2.5, 3.0, 3.5, or 3.8 and equal to or less than 4.8, 4.5 or 4.2.
The isocyanate reactive compound having an amino group has at least one amino group within its backbone. The backbone may be the same as described above for polyols used to make the isocyanate terminated prepolymer (e.g., aliphatic, polyether or polyester backbones). The isocyanate reactive compound having an amino group may be formed by initiating the formation of a polyol using a polyfunctional amine compound. Generally, the amino groups present in the backbone are essentially all tertiary amines.
The average amount of amino groups in the isocyanate reactive compound having an amino group generally is from 1 to 6. Preferably, the average amount of amino groups present in the polyol having an amino group is at least 1.5, 2, 3.0, 3.5, or 3.8 to at most 4.8, 4.5 or 4.2.
Likewise, the OH number (OH#) of the isocyanate reactive compound having an amino group may be any useful to realize the desired cure rate and workability. Generally, the OH# is at least 25 to 2000. Preferably, the OH number is at least 100, 250, 500 or even 550. The OH number arises from a wet analytical method for the hydroxyl content of a polyol; it is the milligrams of potassium hydroxide equivalent to the hydroxyl content in one gram of polyol or other hydroxyl compound and is given by the below equation:
where 56.1 is the atomic weight of potassium hydroxide and 1000 is the number of milligrams in one gram of sample.
The isocyanate reactive compound having an amino group may also have any useful molecular weight. Generally, the molecular weight of said polyol is at least 200 to 10,000. Preferably the molecular weight is at most 5000, 3000, 1500, 1000, 500 or even 400. Preferably the molecular weight is at least 100, 200 or 250. In a preferred embodiment, the isocyanate reactive compound having an amino group has an average OH functionality of 3.5 to 4.2 and OH number of at least 500.
The cure accelerator may be comprised of a small amount of water so long that it does not deleteriously affect the cure rate, workability and cured properties of the adhesive mixture arising, for example, by causing bubbling. The amount of water in the cure accelerator, generally, is less than 1% based upon the total weight of the cure accelerator and the moisture curable adhesive. Typically, it is desirable for the amount of water to be as low as practicable such as only trace amounts such as 500 parts per million by weight of the total weight of the moisture curable adhesive and cure accelerator. Preferably, the amount of water is at most 100 ppm to no water or essentially no water using known methods for determining water content.
The cure accelerator may contain one or more of other ingredients such as filler, a polyol not having an amino group in the backbone, a catalyst, plasticizer, rheological modifier, UV stabilizers or other useful ingredients used moisture curable adhesives. The fillers, polyols, plasticizer and catalysts may be any one of those described previously or known in the art. The amount of each of these may be determined by the desired amount of isocyanate reactive groups (e.g., OH) and other physical characteristics such as rheological properties, which may be useful to ensure uniform mixing and applying of the adhesive system.
When a filler, polyol not containing an amino group, catalyst and plasticizer are contained in the cure accelerator they will typically be present in amounts as follows. The isocyanate reactive compound with the amino group typically will be present in an amount of 5% to 50% by weight by weight of the cure accelerator. The polyol without an amino group will typically present in an amount of 20% to 80% by weight of the cure accelerator. The filler or combination of fillers will typically be present in an amount of 10% to 35% of the cure accelerator. The catalyst or combination of catalyst will typically present in an amount of 0.01% to 2% of the cure accelerator.
The cure accelerator is used to accelerate the cure of a moisture curable adhesive. When doing so, the cure accelerator and moisture curable adhesive are provided separately, otherwise they will react prior to application. Any suitable method of providing two reactive materials having different volumes that are later mixed may be used such as those known in the art and described in copending application U.S. Application No. 61/977668, filed Apr. 10, 2014 to Zhu et. al., from page 1, line 10 to page 2, line 8. Preferably, the moisture curable adhesive and cure accelerator are provided in the two-component reactive dispensing system described in the aforementioned US Application.
Because the moisture curable adhesive is comprised of an isocyanate terminated prepolymer and is moisture curable, the isocyanate index of the adhesive system (i.e., the amount of isocyanates/reactive groups in the cure accelerator multiplied by 100) is generally 85 to 200, but preferably is 100 to 170. Likewise, because of the use of a moisture curable adhesive, generally, the volume ratio of cure accelerator to the moisture curable adhesive is 5 or 10 to 200, 100, 50 or 20. The iso index is essentially the same for all the examples and comparative examples.
The mixing, applying, contacting and allowing to cure of the moisture curable adhesive and cure accelerator may be accomplished by any suitable method such as those known in the art including those described in the aforementioned US Application. Preferably, the mixing, applying, contacting are performed using the method of the above US Application.
The adhesive system of the invention may be used to bond a variety of substrates together. The adhesive system may be used to bond porous and nonporous substrates together. The adhesive system is applied to a substrate and the adhesive on the first substrate is thereafter contacted with a second substrate. In preferred embodiments, the surfaces to which the adhesive is applied are cleaned and may be primed prior to application, but the primer is not necessary, see for example, U.S. Pat. Nos. 4,525,511; 3,707,521 and 3,779,794; for typical practices of application.
Generally, the adhesive system is applied at typical ambient conditions (23° C. ±10° C.) in the presence of atmospheric moisture (typically a relative humidity of 20% to 99%). For the purposes of testing the curing behavior, an RH of 50%±5% at 23° C.±2° C. is suitable. Curing may be accelerated by the addition of additional water in the atmosphere or by applying heat during curing of the adhesive by means of convection heat, microwave heating and the like.
The adhesive system is preferably used to bond glass or plastic coated with an abrasion resistant coating, to other substrates such as metal or plastics. In a preferred embodiment, the first substrate is a glass, or plastic coated with an abrasion resistant coating, window and the second substrate is a window frame. In another preferred embodiment, the first substrate is a glass, or plastic coated with an abrasion resistant coating, window and the second substrate is a window frame of an automobile. Preferably, the glass window is cleaned prior to bonding. The plastic coated with an abrasion resistant coating can be any plastic which is clear, such as polycarbonate, acrylics, hydrogenated polystyrene or hydrogenated styrene conjugated diene block copolymers having greater than 50 percent styrene content. The coating can comprise any coating which is abrasion resistant such as a polysiloxane coating. Preferably, the coating has an ultraviolet pigmented light blocking additive. Preferably, the glass or plastic window has an opaque coating disposed in the region to be contacted with the adhesive to block UV light from reaching the adhesive.
In a preferred embodiment, the adhesive system is used to replace windows in structures or vehicles and most preferably in vehicles. The first step is removal of the previous window. This can be achieved by cutting the bead of the adhesive holding the old window in place and then removing the old window. Thereafter, the new window is cleaned and, if desired, primed. The old adhesive that is located on the window flange can be removed, although it is not necessary, and, in most cases, it is left in place, but may be cut flat with a cutting tool. The window flange may be primed with a paint primer but is not necessary. The adhesive system is applied in a bead to the periphery of the window located such that it will contact the window flange when placed in the vehicle. The window with the adhesive located thereon is then placed into the flange with the adhesive located between the window and the flange. Alternatively, the adhesive may be applied to the window flange. The adhesive bead is a continuous bead that functions to seal the junction between the window and the window flange. A continuous bead of adhesive is a bead that is located such that the bead connects at each end to form a continuous seal between the window and the flange when contacted. Thereafter the adhesive is allowed to cure.
The adhesive system is also useful for bonding large mass substrates of more than 20 Kg, up to 120 Kg, to other substrates. In one class of large mass substrates, the substrates are large windows such as those utilized in mass transportation vehicles (e.g., buses or trains).
In certain applications, the adhesive system may be utilized with a primer or activation wipe. The primer or activation wipe is typically applied to the surface of a substrate. Any solvent is allowed to volatilize away and then the adhesive system is contacted with the substrate. Preferably, the time period from application of the primer or activation wipe to application of the adhesive system to the substrate is 0.5 minutes or greater, more preferably 1 minute or greater and most preferably 2 minutes or greater.
The following examples are provided to illustrate the invention but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated. The raw materials used in the moisture curable adhesive and non-reactive components used in the cure accelerator are shown in Table 1.
Examples 1 and 2 are isocyanate components (A-Side) formulated to have the same Ballan viscosity having the following composition, amounts are by weigh percent. The compositions of Examples 1 and 2 are shown in Table 2. In Table 2, Ballan viscosity is measured from materials conditioned at 23° C. Measuring cup and material in storage container are conditioned in a water bath at 23° C. for a minimum of 1 hour. After air-free transfer of the material in the measurement cup, the cup is mounted to the ballan measuring device. The adhesive is extruded through a 2 mm diameter, 1.8 mm length nozzle at 4±0.01 bar pressure. The extruded weight per time is measured. Press flow viscosities are calculated in g/min.
Examples 3 to 6 are polyol components (B-Side) comprising the curatives. The components amounts are listed as weight percent.
Example 3 contains only “slow” curatives (i.e., 1,4-butane diol in combination with a higher molecular weight polyether triol).
Example 4 to 6 comprise both a “slow” curative a “fast” curative which reacts directly after mixing with the isocyanate groups of the isocyanate component. In Examples 4 and 5 the fast curative is a polyether diamine, in increasing amounts.
Example 6 comprises an alcohol containing a tertiary amine which Intramolecularly catalyzes the alcohol reaction with the isocyanate rendering these OH groups faster than respective OH groups of 1,4-butane diol.
The compositions of Examples 3 and 6 are shown in Table 3.
Referring to Table2, the isocyanate components Ex. 1 and Ex. 2 are made by the following procedure: Components 1 and 3 are added to the mixer and degassed under vacuum for 40 minutes. Item 4, after being predried, is added to the mixer and mixed for 5 minutes at slow speed under vacuum until they are sufficiently wetted by the other items. The speed of the mixer is slowly increased to disperse item 4 (carbon black) for 40 minutes under full vacuum. Then the mixture is heated to 65° C. under stirring. Component 2 is added after it is preheated to the same temperature of 65° C. Then the heating is turned and cooling is activated to cool down to 40° C. Then the components 5 to 10 are added and mixed for a further hour under vacuum. The mixer is then cooled to ambient temperature and the moisture curable adhesive is discharged into a container under dry conditions.
Table 4 shows the cure accelerator Example and Comparative Examples. Each of these is made by essentially the same procedure as follows. Referring to Table 3, the components 1 and 4 are added to a mixer and degassed under vacuum for 30 minutes. Then the pre-dried components 5 to 8 are added and mixed slowly for 5 minutes at slow speed under vacuum until they are sufficiently wetted by the other items. The speed of the mixer is slowly increased to disperse the added components 5 to 8 for 40 minutes under full vacuum. Finally, the items 2 and 3 are added and mixed under vacuum for 20 minutes. The mixture is then discharged into a sealed container.
Each of the cure accelerator formulations shown in Table 4 are placed into an adhesive dispensing system (two component sausage) with the above moisture curable adhesive as described in Example 1 of US Application No. 61/977668 described above. The volumetric ratio of the moisture curable adhesive to the cure accelerator is 9 to 1. For each Example and Comparative Example, the isocyanate index is essentially the same. The moisture curable adhesive and cure accelerator are dispensed in the same manner as described in Example 1 of the aforementioned US Application.
The compositions of Comparative Example A and Examples 8 to 11 are shown in Table 4.
The following properties for Comparative Example A and Examples 8 to 11 are measured and also reported in Table 4:
“Decking” performance is measured using a penetrometer. A triangular shaped adhesive bead is applied with a nozzle having a triangular shape with a base of 7 mm and a height of 14 mm. A weight of 115 g (100 g weight+15 g connecting rod) is hold in placed precisely on the tip of the adhesive bead. The grip on the weight is released for 5 seconds and allowed to sink into the adhesive bead. The depth of penetration is measured in millimeters. The penetration depth is measured directly 1 minute after application of the adhesive bead and then every 2 minutes until it is not anymore possible to easily squeeze the adhesive. The decking performance directly after the adhesive is mixed in the static mixer at time 0 is predicted by a linear approximation of the penetration depth in the time in which the adhesive can be squeezed or at maximum the first 20 minutes;
“Impact strength” is determined via GEX method 344. Metal coupons are placed in a sample holder. The adhesive is applied between the prongs so that it overflows onto tape. Afterwards, coupons (76×25×5 mm) are placed on top of the prongs and the over standing adhesive is removed slowly with a spatula and it is endured that the bead is of perfect shape (25×13×5 mm). After that, the test specimens are stored for the desired cure time (e.g. 15 min & 30 min) and environmental conditions. Then, the impact pendulum is brought up and latched, the test specimen fixed in position and the hammer released (with a 10 lb hammer). The total energy that the adhesive can withstand, prior to destructive failure is measured in J;
“Lap shear strength” is measured according to DIN EN 527 on a suitable device, e.g., shear strength device Zwick 1435 with an FHM 8606.00.00 or 8606.04.00 mounting device. Adhesive bond dimension of 10×25×1.5 mm are used for the lap shear specimens. Lap shear specimens are tested after 1 h, 2 h, 4 h and 7 d curing time at 23° C./50% relative humidity; and
“Tensile Properties: Strength, Elongation, and E Modulus” are determined according to DIN EN ISO 527-1.
To analyze the effect of the fast curative on the decking performance, the reduction of decking height over 20 minutes or the opentime of the adhesive has been linearly approximated,
The linear approximated decking height at 0 min of Comparative Example A with 7.3 mm is higher than the one of the inventive Example 8, with 6.5 mm. The incorporation of 10% of Jeffamine SD-2001 a secondary polyether diamine into the accelerator component results in a reduction of initial decking height of 11%.
As shown in
Examples 9 and 11 employ the inventive polyol component Example 6 which contains triethanol amine as the fast curative. The linear approximated decking height at 0 min is with 5.3 mm and 5.0 mm comparable (
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US20/38331 | 6/18/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62866022 | Jun 2019 | US |
