2K-Low Modulus Polyurethane Adhesive for Bonding Composite Materials

Abstract

This invention relates to polyurethane adhesive compositions, laminated articles comprising one such adhesive composition, and methods for preparing such laminated articles. The adhesive may be a two-component adhesive. The adhesive may be a structural adhesive. A two-component polyurethane adhesive composition comprises: a. a prepolymer component and a curing agent component, wherein the prepolymer comprises (i) at least about 30 wt% of a polyol component, preferably at most not more than about 70 wt%, more preferably at least about 40 wt%, more preferably at least about 45 wt%, and even more preferably at least about 50 wt%; and b. the adhesive composition comprises at least 0.05 wt% of an amine-free / tin-free catalyst, and preferably less than 0.7 wt% of a tin-containing catalyst.

Description

Technical Field

[0001] This invention relates to adhesive compositions that can be used as structural adhesives. In particular, it can be used to bond dissimilar or similar materials, such as bonding polycarbonate materials to other polycarbonate or non-polycarbonate materials; and laminated articles formed by bonding such materials and methods for preparing such laminated articles. Technical Background

[0002] In 2012, the U.S. Environmental Protection Agency (EPA) set a requirement that U.S. vehicles achieve an average fuel efficiency of 54.5 miles per gallon by 2025. To meet this stringent standard, the automotive industry has turned to materials that can reduce vehicle weight. This can include bonding dissimilar materials together. Polycarbonate is an exemplary material suitable for such applications.

[0003] Typically, industrial adhesives used to bond dissimilar materials must possess not only excellent adhesion but also appropriate modulus and high elongation. To meet these requirements, significant amounts of plasticizers and toughening agents are added to the polymerizable adhesive composition. Furthermore, a primer is applied to some materials to achieve good adhesion.

[0004] Bonding dissimilar materials presents significant challenges for industrial adhesives. Different substrates have different coefficients of thermal expansion. When the materials are heated, they expand at different rates, generating stress. One example of such laminates is a laminate bonded to aluminum and glass. The difference in the rates of expansion and contraction of the materials can cause the glass to break.

[0005] In conventional practice, mixtures of amine and tin catalysts are frequently used to formulate polyurethane adhesives to provide good mechanical bonding properties. Traditionally, tertiary amines have been the preferred catalysts for polyurethane reactions. However, the use of tertiary amines presents complexities due to their significant volatility. The volatility of amines is considered a source of unpleasant odors, which can be quite noticeable during manufacturing. Furthermore, tertiary amines can induce polycarbonate cracking when exposed to stress and certain conditions, posing a significant challenge. Meanwhile, tin catalysts exhibit significant selectivity in catalyzing isocyanate-hydroxyl reactions in adhesive systems. However, the widespread adoption of tin compounds has been hampered by perceived health concerns associated with their use, as disclosed in the ATSDR August 2005 public health statement. Summary of the Invention

[0006] Based on the following disclosure, the following and other implementation methods will become apparent.

[0007] This invention relates to polyurethane two-component adhesive compositions. The polyurethane two-component adhesive compositions comprise a prepolymer component and a curing agent component. Preferably, the prepolymer comprises a reaction product of at least one isocyanate compound and at least one polyol component; more preferably, the prepolymer comprises an isocyanate-terminated prepolymer. The prepolymer comprises (I) at least about 30 wt% of a polyol component, preferably no more than about 70 wt%, more preferably at least about 40 wt%, more preferably at least about 45 wt%, and even more preferably at least about 50 wt%, and the composition further comprises at least 0.05 wt% of an amine-free / tin-free catalyst (or "non-amine / tin catalyst").

[0008] Another embodiment of this article is a laminated article comprising a first substrate and a second substrate bonded together, wherein at least one of the first substrate and the second substrate comprises polycarbonate. The adhesive comprises a cured polyurethane two-component adhesive composition. Preferably, the polyurethane two-component adhesive comprises a prepolymer comprising (i) at least about 30 wt% of a polyol component, preferably at most not more than about 70 wt%, more preferably at least about 40 wt%, more preferably at least about 45 wt%, and even more preferably at least about 50 wt%, and the composition will have at least 0.05 wt% of an amine-free / tin-free catalyst. Preferably, the prepolymer comprises a reaction product of at least one isocyanate compound and at least one polyol component, more preferably, the prepolymer comprises an isocyanate-terminated prepolymer.

[0009] Further embodiments include a method for preparing a laminated article. The method includes applying a polyurethane two-component adhesive composition to at least one of a first substrate, a second substrate, and combinations thereof. The polyurethane two-component adhesive composition comprises a prepolymer component and a curing agent component. Preferably, the prepolymer comprises a reaction product of at least one isocyanate compound and at least one polyol component; more preferably, the prepolymer comprises an isocyanate-terminated prepolymer. The prepolymer comprises (i) at least about 30 wt% of a polyol component, preferably at most not more than about 70 wt%, more preferably at least about 40 wt%, more preferably at least about 45 wt%, and even more preferably at least about 50 wt%, and the composition comprises at least 0.05 wt% of an amine-free / tin-free catalyst. At least one of the first substrate, the second substrate, and combinations thereof comprises polycarbonate.

[0010] Regarding specific embodiments, for low-modulus embodiments, the Young's modulus of the adhesive may not exceed about 10 MPa, preferably not exceed about 8 MPa, more preferably not exceed about 7 MPa, more preferably not exceed about 6 MPa, and even more preferably at least about 3 MPa.

[0011] In a further embodiment of the laminated article and the method for preparing the laminated article, the coefficient of thermal expansion of the first substrate may differ from that of the second substrate by at least about 5%, preferably at least about 10%, more preferably at least about 15%, measured at a temperature in the range of about -30°C to about 82°C.

[0012] In one or more embodiments disclosed herein, the amine-free / tin-free catalyst may comprise a zirconium compound (also referred to as a "zirconium complex catalyst" or "zirconium complex"). In one particular embodiment, the zirconium compound comprises a zirconium tetra-dionato compound known as K-KAT 6212 (AKA zirconium tetra-dionato complex catalyst), which is incorporated into a reactive diluent. The catalyst package, alone or in combination with the zirconium compound, may comprise bismuth carboxylate, such as a commercially available 75% solution of tris(2-ethylhexanoic acid) bismuth dissolved in 2-ethylhexanoic acid. Another viable option is to co-mix a zinc catalyst with a bismuth catalyst to form an alternative catalyst combination to promote the isocyanate and hydroxyl reactions.

[0013] Specific embodiments of amine-free / tin-free catalysts may include zirconium compounds alone, zirconium compounds in combination with bismuth, or zirconium compounds paired with bismuth / zinc. These catalyst packages excel in modulating the isocyanate-hydroxyl reaction at room temperature, generating initial strength, and achieving excellent polycarbonate bonding performance.

[0014] The preferred NCO:OH index of the composition falls within the range of about 85-140, preferably about 90-140, more preferably about 90-130, more preferably about 90-120, more preferably about 100-120, and even more preferably from about 105 to less than about 120. Preferably, the NCO:OH index corresponds to a volume ratio of prepolymer to curing agent of about 1:1. When the index falls within these ranges, the adhesive is observed to exhibit a balanced adhesive formulation. It is believed that a lower index can lead to an increase in prepolymer viscosity. Furthermore, this can result in an overly soft adhesive, leading to reduced lap shear strength, typically below 500 psi at room temperature. Conversely, an excessively high NCO:OH index weakens bond quality, thereby impairing adhesive performance. This can manifest as an undesirable failure mode characterized primarily by suboptimal adhesion. In this case, the adhesive performance deviates from the desired properties, making it unsuitable for the intended application.

[0015] The benefits of the polyurethane two-component adhesive compositions disclosed herein include expanding the market for polycarbonate thermoplastic adhesives using minimal or no amine and tin catalysts. Furthermore, the polyurethane two-component adhesive compositions can be used with gravity-feed equipment, which can result in reduced waste, reduced downtime, and reduced equipment costs / maintenance, or one or more of these benefits. The embodiments disclosed herein demonstrate at least one benefit of excellent flexibility and curing ability at temperatures below 100°C, preferably below 75°C, more preferably below 50°C, even more preferably below 40°C, further preferably below 30°C, and even more preferably not exceeding approximately room temperature. Other benefits may include an open time of at least about 5 minutes or more. Furthermore, the embodiments disclosed herein can be formulated to provide excellent performance for polycarbonate bonding. Additionally, bonding can occur at room temperature. Conventional two-component polyurethane adhesives, reinforced with tin and tertiary amine catalysts, have failed to provide the desired bonding performance for polycarbonate under room temperature curing conditions.

[0016] This invention makes it possible to address the aforementioned needs. In particular, the compositions according to the invention unexpectedly achieve excellent adhesion with high elongation and suitable Young's modulus. Attached Figure Description

[0017] Figure 1 This is a guide for explaining the failure modes in the embodiments. Detailed Implementation

[0018] Before explaining in detail at least one embodiment of the inventive concept through exemplary figures, experiments, results, and experimental procedures, it should be understood that the application of the inventive concept is not limited to the details of construction and arrangement set forth in the following description or shown in the figures, experiments, and / or results. The inventive concept can have other embodiments or be practiced or implemented in various ways. Therefore, the language used herein is intended to be given the broadest possible scope and meaning; and the embodiments are intended to be exemplary rather than exhaustive. Furthermore, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered limiting.

[0019] Unless otherwise defined herein, scientific and technical terms relating to this disclosure shall have the meanings commonly understood by one of ordinary skill in the art. Furthermore, unless the context requires otherwise, singular terms shall include plurals, and plural terms shall include singulars. Generally, the nomenclature and techniques associated with the chemistry described herein are those well-known and commonly used in the art. Reactions and purification techniques shall be performed according to the manufacturer's instructions, or in accordance with methods commonly performed in the art, or as described herein.

[0020] All patents, published patent applications, and non-patent publications mentioned in this specification demonstrate the skill level of a person skilled in the art to which this disclosure pertains. All patents, published patent applications, and non-patent publications cited in any part of this application are expressly incorporated herein by reference in their entirety, to the extent that each individual patent or publication is specifically and individually indicated by reference.

[0021] All compositions and / or methods disclosed and claimed herein can be prepared and performed according to this disclosure without excessive experimentation. Although the compositions and methods of the invention have been described according to preferred embodiments, it will be apparent to those skilled in the art that variations may be made to the compositions and / or methods, as well as the steps or order of steps of the methods described herein, without departing from the concept, spirit, and scope of the invention. All such similar substitutions and modifications that are apparent to those skilled in the art are considered to be within the spirit, scope, and scope of the inventive concept defined by the appended claims.

[0022] As used in accordance with this disclosure, unless otherwise stated, the following terms shall be understood to have the following meanings:

[0023] When used in conjunction with the term "comprising" in the claims and / or specification, the word "a" (or "an") may mean "one," but is also consistent with the meaning of "one or more," "at least one," and "one or more than one." The term "or" as used in the claims means "and / or," unless explicitly stated to refer only to alternatives or to mutually exclusive alternatives, although this disclosure supports the definition of "and / or" referring only to alternatives. In this application, the term "about" is used to indicate that a value includes variations inherent in the equipment and methods used to determine that value, and / or variations existing between the subjects of study. The term "at least one" as used should be understood to include one or more than one, including but not limited to 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100, etc. The term "at least one / at least one" can be extended to 100 or 1000 or more, depending on the terms it connects to; furthermore, the number 100 / 1000 should not be considered limiting, as higher limits can also produce satisfactory results. Additionally, the use of the term "at least one / at least one of X, Y, and Z" should be understood to include only X, only Y, only Z, and any combination of X, Y, and Z.

[0024] The terms “comprising” (and any form of “comprising”, such as “comprise” and “comprises”), “having” (and any form of “having”, such as “have” and “has”), “including” (and any form of “including”, such as “includes” and “include”), and “containing” (and any form of “containing”, such as “contains” and “contain”) as used in this specification and claims are inclusive or open-ended and do not exclude additional, unmentioned elements or method steps.

[0025] As used herein, the term "or combinations thereof" refers to all permutations and combinations of the items listed preceding the term. For example, "A, B, C, or combinations thereof" is intended to include at least one of the following: A, B, C, AB, AC, BC, or ABC, and also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB if the order is important in the particular context. Continuing this example, explicitly included are combinations containing one or more repeated items or terms, such as BB, AAA, MB, BBC, AAABCCCC, CBBAAA, CABABB, etc. Those skilled in the art will understand that there is generally no limit to the number of items or terms in any combination unless the context otherwise requires.

[0026] The term "monomer" refers to a small molecule that is chemically bonded to one or more monomers of the same or different kinds during polymerization to form a polymer.

[0027] The term "polymer" refers to a macromolecule containing one or more types of monomeric residues (repeating units) linked by covalent chemical bonds. According to this definition, a polymer encompasses compounds in which the number of monomeric units can vary from very few to very many.

[0028] In the adhesives industry, open time is the amount of time that materials must be bonded together before the adhesive begins to cure.

[0029] Unless otherwise stated, the wt% of compositions, adhesive compositions, etc. mentioned herein are intended to include both prepolymers and curing agents.

[0030] Unless otherwise stated, the standards mentioned throughout this application are those in effect as of the date of filing of this application. Examples of methods that can be used to determine characteristics are listed below. However, these methods are equally applicable, and unless otherwise stated in the claims, the claims are not limited to the following methods.

[0031] (1) Methods that can be used to determine number-average molecular weight include, but are not limited to, gel permeation chromatography (GPC), gas phase permeation, membrane permeation and vapor pressure reduction.

[0032] (2) NCO% (AKA %NCO): One technique for determining NCO% is ASTM D5155. However, determining NCO% is not limited to the above technique.

[0033] (3) The NCO index (AKA NCO:OH index or NCO to OH index) is the equivalent ratio of isocyanate to hydroxyl-containing polyol (calculated as the ratio of the number of isocyanate (NCO) groups to the number of hydroxyl (OH) groups present in the reaction mixture, essentially dividing the equivalent of NCO by the equivalent of OH). The NCO index can be measured when the volume ratio of prepolymer to curing agent is typically about 1:1.

[0034] (4) Viscosity: Viscosity can be measured using a TA Instruments Discovery HR-1 rheometer with a cone plate. Unless otherwise specified, the cone plate has a diameter of 40 mm. Unless otherwise specified, the temperature is 23°C and the shear rate is 0.79 s⁻¹.

[0035] (5) Tensile strength of the adhesive: Tensile strength can be determined according to ASTM D-638. The embodiments disclosed herein are not limited to determining tensile strength according to the above ASTM standard.

[0036] (6) CTE: One test method that can be used to determine the coefficient of thermal expansion (“CTE”) is ASTM Test Method E831. The implementation methods disclosed herein are not limited to determining CTE by the above-mentioned ASTM standard.

[0037] (7) Hydroxyl group number: The OH number can be determined according to ASTM D4274, Test Method for Polyurethane Raw Materials: Determination of Hydroxyl Group Number in Polyols. The determination of the OH number is not limited to the above ASTM standard. Various titration methods are also applicable.

[0038] (8) Young's modulus: While any suitable method or device can be used to determine the Young's modulus discussed herein, one example of a device that can be used to measure modulus is the LMEC-1 Young's modulus meter.

[0039] (9) Overlap shear adhesion: One test method that can be used to determine overlap shear adhesion is ASTM D5868. Other methods may also be used.

[0040] (10) Elongation %: Elongation % can also be determined according to ASTM D-638. The embodiments disclosed herein are not limited to determining tensile strength according to the above ASTM standard.

[0041] "Approximately X" means that the value of X fluctuates by 10%.

[0042] In the context of this invention, the range of values ​​is understood to be inclusive. For example, the range "between 0% and 25%" specifically includes the values ​​0% and 25%.

[0043] The first embodiment disclosed herein includes a two-component (“2K” or “2-component”) adhesive composition. Preferably, the adhesive is a polyurethane adhesive. One application of the adhesive is as a structural adhesive. The adhesive may contain a prepolymer (or “prepolymer component”), preferably a polyol component, and more preferably an NCO content. The prepolymer may contain a reaction product of an isocyanate compound and a polyol component. More preferably, the prepolymer contains an isocyanate-terminated prepolymer. The prepolymer may be referred to as the first component or part A of the 2K adhesive. The second component or part B may be referred to as the curing agent component (or “curing agent”).

[0044] Isocyanates containing two or more isocyanate groups are used in this disclosure as stoichiometric isocyanates, excess isocyanates, and free isocyanates. The isocyanate can be a monomeric or polymeric isocyanate, including aromatic and alicyclic polyisocyanates, more preferably aromatic monomeric isocyanates or aromatic polymeric isocyanates.

[0045] Polyisocyanates can be diisocyanates comprising alicyclic, aromatic, and aliphatic-aromatic diisocyanates. Specific examples of alicyclic diisocyanates include, but are not limited to, cyclopentene-1,3-diisocyanate, cyclohexene-1,4-diisocyanate, cyclohexene-1,2-diisocyanate, 1-isocyano-2-isocyanomethylcyclopentane, 1-isocyano-3-isocyanomethyl-3,5,5-trimethylcyclohexane (isophorone diisocyanate or IPDI), bis-(4-isocyanocyclohexyl)methane, 2,4-... α′-Dicyclohexylmethane diisocyanate, 1,3- or 1,4-bis-(isocyanomethyl)-cyclohexane, bis-(4-isocyano-3-methylcyclohexyl)-methane, α′,α′,α′,α′-tetramethyl-1,3- and / or-1,4-phenylenedimethylene diisocyanate, 1-isocyano-1-methyl-4(3)-isocyanomethylcyclohexane, 2,4- or 2,6-hexahydrotoluene diisocyanate, etc.

[0046] Specific examples of aromatic and aliphatic-aromatic diisocyanates may include, but are not limited to, 2,4- or 2,6-toluene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4′-diisocyanate, phenylenediamine diisocyanate, 1,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, terephthalene diisocyanate, diphenyl-4,4′-diisocyanate, azobenzene-4,4′-diisocyanate, and diphenyl sulfone-4, 4′-diisocyanate, 2,4-toluene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, 4,4′,4″-triisocyanotriphenylmethane, 1,3,5-triisocyanobenzene, 2,4,6-triisocyanotoluene, 4,4′-dimethyldiphenylmethane-2,2′,5,5-tetraisocyanate, and modified aromatic diisocyanates containing carbodiimide groups, carbamate groups, urethane groups, isocyanurate groups, urea groups, or biuret groups.

[0047] Modified aromatic diisocyanates can be urea-imide-modified isocyanates derived from 2,4- or 2,6-toluene diisocyanates; or derived from 4,4′- or 2,4′-diphenylmethane diisocyanates, such as urea-imide-modified 4,4′-diphenylmethane diisocyanates. Suitable urea-imide-modified isocyanates may include commercially available Rubinate® 1680 from Huntsman Corporation; and commercially available ISONATE™ 143L modified MDI from Dow Chemicals Company.

[0048] Another example of modified MDI (modified diphenylmethane diisocyanate) is a diphenylmethane diisocyanate in which at least about 2% of the isocyanate groups have been modified to carbodiimide, or urea carbamate, or biuret, or a polymeric structure.

[0049] In further examples, modified MDI may include a mixture of MDI isomers, some of which have been modified to carbodiimide, or urethane, or biuret, or polymeric structures, while others remain unmodified and thus remain monomers such as 4,4'-MDI, 2,4'-MDI, 2,2'-MDI, or combinations thereof.

[0050] In one non-limiting embodiment, the isocyanate may be hexamethylene diisocyanate, toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), hydrogenated MDI (HMDI), or polymeric MDI (functionality greater than 2).

[0051] Optionally, if desired, the polyurethane composition may be free of aromatic isocyanate compounds. For example, the polyurethane composition may be free of aromatic isocyanate compounds selected from the group consisting of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate, diisocyanobenzene, triisocyanobenzene, triisocyanotoluene, bis(isocyanomethyl)benzene, and combinations thereof.

[0052] The preferred functionality of the polymer and / or monomeric isocyanate is at least about 2 to no more than 3, preferably less than 2.8. Specific preferred examples of functionality may include at least about 2.1, at most about 2.7, at least about 2.15, at least about 2.2, at least about 2.25, at least about 2.3, and at least about 2.35. Alternatively, the functionality may be about 2.0 to about 2.1, about 2.1 to about 2.2, about 2.2 to about 2.3, about 2.3 to about 2.4, about 2.4 to about 2.5, about 2.5 to about 2.6, about 2.6 to about 2.7, about 2.7 to about 2.8, about 2.8 to about 2.9, about 2.9 to about 3.0, and combinations thereof.

[0053] The polyol component of the prepolymer can be any polyol suitable for the preparation of polyurethane. These can be polyols based on polyalkylene oxides, polyesters, or combinations thereof, which may contain large side chains and / or long hydrophobic chains. Polyalkylene oxide-based polyols are commonly referred to as polyether polyols. Polyols may also include polyamide polyols, polycaprolactone polyols such as poly-ε-caprolactone polyols, polycarbonate polyols, hydroxyl-terminated polybutadienes such as fully hydrogenated hydroxyl-terminated polybutadiene and / or partially hydrogenated hydroxyl-terminated polybutadiene, polyisobutylene glycol, and mixtures thereof.

[0054] Non-limiting examples of suitable polyols include polyether polyols and polyester polyols. Exemplary polyether polyols may include linear and / or branched polyethers having hydroxyl groups. Examples of polyether polyols may include substituted and / or unsubstituted polyoxyalkylene polyols, such as polyethylene glycol, polypropylene glycol, polybutane glycol, etc. Furthermore, homopolymers and copolymers of polyoxyalkylene polyols may also be employed. In particular, copolymers of polyoxyalkylene polyols may include adducts having at least one compound selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, 2-ethylhexanediol-1,3-glycerol, 1,2,6-hexanetriol, trimethylolpropane, trimethylolethane, tri(hydroxyphenyl)propane, triethanolamine, triisopropanolamine, ethylenediamine, and ethanolamine; and at least one compound selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide.

[0055] Polyether polyols may include polymers of propylene oxide and / or copolymers of ethylene oxide and propylene oxide, wherein oxides are included. In one non-limiting embodiment, the polyether polyol is an ethylene oxide-terminated polypropylene oxide.

[0056] The number-average molecular weight of polyether polyols typically varies from about 2,000 Daltons to about 20,000 Daltons, or from about 3,500 Daltons to about 12,000 Daltons, or from about 2,000 Daltons to about 12,000 Daltons. For example, Acclaim® 4220N polyol (commercially available from Covestro) is based on propylene oxide and capped with ethylene oxide, with a number-average molecular weight of 4,000 Daltons. Other suitable Acclaim® polyols include Acclaim® 6320N and Acclaim® 8200. Another example is PPG 4000. Examples of polyols with a number-average molecular weight exceeding 12,000 Daltons include Acclaim® 12200 and Hyperlite® E-855. Alternatively, the number average molecular weight may be in the range of about 2,000 to about 4,000, about 4,000 to about 6,000, about 6,000 to about 8,000, about 8,000 to about 10,000, about 10,000 to about 12,000, about 12,000 to about 14,000, about 14,000 to about 16,000, about 16,000 to about 18,000, about 18,000 to about 20,000 and combinations thereof.

[0057] The polyether polyols used in this disclosure may include one or more 2-functional polyether polyols, one or more 3-functional polyether polyols, one or more 4-functional polyether polyols, or combinations thereof. The number-average molecular weight of the 2-functional polyether polyols may vary in the range of about 2,000 to about 20,000 Daltons, or in the range of about 2,000 to 12,000 Daltons. For example, Pluracol® P2010 is a polyether polyol with a number-average molecular weight of 2,000 Daltons, commercially available from BASF. PPG 2000 from PPG is another example of a suitable polyol. The molecular weight of the 3-functional polyether polyols may vary in the range of about 84 to about 20,000 Daltons, or in the range of about 100 to 12,000 Daltons, including Pluracol® TP-440 polyol commercially available from BASF. The molecular weight of 4-functional polyether polyols can vary from about 100 to about 20,000 Daltons or range from about 400 to 12,000 Daltons. For example, Pluracol® 355 is a polyether polyol with a number-average molecular weight of 600 Daltons, commercially available from BASF. In some embodiments, the molecular weight of the polyether polyol will be at least 4,000 Daltons. In an alternative example, the molecular weight of the polyether polyol will not exceed about 4,000 Daltons, preferably less than about 3,000 Daltons.

[0058] Exemplary polyester polyols may include amorphous and liquid polyester polyols, fatty acid polyester polyols, such as castor oil and vegetable oils with different molecular weights and functionalities.

[0059] Polyester polyols can be formed as reaction products of one or more carboxylic acids and one or more polyols such as diols and / or triols. Carboxylic acids that can be used to form polyester polyols may include, but are not limited to, adipic acid, glutaric acid, succinic acid, malonic acid, oxalic acid, and mixtures thereof. Diols that can be used to form polyester polyols may include, but are not limited to, ethylene glycol, propylene glycol, butanediol, neopentyl glycol, pentylene glycol, and hexanediol, and mixtures thereof. Triols considered suitable for forming polyester polyols may include trimethylolpropane.

[0060] Examples of fatty acid polyester polyols may include castor oil, hydroxylated products of unsaturated or polyunsaturated natural oils, hydrogenated products of unsaturated or polyunsaturated polyhydroxy natural oils, polyhydroxy esters of alkyl hydroxy fatty acids, polymerized natural oils, soybean polyols, alkyl hydroxylated amides of fatty acids, and cashew nut shell liquid.

[0061] In one non-limiting embodiment, the polyester polyol can be obtained by reacting a triol with azelaic acid. The triol can be glycerol. An example of such a polyester polyol is Emerox® 14001, which is derived from natural oils and is commercially available from Emery Oleochemicals.

[0062] The number average molecular weight of polyester polyols typically varies in the range of about 1,000 to about 20,000 Daltons, or in the range of about 1,300 to 10,000 Daltons. Admex™ 525 polyol (commercially available from Eastman Chemical Company) is a polyester polyol with a molecular weight of 1,400 and is available for use.

[0063] In one embodiment, the viscosity of the prepolymer may not exceed about 400,000 cP, preferably not exceed about 200,000 cP, more preferably not exceed about 100,000 cP, and even more preferably not exceed about 50,000 cP, measured at 23°C and a shear rate of about 0.79 s⁻¹. Alternatively, the viscosity of the prepolymer may include not more than about 400,000 cP to about 300,000 cP, about 300,000 cP to about 200,000 cP, about 200,000 cP to about 100,000 cP, about 100,000 cP to about 50,000 cP, about 50,000 cP to about 10,000 cP, or combinations thereof, measured at 23°C and a shear rate of about 0.79 s⁻¹.

[0064] Preferably, the NCO% in the prepolymer comprises up to about 30%, more preferably about 1% to 25%, such as about 1% to 20%, even more preferably less than about 20%, and further preferably at least about 3% or up to about 20%. In specific examples, a preferred range of NCO% is about 4-10%, another preferred embodiment is greater than about 4% to less than 19%, and in yet another embodiment, a preferred range is about 4-20%. Alternatively, the NCO% range can be greater than about 1% to about 5%, about 5% to about 10%, about 10% to about 15%, about 15% to about 20%, about 20% to about 25%, about 25% to about 30%, and combinations thereof.

[0065] The second component (“curing agent”) of the adhesive composition may include a second polyol component (or “second polyol”), or two or more second polyols (a plurality of second polyols). Preferably, the second polyol has a number average molecular weight of at least about 2,000 Daltons, more preferably at least about 4,000 Daltons, further preferably at least about 6,000 Daltons, even more preferably at least about 8,000 Daltons, even further preferably at least about 12,000 Daltons, and most preferably greater than about 100,000 Daltons. Exemplary polyols include the aforementioned PPG 4000, Acclaim® 6320 N, Acclaim® 8200, Acclaim® 12200 Pluracol TP-440, and Hyperlite® E-855.

[0066] In one particular embodiment, the number-average molecular weight of the second polyol in the second component does not exceed about 18,000 Daltons. Specific embodiments of the number-average molecular weight of the second polyol may be up to about 15,000 Daltons, up to about 13,000 Daltons, or up to about 12,000 Daltons. Alternatively, the number-average molecular weight may be about 18,000 to about 16,000, about 16,000 to about 14,000, about 14,000 to about 12,000, about 12,000 to about 10,000, about 10,000 to about 8,000, about 8,000 to about 6,000, about 6,000 to about 4,000, about 4,000 to about 2,000, and combinations thereof.

[0067] In another specific embodiment, the second polyol of the second component may have a number average molecular weight of at least about 5,000 Daltons, preferably at least about 10,000 Daltons, more preferably at least about 15,000 Daltons, even more preferably at least about 20,000 Daltons, further preferably at least about 50,000 Daltons, and most preferably greater than about 80,000 Daltons.

[0068] Examples of suitable components for the second polyol component may include polymer-modified polyols, preferably modified polyether polyols. In a preferred embodiment, the concentration of the polymer-modified polyol accounts for up to about 70 wt% of the second component.

[0069] In one specific embodiment, the second polyol comprises at least one polymer or prepolymer containing one or more polyether polyols having one or more organic polymer particles dispersed therein or grafted onto a backbone containing one or more organic polymer particles dispersed therein. One or more organic polymer particles may be based on monovinyl aromatic monomers and copolymers of monovinyl aromatic monomers with conjugated dienes, acrylates, methacrylates, unsaturated nitrites, or mixtures thereof. The copolymer may be a block or random copolymer. In a non-limiting embodiment of this disclosure, one or more organic polymer particles contain unsaturated... nitrile (nitrites), copolymers of conjugated dienes and monovinylene aromatic monomers, copolymers of unsaturated nitrile and monovinylene aromatic monomers, or polyurea. In another non-limiting embodiment of this disclosure, the particles comprise a polystyrene-acrylonitrile copolymer, which is most preferred. Preferably, the organic polymer particles are included in a prepolymer comprising a polyol, preferably a triol, in which the organic polymer particles are dispersed, such as one or more thermoplastic polymers, rubber-modified thermoplastic polymers, or polyureas dispersed in one or more triols. Preferably, the polyol dispersed or grafted with organic polymer particles is disclosed in U.S. Patent No. 6,709,539 to Zhou (column 4, lines 13 to 6, lines 18), which is incorporated herein by reference. Preferably, the polyol used to disperse the organic particles is one or more polyether triols described herein. Preferably, the compositions of the present invention contain a prepolymer containing one or more organic polymer particles in an amount sufficient to improve the elasticity and modulus of the composition. In this specific embodiment, it is also preferred that the number average molecular weight of the second polyol is at least about 15,000 Daltons, more preferably at least about 20,000 Daltons, even more preferably at least about 50,000 Daltons, and most preferably more than about 80,000 Daltons.

[0070] Preferably, the second polyol component is a multifunctional polyol, such as a diol or a triol.

[0071] The second component may contain at least about 10 wt% and at most about 75 wt% of the second polyol or multiple second polyols, preferably less than about 70 wt%, more preferably less than about 65%, even more preferably greater than about 15 wt%, even more preferably at least about 20 wt%, even more preferably at least about 25 wt%, and most preferably at least about 30 wt%; or the second component may contain at least one of the following: about 10 wt% to about 20 wt%, about 20 wt% to about 30 wt%, about 30 wt% to about 40 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 60 wt%, about 60 wt% to about 70 wt%, about 70 wt% to about 75 wt%, or combinations thereof.

[0072] The second component may also comprise a monofunctional alcohol. The monofunctional alcohol preferably comprises a terminal hydroxyl group and a hydrocarbon chain. The hydrocarbon chain may comprise one or more polyether groups. In one particular embodiment, the monofunctional alcohol comprises a terminal hydrocarbon having fewer than 9 carbon atoms, preferably fewer than 8 carbon atoms, and a hydroxyl terminus. More preferably, the main chain of the monofunctional alcohol comprises more than one alkoxyl unit, preferably at least two such units. Suitable examples of alkoxylation can range from at least 3 to about 30 and all numbers therein. Non-limiting examples of suitable alkoxylations include ethylene oxide (EO), propylene oxide (PO), and butane oxide (BO), and combinations thereof.

[0073] The second component may contain up to about 20 wt% of monofunctional alcohol, preferably less than about 15 wt%, more preferably not more than about 10 wt%, even more preferably not more than about 5 wt%, further preferably at least about 1 wt%, even more preferably at least about 3 wt%; or the amount of monofunctional alcohol in the second component may contain at least one of the following combinations: about 1 wt% to about 5 wt%, about 5 wt% to about 10 wt%, about 10 wt% to about 15 wt%, about 15 wt% to about 20 wt%.

[0074] Alternatively, the second component may also include one or more other polyols. These other polyols may be the same as or different from those previously described with respect to the prepolymer. The other polyols may be polyether polyols. In one non-limiting embodiment, the polyether polyol is a polymer of propylene oxide or a copolymer of ethylene and propylene oxide. In another non-limiting embodiment, the free polyol may be cashew phenol-based polyester polyol or poly-ε-caprolactone polyol.

[0075] Optionally, the second polyol may include an aspartic resin or a diamine incorporated into its main chain.

[0076] The adhesive composition may also include a silane tackifier selected from the group consisting of isocyanurate silane tackifiers, isocyanate silane tackifiers, epoxy-functionalized silane tackifiers, and combinations thereof. The concentration of the silane tackifier may range from about 0.1 to 10 wt%. Non-limiting examples of isocyanurate silanes include, but are not limited to, 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. Other examples include (isocyanomethyl)methyldimethoxysilane, 3-isocyanopropyltrimethoxysilane, 3-isocyanopropyltriethoxysilane, 3-isocyanopropylmethyldimethoxysilane, 3-isocyanopropylmethyldiethoxysilane, tris[3-(trimethoxysilyl)propyl]isocyanurate, tris[3-(triethoxysilyl)propyl]isocyanurate, isocyanomethyltrimethoxysilane, and isocyanomethyltriethoxysilane. The aforementioned isocyanurate compounds can be used in any combination thereof.

[0077] Non-limiting examples of suitable epoxy-functionalized silane tackifiers include: 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-(2,3-epoxypropoxypropyl)methyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and combinations thereof.

[0078] The composition may further comprise at least 0.05 wt% of an amine-free / tin-free catalyst, preferably present in at least one of the prepolymer, curing agent, and combinations thereof, more preferably present in at least the prepolymer. In specific embodiments, the wt% of the amine-free / tin-free catalyst may comprise at least about 0.075 wt%, preferably at least about 0.1 wt%, more preferably at least about 0.25 wt%, and even more preferably at least about 0.3 wt%. Alternatively, the wt% of the amine-free / tin-free catalyst may comprise at least about 0.05 wt% to about 0.1 wt%, about 0.1 wt% to about 0.15 wt%, about 0.15 wt% to about 0.2 wt%, about 0.2 wt% to about 0.25 wt%, about 0.25 wt% to about 0.3 wt%, about 0.3 wt% to about 0.35 wt%, about 0.35 wt% to about 0.4 wt%, or combinations thereof.

[0079] An example of an amine-free / tin-free catalyst may comprise a zirconium compound, such as a zirconium chelate catalyst. In other embodiments, the amine-free / tin-free catalyst comprises at least one of the following: a zirconium chelate catalyst, a bismuth catalyst, a zinc catalyst, or a combination thereof. Specific examples of amine-free / tin-free catalysts include at least one of the following: zinc neodecanoate, zinc octanoate, zinc acetylacetonate, zinc oxalate, zinc acetate, bismuth carboxylate, bismuth oxide, bismuth tris(2-ethylhexanoate), bismuth trioctanoate (e.g., Bi-OC, 20% metal content), bismuth neodecanoate, bismuth octanoate, bismuth acetylacetonate, bismuth oxalate, bismuth acetate, or a combination thereof.

[0080] In one embodiment, the amine-free / tin-free catalyst of the two-component polyurethane composition comprises at least one of a zirconium compound, a zinc compound, a bismuth compound (also referred to as a "bismuth complex"), and combinations thereof. Preferably, if present, the zirconium compound is present in an amount not exceeding about 1.2 wt%, preferably not exceeding about 0.9 wt%, more preferably not exceeding about 0.7 wt%, more preferably not exceeding about 0.6 wt%, even more preferably at least about 0.1 wt%, and most preferably greater than about 0.15 wt%. Similarly, preferably, if present, the zinc compound is present in an amount not exceeding about 0.3 wt%, more preferably not exceeding about 0.1 wt%, more preferably not exceeding about 0.07 wt%, even more preferably not exceeding about 0.05 wt%, even more preferably at least about 0.01 wt%, and most preferably greater than about 0.015 wt%. Furthermore, if present, the bismuth compound is preferably present in an amount not exceeding about 0.3 wt%, more preferably not exceeding about 0.1%, even more preferably not exceeding about 0.05 wt%, even more preferably not exceeding about 0.03 wt%, even more preferably at least about 0.01 wt%, and most preferably greater than about 0.015 wt%.

[0081] Optional components of the binder composition may include one or more catalysts, preferably tin catalysts (or "tin-containing catalysts"), in an amount of less than about 0.7 wt%, such as not more than about 0.6 wt%, not more than about 0.5 wt%, not more than about 0.4 wt%, less than about 0.3 wt%, or less than about 0.2 wt%, preferably not more than about 0.1 wt%, more preferably not more than about 0.05 wt%, even more preferably not more than about 0.01 wt%, more preferably not more than trace amounts of tin catalyst, even more preferably less than trace amounts of tin catalyst, and most preferably tin-free catalyst. Alternatively, the tin catalyst may be less than about 0.7 wt% to about 0.6 wt%, about 0.6 wt% to about 0.5 wt%, about 0.5 wt% to about 0.4 wt%, about 0.4 wt% to about 0.3 wt%, about 0.3 wt% to less than about 0.2 wt%, less than about 0.2 wt% to about 0.15 wt%, about 0.15 wt% to about 0.10 wt%, about 0.1 wt% to about 0.05 wt%, about 0.5 wt% to less than 0.1 wt%, or combinations thereof. Examples of optional tin catalysts may include dibutyltin compounds, mercaptotin compounds, and combinations thereof. Regarding the amount of tin, in a preferred embodiment, the binder composition contains no more than about 0.31 wt% tin, preferably no more than about 0.25 wt%, more preferably no more than about 0.2 wt%, and even more preferably no more than about 0.1 wt%.

[0082] Further regarding the 2K polyurethane adhesive composition, optionally, the composition contains no more than about 0.1 wt% or less than about 0.1 wt%, preferably no more than about 0.09 wt% of a tertiary amine catalyst, preferably no more than about 0.05 wt% or less than 0.05 wt%, more preferably no more than about 0.01 wt%, more preferably no more than trace amounts of the tertiary amine catalyst, even more preferably less than trace amounts of the tertiary amine catalyst, and most preferably no tertiary amine catalyst. Examples of tertiary amines include blocked tertiary amines, preferably comprising at least one of the following: a solution of 1,4-diazabicyclo[2.2.2]octane, DBU (diazabicycloundecene), 1,4-diazabicyclooctane, and combinations thereof.

[0083] Another optional aspect is that the adhesive composition may contain less than about 1 wt% of solvent and / or water, preferably not exceeding the nominal amount of solvent and water.

[0084] The adhesive composition may further comprise a further component selected from at least one of the following: polyether diamine, monoether, and combinations thereof. The concentration of the further component may not exceed about 20 wt%, preferably at least about 0.5 wt%.

[0085] Non-limiting examples of polyetheramines include diamines or triamines based on polyoxyalkylene polyamines, such as Jeffamines or Baxxodur polyetheramines.

[0086] Non-limiting examples of monoethers include: poly(ethylene glycol-ran-propylene glycol) monobutyl ether, poly(propylene glycol) monobutyl ether, poly(ethylene-co-1,2-butene) monool, polyester ether monool, C12 to C18 alcohols, and combinations thereof.

[0087] The adhesive compositions disclosed herein may contain less than about 10 wt% of a plasticizer, preferably less than about 5 wt%, more preferably less than about 4 wt%, even more preferably less than about 2 wt%, and most preferably less than about 1 wt%. Specific embodiments may contain less than about 0.5 wt%, less than about 0.1 wt%, or below the detection limit of the plasticizer. Alternatively, the wt% of the plasticizer may be less than about 10 wt% to about 8 wt%, about 8 wt% to about 6 wt%, about 6 wt% to about 4 wt%, about 4 wt% to about 2 wt%, about 2 wt% to less than about 0.5 wt%, or combinations thereof.

[0088] Another component of the adhesive composition may include a chain extender comprising a polyol or aromatic diamine having at least two functionalities. Suitable chain extenders include diols and triols. In one embodiment, the chain extender may be a low molecular weight chain extender compound and may be hydroxyl-terminated or amine-terminated. In a non-limiting embodiment of this disclosure, the chain extender compound may be hydroxyl-terminated, comprising a low molecular weight polyol with a molecular weight range of about 25 to about 1,000 Daltons, or about 32 to about 600 Daltons. The non-carbamate-modified low molecular weight chain extender compound may be selected from the group consisting of ethylene glycol, diethylene glycol, 1,5-pentanediol, 1,3-pentanediol, 1,3-butanediol, 1,4-butanediol, 1,2-propanediol, 1,3-propanediol, 1,6-hexanediol, dipropylene glycol, neopentanediol, 3-methylpentanediol, 1,4-cyclohexanediol, and combinations thereof. In one non-limiting embodiment, the non-carbamate-modified low molecular weight chain extender may include 1,4-butanediol, ethylene glycol, 1,2-propanediol, dipropylene glycol, and combinations thereof. Examples of suitable aromatic diamine compounds may include diethyltoluenediamine, tetrapropoxylated ethylenediamine, methylenebis(o-ethylaniline), and combinations thereof.

[0089] The adhesive composition may also include various types of fillers, rheology modifiers, colorants, and additives as needed. Several typical examples of fillers for polyurethane adhesives include talc, precipitated calcium carbonate, and combinations thereof. Some embodiments of the adhesive composition may contain less than about 1 wt% precipitated calcium carbonate, preferably less than about 0.5 wt%, more preferably less than about 0.1 wt%, and even more preferably no precipitated calcium carbonate.

[0090] In one embodiment, the two-component polyurethane composition may include fumed silica in the prepolymer. The amount of fumed silica in the prepolymer may be less than about 50 wt%, preferably less than about 30 wt%, more preferably less than about 15 wt%, more preferably less than about 10 wt%, and most preferably less than about 5 wt%. If desired, the prepolymer may contain less than about 1 wt% fumed silica. Optionally, the prepolymer may have at least about 0.1 wt% fumed silica.

[0091] Regarding the 2K polyurethane adhesive disclosed herein, the second polyol component may constitute part of the curing agent (“Part B”). The volume ratio of the curing agent to the prepolymer may include from about 1:10 to about 10:1, and preferred volume ratios may include about 1:1, at least about 1:1.5, at least about 1:4, and at least about 1:2.

[0092] Typical components of the prepolymer in Part A may include one or more of the aforementioned polyols, one or more isocyanate compounds, one or more amine-free / tin-free catalysts, one or more of the aforementioned fillers, and other optional components. Typical components of the curing agent in Part B may include one or more of the aforementioned polyols, optional chain extenders, one or more optional fillers, monoamines or diamines, and optionally one or more amine-free / tin-free catalysts.

[0093] Preferably, the tensile strength of the adhesive includes at least about 3 MPa (about 435 psi), more preferably at most at least about 5 MPa (about 725 psi), more preferably at least about 6 MPa (about 870 psi), and even more preferably not exceeding about 7 MPa (at least about 1000 psi), and the NCO:OH index of the composition is about 85 to 140, preferably at least about 90 (such as about 90 to 140), more preferably at least about 100, more preferably at least about 110, more preferably not exceeding about 125, and even more preferably not exceeding about 120. Preferably, the NCO:OH index is measured when the volume ratio of prepolymer to curing agent is about 1:1.

[0094] Preferably, the adhesive composition has a Young's modulus for the low modulus implementation, and the adhesive composition may have a Young's modulus of at most about 10 MPa, preferably not more than about 8 MPa, more preferably not more than about 7 MPa, further preferably at least about 1 MPa, and even more preferably at least about 3 MPa.

[0095] Furthermore, the cured polyurethane adhesive composition may have an elongation of at least about 100%, preferably at least about 200%, and more preferably at least about 300%. In a specific embodiment having one of the above elongation percentages, the cured composition may have a tensile strength of at least about 3 MPa, preferably at least about 7 MPa, and even more preferably up to about 8 MPa.

[0096] The disclosed adhesive may be part of a laminated article. Preferably, the laminated article comprises a first substrate and a second substrate. Preferably, any of the adhesives disclosed herein is sandwiched between the first substrate and the second substrate. In one embodiment, the coefficient of thermal expansion (“CTE”) of the first substrate differs from that of the second substrate by at least about 5%, preferably at least about 10%, more preferably at least about 15%, measured at a temperature ranging from about -30°C to at most about 82°C.

[0097] In one embodiment, the laminated article is formed without using an adequate amount of primer to help the adhesive adhere to one or two substrates. More preferably, no primer is used.

[0098] In another embodiment, a primer can be used. In such an embodiment, the primer can be applied to one or both substrates. Typically, the primer is applied to the substrate adjacent to the adhesive composition.

[0099] The laminated articles disclosed herein are not limited to any particular substrate. In one particular embodiment, the two substrates have different CTEs as described above. Preferably, one of the substrates comprises a polycarbonate material. Non-limiting examples of substrates include glass, glass fiber composites, rubber, textiles, metals, coated metals, thermoplastics, and composites. Preferably, the composites may comprise carbon fiber or sheeting molding compounds. Preferably, the metals may comprise at least one of aluminum, copper steel, stainless steel, galvanized steel, carbon steel, and alloys thereof. Preferably, the coating of the coated metal may comprise nickel. Examples of thermoplastics may include at least one of polyamides, polyolefins, and combinations thereof. Examples of polyolefins and other materials suitable for the substrate may include polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polypropylene (“PP”), polyethylene (“PE”), high-density polyethylene (“HDPE”), polystyrene, polyvinyl chloride (“PVC”), acrylonitrile butadiene styrene (“ABS”), and combinations thereof. The various substrates listed herein can be used in any combination. Furthermore, one or more substrates may be powder-coated or electro-coated.

[0100] This disclosure also includes methods for preparing the laminated articles described herein. The methods include applying any of the adhesives disclosed herein to either a first substrate or a second substrate. The methods also include bonding the first substrate to the second substrate. The foregoing disclosures regarding CTE also apply to methods for preparing laminated articles.

[0101] Optionally, the method may exclude applying the primer to either the first or second substrate, and preferably not to both the first and second substrates. Furthermore, the method may exclude the step of mechanically pretreating either the first or second substrate prior to applying the adhesive, and preferably not mechanically pretreating either the first or second substrate.

[0102] This document also discloses a method for preparing a laminated article. The method includes applying any of the aforementioned adhesive compositions to a first substrate, a second substrate, or both. The adhesive composition is sandwiched between the first substrate and the second substrate. The adhesive is cured at a temperature not exceeding about 50°C, preferably not exceeding about 40°C, more preferably not exceeding about 35°C, more preferably not exceeding about 30°C, even more preferably not exceeding about 25°C, and most preferably at least about 15°C.

[0103] The method of preparing the laminated article may optionally include applying a primer to one of the first substrate or the second substrate, preferably not applying the primer to the first substrate or the second substrate to which the adhesive composition is applied. Preferably, the primer is positioned where it contacts the adhesive composition applied to the other substrate when the adhesive is sandwiched in.

[0104] As described in the alternative, the primer is applied to a location on one of the substrates (first substrate or second substrate) that aligns with the adhesive that has been applied to or will be applied to the other substrate. The order in which the adhesive is applied before or after the primer is irrelevant.

[0105] In another alternative embodiment of the method, a primer is applied to a predetermined location on one of the first and second substrates. An adhesive is then applied to the predetermined location, and the substrates are then bonded together. In yet another alternative embodiment, the primer is applied to locations on both the first and second substrates designed to contact the adhesive. The adhesive is applied to at least one of the first and second substrates at the desired location where the primer has been applied. A laminated article is then formed, wherein the substrate having the adhesive is in contact with a substrate containing the primer but without the adhesive. Preferably, the portion of the substrate previously primed is in contact with the adhesive.

[0106] The adhesive may have a Young's modulus of at least about 1 MPa and at most about 10 MPa. Regarding specific embodiments of the adhesive composition, for low-modulus embodiments, the adhesive may have a Young's modulus of at least about 1 MPa and at most about 7 MPa, preferably not exceeding about 6 MPa.

[0107] The foregoing disclosures regarding laminated articles and methods for preparing laminated articles also apply to alternative adhesive compositions.

[0108] The following terms 1 to 31 are preferred:

[0109] 1. A two-component polyurethane adhesive composition comprising a prepolymer component and a curing agent component, preferably, the prepolymer comprising a reaction product of at least one isocyanate compound and at least one polyol component, more preferably, the prepolymer comprising an isocyanate-terminated prepolymer, wherein the prepolymer comprises:

[0110] a. At least about 30 wt% of a polyol component, preferably no more than about 70 wt%, more preferably at least about 40 wt%, more preferably at least about 45 wt%, and even more preferably at least about 50 wt%; or the amount of said polyol component comprises at least about 30 wt% to about 40 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 60 wt%, about 60 wt% to about 70 wt%, or a combination thereof; and

[0111] b. The composition comprises at least 0.05 wt% of an amine-free / tin-free catalyst, preferably at least about 0.075 wt%, more preferably at least about 0.1 wt%, further preferably at least about 0.25 wt%, and at least about 0.3 wt%; or the composition may comprise an amine-free / tin-free catalyst in amounts of at least about 0.05 wt% to about 0.1 wt%, about 0.1 wt% to about 0.15 wt%, about 0.15 wt% to about 0.2 wt%, about 0.2 wt% to about 0.25 wt%, about 0.25 wt% to about 0.3 wt%, greater than about 0.3 wt%, or combinations thereof, preferably in at least one of the prepolymer, the curing agent, and combinations thereof, more preferably in at least the prepolymer.

[0112] Preferably, the adhesive composition contains less than about 1 wt% precipitated calcium carbonate, more preferably less than about 0.5 wt%, more preferably less than about 0.1 wt%, and even more preferably no precipitated calcium carbonate.

[0113] 2. The two-component polyurethane adhesive composition according to Clause 1, wherein the composition comprises less than 0.7 wt% of a tin catalyst, preferably not more than about 0.6 wt% of a tin catalyst, more preferably not more than about 0.5 wt% of a tin catalyst, further preferably not more than about 0.3 wt% or less than 0.3 wt% of a tin catalyst, even more preferably not more than about 0.1 wt% of a tin catalyst, even more preferably less than trace amounts of a tin catalyst, and most preferably tin-free; or the composition comprises a tin catalyst in an amount of less than 0.7 wt% to about 0.6 wt%, about 0.6 wt% to about 0.5 wt%, about 0.5 wt% to about 0.4 wt%, about 0.4 wt% to about 0.3 wt%, about 0.3 wt% to about 0.2 wt%, about 0.2 wt% to about 0.1 wt%, about 0.1 wt% to about 0.05 wt%, less than about 0.05 wt% to tin-free or a combination thereof. Regarding the amount of tin in the two-component polyurethane adhesive composition, in a preferred embodiment, the adhesive composition contains no more than about 0.31 wt% tin, preferably no more than about 0.25 wt%, more preferably no more than about 0.2 wt%, and even more preferably no more than about 0.1 wt%.

[0114] 3. A two-component polyurethane adhesive composition according to Clause 1 or 2, wherein the composition comprises no more than about 0.1 wt% of a tertiary amine catalyst, such as no more than about 0.09 wt%, preferably no more than about 0.05 wt%, preferably less than 0.05 wt%, more preferably no more than about 0.01 wt%, more preferably no more than trace amounts of the tertiary amine catalyst, even more preferably less than trace amounts of the tertiary amine catalyst, and most preferably no tertiary amine catalyst; or the composition comprises a tertiary amine catalyst in an amount from less than about 0.1 wt% to no more than about 0.09 wt%, from 0.09 wt% to about 0.05 wt%, from about 0.05 wt% to about 0.01 wt%, from about 0.01 wt% to no tertiary amine catalyst.

[0115] 4. A two-component polyurethane adhesive composition according to any one of Clauses 1-3, wherein the polyol component of the prepolymer comprises at least one polyol having a number average molecular weight of at least about 4,000 Daltons, preferably having a number average molecular weight of at least about 6,000 Daltons, more preferably having a number average molecular weight of at least about 8,000 Daltons, even more preferably having a number average molecular weight of at least about 10,000 Daltons, and even more preferably having a number average molecular weight of at least about 12,000 Daltons.

[0116] 5. A two-component polyurethane adhesive composition according to any one of Clauses 1-4, wherein the composition has an NCO and OH index of at least about 85, preferably at least about 90, more preferably at least about 95, more preferably at least about 85 to at most about 140, more preferably at least about 90 to at most 140, further preferably at least about 90 to at most 130, even more preferably at least about 90 to at most 125, even more preferably at least about 95 to at most 125, even more preferably at least about 100 to about 120, even more preferably at least about 105 to less than about 120; or the amount of NCO and OH index may be about 85 to about 90, about 90 to about 100, about 100 to about 105, about 105 to about 110, about 110 to about 115, about 115 to about 120, about 120 to about 130, about 130 to about 140 and combinations thereof, preferably the NCO and OH index is measured when the volume ratio of prepolymer to curing agent is about 1:1.

[0117] 6. A two-component polyurethane adhesive composition according to any one of clauses 1-5, wherein at least one of the prepolymer, curing agent, and combinations thereof is heated at 23°C and 0.79°C. -1 The viscosity at the shear rate is not more than about 50,000 cP, preferably not more than about 30,000 cP, more preferably not more than about 25,000 cP, more preferably about 15,000 cP, and even more preferably greater than about 10,000 cP; or the viscosity may include not more than about 50,000 cP to about 40,000 cP, about 40,000 cP to about 30,000 cP, about 30,000 cP to about 20,000 cP, about 20,000 cP to about 10,000 cP, or a combination thereof.

[0118] 7. The two-component polyurethane adhesive composition according to any one of Clauses 1-6, wherein the amount of fumed silica in the prepolymer is less than about 50 wt%, preferably less than about 30 wt%, more preferably less than about 15 wt%, more preferably less than about 10 wt%, and most preferably less than about 5 wt%; or the composition may contain fumed silica in an amount of less than about 50 wt% to about 40 wt%, about 40 wt% to about 30 wt%, about 30 wt% to about 20 wt%, about 20 wt% to about 10 wt%, about 10 wt% to less than about 5 wt%, or a combination thereof.

[0119] 8. A two-component polyurethane adhesive composition according to any one of Clauses 1-7, wherein the amount of amine-free / tin-free catalyst does not exceed about 1 wt% of at least one of the prepolymer, curing agent or both.

[0120] 9. A two-component polyurethane adhesive composition according to any one of clauses 1-8, wherein the amine-free / tin-free catalyst comprises at least one of zirconium compounds, zinc compounds, bismuth compounds, and combinations thereof.

[0121] a. Preferably, if present, the zirconium compound is present in an amount not exceeding about 1.2 wt%, more preferably not exceeding about 0.9 wt%, further preferably not exceeding about 0.7 wt%, even more preferably not exceeding about 0.6 wt%, even more preferably at least about 0.1 wt%, and most preferably greater than about 0.15 wt%; or the composition may contain a zirconium compound in an amount not exceeding about 1.2 wt% to about 0.9 wt%, about 0.9 wt% to about 0.6 wt%, about 0.6 wt% to about 0.3 wt%, about 0.3 wt% to about 0.1 wt%, or a combination thereof.

[0122] b. Preferably, if present, the zinc compound is present in an amount not exceeding about 0.3 wt%, more preferably not exceeding about 0.1 wt%, further preferably not exceeding about 0.07 wt%, even more preferably not exceeding about 0.05 wt%, even more preferably at least about 0.01 wt%, and most preferably greater than about 0.015 wt%; or the composition may contain a zinc compound in an amount not exceeding about 0.3 wt% to about 0.1 wt%, about 0.1 wt% to about 0.05 wt%, about 0.05 wt% to about 0.01 wt%, or a combination thereof, and / or

[0123] c. Preferably, if present, the bismuth compound is present in an amount not exceeding about 0.3 wt%, more preferably not exceeding about 0.1 wt%, further preferably not exceeding about 0.05 wt%, even more preferably not exceeding about 0.03 wt%, even more preferably at least about 0.01 wt%, and most preferably greater than about 0.015 wt%; or the composition may contain an amount of bismuth compound not exceeding about 0.3 wt% to about 0.1 wt%, about 0.1 wt% to about 0.05 wt%, about 0.05 wt% to about 0.01 wt%, or a combination thereof.

[0124] 10. A two-component polyurethane adhesive composition according to any one of clauses 1-9, wherein the prepolymer further comprises at least one non-tertiary amine, preferably a primary amine, a secondary amine, or a combination thereof, and more preferably wherein the prepolymer has no more than trace amounts of free amine, more preferably less than trace amounts of free amine.

[0125] 11. A two-component polyurethane adhesive composition according to any one of clauses 1-10, wherein the composition has a Young's modulus of less than about 8 MPa, preferably less than about 7 MPa, more preferably less than about 6 MPa (e.g., less than 5 MPa), and more preferably at least about 3 MPa upon curing.

[0126] 12. A two-component polyurethane adhesive composition according to any one of Clauses 1-11, wherein the composition exhibits at least one of the following upon curing: an elongation of at least about 100%, preferably at least about 200%, more preferably at least about 300%; and / or a tensile strength of at least about 3 MPa, more preferably at most about 8 MPa, and even more preferably at most about 7 MPa.

[0127] 13. A two-component polyurethane adhesive composition according to any one of claims 1-12, further comprising a curing agent component, wherein the curing agent component comprises at least one amine-free / tin-free catalyst, preferably the amine-free / tin-free catalyst comprising at least one of a zinc-containing compound, a bismuth-containing compound, and combinations thereof, more preferably the amine-free / tin-free catalyst comprises at least about 0.025 wt% of the curing agent, more preferably the wt% comprises at least about 0.05%, more preferably the amine-free / tin-free catalyst comprises at least about 0.05 wt% of a zinc compound as the curing agent, even more preferably the amine-free / tin-free catalyst comprises both a zinc compound and a bismuth compound, and the wt% comprises more than about 0.05 wt% of the curing agent.

[0128] 14. A two-component polyurethane adhesive composition according to any one of clauses 1-13, wherein the prepolymer further comprises polymeric MDI with a functionality of at least about 2.0, preferably at least about 2.25, more preferably at least about 2.5, and even more preferably at least about 2.7.

[0129] 15. A two-component polyurethane adhesive composition according to any one of Clauses 1-14, wherein the prepolymer comprises a second polyol having a number average molecular weight of at least about 6,000 Daltons, preferably at least about 8,000 Daltons, more preferably at least about 10,000 Daltons, and more preferably at least about 12,000 Daltons.

[0130] 16. A two-component polyurethane adhesive composition according to any one of clauses 1-15, wherein the composition comprises a structural adhesive.

[0131] 17. A two-component polyurethane adhesive composition according to any one of clauses 1-16, wherein the amine-free / tin-free catalyst comprises a zirconium compound.

[0132] 18. A two-component polyurethane adhesive composition according to any one of Clauses 1-16, wherein the amine-free / tin-free catalyst comprises at least one of the following: zinc neodecanoate, zinc octanoate, zinc acetylacetonate, zinc oxalate, zinc acetate, bismuth carboxylate, bismuth oxide, bismuth tri(2-ethylhexanoate), bismuth trioctanoate (Bi-OC, 20% metal content), bismuth neodecanoate, bismuth octanoate, bismuth acetylacetonate, bismuth oxalate, and bismuth acetate, and combinations thereof.

[0133] 19. A two-component polyurethane adhesive composition according to any one of Clauses 1-16, wherein the amine-free / tin-free catalyst comprises at least one of the following: a zirconium chelate catalyst, a bismuth catalyst, a zinc catalyst, and combinations thereof.

[0134] 20. A two-component polyurethane adhesive composition according to any one of clauses 1-19, wherein the NCO% of the prepolymer comprises up to about 30%, preferably less than about 30%, more preferably less than about 20%, more preferably at least about 1%, further preferably at least about 3%, and even more preferably at least about 4% and up to about less than 20%.

[0135] 21. A two-component polyurethane adhesive composition according to any one of clauses 1-20, wherein the curing agent comprises a monofunctional alcohol, preferably the monofunctional alcohol comprises a terminal hydroxyl group and a hydrocarbon chain, more preferably the hydrocarbon chain comprises one or more polyether groups, even more preferably the monofunctional alcohol comprises a terminal hydrocarbon having fewer than 9 carbon atoms, preferably fewer than 8 carbon atoms, and a hydroxyl terminus, further preferably the main chain of the monofunctional alcohol comprises more than one alkoxyl unit, preferably at least two alkoxyl units, even more preferably the alkoxyl unit comprises at least one of ethylene oxide (EO), propylene oxide (PO), butane oxide (BO), and combinations thereof.

[0136] 22. The two-component polyurethane adhesive composition according to Clause 21, wherein the second component (curing agent) contains at most about 20 wt% of a monofunctional alcohol, preferably less than about 15 wt%, more preferably not more than about 10 wt%, even more preferably not more than about 5 wt%, further preferably at least about 1 wt%, even more preferably at least about 3 wt%; or the second component contains at least one of the following: about 1 wt% to about 5 wt%, about 5 wt% to about 10 wt%, about 10 wt% to about 15 wt%, about 15 wt% to about 20 wt%.

[0137] 23. A two-component polyurethane adhesive composition according to any one of clauses 1-22, wherein the curing agent comprises at least one multifunctional polyol having a number-average molecular weight of at least about 4,000 Daltons, preferably having a hydroxyl functionality of at least about 2, more preferably having a hydroxyl functionality of at least about 3, preferably having a number-average molecular weight of at least about 5,000 Daltons, more preferably at least about 8,000 Daltons, even more preferably at least about 10,000 Daltons, and even more preferably at least about 15,000 Daltons.

[0138] 24. The two-component polyurethane adhesive composition according to Clause 23, wherein the wt% of at least one polyfunctional polyol of the curing agent comprises at least about 10 wt% to at most about 75 wt% of the curing agent, preferably less than about 70 wt%, more preferably less than about 65%, further more preferably greater than about 15 wt%, further preferably at least about 20 wt%, even more preferably at least about 25 wt%, and most preferably at least about 30 wt%; or the at least one polyfunctional polyol of the curing agent is present in an amount of at least one of the following: about 10 wt% to about 20 wt%, about 20 wt% to about 30 wt%, about 30 wt% to about 40 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 60 wt%, about 60 wt% to about 70 wt%, about 70 wt% to about 75 wt%, or combinations thereof.

[0139] 25. A laminated article comprising a first substrate and a second substrate bonded together and an adhesive, wherein the adhesive comprises an adhesive composition of any one of clauses 1-24 in a cured form, and at least one of the first substrate and the second substrate comprises polycarbonate.

[0140] 26. The laminated article according to Clause 25, wherein one of the first or second substrates comprises polypropylene, preferably, the substrate comprising polypropylene is free of polycarbonate.

[0141] 27. The laminated article according to clause 25 or 26, wherein the laminated article exhibits good durability, preferably a tensile strength of at least about 3.0 MPa and at most about 7.5 MPa.

[0142] 28. A method for preparing a laminated article, comprising:

[0143] a. Applying the adhesive composition described in any one of clauses 1-24 to a first substrate, a second substrate, or both;

[0144] b. Sandwiching the adhesive composition between the first substrate and the second substrate; and

[0145] c. The adhesive is cured at a temperature not exceeding about 50°C, preferably not exceeding about 40°C, more preferably not exceeding about 35°C, more preferably not exceeding about 30°C, even more preferably not exceeding about 25°C, and most preferably at least about 15°C.

[0146] 29. The method according to Clause 28, further comprising applying a primer to one of a first substrate or a second substrate, preferably not applying the primer to one of a first substrate or a second substrate to which the composition of any one of Clauses 1-18 has been applied, and more preferably, the primer is disposed at a location that contacts the applied composition of any one of Claims 1-19 when clamped.

[0147] 30. The method according to any one of clauses 28 or 29, wherein at least one of the first substrate, the second substrate, or both comprises polycarbonate, preferably, the polycarbonate used herein includes polycarbonate blends.

[0148] 31. A two-component polyurethane adhesive composition according to any one of clauses 1-13 or 15-24, wherein the prepolymer further comprises an isocyanate compound, wherein the isocyanate compound comprises at least one of an aromatic monomeric isocyanate, an aromatic polymeric isocyanate, and combinations thereof, preferably having a functionality of at least about 2.0, more preferably not more than about 3.0, further preferably not more than about 2.7, even more preferably at least about 2.1, even more preferably at least about 2.15, optionally the isocyanate compound comprises MDI.

[0149] 32. A two-component polyurethane adhesive composition comprising a prepolymer component and a curing agent component, preferably the prepolymer comprising a reaction product of at least one isocyanate compound and at least one polyol component, more preferably the prepolymer comprising an isocyanate-terminated prepolymer, wherein the prepolymer comprises:

[0150] a. At least about 30 wt% of the polyol component, preferably no more than about 70 wt%, more preferably at least about 40 wt%, more preferably at least about 45 wt%, and even more preferably at least about 50 wt%; or the amount of the polyol component comprises at least about 30 wt% to about 40 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 60 wt%, about 60 wt% to about 70 wt%, or combinations thereof;

[0151] b. The composition comprises at least 0.05 wt% of an amine-free / tin-free catalyst, preferably at least about 0.075 wt%, more preferably at least about 0.1 wt%, further preferably at least about 0.25 wt%, and at least about 0.3 wt%; or the composition may comprise an amine-free / tin-free catalyst in an amount of at least about 0.05 wt% to about 0.1 wt%, about 0.1 wt% to about 0.15 wt%, about 0.15 wt% to about 0.2 wt%, about 0.2 wt% to about 0.25 wt%, about 0.25 wt% to about 0.3 wt%, greater than about 0.3 wt%, or a combination thereof, preferably with the amine-free / tin-free catalyst present in at least one of the prepolymer, the curing agent, and combinations thereof, more preferably with the amine-free / tin-free catalyst present in at least the prepolymer; and

[0152] c. The curing agent comprises a monofunctional alcohol, preferably comprising a terminal hydroxyl group and a hydrocarbon chain, more preferably comprising one or more polyether groups, even more preferably comprising a terminal hydrocarbon having fewer than 9 carbon atoms, preferably fewer than 8 carbon atoms, and a hydroxyl terminus, further preferably comprising more than one alkoxyl unit in the main chain of the monofunctional alcohol, preferably at least two alkoxyl units, even more preferably comprising at least one of ethylene oxide (EO), propylene oxide (PO), butane oxide (BO), and combinations thereof.

[0153] 33. The two-component polyurethane adhesive composition according to Clause 32, wherein the second component (curing agent) contains at most about 20 wt% of a monofunctional alcohol, preferably less than about 15 wt%, more preferably not more than about 10 wt%, even more preferably not more than about 5 wt%, further preferably at least about 1 wt%, even more preferably at least about 3 wt%; or the second component contains at least one of the following: about 1 wt% to about 5 wt%, about 5 wt% to about 10 wt%, about 10 wt% to about 15 wt%, about 15 wt% to about 20 wt%.

[0154] 34. A two-component polyurethane adhesive composition according to any one of clauses 32 or 33, wherein the curing agent comprises at least one multifunctional polyol having a number-average molecular weight of at least about 4,000 Daltons, preferably having a hydroxyl functionality of at least about 2, more preferably having a hydroxyl functionality of at least about 3, preferably having a number-average molecular weight of at least about 5,000 Daltons, more preferably at least about 8,000 Daltons, further preferably at least about 10,000 Daltons, and even more preferably at least about 15,000 Daltons.

[0155] 35. The two-component polyurethane adhesive composition according to Clause 34, wherein the wt% of at least one polyfunctional polyol of the curing agent comprises at least about 10 wt% to at most about 75 wt% of the curing agent, preferably less than about 70 wt%, more preferably less than about 65%, further more preferably greater than about 15 wt%, further preferably at least about 20 wt%, even more preferably at least about 25 wt%, and most preferably at least about 30 wt%; or the at least one polyfunctional polyol of the curing agent is present in an amount of at least one of the following: about 10 wt% to about 20 wt%, about 20 wt% to about 30 wt%, about 30 wt% to about 40 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 60 wt%, about 60 wt% to about 70 wt%, about 70 wt% to about 75 wt%, or combinations thereof.

[0156] The foregoing description of the properties of adhesives and alternative adhesives also applies to the second alternative implementation and is incorporated herein by reference as if completely rewritten.

[0157] All of the above embodiments can be combined with each other. In particular, the various aforementioned components in the composition, as well as the particularly preferred embodiments, can be combined with each other.

[0158] The compositions and their applications according to this disclosure can be prepared and used according to the examples listed below. These examples are used herein to illustrate the purposes of this disclosure and are not intended to be limiting, such as the preparation of the compositions and their applications.

[0159] Example

[0160] In the embodiments, adhesive failure modes for lap shear tests are provided.

[0161] CH: Cohesive failure – Both sides are coated with adhesive.

[0162] AD: Adhesion failure – There is no adhesive or residual adhesive on the substrate.

[0163] TF: Film failure - There is a thin adhesive layer on the surface of the substrate and a thick adhesive layer on the back side of the substrate.

[0164] exist Figure 1 In this embodiment, the adhesive is dark-colored, and the substrate is a transparent article. In each embodiment, the two laminated articles are separated to illustrate the failure modes. Image (A) illustrates AD, image (B) illustrates CH, and image (C) illustrates TF.

[0165] Example A

[0166] In Example A, samples 1-4 were prepared using the following materials, and the procedures used were as described below.

[0167] Procedures for preparing samples 1-4.

[0168] The polyol was loaded into the reactor. The reactor was heated to 90°C. When the reactor temperature reached 80°C, talc was loaded into the reactor and low-shear stirring was applied, such as at a rate less than approximately 800 rpm. Silica was slowly added during stirring, and stirring continued until the silica was uniformly dispersed in the reactor. The composition was further mixed at 93°C for 60 minutes under a vacuum above 27 mm Hg. The moisture content of the composition was sampled until it reached a moisture percentage below 400 ppm. The reactor was cooled to 83°C. Next, isocyanate Rubinate 9720 and molecular sieves were loaded into the reactor. Vacuum was reapplied, and the composition was stirred at 83°C for 2 hours. The reactor was then cooled to 70°C. K-KAT 6212 catalyst was added to the reactor, and the composition was stirred under vacuum for 30 minutes. The solids content, NCO% and the concentration at 23°C and 0.79 s were determined. -1 Viscosity at shear rate. NCO% was measured by titration using a Metrohm 800 Dasino, and viscosity was measured using a Discovery HR-1 cone-plate rheometer.

[0169] Table 1. Prepolymers of Samples 1-4

[0170]

[0171] In Example B, curing agent samples 5-8 were synthesized using the following procedures and materials.

[0172] The polyol was charged into the reactor. A vacuum was applied, and the reactor was heated to 94°C. At 94°C, talc and fumed silica were charged into the reactor, and low-shear stirring was applied until the talc and fumed silica were wetted. Next, the stabilizer and BDO were added to the reactor. Piperazine was added to the reactor, and the composition was mixed at 65-70°C for 30 minutes. Molecular sieves and catalyst were added to the reactor, and the composition was stirred at 65-70°C for 60 minutes. The composition was degassed at 65-70°C for 30 minutes. The composition was filtered, and the viscosity of each sample was checked and adjusted as needed. The viscosity at 23°C was 0.79 s⁻¹. -1 Examined at shear rate.

[0173] Table 2 Curing agents for samples 5-8

[0174]

[0175] As shown in Table 3 for samples 9-14, the prepolymers and curing agents prepared in Tables 1 and 2 were respectively loaded into side-by-side cylinders and pumped through a static mixing tube (a static mixer with 24 mixing tubes, the mixing tube width being 8.7 mm) to achieve complete mixing, as shown in Table 3. The mixed polymerizable adhesive composition was then applied directly from the static mixing tube to one side of the test substrate.

[0176] Table 3 Prepolymer and Curing Agent Combinations

[0177]

[0178] Overlap shear tests were performed to measure the lap shear strength and failure mode of the adhesive bond. Overlap shear specimens were prepared by overlapping 4×6-inch, 3 mm polycarbonate substrates, with adhesive and 0.76 mm glass spacer beads filling the overlap area. Both sides of the polycarbonate substrates had a film. The film was peeled off, and the adhesive was dispersed directly onto the substrate. Test specimens were placed under two steel bars at room temperature for at least 4 days. The lap shear test was performed according to ASTM D5868, with a crosshead rate of 2 inches per minute. ASTM D5868 is incorporated herein by reference in its entirety. Unless otherwise stated, all adhesives were prepared with an NCO and OH index ranging from about 95 to about 105.

[0179] Table 4. Overlap shear results under different conditions

[0180]

[0181] Environment: 72°C, 42% RH

[0182] Substrate: Polycarbonate, 3 mm thick, with protective film on both sides, which has been removed.

[0183] The prepolymer and curing agent were separately loaded into side-by-side cylinders and pumped through a static mixing tube (with 18 mixing elements, 8.7 mm wide) to achieve complete mixing. The mixed polymerizable adhesive composition was then applied directly from the static mixing tube to one side of the test substrate.

[0184] The test samples were formed with a 1” overlap and the adhesive thickness was 30 mil.

[0185] The lap shear test was performed according to ASTM D5868, with a beam speed of 0.5 per minute.

[0186] Curing conditions: Store at room temperature for at least 4 days, then test.

[0187] Failure mode naming: AD – Adhesion, FT – Fiber tearing, CH – Cohesion, TFC – Film cohesion, SB – Substrate fracture. 30%CH / 70%AD = 30% cohesion, 70% adhesion.

[0188] The results in Table 4 indicate that Sample 9 exhibits the highest lap shear strength, and the cohesive failure mode is generally preferred in such applications. Sample 9 is derived from prepolymer Sample 1, which was prepared using a high molecular weight polyol with a zirconium chelate catalyst. The zirconium chelate catalyst was used as a non-tin catalyst, suitable for two-component multi-gun applications or in-line mixing applications. Sample 9 exhibits a rapid curing response and a very good low-temperature curing response, as well as high selectivity for the -NCO / OH reaction relative to the -NCO / water reaction. The zirconium chelate catalyst is sensitive to moisture. Therefore, this product was designed to be premixed with the polyisocyanate component.

[0189] Sample 2 does not contain a zirconium catalyst with the same prepolymer composition, while Sample 6 contains a tin catalyst. Sample 10 (prepolymer sample 2 / curing agent sample 6) exhibits good lap shear strength and failure mode at room temperature and 82°C. However, the lap shear strength is lower after water immersion, and it exhibits an adhesion failure mode.

[0190] Sample 11 does not contain a zirconium catalyst in prepolymer sample 2, and its lap shear strength is much lower under all conditions.

[0191] Sample 12 contains a tin catalyst instead of a bismuth catalyst and a zinc catalyst, and exhibits lower lap shear strength under all conditions.

[0192] The prepolymer of sample 13 has a different composition compared to samples 1 and 2, and the curing agent contains tin catalyst and amine catalyst. Sample 13 exhibits lower lap shear strength under all conditions and shows undesirable failure modes after water immersion.

[0193] Sample 14 is a commercially available Pliogrip® low-modulus adhesive that has low lap shear strength and exhibits an adhesion failure mode.

[0194] Table 5. Composition of prepolymers with different isocyanates

[0195]

[0196] Table 6 Combinations of Prepolymer and Curing Agent

[0197]

[0198] Table 7. Overlap shear results under different conditions

[0199]

[0200] Samples 19-22 were prepared using prepolymers 15-18 with different isocyanate compounds. Sample 19, containing prepolymer sample 15 Rubinate® M, contains polymeric MDI with a functionality of 2.7. Sample 20, containing prepolymer sample 16 Mondur® MA2300, is a urea-formaldehyde modified 4,4'-diphenylmethane diisocyanate (MDI). Sample 21, containing prepolymer sample 17 Mondur® MRS 4, is a low- to medium-functionality polymeric diphenylmethane diisocyanate (pMDI) with a moderately high content of 2,4'-MDI isomers. Sample 22, containing prepolymer sample 18 Mondur MLQ monomeric diphenylmethane diisocyanate (MDI), contains a high percentage of 2,4-isomers. Sample 23 (below) Rubinate 9720 is the industry standard for carbodiimide-modified pure MDI, exhibiting higher reactivity, good adhesion, and flexibility. Prepolymers using different isocyanate compounds exhibit different mechanical properties.

[0201] Sample 23

[0202] Table 8 Composition of the prepolymer of sample 23

[0203]

[0204] Samples 24 and 25

[0205] Sample 24 contains only a bismuth catalyst in its curing agent, and sample 25 contains only a zinc catalyst in its curing agent.

[0206] Table 9 Composition of Curing Agent

[0207]

[0208] Table 10 Samples 27, 28 and 29

[0209]

[0210] Table 11. Overlap shear results under different conditions

[0211]

[0212] Sample 27 contains both bismuth and zinc catalysts in its curing agent and exhibits the best lap shear properties among samples 27-29. Sample 28 contains a bismuth catalyst in its curing agent and exhibits good lap shear strength and a favorable failure mode, with performance close to that of sample 27. The initial strength build-up of sample 28 is slightly slower than that of sample 27. Sample 29 contains only a zinc catalyst in its catalyst, and its room temperature lap shear strength is lower than both samples 27 and 28, and its initial strength build-up is much slower than that of sample 27. The combination of bismuth and zinc catalysts in the curing agent exhibits the most balanced performance.

[0213] Adhesive compositions having prepolymers comprising a second polyol having a number average molecular weight of at least about 12,000 Daltons exhibit an elongation of about 300%, which is an increase of 50% compared to adhesive compositions having a second polyol having a number average molecular weight of at most about 8,000 Daltons.

[0214] Table 14 Test results for sample 27, 1mm thick polycarbonate bond with 30% glass filler

[0215]

[0216] Table 15 General properties of the curing agent for Sample 27, prepolymer Sample 23 / Sample 24

[0217]

[0218] Table 16 Mechanical properties of the curing agents for Sample 27, prepolymer Sample 23 / Sample 24

[0219]

[0220] Example 30

[0221] The adhesive composition has a low NCO:OH index of 87.

[0222] Table 17 Composition of Prepolymer

[0223]

[0224] Table 18 Composition of Curing Agent

[0225]

[0226] Table 19 Adhesive Formulation

[0227]

[0228] Table 20 Overlap Shear Adhesive

[0229]

[0230] Although the invention has been described in detail with reference to certain preferred embodiments, it should be understood that this disclosure is not limited to these specific embodiments. Rather, in view of this disclosure, many modifications and variations will be made by those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. A two-component polyurethane adhesive composition comprising: a. A prepolymer component and a curing agent component, wherein the prepolymer comprises: i. At least about 30 wt% of a polyol component, preferably no more than about 70 wt%, more preferably at least about 40 wt%, more preferably at least about 45 wt%, and even more preferably at least about 50 wt%, and b. The composition comprises at least 0.05 wt% of an amine-free / tin-free catalyst, preferably at least about 0.075 wt%, more preferably at least about 0.1 wt%, and even more preferably at least about 0.25 wt%. Preferably, the amine-free / tin-free catalyst is present in at least one of the prepolymer, the curing agent, and combinations thereof. More preferably, the amine-free / tin-free catalyst is present in at least the prepolymer. The adhesive composition contains less than about 1 wt% precipitated calcium carbonate, preferably less than about 0.5 wt%, more preferably less than about 0.1 wt%, and even more preferably no precipitated calcium carbonate.

2. The two-component polyurethane adhesive composition according to claim 1, wherein the composition comprises less than 0.7 wt% of a tin-containing catalyst, preferably no more than about 0.6 wt% of a tin catalyst, more preferably no more than about 0.5 wt% of a tin catalyst, even more preferably no more than about 0.3 wt% of a tin catalyst, even more preferably less than 0.3 wt%, even more preferably no more than about 0.1 wt% of a tin catalyst, even more preferably no more than trace amounts of a tin catalyst.

3. The two-component polyurethane adhesive composition according to any one of claims 1 or 2, wherein the composition contains less than about 0.1 wt% of a tertiary amine catalyst, preferably not more than about 0.05 wt%, more preferably not more than about 0.01 wt%, even more preferably not more than trace amounts of the tertiary amine catalyst, even more preferably less than trace amounts of the tertiary amine catalyst.

4. The two-component polyurethane adhesive composition according to any one of claims 1-3, wherein the polyol component of the prepolymer comprises at least one polyol having a number average molecular weight of at least about 4,000 Daltons, preferably having a number average molecular weight of at least about 6,000 Daltons, more preferably having a number average molecular weight of at least about 8,000 Daltons, even more preferably having a number average molecular weight of at least about 10,000 Daltons, and even more preferably having a number average molecular weight of at least about 12,000 Daltons.

5. The two-component polyurethane adhesive composition according to any one of claims 1-4, wherein the composition has an NCO and OH index of at least about 85, preferably at least about 90, more preferably at least about 90 to at most about 140, further preferably at least about 95 to at most about 130, even more preferably at least about 100 to at most about 125, and most preferably at least about 105 to at most about 115, wherein the NCO and OH index is preferably measured when the volume ratio of prepolymer to curing agent is about 1:

1.

6. The two-component polyurethane adhesive composition according to any one of claims 1-5, wherein at least one of the prepolymer, curing agent, and combinations thereof has a viscosity of not more than about 50,000 cP at 23°C and a shear rate of 0.79 s⁻¹, preferably not more than about 30,000 cP, more preferably not more than about 25,000 cP, more preferably not more than about 15,000 cP, and even more preferably greater than about 10,000 cP.

7. The two-component polyurethane adhesive composition according to any one of claims 1-6, wherein the amount of fumed silica in the prepolymer is less than about 50 wt%, preferably less than about 30 wt%, more preferably less than about 15 wt%, more preferably less than about 10 wt%, and most preferably less than about 5 wt%.

8. The two-component polyurethane adhesive composition according to any one of claims 1-7, wherein the amount of amine-free / tin-free catalyst is not more than about 1 wt% of the prepolymer, curing agent, or both.

9. The two-component polyurethane adhesive composition according to any one of claims 1-8, wherein the amine-free / tin-free catalyst comprises at least one of a zirconium compound, a zinc compound, a bismuth compound, and combinations thereof. a. Preferably, if present, the zirconium compound is present in an amount not exceeding about 1.2 wt%, more preferably not exceeding about 0.9 wt%, even more preferably not exceeding about 0.7 wt%, even more preferably not exceeding about 0.6 wt%, even more preferably at least about 0.1 wt%, and most preferably greater than about 0.15 wt%. b. Preferably, if present, the zinc compound is present in an amount not exceeding about 0.3 wt%, more preferably not exceeding about 0.1 wt%, further preferably not exceeding about 0.07 wt%, even more preferably not exceeding about 0.05 wt%, even more preferably at least about 0.01 wt%, and most preferably greater than about 0.015 wt%, and / or c. Preferably, if present, the bismuth compound is present in an amount not exceeding about 0.3 wt%, more preferably not exceeding about 0.1 wt%, further preferably not exceeding about 0.05 wt%, even more preferably not exceeding about 0.03 wt%, even more preferably at least about 0.01 wt%, and most preferably greater than about 0.015 wt%.

10. The two-component polyurethane adhesive composition according to any one of claims 1-9, wherein the prepolymer further comprises at least one of a non-tertiary amine, preferably a primary amine, a secondary amine, or a combination thereof, and more preferably wherein the prepolymer has no more than trace amounts of free amine, more preferably less than trace amounts of free amine.

11. The two-component polyurethane adhesive composition according to any one of claims 1-10, wherein the composition has a Young's modulus of less than about 8 MPa, preferably less than about 7 MPa, more preferably less than about 6 MPa, and more preferably at least about 3 MPa upon curing.

12. The two-component polyurethane adhesive composition according to any one of claims 1-11, wherein the composition comprises a structural adhesive.

13. The two-component polyurethane adhesive composition according to any one of claims 1-12, further comprising a curing agent component, wherein the curing agent component comprises at least one amine-free / tin-free catalyst, preferably the amine-free / tin-free catalyst comprises at least one of a zinc-containing compound, a bismuth-containing compound, and combinations thereof, more preferably the amine-free / tin-free catalyst comprises at least about 0.025 wt% of the curing agent, more preferably the wt% comprises at least about 0.05%, more preferably the amine-free / tin-free catalyst comprises at least about 0.05 wt% of a zinc compound as the curing agent, even more preferably the amine-free / tin-free catalyst comprises both a zinc compound and a bismuth compound, and the wt% comprises more than about 0.05 wt% of the curing agent.

14. The two-component polyurethane adhesive composition according to any one of claims 1-13, wherein the prepolymer further comprises polymeric MDI with a functionality of at least about 2.0, preferably at least about 2.25, more preferably at least about 2.5, and even more preferably at least about 2.

7.

15. The two-component polyurethane adhesive composition according to any one of claims 1-14, wherein the prepolymer comprises a second polyol having a number average molecular weight of at least about 6,000 Daltons, preferably at least about 8,000 Daltons, more preferably at least about 10,000 Daltons, and more preferably at least about 12,000 Daltons.

16. The two-component polyurethane adhesive composition according to any one of claims 1-15, wherein the curing agent comprises a monofunctional alcohol, preferably the monofunctional alcohol comprises terminal hydroxyl groups and a hydrocarbon chain, more preferably the hydrocarbon chain comprises one or more polyether groups, even more preferably the monofunctional alcohol comprises terminal hydrocarbons having fewer than 9 carbon atoms, preferably fewer than 8 carbon atoms, further preferably the main chain of the monofunctional alcohol comprises more than 1 alkoxyl unit, preferably at least about 2 alkoxyl units, even more preferably the alkoxyl unit comprises at least one of ethylene oxide (EO), propylene oxide (PO), butane oxide (BO), and combinations thereof.

17. The two-component polyurethane adhesive composition according to any one of claims 1-16, wherein the curing agent comprises a second polyol component, the second polyol component comprising at least one multifunctional polyol having a number-average molecular weight of at least about 4,000 Daltons, preferably the multifunctional polyol having a hydroxyl functionality of at least about 2, more preferably a hydroxyl functionality of at least about 3, preferably the number-average molecular weight comprising at least about 5,000 Daltons, more preferably at least about 8,000 Daltons, further preferably at least about 10,000 Daltons, and even more preferably at least about 15,000 Daltons.

18. The two-component polyurethane adhesive composition according to any one of claims 1-17, wherein the NCO% of the prepolymer comprises less than about 30%, preferably less than about 20%, more preferably at least about 1%, further preferably at least about 3%, and even more preferably at least about 4% and at most less than about 20%.

19. The two-component polyurethane adhesive composition according to any one of claims 1-18, wherein the prepolymer comprises a reaction product of at least one isocyanate compound and at least one polyol, preferably, the prepolymer comprises an isocyanate-terminated prepolymer.

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