Polyurethane adhesive composition containing a flame retardant package

Abstract

A polyurethane adhesive composition comprising a flame retardant package, the flame retardant package comprising about 20% by weight or less of the polyurethane adhesive composition, preferably about 15% by weight or less, more preferably about 10% by weight or less. Preferably, the flame retardant package comprises about 15% by weight or less, preferably less than about 10% by weight, more preferably about 5% by weight or less, even more preferably about 4% by weight or less, and even more preferably about 3% by weight or less of a liquid phosphate ester, based on the weight of the composition, and a solid ammonium polyphosphate salt, the solid ammonium polyphosphate salt comprising "n" ammonium phosphate units, "n" being at least about 500, more preferably at least about 750, more preferably at least about 1000, and even more preferably at least about 1500. The composition may comprise a polyisocyanate component and a polyol component, the molar ratio of the polyisocyanate component to the polyol component being greater than about 1:1, preferably at least about 2:1, more preferably at least about 5:1, even more preferably at least about 10:1, and most preferably about 20:1 or less. An advantageous use of the adhesive composition is as a structural adhesive, preferably for one or more wood substrates, or for producing engineered wood articles.

Description

[Technical Field]

[0001] The disclosed process(es), procedure(s), method(s), product(s), result(s), and / or concept(s) (hereinafter collectively referred to as "the disclosure") generally relates to polyurethane-based adhesive compositions having a flame retardant package, uses of the compositions, and methods of bonding dissimilar or similar substrates using the adhesive compositions. [Background technology]

[0002] Structural adhesives are typically used for strong, robust structural bonds in industrial applications. Wood structural adhesives play a crucial role in the efficient utilization of wood resources. For thousands of years, wood has been bonded using natural adhesives (bioadhesives). In the 20th century, synthetic adhesives gradually replaced them because they were more effective, less expensive, and had better, more tunable properties. Synthetic wood adhesives are primarily based on four synthetic thermosetting resins: phenol-formaldehyde (PF), urea-formaldehyde (UF), melamine-formaldehyde (MF), and polymeric diphenylmethane diisocyanate (pMDI) resins. Formaldehyde-based wood adhesives typically emit formaldehyde. Therefore, concerns about formaldehyde emissions from engineered wood products, especially in indoor applications, have been a major driving force for safe adhesive systems. The introduction of polyurethane adhesive systems has proven to offer a reliable alternative to these formaldehyde-based wood adhesives. Due in part to their lack of formaldehyde emissions, lack of solvents, and rapid room temperature cure, polyurethane adhesives have continued to gain acceptance and demand in the structural wood adhesives industry. Furthermore, polyurethane structural wood adhesives offer unique properties due to the wide range of physical property variations that can be achieved by modifying their formulations.

[0003] Polyurethane adhesives are available as one-component and two-component systems. The most promising is one-component polyurethane adhesive (1C-PUR). The first one-component polyurethane adhesive to enter the engineered wood market was PURBOND HB110 (Purbond AG / Switzerland). One-component polyurethane adhesives have gained a large market share because they offer several advantages over conventional adhesive systems, such as no premixing required, reduced press time, rapid adhesion at room temperature, and a ductile, inconspicuous bond line. Nevertheless, obstacles still exist that prevent the more widespread use of 1C-PUR adhesives, such as the performance of 1C-PUR-glued wood under high thermal and humidity loads. Moisture and heat resistance remain one of the major issues preventing 1C-PUR from being used in large-scale structural wood joining.

[0004] U.S. Patent No. 9,649,826 discloses an adhesive system for producing lignocellulosic composites. The adhesive system includes a water-based primer composition and a polyurethane-based adhesive composition. The water-based primer composition consists of water, 10% by weight or less of a surfactant, 0-25% by weight of a polyol having a molecular weight of less than 5,000 daltons, and 0-10% by weight of a cosolvent. The polyol includes a water-soluble polyol, a water-dispersible polyol, or a water-emulsifiable polyol. Similarly, the surfactant includes a water-soluble surfactant or a water-emulsifiable surfactant.

[0005] Similarly, U.S. Patent Publication No. 20160168435 teaches an adhesive system for producing lignocellulosic composites, comprising a primer composition and a polyurethane-based adhesive composition. The primer composition is primarily composed of a polyalkylene glycol, a polyalkylene glycol monoether, and a polyalkylene glycol diether, each having a hydroxyl value of 30 mg KOH / g or less. The primer composition may further comprise a surfactant selected from siloxane-based surfactants; alkyl polyglucosides; alkoxylated fatty acids; alkoxylated alcohols; alkyl sulfosuccinates; acetylenic diols; and mixtures thereof.

[0006] No. 8,829,122 teaches impact modifiers obtained by the reaction of amphiphilic block copolymers. These impact modifiers are suitable for use in thermosetting epoxy resin adhesives.

[0007] Similarly, U.S. Patent No. 8,969,511 describes compositions containing special polyether block copolymers and, in particular, polyurethanes derived therefrom. These compositions are well suited as reactive hot-melt adhesive and / or coating materials.

[0008] US Patent Publication No. 20040109853 teaches biomolecules, such as proteins, as components of coatings and paints that include biomolecular compositions.

[0009] A flame retardant adhesive composition for structural bonding of wood is disclosed in PCT / EP2022 / 051298. The '298 application discloses a 1C-PUR flame retardant adhesive composition comprising a reactive polyurethane prepolymer, and the use of the adhesive composition for structural bonding of wood substrates.

[0010] A heat-resistant structural wood adhesive composition containing polyalkylene diphenylmethane diisocyanate (polymeric MDI or pMDI, also referred to herein as polymeric methylene diisocyanate), a polyol, and an aromatic polyol is disclosed in European Patent No. 2547743 (B1). This patent describes an adhesive composition that forms the basis of a heat-resistant, fire-resistant, and water-resistant polyurethane-based adhesive suitable for use in the manufacture of wood products, and a method for producing the adhesive. Finger-jointed lumber laminates produced using adhesives derived from this patent are reported to meet or exceed 60-minute fire ratings according to ASTM E 119 and ASTM D 7374. This patent teaches that the adhesive's heat resistance is the result of incorporating thermally stable aromatic polyol molecules into the polymer structure of a wood adhesive system composed of the reaction product of poly(methylene diphenyl diisocyanate), at least one polyether polyol and polyester polyol, and an aromatic polyol, which in a preferred embodiment is a hydroxyphenol.

[0011] From the above, it is clear that polyurethane adhesives have been used in wood bonding applications for quite some time. They have gained more momentum in recent years compared to phenolic or amino adhesives due to their lack of formaldehyde emission, ease of application, room temperature curing, and natural wood-colored bond lines. However, they do not have the favorable heat resistance or flame retardancy of phenolic or amino adhesives. Under fire conditions, urethane adhesives can gradually deteriorate, causing delamination and potentially leading to catastrophic failure in structural applications. Summary of the Invention

[0012] In one embodiment, the present disclosure provides a polyurethane adhesive composition comprising a flame retardant package, wherein the flame retardant package comprises about 20% by weight or less of the composition, preferably about 15% by weight or less, and more preferably about 10% by weight or less (the polyurethane adhesive composition is also referred to herein as the "flame retardant adhesive composition" or "flame retardant composition" or "adhesive composition"). Preferably, the flame retardant package comprises a liquid phosphate ester, and the composition comprises about 15% by weight or less, preferably less than about 10% by weight, more preferably about 5% by weight or less, even more preferably about 4% by weight or less, and even more preferably about 3% by weight or less of the liquid phosphate ester, based on the weight of the composition. The flame retardant package may also comprise a solid ammonium polyphosphate, wherein the solid ammonium polyphosphate comprises "n" ammonium phosphate units, where "n" is at least about 500, more preferably at least about 750, more preferably at least about 1000, and even more preferably at least about 1500. The composition further comprises a polyisocyanate component and a polyol component, wherein the molar ratio of the polyisocyanate component to the polyol component is greater than about 1:1, preferably at least about 2:1, more preferably at least about 5:1, even more preferably at least about 10:1, and most preferably no greater than about 20:1.

[0013] In another embodiment, the present disclosure provides a laminate comprising two wood substrates and the cured polyurethane-based adhesive composition described above, bonding the two wood substrates together. Preferably, at least one of the two wood substrates comprises a structural substrate, and more preferably, both of the two wood substrates comprise a structural substrate.

[0014] In yet another embodiment, the present disclosure provides a method for bonding a first substrate and a second substrate, the method comprising: (i) providing a first substrate having at least one surface and a second substrate having at least one surface, wherein the first substrate comprises a lignocellulosic substrate and the second substrate comprises a lignocellulosic substrate or a non-lignocellulosic substrate; (ii) applying the polyurethane-based adhesive composition described above to one surface of the first substrate or the second substrate, or to the surfaces of both the first and second substrates; (iii) sandwiching the composition between the first and second substrates; and (iv) curing the adhesive composition at a pressure of at least about 15 psi, preferably no more than about 300 psi, more preferably no more than about 200 psi, for a time of at least about 5 minutes.

[0015] Embodiments disclosed herein may also further include a flame retardant package comprising a liquid phosphate ester, preferably a liquid polymeric phosphate ester (e.g., Daiguard 770) and a solid ammonium polyphosphate (e.g., Exolit® AP422). The weight ratio of the liquid polymeric phosphate ester to the solid ammonium polyphosphate may comprise about 10:1 to about 1:6. Optionally, the flame retardant package may consist of the liquid polymeric phosphate ester and the solid ammonium polyphosphate.

[0016] In one embodiment, the flame retardant adhesive composition may contain polymeric MDI with a high 4,4' MDI content.

[0017] In another embodiment, the flame retardant composition comprises an NCO content of 5% to 25%, preferably 10% to 22%.

[0018] Optionally, the flame retardant composition may include other flame retardants such as, but not limited to, zinc borate, melamine polyphosphate, brominated flame retardants, chlorinated flame retardants, and combinations thereof.

[0019] The embodiments disclosed herein relate to formulating a polyurethane-based adhesive composition that exhibits excellent flame retardant performance for structural wood bonding applications. It may contain a liquid polymeric phosphate ester-based flame retardant used in combination with a solid flame-retardant ammonium polyphosphate. The preferred loading of these flame retardants may be about 0.1 to 7 wt %, preferably about 0.5 to 5 wt %, of the polyurethane-based adhesive composition.

[0020] Another composition embodiment included herein is a two-component polyurethane adhesive composition (also known as a two-part adhesive composition) comprising an NCO prepolymer, where the prepolymer comprises the reaction product of an isocyanate compound and a polyol. Preferably, the NCO content of the prepolymer is up to about 30%, more preferably about 1% to 20%, even more preferably less than about 20% to at least about 10%, or about 1% to 10%. The second component of the composition comprises a second polyol, preferably having a number average molecular weight of at least about 2,000 daltons, more preferably at least about 4,000 daltons, even more preferably at least about 8,000 daltons, and most preferably greater than 10,000 daltons. Another component comprises a flame retardant package, where the flame retardant package comprises about 20% by weight or less of the composition, preferably about 15% by weight or less, and more preferably about 10% by weight or less. The flame retardant package may comprise, based on the weight of the composition, about 15% by weight or less of a liquid phosphate ester, preferably less than about 10% by weight of a liquid phosphate ester, more preferably about 5% by weight or less of a liquid phosphate ester, even more preferably about 4% by weight or less of a liquid phosphate ester, even more preferably about 3% by weight or less of a liquid phosphate ester, and a solid ammonium polyphosphate salt comprising "n" ammonium phosphate units, wherein "n" is at least about 500, more preferably at least about 750, more preferably at least about 1000, and even more preferably at least about 1500.

[0021] The two-component adhesive composition may or may not contain a silane adhesion promoter selected from the group consisting of isocyanurate silane adhesion promoters, isocyanatosilane adhesion promoters, and combinations thereof, and when present, the concentration of the silane adhesion promoter comprises about 0.1 to 10 weight percent of the two-component polyurethane adhesive composition (a non-limiting example of an isocyanurate silane is 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione). Another optional component may include an epoxy-functional silane adhesion promoter. Alternatively, the two-component adhesive composition may comprise less than 0.1 wt. % (based on the weight of the two-component polyurethane adhesive composition) of a silane adhesion promoter selected from the group consisting of isocyanurate silane adhesion promoters, isocyanatosilane adhesion promoters, and combinations thereof, preferably less than about 0.05 wt. %, more preferably less than about trace amounts, and even more preferably no silane adhesion promoter; and / or may comprise less than 0.5 wt. % (based on the weight of the two-component polyurethane adhesive composition) of an epoxy-functional silane adhesion promoter, preferably less than about 0.1 wt. %, more preferably less than about 0.05 wt. %, and even more preferably no more than about trace amounts of an epoxy-functional silane adhesion promoter.

[0022] Preferred properties of the two-component adhesive (when cured) may include one or more of the following: (a) preferably, the adhesive has a tensile strength of at least about 1 MPa, more preferably at least about 5 MPa, even more preferably at least about 7 MPa, and even more preferably at least about 10 MPa; (b) a Young's modulus of at least about 1 MPa; (c) an NCO to OH index of at least about 80-130, preferably at least about 100, more preferably at least about 110, and even more preferably about 125 or less; and (d) combinations thereof. DETAILED DESCRIPTION OF THE INVENTION

[0023] Before describing in detail at least one embodiment of the inventive concept(s) by way of illustrative figures, experiments, results, and experimental procedures, it is to be understood that the inventive concept(s) are not limited in their application to the details of construction and arrangement of components set forth in the following description or illustrated in the figures, experiments, and / or results. The inventive concept(s) are capable of other embodiments or may be practiced or carried out in various ways. Accordingly, the terms used herein are intended to be accorded the broadest possible scope and meaning, and the embodiments are meant to be illustrative rather than exhaustive. It is also to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0024] Unless otherwise defined herein, scientific and technical terms used in connection with this disclosure shall have the meanings commonly understood by those of ordinary skill in the art. Furthermore, unless otherwise required by context, singular terms shall include the plural and plural terms shall include the singular. Generally, the nomenclature utilized in connection with this specification and the chemical techniques described herein are those well known and commonly used in the art. Reactions and purification techniques are performed according to manufacturer's specifications or as commonly accomplished in the art or as described herein.

[0025] All patents, published patent applications, and non-patent publications mentioned in this specification are indicative of the level of skill of those 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 by reference herein in their entirety, to the same extent as if each individual patent or publication was specifically and individually indicated to be incorporated by reference.

[0026] All of the compositions and / or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of the present invention have been described in preferred embodiments, it will be apparent to those skilled in the art that various changes can be made in the compositions and / or methods, and in the steps or sequence of steps of the methods described herein, without departing from the concept, spirit, and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the inventive concept(s) as defined by the appended claims.

[0027] As utilized in accordance with the present disclosure, the following terms, unless otherwise indicated, shall be understood to have the following meanings:

[0028] In the claims and / or specification, the use of the word "a" or "an" in conjunction with the term "comprising" may mean "one," but is also consistent with the meanings of "one or more," "at least one," and "one or more than one." The use of the term "or" in the claims is used to mean "and / or" unless expressly indicated to refer to alternatives only or where the alternatives are mutually exclusive; however, this disclosure supports the definition referring to alternatives only and "and / or." Throughout this application, the term "about" is used to indicate that a value includes the inherent variation of the device, the method employed to determine the value, and / or the variation that exists among test subjects. Use of the term "at least one" is understood to include not only one, but any quantity greater than one, including, but not limited to, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100, etc. The term "at least one" may range up to 100 or 1000 or more depending on the term with which it is accompanied, and in addition, the quantity of 100 / 1000 should not be considered limiting, as higher upper limits may also provide satisfactory results. Additionally, use of the term "at least one of X, Y and / or Z" is understood to include X alone, Y alone, and Z alone, as well as any combination of X, Y and Z.

[0029] As used in this specification and claim(s), the words "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") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0030] 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" includes at least one of A, B, C, AB, AC, BC, or ABC, and is intended to also include BA, CA, CB, CBA, BCA, ACB, or CAB, where order is important in the particular context. Continuing with this example, expressly included are combinations containing repeats of one or more items or terms, such as BB, AAA, ABB, BBC, AAABCCCC, CBBAAA, CABABB, etc. One of ordinary skill in the art will understand that there is typically no limit to the number of items or terms in any combination unless otherwise apparent from the context.

[0031] As used herein, the term "amphiphilic block copolymer" refers to a copolymer characterized by a hydrophilic block chemically linked to a hydrophobic block. The amphiphilic block copolymer may be a multiblock copolymer. Suitable, non-limiting examples of such amphiphilic multiblock copolymers may include diblock, triblock, tetrablock copolymers, etc.

[0032] The term "monomer" refers to a small molecule that chemically attaches to one or more monomers of the same or different type during polymerization to form a polymer.

[0033] The term "polymer" refers to a large molecule containing one or more types of monomer residues (repeating units) linked by covalent chemical bonds. By this definition, polymers encompass compounds in which the number of monomer units ranges from a very small number, which may more commonly be called oligomers, to a very large number.

[0034] References herein to compositions, weight percent of adhesive compositions, are intended to encompass the entire composition unless otherwise stated. For one-component polyurethane adhesive compositions, the weight percent is based on all components unless otherwise stated. For two-component polyurethane adhesive compositions, the weight percent is based on both the prepolymer and the curing agent (i.e., the two parts of the composition) unless otherwise stated.

[0035] Unless otherwise stated, standards referred to throughout this application are effective as of the filing date. Examples of methods that may be used to determine properties are listed below. However, these methods may be equally applicable, and the claims are not limited to the methods below unless otherwise stated in the claims.

[0036] Methods that can be used to determine number average molecular weight include, but are not limited to, gel permeation chromatography (GPC), vapor pressure osmometry, membrane osmometry, and vapor pressure depression spectroscopy.

[0037] NCO%: One technique for determining NCO% is ASTM D5155. Determining NCO% is not necessarily limited to the aforementioned technique. Unless otherwise stated, NCO% is the weight percent of free NCO in the prepolymer.

[0038] The NCO index (or NCO to OH index) is the equivalent ratio of isocyanate to hydroxyl-containing polyol.

[0039] Viscosity: Unless otherwise stated, viscosity was measured using a Brookfield viscometer with a number 6 spindle at 20 rpm at room temperature (20-25°C). An alternative device for measuring viscosity is a TA Instruments Discovery HR-1 rheometer with a cone-plate. The cone-plate may have a diameter of 40 mm. A typical measurement temperature is 23°C, and a typical shear rate is 0.79 l / s.

[0040] Tensile strength of adhesive: Tensile strength may be determined according to ASTM D-638. The embodiments disclosed herein are not limited to determining tensile strength according to the aforementioned ASTM standard.

[0041] Young's Modulus: While any suitable method or device may be used to determine the Young's modulus discussed herein, one exemplary device that may be used to measure this modulus is the LMEC-1 Young's Modulus Measuring Device.

[0042] Flame retardant performance reported herein may be measured according to the flame test CSA O177-06 Annex A.2 (sections 2.1.7 and 3.7 of ANSI 405) performed using a CLT sample configuration.

[0043] Hydroxyl number: The OH number may be determined according to ASTM D4274 Standard Test Method for Polyurethane Raw Materials Testing: Determination of the Hydroxyl Number of Polyols. The method for determining the OH number is not limited to the aforementioned ASTM standard. Certain titration methods may also be suitable.

[0044] The isomer ratio of the polyisocyanate component or the isocyanate compound may be measured by liquid chromatography / triple quadrupole tandem mass spectrometry (LC-QQQ) method.

[0045] Unless otherwise stated, by way of example, the meaning of "about X" is intended to mean "10% above or below the value of X."

[0046] In the context of the present invention, numerical ranges are understood to be inclusive, for example the range "between 0% and 25%" specifically includes the values ​​0% and 25%.

[0047] As used herein, the term "lignocellulosic substrate" refers to a substrate made from woody materials such as cellulose or lignin. Furthermore, the woody material may be a softwood or hardwood. Suitable examples of such lignocellulosic substrates may include, but are not limited to, solid wood, wood particle board, wood chip board, wood oriented strand board, wafer board, wood fiberboard, parallel strand lumber, laminated strand lumber, plywood, laminated veneer lumber, straw particle board, or straw fiberboard.

[0048] As used herein, the term "trace amount" preferably means an amount of at most 0.02% by weight, for example an amount of at most 0.01% by weight. In some cases, "less than a trace amount" may mean 0% by weight.

[0049] In one aspect, the present disclosure provides an adhesive, particularly a structural adhesive, that includes a flame retardant package. One embodiment of the adhesive (e.g., one embodiment of the structural adhesive) includes a polyurethane-based adhesive composition. The composition includes a flame retardant package, the flame retardant package comprising no more than about 20% by weight of the composition, preferably no more than about 15% by weight, and more preferably no more than about 10% by weight. Preferably, the flame retardant package includes a liquid phosphate ester, and has no more than about 15% by weight of the liquid phosphate ester, preferably less than about 10% by weight, more preferably no more than about 5% by weight, even more preferably no more than about 4% by weight, and even more preferably no more than about 3% by weight, based on the weight of the composition. The flame retardant package may also include a solid ammonium polyphosphate. The solid ammonium polyphosphate may also include "n" ammonium phosphate units, where "n" is at least about 500, more preferably at least about 750, more preferably at least about 1000, and even more preferably at least about 1500. Examples of suitable numbers of ammonium phosphate units may include at least about 2000, at least about 2500, and up to about 5000, e.g., 2000 to 5000 or 2500 to 5000. Optionally, the flame retardant package comprises no more than about 7% by weight of the composition, preferably no more than about 5% by weight.

[0050] The composition may further comprise a polyisocyanate component and a polyol component, wherein the molar ratio of the polyisocyanate component to the polyol component is greater than about 1:1, preferably at least about 2:1, more preferably at least about 5:1, even more preferably at least about 10:1, and most preferably up to about 20:1 (e.g., 1:1 to 20:1, preferably 2:1 to 20:1, more preferably 5:1 to 20:1, and more preferably 10:1 to 20:1).

[0051] In one preferred embodiment, the liquid phosphate ester may comprise a polymer.

[0052] In another embodiment, the polyurethane adhesive composition comprises a polymeric MDI, preferably the polymeric MDI comprises a 4,4' isomer content of at least about 20% by weight of the polyisocyanate component, more preferably at least about 25% by weight, even more preferably at least about 30% by weight, even more preferably at least about 35% by weight, and most preferably at least about 40% by weight.

[0053] In another embodiment, the polyisocyanate component / isocyanate compound may comprise a polymeric methylene diisocyanate (pMDI) having a 4,4' to 2,4' isomer ratio of at least about 2:1, preferably at least about 3:1, more preferably at least about 4:1, even more preferably at least about 6:1, even more preferably at least about 8:1, even more preferably at least about 10:1, and even more preferably at least about 12:1. The upper ratio limit may include up to about 20:1. In particular, the 4,4' to 2,4' isomer ratio of the polymeric methylene diisocyanate may be 2:1 to 20:1, preferably 3:1 to 20:1, more preferably 4:1 to 20:1, even more preferably 6:1 to 20:1, even more preferably 8:1 to 20:1, for example, 10:1 to 20:1, or 12:1 to 20:1.

[0054] In further embodiments of the polyurethane adhesive composition, the polyisocyanate component may comprise greater than about 35 wt. % polymeric MDI (pMDI), preferably at least about 40 wt. %, and more preferably up to about 50 wt. % (e.g., greater than about 35 wt. % to about 50 wt. %, or about 40 wt. % to about 50 wt. %), or alternatively, about 35 wt. % to about 75 wt. %, more preferably about 60 wt. % to less than about 75 wt. %, based on the weight of the polyisocyanate component; and / or, preferably, the monomeric MDI content of the polyisocyanate component may comprise less than about 45 wt. %, more preferably less than about 40 wt. %, even more preferably less than about 35 wt. %, and even more preferably less than about 30 wt. % based on the weight of the polyisocyanate component.

[0055] Examples of NCO contents of polyurethane adhesive compositions include at least about 5%, preferably at least about 10%, more preferably at least about 15%, even more preferably at most about 25%, and even more preferably about 23% or less. In particular, the NCO content may be 5-25%, or 5-23%, or 10-25%, or 10-23%, or 15-25%, or 15-23%.

[0056] The aforementioned flame retardant package may include an additional non-halogenated flame retardant, preferably the additional non-halogenated flame retardant includes at least one of zinc borate, melamine polyphosphate, or both.

[0057] In another optional embodiment of the flame retardant package, the flame retardant package preferably contains less than 5 wt. % of halogenated flame retardants, preferably less than about 3 wt. %, more preferably less than about 1 wt. %, and even more preferably no more than trace amounts of halogenated flame retardants. More preferably, this limitation on halogenated flame retardants applies not only to the flame retardant package but also to the polyurethane adhesive composition. The weight percentages described in this paragraph may be based on the weight percentages of the polyurethane adhesive composition.

[0058] In one embodiment, the polyurethane adhesive composition may have less than 0.1 wt. %, preferably less than about 0.05 wt. %, more preferably no more than a trace amount, and even more preferably less than a trace amount, of a silane adhesion promoter selected from the group including isocyanurate silane adhesion promoters, isocyanato silane adhesion promoters, and combinations thereof.

[0059] In another embodiment, the polyurethane adhesive composition may have less than 0.5 wt. %, preferably less than about 0.1 wt. %, even more preferably less than about 0.05 wt. %, more preferably no more than a trace amount, and even more preferably less than a trace amount of epoxy-functional silane adhesion promoter.

[0060] In a preferred embodiment, the polyurethane adhesive composition contains less than about 1% by weight of formaldehyde-containing and / or formaldehyde-forming compounds upon application of heat to the cured composition, preferably less than about 0.5% by weight, more preferably less than about 0.1% by weight, even more preferably no more than trace amounts, and even more preferably no more than trace amounts.

[0061] Any one of the embodiments of the polyurethane-based adhesive compositions described herein may include a rheology modifier, preferably the rheology modifier includes fumed silica, and even more preferably the amount of fumed silica includes about 7 wt.% or less, more preferably about 5 wt.% or less, even more preferably about 3 wt.% or less, and most preferably at least about 1 wt.%.

[0062] Optionally, the polyurethane adhesive composition may contain one or more additional rheology modifiers. Preferably, the additional rheology modifiers have a carbon content of at least 3% by weight. Preferably, the carbon content includes long-chain carbon side chains. Rheology modifiers with a carbon content of at least 3% function as thickeners, increasing the viscosity of the adhesive composition. Such rheology modifiers may also improve the shear properties of the adhesive composition. One example of a suitable rheology modifier is polydimethylsiloxane.

[0063] Other examples of possible rheology modifiers include, but are not limited to, bentonite, hectorite, colloidal silica, attapulgite, precipitated calcium carbonate, montmorillonite, fibers, zirconates, aluminates, cellulosics, polysaccharides, and polyamides, which may be present, for example, in an amount of about 0.01% to 5.0% by weight, based on the total weight of the adhesive composition.

[0064] The adhesive composition according to the present disclosure may further comprise a filler. Suitable examples of fillers include, but are not limited to, calcium carbonate, silica, barium sulfate, aluminum hydroxide (ATH), clay, calcium sulfate, talcum powder, mica powder, carbon black, graphite, glass fiber, and molecular sieves. Furthermore, the filler may be present in an amount of about 2.0% to 10% by weight, based on the total weight of the adhesive composition.

[0065] The adhesive composition according to the present disclosure further optionally includes an activator. A number of aliphatic and aromatic amines may be used as activators for purposes of the present disclosure. Suitable examples of such compounds include, but are not limited to, diaminobicyclooctane (DABCO), 2,2'-dimorpholinodiethyl ether (DMDEE), trimethylaminoethylethanolamine, N,N,N',N',N''-pentamethyldiethylenetriamine, N-ethylmorpholine, 2-methyl-2-azanorbornane, and guanidine. Other examples of activators may include, but are not limited to, organometallic compounds based on titanium, zinc, bismuth, or zirconium metals, such as dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, dibutyltin dimercaptide, zinc neodecanoate, zinc octoate, bismuth carboxylate, zirconium octoate, and different ligand chemistries surrounding the catalytic metal center, as well as alkali metal salts of carboxylic acids and phenols, such as calcium, magnesium, strontium, and barium salts of hexanoic, octanoic, naphthenic, and linolenic acids. The activator may be present in an amount of more than trace amounts to about 1.0 wt. %, based on the total weight of the adhesive composition.

[0066] The adhesive composition according to the present disclosure may further comprise at least one additional additive. The amount of the additional additive may vary from about 0.01% to 5.0% by weight based on the total weight of the adhesive composition. The additional additive may include, for example, an antifoaming agent. Suitable examples of antifoaming agents include, but are not limited to, polysiloxane compounds such as polysiloxane-polyalkylene copolymers.

[0067] Optionally, the adhesive composition may also include one or more surfactants, which may be non-functional surfactants or functionalized surfactants.

[0068] A preferred example of the polyol component of the polyurethane-based adhesive composition may comprise a polyether, preferably the polyether comprises a polyol ether diol, more preferably the polyol ether diol comprises a plurality of primary diols, even more preferably the polyol ether diol comprises a bisphenol A component, and even more preferably the polyol ether diol having a bisphenol A component comprises a plurality of primary hydroxyl units.

[0069] Further examples of polyol components that can be used to prepare the compositions of the present disclosure include polyols suitable for producing polyurethanes. These may be polyols based on polyalkylene oxides, polyesters, or combinations thereof, and may contain bulky side chains and / or long hydrophobic chains. Polyols based on polyalkylene oxides are often referred to as polyether polyols. Polyols may also include polyamide polyols, polycaprolactone polyols such as poly-ε-caprolactone polyols, polycarbonate polyols, hydroxy-terminated polybutadienes such as fully hydrogenated hydroxy-terminated polybutadiene and / or partially hydrogenated hydroxy-terminated polybutadiene, polyisobutylene diols, and mixtures thereof.

[0070] Further 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, and polybutylene glycol. Furthermore, homopolymers and / or copolymers of polyoxyalkylene polyols may be used. In particular, copolymers of polyoxyalkylene polyols may include an adduct of at least one compound selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, 2-ethylhexanediol-1,3-glycerin, 1,2,6-hexanetriol, trimethylolpropane, trimethylolethane, tris(hydroxyphenyl)propane, triethanolamine, triisopropanolamine, ethylenediamine, and ethanolamine with at least one compound selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide.

[0071] The polyether polyol can include polymers of propylene oxide and / or copolymers of ethylene oxide and propylene oxide. In one non-limiting embodiment, the polyether polyol is ethylene oxide-capped polypropylene oxide.

[0072] The polyether polyol may be an amphiphilic block copolymer, which means a copolymer characterized by a hydrophilic block chemically linked to a hydrophobic block.

[0073] Suitable examples of hydrophilic block segments may include, but are not limited to, polyethylene oxide (PEO) blocks, polyacrylamide (PAM) blocks, polyester blocks, polyamide blocks, and polysaccharide blocks.

[0074] Suitable examples of hydrophobic block segments may include, but are not limited to, polypropylene oxide (PPO) blocks, poly(methyl methacrylate) (PMMA) blocks, poly(styrene) blocks, polyvinyl chloride blocks, polyethylene blocks, and polydimethylsiloxane blocks.

[0075] In one non-limiting embodiment of the present disclosure, the hydrophilic block segment can be a PEO block. In another non-limiting embodiment of the present disclosure, the hydrophobic block segment can be a PPO block.

[0076] Furthermore, the polyether polyol block copolymer according to the present disclosure may be a diblock, triblock, or tetrablock copolymer. In one non-limiting embodiment of the present disclosure, the polyether polyol block copolymer may be a triblock polymer. In one non-limiting embodiment of the present disclosure, the polyether polyol triblock copolymer may be derived from repeating units of ethylene oxide (EO) and propylene oxide (PO). The polyether polyol block copolymer according to the present disclosure may be a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer (PEO-PPO-PEO):poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) block copolymer (PPO-PEO-PPO).

[0077] In one non-limiting embodiment of the present disclosure, the ethylene oxide (EO) and propylene oxide (PO) repeat units may be present in a weight ratio of about 1:10 to about 10:1. In one embodiment of the present disclosure, the weight ratio may range from about 1:5 to about 5:1, or from about 1:3 to about 3:1, or from about 1:2 to about 2:1, and in certain embodiments, the ratio may be up to about 10:1 or up to about 5:1.

[0078] The polyether polyols used in this disclosure may include one or more difunctional polyether polyols, one or more trifunctional polyether polyols, one or more tetrafunctional polyether polyols, or combinations thereof. The number average molecular weight of the difunctional polyether polyols can vary from about 2,000 to about 20,000 daltons, or from about 2,000 to 12,000 daltons. For example, Pluracol® P2010 is a polyether polyol having a number average molecular weight of 2,000 daltons, which is commercially available from BASF. PPG 2000, available from PPG, is another example of a suitable polyether polyol. The number average molecular weight of the trifunctional polyether polyols can vary from about 84 to about 20,000 daltons, or from about 100 to 12,000 daltons, including Pluracol® TP-440 polyol, commercially available from BASF. The number average molecular weight of the tetrafunctional polyether polyol can vary from about 100 to about 20,000 daltons, or from about 400 to 12,000 daltons. For example, Pluracol® 355 is a polyether polyol having a number average molecular weight of 600 daltons and is commercially available from BASF. In some embodiments, the polyether polyol has a molecular weight of at least 4,000 daltons. In another example, the polyether polyol has a molecular weight of about 4,000 daltons or greater, preferably less than about 3,000 daltons.

[0079] In one embodiment, the polyether polyol triblock copolymer according to the present disclosure may have a weight average molecular weight of less than 4,000 daltons. In one non-limiting embodiment of the present disclosure, the weight average molecular weight of the polyether polyol block copolymer may vary from 100 daltons to 2,000 daltons or from 2,000 daltons to 4,000 daltons. In other non-limiting embodiments, the weight average molecular weight of the polyether polyol may be less than 3,000 daltons, preferably less than 2,500 daltons. In a further example, the weight average molecular weight of the polyether polyol may be about 1,000 to 2,300 daltons.

[0080] With respect to the ratio of the weight average molecular weights of the various blocks of the polyether polyol, preferably the ratio is not greater than about 2:1, more preferably not greater than about 1.5:1, and even more preferably not greater than about 1.2:1.

[0081] Another property of interest for a polyether polyol can be its HLB (hydrophilic-lipophilic balance) value. Preferably, the polyol has an HLB value of 20 or less. Particular embodiments may have an HLB value in one of the following ranges: about 5-20, about 6-15, about 7-12, or about 8-10.

[0082] In addition to the polyether polyol block copolymer, the adhesive composition of the present disclosure may further contain a polyhydric alcohol or polyol. Polyols having 2 to 15 carbon atoms are suitable, such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, and glycerol. Other suitable, non-limiting examples of such polyols may include diol phosphates and aromatic polyols such as catechol, resorcinol, hydroquinone, 1,5-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,2'-biphenol, 4,4'-biphenol, bisphenol A, bisphenol F, bisphenol S, bisphenol H, bisphenol A ethoxylate, bisphenol A propoxylate, 2,5-bis(hydroxymethyl)furan, 3,4-bis(hydroxymethyl)furan, 2,6-pyridinedimethanol, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 1,4-benzenediethanol. The amount of such polyhydric alcohols or polyols may vary from about 0% to about 40% by weight, or from about 1% to about 40% by weight, or from about 1% to about 10% by weight, based on the total weight of the adhesive composition.

[0083] Optionally, the adhesive composition may include a polyester polyol. The polyester polyol may be used in place of or in combination with the polyether polyol. When the polyester polyol and the polyether polyol are used in combination, the weight percent of the polyether polyol is at least about 5 weight percent.

[0084] Polyester-based polyols (also called polyester polyols) can include amorphous and liquid polyester polyols, as well as fatty acid polyester polyols such as castor oil and vegetable oil with different molecular weights and functional groups.

[0085] 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, alkylhydroxylated amides of fatty acids, and cashew nut shell liquid.

[0086] Polyester polyols can be formed as the reaction product of one or more carboxylic acids with one or more polyols, such as diols and / or triols. Carboxylic acids useful for forming polyester polyols include, but are not limited to, adipic acid, glutaric acid, succinic acid, malonic acid, oxalic acid, and mixtures thereof. Diols useful for forming polyester polyols can include, but are not limited to, ethylene glycol, propanediol, butanediol, neopentyldiol, pentanediol, and hexanediol, and mixtures thereof. Triols considered useful for forming polyester polyols can include trimethylolpropane.

[0087] In one non-limiting embodiment, the polyester polyol can be obtained from the reaction of a triol with azelaic acid. The triol can be glycerol. One example of such a polyester polyol is Emerox® 14001, which is derived from natural oils and is commercially available from Emery Oleochemicals Company.

[0088] In two-component PUR adhesives, commercially available polyether polyol block copolymers can be used to prepare the isocyanate-terminated urethane prepolymers (as NCO prepolymers) described further herein. For example, Pluronic® series polyols available from BASF or Makon® series polyols available from Stepan can be used. Alternatively, polyether polyol block copolymers can also be prepared by methods known to those skilled in the art, such as those disclosed in Macromolecules 29, 6994-7002 (1996) and Macromolecules 33, 9522-9534 (2000) and J. Polym. Sci. Part B: Polym. Phys. 45, 3338-3348 (2007).

[0089] Other examples of suitable polyester polyols include polyglycol dicarboxylates, polycaprolactone polyols, polycaprolactones, and combinations thereof. Useful polyester polyols can be prepared from the reaction product of a polycarboxylic acid, its anhydride, its ester, or its halide, and a stoichiometric excess of a polyhydric alcohol. Suitable polycarboxylic acids include dicarboxylic and tricarboxylic acids, such as aromatic dicarboxylic acids, their anhydrides, and esters (e.g., terephthalic acid, isophthalic acid, dimethyl terephthalate, diethyl terephthalate, phthalic acid, phthalic anhydride, methylhexahydrophthalic acid, methylhexahydrophthalic anhydride, methyltetrahydrophthalic acid, methyltetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, and tetrahydrophthalic acid), aliphatic dicarboxylic acids, and and anhydrides thereof (e.g., maleic acid, maleic anhydride, succinic acid, succinic anhydride, glutaric acid, glutaric anhydride, adipic acid, hexanoic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, chlorendic acid, 1,2,4-butanetricarboxylic acid, decanedicarboxylic acid, octadecanedicarboxylic acid, dimer acid, dimerized fatty acid, trimer fatty acid, and fumaric acid), and alicyclic dicarboxylic acids (e.g., 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid).

[0090] Additional examples of suitable polyols from which the polyester polyols can be derived include aliphatic polyols, such as ethylene glycol, propanediols (e.g., 1,2-propanediol and 1,3-propanediol), butanediols (e.g., 1,3-butanediol, 1,4-butanediol), pentanediols (e.g., 1,5-pentanediol), 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols, propylene glycol, and the like. Coal, polypropylene glycols (e.g., dipropylene glycol and tripropylene glycol), 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, dimer diols, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, glycerol, tetramethylene glycol, polytetramethylene glycol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-methyl-1,8-octadiol, trimethylolpropane, glycerin, pentaerythritol, sorbitol, glucose, and combinations thereof.

[0091] Preferably, the polyester polyols may be amphiphilic. The properties described above for polyether polyols are equally applicable to polyester polyols, whether or not they are used in combination with polyether polyols.

[0092] The number average molecular weight of the polyester polyols typically varies from about 1,000 to about 20,000 daltons, or from 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 that may be used.

[0093] In another particular embodiment, the polyol component may have a number average molecular weight of at least about 15,000 daltons, preferably at least about 20,000 daltons, more preferably at least about 50,000 daltons, and most preferably greater than about 80,000 daltons. An example of a polyol component having a number average molecular weight of at least about 15,000 daltons is Hyperlite® E-855 polyoxyalkylene polyol.

[0094] The polyisocyanate component used to prepare the compositions of the present disclosure can include any isocyanate compound containing two or more isocyanate groups. Furthermore, the isocyanate can be a polyisocyanate including aromatic, aliphatic, araliphatic polyisocyanates, or mixtures thereof. The polyisocyanate can be a diisocyanate including aliphatic, cycloaliphatic, aromatic, or aliphatic-aromatic diisocyanates. Suitable examples of aliphatic and alicyclic diisocyanates include ethylene diisocyanate, ethylidene diisocyanate, propylene diisocyanate, butylene diisocyanate, trimethylene diisocyanate, cyclopentylene-1,3-diisocyanate, cyclohexylene-1,4-diisocyanate, cyclohexylene-1,2-diisocyanate, dichlorohexamethylene diisocyanate, furfuridene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1-isocyanato-2-isocyanatomethylcyclopentadiene ... The isocyanatomethylcyclohexane may include, but is not limited to, 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane (isophorone diisocyanate or IPDI), bis-(4-isocyanatocyclohexyl)-methane, 2,4'-dicyclohexylmethane diisocyanate, 1,3- or 1,4-bis-(isocyanatomethyl)-cyclohexane, bis-(4-isocyanato-3-methylcyclohexyl)-methane, α',α',α',α'-tetramethyl-1,3- and / or -1,4-xylylene diisocyanate, 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, 2,4- or 2,6-hexahydrotoluylene diisocyanate.

[0095] Similarly, suitable examples of aromatic and araliphatic diisocyanates are 2,4- and / or 2,6-toluene diisocyanate, diphenylmethane-2,4'- and / or 4,4'-diisocyanate (MDI), 2,2-diphenylpropane-4,4'-diisocyanate, xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, diphenyl-4,4'-diisocyanate, azobenzene-4,4'-diisocyanate, diphenyl ... These may include, but are not limited to, nitrosulfone-4,4'-diisocyanate, 2,4-tolylene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, 4,4',4''-triisocyanatotriphenylmethane, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4,4'-dimethyldiphenylmethane-2,2',5,5-tetratetraisocyanate, and modified aromatic diisocyanates containing carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups, or biuret.

[0096] In one non-limiting embodiment of the present disclosure, the isocyanate compound can be diphenylmethane diisocyanate (MDI). Diphenylmethane diisocyanate (MDI) can be used in monomeric or polymeric form. The monomeric form of MDI can include diphenylmethane-2,4'-diisocyanate (also referred to herein as the 2,4' isomer) or diphenylmethane-4,4'-diisocyanate (also referred to herein as the 4,4' isomer), or a mixture thereof. In one non-limiting embodiment of the present disclosure, the isocyanate compound is polymeric MDI (pMDI). The polymeric MDI used in the present disclosure can have an average isocyanate functionality of at least about 2. The isocyanate functionality of the polyisocyanate component can vary from about 2.0 to 3.0.

[0097] The polyisocyanate component of the present disclosure may contain free isocyanate (NCO) groups. The free isocyanate groups are typically obtained from the reaction of at least one isocyanate-containing compound with at least one polyether polyol. The free hydroxyl groups of the polyether polyol react with the free isocyanate groups. Compositions according to the present disclosure may have an isocyanate content of about 10% to about 75% by weight, or about 10% to about 70% by weight, or about 15% to about 50% by weight, or about 10% to about 45% by weight, or about 1% to about 40% by weight, based on the total weight of the composition.

[0098] In another embodiment applicable to any embodiment disclosed herein, the polyurethane adhesive composition may contain less than 2 wt. % of small molecules comprising at least one of tris-chloroisopropyl-phosphate (TCPP), tris(1,3-dichloroisopropyl)phosphate (TDCPP), tris-chloroethyl-phosphate (TCEP), and combinations thereof, preferably 1 wt. % or less, more preferably 0.5 wt. %, and even more preferably trace amounts or less.

[0099] The adhesive composition may also contain less than 10% by weight water, preferably less than about 1% by weight water, more preferably only trace amounts of water, and even more preferably the composition is free of water.

[0100] Any of the polyurethane-based adhesive compositions disclosed herein may have a viscosity of the adhesive composition, measured at room temperature (20 to 25°C) using a Brookfield viscometer with a No. 6 spindle at 20 rpm, of less than about 1,000,000 cP, preferably less than about 500,000 cP, even more preferably less than about 100,000 cP, more preferably less than about 50,000 cP, even more preferably about 30,000 cP or less, or preferably about 5,000 to 30,000 cP, more preferably about 6,000 to 25,000 cP, even more preferably about 20,000 cP or less (particularly about 6,000 to 20,000).

[0101] An example of a two-component polyurethane adhesive composition including a flame retardant package includes an NCO prepolymer comprising the reaction product of an isocyanate compound and a polyol (preferably the NCO% in the prepolymer is up to about 30%, more preferably about 1-20%, even more preferably at least 10% to less than 20%, or about 1-10%), and a second component including a second polyol (preferably having a number average molecular weight of at least about 2,000 daltons, more preferably at least about 4,000 daltons, even more preferably at least about 8,000 daltons, and most preferably greater than 10,000 daltons).

[0102] The components of the two-component polyurethane adhesive composition include a flame retardant package, which comprises about 20% by weight or less of the composition, preferably about 15% by weight or less, and more preferably about 10% by weight or less. The flame retardant package includes a liquid phosphate ester, which comprises about 15% by weight or less of the two-component polyurethane adhesive composition, preferably less than about 10% by weight, more preferably about 5% by weight or less, even more preferably about 4% by weight or less, and even more preferably about 3% by weight or less, based on the weight of the composition. Preferably, the liquid phosphate ester comprises a polymer. The flame retardant package also includes a solid ammonium polyphosphate salt, which comprises n ammonium phosphate units, where n is at least about 500, more preferably at least about 750, more preferably at least about 1000, even more preferably at least about 1500.

[0103] The two-component adhesive composition may optionally contain a silane adhesion promoter selected from the group consisting of isocyanuratosilane adhesion promoters, isocyanatosilane adhesion promoters, and combinations thereof, where the concentration of the silane adhesion promoter is about 0.1 to 10% by weight of the two-component polyurethane adhesive composition (non-limiting example of an isocyanuratosilane is 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione). Another optional component may include an epoxy-functional silane adhesion promoter, which may be included in the two-component adhesive composition in an amount of at least 0.5% by weight and up to about 20% by weight of the two-component polyurethane adhesive composition. The various types of silane adhesion promoters listed herein may be used in any combination thereof.

[0104] Alternatively, the two-component adhesive composition may comprise less than 0.1 wt. % of isocyanuratosilane adhesion promoters, isocyanatosilane adhesion promoters, and combinations thereof, preferably less than about 0.05 wt. %, more preferably no more than trace amounts and / or less than 0.5 wt. % of epoxy-functional silane adhesion promoters, preferably no more than trace amounts of epoxy-functional silane adhesion promoters.

[0105] Preferred properties of the cured two-component polyurethane adhesive (when cured) may include one or more of the following: preferably (1) a tensile strength of the adhesive of at least about 1 MPa, more preferably at least about 5 MPa, even more preferably at least about 7 MPa, and even more preferably at least about 10 MPa; (2) a Young's modulus of at least about 1 MPa; (3) an NCO / OH index of at least about 80-130, preferably at least about 100 (especially 100-130), more preferably at least about 110 (especially 110-130), and even more preferably about 125 or less (especially 110-125); and (4) combinations thereof.

[0106] Optionally, the two-component polyurethane adhesive may further comprise a tertiary amine, preferably comprising at least one of 1,4-diazabicyclo[2.2.2]octane solution, DBU (diazabicycloundecene), 1,4-diazabicyclooctane, and combinations thereof.

[0107] In preferred embodiments of the two-component adhesive composition, the number average molecular weight of the second polyol can comprise at least about 10,000 daltons, preferably at least about 20,000 daltons, more preferably at least about 35,000 daltons, even more preferably at least about 50,000 daltons, and most preferably at least about 80,000 daltons.

[0108] In one non-limiting embodiment of the present disclosure, the prepolymer can be referred to as an isocyanate-terminated urethane prepolymer.

[0109] Isocyanate-terminated urethane prepolymers can be prepared by mixing polyols, drying the polyols at a temperature of about 80°C to about 105°C, adding an isocyanate-containing compound (particularly a diisocyanate) at a temperature of about 65°C or less, and increasing the temperature to about 80°C to about 105°C. A typical residence time in this temperature range is about 1 hour, or until the isocyanate content (determined by n-butylamine titration) reaches equilibrium (or slightly lower). This reaction can be carried out under reduced pressure. As previously mentioned, isocyanate-terminated urethane prepolymers according to the present disclosure contain free NCO groups. Urethane prepolymers containing free NCO groups can be obtained by reacting an excess amount of an isocyanate-containing compound with a polyol (particularly a polyether polyol, or a mixture of a polyether polyol and a polyhydric alcohol). In one non-limiting embodiment of the present disclosure, the molar ratio of isocyanate-containing compound (NCO) to polyether polyol (OH) can vary from about 0.9 to about 1.5.

[0110] The polyurethane-based adhesive compositions disclosed herein may include or be structural adhesives, preferably the structural adhesives include either one-component or two-component adhesives.

[0111] Any one of the adhesive compositions described above may be used to form an engineered wood composite. The composite comprises any one of the adhesive compositions described above and a plurality of wood-based materials, with preferred examples of the wood-based materials including wood chips, wood strands, sawdust, wood particles, and combinations thereof. More preferably, the engineered wood composite has a three-dimensional shape, and even more preferably, the three-dimensional shape comprises any one of a board, a sheet, or a plank.

[0112] One use of the polyurethane adhesives disclosed herein includes using the adhesive to form a laminate. The laminate may include two wood substrates, and embodiments of the polyurethane adhesive compositions disclosed herein, in their cured state, bond the two wood substrates together, preferably at least one of the two wood substrates comprising a structural substrate, and more preferably both of the two wood substrates comprising a structural substrate.

[0113] Examples of construction materials for the substrates include one of wood particle board, wood chip board, oriented strand wood board, wafer board, wood fiberboard, parallel strand lumber, laminated strand lumber, plywood, laminated veneer lumber, straw particle board, or straw fiberboard, and the first substrate and the second substrate may comprise the same construction material, or preferably, the first substrate and the second substrate comprise different construction materials. The foregoing embodiments may include one or both of the substrates.

[0114] Wood substrates may also be described as lignocellulosic substrates. As used herein, the term "lignocellulosic substrate" refers to a substrate made from woody materials such as cellulose or lignin. Furthermore, the woody material may be a softwood or hardwood. Suitable examples of such lignocellulosic substrates include, but are not limited to, solid wood, wood particle board, wood chip board, oriented strand board, wafer board, wood fiberboard, parallel strand lumber, laminated strand lumber, plywood, laminated veneer lumber, straw particle board, or straw fiberboard.

[0115] Optionally, the laminate may include a primer (also referred to herein as a "primer composition"), preferably the primer comprises ammonium phosphate, more preferably ammonium dihydrogen phosphate.

[0116] A method of bonding a first substrate and a second substrate may include the following steps: (i) providing a first substrate having at least one surface and a second substrate having at least one surface, wherein the first substrate comprises a lignocellulosic substrate and the second substrate comprises a lignocellulosic substrate or a non-lignocellulosic substrate; and (ii) applying an adhesive composition disclosed above to one surface of the first substrate or the second substrate, or to both surfaces of the first substrate and the second substrate. (iii) sandwiching the composition between a first substrate and a second substrate; and (vi) curing the adhesive composition at a pressure of at least about 15 psi, preferably up to about 300 psi, more preferably up to about 200 psi, particularly 15-300 psi or 15-200 psi, for a time of at least about 5 minutes, preferably up to 440 minutes (particularly 5-440 minutes).

[0117] Substrates can be joined to form an adhesive bond. Generally, substrates should be joined according to the recommended assembly time instructions in the adhesive's technical literature, including open assembly time, closed assembly time, and pressing time. Typical assembly times for adhesives range from less than 1 minute to up to 75 minutes. Furthermore, the adhesive compositions of the present disclosure can be cured in conventional ways, for example, at ambient or elevated temperatures and under pressure. Curing typically involves applying pressures of about 15 psi to 300 psi, preferably up to about 200 psi (e.g., 15 to 200 psi), and using appropriate pressing times of about 5 minutes to typically up to about 440 minutes, to allow for the formation of a strong adhesive bond. Examples of suitable pressures can range from about 50 to about 220 psi, about 60 to about 200 psi, about 60 to about 190 psi, about 90 to about 185 psi, or about 60 to about 90 psi. Press times may vary based on the adhesive's recommended press times, for example, based on the type and amount of activator or catalyst used in the adhesive composition. Additionally, heat may also be applied in conjunction with pressure to accelerate the cure of the adhesive composition.

[0118] In another non-limiting embodiment of the present disclosure, the method for bonding a first substrate and a second substrate can also include applying a primer composition to either the first substrate or the second substrate, or to both the first substrate and the second substrate, before applying the polyurethane-based adhesive composition of the present disclosure. Application of the adhesive composition to the substrate surface according to the present disclosure can be carried out using conventional methods known in the relevant technical field, such as brushing, spraying, or coating techniques.

[0119] The adhesive composition according to the present disclosure may be applied immediately after applying a primer, or may be applied after a certain time interval. In one non-limiting embodiment of the present disclosure, the adhesive composition may be applied immediately after applying a primer to a substrate. In another non-limiting embodiment of the present disclosure, the adhesive composition may be applied within 24 hours to 7 days after applying a primer to a substrate.

[0120] The first and second substrates used herein may be made of the same or different materials. The first substrate used herein may be a lignocellulosic substrate, and the second substrate used herein may be a lignocellulosic or non-lignocellulosic substrate. The lignocellulosic substrate used in this bonding method refers to a substrate made from wood-based materials such as cellulose and lignin. The lignocellulosic substrate may be selected from softwoods or hardwoods. Suitable examples of such lignocellulosic substrates include, but are not limited to, solid wood, wood particle board, wood chipboard, oriented strand board, waferboard, wood fiberboard, parallel strand lumber, laminated strand lumber, plywood, laminated veneer lumber, straw particle board, or straw fiberboard. Similarly, suitable examples of non-lignocellulosic substrates include, but are not limited to, alloys, glass, ceramics, foams, plastics, composites, metals, and bovine or equine hooves.

[0121] The method may also include applying a primer to the surface of the first substrate or the second substrate before applying the adhesive composition, the primer comprising water (the primer is therefore also referred to as a water-based primer), preferably in the form of a mist, at least one of ammonium phosphate, preferably ammonium dihydrogen phosphate, and combinations thereof.

[0122] Alternatively, the present disclosure is not limited to structural adhesives. The polyurethane-based adhesive compositions described above may be used in non-structural applications.

[0123] Like the optional surfactant of the adhesive, the surfactant in the primer may be a non-functional surfactant, more preferably having no more than two hydroxyl units, and even more preferably having no more than one hydroxyl unit.

[0124] In another optional embodiment, the primer may have less than an effective amount of adhesion promoter, for example, about 3% by weight or less, preferably less than 1% by weight, more preferably no more than a trace amount of adhesion promoter, and even more preferably is substantially free of adhesion promoter.

[0125] Similarly, suitable examples of alkylphenol ethoxylates that can be used in the primer composition of the present disclosure include, but are not limited to, tristyrylphenol ethoxylate, polyethoxylated tallow amine, decyl alcohol ethoxylate, undecyl alcohol ethoxylate, tridecyl alcohol ethoxylate, propylheptanol alcohol ethoxylate, amide ethoxylate, cocoamine ethoxylate, nonylphenol ethoxylate, ethoxylated octylphenol, castor oil ethoxylate, sorbitan ester ethoxylate, tridecyl alcohol alkoxylate, tall oil fatty acid ethoxylate, lauryl alcohol ethoxylate, and ethoxylated phenol. In one non-limiting embodiment of the present disclosure, the alkylphenol ethoxylate can be ethoxylated octylphenol. Additionally, the alkylphenol ethoxylate may be present in an amount of about 30% to about 50% by weight, or about 35% to about 50% by weight, or about 35% to about 45% by weight, based on the total weight of the primer composition.

[0126] The water present in the waterborne primer composition of the present disclosure can be filtered water, deionized water, distilled water, purified water, tap water, treated water, or any mixture thereof. In one non-limiting embodiment of the present disclosure, the water can be present in an amount of about 10% to about 30% by weight, or about 15% to about 25% by weight, based on the total weight of the primer composition. In another non-limiting embodiment of the present disclosure, the water can be mixed with at least one other solvent. Suitable examples of such solvents can include, but are not limited to, acetone, ethanol, methanol, and any combination thereof.

[0127] The water-based primer composition of the present disclosure may have a pH ranging from about 4 to about 8, or from about 5 to about 7.

[0128] The water-based primer composition of the present disclosure can be prepared by blending various components. The water-based primer composition according to the present disclosure can be in the form of a solution. The water-based primer composition of the present disclosure can be used as is or can be further diluted immediately before application. In one non-limiting embodiment of the present disclosure, the diluted form of the primer composition can contain about 0.5 wt % to about 9 wt % of the primer composition, based on the total weight of the diluted form of the primer composition.

[0129] Another aspect of the present disclosure relates to a method for bonding at least two substrates using a moisture-curable adhesive composition (i.e., a polyurethane-based adhesive composition) of the present disclosure. The method according to the present disclosure may include the following steps: (i) providing a first substrate having at least one surface and a second substrate having at least one surface; (ii) applying a moisture-curable adhesive composition of the present disclosure to at least one surface of the first substrate, or to at least one surface of the second substrate, or to both the first and second substrates; (iii) contacting the first substrate or the second substrate, or both the first and second substrates, bearing the composition for bonding; and (iv) curing the moisture-curable adhesive composition. The moisture-curable adhesive composition according to the present disclosure may be applied to one or both substrates. The substrates are then joined to form an adhesive bond. Generally, the substrates should be joined according to the recommended assembly time instructions provided in the technical literature for the adhesive, including the open assembly time, closed assembly time, and press time.

[0130] Typical assembly times for adhesives range from less than about 1 minute to up to about 75 minutes. Furthermore, adhesive compositions of the present disclosure can be cured in a conventional manner, for example, at ambient or elevated temperatures and under pressure. Curing typically involves applying pressures of about 15 psi to about 300 psi with a suitable press time of about 5 minutes to typically up to about 440 minutes to allow for the formation of a strong adhesive bond. Examples of suitable pressures can range from about 50 to about 220 psi, about 60 to about 200 psi, about 60 to about 190 psi, about 90 to about 185 psi, or about 60 to about 90 psi. Press times can vary based on the adhesive's recommended press time. For example, they can vary based on the type and amount of activator or catalyst used in the adhesive composition. Furthermore, heat can also be applied in conjunction with pressure to accelerate the cure of the adhesive composition.

[0131] In another non-limiting embodiment of the present disclosure, the method for bonding a first substrate and a second substrate can also include applying a primer composition to either the first substrate or the second substrate, or to both the first substrate and the second substrate, before applying the polyurethane-based adhesive composition of the present disclosure. Application of the adhesive composition to the substrate surface according to the present disclosure can be carried out using conventional methods known in the relevant technical field, such as brushing, spraying, or coating techniques.

[0132] The adhesive composition according to the present disclosure may be applied immediately after applying a primer, or may be applied after a certain time interval. In one non-limiting embodiment of the present disclosure, the adhesive composition may be applied immediately after applying a primer to a substrate. In another non-limiting embodiment of the present disclosure, the adhesive composition may be applied within 24 hours to 7 days after applying a primer to a substrate.

[0133] The first and second substrates used herein may be made of the same or different materials. The first substrate used herein may be a lignocellulosic substrate, and the second substrate used herein may be a lignocellulosic or non-lignocellulosic substrate. The lignocellulosic substrate used in this bonding method refers to a substrate made from wood-based materials such as cellulose and lignin. The lignocellulosic substrate may be selected from softwoods or hardwoods. Suitable examples of such lignocellulosic substrates include, but are not limited to, solid wood, wood particle board, wood chipboard, oriented strand board, waferboard, wood fiberboard, parallel strand lumber, laminated strand lumber, plywood, laminated veneer lumber, straw particle board, or straw fiberboard. Similarly, suitable examples of non-lignocellulosic substrates include, but are not limited to, alloys, glass, ceramics, foams, plastics, composites, metals, and cow or horse hooves.

[0134] In one embodiment of the present disclosure, the substrate may be pretreated prior to application of the adhesive. Such pretreatment may include physical inspection and / or cleaning methods, application of an adhesion promoter, an adhesion promoter solution, or a primer.

[0135] The method of bonding a first substrate and a second substrate according to the present disclosure results in a composite article. Composite articles are, among other structures, such as panels, pipes, decking, boards, housings, sheets, poles, straps, fences, components, doors, shutters, awnings, shades, signs, frames, window frames, backboards, wallboard, flooring, tiles, railroad ties, foam, trays, tool handles, stoles, bedding, dispensers, barrel timber, films, wraps, totes, barrels, boxes, packaging, baskets, straps, slips, racks, casings, binders, dividers, walls, indoor and outdoor carpets, rugs, fabrics, and mats, frames, bookshelves, sculptures, chairs, tables, etc. bulls, desks, art, toys, games, wharves, piers, boats, masts, pollution control products, septic tanks, automotive panels, substrates, computer housings, above and below ground electrical casings, furniture, picnic tables, tents, playgrounds, benches, shelters, sporting equipment, beds, commodes, yarn, filament, fabric, plaques, trays, hangers, servers, pools, insulation, coffins, book covers, clothing, canes, crutches, and other construction, agricultural, material handling, transportation, automotive, industrial, environmental, naval, electrical, electronic, recreational, medical, textile, or consumer products.

[0136] In yet another aspect, the present disclosure provides a composite article resulting from the bonding method described hereinabove. The composite article according to the present disclosure meets the requirements of Canadian Standards Association (CSA) standards O112.9 and PRG-320 for CLT applications.

[0137] The following clauses 1 to 26 are preferred.

[0138] Clause 1. A polyurethane-based adhesive composition comprising a flame retardant package, wherein the flame retardant package comprises about 20% by weight or less of the composition, preferably about 15% by weight or less, and more preferably about 10% by weight or less, and the flame retardant package may comprise a liquid phosphate ester (preferably about 15% by weight or less of the liquid phosphate ester, preferably less than about 10% by weight, more preferably about 5% by weight or less, even more preferably about 4% by weight or less, and even more preferably about 3% by weight or less, based on the weight of the composition), and a solid ammonium polyphosphate, wherein the solid ammonium polyphosphate comprises n ammonium phosphate units, where n is at least about 500, more preferably at least about 750, more preferably at least about 1000, and even more preferably at least about 1500. The composition also comprises a polyisocyanate component and a polyol component, wherein the molar ratio of the polyisocyanate component to the polyol component is greater than about 1:1, preferably at least about 2:1, more preferably at least about 5:1, even more preferably at least about 10:1, and most preferably about 20:1 or less. Further examples of suitable molar ratios can include 1.25:1, 1.5:1, 3:1, 4:1, 6:1, 7:1, 8:1, 9:1, 12:1, 15:1, 17:1, and 19:1.

[0139] Clause 2. The polyurethane adhesive composition of clause 1, wherein the liquid phosphate ester comprises a polymer.

[0140] Clause 3. The polyurethane adhesive composition of clause 1 or 2, wherein the adhesive composition comprises polymeric diphenylmethane diisocyanate ("polymeric MDI"), preferably the polymeric MDI having a 4,4' isomer content of at least about 20% by weight of the polyisocyanate component, more preferably at least about 25% by weight, even more preferably at least about 30% by weight, even more preferably at least about 35% by weight, and most preferably at least about 40% by weight.

[0141] Clause 4. The polyurethane adhesive composition of clause 1 or 2, wherein the polyisocyanate component of the adhesive composition comprises more than about 35% by weight of polymeric (MDI), preferably at least about 40% by weight of the polyisocyanate component, more preferably up to about 50% by weight, or from about 35% to about 75% by weight, more preferably from about 60% to less than about 75% by weight of polymeric MDI, and / or preferably the monomeric MDI content of the polyisocyanate component comprises less than about 45% by weight, more preferably less than about 40% by weight, even more preferably less than about 35% by weight, and even more preferably less than about 30% by weight of the polyisocyanate component.

[0142] Clause 5. The polyurethane adhesive composition of any one of clauses 1 to 4, wherein the adhesive comprises an NCO content of at least about 5%, preferably at least about 10%, more preferably at least about 15%, even more preferably up to about 25%, and even more preferably no more than about 23%.

[0143] Clause 6. The polyurethane adhesive composition of any one of clauses 1-5, wherein the flame retardant package further comprises an additional non-halogen flame retardant, preferably the additional non-halogen flame retardant comprises at least one of zinc borate, melamine polyphosphate, or both.

[0144] Clause 7. The polyurethane-based adhesive composition of any one of clauses 1-6, wherein the adhesive composition contains less than about 1% by weight of formaldehyde-containing and / or formaldehyde-forming compounds upon application of heat to the cured composition, preferably less than about 0.5% by weight, more preferably less than about 0.1% by weight, even more preferably no more than trace amounts, and even more preferably no more than trace amounts.

[0145] Clause 8. The polyurethane adhesive composition of any one of clauses 1-7, wherein the flame retardant package comprises no more than about 7% by weight of the polyurethane adhesive composition, preferably no more than about 5% by weight.

[0146] Clause 9. The polyurethane adhesive composition of any one of clauses 1 to 8, further comprising a rheology modifier, preferably the rheology modifier comprises fumed silica, and even more preferably the amount of fumed silica comprises no more than about 7% by weight of the polyurethane adhesive composition, more preferably no more than about 5% by weight, even more preferably no more than about 3% by weight, and most preferably at least about 1% by weight.

[0147] Clause 10. The polyurethane adhesive composition of any one of clauses 1 to 9, wherein the polyol component comprises a polyether, preferably the polyether comprises a polyol ether diol, more preferably the polyol ether diol comprises a plurality of primary diols, even more preferably the polyol ether diol comprises a bisphenol A component, and even more preferably the polyol ether diol having a bisphenol A component comprises a plurality of primary hydroxyl units.

[0148] Clause 11. The polyurethane adhesive composition of any one of clauses 1 to 10, wherein the adhesive composition comprises less than 2 wt. % of small molecules, the small molecules comprising at least one of tris-chloroisopropyl-phosphate (TCPP), tris(1,3-dichloroisopropyl)phosphate (TDCPP), tris-chloroethyl-phosphate (TCEP), and combinations thereof.

[0149] Clause 12. The polyurethane adhesive composition according to any one of Clauses 1 to 11, wherein the viscosity of the adhesive composition is less than about 1,000,000 cP, preferably less than about 500,000 cP, more preferably less than about 100,000 cP, more preferably less than about 50,000 cP, and even more preferably about 30,000 cP or less, or about 5,000 to 30,000 cP, preferably about 6,000 to 25,000 cP, and more preferably about 20,000 cP or less, as measured at room temperature (20 to 25°C) with a No. 6 spindle at 20 rpm.

[0150] Clause 13. The polyurethane adhesive composition of any one of clauses 1 to 12, wherein the adhesive composition comprises a structural adhesive, preferably wherein the structural adhesive comprises either a one-component adhesive or a two-component adhesive.

[0151] Clause 14. The polyurethane adhesive composition of any one of clauses 1 to 13, wherein the polyurethane adhesive composition contains less than 5% by weight of a halogenated flame retardant, preferably less than about 3% by weight, more preferably less than about 1% by weight, and even more preferably no more than a trace amount of a halogenated flame retardant.

[0152] Clause 15. The polyurethane adhesive composition of any one of clauses 1 to 14, wherein the polyurethane adhesive composition has less than 0.1 wt.%, preferably less than about 0.05 wt.%, more preferably no more than a trace amount, even more preferably less than a trace amount, of a silane adhesion promoter selected from the group consisting of isocyanuratosilane adhesion promoters, isocyanatosilane adhesion promoters, and combinations thereof, and / or the polyurethane adhesive composition has less than 0.5 wt.%, preferably less than about 0.1 wt.%, even more preferably less than about 0.05 wt.%, more preferably no more than a trace amount, even more preferably less than a trace amount, of an epoxy-functional silane adhesion promoter.

[0153] Clause 16. A two-component polyurethane adhesive composition comprising: an NCO prepolymer comprising the reaction product of an isocyanate compound and a polyol, wherein the NCO content in the prepolymer is preferably up to about 30%, more preferably about 1% to about 20%, even more preferably less than about 20% to at least about 10%, or about 1% to about 10%, and a second component comprising a second polyol, wherein the second polyol preferably has a number average molecular weight of at least about 2,000 daltons, more preferably at least about 4,000 daltons, even more preferably at least about 8,000 daltons, and most preferably greater than 10,000 daltons.

[0154] The components of the two-component polyurethane adhesive composition include a flame retardant package, which comprises about 20% by weight or less of the composition, preferably about 15% by weight or less, and more preferably about 10% by weight or less. The flame retardant package includes a liquid phosphate ester, which comprises about 15% by weight or less of the two-component polyurethane adhesive composition, preferably less than about 10% by weight, more preferably about 5% by weight or less, even more preferably about 4% by weight or less, and even more preferably about 3% by weight or less, based on the weight of the composition. Preferably, the liquid phosphate ester comprises a polymer. The flame retardant package also includes a solid ammonium polyphosphate salt, which comprises n ammonium phosphate units, where n is at least about 500, more preferably at least about 750, more preferably at least about 1000, and even more preferably at least about 1500.

[0155] The two-component adhesive composition may optionally contain a silane adhesion promoter selected from the group consisting of isocyanuratosilane adhesion promoters, isocyanatosilane adhesion promoters, and combinations thereof, where the concentration of the silane adhesion promoter is about 0.1 to 10% by weight of the two-component polyurethane adhesive composition (non-limiting example of an isocyanuratosilane is 1,3,5-tris[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione). Another optional component may include an epoxy-functional silane adhesion promoter, which may be included in the two-component adhesive composition in an amount of at least 0.5% by weight and up to about 20% by weight of the two-component polyurethane adhesive composition. The various types of silane adhesion promoters listed herein may be used in any combination.

[0156] Clause 16A. Alternatively, the two-component adhesive composition may comprise less than 0.1 wt. % of isocyanuratosilane adhesion promoters, isocyanatosilane adhesion promoters, and combinations thereof, preferably less than about 0.05 wt. %, more preferably no more than a trace amount, and / or less than 0.5 wt. % of epoxy-functional silane adhesion promoters, preferably no more than a trace amount, of epoxy-functional silane adhesion promoters. Preferred properties of the cured two-component polyurethane adhesive may include one or more of the following: preferably (1) a tensile strength of the adhesive of at least about 1 MPa, more preferably at least about 5 MPa, even more preferably at least about 7 MPa, and even more preferably at least about 10 MPa; (2) a Young's modulus of at least about 1 MPa; (3) an NCO to OH index of at least about 80 to about 130, preferably at least about 100, more preferably at least about 110, and even more preferably about 125 or less; and (4) combinations thereof.

[0157] Clause 17. The adhesive composition of clause 16 or 16A may further comprise a tertiary amine, preferably the tertiary amine comprises at least one of 1,4-diazabicyclo[2.2.2]octane solution, DBU (diazabicycloundecene), 1,4-diazabicyclooctane, and combinations thereof.

[0158] Clause 18. The two-component adhesive composition of any one of clauses 16, 16A or 17, wherein the number average molecular weight of the second polyol comprises at least about 10,000 daltons, preferably at least about 20,000 daltons, more preferably at least about 35,000 daltons, even more preferably at least about 50,000 daltons, and most preferably at least about 80,000 daltons.

[0159] Clause 19. An engineered wood composite comprising any one of the polyurethane adhesive compositions according to any one of clauses 1 to 18 and a plurality of wood-based materials, wherein preferred examples of the wood-based materials include wood chips, wood strands, sawdust, wood particles, and combinations thereof, more preferably the engineered wood composite has a three-dimensional shape, and even more preferably the three-dimensional shape comprises any one of a board, a sheet, or a plank.

[0160] Clause 20. A laminate comprising two structural wood substrates and the cured polyurethane adhesive composition of any one of clauses 1-18 bonding the two structural wood substrates together.

[0161] Clause 21. The laminate of clause 20, wherein the constituent material of at least one, and preferably both, substrates comprises any one of wood particle board, wood chip board, oriented strand wood board, wafer board, wood fiberboard, parallel strand lumber, laminated strand lumber, plywood, laminated veneer lumber, straw particle board, or straw fiberboard, and optionally the first substrate and the second substrate comprise the same constituent material, or preferably the first substrate and the second substrate comprise different constituent materials.

[0162] Clause 22. The laminate of any one of clauses 20 or 21, further comprising a primer, preferably the primer comprises ammonium phosphate, more preferably ammonium dihydrogen phosphate.

[0163] Clause 23. A method of bonding a first substrate and a second substrate, comprising: (i) providing a first substrate having at least one surface and a second substrate having at least one surface, wherein the first substrate is a wood substrate and the second substrate comprises a wood substrate or a non-wood substrate; (ii) applying the adhesive composition of any one of clauses 1 to 18 to a surface of either a first substrate or a second substrate, or to a surface of both the first substrate and the second substrate; (iii) contacting a first substrate, a second substrate, or both the first substrate and the second substrate carrying the composition for bonding; (iv) curing the adhesive composition at a pressure of at least about 15 psi, preferably at most about 300 psi, more preferably at most about 250 psi, and even more preferably at most about 200 psi, for a time of at least about 5 minutes; A method comprising:

[0164] Clause 24. The method of clause 23, further comprising applying a primer to the surface of the first substrate or the second substrate before applying the adhesive composition, wherein the primer comprises at least one of water, preferably in the form of a mist, ammonium phosphate, preferably ammonium dihydrogen phosphate, and combinations thereof.

[0165] Clause 25. The polyurethane adhesive composition of any one of clauses 1, 2, or 4-15, wherein the polyisocyanate component comprises a polymeric methylene diisocyanate (pMDI) having a 4,4' to 2,4' isomer ratio of at least about 2:1, preferably at least about 3:1, more preferably at least about 4:1, even more preferably at least about 6:1, even more preferably at least about 8:1, even more preferably at least about 10:1, and even more preferably at least about 12:1. The upper limit of the ratio may include up to about 20:1.

[0166] Clause 26. The two-component adhesive composition of any one of clauses 16-18, wherein the isocyanate compound comprises a polymeric methylene diisocyanate (pMDI) having a 4,4' to 2,4' isomer ratio of at least about 2:1, preferably at least about 3:1, more preferably at least about 4:1, even more preferably at least about 6:1, even more preferably at least about 8:1, even more preferably at least about 10:1, even more preferably at least about 12:1. The upper limit of the ratio may include up to about 20:1.

[0167] The contents of U.S. Provisional Patent Application No. 63 / 447,668, filed February 23, 2023, are incorporated by reference herein as if restated in full.

[0168] The foregoing descriptions of adhesive properties and alternative adhesives are equally applicable to the second alternative embodiment and are incorporated by reference herein as if restated in full.

[0169] All the embodiments described above can be combined with each other, in particular the various components described above in the compositions, particularly the preferred embodiments, can be combined with each other.

[0170] Compositions according to the present disclosure and their uses may be prepared and used in accordance with the examples set forth below, which are presented herein for the purpose of illustrating the disclosure and are not intended to limit, for example, the preparation of the compositions and their uses. [Example]

[0171] Examples of adhesive formulations containing flame retardant packages are set forth below.

[0172] Base polyurethane adhesive (BPUR) formulation A is synthesized using a combination of polyol and polymeric methylene diisocyanate (pMDI) (also known as diphenylmethane diisocyanate) having a 4:4' to 2:4' isomer ratio of about 8:1 to about 12:1 and an NCO content of 20%, and a molar ratio of polyisocyanate to polyol of about 13.

[0173] BPUR Formulation B is synthesized using a combination of polyol and polymeric methylene diisocyanate (pMDI, also known as diphenylmethane diisocyanate) having a 4,4' isomer to 2,4' isomer ratio of approximately 2:1 to 3:1 and an NCO content of 20%, and a molar ratio of polyisocyanate to polyol of approximately 13. [Table 1]

[0174] Adhesive formulations were produced by combining the listed BPUR with a flame retardant package. To avoid settling of the flame retardant package components, approximately 2% fumed silica was added to thicken the adhesive composition and prevent any settling. A Speedmixer was used to uniformly mix the BPUR, fumed silica, and flame retardant package composition.

[0175] To test the fire performance of wood glued assemblies, the CSA O177-06 Annex A.2 (ANSI 405 sections 2.1.7 and 3.7) test protocol was used for assembly and testing. The sample billet was assembled in a cross-laminated (CLT) configuration. It contained eight layers of wood assemblies bonded with different adhesive formulations, as listed in Tables 1-3. The wood assemblies were made of southern yellow pine with a specific gravity of 0.6.

[0176] The following ranking was adopted to evaluate the fire performance of the adhesive formulations: A total of seven bond lines per sample were tested under flame, and a total of three samples were evaluated for each adhesive composition (a total of 21 bond lines tested per adhesive formulation). [Table 2]

[0177] As shown in Table 2, adhesive formulations containing a combination of liquid phosphate ester and ammonium polyphosphate Type II (solid ammonium polyphosphate) exhibited the best fire performance compared to compositions that were liquid phosphate ester alone or ammonium polyphosphate Type II alone. [Table 3]

[0178] Table 3 demonstrates that BPUR compositions with higher 4,4'MDI isomers exhibit superior fire performance than those with relatively low 4,4'MDI isomer distribution.

[0179] Although the present invention has been described in detail with reference to certain preferred embodiments, it should be appreciated that the disclosure is not limited to those precise embodiments. Rather, many modifications and variations will become apparent to those skilled in the art in light of the present disclosure without departing from the scope and spirit of the invention.

Claims

1. 1. A polyurethane adhesive composition comprising a flame retardant package, comprising: the flame retardant package comprises no more than about 20% by weight of the polyurethane adhesive composition, preferably no more than about 15% by weight, and more preferably no more than about 10% by weight; The flame retardant package comprises: a. about 15% by weight or less, preferably less than about 10% by weight, more preferably about 5% by weight or less, even more preferably about 4% by weight or less, and even more preferably about 3% by weight or less of a liquid phosphate ester, based on the weight of the polyurethane adhesive composition; b. a solid ammonium polyphosphate comprising n ammonium phosphate units, wherein n is at least about 500, more preferably at least about 750, more preferably at least about 1000, and even more preferably at least about 1500; Including, 1. A polyurethane-based adhesive composition comprising a polyisocyanate component and a polyol component, wherein the molar ratio of the polyisocyanate component to the polyol component is greater than about 1:1, preferably at least about 2:1, more preferably at least about 5:1, even more preferably at least about 10:1, and most preferably not more than about 20:

1.

2. The polyurethane adhesive composition of claim 1 , wherein the liquid phosphate ester comprises a polymer.

3. 3. The polyurethane-based adhesive composition according to claim 1 or 2, wherein the polyisocyanate component of the adhesive composition comprises polymeric diphenylmethane diisocyanate (polymer (MDI)), and the polymer (MDI) comprises more than about 35% by weight of the polyisocyanate component, preferably at least about 40% by weight, more preferably up to about 50% by weight, or from about 35% to about 75% by weight, more preferably from about 60% to less than about 75% by weight, and / or preferably the monomeric content of MDI comprises less than about 45% by weight, more preferably less than about 40% by weight, even more preferably less than about 35% by weight, and even more preferably less than about 30% by weight of the polyisocyanate component.

4. 10. The polyurethane-based adhesive composition according to any one of the preceding claims, having an NCO content of at least about 5%, preferably at least about 10%, more preferably at least about 15%, even more preferably up to about 25% and even more preferably up to about 23%.

5. 10. The polyurethane-based adhesive composition according to any one of the preceding claims, wherein the flame retardant package further comprises an additional non-halogen flame retardant, preferably wherein the additional non-halogen flame retardant comprises at least one of zinc borate, melamine polyphosphate or both.

6. 10. A polyurethane-based adhesive composition according to any one of the preceding claims, comprising less than about 1 wt. % formaldehyde-containing and / or formaldehyde-forming compounds upon application of heat to the cured composition, preferably less than about 0.5 wt. %, more preferably less than about 0.1 wt. %, even more preferably no more than trace amounts, and even more preferably less than trace amounts.

7. 10. The polyurethane-based adhesive composition of any one of the preceding claims, wherein the flame retardant package comprises no more than about 7% by weight of the polyurethane-based adhesive composition, preferably no more than about 5% by weight.

8. 10. A polyurethane adhesive composition according to any one of the preceding claims, further comprising a rheology modifier, preferably wherein said rheology modifier comprises fumed silica, and even more preferably wherein the amount of fumed silica comprises no more than about 7% by weight of the polyurethane adhesive composition, more preferably no more than about 5% by weight, even more preferably no more than about 3% by weight, and most preferably at least about 1% by weight.

9. 10. A polyurethane-based adhesive composition according to any one of the preceding claims, wherein the polyol component comprises a polyether, preferably the polyether comprises a polyol ether diol, more preferably the polyol ether diol comprises a plurality of primary diols, even more preferably the polyol ether diol comprises a bisphenol A component, and even more preferably the polyol ether diol with the bisphenol A component comprises a plurality of primary hydroxyl units.

10. 10. A polyurethane-based adhesive composition according to any one of the preceding claims, wherein the adhesive composition comprises less than 2 wt% of small molecules, said small molecules comprising preferably 1 wt% or less, more preferably less than 0.5 wt%, and even more preferably no more than trace amounts of at least one of tris-chloroisopropyl-phosphate (TCPP), tris(1,3-dichloroisopropyl)phosphate (TDCPP), tris-chloroethyl-phosphate (TCEP) and combinations thereof.

11. 10. The polyurethane adhesive composition according to any one of the preceding claims, wherein the viscosity of the polyurethane adhesive composition comprises less than about 1,000,000 cP, preferably less than about 500,000 cP, even more preferably less than about 100,000 cP, more preferably less than about 50,000 cP, even more preferably about 30,000 cP or less, or preferably about 5,000 to 30,000 cP, more preferably about 6,000 to 25,000 cP, even more preferably about 20,000 cP or less, as measured by a Brookfield viscometer at 20 rpm using a No. 6 spindle at room temperature (20 to 25°C).

12. 10. The polyurethane adhesive composition of any one of the preceding claims, comprising a structural adhesive, preferably wherein the structural adhesive comprises either a one-component adhesive or a two-component adhesive.

13. 10. A polyurethane adhesive composition according to any one of the preceding claims, comprising less than 5% by weight of a halogenated flame retardant, preferably less than about 3% by weight, more preferably less than about 1% by weight, and even more preferably no more than a trace amount of said halogenated flame retardant.

14. 10. A polyurethane-based adhesive composition according to any one of the preceding claims, having less than 0.1 wt. %, preferably less than about 0.05 wt. %, more preferably no more than a trace amount, even more preferably less than a trace amount, of a silane adhesion promoter selected from the group comprising isocyanurate silane adhesion promoters, isocyanato silane adhesion promoters and combinations thereof, based on the weight of the polyurethane-based adhesive composition.

15. 10. A polyurethane adhesive composition according to any one of the preceding claims having less than 0.5 wt%, preferably less than about 0.1 wt%, even more preferably less than about 0.05 wt%, more preferably no more than a trace amount, and even more preferably less than a trace amount, of an epoxy-functional silane adhesion promoter, based on the weight of the polyurethane adhesive composition.

Images