Solvent-free adhesive composition

Abstract

A two-component solventless adhesive composition comprising: (A) at least one isocyanate component formulated for application to a first substrate, the at least one isocyanate component comprising either at least one aromatic isocyanate or a blend of (Ai) at least one aromatic isocyanate and (Aii) at least one aliphatic isocyanate; and (B) at least one isocyanate-reactive component formulated for application to a second substrate, the at least one isocyanate-reactive component comprising (Bi) at least one isocyanate-reactive component comprising a backbone incorporating two or more primary hydroxyl groups and a tertiary amine. and at least one isocyanate-reactive component comprising a blend of (Bii) at least one hydroxyl-terminated polyurethane polyol, (Biii) at least one phosphate ester polyol, (Biv) at least one polyester polyol, (Bv) at least one polyether polyol, and (Bvi) optionally at least one silane adhesion promoter; and a method for preparing the two-component solventless adhesive composition; and a laminate structure made using the two-component solventless adhesive composition.

Description

[Technical Field]

[0001] The present invention relates to solventless adhesive compositions, and more particularly to two-component solventless polyurethane laminating adhesive compositions for use in the manufacture of laminated structures. [Background technology]

[0002] Adhesive compositions are useful for a wide variety of purposes. For example, adhesive compositions are used to bond substrates such as polyethylene, polypropylene, polyester, polyamide, metal, paper, or cellophane together to form composite films, i.e., laminates. The use of adhesives in different end-use applications is generally known. For example, adhesives can be used in the packaging industry to produce film / film and film / foil laminates, particularly those used for food packaging. Among the many known laminating adhesive systems, polyurethane-based laminating adhesives are preferred due to their many desirable properties, including good adhesion, peel strength, heat seal strength, and resistance to aggressive filling goods. Adhesives used in laminating applications, i.e., "laminating adhesives," can generally be classified into three categories: solvent-based, water-based, and solventless. Adhesive performance varies depending on the category and the application to which the adhesive is applied. Two-component solventless adhesives are solvent-free adhesives and / or adhesives that are applied without solvents such as organic solvents or water. Two-component solvent-free adhesives are supplied as two separate components which are mixed together before application and subsequent curing.

[0003] Solventless laminating adhesives can be applied at up to 100 percent solids without the use of either an organic solvent or an aqueous carrier. Because solventless adhesives do not require drying of the organic solvent or water upon application, they can advantageously be applied and run at high line speeds, making them preferred for applications requiring rapid bonding. Solvent- and water-based laminating adhesives are limited by the rate at which the solvent or water can effectively dry and be removed from the laminate structure after application of the adhesive.

[0004] Furthermore, lamination adhesives are preferably water-based or solvent-free for environmental, health, and safety reasons. However, solvent-free adhesives often encounter problems such as short pot life, poor initial bond, slow bond development, slow primary aromatic amine ("PAA") and isocyanate ("NCO") decay, poor adhesion to metal surfaces, and poor chemical and heat resistance, especially in high performance applications such as boil-in-bag applications.

[0005] There are many types within the category of solventless laminating adhesives. One particular type includes premixed two-component polyurethane-based laminating adhesives, which are premixed prior to application and are referred to herein as "premixed two-component adhesives." Typically, two-component polyurethane-based laminating adhesives include a first component containing an isocyanate-containing prepolymer and / or polyisocyanate and a second component containing a polyol. The prepolymer can be obtained by reacting a polyether and / or polyester containing two or more hydroxyl groups per molecule with excess isocyanate. The second component is a polyether and / or polyester functionalized with two or more hydroxyl groups per molecule. The two components are combined, or "premixed," in a predetermined ratio and then applied to one of two substrates to be laminated together. For example, the adhesive is applied to a first substrate ("carrier web"), such as a film or foil substrate. The first substrate is then combined with a second substrate to form a laminate structure. Additional layers of substrates can be added to the laminate structure, with additional layers of adhesive composition disposed between each successive substrate. The adhesive is then cured at room temperature (about 23°C) or at an elevated temperature, thereby bonding the substrates together.

[0006] Further processing of laminate structures depends on the adhesive's cure rate. The adhesive cure rate is indicated by the time it takes for the mechanical bond between the laminated substrates to develop sufficiently to allow further processing, and the laminate to comply with applicable regulations (e.g., food contact regulations). Slow cure rates result in lower conversion efficiencies. Compared to traditional solvent-borne adhesives, premixed two-component solvent-free polyurethane laminating adhesives have weak initial bonds and exhibit slow cure rates (i.e., slow bond development) prior to lamination. Furthermore, these adhesives tend to exhibit poor chemical resistance, especially under acidic conditions. Traditional two-component solvent-free polyurethane-based laminating adhesives also exhibit slow primary aromatic amine and isocyanate decay, resulting in low conversion efficiencies.

[0007] A general trend in the converting industry is toward faster curing laminating adhesives. Faster cure improves converters' operational efficiency. Specifically, it increases production capacity and flexibility for fulfilling last-minute orders (e.g., retail promotional campaigns) by quickly moving finished products from warehouses. Therefore, to improve operational efficiency, laminates must be formed using adhesive compositions that are much more reactive than existing adhesive compositions. However, such highly reactive adhesive compositions present challenges for conventional adhesive application techniques. In other words, because solventless adhesive compositions are formulated to be more reactive and exhibit faster cure rates than existing adhesive compositions, the existing adhesive compositions are not ideally suited for use with existing adhesive application equipment. This is because the two components of existing adhesive compositions react so quickly that the adhesive gels, making it unsuitable for application to substrates.

[0008] Furthermore, such highly reactive adhesive compositions have shown limitations when used in laminate structures containing metal and / or metallized substrates and polymeric barrier substrates. At relatively high line speeds (e.g., speeds above 250 meters / minute [m / min]), defects can be visually observed in the resulting laminate. These defects are less severe, but are still noticeable at relatively slow line speeds (e.g., below 150 m / min). The defects are due, inter alia, to poor wetting and air entrainment during the lamination process, as well as CO2 evolution when the laminate is rewound.

[0009] Therefore, due to the advantages of lower cost and the desire in industry for more environmentally friendly adhesives, several two-component solvent-free adhesives have been developed to replace solvent-based adhesives, but solvent-based laminating adhesives are still used today to produce laminates for flexible packaging structures and the like. In some applications, solvent-based adhesives are still used because of the specific performance of such solvent-based adhesives and the properties of the substrates that are bonded together by the solvent-based adhesive. Therefore, not all two-component solvent-free laminating adhesives are useful for all structures and all applications.

[0010] Therefore, there remains a need for two-component solventless polyurethane-based laminating adhesive compositions that have improved bond strength, faster bond onset, faster cure rates without the need for the use of catalysts to accelerate the cure reaction, high performance application capabilities, higher line speeds on barrier laminate structures, improved chemical and heat resistance, faster decay of primary aromatic amines and isocyanates, and improved adhesion to metal substrates, metallized substrates, and / or polymeric barrier substrates. Summary of the Invention

[0011] The present invention relates to a two-component solventless polyurethane laminating adhesive formulation and a method for forming laminates using the solventless adhesive formulation. The adhesive composition of the present invention is particularly suitable for use in laminate structures including metal substrates, metallized substrates, or polymeric barrier substrates.

[0012] In some embodiments, the solventless adhesive composition includes an isocyanate component containing one or more isocyanates. For example, the isocyanate component includes at least one aromatic isocyanate or a blend of (i) at least one aromatic isocyanate and (ii) one or more other isocyanates selected from the group consisting of aromatic isocyanates, aliphatic isocyanates, and combinations thereof. The solventless adhesive composition further includes an isocyanate-reactive component such as a polyol, where the isocyanate-reactive component includes a blend of a highly reactive amine-initiated polyol, a hydroxyl (—OH)-terminated polyurethane polyol, a phosphate ester polyol, a polyester polyol, a polyether polyol, and optionally an aminosilane.

[0013] In one preferred embodiment, the solventless adhesive lamination formulation comprises (A) at least one isocyanate component, and (B) at least one isocyanate-reactive component (B), wherein the isocyanate component (A) comprises either (1) at least one aromatic isocyanate, or (2) a blend of (Ai) at least one aromatic isocyanate and (Aii) at least one aliphatic isocyanate, and the at least one isocyanate-reactive component (B) comprises a blend of (Bi) at least one amine-initiated polyol, (Bii) at least one hydroxyl-terminated polyurethane polyol, (Biii) at least one phosphate ester polyol, (Biv) at least one polyester polyol, (Bv) polyether polyol, and (Bvi) at least one silane adhesion promoter.

[0014] In another preferred embodiment, components (Bi) through (Bv), including component (B), can be used in the following concentrations based on the isocyanate-reactive components: (Bi) 0.5 weight percent (wt%) to 30 wt% of at least one amine-initiated polyol; (Bii) 10 wt% to 85 wt% of at least one hydroxyl-terminated polyurethane polyol; (Biii) 0.5 wt% to 40 wt% of at least one phosphate ester polyol; (Biv) 0.5 wt% to 50 wt% of at least one polyester polyol; (Bv) 1 wt% to 30 wt% of at least one polyether polyol; and (Bvi) 0 wt% to 5 wt% of at least one silane adhesion promoter.

[0015] The adhesive composition of the present invention exhibits a faster cure rate when used in laminate structures compared to existing two-component solventless adhesive compositions. However, to avoid the two components of the solventless adhesive composition reacting too quickly, causing the adhesive to gel and become unsuitable for application to a substrate, the two-component solventless adhesive composition of the present invention is formulated so that the isocyanate component and the isocyanate-reactive component are applied separately and independently to two different substrates, instead of being premixed and applied to a single carrier web. In one embodiment, the adhesive composition of the present invention is formulated so that the two substrates are applied separately and independently, and then combined to allow the adhesive composition applied to the substrates to mix and react.

[0016] For example, one component of the adhesive composition (e.g., an isocyanate component), i.e., component (A), is configured to be uniformly applied to the surface of a first substrate, and the other component of the adhesive composition (e.g., an isocyanate-reactive component), i.e., component (B), is configured to be uniformly applied to the surface of a second substrate. The surface of the first substrate coated with the first adhesive component is then contacted with the surface of the second substrate coated with the second adhesive component, causing the two components to mix and react to form a mixed, curable adhesive composition disposed between the first and second substrates, thereby forming an uncured laminate. In this manner, the adhesive composition can then be cured to bond the first and second substrates and form a cured laminate.

[0017] In one preferred embodiment, the method for forming the laminate of the present invention comprises: (I) applying a first coating layer of an isocyanate component to a surface of a first substrate; (II) applying a second coating layer of an isocyanate-reactive component to the surface of a second substrate; (III) contacting a coating layer of an isocyanate component on a surface of a first substrate with a coating layer of an isocyanate-reactive component on a surface of a second substrate to form a combined mixed adhesive formulation layer disposed between the first substrate and the second substrate; (IV) curing the adhesive formulation layer disposed between the first substrate and the second substrate to adhere / attach (i.e., bond or laminate) the first substrate to the second substrate.

[0018] In yet another embodiment, the present invention comprises a laminated structure prepared using the two-component solventless polyurethane laminating adhesive formulation described above. DETAILED DESCRIPTION OF THE INVENTION

[0019] In one broad embodiment, the two-component solventless adhesive composition of the present invention comprises (A) an isocyanate component and (B) an isocyanate-reactive component comprising a polyol component.

[0020] In one embodiment, component (A) of the two-component solventless polyurethane laminating adhesive formulation or composition for producing a laminate comprises at least one aromatic isocyanate or a blend of (Ai) at least one aromatic isocyanate, (Aii) at least one aliphatic isocyanate, and combinations thereof. In one embodiment, component (B) of the two-component solventless polyurethane laminating adhesive formulation or composition for producing a laminate comprises at least one isocyanate-reactive component comprising a polyol. The polyol component, component (B), comprises a novel combination, mixture, or blend of (Bi) at least one amine-initiated polyol, (Bii) at least one hydroxyl-terminated polyurethane polyol, (Biii) at least one phosphate ester polyol, (Biv) at least one polyester polyol, (Bv) at least one polyether polyol, and (Bvi) optionally at least one silane adhesion promoter.

[0021] Isocyanate component As mentioned above, the at least one isocyanate-containing component (A) used to produce the solventless adhesive of the present invention is, for example, at least one aromatic isocyanate, or a blend of (Ai) at least one aromatic isocyanate and (Aii) at least one aliphatic isocyanate. In one embodiment, the isocyanate component (A) of the present invention comprises, for example, two or more isocyanate-containing components selected from the group consisting of isocyanate monomers, polyisocyanates (e.g., dimers, trimers, etc.), isocyanate prepolymers, and mixtures of two or more thereof.

[0022] As used herein, a "polyisocyanate" is any compound containing two or more isocyanate groups. As used herein, an "isocyanate prepolymer" includes an isocyanate-terminated prepolymer. An isocyanate-terminated prepolymer is the reaction product of reactants including an isocyanate or polyisocyanate and a polyol. In such a reaction, an excess of isocyanate or polyisocyanate is present to produce the isocyanate-terminated prepolymer. An "isocyanate prepolymer" can be a polyisocyanate itself.

[0023] In some embodiments, polyisocyanates suitable for use in preparing the adhesive composition of the present invention can be selected from the group consisting of aromatic polyisocyanates, aliphatic polyisocyanates, and combinations thereof. An "aromatic polyisocyanate" is a polyisocyanate in which the isocyanate group is bonded to an aromatic group and contains one or more aromatic rings. An "aliphatic polyisocyanate" does not contain an isocyanate group directly bonded to an aromatic ring. That is, an "aliphatic polyisocyanate" is better defined as an isocyanate containing an isocyanate group bonded to an aliphatic group which can be bonded to another aliphatic group, an alicyclic group, or an aromatic ring (group).

[0024] Aromatic Isocyanates Suitable aromatic polyisocyanates include, but are not limited to, 1,3- and 1,4-phenylene diisocyanate, 1,5-naphthylene diisocyanate, 2,6-toluene diisocyanate ("2,6-TDI"), 2,4-toluene diisocyanate ("2,4-TDI"), 2,4'-diphenylmethane diisocyanate ("2,4'-MDI"), 4,4'-diphenylmethane diisocyanate ("4,4'-MDI"), 3,3'-dimethyl-4,4'-biphenyl diisocyanate ("TODI"), and mixtures of two or more thereof.

[0025] Aliphatic Isocyanate Suitable aliphatic polyisocyanates include cyclohexane diisocyanate, methyl cyclohexane diisocyanate, ethyl cyclohexane diisocyanate, propyl cyclohexane diisocyanate, methyl diethyl cyclohexane diisocyanate, propane diisocyanate, butane diisocyanate, pentane diisocyanate, hexane diisocyanate, heptane diisocyanate, octane diisocyanate, nonane diisocyanate, nonane triisocyanates such as 4-isocyanatomethyl-1,8-octane diisocyanate ("TIN"), decane di- and triisocyanates, undecane di- and triisocyanates, and dodecane di- and triisocyanates, isophorone diisocyanate ("IPDI"), hexamethylene diisocyanate ("HDI"), diisocyanatodicyclohexylmethane ("H12MDI"), 2-methylpentane diisocyanate ("MPDI"), 2,2,4-trimethylhexamethylene diisocyanate / 2,4,4-trimethylhexamethylene diisocyanate ("TMDI"), norbornane diisocyanate ("NBDI"), xylylene diisocyanate ("XDI"), tetramethylxylylene diisocyanate, and dimers, trimers, and mixtures of two or more thereof. Additional isocyanates suitable for use in the present invention include, but are not limited to, 4-methylcyclohexane-1,3-diisocyanate, 2-butyl-2-ethylpentamethylene diisocyanate, 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate, 2-isocyanatopropylcyclohexyl isocyanate, 2,4'-methylenebis(cyclohexyl)diisocyanate, 1,4-diisocyanato-4-methylpentane, and mixtures of two or more thereof.

[0026] In one preferred embodiment, the isocyanate component useful in the present invention can be MDI-based polyisocyanates, TDI-based polyisocyanates, HDI-based polyisocyanates, XDI-based polyisocyanates, and mixtures thereof.

[0027] Some commercially available examples of aromatic isocyanate components useful in the present invention include Isonate 125 M, MOR-FREE™ L75-100, PACACEL™ L75-191, Coreactant CT, and Catalyst F (all available from The Dow Chemical Company).

[0028] Some examples of commercially available aliphatic components useful in the present invention include, for example, TAKENATE® D-110N and TAKENATE® D-120N (both available from Mitsui Chemicals); DESMODUR® N 3300, DESMODUR® Quix 175, and DESMODUR® E 2200 / 76 (all available from The Covestro Company); and mixtures thereof.

[0029] The isocyanate component may further include other isocyanate-containing compounds generally known to those skilled in the art.

[0030] Compounds having isocyanate groups, such as the isocyanate component (A) of the present invention, can also be characterized by the weight percentage of isocyanate groups (NCO), based on the total weight of the isocyanate component. The weight percentage of isocyanate groups is referred to as "NCO%" and is measured in accordance with ASTM D2572-97. In one embodiment, the NCO content of component (A) is 7 NCO% or greater, and in another embodiment, the NCO content of component (A) is 10 NCO% or greater. In yet another embodiment, the NCO content of component (A) is 30 NCO% or less, and in yet another embodiment, the NCO content of component (A) is 25 NCO% or less.

[0031] The isocyanate component has an average functionality of greater than or equal to 2 isocyanate groups / molecule. In one embodiment, for example, the isocyanate may have an average functionality of 2 to 4.0. The isocyanate component has a viscosity at 25 degrees Celsius (°C) of 300 millipascal seconds (mPa s) to 40,000 mPa s, or 500 mPa s to 20,000 mPa s, or 1,000 mPa s to 15,000 mPa s, as measured by the method of ASTM D2196.

[0032] The amount of the aliphatic component used in the isocyanate component of the present invention is, for example, 0 to 40% by weight in one embodiment, 1 to 30% by weight in another embodiment, and 2 to 20% by weight in yet another embodiment. The amount of the aliphatic component used in the present invention is based on the total amount of components in component (A).

[0033] The amount of isocyanate in the adhesive composition is at least 20%, or at least 30%, or at least 40% by weight based on the weight of the adhesive composition (i.e., the total weight of the isocyanate component and the isocyanate-reactive component), and not more than 90%, or not more than 80%, or not more than 70% by weight based on the weight of the adhesive composition.

[0034] Isocyanate-reactive component As mentioned above, component (B), which is at least one isocyanate-reactive component used to produce the solventless adhesive of the present invention, comprises, for example, a blend of (Bi) at least one amine-initiated polyol, (Bii) at least one hydroxyl-terminated polyurethane polyol, (Biii) at least one phosphate ester polyol, (Biv) at least one polyester polyol, (Bv) at least one polyether polyol, and (Bvi) optionally at least one silane adhesion promoter. For example, the solventless adhesive comprises (Bi) a highly reactive amine-initiated polyol, (Bii) a hydroxyl-terminated polyurethane polyol, (Biii) a phosphate ester polyol, (Biv) a polyester polyol, (Bv) a polyether polyol, and (Bvi) optionally an aminosilane.

[0035] Amine-Initiated Polyols The amine-initiated polyol, component (Bi) of component (B), comprises a hydroxyl group and a backbone incorporating at least one tertiary amine. Amine-initiated polyols suitable for use in the adhesive compositions of the present invention are made by alkoxylating one or more amine initiators with one or more alkylene oxides. In some embodiments, the amine-initiated polyol has the following structure (I):

[0036] [ka] where n ranges from 0 to 4, x ranges from 10 to 30, and y ranges from 1 to 10. In some embodiments, the amine-initiated polyol comprises a tertiary amine and a secondary amine.

[0037] Amine-initiated polyols contain functionalities of 2 to 12, or 3 to 10, or 4 to 8. When used with respect to the polyol component, "functionality" refers to the number of isocyanate reactive sites per molecule. Furthermore, amine-initiated polyols contain a hydroxyl number (OH#) of 5 to 1,830, or 15 to 800, or 20 to 100, or 31 to 60. When used with respect to the polyol component, "hydroxyl number" or "OH#" is a measure of the amount of reactive hydroxyl groups available for reaction. This value is determined by wet analytical methods and reported as milligrams of potassium hydroxide equivalent to the hydroxyl groups found in one gram of sample (mgKOH / g). The most commonly used method for determining OH# is described in ASTM D 4274 D. Additionally, the amine-initiated polyol has a viscosity at 25°C of from 500 mPa.s to 40,000 mPa.s, or from 1,000 mPa.s to 30,000 mPa.s, or from 1,500 mPa.s to 20,000 mPa.s.

[0038] Some examples of commercially available amine-initiated polyol components useful in the present invention include, for example, VORANOL™ 800, VORANOL™ RA640, and SPECFLEXTMACTIV 2306 (all available from The Dow Chemical Company); MULTRANOL® 4063 and MULTRANOL® 9138 (both available from COVESTRO); and mixtures thereof.

[0039] The amount of amine-initiated polyol component used in the isocyanate-reactive compositions of the present invention is, for example, from 0.5% to 30% by weight in one general embodiment, from 2% to 25% by weight in another embodiment, and from 3% to 20% by weight in yet another embodiment, based on the weight of the isocyanate-reactive component. In one preferred embodiment, the concentration of amine-initiated polyol is from 5% to 15% by weight, based on the weight of the isocyanate-reactive component.

[0040] Examples of some advantageous properties exhibited by the amine-initiated polyol component of the present invention include providing higher reactivity and faster cure for use in two-component solventless adhesive compositions compared to conventional polyols used in existing two-component solventless adhesive compositions.

[0041] Hydroxyl-terminated polyurethane polyol Polyurethane polyols are compounds having a structure of urethane linkages and hydroxyl end groups. Suitable polyurethane polyols, component (Bii) of component (B) useful in the present invention, can be prepared by reacting a polyisocyanate with a polyol. In such a reaction, the polyol is present in excess to produce a hydroxy-terminated polyurethane polyol; in other words, the stoichiometric ratio of hydroxyl groups to isocyanate groups is greater than 1. Suitable polyisocyanates for use in preparing hydroxy-terminated polyurethane resins include, but are not limited to, aromatic polyisocyanates and aliphatic polyisocyanates. Suitable polyols for use in preparing hydroxy-terminated polyurethane resins include, but are not limited to, polyether polyols, polyester polyols, and mixtures thereof.

[0042] In one preferred embodiment, the polyurethane polyol component useful in the present invention can be (1) a reaction product of a polyether polyol with diphenylmethane diisocyanate, (2) a reaction product of a polyether polyol and / or an aliphatic polyester polyol with diphenylmethane diisocyanate, and (3) mixtures thereof. The polyether polyols used herein have a hydroxy functionality of 2 or greater (e.g., difunctional, trifunctional, etc.) and an OH# of 100 mg KOH / g to 400 mg KOH / g. In some embodiments, the polyether polyol has a number average molecular weight (M) of 100 g / mol to 3,000 g / mol, 200 g / mol to 2,500 g / mol, or 350 g / mol to 1,500 g / mol. nIn some embodiments, the polyether polyol has a viscosity of 50 mPa·s to 2,000 mPa·s at 25° C. Commercially available examples of polyether polyols suitable for use in accordance with the present disclosure include products sold under the trade names VORANOL™ CP-450, VORANOL™ 220-260, and VORANOL™ 220-110N, each available from The Dow Chemical Company.

[0043] The amount of hydroxyl-terminated polyurethane polyol used in the isocyanate-reactive component of the adhesive composition of the present invention is, for example, 10% to 85% by weight in one embodiment, 15% to 70% by weight in another embodiment, and 25% to 60% by weight in yet another embodiment.

[0044] Some advantageous properties exhibited by the polyurethane polyol component of the present invention include providing a viscosity suitable for adhesive applications and good wetting on a wide range of substrates, including polymeric films, metallized films and foils.

[0045] Phosphate ester polyol In one embodiment, the phosphate ester polyol, component (Biii) of component (B) useful in the present invention, has the following chemical structure (II):

[0046] [ka] [In the formula, R 1 In addition to the pendant groups shown in structure (II), R 1 may or may not have one or more additional pendant —OH groups, and R 1 may or may not have one or more additional pendant groups of structure (II). Any two or more of the —OH groups and groups of structure (II) may be 1In a preferred embodiment, each OH group and each group of structure (II) may or may not be bonded to the same atom of R 1 are bonded to separate atoms of

[0047] R 1 A convenient way to characterize is to identify the following structure (III):

[0048] [ka] [In the formula, R 1 is the same as that of structure (II). Compounds having structure (III) are referred to herein as "precursor polyols."

[0049] In some embodiments, suitable precursor polyols have an M of 90 g / mol or more in one embodiment, 200 g / mol or more in another embodiment, and 400 g / mol or more in yet another embodiment. n In some embodiments, suitable precursor polyols have an M of 4,000 g / mol or less in one embodiment, 2,000 g / mol or less in another embodiment, 1,200 g / mol or less in yet another embodiment, 900 g / mol or less in yet another embodiment, and 500 g / mol or less in yet another embodiment. n In some embodiments, suitable precursor polyols have an M in one embodiment from 200 g / mol to 4,000 g / mol, in another embodiment from 400 g / mol to 2,000 g / mol, in yet another embodiment from 400 g / mol to 1,200 g / mol, and in yet another embodiment from 400 g / mol to 900 g / mol. n It has.

[0050] In some embodiments, suitable precursor polyols include alkyl higher polyols, monosaccharides, disaccharides, and polyols having the following structure (IV):

[0051] [ka] [In the formula, R 2 , R 3 , R 4 , and R 5 each of n1, n2, and n3 is, independently of one another, an organic group, and each of n1, n2, and n3 is, independently of one another, an integer from 0 to 10. In addition to the pendant groups shown in structure (IV), R 2 may or may not have one or more additional pendant groups. Furthermore, two or more of the pendant groups may not be R 2 It will be understood that n1, n2, and n3 may or may not be bonded to the same atom of the molecule. In some embodiments, there are mixtures of compounds having structure (IV), where the compounds of structure (IV) differ from one another in the value of one or more of the parameters n1, n2, and n3. Such mixtures are described herein by stating a non-integer value for the parameters n1, n2, or n3, where the non-integer value represents a number average for that parameter. When it is desired to assess the molecular weight of such a mixture, the number average molecular weight is used.

[0052] Among the precursor polyols having structure (IV), in one preferred embodiment, each pendant group is R 2 Among the precursor polyols having structure (IV), in another preferred embodiment, R 3 , R 4 , and R 5 In one embodiment, one or more of R is a hydrocarbon group having 1C to 4C, in another embodiment, 2C to 3C, and in yet another embodiment, 3C. In yet another preferred embodiment of the precursor polyol having structure (IV), R 3 , R 4 , and R 5 is an alkyl group which may be linear or cyclic or branched or a combination thereof, and in yet another preferred embodiment, R 3 , R 4 and R 5 is a linear or branched alkyl group, and in yet another preferred embodiment, R 3 , R 4 and R 5In yet another preferred embodiment, one or more of R 3 , R 4 , and R 5 are identical to each other.

[0053] In one preferred embodiment of the precursor polyol having structure (IV), one or more of n1, n2, and n3 are 0 to 8. In another preferred embodiment of the precursor polyol having structure (IV), one or more of n1, n2, and n3 are 1 or greater. In yet another preferred embodiment of the precursor polyol having structure (IV), one or more of n1, n2, and n3 are 6 or less. In yet another preferred embodiment of the precursor polyol having structure (IV), n1, n2, and n3 are the same as one another.

[0054] In one embodiment, the group of precursor polyols having structure (IV) is R 2 , R 3 , R 4 , and R 5 are alkyl groups, and such precursor polyols are referred to herein as alkoxylated alkyl triols. In the triol, at least one of n1, n2, and n3 is 1 or greater, and R 2 has the following structure (V):

[0055] [ka] In an alkoxylated triol, R 3 , R 4 , and R 5 When each of R is a branched alkyl group having exactly three carbon atoms (C), the alkoxylated triol is referred to herein as a propoxylated triol. 2 The propoxylated triol having structure (V) is referred to herein as a propoxylated glycerol.

[0056] Among the precursor polyols that are higher alkyl polyols, in one embodiment the compounds have 10 or fewer carbon atoms, in another embodiment the compounds have 6 or fewer carbon atoms, in yet another embodiment the compounds have 3 or fewer carbon atoms, and in yet another embodiment the compound is glycerol.

[0057] In yet another embodiment, the precursor polyol is a compound having an alkyl higher polyol and structure (IV): When n1 is equal (=) so that n2=n3=0, and R 2 It should be noted that when is either an alkyl group or an alkyl group containing a hydroxyl group, the compound having structure (V) is an alkyl higher polyol.

[0058] In one embodiment, the group of precursor polyols is alkyltriols and alkoxylated alkyltriols. Among these compounds, glycerol and, in one embodiment, alkoxylated glycerol, in another embodiment, alkoxylated glycerol. Among the alkoxylated glycerols, in one preferred embodiment, propoxylated glycerol is used.

[0059] Another class of suitable phosphate ester polyols useful in the present invention includes compounds containing urethane linkages. Phosphate ester compounds containing urethane linkages are prepared by reacting one or more suitable phosphate-functional polyols with one or more polyisocyanates, including, in preferred embodiments, one or more diisocyanates. In preferred embodiments, the amount of polyisocyanate is kept low enough so that some or all of the reaction product is a phosphate-functional polyol. Alternatively, a polyol can be first reacted with a polyisocyanate to produce an -OH-terminated prepolymer, which is then reacted with polyphosphoric acid. Phosphate ester polyols with urethane linkages include those having an M in one general embodiment ranging from 1,000 g / mol to 6,000 g / mol, in another embodiment ranging from 1,200 g / mol to 4,000 g / mol, and in yet another embodiment ranging from 1,400 g / mol to 3,000 g / mol. n Examples of the compound include compounds having the formula:

[0060] In some embodiments, the phosphate ester polyol is the reaction product of a reactant comprising a precursor polyol and a phosphoric acid type acid, and the resulting phosphate ester polyol has the chemical structure of structure (II).

[0061] In one preferred embodiment, the amount of phosphoric acid and precursor polyol is M p :M x is chosen to determine the ratio of M hy = number of hydroxyl groups per molecule of precursor polyol; N x =M hy -2;M x = (number of moles of precursor polyol) × (N x );M p = number of moles of phosphorus atoms in a phosphoric acid type acid.

[0062] Generally, M p :M xIn one embodiment, the ratio of M is 0.1:1 or greater, in another embodiment, 0.2:1 or greater, in yet another embodiment, 0.5:1 or greater, and in yet another embodiment, 0.75:1 or greater. p :M x The ratio is 1.1:1 or less.

[0063] Generally, the weight ratio of phosphoric acid-type acid to precursor polyol is, in one embodiment, 0.005:1 or greater, in another embodiment, 0.01:1 or greater, and in yet another embodiment, 0.02:1 or greater, hi some embodiments, the weight ratio of phosphoric acid-type acid to precursor polyol is 0.3:1 or less, or 0.2:1 or less, or 0.12:1 or less.

[0064] In some embodiments, the phosphoric acid-type acid contains polyphosphoric acid. Generally, the amount of polyphosphoric acid in the phosphoric acid-type acid is, by weight based on the weight of the phosphoric acid-type acid, 75% by weight or more in one embodiment, 80% by weight or more in another embodiment, and 90% by weight or more in yet another embodiment. Polyphosphoric acid is available in various grades, each characterized by a percentage. To determine the grade, first recognize that pure monomeric orthophosphoric acid is considered to have a phosphorus pentoxide content of 72.4%. Any grade of polyphosphoric acid can also be analyzed, and one mole of polyphosphoric acid (formula weight designated "Fppa") is considered to contain the number of moles of phosphorus pentoxide designated "Nppo," and the percentage of phosphorus pentoxide ("PCppo") is determined by PCppo = (Nppo x 142) / Fppa, expressed as a percentage. The grade of the polyphosphoric acid is then the ratio: percentage:grade = PCppo / 72.4.

[0065] In some embodiments, the polyphosphoric acid used has a grade of 100 percent (%) or more in one embodiment, and 110% or more in another embodiment. In some embodiments, the polyphosphoric acid used has a grade of 150% or less in one embodiment, and 125% or less in another embodiment.

[0066] In some embodiments, the solvent-based adhesive compositions of the present disclosure contain one or more phosphorus-free polyols in addition to one or more phosphate-functional polyols.

[0067] Further information regarding suitable phosphate esters and the preparation of such suitable phosphate esters can be found, for example, in WO 2015 / 168670.

[0068] The amount of phosphate ester polyol used in the isocyanate-reactive component of the adhesive composition of the present invention is, based on the dry weight of the isocyanate-reactive component, component (B), in one embodiment from 0.1% to 30% by weight, in another embodiment from 0.2% to 20% by weight, in yet another embodiment from 0.5% to 10% by weight, and in yet another embodiment from 1% to 8% by weight.

[0069] Some of the advantageous properties exhibited by the phosphate ester polyols of the present invention include improved adhesion to metal surfaces and increased heat and product resistance of the adhesive.

[0070] Polyester Polyol Component (Biv) of component (B), the polyester polyol component useful in the present invention, comprises one or more polyester polyols. In one preferred embodiment, the polyester polyol useful in the present invention is an aliphatic hydrophobic polyester polyol.

[0071] In some embodiments, preferred polyester polyols are made from diols and diacids. Examples of diols suitable for use in preparing polyester polyols include neopentyl glycol, 2-methylpropylene diol, hexanediol, butanediol, propylene glycol, ethylene glycol, diethylene glycol, other alkylene diols having 6 to 16 carbon atoms in the backbone, and mixtures thereof. These diols may be used in combination of two or more. Examples of diacids suitable for use in preparing polyester polyols include adipic acid, azelaic acid, sebacic acid, and mixtures thereof. These diacids may be used alone or in combination of two or more diacids. In some embodiments, preferred polyester polyols are aliphatic hydrophobic polyols made from monomers containing neopentyl glycol.

[0072] The polyester polyols used herein have a hydroxy functionality of 2 and an OH# of 20 mg KOH / g to 250 mg KOH / g. In some embodiments, the polyester polyols have an M of 100 to 3,000 g / mol, 200 to 2,500 g / mol, or 350 to 1,500 g / mol. n In some embodiments, the polyether polyol has a viscosity at 25° C. of from 100 mPa·s to 20,000 mPa·s, from 200 mPa·s to 10,000 mPa·s, and from 1,000 mPa·s to 5000 mPa·s.

[0073] Some examples of commercially available aliphatic polyester polyol components useful in the present invention include, for example, ADCOTE® 113-7, ADCOTE® X108-53 (available from The Dow Chemical Company).

[0074] Some of the advantageous properties exhibited by the polyester polyol components of the present invention include improved heat and product resistance of adhesives, films, good wetting on metal substrates, and good compatibility with amine-initiated polyols to form clear, stable isocyanate-reactive components.

[0075] The amount of polyester polyol component used in the isocyanate-reactive component of the present invention is, for example, 0.5% to 50% by weight in one embodiment, 5% to 45% by weight in another embodiment, and 10% to 40% by weight in yet another embodiment. In one preferred embodiment, the concentration of polyester polyol is 20% to 40% by weight based on the isocyanate-reactive component.

[0076] Polyether polyol In some embodiments, the polyether polyol, component (Bv) of component (B), has a hydroxy functionality of 2 or greater (e.g., difunctional, trifunctional, etc.). In some embodiments, the polyether polyol has an OH# of 100 mg KOH / g to 400 mg KOH / g, as measured according to ASTM D4274. In some embodiments, the polyether polyol has an M of 100 to 3,000 g / mol, 200 to 2,500 g / mol, or 350 to 1,500 g / mol. nIn some embodiments, the polyether polyol has a viscosity of 50 mPa·s to 1,000 mPa·s at 25° C., as measured according to ASTM D4878. Commercially available examples of polyether polyols suitable for use in the present invention include products sold under the trade names VORANOL™ CP-450, VORANOL™ CP-755, VORANOL™ CP-1055, VORANOL™ 220-260, VORANOL™ 220-056N, and VORANOL™ 220-110N, each available from The Dow Chemical Company. In some embodiments, the amount of polyether polyol in the isocyanate-reactive component is from 1 wt % to 30 wt % in one embodiment, or from 3 wt % to 25 wt % in another embodiment, or from 5 wt % to 20 wt % in yet another embodiment, based on the weight of the isocyanate-reactive component.

[0077] silane adhesion promoter The optional silane adhesion promoter component, component (Bvi) of component (B) of the present invention, can comprise one or more aminosilanes. Examples of aminosilane adhesion promoters useful in the present invention include γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane, and mixtures thereof.

[0078] Some examples of commercially available silane adhesion promoter components useful in the present invention include, for example, SIQUEST™ A-1100 (available from MOMENTIVE PERFORMANCE MATERIALS); and GENIOSIL® GF-93 (available from WACKER).

[0079] The amount of silane adhesion promoter component used in the method of the present invention is, for example, from 0% to 5% by weight in one embodiment, from 0.2% to 3% by weight in another embodiment, and from 0.5% to 2% by weight in yet another embodiment, based on the isocyanate-reactive component.

[0080] In addition to the silane adhesion promoters described above, in some embodiments, the two-component solventless laminating adhesive compositions of the present invention may include one or more optional additives, including, but not limited to, for example, tackifiers, plasticizers, rheology modifiers, other adhesion promoters, antioxidants, fillers, colorants, surfactants, and combinations of two or more thereof.

[0081] The amount of optional ingredients, if used, can be, for example, 0% to 2% by weight in one embodiment, 0.01% to 1% by weight in another embodiment, and 0.1% to 0.5% by weight in yet another embodiment.

[0082] In one broad embodiment, the two-component solventless laminating adhesive composition of the present invention is prepared by thoroughly mixing, admixing, or blending a predetermined amount of at least one aromatic isocyanate or each of components (Ai) and (Aii) to form at least one isocyanate component, component (A) or "A-side" component, and thoroughly mixing, admixing, or blending a predetermined amount of each of components (Bi) through (Bvi) to form at least one isocyanate-reactive component, component (B) or "B-side" component. The A-side and B-side components become a reactive mixture when components (A) and (B) are thoroughly mixed to form a uniform and homogeneous reactive adhesive formulation. The components comprising the A-side and B-side components can be mixed together by any known adhesive mixing method and equipment.

[0083] The unique two-component solventless laminating adhesive composition of the present invention has several advantages over previously known solventless adhesive systems. For example, the advantageous properties exhibited by the unique two-component solventless laminating adhesive composition of the present invention include (1) long pot life, (2) fast bonding, (3) fast cure, (4) good adhesion performance (bond strength) to a variety of substrates, including metal or metallized substrates and polymeric barrier substrates, (5) fast bond strength development, (6) good chemical resistance, (7) good heat / temperature resistance, (8) good stability, (9) fast line speeds, and (10) improved conversion efficiency. The unique solventless adhesive composition of the present invention, in turn, is useful in methods for making multilayer laminate structures having various beneficial attributes, as described below in this specification.

[0084] With regard to the pot life of the adhesive composition, for example, because the adhesive composition of the present invention is formulated so that it is applied separately and independently (in two separate adhesive components) to two substrates, which are then combined and the adhesive compositions applied to the substrates are mixed and reacted, the pot life of the resulting two-component solventless laminating adhesive composition is not an issue or a limiting factor because the adhesive composition is mixed and used immediately after combining the two substrates.

[0085] The bond strength properties of the two-component solventless laminating adhesive composition can be, for example, 1 N / 15 mm or greater in one general embodiment, and in another embodiment, in the range of 1 N / 15 mm to 10 N / 15 mm. The bond strength of the two-component solventless laminating adhesive composition can be measured using ASTM method D638. Using an adhesive composition with a bond strength property of less than 1 N / 15 mm compromises the durability of the final package prepared using the adhesive composition. Adhesive compositions with a bond strength property of greater than 10 N / 15 mm are useful in the present invention.

[0086] The cure kinetics of the two-component solventless laminating adhesive composition, as measured by infrared spectroscopy, can be, for example, in one general embodiment, in the range of 1 to 3 days. Adhesive compositions with as fast a cure kinetics as possible are desirable.

[0087] The chemical and heat resistance of the two-component solventless laminating adhesive composition can be, for example, 1 N / 15 mm or greater in one general embodiment, and in another embodiment, in the range of 1 N / 15 mm to 5 N / 15 mm. The chemical and heat resistance of the two-component solventless laminating adhesive composition is measured by the method described in ASTM D638. If the chemical and heat resistance of the adhesive is less than 1 N / 15 mm, the durability of the final package prepared using the adhesive composition will be impaired. Adhesive compositions having chemical and heat resistances of greater than 5 N / 15 mm are useful in the present invention.

[0088] Formation of laminated structure Generally, the laminated structure of the present invention is produced by applying the adhesive composition of the present invention between a first film substrate and a second film substrate to form an adhesive layer on the inner surface of the first film substrate and the inner surface of the second film substrate, contacting the two substrates with each other through the inner surfaces of the substrates, thereby disposing the adhesive formulation therebetween, and curing the adhesive formulation at a cure temperature sufficient to bond the two substrates together.

[0089] In one preferred embodiment, a method for producing a laminate structure of the present invention includes, for example, (I) providing at least one first substrate; (II) providing at least one second substrate; and (III) providing an adhesive composition comprising the two-component solventless laminating adhesive composition of the present invention. (IV-i) applying a first coating layer of the isocyanate component of the two-component solventless adhesive composition to at least a portion of one surface of a first substrate to form a film layer of the isocyanate component disposed on the first substrate; (IV-ii) applying a second coating layer of the isocyanate-reactive component of the two-component solventless adhesive composition to at least a portion of one surface of a second substrate to form a film layer of the isocyanate-reactive component disposed on the second substrate; and (V) applying a second coating layer of the isocyanate-reactive component of the two-component solventless adhesive composition to at least a portion of one surface of a second substrate to form a film layer of the isocyanate-reactive component disposed on the surface of the first substrate. (VI) contacting a first coating layer of an isocyanate component with a second coating layer of an isocyanate-reactive component disposed on a surface of a second substrate to form a combined uncured adhesive formulation layer comprising the isocyanate component and the isocyanate-reactive component between the first substrate and the second substrate to form a layered laminate structure; and (VI) curing the adhesive formulation layer between the first substrate and the second substrate to attach the first substrate to the second substrate via the cured adhesive to form a bonded laminate structure.

[0090] For example, the applying step of the above method can be performed by applying the isocyanate component of the adhesive composition to one side of a first substrate, e.g., the inner or inner surface of the first substrate layer, without applying the isocyanate component to the outer or outer surface of the first substrate; and by applying the isocyanate-reactive component of the adhesive composition to one side of a second substrate, e.g., the inner or inner surface of the second substrate, without applying the polyol component to the outer or outer surface of the second substrate. The inner surface of the first substrate is then brought into contact with the inner surface of the second substrate, thereby disposing a layer of adhesive formulation between the first and second substrates.

[0091] The present invention contemplates that the isocyanate component (A-side) and the isocyanate-reactive component (B-side) of the solventless adhesive composition of the present invention are compounded separately and stored until it is desired to form a laminate structure. Preferably, the isocyanate component and the isocyanate-reactive component are in a liquid state at 25°C. Even if the components are solid at 25°C, it is acceptable to heat the components to bring them to a liquid state, if necessary. Because the pot life of the adhesive composition is decoupled from the cure method, the A-side and B-side components can be stored separately indefinitely.

[0092] As mentioned above, a laminate including the solventless adhesive composition is formed by separately applying the isocyanate component and the polyol component of the adhesive composition to two different substrates, such as two films. As used herein, a "film" is any structure having one dimension of 0.5 millimeters (mm) or less and two other dimensions of 1 centimeter (cm) or more. A "polymer film" is a film made from a polymer or a mixture of polymers. The composition of a polymer film is typically 80 weight percent (wt%) or more of one or more polymers.

[0093] In one embodiment, a layer of isocyanate component is applied to the surface of a first substrate. Preferably, the thickness of the layer of isocyanate component on the first substrate is 0.5 micrometers (μm) to 2.5 μm. A layer of isocyanate-reactive component is applied to the surface of a second substrate. Preferably, the thickness of the layer of isocyanate-reactive component on the second substrate is 0.5 μm to 2.5 μm. By controlling the thickness of the layer applied to each substrate, the ratio of components can be controlled. In some embodiments, the mixing ratio of isocyanate component to isocyanate-reactive component in the final adhesive composition can be 100:100, 100:90, or 100:80. The adhesive composition is more forgiving than conventional adhesives and can accommodate some coating weight error (e.g., up to about 10% coating weight error).

[0094] The surfaces of the first and second substrates are then passed through a device, such as a nip roller, for applying external pressure to the first and second substrates. The isocyanate component and the isocyanate-reactive component are combined to form a curable adhesive mixture layer. When the surfaces of the first and second substrates are combined, the curable adhesive mixture layer has a thickness of 1 to 5 μm. When the first and second substrates are combined and the components come into contact with each other, the isocyanate component and the isocyanate-reactive component begin to mix and react, marking the beginning of the curing process.

[0095] Further mixing and reaction is achieved when the first substrate and the second substrate are passed through various other rollers and finally through a rewind roller. Because each substrate takes a longer or shorter path across each roller than the other substrate, further mixing and reaction occurs as the first substrate and the second substrate pass through the rollers. In this way, the two substrates move relative to each other, mixing the components on each substrate. Such roller arrangements in application devices are commonly known in the art. The curable mixture is then cured or allowed to cure.

[0096] The steps of the method of applying the isocyanate component and the isocyanate-reactive component to the substrate forming the laminate structure are carried out, for example, at a temperature of from room temperature to 80°C in one embodiment, from 30°C to 70°C in another embodiment, and from 40°C to 60°C in yet another embodiment.

[0097] In one general embodiment, the method steps for applying external pressure to the first and second substrates using nip rollers or the like are carried out, for example, at a pressure range of 1.5 bar to 4 bar for the nip rollers and at lay-on roll pressure during rewinding. If the pressure drops below 1.5 bar, the adhesive composition may take longer to crosslink, which may result in cosmetic issues in the final reel. If the pressure exceeds 4 bar, cosmetic issues may occur, and cosmetic issues unrelated to the adhesive composition, such as increased curl in the lamination, may be observed in the final reel.

[0098] In one general embodiment, the curing step of the method of forming the laminate structure is carried out at a curing temperature of, for example, room temperature to 60° C., and the curing time of the adhesive formulation can be for a period of 1 to 3 days.

[0099] Laminated structure In a broad embodiment, the laminate structure of the present invention comprises a combination of at least two film layer substrates adhered or bonded together by an adhesive formulation layer formed between the two substrates using the adhesive formulation and application method of the present invention. For example, the laminate product comprises: (a) a first film substrate; (b) a second film substrate; and (c) a layer of the adhesive formulation described above to bond the first and second film substrates, layers (a) and (b). If desired, one or more other optional film substrates may be used to produce a multilayer laminate structure.

[0100] Generally, suitable substrates for laminate structures include, but are not limited to, films, such as polyolefin-based films, polyamide-based films, ethylene vinyl alcohol-based films, polyethylene terephthalate films, metallized films, and metal substrates. Some films optionally have a surface on which an image is printed with an ink that can contact the adhesive composition. The substrates are layered to form a laminate structure using the solventless adhesive composition according to the present invention, which bonds two or more of the substrates together.

[0101] Materials used for the first film substrate layer, component (a), can include, for example, printed polyester, printed polypropylene, nylon, metallized polyester, metallized polypropylene, foil, polyethylene, paper, and the like, and mixtures thereof. In a preferred embodiment, the first layer material can include, for example, printed polyester, printed polypropylene, and mixtures thereof.

[0102] The thickness of the first film layer used to form the recyclable multi-layer laminate product of the present invention may be, for example, from 7 μm to 300 μm in one general embodiment.

[0103] Materials used for the second film layer, component (b), can include, for example, polyethylene, polyethylene-EVOH-polyethylene, metallized polyester, metallized polypropylene, nylon, foil, paper, etc., and mixtures thereof. In a preferred embodiment, the material for the second film layer can include, for example, polyethylene, polyethylene-EVOH-polyethylene, and mixtures thereof.

[0104] The thickness of the second film layer used to form the recyclable multi-layer laminate product of the present invention may be, for example, from 7 μm to 300 μm in one general embodiment.

[0105] Component (c), the two-component solventless adhesive composition of the present invention described above, is used to bond the first and second film layers, components (a) and (b), respectively.

[0106] The thickness of the adhesive layer used to bond the first and second layers together to form the multi-layer laminate product of the present invention may be, for example, from 1 μm to 5 μm in one general embodiment, and from 1.5 μm to 3 μm in another embodiment.

[0107] Additional film substrates other than the first and second film layers are optional and can be used to create a multilayer laminate structure as needed. In addition, one or more of the film substrates can optionally contain a barrier coating on at least one surface of the film substrate. For example, the optional barrier coating can include AlOx, SiOx, and mixtures thereof.

[0108] As described above, the solvent-free adhesive composition and the method of applying such a solvent-free adhesive composition to a substrate provide fast cure / fast bonding of the formed laminate after lamination, thereby improving conversion efficiency and reducing costs. Furthermore, the adhesive composition of the present invention provides high operating line speeds on various laminate structures. For example, the adhesive composition of the present invention provides laminate structures with improved conversion efficiency, particularly when used in laminate structures having (1) metal and / or metallized substrates therein, such as metallized PET film, aluminum film, etc., and (2) polymer barrier substrates therein, such as polyethylene ("PE") film, polyamide ("PA") film, ethylene vinyl alcohol ("EVOH") film, etc.

[0109] Some of the advantageous properties exhibited by the resulting laminate structures produced using the two-component solventless laminating adhesive composition according to the above-described method of the present invention can include, for example, (1) high operating line speeds on structures containing good barrier films, (2) either (a) no levels of aromatic amine migration or (b) very low levels of aromatic amine migration, (3) good adhesion performance (bond strength) to a variety of substrates, such as metal or metallized substrates and polymeric barrier substrates, (4) good chemical resistance, and (5) good heat / temperature resistance.

[0110] The high operating line speed of the laminate structure can be, for example, 60 m / min or more in one general embodiment, and in another embodiment, 60 m / min to 450 m / min. The high operating line speed of the laminate structure can be determined by measuring the readings on the laminator's electronics, and is based on how fast the laminate structure using the adhesive of the present invention can be run without observing any laminate appearance issues (i.e., scratches on the laminate) at the final reel of the lamination process, and whether "misting" is present on the application roller of the lamination process.

[0111] The amine migration properties of the laminated structure, which exhibits no or very low aromatic amine migration from the adhesive, can range, for example, in one general embodiment, from 0 to less than 10 parts per billion (ppb). The absence or very low aromatic amine migration of the laminated structure can be measured by conventional liquid chromatography-mass spectrometry (LC-MS).

[0112] The two-component solventless adhesive composition of the present invention is used to produce a laminate structure, which is then used to produce a multi-layer laminate article or product. For example, the adhesive composition of the present invention is advantageously suitable for use in packaging applications such as high-performance food packaging applications (e.g., boil-in-bag applications). In addition, the adhesive composition of the present invention can be used in applications for producing articles such as hot-fill pouches, wet wipes, coffee packaging, detergent packaging, and pet food packaging. [Example]

[0113] The following examples are presented to further illustrate the invention, but should not be construed as limiting the scope of the claims. Unless otherwise indicated, all parts and percentages are by weight.

[0114] The various materials used in the inventive examples (Inv. Ex.) and comparative examples (Comp. Ex.) are set forth in Table I below.

[0115] [Table 1]

[0116] Preparation of phosphate ester polyols 55.1 grams (g) of VORANOL™ CP-450 and 1.5 g of polyphosphoric acid are added to a reactor at room temperature under a nitrogen (N2) purge. The reactor temperature is then set to 100°C, and the reactor contents are stirred for 1 hour (hr). The reactor temperature is then reduced to 50°C, and 18.4 g of ISONATE™ 125M is introduced into the reactor. The reactor temperature rises to 80°C due to an exothermic reaction. The reaction temperature is controlled at 78°C for 2 hours. The resulting phosphate ester polyol has an OH# of 293 mg KOH / g as measured in accordance with ASTM D4274 and a viscosity of 18,000 mPa.s at 25°C as measured in accordance with ASTM D2196.

[0117] Preparation of polyurethane polyol 850 g of VORANOL™ CP-755 is added to a reactor at room temperature under a nitrogen (N2) purge. The reactor temperature is then set to 40°C. After the reactor temperature reaches 40°C, 150 g of ISONATE™ 125M is charged to the reactor. The reactor temperature increases due to an exothermic reaction. After the reactor temperature stabilizes, the reactor temperature is set to 70°C. The reaction temperature is controlled at 70°C for 3 hours. The resulting polyurethane polyol has an OH# of 135 mg KOH / g, as measured according to ASTM D4274, and a viscosity of approximately 53,000 mPa.s at 25°C, as measured according to ASTM D2196.

[0118] Preparation of the isocyanate component (component A). For the isocyanate components of Inv.Ex.1-4, the appropriate components are listed in Table II. Using the isocyanate component of Inv.Ex.1 as a typical example for sample preparation, approximately 40 g of MOR-FREE™ C33 and approximately 960 g of MOR-FREE™ L75-100 are placed in a glass reactor. The reactor is heated to approximately 40°C, and the resulting mixture in the reactor is stirred at 40°C for approximately 30 minutes. The resulting sample is then removed from the reactor and packaged for later use.

[0119] Preparation of the Isocyanate-Reactive Component (Component B) Suitable components of the isocyanate-reactive components of Inv.Ex.1-4 are detailed in Table II. Using the isocyanate-reactive component of Inv.Ex.1 as a representative example of sample preparation, approximately 750 g of polyurethane polyol, approximately 510 g of ADCOTE™ 113-7, approximately 60 g of phosphate ester polyol, and approximately 180 g of SPECFLEX™ ACTIV 2306 are placed in a glass reactor. The reactor is heated to approximately 60°C, and the resulting mixture in the reactor is stirred for approximately 30 minutes while maintaining the temperature at approximately 60°C. The resulting sample is then removed from the reactor and packaged for later use.

[0120] Preparation of Coreactant A and Coreactant B BESTER™ 648, VORANOL™ CP755, and ISONATE™ 125M are first reacted in a mixing ratio of 14.83:50.75:9.40 by weight in a reactor under a N2 purge at 70°C for 3 hours to form a hydroxyl (OH) terminated component. 75 parts (pts) of the synthesized OH terminated component are then blended with 14.8 pts IP 9001 and 10.2 pts SPECFLEX™ ACTIV 2306 at 60°C for 1 hour to form coreactant A.

[0121] 99.8 pts of coreactant A is blended with 0.2 pts of DC 163 at 60° C. for 1 hour to form coreactant B. Parts (pts) listed in this preparation are by weight.

[0122] [Table 2]

[0123] General Procedure for Preparing Laminates Table III lists the various films used in the examples to prepare laminates and laminate samples using the adhesive formulations described in Table II above. Laminates based on the adhesives of the present invention, Inv. Exs. 1-4 and Comp. Exs. A and B, were produced using a Nordmeccanica Duplex One Shot laminator. The isocyanate component ("Composition A" in Table II) was coated onto the surface of a first substrate, and the isocyanate-reactive component ("Composition B" in Table II) was applied to the surface of a second substrate. The two coated substrates were then combined to form a laminate in the nipping station of the laminator. The coat weight of each laminate was approximately 1.6 grams per square meter (g / m 2 The metering, application, and nip temperatures were 45°C, 50°C, and 60°C, respectively.

[0124] Laminates based on the comparative adhesive Comp.Ex.C were prepared using a Nordmeccanica Super Combi 3000 laminator. The isocyanate component and the isocyanate-reactive component of the comparative adhesive formulation were first mixed together using a metering mix pump. The resulting adhesive mixture was then coated onto the surface of a primary substrate to form a coated web on the primary substrate, and the coated web was then nipped with a secondary substrate in the nipping station of the laminator to form a laminate. The coat weight of each laminate was approximately 1.6 g / m. 2 was maintained.

[0125] [Table 3]

[0126] Film testing and measurement methods Bond strength measurement 90° T-peel tests were performed on laminate samples cut into 15 mm wide strips and pulled on a 15 mm long strip at a speed of 4 inches per minute (10 centimeters per minute) in a Thwing Albert™ QC-3A peel tester equipped with a 50 Newton (N) load cell. Three separate sample strips were tested, and the test values obtained for the three strips were averaged. During the peel test, the average force during pulling was recorded when the two bonded films of the laminate sample separated (peeled). If one of the films stretched or broke, the maximum force or force at break was recorded. The failure mode (FM) or mode of failure (MOF) was recorded according to the following designations: "FS" stands for "film stretch." "FT" means "film tear" (or "break"). "DL" stands for "delamination" and means that the secondary film has separated from the primary film. "AT" stands for "adhesive transfer" and means that the adhesive fails to adhere to the primary film and transfers to the secondary film. "AS" stands for "adhesive split" (or cohesive failure) and means that adhesive is found on both the primary and secondary films. "MT" stands for "metal transfer" and means that transfer of metal from the metallized film to the secondary film has occurred. "PMT" means "partial metal transfer."

[0127] The initial or "green" bond was tested as soon as possible after the laminate was made. Additional T-peel tests were performed at the time intervals listed in Table IV below.

[0128] Boil-in-Bag Test Procedure One of the 9-inch by 12-inch (23 cm by 30.5 cm) PE sheets of the laminate was folded so that the PE film of one layer was in contact with the PE film of the other layer, resulting in a double-layered sheet member with dimensions of approximately 9 inches by 6 inches (23 cm by 15.25 cm). The edges of the double-layered sheet member were trimmed with a paper cutter to obtain a folded piece of approximately 5 inches by 7 inches (12.7 cm by 17.8 cm). The two long sides and one short side of the folded piece were heat-sealed at the edges to obtain a finished pouch with an internal size of 10.2 cm by 15.2 cm (4 inches by 6 inches). The heat sealing was performed at 177°C (350°F) for 1 second with an oil pressure of 276 kilopascals (kpa) (40 pounds per square inch [PSI]). Two or three pouch samples were prepared for each test.

[0129] The pouches were filled through the open end with approximately 100 milliliters (mL) of 1:1:1 sauce (a blend of equal parts by weight of ketchup, vinegar, and vegetable oil). Splashing of the fill onto the heat-seal area was avoided, as this could cause heat-seal failure during testing. After the pouches were filled with sauce, the tops of the pouches were sealed in a manner that minimized the entrapment of air inside the pouches.

[0130] The pouches were visually inspected on all four sides for seal integrity to ensure there were no flaws in the seal that would cause the pouch to leak during testing. Any pouches suspected of having flaws were discarded and replaced with another pouch for testing. In some cases, the suspect pouch was not replaced with another pouch, but the flaws in the laminate were marked to identify if any new, additional flaws occurred during testing.

[0131] A pot was filled 2 / 3 with water and brought to a boil. The boiling pot was covered to minimize water and steam loss. The pot was visually inspected throughout the test to ensure there was enough water to maintain a boil. The pouch was placed in the pot of boiling water and held in the pot / boiling water for 30 minutes. The pouch was removed from the pot / boiling water and visually inspected for damage to the pouch. The severity of damage, e.g., tunneling, blistering, delamination, or leakage, was compared to any existing damage that was marked. Any damage observed was recorded. The pouch was then cut open, emptied, and rinsed with soap and water. One or more 15 mm strips were cut from the pouch, and the laminate bond strength of each of the cut strips was measured according to the standard bond strength test using the bond strength measurement procedure described above. The bond strength test was performed as soon as possible after the pouch contents were removed from the pouch. The interior of the pouch was visually inspected, and any other visual defects observed were noted.

[0132] Laminate appearance evaluation After the laminate was produced, the appearance of the laminate was visually inspected, and the maximum lamination speed for the laminated structure was determined when the laminate showed no visual defects such as bubbles and orange peel.

[0133] [Table 4]

[0134] [Table 5]

[0135] As shown in Tables IV and V, compared to Comp. Ex. F, the solvent-free adhesive of the present invention allows for faster cure / faster bonding of the formed laminate after lamination, with bond strengths of greater than 0.8 Newtons per 15 millimeters (N / 15 mm) at 90 minutes, thus improving conversion efficiency and reducing costs. The adhesive exhibits excellent chemical and temperature resistance, demonstrating bond strengths of greater than 1.5 N / 15 mm after a 1-hour boil-in-bag 1:1:1 source test, compared to the delamination failure mode of Comp. Ex. D and E solvent-free adhesive laminated products. Furthermore, the solvent-free adhesive of the present invention allows for higher operational lamination speeds with good appearance.

[0136] Other embodiments A two-component solventless adhesive composition comprising a prepolymer isocyanate, wherein the isocyanate monomer for preparing the prepolymer isocyanate is selected from the group consisting of one or more of methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate.

[0137] A two-component solventless adhesive composition comprising an amine-initiated polyol, the amine-initiated polyol having a functionality of 2 to 12, a hydroxyl number of 5 to 1,830, and a viscosity of 500 mPa.s to 40,000 mPa.s at 25°C.

[0138] A two-component solventless adhesive composition, wherein the weight ratio of isocyanate component to isocyanate-reactive component is from 0.5:1 to 1.5:1.

[0139] A two-component solventless adhesive composition further comprising tackifiers, plasticizers, rheology modifiers, other adhesion promoters, antioxidants, fillers, colorants, surfactants, and combinations of two or more thereof.

[0140] A laminate structure that exhibits a good appearance when measured / determined by visual observation, with no bubbles formed on the laminate and no orange peel formed on the laminate.

Claims

1. 1. A two-component solventless adhesive composition comprising: (A) at least one isocyanate component formulated for application to a first substrate, the at least one isocyanate being at least one aromatic isocyanate; or (Ai) at least one aromatic isocyanate, and (Aii) at least one isocyanate component comprising any of a blend of at least one aliphatic isocyanate; (B) at least one isocyanate-reactive component formulated for application to a second substrate, (Bi) at least one amine-initiated polyol comprising a backbone incorporating two or more primary hydroxyl groups and a tertiary amine; (Bii) at least one hydroxyl-terminated polyurethane polyol; (Biii) at least one phosphate ester polyol; (Biv) at least one polyester polyol; (Bv) at least one polyether polyol, and (Bvi) at least one isocyanate-reactive component comprising a blend of optionally at least one silane adhesion promoter.

2. the isocyanate-reactive component (B) comprises, based on the total weight of the isocyanate-reactive components: (Bi) 0.5% to 30% by weight of at least one amine-initiated polyol comprising a backbone incorporating two or more primary hydroxyl groups and a tertiary amine; (Bii) 10% to 85% by weight of at least one hydroxyl-terminated polyurethane polyol; (Biii) 0.5% to 40% by weight of at least one phosphate ester polyol; (Biv) 0.5% to 50% by weight of at least one polyester polyol; (Bv) 1% to 30% by weight of at least one polyether polyol, and (Bvi) 0% to 5% by weight of at least one silane adhesion promoter.

3. 10. The two-component solventless adhesive composition of claim 1, wherein the isocyanate component comprises two or more components selected from the group consisting of monomeric isocyanates, polymeric isocyanates, and prepolymeric isocyanates.

4. 10. The two-component solventless adhesive composition of claim 1, wherein the amine-initiated polyol is the reaction product of an alkylene oxide and an amine.

5. 10. The two-component solventless adhesive composition of claim 1, wherein the amine-initiated polyol comprises a compound containing a tertiary amine or a secondary amine.

6. 2. The two-component solventless adhesive composition of claim 1, wherein the at least one hydroxyl-terminated polyurethane polyol is a polyol selected from the group consisting of: (1) a reaction product of a polyether polyol with an aromatic isocyanate monomer; (2) a reaction product of a polyether polyol and / or an aliphatic polyester polyol with an aromatic isocyanate monomer; and (3) mixtures thereof.

7. The at least one phosphate ester polyol has the following chemical structure of structure (II): 【Chemical 1】 [In the formula, R １ The two-component solventless adhesive composition according to claim 1, wherein the polyol compound has the formula:

8. 2. The two-component solventless adhesive composition of claim 1, wherein the at least one polyester polyol comprises a polyol made with diacids and diols selected from the group consisting of neopentyl glycol, 2-methylpropylene diol, hexanediol, butanediol, propylene glycol, ethylene glycol, diethylene glycol, other alkylene diols having 6 to 16 carbon atoms in the backbone; adipic acid, azelaic acid, sebacic acid, and mixtures thereof.

9. 2. The two-component solventless adhesive composition of claim 1, wherein the at least one silane adhesion promoter is an aminosilane adhesion promoter selected from the group consisting of gamma-aminopropyltriethoxysilane, gamma-aminopropyl-trimethoxysilane, N-beta(aminoethyl)-gamma-aminopropyltrimethoxysilane, N-beta(aminoethyl)-gamma-aminopropyltrimethyldimethoxysilane, N-phenyl-gamma-aminopropyltrimethoxysilane, and mixtures thereof.

10. 10. The two-component solventless adhesive composition of claim 1, wherein the adhesive composition has a bond strength of greater than 1 N / 15 mm when a laminate produced using the adhesive composition is cured at 25°C for 90 minutes.

11. 10. The two-component solventless adhesive composition of claim 1, wherein the adhesive composition has less than 10 ppb of primary aromatic amines after being cured at 25°C for up to 3 days.

12. A laminated structure, (a) at least one first substrate layer; (b) at least one second substrate layer; (c) a layer of the two-component solventless adhesive composition of claim 1 disposed between the first substrate layer and the second substrate layer, thereby bonding the first substrate layer to the second substrate layer.

13. 1. A method for making a laminate structure, comprising: (I) providing at least one first substrate; (II) providing at least one second substrate; (III) preparing an adhesive composition comprising the two-component solventless adhesive composition of claim 1; (IV) applying a first coating layer of the isocyanate component of the two-component solventless adhesive composition to at least a portion of one surface of the first substrate to form a film layer of the isocyanate component disposed on the first substrate; (V) applying a second coating layer of the isocyanate-reactive component of the two-component solventless adhesive composition to at least a portion of one surface of the second substrate to form a film layer of the isocyanate-reactive component disposed on the second substrate; (VI) contacting the first coating layer of the isocyanate component of the first substrate with the second coating layer of the isocyanate-reactive component of the second substrate to form a combined uncured adhesive formulation layer comprising the isocyanate component and the isocyanate-reactive component between the first substrate and the second substrate to form a layered laminate structure; (VII) curing the adhesive formulation layer between the first substrate and the second substrate to attach the first substrate to the second substrate via the cured adhesive to form a bonded laminate structure.

14. 14. The method of claim 13, carried out at an operating line speed of greater than 60 meters / minute to 450 meters / minute.

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