Hardener component for reactive resins

Abstract

The invention is directed to a hardener component for hardening a reactive amino resin and its preparation method. The hardener component comprises a salt formed by an aromatic amine and a first acid, and may further comprise a second acid, a polar solvent and / or additives. The invention also relates to a curable composition comprising a resin component and the present hardener component, which are present in a weight ratio of greater than 1:1. The invention also relates to a composite article comprising a substrate and a cured product of the curable composition of the present invention, and a process for making the same. The composite article includes a wood composite, such as cross- laminated timber, glue-laminated beam or rig mat.

Description

HARDENER COMPONENT FOR REACTIVE RESINS

[0001] This application claims priority to and any benefit of U.S. provisional patent application No. 63 / 689,286, filed August 30, 2024, the content of which is incorporated herein by reference in its entirety.FIELD

[0002] The invention relates to a hardener component for hardening a reactive amino resin, a curable composition comprising the hardener component and a resin component, and a composite article comprising a cured product of the curable composition. The present disclosure also relates to methods for manufacturing the hardener component, the curable composition and the composite article.BACKGROUND

[0003] Amino resins are polymeric condensation products made by reacting formaldehyde with amino functional molecules, such as urea or melamine. Amino resins have found a broad range of applications as coatings or adhesives when combined with an acidic hardener (also referred to as a curing agent or crosslinker), such as formic acid, to form a two-component (2K) curable composition. The curing process of amino resin can be performed at room temperature or at a higher temperature with an energy input (e.g., radio frequency), depending on the application and performance requirements. The cured amino resins are hard, rigid, light-colored (comparing with phenolic-based resins), resistant to water and solvent, and have high mechanical strength, bonding strength and robust application tolerances.

[0004] Amino resins, including urea-fonnaldehyde (UF), melamine-formaldehyde (MF) and their co-condensation resin melamine-urea-formaldehyde (MUF), are widely used as adhesives in the wood industry for the preparation of wood composites. For instance, in the manufacturing of glued laminated beams (glulam), a resin component comprising MF is mixed in a specific weight ratio with a hardener component comprising formic acid, and then spread onto the surface of planed lumber. The lumber is stacked in a pattern and pressed together. The resin is cured at room temperature (ambient curing) after, for example, about 24 hours, but may cure more quickly if a radio frequency (RF) is used (RF curing).

[0005] To improve water-resistance of the cured resin, resorcinol is often included in the hardener component. However, the inclusion of resorcinol tends to increase the curing time. Even though RF curing can be used to shorten curing time, it will greatly increase production cost, energy usage and complexity. Therefore, a need exists for an amino resin-based curing system with a high curing speed at ambient temperature and at the same time can result in a cured product of high performance.SUMMARY

[0006] The following is a brief summary of subject matter that is described in greater detail herein. This summary is not intended to be limiting as to the scope of the claims.

[0007] The invention is directed to a hardener component for hardening a reactive amino resin of a curable composition, comprising a salt formed by an aromatic amine and a first acid. The aromatic amine has a chemical structure of:wherein Ri represents -OH or -NH2, R2represents a C1-C3alkyl, and n=0 or 1. Tire aromatic amine may comprise an aminophenol (such as 2-aminophenol, 3 -aminophenol, 4-aminophenol), m- phenylenediamine, p-phenylenediamine, 2,4-diaminophenol, or combination thereof. The first acid may be selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, phosphoric acid, nitric acid, perchloric acid, persulphuric acid, formic acid, acetic acid, maleic acid, propionic acid, butyric acid, iso-butyric acid, hydroxyacetic acid, 2-hydroxypropanoic acid, 3-hydroxypropanoic acid, hydroxybutanoic acid, 2,3- dihydroxypropanoic acid, citric acid, oxalic acid, malonic acid, fumaric acid, acrylic acid, methacrylic acid, para-toluene sulfonic acid, methyl sulfonic acid, and combinations thereof. Preferably, the first acid is sulfuric acid, hydrochloric acid, phosphoric acid, or formic acid. More preferably, the first acid is sulfuric acid. The hardener component is in a liquid form or a solid form.

[0008] The hardener component may further comprise a second acid. The second acid may comprise one or more acids selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, phosphoric acid, nitric acid, perchloric acid, persulphuric acid, formic acid, acetic acid, maleic acid, propionic acid, butyric acid, iso-butyric acid, hydroxyacetic acid, 2-hydroxypropanoic acid, 3-hydroxypropanoic acid, hydroxybutanoic acid, 2,3-dihydroxypropanoic acid, citric acid, oxalic acid, malonic acid, fumaric acid, acrylic acid, methacrylic acid, para-toluene sulfonic acid and methyl sulfonic acid. Preferably, the second acid comprises formic acid. More preferably, the second acid is formic acid.

[0009] The hardener component may further comprise a polar solvent, such as water. The hardener component may further comprise one or more additives selected from the group consisting of non-polar solvent, defoamer, viscosity modifier, rheology modifier, formaldehyde scavenger, plasticizer, filler, flame retardant, lubricant, softening agent, pigment, biocide, latent acid donor, surfactant, dispersant, latex, and hydrophobic agent. The hardener component may be substantially free of resorcinol. The hardener component may comprise from 10 wt.% to 40 wt.% of the salt formed by the aromatic amine and the first acid; from 0 wt.% to 40 wt.% of the second acid; from 20 wt.% to 90 wt.% of the polar solvent; and from 0 wt.% to 40 wt.% of the one or more additives. The hardener component may further comprise the first acid which may be present in an amount of from 0.01 wt.% to 20 wt.% based on the total weight of the hardener component.

[0010] The hardener component has a solid content of from 15 wt.% to 60 wt.%. The hardener component has a pH in a range of from - 1 to 4. The hardener component has a viscosity in a range of from 500 cPs to 8,000 cPs, measured by a Brookfield viscometer using #4 spindle at 20 rpm at 25°C.

[0011] The invention is also directed to a method for preparing a hardener component for hardening a reactive amino resin of a curable composition. The method comprises reacting an aromatic amine and a first acid in a polar solvent to obtain a first solution, wherein the stoichiometric ratio of the aromatic amine to the first acid is no greater than 1.0. The stoichiometric ratio of the aromatic amine to the water-soluble acid may be less than 0.8, or less than 0.6. The aromatic amine may have the same chemical structure as disclosed above. In the first solution, preferably, the aromatic amine is completely protonated. The method may further comprise a step of adding a second acid into the first solution. The examples of the first acid and the second acid have been disclosed above. In some aspects, the method uses the following ingredients: from 6wt.% to 22 wt.% of the aromatic amine; from 4 wt.% to 18 wt.% of the first acid; from 0 wt.% to 40 wt.% of the second acid; and from 20 wt.% to 90 wt.% of the polar solvent.

[0012] TThhee iinnvveennttiioonn iiss aallssoo ddiirreecctteedd ttoo a curable composition, comprising a resin component comprising a reactive amino resin and a hardener component according to the present invention, which are present in a weight ratio of greater than 1:1, preferably in a weight ratio of at least 1.5:1, and more preferably in a weight ratio of at least 2:1. The reactive amino resin may comprise melamine-formaldehyde resin, urea-formaldehyde resin, melamine-urea-formaldehyde, or combination thereof. The reactive amino resin may be methylated, methylolated, or, both methylated and methylolated. The reactive amino resin has a weight average molecular weight (Mw) in a range of from 125 Da to 155 Da, preferably from 140 Da to 155 Da, and a polydispersity index (PDI) in a range of from 1.0 to 3.0, measured by gel permeation chromatography. The resin component has a pH in a range of from 7 to 11. The resin component has a solid content of from 50 wt.% to 90 wt.%, and a viscosity in a range of from 500 cPs to 8,000 cPs, measured by a Brookfield viscometer using #4 spindle at 20 rpm at 25°C. In some aspects, the resin component may comprise a methylated melamine-formaldehyde resin which can be prepared by reacting melamine, methanol, and formaldehyde. For example, the methylated melamine-formaldehyde resin may be prepared by reacting melamine, methanol and formaldehyde at a temperature of from 75°C to 80°C and at a pH of from 7.3 to 8.0; and adjusting the pH to greater than 9.5. Alternatively, the methylated melamine-formaldehyde resin may be prepared by a staged addition of formaldehyde method comprising: (1) reacting melamine, methanol and a first part of formaldehyde at a temperature of from 75°C to 80°C and at a pH of from 7.3 to 8.0 to obtain a first resin solution having a dilutability greater than 150%; (2) adding a second part of formaldehyde to the first resin solution and heating to reflux at a temperature of from 75 °C to 80°C and at a pH of from 7.3 to 8.0 to obtain a second resin solution having a dilutability less than 150%; and (3) adjusting the pH of the second resin solution to greater than 9.5. The resin component may further comprise one or more additives selected from the group consisting of non-polar solvent, defoamer, viscosity modifier, rheology modifier, formaldehyde scavenger, plasticizer, filler, flame retardant, lubricant, softening agent, pigment, biocide, latent acid donor, surfactant, dispersant, latex, and hydrophobic agent.

[0013] The invention is also directed to a composite article comprising a cured product of the curable composition of the present invention and a substrate. The substrate may comprise alignocellulose material. The composite article may be a wood composite, such as a cross-laminated timber, a glue-laminated beam, or a rig mat.

[0014] TThhee iinnvveennttiioonn iiss aallssoo ddiirreecctteedd ttoo a process for making a composite article, comprising: providing a curable composition of the present invention; applying the curable composition on a substrate; and curing the curable composition. The applying of the curable composition may be conducted by coating a surface of the substrate with the curable composition in a spread rate of from 40 lbs to 110 lbs / 1000ft2, or by blending the curable composition with the substrate in a weight ratio of from 1:100 to 50:100. The process may further comprise a step of consolidating the substrate by applying pressure or extrusion. The curing of the curable composition may occur at a temperature of from 15°C to 35°C, or at a temperature of from 35°C to 100°C. The curing of the curable composition may occur under a radio frequency (RF) treatment. The substrate may comprise a lignocellulose material. The composite article may be a wood composite, such as a cross-laminated timber, a glue-laminated beam, or a rig mat.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The general inventive concepts, as well as illustrative embodiments and advantages thereof, are described below in greater detail, by way of example, with reference to the drawings in which:

[0016] Fig. 1 illustrates GPC curves of resin component EcoBind™ 6500 and E2-1 prepared in Example 2.

[0017] Fig. 2 illustrates steady shear gel curves of curable composition samples of Example3.

[0018] Fig. 3 illustrates storage modulus and loss modulus test results of curable composition samples of Example 3.

[0019] Fig. 4 illustrates steady shear gel curves of curable composition samples of Example4.

[0020] Fig. 5 illustrates NMR spectrums of two hardener components El-1 and El-5.

[0021] Fig. 6 illustrates steady shear gel curves of curable composition samples of Example5.

[0022] Fig. 7 illustrates steady shear gel curves of curable composition samples of Example6.

[0023] Fig. 8 illustrates storage modulus and loss modulus testing results of curable composition samples of Example 6.

[0024] Figs. 9 (a) and (b) illustrate the breaking loads over time of two glulam beams samples made from curable composition samples CE1 and E3-3 of Example 7.

[0025] Figs. 10 (a) and (b) illustrate the breaking loads over time of two glulam beams samples made from curable composition samples CE2 and E3-4 of Example 7.

[0026] Fig. 1 1 illustrates steady shear gel curves of curable composition samples ofExample 8.

[0027] Fig. 12 illustrates steady shear gel curves of curable composition samples ofExample 9.

[0028] Fig. 13 illustrates steady shear gel curves of curable composition samples ofExample 11.DETAILED DESCRIPTION

[0029] The invention is directed to a hardener component for hardening a reactive amino resin of a curable composition, the curable composition and methods for manufacturing thereof. The curable composition can be used to manufacture composite articles, and therefore, the invention further relates to a composite article comprising a cured product of the curable composition, as well as a process for manufacturing the composite article using the curable composition disclosed herein. While the following disclosure describes certain aspects of the hardener component, methods of manufacturing, the two-component curable composition, and composite articles in detail, the present disclosure is to be considered exemplary and is not intended to be limited to the disclosed aspects.Hardener Component

[0030] As used herein, a “hardener component” is defined as a separate ingredient comprising a hardener that functions initiate the cross-linking reaction of a reactive resin in a resincomponent of a two-component or multiple-component curable composition. A “hardener” may also be referred to as a curing agent, crosslinking agent, or catalyst. The cross-linking reaction may occur through the reaction between the hardener and the reactive resin, or through self-crosslinking of the reactive resin in the presence of the hardener. Before mixing, the hardener component and the resin component are stored separately. The cross-linking reaction occurs upon mixing and the reactive resin cures to form a cured product. As used herein, “cure”, “curing”, “cured” and similar terms are intended to embody the structural change that occurs in the reactive resin. The curing speed depends on the cross-linking speed. The performance and properties of the cured product usually depend on the structure of the resin and the crosslink density.

[0031] The hardener component of the invention is used to harden a reactive amino resin of a curable composition. The hardener component comprises a salt formed by an aromatic amine and a first acid. In some aspects, the hardener component is present in a liquid form comprising the salt with a liquid carrier (e.g., a polar solvent). In some other aspects, the hardener component is present in a solid form (e.g., particle or powder) comprising the salt without a liquid carrier.

[0032] Any aromatic amine may be used in the present invention, provided that it can be solubilized or protonated in an aqueous acidic solution. The ability of the aromatic amine to be solubilized or protonated in an aqueous acidic solution ensures effective formation of the hardener salt and compatibility with the curable resin. The aromatic amine has a chemical structure of:wherein Ri represents -OH or -NH2, and R2represents C1-C3alkyl, n=0 or 1. Examples of the aromatic amine include, for example, aminophenols (e.g., 2-aminophenol, 3 -aminophenol, 4- aminophenol), phenylenediamines (e.g., m-phenylenediamine, p-phenylenediamine), and other compounds such as 2,4-diaminophenol.

[0033] A first acid used to form the salt may comprise a mineral acid or an organic acid. As used herein, the term “mineral acid” includes an acid derived from inorganic compound, andmay also be referred to as an inorganic acid. When dissolved in water, the mineral acid dissociates to produce hydrogen ions (H+). Examples of mineral acids include sulfuric acid, sulfurous acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, phosphoric acid, nitric acid, perchloric acid, persulphuric acid, and the like. As opposed to mineral acid, an “organic acid” is an acidic organic compound. The organic acid used herein is also able to produce hydrogen ions (H+) when dissolved in water. Examples of organic acid include formic acid, acetic acid, maleic acid, propionic acid (or propanoic acid), butyric acid, iso-butyric acid, hydroxyacetic acid, 2-hydroxypropanoic acid, 3- hydroxypropanoic acid, hydroxybutanoic acid, 2,3-dihydroxypropanoic acid, citric acid, oxalic acid, malonic acid, fumaric acid, acrylic acid, methacrylic acid, para-toluene sulfonic acid and methyl sulfonic acid and the like. In some aspects, the first acid is able to fully solubilize the aromatic amine in water. Preferably, the salt in the hardener component is formed from sulfuric acid, hydrochloric acid, or formic acid. More preferably, the salt is formed from sulfuric acid. The sulfuric salt of aromatic amine is stable in water solution.

[0034] The salt formed by an aromatic amine and first acid may be included in the hardener component in an amount from 10 wt.% to 40 wt.%, based on the total weight of the hardener component. For instance, the salt formed by an aromatic amine and first acid may be included in the hardener component in an amount from 12 wt.% to 38 wt.%, 13 wt.% to 35 wt.%, 14 wt.% to 30 wt.%, or 15 wt.% to 25 wt.%, including all endpoints and subranges therebetween.

[0035] In some aspects, the hardener component of the present application further comprises a second acid. The second acid is also a mineral acid or an organic acid. The second acid may include one or more acids selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, phosphoric acid, nitric acid, perchloric acid, persulphuric acid, formic acid, acetic acid, maleic acid, propionic acid (or propanoic acid), butyric acid, iso-butyric acid, hydroxyacetic acid, 2-hydroxypropanoic acid, 3-hydroxypropanoic acid, hydroxybutanoic acid, 2,3-dihydroxypropanoic acid, citric acid, oxalic acid, malonic acid, fumaric acid, acrylic acid, methacrylic acid, para-toluene sulfonic acid and methyl sulfonic acid. In some aspects, the second acid is formic acid. The second acid may be the same as the first acid (such as both the first acid and the second acid are formic acid), and also can be different from the first acid (such as the first acid is sulfuric acid, the second acid is formic acid).

[0036] If present, the second acid may be included in the hardener component in an amount from 0.25 wt.% to 40 wt.%, based on the total weight of the hardener component. For instance, thesecond acid may be included in the hardener component in an amount from 0.5 wt.% to 35 wt.%, 1 wt.% to 30 wt.%, 2.5 wt.% to 25 wt.%, or 5 wt.% to 20 wt.%, including all endpoints and subranges therebetween. Usually, an acid is used in the form of an aqueous solution having a determined concentration (e.g., a 97.6% formic acid aqueous solution, a 96.9% sulfuric acid aqueous solution). Unless otherwise indicated, the wt.% (weight percentage) of acid used in the present application refers to the amount of the acid substance, rather than the amount of an acid solution. In other words, the wt.% of an acid is calculated based on 100% of the acid.

[0037] The hardener component may comprise a polar solvent, such as water, ethanol, methanol, glycerol, cyrene, levoglucosenone, dipropylene glycol dibenzoate, diethylene glycol dibenzoate and combinations thereof. Preferably, the polar solvent is water.

[0038] The polar solvent is included in the hardener component in an amount from 20 wt.% to 90 wt.%, based on the total weight of the hardener component. For instance, the polar solvent may be included in the hardener component in an amount from 25 wt.% to 85 wt.%, 30 wt.% to 80 wt.%, 35 wt.% to 75 wt.%, or 40 wt.% to 65 wt.%, including all endpoints and subranges therebetween.

[0039] The hardener component may further comprise at least one additive selected from the group consisting of a non-polar solvent, defoamer, viscosity modifier, rheology modifier, formaldehyde scavenger, plasticizer, filler, flame retardant, lubricant, softening agent, pigment, biocide, latent acid donor, surfactant, dispersant, latex, hydrophobic agent, and the like and mixtures thereof.

[0040] The hardener component of the present disclosure may comprise, based on the total weight of the hardener component, from 10 wt.% to 40 wt.% of the salt formed by an aromatic amine and a first acid; from 0 wt.% to 40 wt.% of the second acid; from 20 wt.% to 90 wt.% of the polar solvent; and from 0 wt.% to 40 wt.% of additives. In some instances, the hardener component includes unreacted first acid when, for example, an excess amount of the first acid is used to prepare the salt of aromatic amine. When such excess first acid is present in the hardener component, the first acid is present in an amount from 0.01 wt.% to 20 wt.%, including, for example, from 0.05 wt.% to 15 wt.%, from 0.1 wt.% to 10 wt.%, from 0.5 wt.% to 8 wt.%, or from 0.5 wt.% to 5 wt.%, including all endpoints and subranges therebetween.

[0041] The hardener component may be substantially free of resorcinol. As mentioned above, although the inclusion of resorcinol may improve water-resistance of the cured product, it also tends to reduce the curing speed. Accordingly, the hardener is preferably free or substantially free (i.e., less than 1 wt.%) of resorcinol. However, the hardener component may optionally comprise a certain amount of resorcinol, such as, for example, no greater than 20 wt.% of resorcinol, or no greater than 10 wt.% of resorcinol based on the total weight of the hardener component.

[0042] The hardener component is acidic and may have a pH in a range of from less than0 (i.e., negative pH value) to 4, including, for example, from -1 to 4, from -0.5 to 4, from 0 to 4, from -1 to 3, from -0.5 to 3, from 0 to 3, or from 0 to 2.

[0043] The hardener component is in the form of a liquid solution, with a solids content of from 15 wt.% to 60 wt.%, such as, for example, from 20 wt.% to 55 wt.%, or from 25 wt.% to 50 wt.%. As used herein, the solids content of a composition is measured by the weight loss upon heating of a small, e.g., about 1 to about 5 grams, sample of the composition at about 125°C for 1.75 hours. The hardener component has a viscosity in a range of from 500 cPs to 8,000 cPs, measured by a Brookfield viscometer using #4 spindle at 20 rpm at 25°C. For instance, the viscosity of the hardener component may be from 800 cPs to 6,000 cPs or from 1,000 cPs to 5,000 cPs. The viscosity of the hardener component can be adjusted by, for example, adding a viscosity modifier and / or a rheology modifier.

[0044] The hardener component may be prepared by blending the above disclosed salt, and optional second acid, optional polar solvent, and optional additives. In some aspects, the method for preparing the hardener component comprises a first step of reacting an aromatic amine and a first acid in a polar solvent in a stoichiometric ratio of no greater than 1 to obtain a first solution. The method may further comprise a second step of adding the second acid into the first solution. The stoichiometric ratio of the aromatic amine to the first acid is no greater than 1.0, such as less than 0.8, less than 0.7, or less than 0.6. Preferably, a stoichiometric excess of the first acid is utilized to solubilize the aromatic amine and achieve a high percentage protonation of the aromatic amine. Without wishing to be bound by theory, the presence of a highly or nearly completely protonated aromatic amine in the hardener component can increase the curing speed of a reactive amino resin. In the case where the aromatic amine is completely protonated by the first acid, the hardener component is substantially free (i.e., less than 2%, or less than 1%) of aromatic amine and may further include a presence of unreacted first acid.

[0045] As disclosed above, the first acid may be the same as or may be different from the second acid. The total amount of the first and the second acid present in the hardener component should render the pH of the hardener component in the range of from less than 0 to 4, such as from -1 to 4. The ingredients used to prepare the hardener component may comprise, for example, from 6 wt.% to 22 wt.% of the aromatic amine; from 4 wt.% to 18 wt.% of the first acid; from 0 wt.% to 40 wt.% of the second acid; and from 20 wt.% to 90 wt.% of the polar solvent.Resin Component

[0046] The resin component comprises a reactive amino resin. As used herein, the term “amino resin” refers to condensation products that are made by reacting aldehyde (e.g., formaldehyde) with amino functional molecules (e.g., urea or melamine). The properties of an amino resin can be varied by changing the molar ratio of aldehyde to amino functional molecules. Common amino resins include formaldehyde condensation resins, including melamineformaldehyde (MF) resin, urea-formaldehyde (UF) resin, and melamine-urea-formaldehyde (MUF) resin. The term “reactive amino resin” refers to amino resins having functional groups (e.g., hydroxyl groups) which can be cross-linked under the presence of a hardener or can be cross-linked by reacting with a hardener. In the present invention, the reactive amino resin may be methylated, methylolated, or, both methylated and methylolated. After curing, the reactive amino resin can form hard, rigid, light-colored and water-resistant cured product.

[0047] The reactive amino resin may have a weight average molecular weight (Mw) in a range of from 125 Da to 155 Da, measured by gel permeation chromatography (GPC). Preferably, the resin component comprises a reactive amino resin having a high weight average Mw, such as, for example, a weight average molecular weight in a range of from 140 Da to 155 Da (hereinafter “high Mw amino resin”). The reactive amino resin may have a polydispersity index (PDI) in a range of from 1.0 to 5.0, preferably, from 1.0 to 3.0, as measured by GPC. PDI is calculated as the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn). The molecular weight numbers disclosed in the present application are relative and not absolute and they depend on the running conditions and calibration of a GPC equipment. As disclosed herein, the GPC measurement is conducted on an Agilent 1260 Infinity II LC system equipped with a refractive index (RI) detector using a mobile phase of 0.02M ammonium acetate in dimethyl sulfoxide (DMSO) at a flow rate of 0.65 mL / min. The column set consists of three Agilent PLGel columns (5 μm 100A, 500A, and mixed D). Column temperatures were elevated to 80 °C. The RIdetector was kept at 55°C. The calibration standards are PSS (polysulfonated styrene) with MW ranging from 622000 to 210 Da to create a 3rd order polynomial calibration, recalibrated every 3- 6 months. Two PSS checks (Mw 63900 and 3610) are run with every GPC run.

[0048] Based on GPC measurements, the reactive amino resin has a molecular weight distribution such that at least 80% of the resin comprises large molecules having an elution time in GPC of less than 38 minutes, for example, between 31 and 38 minutes. The reactive amino resin may have a molecular weight distribution such that less than 10% of the resin comprises small molecules having an elution time in GPC of at least 38 minutes, for example, between 31 and 38 minutes. In some aspects, the reactive amino resin has a GPC pattern substantially similar to at least one of the patterns in Figure 1.

[0049] The resin component has a neutral to basic pH, such as a pH in a range of from 7 to 11, including, for example, from 8 to 10.5, from 8.5 to 10, or from 9 to 10.

[0050] The resin component is in the form of a liquid, with a solids content of 50 wt.% to90 wt.%. including, for example, from 55 wt.% to 85 wt.%, or from 60 wt.% to 80 wt.%. The resin component may have a viscosity in a range of from 500 cPs to 8,000 cPs, measured by a Brookfield viscometer using #4 spindle at 20 rpm at 25°C. For instance, the viscosity of the hardener component may be from 800 cPs to 6,000 cPs, from 1,000 cPs to 5,000 cPs, or from 1,500 cPs to 3,500 cPs. The viscosity of the resin component can be adjusted by, for example, changing the wt.% of amino resin, viscosity modifier, and rheology modifier in the resin component.

[0051] The reactive amino resin in the resin component can be prepared by a condensation of formaldehyde and amino functional molecules in a basic environment, such as, in the presence of a basic catalyst, such as sodium hydroxide. For example, a methylated melamine-formaldehyde resin can be prepared by reacting melamine, methanol, and formaldehyde at a pH of from 7.3 to 8.0. In a specific example, a methylated melamine-formaldehyde resin is prepared by reacting melamine, methanol and formaldehyde at a temperature of from 75°C to 80°C and at a pH of from 7.3 to 8.0; and adjusting the pH to greater than 9.5. If a high Mw amino resin is desired, the high Mw amino resin can be prepared by a method including staged addition of formaldehyde. For example, the preparation of high Mw MF resin includes reacting melamine, methanol and a first part of formaldehyde at a temperature of from 75°C to 80°C and at a pH of from 7.3 to 8.0 to obtain a first resin solution having a water dilutability of greater than 150%; adding a second part offormaldehyde to the first resin solution to react at a temperature of from 75°C to 80°C and at a pH of from 7.3 to 8.0 to obtain a second resin solution having a water dilutability less than 150%; and adjusting the pH of the second resin solution to greater than 9.5. The staged addition of formaldehyde can result in an amino resin having a high Mw without broadening its molecular weight distribution. As used herein, the dilutability (%), which is also called “water tolerance”, is defined as the percent quotient of the grams of deionized water over the grams of resin needed to turn the resulting sample mix hazy. The dilutability is tested at 25 °C by adding deionized water to a sample resin slowly under stirring until resin precipitation occurs and the sample solution becomes turbid.

[0052] The resin component may further comprise at least one additive selected from the group consisting of a non-polar solvent, defoamer, viscosity modifier, rheology modifier, formaldehyde scavenger, plasticizer, filler, flame retardant, lubricant, softening agent, pigment, biocide, latent acid donor, surfactant, dispersant, latex, hydrophobic agent, and the like and mixtures thereof.Additional Component(s)

[0053] The curable composition optionally further includes one or more “additional components,” which may include, but are not limited to, polar solvents, non-polar solvents, formaldehyde scavengers, plasticizers, rheology modifiers, fillers, flame retardants, lubricants, softening agents, pigments, biocides, latent acid donors such as acid anhydrides and / or alkyl esters, surfactants, latexes, combinations thereof and a combination comprising one or more of these.

[0054] Exemplary fillers include, but are not limited to, an organic filler, a mineral filler, and combinations thereof. Examples of suitable organic fillers include cellulosic material, organic polymer fibers, such as carbon fiber, biochar, and combinations thereof. Cellulosic materials may include wood or wood byproducts like wood flour, wood fibers, sawdust, wood shavings; paper or lignin products or byproducts; plant materials such as flax, hemp, wheat straw, rice hulls, soy hulls, kenaf, jute, sisal, seed shells (e.g., peanut or walnut shells), other natural fibers; and combinations thereof. Cellulosic material should be understood herein to include lignocellulosic material. Examples of suitable mineral fillers include any solid inorganic material, preferably inorganic particulates or fibers. Such inorganic materials include calcium carbonate (CaCO3), graphite, silicas, silicates, aluminas, aluminates, aluminosilicates, talc, mica, clay, feldspars, diatomaceousearth, fumed silica, amorphous silica, fumed aluminum oxide, sand, wollastonite, carbon black, TiO2, glass fibers, glass beads, glass spheres, mol sieves, ceramic spheres, pigments, and combinations thereof.

[0055] Exemplary formaldehyde scavengers include, for example, ammonium salts, primary amines, melamine, ethylene urea, urea, resorcinol, tannins, and combinations thereof. Exemplary plasticizers include ethylene and propylene glycol oligomers, hydroxyaryl compounds, glycerin esters, gum rosins, sugars, phosphate esters and combinations thereof.

[0056] Exemplary rheological modifiers include, for example, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, attapulgite clays, sepiolite clays, organo-clays, polyvinyl alcohols, starches, xanthan gum, guar gum, molasses, alginate, polyglucans, polyurethane-based rheology modifiers, such as hydrophobically modified ethoxylate urethane compounds (HEUR), hydrophobically modified polyethers (HMPE), and combinations thereof.

[0057] Exemplary flame retardants include, for example, silica, melamine phosphate, melamine borate, pentaerythritol, melamine cyanurate, expandable graphite, pentaerythritol polyphosphate ester, alkyl phosphate esters, trimethyl borate, borate esters, zinc borate, guanylurea phosphate, magnesium oxide, ammonium polyphosphate and combinations thereof.

[0058] Exemplary polar solvents include, for example, water, ethanol, methanol, glycerol,Cyrene, levoglucosenone, dipropylene glycol dibenzoate, diethylene glycol dibenzoate and combinations thereof. Exemplary surfactants include Surfynol 104H, Surfynol 420, Dynol 360, Dynol 980, Carbowet 106, Carbowet 109, Silres BS168, FC-402, free fatty acids, polysiloxanes, polyacrylates, fluorosurfactants and combinations thereof. Exemplary latent acid donors include but are not limited to maleic anhydride, acetic anhydride, trimethyl citrate, triethyl citrate, ammonium sulfate, methyl salicylate, and combinations thereof. In general, the additional components, when used, may be present in an amount that does not affect the desired properties of the adhesive composition.

[0059] The one or more additional components may optionally be present in the curable composition in an amount from 0 to 60 wt.%, such as, for example, from 0.1 wt. % to 50 wt. %, from 0.5 wt.% to 30 wt.%, from 1 wt.% to 25 wt.%, from 3 wt.% to 20 wt.%, from 5 wt.% to 17 wt.%, or from 7 wt.% to 15 wt.%, including all endpoints and subranges therebetween.Curable Composition

[0060] The hardener component, resin component, and optional additional component, whether included as separate components of a package, or pre-blended, may be referred to herein as the curable composition. For example, the curable composition may be a two-component or two-part (2K) system whereby the resin component and hardener component are not pre-blended, but rather are separate components of an overall system (with optional additives in either component). Alternatively, the curable composition may be prepared by blending, mixing, or otherwise combining the resin component, the hardener component, and optional additional component. In some aspects, the resin component and the hardener component, both in liquid form, optionally together with optional additives, are blended or otherwise mixed, to obtain the curable composition of the present application. The curable composition may be ready to use after the blending or mixing.

[0061] The curing speed of the curable composition and the properties of the cured product can be affected by the weight ratio of the resin component to the hardener component. In the curable composition, the resin component and the hardener component may be present in a weight ratio of greater than 1:1. Preferably, the resin component and the hardener component may be present in a higher weight ratio, such as at least 1.1 : 1 , at least 1.2: 1 , at least 1.3:1, at least 1.4: 1 , at least 1.5:1, at least 1.6: 1, at least 1.7:1, at least 1.8:1, at least 1.9: 1, or at least 2:1.

[0062] The curable composition of the present disclosure is useful as coating or adhesives in the plastics, wood, molding, and laminating fields. The use of the curable composition can be carried out by applying the curable composition on a substrate and curing the curable composition. Specifically, the applying of the curable composition on a substrate can be conducted by applying the hardener component, the resin component and optional additional component, without specific order, respectively, or by applying a mixture of the hardener component, the resin component and optional additional component on the substate. The applying can be conducted by any method or tool known in the art, such as coating or spraying. The viscosity of the component or the composition to be applied depends on the applying method. As mentioned above, the viscosity of the component or the composition can be adjusted by adding additives, such as solvent and / or viscosity modifier.

[0063] The curable composition of the present invention is curable at ambient temperature and can reach a green strength within 80 minutes, preferably within 70 min, more preferably within 60 minutes, and even more preferably within 50 minutes or within 40 minutes. As used herein, the ambient temperature is the air temperature of an environment where the curing is conducted, without additional heat-treatment. Usually, the ambient temperature has a range of from 15°C to 35°C, preferably from 20°C to 30°C, and more preferably from 20°C to 25°C. The “green strength” refers to the early development of a curable composition’s bond strength, which allows the cured product to maintain its bond integrity and to be handled (such as being moved to another place) before it is fully cured. Usually, the green strength is significantly lower than the final bond strength.

[0064] It is surprisingly discovered that the use of the hardener component of the present invention can accelerate the curing of a reactive amino resin to obtain a cured product of high performance, including excellent mechanical strength, light color, water and chemical resistance. Furthermore, it is also discovered that when a high Mw reactive amino resin is used, the curing speed can be further improved, without affecting the performance of the cured product.Composite Article

[0065] The curable composition can be used to make a composite article. The composite article comprises a cured product of the curable composition as disclosed herein and a substrate. In particular, the substrate may include a lignocellulose material (i.e., wood particles, wood fibers, straw, hemp, cotton stalk, wheat, bamboo, jute, flax, hard woods, soft woods, grasses, etc.), paper, fiberglass, cellulose, metal, sand, polymer materials, synthetic materials, and the like. When a lignocellulose material is used as substrate, examples of the composite article include oriented strand board (OSB), particleboard, flake board, medium or high-density fiberboard, waferboard, plywood, laminated veneer layer (LVL), laminated glulam beam, mass timber, cross-laminated timber (CLT), rig mat, medium density overlay (MDO), high density overlay (HDO), an overlaid weather barrier, high pressure laminates (HPL), or thermally fused laminates (TFL), and the like. The curable composition is very suitable for making a wood composite, especially structural wood composite, such as laminated glulam beam, cross-laminated timber (CLT) and a rig mat.

[0066] A process for manufacturing the composite article includes the steps of: 1) providing a curable composition including a resin component and a hardener component; 2) applying the curable composition to a substrate; and 3) curing the curable composition. Asdisclosed above, applying the curable composition to the substrate may be conducted by applying the hardener component, the resin component and optional additional component, in any order, or by applying a mixture of the hardener component, the resin component and optional additional component(s) to the substate.

[0067] The curable composition may be applied to a substrate by any method (coating, spraying, and the like) or any tool (such as by blender, roll coater, curtain coater, dip coater, spray booth, extruder, and the like) known in the art. For example, various spraying techniques can be used to apply the curable composition on the substrate. The curable composition applied to the substrate is referred to herein as a coating even though it may be in the form of small resin particles which do not form a continuous layer.

[0068] In some aspects, the composite article comprises a plurality of plates or laminas as substrate. The process for manufacturing the composite article comprises the steps of 1) applying the curable composition to contacting surfaces of the plurality of laminas; 2) consolidating the plurality of laminas by applying pressure; and 3) curing the curable composition. The curable composition may be applied to a surface of the substrate by coating the curable composition on the surface in a spread rate of from 40 Ibs / lOOOft2to 110 lbs / 1000ft2, preferably from 50 lbs / 1000ft2to 100 lbs / 1000ft2. During consolidation of the laminas under pressure, the curable composition is cured, and the laminas are bonded together. As an example, in the manufacturing of a structural wood composite article, such as a laminated glulam beam, several layers of dimensioned lumber with the curable composition applied therebetween are stacked and pressed. The structural wood composite article made from the curable composition of the present application can reach a breaking load of 200 pounds per square inch (PSI) within 80 minutes, preferably within 70 minutes, and more preferably within 60 minutes, measured by a test method AITC T-107 published by American Institute of Timber Construction (AITC).

[0069] In some aspects, the composite article comprises small-piece materials as a substrate, which may be formed by blending the curable composition with the small-piece materials; consolidating the small-piece materials by applying pressure or extrusion; and curing the curable composition. When blending the curable composition with the substrate, it may be conducted in a weight ratio of curable composition to substrate being from 1 : 100 to 50: 100. During the pressing or extrusion, the curable composition is cured, and the small-piece materials are bonded together. In some embodiments, the small-piece materials are small wood pieces whichcan be used to produce fiberboards or particleboards. The blend of small wood pieces and the curable composition can be pressed or extruded through a die to form a flat board.

[0070] The curable composition may be cured at ambient temperature (ambient cure) such as from 15°C to 35°C, or at an elevated temperature such as from 35°C to 100°C. The curing can also occur under an energy input such as radio frequency (RF).

[0071] When the curable composition is used in manufacturing of composite articles, the production efficiency is greatly increased as the curable composition can be cured with a fast speed. Since the fast curing can happen at ambient temperature without an energy input, the energy consumption and product cost are also reduced.EXAMPLES

[0072] The following examples are included for the purposes of illustration and does not limit the scope of the general inventive concepts described herein.Testing Methods

[0073] In the following examples, any reference to pH was measured using a ThermoScientific Orion Star A211 pH meter, after daily 3-point calibration, at 25°C unless otherwise specified.

[0074] The viscosity was measured by a Brookfield viscometer using a #4 spindle at 20 rpm at 25°C.

[0075] The refractive index was measured using a 1257 Automated refractometer by Rudolph Research.

[0076] The density was measured using a calibration certified stainless steel Gardco WG- SS-83.2 / C U.S Standard Weight per gallon cup.

[0077] The dilutability (%) was tested at 25°C by adding deionized water to a sample resin slowly under stirring until resin precipitation occurs and the sample solution becomes turbid. The criteria for determining an end point of adding water is that, through the sample solution, a printed word of 48 font size in bold can be visible but the same word of a smaller font size cannot be visible.

[0078] All rheometry data including steady shear gel curves, storage modulus and loss modulus via oscillatory rheometry were conducted with a Discovery- 1 TA Instrument rheometer using a 40 mm parallel plate and a steel Peltier plate.

[0079] The weight average molecular weight (Mw), PDI and GPC curves were measured by gel permeation chromatography (GPC), which is an Agilent 1260 Infinity II LC system equipped with a refractive index (RI) detector using a mobile phase of 0.02M ammonium acetate in dimethyl sulfoxide (DMSO) at a flow rate of 0.65 mL / min. The column set consists of three Agilent PLGel columns (5 μm 100A, 500A, and mixed D). Column temperatures were elevated to 80 °C. The RI detector was kept at 55°C. The calibration standards are PSS (polysulfonated styrene) with MW ranging from 622000 to 210 Da to create a 3rd order polynomial calibration, recalibrated every 3-6 months. Two PSS checks (Mw 63900 and 3610) are run with every GPC run.

[0080] The NMR spectra were recorded on a Bruker Avance III HD Neobay 400 MHz spectrometer at 35 °C. 300 mg of resin was dissolved in 0.75 mL d6-DMSO containing pyrazine as an internal standard (0.5 % w / w). 13C NMR acquisitions were acquired using a 30° pulse width, power gated decoupling, a 2 s relaxation delay and an acquisition time of 1.6 s. 4096 scans were taken.Materials

[0081] The materials used in the following examples were listed in Table 1. Unless otherwise indicated, the acids used in the examples are provided in aqueous solution form, with their respective concentrations indicated with % by weight.Example 1. Preparation of Hardener Components

[0082] To a 12-liter round bottom flask equipped with a condenser and thermocouple, 3,577.6 g of cold water and 14.2 g of FC-402 defoamer were added and mixed for 5 minutes. 668.2 g of Elvanol 50-42 was slowly added to the mixture under good agitation until the Elvanol 50-42 was completely dissolved. The batch was heated to 90°C using a heating mantle and held for 30 minutes. Then the batch was cooled to 44°C by applying water to the outside of the flask and 1342.8 g of additional water and 898.7 g 3-amminophenol was added to the batch. The batch was further cooled with cooling water to 26.5°C, and 898.7 g of 96.9% sulfuric acid was slowly added over 85 minutes to control exotherm. Once the sulfuric acid was added, 599.94 g of 97.6% formic acid was added to the batch and stirred for 15 minutes. After stirring for 15 minutes, the hardener component El-1 was obtained. The ingredients in weight percentages and the physical properties of El-1 were shown in Table 2. The viscosity was measured with a #4 spindle at 20 rpm at 25°C and the measurement was taken after 60 seconds. The pH and refractive index were measured at 25°C.

[0083] The hardener components El-2, El-3 and El-4 were prepared in a similar manner as El-1. Their ingredients in weight percentages and physical properties were also shown in Table 2.Example 2. Preparation of Resin Components

[0084] To a 12-liter round bottom flask equipped with a condenser and thermocouple, 3646.8g formaldehyde water solution (53.27%, 60°C) and 225.5g water were added and agitated. Next, 5.5 g of 10M borax and 2,731.7 g methanol were added under continuous stirring and the batch was cooled to a target of below 30°C. After about 20 minutes at 28.7°C, a pH sample was taken and read at 25°C. The pH was detennined to be 6.3, so the pH of the batch was adjusted to 9.1 + / - 0.1 through adding 2 g of 25% sodium hydroxide solution. Next, 210.7 g ortho-para toluene sulfonamide and 2731.7 g melamine were quickly added, and the batch was heated to reflux at 78.5°C and held at NTP reflux for 30 minutes. Hot samples were taken from the batch from time to time to monitor the pH. 10% formic acid was used to maintain the pH in the range of from 7.6 to 7.8.

[0085] Samples were taken for dilutability tests at 25°C. After a dilutability of 157% at a hot pH of 7.55 was tested, the batch was cooled to 57.6°C and 421.5g of 53.27% aqueous formaldehyde solution and 9.7g of water were added. The batch was heated back to reflux at a pH of 7.6-7.8 using 1.25 g of 25% sodium hydroxide solution. The same pH range was maintained as the resin was condensed to a final dilutability of 70%. At the end of condensation, 4.3g of 25% sodium hydroxide solution was added to terminate the acid catalyzed condensation reaction and adjust the pH to 9.72. The batch was cooled to 59.5°C and vacuum distillation was carried out to obtain a batch having a Gardener viscosity of Z-4. After adding 1,600g of water, the batch was vacuum distilled again to obtain a Gardner viscosity of Z- 1. After the distilled batch was cooled to about 30°C, 267.0g water, 92.3g of caprolactam, 186.3g of 1,4-butaindiol, and 8.2 g of FC-402 defoamer were added, and the pH was adjusted to 9.76 using 25% sodium hydroxide solution to obtain an intermediate resin product. Finally, 995.06g of this intermediate resin product was mixed with 5.07g of Cimsil under stirring for 30 minutes to obtain amino resin E2-1. The main ingredients in grams and the physical properties of E2-1 are shown in Table 3. The viscosity of the resin was measured using a #4 spindle at 20 rpm at 25°C and taken after 60 seconds.

[0086] The amino resin E2-2 was prepared in a similar manner as E2-1 with an exception that, at the last step, 988.51 g of the intermediate resin product was mixed with 11.52 g of Cimsil under stirring for 10 minutes to obtain amino resin E2-2. The main ingredients in grams of E2-2 and its physical properties are also shown in Table 3.

[0087] The GPC curves of two resin samples Ecobind™ 6500 and E2-1 were depicted in Fig. 1. As illustrated in Fig. 1, E2-1 comprises more large molecules that have an elution time in GPC column less than 35.5 minutes, indicating E2-1 has a higher Mw than Ecobind™ 6500.Example 3. Two-component Curable Compositions Comprising Different Resins and Hardeners

[0088] Four samples of two-component curable compositions were provided with a weight ratio of resin component to hardener component being 2: 1. As shown in Table 4, a two-component curable composition including commercial resin EcoBind™ 6500 and commercial hardener M- 700 Y was used as a comparative example (CE1). Sample E3-1 was a combination of EcoBind™ 6500 and a hardener component prepared from Example 1 (El-1). Sample E3-2 was a combination of a resin component prepared from Example 2 (E2-1) and commercial hardener M-700Y. Sample E3-3 was a combination of El-1 and E2-1 prepared in Examples 1 and 2 respectively.

[0089] The four samples were tested for their viscosity over time and the results were shown as steady shear gel curves in Fig. 2. As shown in Fig. 2, comparing with sample CE1, the other three samples E3-1, E3-2 and E3-3 showed less gel time, indicating a faster curing speed. The sample E3-3 had the fastest curing speed among the four samples.

[0090] The four samples were also tested for their storage and loss moduli using a 40 mm diameter steel parallel plate geometry at 25°C using a frequency of 0.2 HZ at 1.0% strain. The testing results were shown in Fig. 3. Comparing with sample CE1, sample E3-1 (EcoBind™ 6500: El-1 = 2: 1) showed a very quick increase of both storage modulus and loss modulus within the first several minutes. Sample E3-3 (E2-1: El-1 = 2:1) also showed fast establishment of storage modulus and loss modulus at initial stage, and furthermore, it presented a very high final storage modulus. Sample E3-2 (E2-1: M-700Y = 2: 1) did not show an obvious improvement on storage modulus and loss modulus over CE1. The testing results demonstrated that the use of the hardener component made in Example 1 (El-1) can result in a fast buildup of both storage modulus and loss modulus within the first 20 minutes and can achieve a high final storage modulus.Example 4. Two-component Curable Compositions with Hardener Components Prepared from Sulfuric Acid of Different wt.%

[0091] A series of hardener components were prepared according to the similar method as described in Example 1. The wt.% of their main ingredients were shown in Table 5. As shown in Table 5, these hardener components were made from 3-aminophenol and formic acid of the similar wt.%, but sulfuric acid of different wt.%.

[0092] Each of the hardener components shown in Table 5 (El-5 to El-12) were mixed with the resin component E2-1 (prepared in Example 2) in a weight ratio of 1:2 to obtain a series of curable composition samples. The viscosity of these curable compositions was tested over time and reflected as steady shear gel curves in Fig. 4. The gel curve of CE1 (EcoBind™ 6500: M- 700Y = 2: 1) was also shown in Fig. 4 as a control.

[0093] As shown in Fig. 4, with the increase in the wt.% of sulfuric acid used to prepare the hardener component, the gel time of the resulting two-component curable compositions shortened. This indicated that a hardener component made with an excess amount of sulfuric acid can result in a shortened gel time. An excess amount of sulfuric acid can result in a complete protonation of 3-aminophenol (as shown in the following 13C-NMR analysis), which can lead to a fast curing of amino resins.

[0094] 13C-NMR analysis was conducted for hardener components El-5 and El-1. The preparation of El-5, 6.55 wt.% of sulfuric acid and 10.71 wt.% 3-aminophenol were used, while in the preparation of El-1, 10.9 wt.% of sulfuric acid and 11.2 wt.% of 3-aminophenol were used. Their NMR spectra were shown in Fig. 5. The NMR spectrum of El-5 showed a “square” peak broadening at from 108 ppm to 118 ppm, while the NMR spectrum of El-1 showed clear discreet peaks instead of the broadening. Usually, the broadening is a mix of chemical shift anisotropy, dipole coupling and extreme variation, such as such as structural disorder, molecules with different conformations or an environment with a lot of hydrogen bonding. It was very likely the broa dening in Fig. 5 upper spectrum was caused by various conformations of the 3-aminophenol as part of it forms sulfate salt and / or interference due to hydrogen bonding interactions with the polyvinyl alcohol in the system. The broadening disappeared after the system became more homogenous, i.e., a complete protonation of 3-aminophenol. Therefore, the NMR results indicated a complete protonation of 3-aminophenol was achieved for El-1, but not for El-5.Example 5. Two-component Curable Compositions with Hardener Components Prepared from Formic Acids of Different wt.%

[0095] A series of hardener components were prepared according to the similar method described in Example 1. The wt.% of their main ingredients were shown in Table 6. As shown in Table 6, these hardener components were made from 3-aminophenol and sulfuric acid of the similar wt.%, but formic acid of different wt.%.

[0096] Each of the hardener components shown in Table 6 was mixed with the resin component E2-1 (prepared in Example 2) in a weight ratio of 1:2 to obtain a series of curable composition samples. The viscosity of these curable compositions was tested over time and reflected as steady shear gel curves in Fig. 6.

[0097] As shown in Fig. 6, using a higher wt.% of formic acid in the preparation of a hardener component, resulted in a shortened gel time of the two-component curable compositions.Example 6. Two-component Curable Compositions with Resins of Different Formaldehyde to Melamine Molar Ratios

[0098] In this example, El-1 prepared in Example 1 was used as the hardener component. A series of MF resins with different molar ratios of formaldehyde to melamine (2.90: 1, 2.95: 1, 3.10:1, 3.25:1, 3.50:1, and 3.59:1) were prepared using the same method of preparing E2-1 in Example 2. The prepared MF resin was used as the resin component. The resin component and the hardener component were mixed in a fixed weight ratio of 2: 1.

[0099] The viscosity over time was tested and their steady shear gel curves were shown in Fig. 7. As shown in Fig. 7, the increase of molar ratios of formaldehyde to melamine resulted in a shorter gel time which means a faster curing process.

[0100] The two-component curable composition samples having MF resins of different formaldehyde to melamine molar ratios (2.90: 1, 3.25: 1 and 3.50:1) were also tested for their storage modulus and loss modulus. According to the results shown in Fig. 8, samples prepared from MF resins with a higher molar ratios of formaldehyde to melamine presented a faster curing speed and reached 70 KPa storage modulus within 40 minutes, while CE1 (EcoBind™ 6500: M- 700Y) failed to reach 70 KPa storage modulus within 100 minutes. The results demonstrate that increasing the molar ratio of formaldehyde to melamine during MF resin preparation can lead to a faster curing.Example 7. Ambient Gluing of Small-scale Test Glulam Beams on Surfaced Douglas Fir

[0101] Four two-component curable compositions, E3-3, E3-4, CEl and CE2 as listed in Table 7 were used to glue glulam beams on surfaced Douglas fir. Each of them was applied at a 2: 1 weight ratio (resin: hardener) at a 70 lbs / 1000ft2spread rate using Separate Application to make a 1- 2 ply - 3 / 4" x 5 1 / 2" x 24" beam per condition.

[0102] All samples were laid up parallel to grain with the shortest assembly time condition of 0 / 5 minutes. They were tested at intervals after pressing using compression testing protocols per AITC T-107. For CE1 and CE2, the testing times in Table 8 do not include the 40 min press time at 150 PSI as they did not reach green strength within 40 minutes. Photomicroscopy was conducted on some samples (those marked with*) to look at penetration into the wood. The testing results were shown in Table 8 and Figs. 9 and 10. CE1 and CE2 used the same commercial products but different batches, so the corresponding glulam beam samples showed slight differences in the testing results. A glulam beam prepared with CE1 after curing 24 hours was used as a Control Sample. The “PSI% of Control” in Table 8 is based on 100% of the breaking load value of the Control Sample.

[0103] As shown in the first half of Table 8, the samples prepared with the two-component curable composition E3-3 showed an overall higher strength than the sample made with CE1, especially within the first two hours. For samples made with E3-3, at three press time of 20 min,60 min and 24 hr, they were examined using photomicroscopy. The 20 min sample showed signs of wood failure, but this was not seen on the 60 min sample. The testing results of samples made from E3-3 and CE1 over time were more clearly demonstrated in Fig. 9 (a) and (b). Fig. 9(a) shows all breaking load values over time of samples prepared with E3-3 and CE1. All samples werepressed at 150 PSI for 40 min under ambient conditions. The two-component curable composition E3-3 built strength faster than CE1 during initial cure until the 4-hour mark. The final breaking loads after 24 hours and the 24-hour overnight samples were all comparable. The testing results showed that the two-component curable composition E3-3 has a faster initial cure and a slower post cure. FIG. 9(b) showed breaking loads for the first two hours of cure. Within 60 min after applying, samples made from CE1 cannot be effectively handled for testing, while the samples made from two-component curable composition E3-3 were able to provide data at 20 minutes and at 40 minutes. From 1 hour to 2 hours, the samples made from E3-3 showed a higher breaking load than the samples made from CE1.

[0104] As shown in the bottom part of Table 8, the samples prepared with the two- component curable composition E3-4 showed an overall higher strength than the samples prepared with CE2, especially within the first six hours. The testing results of samples made from E3-4 and CE2 overtime were more clearly demonstrated in Fig. 10(a) and (b). Fig. 10(a) shows all breaking load values over time of samples prepared with E3-4 and CE2. All samples pressed at 150 PSI for 40 min under ambient conditions. The two-component curable composition E3-4 built strength faster than CE2 during initial cure until the 6-hour mark. The final breaking loads after 24 hours and the 24-hour overnight samples were all comparable. The testing results showed that the two- component curable composition E3-4 has a faster initial cure and a slower post cure. Fig. 10(b) showed breaking loads for the first two hours of cure. Within 60 min after applying, samples made from CE2 cannot be effectively handled for testing, while the samples made from two-component curable composition E3-4 were able to provide data at 20 minutes and at 40 minutes. From 1 hour to 2 hours, the samples made from E3-4 showed a higher breaking load than the samples made from CE2.Example 8. Preparation of Hardener Components Using Varied First Acids and Their Application for Curing

[0105] A series of hardener components were prepared using different first acids. The general procedure involved preparing a polyvinyl alcohol (PVOH) mixture, dissolving 3- aminophenol with a selected first acid in the PVOH mixture, and subsequently adding formic acid as a second acid. The resulting hardener components were then tested for their curing performance with an MF resin.

[0106] Preparation of PVOH mixture. In a 12-liter glass round bottom flask, 2,613 g of water, 488 g of PVOH, and 10.57 g of FC-402 defoamer were added. The mixture was heated to 90°C and held at 90°C for 30 minutes, then cooled to room temperature for use in the preparation of the following hardener components.

[0107] Preparation of hardener component El-16. In a 2-liter glass round bottom flask, 501.2 g of the PVOH mixture and 143.2 g of water were added, followed by 105.5 g of 3- aminophenol. Over 20 minutes, 114.5 g of hydrochloric acid (37%) was added under stirring. The solution turned yellow and exothermic. After stirring for 5 minutes, 3 -aminophenol was fully solubilized. Next, 101.2 g of formic acid (97.6%) was added and stirred for 15 minutes.

[0108] Preparation of hardener component El-17. In a 1.5-liter metal beaker, 500.8 g of the PVOH mixture and 118.1 g of water were added, followed by 105.2 g of 3-aminophenol. Over 10 minutes, 139.3 g of acetic acid (50%) was added under stirring. The solution turned light brown and a small exotherm occurred. After stirring for 50 minutes, 3-aminophenol was not fully solubilized. An additional 108.0 g of acetic acid (50%) was added. After stirring for 20 minutes, 3-aminophenol was fully solubilized. Next, 101.2 g of formic acid (97.6%) was added and stirred for 15 minutes.

[0109] Preparation of hardener component El-18. In a 1.5-liter metal beaker, 500.7 g of the PVOH mixture and 150.7 g of water were added, followed by 105.5 g of 3 -aminophenol. Over 10 minutes, 106.8 g of formic acid (50%) was added under stirring. The solution turned light yellow. After stirring for 25 minutes, 3-aminophenol was fully solubilized. Next, 101.2 g of formic acid (97.6%) was added and stirred for 15 minutes.

[0110] Preparation of hardener component El-19. In a 2-liter glass round bottom flask, 511.8 g of the PVOH mixture and 300.0 g of pTSA (77%) were added, followed by 105.5 g of 3- aminophenol. The solution turned light brown. After stirring for 8 minutes, 3-aminophenol was fully solubilized. Next, 101.2 g of formic acid (97.6%) was added and stirred for 15 minutes.

[0111] Preparation of hardener component El-20. In a 2-liter glass round bottom flask, 376.4 g of water, 1.5 g of FC-402 defoamer, and 70.3 g of PVOH were added under stirring, and heated to 90°C for 30 minutes, then cooled to 40°C. 372.5 g of a citric acid solution (60%) was added, followed by 94.6 g of 3 -aminophenol. A slight exotherm was observed. After stirring for15 minutes, 3-aminophenol was fully solubilized. Next, 88.6 g of formic acid (97.6%) was added and stirred for 15 minutes.

[0112] Preparation of hardener component El-21. In a 2-liter glass round bottom flask, 435.5 g of water, 1.8 g of FC-402 defoamer, and 81.3 g of PVOH were added under stirring, and heated to 90°C for 30 minutes, then cooled to 40°C. 159.0 g of water and 109.4 g of 3 -aminophenol were added. 108.0 g of butyric acid (99.7%) was slowly added. The solution turned light brown. After stirring for 10 minutes, 3-aminophenol was fully solubilized. Next, 105.0 g of formic acid (97.6%) was then added and stirred for 15 minutes.

[0113] Preparation of hardener component El -22 (Comparative). In a 2-liter metal beaker, 500.8 g of the PVOH mixture was added, followed by 200 g of maleic acid solution (30%) and 105.5 g of 3-aminophenol. Multiple additions of maleic acid solution (30%) were made under stirring, reaching an acid to amine mole ratio of 3.47:1. Even after extended mixing, 3- aminophenol was not fully solubilized. The result indicates that maleic acid is not suitable to be used as the first acid.

[0114] Preparation of hardener component El-23 (Comparative). Addition of phosphoric acid to 3-aminophenol in the presence of water resulted in the formation of a solid white precipitate. The result indicates that phosphoric acid is not suitable to be used as the first acid.

[0115] All tested first acids except maleic acid and phosphoric acid successfully solubilized 3-aminophenol and produced a homogeneous hardener solution. The six hardener components El- 16 to El-21 were summarized in Table 9, including the mole ratio of the first acid to 3-aminophenol.

[0116] Hardener components El-1 (as prepared in Example 1), and El-16 to El-21 were evaluated for their ability to cure MF resin under ambient conditions. The hardener and MF resin EcoBind™ 6500 were mixed at a 2:1 weight ratio for 1.5 minutes, and 1.5 ml of the mixture was syringed onto the rheometer plate for a steady shear test at 25°C. The rheometer runs were done on a 40mm parallel plate, peltier plate steel, with the velocity set to 0.33 rad / s with a sampling interval of 30.0 secs / point. The system was considered gelled when viscosity reached 200,000 cPs. All hardener components successfully initiated gelation of the MF resin. The gel curves for each system are shown in Fig. 11. The results demonstrate that a variety of mineral and organic acids can be used as the first acid in the preparation of a hardener component.Example 9. Preparation of Hardener Components Using Varied Second Acids and Their Application for Curing

[0117] A series of hardener components were prepared using different second acids. The general procedure involved preparing a PVOH mixture, dissolving 3-aminophenol with sulfuric acid in the PVOH mixture, and subsequently adding a second acid. The second acid was added in an amount that the mole ratio of the second acid to 3-aminophenol was set at 2.22:1. The resulting hardener components were then tested for their curing performance with an MF resin.

[0118] Preparation of hardener component El-24 (no second acid). In a 12-liter glass round bottom flask, 3,484 g of water, 650 g PVOH, and 14.10 g of FC-402 defoamer were added and mixed. The resulting mixture was heated to 90°C for 30 minutes and then cooled down to 40°C. 1,175 g of water and 875 g of 3-aminophenol were added. Over 120 minutes, at below 30°C, 982 g of sulfuric acid (96.6%) was slowly added. After addition of sulfuric acid, 3-aminophenol was fully solubilized.

[0119] Preparation of hardener component El-25. In a 2 -liter glass round bottom flask, 897.6 g of El-24 was added. With agitation, 214.3 g of a hydrochloric acid solution (37%) was slowly added. The mixture was stirred for 20 minutes.

[0120] Preparation of hardener component El-26. In a 1 -liter metal beaker, 897.6 g of El- 24 was added. With agitation, 131 g of an acetic acid solution (50%) was slowly added. The mixture was stirred for 20 minutes.

[0121] Preparation of hardener component El-27. In a 1 -liter metal beaker, 897.6 g of El- 24 was added. With agitation, 226.1 g of a sulfuric acid solution (96.6%) was slowly added. A small exotherm was recorded. The mixture was stirred for 20 minutes.

[0122] Preparation of hardener component El-28. In a 2-liter glass round bottom flask, 525.7 g of El-24 was added. With agitation, 374.3 g of a pTSA (60%) was slowly added. The mixture was stirred for 20 minutes.

[0123] Preparation of hardener component El-29. In a 1-liter metal beaker, 255. 1 g of El- 24 was added. With agitation, 244.9g of a citric acid solution (60%) was slowly added. The mixture was stirred for 20 minutes.

[0124] Preparation of hardener component El-30. In a 2-liter glass round bottom flask, 659.0 g of El-24 was added. With agitation, 145.0 g of a butyric acid solution (99%) was slowly added. The mixture was stirred for 20 minutes.

[0125] Preparation of hardener component El-31. In a 1 -liter metal beaker, 409.0 g of El- 24 was added. With agitation, 391.8 g of a maleic acid solution (30%) was slowly added. A small exotherm was recorded. The mixture was stirred for 20 minutes.

[0126] Preparation of hardener component El-32. In a 2-liter glass round bottom flask, 897.5 g of El-24 was added. With agitation, 218.2 g of a phosphoric acid solution (85%) was slowly added. The mixture was stirred for 20 minutes.

[0127] The eight hardener components El-25 to El-31 were summarized in Table 10.

[0128] Hardener components El-1 (as prepared in Example 1), and El-25 to El-32 were evaluated for its ability to cure MF resin under ambient conditions. The hardener and MF resin EcoBind™ 6500 were mixed at a 2:1 weight ratio for 1.5 minutes, and 1.5 ml of the mixture wassyringed onto the rheometer plate for a steady shear test at 25°C. The rheometer runs were done on a 40mm parallel plate, peltier plate steel, with the velocity set to 0.33 rad / s with a sampling interval of 30.0 secs / point. The system was considered gelled when viscosity reached 200,000 cPs. All hardener formulations successfully initiated gelation of the MF resin. The gel curves for each system are shown in Fig. 12. The results demonstrate that a variety of mineral and organic acids can be used as the second acid in the preparation of a hardener component.Example 10. Preparation of Hardener Components Using Varied Aromatic Amines and Their Application for Curing

[0129] A series of hardener components were prepared by reacting various aromatic amines with sulfuric acid in water. The resulting sulfate salts were isolated and tested for their ability to cure MF resin (EcoBind™ 6500) under ambient conditions.

[0130] Preparation of hardener component El-33. In a 250 mL beaker with a stir bar, 135 g of water and 4.7 g of sulfuric acid (96.6%) were added and mixed for 2 minutes. 10.0 g of 3- aminophenol was slowly added and stirred for 8 minutes until fully dissolved. The molar ratio of acid to amine was 1 :2. A pH of 3.29 was recorded. The solution was poured into a crystallization dish and dried under vacuum at 105 °C for 10 hours. The resulting solid was ground with a mortar and pestle into a fine white-yellowish powder. 1.5 g of the salt was added into 20 g of MF resin and stirred for 2 minutes. After 24 hours, the resin was cured.

[0131] Prepara tion of hardener component El-34. In a 250 mL beaker with a stir bar, 135 g of water and 4.7 g of sulfuric acid (96.6%) were added and mixed for 2 minutes. 10.0 g of m- phenylenediamine was slowly added and stirred for 3 minutes until fully dissolved. The molar ratio of acid to amine was 1 :2. A pH of 4.38 was recorded. The solution was poured into a crystallization dish and dried under vacuum at 105°C for 10 hours. The resulting solid was ground with a mortar and pestle into a fine light blue powder. 1.5 g of the salt was added into 20 g of MF resin and stirred for 2 minutes. After 24 hours, the resin was cured.

[0132] Preparation of hardener component El-35. In a 500 mL beaker with a stir bar, 135 g of water and 4.7 g of sulfuric acid (96.6%) were added and mixed for 2 minutes. 10.0 g of p- phenylenediamine was slowly added and stirred overnight. The mixture turned dark purple. The next day, a pH of 6.22 was recorded. An additional 3.1 g of sulfuric acid (96.6%) and 300 g of water were added, and the solution was stirred overnight. The molar ratio of acid to amine was1:1.16. The solids were filtered off, and the solution was poured into a crystallization dish and dried under vacuum at 105°C for 18 hours. The resulting solid was ground with a mortar and pestle into a fine dark purple powder. 1 .5 g of the salt was added into 20 g of MF resin and stirred for 2 minutes. After 24 hours, the resin was cured.

[0133] Preparation of hardener component El-36. In a 150 mL beaker with a stir bar, 50 g of water and 5.0 g of 4-amino-3 -methylphenol were added and mixed. 2.1 g of sulfuric acid (96.6%) was slowly added, followed by an additional 0.9 g of sulfuric acid (96.6%). The mixture w'as stirred overnight. The molar ratio of acid to amine was 1:1.37. A pH of 3.08 was recorded. Small brown solids were filtered off. The solution was poured into a crystallization dish and dried under vacuum at 105°C for 24 hours. The resulting solid was ground with a mortar and pestle into a fine brown powder. 1.5 g of the salt was added into 20 g of MF resin and stirred for 2 minutes. After 24 hours, the resin was cured.

[0134] Preparation of hardener component El-37 (comparative). In a 150 mL beaker with a stir bar, 100 g of water and 5.0 g of sulfuric acid (96.6%) were added and mixed for 2 minutes.3 g of 4,4’-diaminodiphenylmethane was added into the mixture. Excess water and acid w'ere added, but still the 4,4 ’-diaminodiphenylmethane was unable to solubilize. A pH of 3.39 was recorded.

[0135] In this example, the hardeners prepared by reacting various aromatic amines, including 3-aminophenol, m-phenylenediamine, p-phenylenediamine, and 4-amino-3- methylphenol, with sulfuric acid successfully initiated curing of the MF resin. However, a hardener w'as not successfully prepared from 4,4’-diaminodiphenylmethane, as it failed to solubilize in a sulfuric acid solution.Example 11. Two-component Curable Compositions Comprising MUF Resin

[0136] A hardener El-38 was prepared with 10.71 wt. % of 3-aminophenol, 6.55 wt.% of sulfuric acid (100%), and 14.0 wt.% of formic acid (100%) according to the method described in Example 1. As shown in Table 11, in the two-component curable composition E3-5, a commercial MUF resin CB-45 was used as the resin component, and the El-38 was used as the hardener component. The comparative example used the same MUF resin and a commercial hardener 5000Q.

[0137] 20 g of CB-45 and 10 g of El-38 hardener were added into a dixie cup and stirred for 1.5 minutes with a popsicle stick. 1.5 ml of the mixture was syringed onto the rheometer plate. The rheometer run was done at 25°C on a 40mm parallel plate, Peltier plate steel, the velocity was set to 0.33 rad / s with a sampling interval of 30.0 secs / point. The system was considered gelled once 200,000 cPs on viscosity was met. A similar procedure was conducted for the comparative example. The gel curves for the two systems are shown in Fig. 13.

[0138] As illustrated in Fig. 13, the two-component curable composition E3-5 had a gelation time of 15.67, while the comparative example exhibited a gelation time of 56.74 minutes. The results demonstrates that the hardener prepared according to the present invention is highly effective in promoting rapid cure of MUF resin at ambient temperature, achieving significantly faster gelation than conventional resorcinol-based hardeners.

[0139] The terminology as set forth herein is for description only and should not be construed as limiting the disclosure as a whole. All references to singular characteristics or limitations of the present disclosure shall include the corresponding plural characteristic or limitation, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made. Unless otherwise specified, “a,” “an,” “the,” and “at least one” are used interchangeably. Furthermore, as used in the description and the appended claims, the singular forms “a,” “an,” and “the” are inclusive of their plural forms, unless the context clearly indicates otherwise.

[0140] To the extent that the term “includes” or “including” is used in the description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When intending to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use.

[0141] All combinations of method or process steps as used herein can be performed in any order, unless otherwise specified or clearly implied to the contrary by the context in which the referenced combination is made.

[0142] Unless otherwise indicated, all numbers expressing quantities of ingredients, chemical and molecular properties, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present exemplary aspects. At the very least, each numerical parameter should be construed in light of the number of significant digits and ordinary rounding approaches.

[0143] All ranges and parameters, including but not limited to percentages, parts, and ratios, disclosed herein are understood to encompass any and all sub-ranges assumed and subsumed therein, and every number between the endpoints. For example, a stated range of “1 to 10” should be considered to include any and all sub-ranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 1 to 6.1, or 2.3 to 9.4), and to each integer (1, 2, 3, 4, 5, 6, 7, 8, 9, and 10) contained within the range.

[0144] The subject matter of the invention can comprise, consist of, or consist essentially of the essential elements of the disclosure as described herein, as well as any additional or optional element described herein, or which is otherwise useful in hardener component, resin component, curable composition and composite article.

[0145] Every document cited herein is incorporated herein by reference in its entirety unless otherwise specified. The citation of any document is not to be construed as an admission that it is prior art with respect to any invention disclosed or claimed herein. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0146] It will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

Claims

CLAIMSWhat is claimed is:

1. A hardener component for hardening a reactive amino resin of a curable composition, comprising a salt formed by an aromatic amine and a first acid, wherein the aromatic amine has a chemical structure of:wherein Ri represents -OH or -NHz, Rz represents a C1-C3alkyl, and n=0 or 1.

2. The hardener component according to claim 1 , wherein the aromatic amine comprises 2- aminophenol, 3-aminophenol, 4-aminophenol, m-phenylenediamine, p-phenylenediamine, or 2,4- diaminophenol.

3. The hardener component according to claim 1 or claim 2, wherein the hardener component is in a liquid form or a solid form.

4. The hardener component according to any one of claims 1 to 3, wherein the first acid is selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, phosphoric acid, nitric acid, perchloric acid, persulphuric acid, formic acid, acetic acid, maleic acid, propionic acid, butyric acid, iso-butyric acid, hydroxyacetic acid, 2- hydroxypropanoic acid, 3-hydroxypropanoic acid, hydroxybutanoic acid, 2,3-dihydroxypropanoic acid, citric acid, oxalic acid, malonic acid, fumaric acid, acrylic acid, methacrylic acid, paratoluene sulfonic acid, methyl sulfonic acid, and combinations thereof.

5. The hardener component according to any one of claims 1 to 4, wherein the first acid is sulfuric acid, hydrochloric acid, phosphoric acid, or formic acid.

6. The hardener component according to any one of claims 1 to 5, further comprising a second acid, wherein the second acid comprises one or more acids selected from the group consisting ofsulfuric acid, sulfurous acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, phosphoric acid, nitric acid, perchloric acid, persulphuric acid, formic acid, acetic acid, maleic acid, propionic acid, butyric acid, iso-butyric acid, hydroxyacetic acid, 2-hydroxypropanoic acid, 3- hydroxypropanoic acid, hydroxybutanoic acid, 2,3-dihydroxypropanoic acid, citric acid, oxalic acid, malonic acid, fumaric acid, acrylic acid, methacrylic acid, para-toluene sulfonic acid, and methyl sulfonic acid.

7. The hardener component according to claim 6, wherein the second acid is formic acid.

8. The hardener component according to any one of claims 1 to 7, further comprising a polar solvent.

9. The hardener component according to any one of claims 1 to 8, further comprising one or more additives selected from the group consisting of non-polar solvent, defoamer, viscosity modifier, rheology modifier, formaldehyde scavenger, plasticizer, filler, flame retardant, lubricant, softening agent, pigment, biocide, latent acid donor, surfactant, dispersant, latex, and hydrophobic agent.

10. The hardener component according to any one of claims 1 to 9, comprising, based on the total weight of the hardener component, from 10 wt.% to 40 wt.% of the salt formed by the aromatic amine and the first acid; from 0 wt.% to 40 wt.% of a second acid; from 20 wt.% to 90 wt.% of a polar solvent; and from 0 wt.% to 40 wt.% of one or more additives.

11. The hardener component according to any one of claims 1 to 10, wherein the hardener component is substantially free of resorcinol.

12. The hardener component according to any one of claims 1 to 11 , wherein the hardener component has a pH in a range of from about -1 to about 4.

13. The hardener component according to any one of claims 1 to 12, wherein the hardener component has a viscosity in a range of from 500 cPs to 8,000 cPs, measured by a Brookfield viscometer using #4 spindle at 20 rpm at 25°C.

14. The hardener component according to any one of claims 1 to 13, wherein the hardener component has a solid content of from 15 wt.% to 60 wt.%.

15. The hardener component according to any one of claims 1 to 14, wherein the hardener component further comprises from 0.01 wt.% to 20 wt.% of the first acid, based on the total weight of the hardener component.

16. A method for preparing a hardener component for hardening a reactive amino resin of a curable composition, comprising reacting an aromatic amine and a first acid in a polar solvent to obtain a first solution, wherein the stoichiometric ratio of the aromatic amine to the first acid is no greater than 1.0.

17. The method according to claim 16, wherein the stoichiometric ratio of the aromatic amine to the first acid is less than 0.8.

18. The method according to claim 16, wherein the stoichiometric ratio of the aromatic amine to the first acid is less than 0.6.

19. The method according to claim 16, wherein the aromatic amine is completely protonated.

20. The method according to any one of claims 16 to 19, wherein the aromatic amine has a chemical structure of:wherein Ri represents -OH or -NH2, R2represents a C1-C3alkyl, and n=0 or 1.

21. The method according to any one of claims 16 to 20, wherein the aromatic amine comprises 2-aminophenol, 3-aminophenol, 4-aminophenol, m-phenylenediamine, p-phenylenediamine, 2,4- diaminophenol, or combination thereof.

22. The method according to any one of claims 16 to 21 , wherein the first acid is selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, phosphoric acid, nitric acid, perchloric acid, persulphuric acid, formic acid, acetic acid, maleic acid, propionic acid, butyric acid, iso-butyric acid, hydroxyacetic acid, 2- hydroxypropanoic acid, 3-hydroxypropanoic acid, hydroxybutanoic acid, 2,3-dihydroxypropanoicacid, citric acid, oxalic acid, malonic acid, fumaric acid, acrylic acid, methacrylic acid, paratoluene sulfonic acid, methyl sulfonic acid, and combinations thereof.

23. The method according to any one of claims 16 to 22, further comprising adding a second acid into the first solution, wherein the second acid comprises one or more selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, phosphoric acid, nitric acid, perchloric acid, persulphuric acid, formic acid, acetic acid, maleic acid, propionic acid, butyric acid, iso-butyric acid, hydroxyacetic acid, 2-hydroxypropanoic acid, 3-hydroxypropanoic acid, hydroxybutanoic acid, 2,3-dihydroxypropanoic acid, citric acid, oxalic acid, malonic acid, fumaric acid, acrylic acid, methacrylic acid, para-toluene sulfonic acid, and methyl sulfonic acid.

24. The method according to any one of claims 16 to 23, wherein the following ingredients are used, based on the total weight of the hardener component: from 6 wt.% to 22 wt.% of the aromatic amine; from 4 wt.% to 18 wt.% of the first acid; from 0 wt.% to 40 wt.% of the second acid; and from 20 wt.% to 90 wt.% of the polar solvent.

25. A curable composition, comprising: a resin component comprising a reactive amino resin; and a hardener component according to any one of claims 1-15, wherein the resin component and the hardener component are present in a weight ratio of greater than 1 :1.

26. The curable composition according to claim 25, wherein the resin component and the hardener component are present in a weight ratio of greater than 1.5:1.

27. The curable composition according to claim 25, wherein the resin component and the hardener component are present in a weight ratio of greater than 2: 1.

28. The curable composition according to any one of claims 25-27, wherein the reactive amino resin comprises melamine-formaldehyde resin, urea-formaldehyde resin, melamine-urea- formaldehyde, or combination thereof.

29. The curable composition according to any one of claims 25-28, wherein the reactive amino resin is methylated, methylolated, or, both methylated and methylolated.

30. The curable composition according to any one of claims 25-29, wherein the reactive amino resin has a weight average molecular weight (Mw) in a range of from 125 Da to 155 Da, measured by gel permeation chromatography.

31. The curable composition according to any one of claims 25-30, wherein the reactive amino resin has a weight average molecular weight (Mw) in a range of from 140 Da to 155 Da, measured by gel permeation chromatography.

32. The curable composition according to any one of claims 25-31, wherein the reactive amino resin has a poly dispersity index (PDI) in a range of from 1.0 to 5.0, measured by gel permeation chromatography.

33. The curable composition according to any one of claims 25-32, wherein the reactive amino resin has a GPC pattern substantially similar to at least one of the patterns in Figure 1.

34. The curable composition according to any one of claims 25-33, wherein the resin component has a pH in a range of from 7 to 11.

35. The curable composition according to any one of claims 25-34, wherein the resin component has a viscosity in a range of from 500 cPs to 8,000 cPs, measured by a Brookfield viscometer using #4 spindle at 20 rpm at 25°C.

36. The curable composition according to any one of claims 25-35, wherein the resin component has a solid content of from 50 wt.% to 90 wt.%.

37. fhe curable composition according to any one of claims 25-36, wherein the resin component is prepared by a method comprising: reacting melamine, methanol and a first part of formaldehyde at a temperature of from 75°C to 80°C and at a pH of from 7.3 to 8.0 to obtain a first resin solution having a dilutability greater than 150%; adding a second part of formaldehyde to the first resin solution and heating to reflux at a temperature of from 75°C to 80°C and at a pH of from 7.3 to 8.0 to obtain a second resin solution having a dilutability less than 150%; andadjusting the pH of the second resin solution to greater than 9.5.

38. The curable composition according to any one of claims 25-37, wherein the resin component further comprises one or more selected from the group consisting of non-polar solvent, defoamer, viscosity modifier, rheology modifier, formaldehyde scavenger, plasticizer, filler, flame retardant, lubricant, softening agent, pigment, biocide, latent acid donor, surfactant, dispersant, latex, and hydrophobic agent.

39. A composite article, comprising a cured product of the curable composition of any one of claims 25 to 38 and a substrate.

40. The composite article according to claim 39, wherein the substrate comprises a lignocellulose material.

41. The composite article according to claim 39 or claim 40 is a wood composite.

42. The composite article according to claim 41, wherein the wood composite is a crosslaminated timber, a glue-laminated beam, or a rig mat.

43. A process for making a composite article, comprising: providing a curable composition of any one of claims 25 to 38; applying the curable composition on a substrate; and curing the curable composition.

44. The process according to claim 43, wherein the applying of the curable composition is conducted by coating a surface of the substrate with the curable composition in a spread rate of from 40 lbs to 1 10 lbs / 1000ft2.

45. The process according to claim 43, wherein the applying of the curable composition is conducted by blending the curable composition with the substrate in a weight ratio of from 1 : 100 to 50:100.

46. The process according to any one of claims 43-45, further comprising consolidating the substrate by applying pressure or extrusion.

47. The process according to any one of claims 43-46, wherein the curing of the curable composition occurs at a temperature of from 15°C to 35°C.

48. The process according to any one of claims 43-46, wherein the curing of the curable composition occurs at a temperature of from 35°C to 100°C.

49. The process according to any one of claims 43-46, wherein the curing of the curable composition occurs under a radio frequency treatment.

50. The process according to any one of claims 43-49, wherein the substrate comprises a lignocellulose material.

51. The process according to any one of claims 43-50, wherein the composite article is a wood composite.

52. The process according to claim 51 , wherein the wood composite is a cross-laminated timber, a glue-laminated beam, or a rig mat.

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