High acid value polyester

Abstract

A coating composition comprises: (a) a melamine resin having imino and hydroxymethyl functional groups, the imino and hydroxymethyl functional groups together comprising 30 mol% or more of the total functionality of the melamine resin; and (b) at least one polymer reactive with (a), obtained from a component comprising polytetrahydrofuran and a carboxylic acid or its anhydride. The polytetrahydrofuran comprises more than 20% by weight of the component forming the polymer (b), and the carboxylic acid or its anhydride comprises more than 13% by weight of the component forming the polymer (b). Based on the total resin solids of the polymer (b), the acid value of the polymer (b) is in the range of 40 to 60.

Description

Technical Field

[0001] This invention relates to coating compositions, coatings prepared using said coating compositions, and methods for preparing coatings. Background Technology

[0002] Coatings are applied to a wide variety of substrates to provide color and other visual effects, corrosion resistance, abrasion resistance, chemical resistance, etc. Furthermore, various types of coatings, such as those applied to packaging and automotive substrates, can be formed from compositions that can be baked and formed at low curing temperatures. Because these compositions can be baked at low curing temperatures, they have been found to be usable for forming coatings with faster application times and lower costs. Therefore, the object of the present invention is to provide a coating composition that can be dehydrated and cured at relatively low temperatures to form coatings with a variety of properties, thereby reducing costs and improving the efficiency of the coating process. Summary of the Invention

[0003] This invention relates to a coating composition comprising: (a) a melamine resin containing imino and hydroxymethyl functional groups, the imino and hydroxymethyl functional groups together comprising 30 mol% or more of the total functionality of the melamine resin; and (b) at least one polymer, said at least one polymer being reactive with (a), obtained from a component comprising polytetrahydrofuran and a carboxylic acid or its anhydride, wherein the polytetrahydrofuran comprises more than 20% by weight of said component forming said polymer (b), and the carboxylic acid or its anhydride comprises more than 13% by weight of said component forming said polymer (b), and wherein if said polymer (b) does not contain core-shell particles, then based on said polymer ( b) the total resin solids of the polymer having an acid value in the range of 40 to 60; or the polymer (b) that is reactive with the melamine resin (a) comprises polymer core-shell particles, wherein at least a portion of the polymer shell of the core-shell particles is covalently bonded to at least a portion of the polymer core of the core-shell particles, and wherein the polymer shell of the core-shell particles is obtained from a composition comprising more than 20% by weight of polytetrahydrofuran and more than 13% by weight of a carboxylic acid or its anhydride, and wherein, based on the total resin solids of the polymer forming the polymer shell, the acid value of the polymer shell is in the range of 40 to 60. Attached Figure Description

[0004] Figure 1a The obtained melamine for RESIMENE HM 2608 13 C-NMR spectrum; and

[0005] Figure 1b The obtained melamine targeting CYMEL 202 13 C-NMR spectra. Detailed Implementation

[0006] For the purposes of the following detailed description, it should be understood that the invention may take various alternative variations and sequences of steps unless explicitly stated otherwise. Furthermore, except in any operational instance or where otherwise indicated, all figures representing the amounts of ingredients used, for example, in the specification and claims, should in all cases be understood to be modified by the term “about.” Therefore, unless indicated otherwise, the numerical parameters set forth in the following specification and appended claims are approximations that can be varied according to the desired properties obtained by the invention. At least, and without attempting to limit the application of the equivalence principle to the scope of the claims, each numerical parameter should be interpreted at least according to the number of significant figures reported and by applying ordinary rounding techniques.

[0007] Although the numerical ranges and parameters illustrating the broad scope of the invention are approximate, the values ​​described in the specific examples are reported as precisely as possible. However, any numerical value inherently contains some error that is necessarily caused by the standard deviation found in its corresponding test measurement results.

[0008] Furthermore, it should be understood that any numerical range described herein is intended to include all subranges thereof. For example, the range “1 to 10” is intended to include all subranges between (and including) the stated minimum value of 1 and the stated maximum value of 10, that is, a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0009] In this application, unless otherwise specifically stated, the use of the singular includes the plural and the plural encompasses the singular. Additionally, in this application, unless otherwise specifically stated, the use of “or” means “and / or,” even if “and / or” may be explicitly used in certain circumstances. Furthermore, in this application, unless otherwise specifically stated, the use of “a” or “an” means “at least one / a.” For example, “a” melamine resin, “a” polymer, “a” coating composition, etc., refer to one or more of any of these items.

[0010] This invention relates to a coating composition comprising a melamine resin and at least one polymer reactive with the melamine resin. As used herein, "melamine resin" refers to a resin having melamine rings capped with a plurality of hydroxyl groups derived from formaldehyde. Further, the terms "resin" and "polymer" are used interchangeably. As used herein, the term "polymer" refers to oligomers, homopolymers (e.g., prepared from a single monomer species), copolymers (e.g., prepared from at least two monomer species), terpolymers (e.g., prepared from at least three monomer species), and graft polymers.

[0011] The melamine resin used in this invention can be a resin obtained by addition condensation of melamine with formaldehyde using methods known in the art, or a resin obtained by further addition condensation of such resin with various alcohols such as methanol, butanol, and / or isobutanol. Further, the melamine resin used with this invention includes imino functional groups and hydroxymethyl functional groups. The imino and hydroxymethyl functional groups together account for 30 mol% or more of the total functionality of the melamine resin, or 35 mol% or more of the total functionality of the melamine resin, or 40 mol% or more of the total functionality of the melamine resin, or 50 mol% or more of the total functionality of the melamine resin, or 55 mol% or more of the total functionality of the melamine resin, or 60 mol% or more of the total functionality of the melamine resin, or 70 mol% or more of the total functionality of the melamine resin, or 80 mol% or more of the total functionality of the melamine resin, or 90 mol% or more of the total functionality of the melamine resin, or up to 100 mol% or more of the total functionality of the melamine resin. The imino functional group and the hydroxymethyl functional group may together comprise an amount in the range of, for example, 30 mol% to 80 mol%, or 40 mol% to 80 mol%, or 50 mol% to 70 mol% of the total functionality of the melamine resin.

[0012] It is understood that the amount of imino functional groups on melamine resin can be greater than the amount of hydroxymethyl functional groups on melamine resin. Alternatively, the amount of hydroxymethyl functional groups on melamine resin can be greater than the amount of imino functional groups on melamine resin.

[0013] Through quantitative 13 The molar percentage of functional groups on melamine resin was determined by C-NMR. Quantitative measurements were obtained using a BRUKER AVANCE II spectrometer (manufactured by Bruker, Billerica, MA) operating at a carbon frequency of 75.48 MHz NMR. 13 C10-NMR data. Dimethyl sulfoxide-d6 (DMSO-d6) was used as the NMR solvent. Cr(acac)3 was used for quantification.13 The relaxation agent for C NMR was recorded with a relaxation time of 3 seconds, a pulse angle of 90°, and an acquisition time of 0.66 seconds. A possible structure of melamine resin is shown below. Each triazine ring is substituted with six functional groups. In the structure shown below, the triazine is substituted with one imino (-NH), one hydroxymethyl (-CH2OH), two methoxy (-CH2OMe), one n-butoxy (-CH2OBu), and one isobutyl (-CH2OisoBu). A portion of the six functional groups on each triazine ring can be bridges (commonly referred to as crosslinks) with other triazine rings. To calculate the percentage of imino or hydroxymethyl functional groups on the melamine, these bridges should still be considered functional groups. Specifically, as will be seen below, because the level of imino cannot be determined by... 13 Therefore, the level of the imine group must be determined by the difference between the theoretically six functional groups per triazine ring and the levels of other functional groups (which can be directly determined). When performing this calculation, factors that can be directly determined should be included. 13 C-NMR determines the bridging groups at different levels.

[0014]

[0015] Characteristics of typical substituents 13 Examples of C-NMR peaks are 55 ppm (-OMe), 28 ppm (isoBu), 90 ppm (bridged or crosslinked), and 13 / 31.5 / 64 ppm (-nBu). The carbon peak of -NCH2OH appears in the range of 66 ppm to 70 ppm, and the carbon peak of -NCH2OR appears in the range of 70-79 ppm (where R contains an alkoxy group or a bridging group to another triazine ring). Furthermore, the carbon peaks of -NCH2OH / -NCH2OR can overlap with substituent or solvent peaks. Figure 1a and 1b For example, in RESIMENE HM2608 (melamine-formaldehyde resin, available from INEOS (London, UK)). 13 In the C10 NMR spectrum, the isobutanol solvent overlaps with the -NCH2OH carbon. Therefore, these peaks from substituents or solvents need to be considered in calculating the molar percentage of imino or hydroxymethyl groups.

[0016] When using 13 When calculating the percentage of melamine functional groups as imino and / or hydroxymethyl groups using C-NMR data, the triazine ring carbon (166 ppm) was normalized relative to 3. Theoretically, there are 6 substituents for each triazine ring. After normalizing the triazine ring carbon relative to 3, the molar percentages of NH and hydroxymethyl were calculated based on peak intensities.

[0017] Used for these melamines 13 C-NMR revealed the following two previously described processes for melamine: RESIMENE HM 2608 and CYMEL 202 (melamine-formaldehyde resin, commercially available from Allnex (Frankfurt, Germany), and the processes are shown in... Figure 1a (RESIMENE HM 2608) and Figure 1b (CYMEL 202)

[0018] The mol% of imino groups is calculated using the following Equation 1: Imine mol% = 100 x (6 – I- NCH2OR –I- NCH2OH ) / 6. Further, the molar percentage of hydroxymethyl is calculated using Equation 2: Hydroxymethyl molar percentage = 100 x (I- NCH2OH ) / 6.

[0019] Regarding equations 1 and 2, R is an alkyl group and I... -NCH2OR For –N C The peak intensity of H2OR carbon, which can be detected by I- NCH2OR =I (70-79ppm) –I -异Bu取代基(28ppm) Obtain. Furthermore, I -NCH2OH For –N C The peak intensity of H2OH carbon, which can be obtained through I -NCH2OH =I (66-70ppm) –I -nBu取代基(31.5ppm) –I -异丁醇(30.5ppm) get.

[0020] Regarding RESIMENE HM 2608, the molar percentage of imino groups is calculated using Equation 1 as follows: Imino molar percentage = 100 x (6 – I -NCH2OR –I -NCH2OH ) / 6=100x[6–(3.55-0.12)–(1.19-0.55)] / 6=32.2%. Regarding RESIMENE HM 2608, the molar percentage of hydroxymethyl is calculated using Equation 2 as follows: Hydroxymethyl molar percentage = 100x(I) / 6=32.2%. -NCH2OH ) / 6 = 100x(0.64) / 6 = 10.7%.

[0021] Regarding CYMEL 202, the molar percentage of imino groups is calculated using Equation 1 as follows: Imino molar percentage = 100 x (6 – I -NCH2OR –I -NCH2OH ) / 6=100x[6–2.59–(1.93-1.23)] / 6=45.2%. Regarding CYMEL 202, the molar percentage of hydroxymethyl is calculated using Equation 2 as follows: Hydroxymethyl molar percentage = 100x(I-NCH2OH ) / 6 = 100x(0.7) / 6 = 11.7%.

[0022] The method for determining the mol% of functional groups on melamine resins, as previously described, is referred to herein as the "melamine functional group mol% method." It will be understood that the presence of other components or other types of substituents or solvents can produce additional peaks or interfering peak integrals not described above, for example, 13 N in C-NMR C H2OR carbon (70-79ppm), and the contributions of the other components or the other types of substituents or solvents will be considered for the calculation of imino and hydroxymethyl functionalities.

[0023] It should be understood that when the imino and hydroxymethyl functional groups together account for less than 100 mol% of the total functionality of the melamine resin, one or more other functional groups constitute the remaining mol% of the total functionality of the melamine resin. Non-limiting examples of other functional groups include methoxy (-CH2OMe), n-butoxy (-CH2OBu), isobutoxy, and combinations thereof. Alternatively, the melamine resin may be free of all other functional groups except for the imino and hydroxymethyl functional groups. In such examples, the imino and hydroxymethyl functional groups together account for 100 mol% of the total functionality of the melamine resin.

[0024] The molar percentage of functional groups on melamine that are bridged (or cross-linked) with other triazine rings can also be determined by... 13 C-NMR characterization is used to determine this. The molar percentage of functional groups on melamine that are bridged (or crosslinked) with other triazine rings can be less than 10 mol% of the total functionality of the melamine resin, or less than 5 mol% of the total functionality of the melamine resin, or less than 3 mol% of the total functionality of the melamine resin, or less than 2 mol% of the total functionality of the melamine resin.

[0025] Based on the total resin solids of the coating composition, the melamine resin of the present invention may comprise at least 5% by weight, 10% by weight, or at least 15% by weight. Based on the total resin solids of the coating composition, the melamine resin of the present invention may also comprise at most 40% by weight, at most 35% by weight, or at most 30% by weight. Based on the total resin solids of the coating composition, the melamine resin of the present invention may further comprise an amount in the range of 5% to 40% by weight, or 15% to 30% by weight, or 5% to 35% by weight, or 10% to 35% by weight.

[0026] As indicated, the coating composition further includes at least one polymer reactive with the melamine resin. The polymer reactive with the melamine resin is obtained from a component comprising polytetrahydrofuran and a carboxylic acid or its anhydride. The carboxylic acid or anhydride can be selected from various types of polycarboxylic acids or their anhydrides, such as those selected from dicarboxylic acids or their anhydrides, or from polycarboxylic acids or their anhydrides having three or more carboxylic acid groups. The carboxylic acid or its anhydride can also be selected from compounds having aromatic ring or aliphatic structures. As used herein, the term "aromatic group" refers to a cyclic conjugate hydrocarbon whose stability (due to delocalization) is significantly greater than the assumed stability of a localized structure. Further, the term "aliphatic" refers to a non-aromatic straight-chain, branched, or cyclic hydrocarbon structure containing saturated carbon bonds.

[0027] Non-limiting examples of carboxylic acids include glutaric acid, succinic acid, malonic acid, oxalic acid, trimellitic acid, phthalic acid, isophthalic acid, hexahydrophthalic acid, adipic acid, maleic acid, and combinations thereof. As indicated, acid anhydrides, such as the anhydrides of any of the carboxylic acids previously described, may be used. Non-limiting examples of such acid anhydrides include trimellitic anhydride, phthalic anhydride, maleic anhydride, succinic anhydride, malonic anhydride, oxalic anhydride, hexahydrophthalic anhydride, adipic anhydride, and combinations thereof.

[0028] As indicated, a carboxylic acid or its anhydride may be selected from compounds having an aromatic ring or an aliphatic structure. For example, a carboxylic acid or its anhydride may be selected from aromatic compounds in which the carboxylic acid or anhydride functional group is directly bonded to the aromatic ring such that there is no interrupting atom between the aromatic ring and the attached carboxylic acid or anhydride functional group (a non-limiting example is trimellitic anhydride).

[0029] Polymers reactive with melamine resins can also be prepared using components other than the previously described polytetrahydrofuran and carboxylic acids or their anhydrides. Non-limiting examples of other components that can be used to form the polymer include polyols other than polytetrahydrofuran, other compounds containing one or more carboxylic acid groups or their anhydrides, olefinic unsaturated compounds, polyisocyanates, and combinations thereof.

[0030] As used herein, “olefin unsaturated” means a group having at least one carbon-carbon double bond. Non-limiting examples of olefin unsaturated groups include, but are not limited to, (meth)acrylate groups, vinyl groups, and combinations thereof. As used herein, the term “(meth)acrylate” refers to both methacrylates and acrylates.

[0031] Examples of polyols include glycols, polyether polyols, polyester polyols, copolymers thereof, and combinations thereof. Non-limiting examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-butanediol, tetramethylene glycol, hexamethylene glycol, and combinations thereof, as well as other compounds comprising two or more hydroxyl groups and combinations of any of the foregoing substances. Non-limiting examples of suitable polyether polyols, other than polytetrahydrofuran, include polyethylene glycol, polypropylene glycol, polybutanediol, and combinations thereof.

[0032] Other suitable polyols include, but are not limited to, cyclohexanediol, 2-ethyl-1,6-hexanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, trimethylolpropane, 1,2,6-hexanetriol, glycerol, and combinations thereof. It should be understood that polyols may be selected from diols and / or compounds having three or more hydroxyl groups.

[0033] The additional compound containing one or more carboxylic acid groups or anhydrides may comprise any of the carboxylic acids and anhydrides previously described, provided that the additional compound is different from the first carboxylic acid or anhydride. For example, the component forming the polymer that is reactive with melamine resin may comprise both trimellitic anhydride and maleic anhydride.

[0034] Non-limiting examples of olefinic unsaturated monomers include, but are not limited to, alkyl esters of (meth)acrylic acid, hydroxyalkyl esters of (meth)acrylic acid, olefinic unsaturated monomers containing acid groups, vinyl aromatic monomers, and combinations thereof.

[0035] Non-limiting examples of alkyl esters of (meth)acrylic acid include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, ethylhexyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, glycidyl (meth)acrylate, isononyl (meth)acrylate, isodecanyl (meth)acrylate, vinyl (meth)acrylate, acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, and combinations thereof. Other non-limiting examples include alkyl diesters of di(meth)acrylate formed by the condensation of two equivalents of (meth)acrylic acid, such as ethylene glycol di(meth)acrylate. C64-dimethacrylates such as butanediol and hexanediol may also be used. 2-24 Alkyl di(meth)acrylate formed from diols.

[0036] Non-limiting examples of hydroxyalkyl esters of (meth)acrylic acid include hydroxymethyl ester (meth)acrylic acid, hydroxyethyl ester (meth)acrylic acid, hydroxypropyl ester (meth)acrylic acid, hydroxybutyl ester (meth)acrylic acid, and combinations thereof.

[0037] Non-limiting examples of olefinic unsaturated monomers containing acid groups include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aspartic acid, malic acid, mercaptosuccinic acid, and combinations thereof.

[0038] Non-limiting examples of vinyl aromatic monomers include styrene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, vinylnaphthalene, vinyltoluene, divinylbenzene, and combinations thereof.

[0039] Non-limiting examples of suitable polyisocyanates include isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate (H12MDI), cyclohexyl diisocyanate (CHDI), m-tetramethylxylene diisocyanate (m-TMXDI), p-tetramethylxylene diisocyanate (p-TMXDI), ethylene diisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropane, 1,6-diisocyanate... Hexane cyanate (hexamethylene diisocyanate or HDI), 1,4-butene diisocyanate, lysine diisocyanate, 1,4-methylene bis-(cyclohexyl isocyanate), toluene diisocyanate (TDI), m-xylene diisocyanate (MXDI) and p-xylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 1,5-tetrahydro-naphthalene diisocyanate, 4,4'-dibenzyl diisocyanate and 1,2,4-benzenetriisocyanate, xylene diisocyanate (XDI) and mixtures or combinations thereof.

[0040] It should be understood that the optional additional components described above can be used to modify or adjust the properties of the polymer and the final coating formed therefrom. For example, the polymer can be formed from additional components, such as additional polyols, which can provide faster curing at lower baking temperatures, such as 80°C or lower.

[0041] The polytetrahydrofuran used to form the polymer may comprise more than 20% by weight, or more than 30% by weight, or more than 40% by weight of the polymer-forming component. The polytetrahydrofuran may also comprise up to 50% by weight, or up to 60% by weight, or up to 70% by weight, or up to 80% by weight, or up to 90% by weight of the polymer-forming component. The polytetrahydrofuran may further comprise amounts ranging from 20% to 90% by weight, or 40% to 80% by weight, or 50% to 70% by weight, or 30% to 40% by weight of the polymer-forming component.

[0042] The carboxylic acid or anhydride used to form the polymer may constitute more than 13% by weight or more than 15% by weight of the components forming the polymer. The carboxylic acid or anhydride may also constitute up to 21% by weight or up to 18% by weight of the components forming the polymer. The carboxylic acid or anhydride used to form the polymer may constitute from 13% to 21% by weight of the components forming the polymer.

[0043] It should be understood that one or more of the other components described above may constitute the remaining amount of the components used to form a polymer that is reactive with melamine resin. For example, the polymer may be prepared from polytetrahydrofuran, carboxylic acids or anhydrides, polyols other than polytetrahydrofuran, and other carboxylic acids or anhydrides other than the first carboxylic acid or anhydride.

[0044] The polymers prepared from the previously described components include at least ether bonds and carboxylic acid functional groups. The resulting polymers may also include ester bonds and / or urethane bonds, as well as additional functional groups such as hydroxyl functional groups. For example, the resulting polymers may include ether bonds, ester bonds, carboxylic acid functional groups, and hydroxyl functional groups. The resulting polymers may also include additional bonds and functional groups, including, but not limited to, the additional functional groups previously described.

[0045] Polymers that are reactive with melamine resins may include polymer core-shell particles in which the polymer core is at least partially enclosed by a polymer shell, self-emulsifying dispersion polymers, or combinations thereof.

[0046] If the polymer reactive with melamine resin does not contain core-shell particles, the acid value of the polymer, based on the total resin solids, can be at least 40, or at least 42, or at least 45, or at least 47, or at least 49, or at least 50. If the polymer reactive with melamine resin does not contain core-shell particles, the acid value of the polymer, based on the total resin solids, can be at most 60, or at most 57, or at most 55, or at most 53, or at most 51, or at most 50. If the polymer reactive with melamine resin does not contain core-shell particles, the acid value of the polymer, based on the total resin solids, can be in the range of 40 to 60, or 42 to 57, or 45 to 55, or 47 to 53, or 49 to 51. The acid value is determined as described in the examples.

[0047] Polymers reactive with melamine resin may include polymeric core-shell particles, wherein at least a portion of the polymeric shell of the core-shell particles is covalently bonded to at least a portion of the polymeric core of the core-shell particles. The polymeric shell of the core-shell particles may be obtained from components comprising greater than 20% by weight of polytetrahydrofuran and greater than 13% by weight of a carboxylic acid or its anhydride. Based on the total resin solids of the polymer, the acid value of the polymeric shell may be at least 40, or at least 42, or at least 45, or at least 47, or at least 49, or at least 50. Based on the total resin solids of the polymer, the acid value of the polymeric shell may be at most 60, or at most 57, or at most 55, or at most 53, or at most 51, or at most 50. Based on the total resin solids of the polymer, the acid value of the polymeric shell may be in the range of 40 to 60, or 42 to 57, or 45 to 55, or 47 to 53, or 49 to 51.

[0048] To determine the acid value of the polymer shell, the polymer shell can first be synthesized in a step separating it from the polymer core. The polymer shell is synthesized as described herein with respect to polymer (b). After the synthesis of the polymer shell, the acid value of the polymer shell is determined before the formation of the polymer core. The acid value of the polymer shell is determined as described in the examples. Once the acid value of the polymer shell is determined, the polymer shell can be dispersed in water, and the monomers of the polymer core can be added. An initiator can then be added to polymerize the monomers of the polymer core. The polymer shell can be covalently bonded to at least a portion of the polymer core.

[0049] As indicated, core-shell particles include a polymer core and a polymer shell. "Polymer core" means that the core of a core-shell particle comprises one or more polymers, and "polymer shell" means that the shell of a core-shell particle comprises one or more polymers.

[0050] As used herein, a core-shell particle in which the core is at least partially encapsulated by a shell refers to a particle comprising: (i) at least one or more first materials forming the center (i.e., the core) of the particle; and (ii) at least one or more second materials (i.e., the shell) forming a layer over at least a portion of the surface of the first material (i.e., the core). It should be understood that the one or more first materials forming the core are different from the one or more second materials forming the shell. Furthermore, core-shell particles can have various shapes (or morphologies) and sizes. For example, core-shell particles can have generally spherical, cubic, plate-like, polyhedral, or needle-like (elongated or fibrous) morphologies. Core-shell particles can also have an average particle size of 30 to 300 nanometers, or 40 to 200 nanometers, or 50 to 150 nanometers. As used herein, “average particle size” refers to the volume average particle size. The average particle size can be determined, for example, using a ZETASIZER 3000HS manufactured by Malvern Instruments (Worcestershire, United Kingdom) according to the instructions in the ZETASIZER 3000HS manual.

[0051] The polymer shell of the core-shell particles can be obtained from the previously described components, including polytetrahydrofuran, its carboxylic acids or anhydrides, hydroxyl-functionalized olefinic unsaturated compounds, and optionally other additional components (e.g., additional polyols, additional carboxylic acids and / or anhydrides, polyisocyanates, and / or combinations thereof). Further, the polymer core typically comprises an addition polymer derived from an olefinic unsaturated monomer.

[0052] Polytetrahydrofuran may include amounts ranging from 20% to 90% by weight of the component forming the polymer shell, or from 40% to 80% by weight of the component forming the polymer shell, or from 50% to 70% by weight of the component forming the polymer shell, or from 55% to 65% by weight of the component forming the polymer shell.

[0053] The carboxylic acid or anhydride may be in an amount ranging from 13% to 21% by weight of the component forming the polymer shell, or from 15% to 18% by weight of the component forming the polymer shell, or from 17% to 19% by weight of the component forming the polymer shell.

[0054] The polymer shell can also be covalently bonded to at least a portion of the polymer core. For example, the polymer shell can be covalently bonded to the polymer core by reacting at least one functional group on the monomer and / or prepolymer used to form the polymer shell with at least one functional group on the monomer and / or prepolymer used to form the polymer core. The functional group can include any of the previously described functional groups, provided that at least one functional group on the monomer and / or prepolymer used to form the polymer shell is reactive with at least one functional group on the monomer and / or prepolymer used to form the polymer core. For example, the monomers and / or prepolymers used to form both the polymer shell and the polymer core can each include at least one olefinically unsaturated group that reacts with each other to form a chemical bond. As used herein, "prepolymer" refers to a polymer precursor capable of further reaction or polymerization by one or more reactive groups to form a higher molecular weight or cross-linked state.

[0055] When the polymer shell and polymer core are covalently bonded, the acid value of the core-shell particles may be lower than that of the polymer shell (considered alone) due to the presence of the polymer core. The acid value of the core-shell particles can be calculated by multiplying the acid value of the polymer shell, as described in the examples, by the weight percentage of the polymer shell present in the core-shell particles. For example, assuming the acid value of the polymer core is 0, if the determined acid value of the polymer shell is 50, and the core-shell particles account for 50% by weight of the polymer shell, then the acid value of the core-shell particles will be 50. * (0.5) = 25.

[0056] A portion of the polymer shell may not react with the polymer core to form core-shell particles. Therefore, the coating composition may include both core-shell particles as described herein and a polymer shell polymer that is not bonded to the polymer core.

[0057] Core-shell particles containing polymeric cores and shells can be prepared to provide hydrophilic polymeric shells and hydrophobic polymeric cores with enhanced water dispersibility / stability. As used herein, the term "hydrophilic" refers to polymers, monomers, and other materials that have an affinity for water and will be dispersed or dissolved in water or other aqueous media. Hydrophilic materials, such as hydrophilic polymers, typically have water-dispersible groups. A "water-dispersible group" refers to a group having one or more hydrophilic functional groups or groups formed therefrom that have an affinity for water and facilitate the dispersion of compounds such as polymers in water or other aqueous media. Further, as used herein, the term "hydrophobic" refers to polymers, monomers, and other materials that lack an affinity for water or other aqueous media and tend to repel water or other aqueous media, are insoluble or dispersed in water or other aqueous media, and / or are not wetted by water or other aqueous media. Hydrophobic materials, such as hydrophobic polymers, typically do not contain water-dispersible groups.

[0058] As indicated, polymeric cores and shells of core-shell particles can be prepared to provide hydrophilic polymeric shells and hydrophobic polymeric cores with enhanced water dispersibility / stability. Thus, the polymeric shell may include hydrophilic water-dispersible groups, while the polymeric core may be free of such groups. The hydrophilic water-dispersible groups can improve the water dispersibility / stability of the polymeric shell in aqueous media, such that the polymeric shell at least partially encapsulates the hydrophobic core.

[0059] As previously described, the water-dispersible group includes one or more hydrophilic functional groups. For example, the polymer forming the hydrophilic polymer shell may include ionic or ionizable groups, such as carboxylic acid functional groups or salts thereof. The carboxylic acid functional groups may be at least partially neutralized (i.e., at least 30% of the total neutralization equivalent) by a base such as a volatile amine to form a salt group. Volatile amines are amine compounds with an initial boiling point less than or equal to 250°C as measured at standard atmospheric pressure of 101.3 kPa. Suitable examples of volatile amines are ammonia, dimethylamine, trimethylamine, monoethanolamine, and dimethylethanolamine. It should be understood that the amine may evaporate during coating formation to expose the carboxylic acid functional groups and allow the carboxylic acid functional groups to undergo further reactions. Other non-limiting examples of water-dispersible groups include polyoxyalkylene groups, such as those obtained by using polyethylene / propylene glycol ether materials.

[0060] As indicated, polymers reactive with melamine resins may include self-emulsifying dispersion polymers. As used herein, a “self-emulsifying dispersion polymer” means a polymer that contains hydrophilic functional groups and is not initially synthesized as an aqueous dispersion but is then mixed with water to form an aqueous dispersion.

[0061] The self-emulsifying dispersion polymers of the present invention can be obtained from the previously described components, including polytetrahydrofuran, carboxylic acids or anhydrides, and optionally other additional components (e.g., additional polyols, additional carboxylic acids or anhydrides, polyisocyanates, olefinic unsaturated compounds, and / or combinations thereof). For example, self-emulsifying dispersion polymers are typically prepared using polytetrahydrofuran, carboxylic acids or anhydrides, polyols different from polytetrahydrofuran, and another carboxylic acid or anhydride different from the first carboxylic acid or anhydride.

[0062] Polytetrahydrofuran may include amounts ranging from 20% to 90% by weight of the component forming the self-emulsifying dispersion polymer, or from 40% to 80% by weight of the component forming the self-emulsifying dispersion polymer, or from 50% to 70% by weight of the component forming the self-emulsifying dispersion polymer, or from 80% to 90% by weight of the component forming the self-emulsifying dispersion polymer.

[0063] The carboxylic acid or anhydride may be in an amount ranging from 13% to 21% by weight of the component forming the self-emulsifying dispersion polymer, or from 15% to 18% by weight of the component forming the self-emulsifying dispersion polymer, or from 14% to 16% by weight of the component forming the self-emulsifying dispersion polymer.

[0064] As indicated, the polymers reactive with melamine resin may include both the previously described polymer core-shell particles and self-emulsifying dispersion polymers. When the coating composition of the present invention includes both polymer core-shell particles and self-emulsifying dispersion polymers, the coating composition may include a greater amount of polymer core-shell particles than the amount of self-emulsifying dispersion polymer, or the amount of self-emulsifying dispersion polymer may be greater than the amount of polymer core-shell particles.

[0065] The pKa of the acid functionality of polymers (and / or the polymer shell itself) that are reactive with melamine resin can be less than 5, or less than 4, or less than 3.5, or less than 3, or less than 2.5, or less than 2. The pKa of the acid functionality of polymers that are reactive with melamine resin can be in the range of 1.5 to 4.5. The pKa value is the negative (decimal) logarithm of the acid dissociation constant and is determined by titration according to the method described in Section 8.2.1 of Lange's Handbook of Chemistry, 15th edition.

[0066] The carboxylic acid functional groups found on the polymer may be provided solely by the first carboxylic acid or anhydride. Alternatively, when the polymer is formed using other carboxylic acid functional compounds and / or anhydrides, the carboxylic acid functional groups found on the polymer are provided by the first carboxylic acid or anhydride and other carboxylic acid functional compounds and / or anhydrides.

[0067] The polymer (and / or the polymer shell itself) may also include 1,500 to 5,000 or 2,000 to 3,000 hydroxyl equivalents, as measured by reacting the dried polymer with an excess of acetic anhydride and titrating with potassium hydroxide according to ASTM E222-17.

[0068] Based on the total resin solids of the coating composition, the polymer reactive with melamine resin may comprise at least 50%, 60%, or at least 70% by weight. Based on the total resin solids of the coating composition, the polymer reactive with melamine resin may also comprise up to 90% by weight or up to 80% by weight. Based on the total resin solids of the coating composition, the polymer reactive with melamine resin may further comprise an amount in the range of 50% to 90% by weight, or 60% to 80% by weight, or 70% to 80% by weight, or 70% to 90% by weight.

[0069] It should be understood that melamine resin, polymers reactive with melamine resin, and other optional components described herein are dispersed in an aqueous medium. As used herein, "aqueous medium" means a liquid medium comprising more than 50% by weight of water based on the total weight of the liquid medium. Based on the total weight of the liquid medium, such an aqueous liquid medium may, for example, comprise at least 60% by weight of water, or at least 70% by weight of water, or at least 80% by weight of water, or at least 90% by weight of water, or at least 95% by weight of water, or 100% by weight of water. Solvents constituting less than 50% by weight of the liquid medium (if present) comprise organic solvents. Non-limiting examples of suitable organic solvents include polar organic solvents, such as protonated organic solvents, such as ethylene glycol, ethylene glycol ether alcohols, alcohols, volatile ketones, ethylene glycol diethers, esters, and diesters. Other non-limiting examples of organic solvents include aromatic and aliphatic hydrocarbons.

[0070] The coating composition may include additional materials, including, but not limited to, additional resins, such as additional film-forming resins and additional crosslinking agents. As used herein, "film-forming resin" means a resin that, when used in a coating composition, can form a self-supporting continuous film on at least a horizontal surface by dehydration and / or during curing. The term "dehydration" means the removal of water and / or other solvents. It should be understood that dehydration may also cause the resin material to at least partially cure. Further, the terms "curable," "curable," etc., mean that at least a portion of the resin material in the composition is crosslinked or crosslinkable.

[0071] The additional resin may comprise any of the various thermoplastic and / or thermosetting film-forming resins known in the art. The term "thermosetting" refers to a resin that is irreversibly "cured" upon curing or crosslinking, wherein the polymer chains of the resin are covalently linked together. Once cured or crosslinked, thermosetting resins will not melt upon application of heat and are insoluble in solvents. As indicated, the film-forming resin may also comprise thermoplastic film-forming resins. The term "thermoplastic" refers to a resin that is not covalently linked and thus can flow as a liquid upon heating and is soluble in certain solvents.

[0072] Suitable other examples of resins, without limitation, include polyurethanes, polyesters such as polyester polyols, polyamides, polyethers, polysiloxanes, fluoropolymers, polysulfides, polysulfides, polyureas, (meth)acrylic resins, epoxy resins, vinyl resins, and combinations thereof. Other resins may also include particulate resins and non-particulate resins.

[0073] Other resins may have any of a variety of reactive functional groups, including, but not limited to, carboxylic acid groups, amino groups, epoxy groups, hydroxyl groups, thiols, urethane groups, amide groups, urea groups, isocyanate groups (including terminally capped isocyanate groups), (meth)acrylate groups, and combinations thereof. Thermosetting coating compositions typically include a crosslinking agent, which may be selected from any crosslinking agents known in the art, to react with the functional groups of the resin used in the coating composition. Alternatively, thermosetting film-forming resins having self-reactive functional groups may be used, in such a way that these thermosetting resins are self-crosslinking.

[0074] As indicated, the coating composition may also include additional crosslinking agents. As used herein, the term "crosslinking agent" and similar terms refer to a molecule comprising two or more functional groups that are reactive with other functional groups and capable of chemically linking two or more monomer or polymer molecules. Non-limiting examples of crosslinking agents include polyhydrazides, carbodiimides, polyols, phenolic resins, epoxy resins, β-hydroxy(alkyl)amide resins, hydroxy(alkyl)urea resins, oxazoline, alkylated urethane resins, (meth)acrylates, isocyanates, terminally capped isocyanates, polybasic acids, acid anhydrides, organometallic acid functional materials, polyamines, polyamides, amino plastics (different from the melamine resins previously described), aziridine, and combinations thereof. The coating compositions of the present invention may also be free of additional film-forming resins and / or crosslinking agents, such as polyisocyanates.

[0075] The coating composition may also contain other additional materials, such as colorants. As used herein, "colorant" means any substance that imparts color and / or other opacity and / or other visual effects to the composition. Colorants may be added to the coating in any suitable form, such as discrete particles, dispersions, solutions, and / or flakes. A single colorant or a mixture of two or more colorants may be used in the coatings of the present invention.

[0076] Example colorants comprise pigments (organic or inorganic), dyes, and colorants, such as those used in the paint industry and / or listed in the Dry Color Manufacturers Association (DCMA), as well as special effects compositions. Colorants may comprise, for example, finely divided solid powders that are insoluble but wettable under the conditions of use. Colorants may be organic or inorganic and may be agglomerated or non-agglomerated. Colorants can be incorporated into coatings using a grinding vehicle, such as an acrylic grinding vehicle, the use of which is well known to those skilled in the art.

[0077] Example pigments and / or pigment compositions include, but are not limited to, carbazole dioxazine crude pigments, azo, monoazo, diazo, naphthol AS, salt types (flakes), benzimidazolone, isoindolineone, isoindoline and polycyclic phthalocyanine, quinacridone, perylene, perinone, diketopyrrolopyrrole, thioindigo, anthraquinone, indigoanthraquinone, anthraquinone pyrimidine, flavinthrone, pinanthraquinone, anthraquinone, dioxazine, triarylcarbium, quinophthalone pigments, diketopyrrolopyrrole red (“DPPBO Red”), titanium dioxide, carbon black, and mixtures thereof. The terms “pigment” and “coloring filler” are used interchangeably.

[0078] Example dyes include, but are not limited to, solvent-based dyes and / or water-based dyes, such as phthalocyanine green or phthalocyanine blue, iron oxide, and bismuth vanadate.

[0079] Example colorants include, but are not limited to, pigments dispersed in a water-based or water-miscible carrier, such as AQUA-CHEM 896, available from Evonik Industries (Essen, Germany), and CHARISMA COLORANTS and MAXITONERINDUSTRIAL COLORANTS, available from the Accurate Dispersions Division of Eastman Chemical (South Holland, IL).

[0080] Colorants that can be used with the coating compositions of the present invention may also include special effect compositions or pigments. As used herein, “special effect composition or pigment” means a composition or pigment that interacts with visible light to provide an appearance effect other than or excluding a continuous, unchanging color. Example special effect compositions and pigments include those that produce one or more appearance effects such as reflectivity, pearlescent, metallic sheen, texture, phosphorescence, fluorescence, photochromism, photosensitivity, thermochromism, goniochromism, and / or color change. Non-limiting examples of special effect compositions may include transparent coated mica and / or synthetic mica, coated silica, coated alumina, aluminum flakes, transparent liquid crystal pigments, liquid crystal coatings, and combinations thereof.

[0081] Other non-limiting examples of additional materials that may optionally be used with the coating compositions of the present invention include plasticizers, abrasion-resistant particles, antioxidants, hindered amine light stabilizers, UV absorbers and stabilizers, surfactants, flow and surface control agents, thixotropic agents, catalysts, reaction inhibitors, and other conventional additives.

[0082] It should be understood that the components forming the coating composition can be selected to form a one-component composition (“1K”). As used herein, a “one-component composition” means a composition in which all coating components remain in the same container after manufacturing, during storage, etc. In contrast, multi-component compositions, such as two-component compositions (“2K”) or more component compositions having at least two components, are maintained in different containers after manufacturing, during storage, etc., prior to application and coating on a substrate. Therefore, the coating composition may not contain components typically used to form multi-component compositions, such as polyisocyanates.

[0083] The coating composition of the present invention can be deposited on at least a portion of a substrate and dehydrated and / or cured to form a coating.

[0084] The substrates on which the coating composition can be applied include a wide range of substrates. For example, the coating composition of the present invention can be applied to vehicle substrates, industrial substrates, aerospace substrates, etc.

[0085] The vehicle substrate may contain components of a vehicle. In this disclosure, the term "vehicle" is used in its broadest sense and includes all types of aircraft, spacecraft, watercraft, and land vehicles. For example, a vehicle may include, but is not limited to, aerospace substrates (components of aerospace vehicles, such as aircraft, like airplanes (e.g., private jets, and small, medium, or large commercial passenger aircraft, cargo aircraft, and military aircraft), helicopters (e.g., private, commercial, and military helicopters), aerospace vehicles (e.g., rockets and other spacecraft), etc.). Vehicles may also include land vehicles, such as animal trailers (e.g., horse-drawn carriages), all-terrain vehicles (ATVs), automobiles, trucks, buses, vans, heavy equipment, tractors, golf carts, motorcycles, bicycles, snowmobiles, trains, railway vehicles, etc. Vehicles may also include watercraft, such as ships, boats, hovercraft, etc. The vehicle substrate can include vehicle body components, such as car hoods, doors, trunks, roofs, etc.; such as wings and fuselages of aircraft or spacecraft; such as the hulls of watercraft.

[0086] The coating composition can be applied to an industrial substrate, which may include tools, heavy equipment, furniture such as office furniture (e.g., office chairs, tables, filing cabinets, etc.), appliances such as refrigerators, ovens and stoves, dishwashers, microwave ovens, washing machines, dryers, small appliances (e.g., coffee makers, slow cookers, pressure cookers, blenders, etc.), metal hardware, extruded metals such as extruded aluminum for window frames, and other interior and exterior metal building materials.

[0087] The coating composition can be applied to: storage tanks, windmills, nuclear power plant components, packaging substrates, wood flooring and furniture, clothing, electronic devices (including housings and circuit boards), glass and transparent sheets, sports equipment (including golf balls), stadiums, buildings, bridges, etc.

[0088] The substrate can be metallic or non-metallic. Metallic substrates include, but are not limited to, tin, steel (including electro-galvanized steel, cold-rolled steel, hot-dip galvanized steel, etc.), aluminum, aluminum alloys, zinc-aluminum alloys, steel coated with zinc-aluminum alloys, and aluminized steel. Non-metallic substrates include polymeric materials, plastics and / or composites, polyesters, polyolefins, polyamides, cellulose, polystyrene, polyacrylic acid, polyethylene naphthalate, polypropylene, polyethylene, nylon, ethylene vinyl alcohol (EVOH), polylactic acid, other "green" polymeric substrates, polyethylene terephthalate ("PET"), polycarbonate, polycarbonate propylene butadiene styrene ("PC / ABS"), wood, veneer, wood composites, particleboard, medium-density fiberboard, cement, stone, glass, paper, cardboard, textiles, synthetic and natural leather, etc. Substrates can include metals, plastics and / or composites and / or fibrous materials. Fiberic materials can include nylon and / or thermoplastic polyolefin materials with continuous strands or short-cut carbon fibers. The substrate can be a substrate that has been treated in some way, such as to give visual and / or color effects, protective pretreatment, or other coatings.

[0089] The coating compositions of the present invention may be particularly advantageous when applied to metal substrates. The coatings of the present invention may be particularly advantageous when applied to metal substrates used in the manufacture of motor vehicles, such as automobiles, trucks, and tractors.

[0090] The coating compositions of the present invention are particularly advantageous when applied to substrates forming packaging, such as metal substrates forming packaging. Suitable metal packaging substrates include, but are not limited to, food and / or beverage packaging, components for manufacturing such packaging, or monolithic aerosol cans or tubes. Suitable monolithic aerosol cans or tubes include, but are not limited to, deodorant containers and hairspray containers. Monolithic aerosol cans or tubes may be aluminum monolithic aerosol cans or tubes.

[0091] As used herein, “packaging” is any substance intended to contain another article, specifically for transport from the point of manufacture to the consumer, and for subsequent storage by the consumer. Therefore, packaging should be understood as something sealed to prevent its contents from spoiling (until opened by the consumer). Manufacturers typically determine the length of time a food or beverage will not spoil, which generally ranges from several months to several years. Thus, the “packaging” of this invention is distinguished from storage packaging or baking trays in which consumers may prepare and / or store food; such packaging will only maintain the freshness or integrity of the food article for a relatively short period. As used herein, “packaging” means the entire packaging itself or any component thereof, such as ends, lids, caps, etc. For example, “packaging” coated with the coating composition described herein may comprise a metal can, wherein only the end of the can or a portion thereof is coated. Packaging according to the invention can be made of metal or non-metal, such as plastic or laminated materials, and can be of any form. One example of suitable packaging is laminated tubing. Another example of suitable packaging is a metal can. The term "metal can" encompasses any type of metal can, packaging, or reservoir, or part thereof, sealed by a food / beverage manufacturer to minimize or eliminate spoilage of the contents until the consumer opens the package. An example of a metal can is a food can; the term "food can" is used herein to refer to a can, packaging, or reservoir, or part thereof, used for packaging any type of food and / or beverage. "Beverage can" may also be used more specifically to refer to a food can that packages a beverage. The term "metal can" specifically includes food cans, includes beverage cans, and also specifically includes a "can end" comprising an "EZ opening," which is typically stamped from can end material and used in conjunction with food and beverage packaging. The term "metal can" also specifically includes metal caps and / or closures, such as bottle caps, screw caps and lids, snap-on caps, etc., of any size. Metal cans can also be used to contain other items, including, but not limited to, personal care products, pesticides, paints, and any other compounds suitable for packaging in aerosol cans. The cans can include two-piece cans, three-piece cans, and thin-walled stretched one-piece cans; such one-piece cans are commonly used for aerosol products. Packaging coated with the compositions of this invention can also include plastic bottles, plastic tubes, laminates, and flexible packaging, such as those made of PE, PP, PET, etc. Such packaging can hold, for example, food, toothpaste, personal care products, etc.

[0092] The coating compositions of the present invention can be applied to the interior and / or exterior of packaging. For example, the coating can be roll-coated onto metal used in the manufacture of two-piece food cans, three-piece food cans, can end blanks, and / or cap / seal blanks. The coating is applied to rolls or sheets by roll coating; the coating is then cured, and the can end is stamped out to form the finished product, i.e., the can end. The coating can also be applied as an edge coating to the bottom of the can; this application can be done by roll coating. The role of the edge coating is to reduce friction to improve handling during the ongoing manufacture and / or processing of the can. The coating can be applied to the “side stripes” of the metal can, which will be understood as the seams formed during the manufacture of three-piece cans. The coating can also be applied to the cap and / or seal; such application may include, for example, a protective varnish applied before and / or after the cap / seal is formed, and / or a colored enamel applied later to the cap, specifically those with scored seams at the bottom of the cap. Decorated can stock can also be partially coated externally with the coatings described herein, and decorated, coated can stock can also be used to form various metal cans. The coating can be applied to the can blank before the can or can component is formed, or it can be applied to the can or can component after formation. Any material used to form food cans can be treated according to the method of the invention. Particularly suitable substrates include tin-plated steel, tin-free steel, and black-plated steel.

[0093] The coating composition can be applied to at least a portion of a substrate by any standard method in the art, such as spraying, electrostatic spraying, dipping, roller coating, brushing, etc. Once applied, the composition can be dehydrated and / or cured to form a coating. The coating compositions of the present invention can be cured by various methods, including but not limited to applying heat.

[0094] The coating compositions of the present invention have been found to be dehydrated at temperatures ranging from 20°C to 90°C, or 20°C to 80°C, or 20°C to 70°C, or 20°C to 60°C, or 40°C to 80°C, or 40°C to 70°C. The coating compositions can be dehydrated at these temperatures for a period of less than 2 minutes or less than 1 minute. The dehydration period of the coating compositions is a specified dehydration period and does not include the time required to transfer the coating compositions and subject them to another step, such as a curing step.

[0095] The coating composition can also be cured at relatively low temperatures. For example, the coating composition can be cured at 140°C or lower, or 120°C or lower, or 100°C or lower, or 80°C or lower.

[0096] The coatings of this invention have been found to form at lower dehydration / curing temperatures than other coatings typically required for application to substrates, such as those forming packaging or vehicles. The coatings also provide desired appearance and mechanical / chemical properties, such as good solvent resistance.

[0097] This invention also relates to a multilayer coating comprising at least a first base coat and a second base coat. As explained in further detail herein, the multilayer coating may include additional coatings, including, but not limited to, a primer layer, a top coat, or a combination thereof. A “base coat” is a coating deposited on a primer and / or directly onto a substrate, optionally containing components that affect color and / or provide other visual effects (such as pigments). A “top coat” is the uppermost coating deposited on another coating, such as a base coat, to provide a protective and / or decorative layer. A “primer layer” is a bottom coating that can be deposited onto a substrate to prepare the surface for the application of a protective or decorative coating system.

[0098] The first and / or second base coats of the multilayer coating are formed from the coating composition previously described, which includes a melamine resin and at least one polymer reactive with the melamine resin. The coating composition used to form the first and / or second base coats may also contain one or more of the components previously described, such as additional film-forming resins, crosslinking agents, colorants, and / or other optional materials.

[0099] The coating compositions used to form the first and second primer coatings can be the same or different. For example, the first and second primer coatings can each comprise a coating composition comprising a melamine resin and a polymer of the same or different types reactive with the melamine resin (i.e., the previously described polymer core-shell particles and / or self-emulsifying dispersion polymers), such that each layer forms a one-component composition. In some instances, one of the primer coatings can be formed by the previously described coating composition and includes components forming a one-component composition, while the other coating can be formed by components forming a multilayer composition, such as a two-component composition comprising, for example, polyisocyanates and polyol functional resins.

[0100] Alternatively, one of the first or second primer coatings can be formed using different coating compositions. Different coatings can be formed using a variety of components, including the various resins and crosslinking agents previously described, such as those formed with carboxylic acid functional polymer core-shell particles, and various crosslinking agents such as carbodiimide can be used.

[0101] The first and second base coat compositions may also include the same or different additional resins, crosslinking agents, colorants, and other optional materials previously described. For example, the second base coat composition may include special effect pigments, and the first base coat composition may not contain special effect pigments. Thus, the first base coat composition may, for example, include only pigments that impart a continuous, unchanging color, and the second base coat may, for example, include only special effect pigments. Alternatively, the first base coat composition may include special effect pigments, and the second base coat composition may not contain special effect pigments. Thus, the second base coat composition may, for example, include only pigments that impart a continuous, unchanging color, and the first base coat may, for example, include only special effect pigments.

[0102] Both the first and second primer coatings can be formed from a single-component composition as previously described. Alternatively, one of the primer coatings can be formed from a single-component composition, while the other primer coating can be formed from a multi-component composition, such as a two-component composition.

[0103] The first primer composition can be applied directly to at least a portion of the substrate by any standard method in the art, such as spraying, electrostatic spraying, dipping, roller coating, brushing, etc. Then, the second primer composition can be applied directly to at least a portion of the first primer composition as a wet-on-wet process (i.e., before the first primer composition is dehydrated). The second primer composition can be applied by any standard method in the art, such as spraying, electrostatic spraying, dipping, roller coating, brushing, etc. After the second primer composition is applied, both primer compositions can be dehydrated simultaneously. The two primer compositions can be dehydrated simultaneously at 20°C to 90°C, or 20°C to 80°C, or 20°C to 70°C, or 20°C to 60°C, or 40°C to 80°C, or 40°C to 70°C. The coating compositions can be dehydrated at the above temperatures for a period of less than 2 minutes or less than 1 minute, for example.

[0104] The second primer composition can also be applied directly over at least a portion of the dehydrated first primer composition as previously described. The second primer composition can be dehydrated at 20°C to 90°C, or 20°C to 80°C, or 20°C to 70°C, or 20°C to 60°C, or 40°C to 80°C, or 40°C to 70°C. The coating composition can be dehydrated at the aforementioned temperatures for a period of less than 2 minutes or less than 1 minute. After dehydration of the second primer composition, the primer can be cured at a temperature of 140°C or lower, or 120°C or lower, or 100°C or lower, or 80°C or lower.

[0105] Multilayer coatings may also include a topcoat applied over at least a portion of a second base coat before or after the base coat has cured. The topcoat may be formed from a coating composition comprising a film-forming resin, a crosslinking agent, an aqueous or organic solvent medium, and / or any other material as previously described. For example, the topcoat may comprise a film-forming resin and one or more polyisocyanates, such as at least one urea diketone dimer-based polyisocyanate that is reactive with the film-forming resin.

[0106] The topcoat may be a transparent topcoat. As used herein, a “transparent coating” means a coating that is at least substantially transparent or completely transparent. The term “substantially transparent” means a coating in which surfaces other than the coating are at least partially visible to the naked eye when viewed through the coating. The term “completely transparent” means a coating in which surfaces other than the coating are completely visible to the naked eye when viewed through the coating. It should be understood that a transparent topcoat may include colorants such as pigments, provided that the colorants do not interfere with the desired transparency of the transparent topcoat. Alternatively, a transparent topcoat may not contain colorants such as pigments (i.e., pigment-free).

[0107] Non-limiting examples of topcoats that can be used with the multilayer coatings of the present invention include those described in U.S. Patent No. 4,650,718, column 1, line 62 through column 10, line 16; U.S. Patent No. 5,814,410, column 2, line 23 through column 9, line 54; and U.S. Patent No. 5,891,981, column 2, line 22 through column 12, line 37, all of which are incorporated herein by reference. Suitable topcoat compositions that can be used to form the topcoat also comprise compositions commercially available from PPG Industries, Inc. (Pittsburgh, PA) under the trade names NCT, DIAMOND COAT, and CERAMICLEAR.

[0108] As indicated, the top coating can be cured simultaneously with the first and second base coatings. For example, the top and base coatings can be cured at temperatures of 140°C or lower, 120°C or lower, 100°C or lower, or 80°C or lower.

[0109] The multilayer coating according to the invention may further include other optional layers, including, but not limited to, additional base coats and primer coatings as indicated above. The primer coating may be formed over at least a portion of the substrate, and the first or second base coat may be formed over at least a portion of the primer coating. Further, the additional base coat may be prepared from any of the materials previously described. The additional base coat may be applied over, for example, the first or second base coat before the top coat is applied.

[0110] The primer coating, optionally used with the multilayer coating of the present invention, can be formed from a coating composition comprising a film-forming resin, such as a cationic-based resin, anionic-based resin, and / or any other film-forming resin previously described. The coating composition used to form the primer coating composition may also contain the crosslinking agents, colorants, and other optional materials previously described.

[0111] Additionally, the primer coating composition may contain corrosion inhibitors. As used herein, "corrosion inhibitor" refers to a component, such as a material, substance, compound, or complex, that reduces the rate or severity of surface corrosion on a metallic or metal alloy substrate. Corrosion inhibitors may contain, but are not limited to, alkali metal components, alkaline earth metal components, transition metal components, or combinations thereof. The term "alkali metal" refers to elements in Group 1 of the periodic table (International Union of Pure and Applied Chemistry, IUPAC), and includes, for example, cesium (Cs), strontium (Fr), lithium (Li), potassium (K), rubidium (Rb), and sodium (Na). The term "alkaline earth metal" refers to elements in Group 2 of the periodic table (IUPAC), and includes, for example, barium (Ba), beryllium (Be), calcium (Ca), magnesium (Mg), and strontium (Sr). The term "transition metals" refers to elements in groups 3 through 12 of the periodic table (IUPAC), and includes, for example, titanium (Ti), chromium (Cr), and zinc (Zn), as well as various other elements.

[0112] Specific, non-limiting examples of inorganic components that serve as corrosion inhibitors include magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium phosphate, magnesium silicate, zinc oxide, zinc hydroxide, zinc carbonate, zinc phosphate, zinc silicate, zinc powder, and combinations thereof.

[0113] As indicated, the primer coating composition may be deposited directly onto at least a portion of the substrate prior to the application of the first or second primer coating composition, and then dehydrated and / or cured to form a primer coating. The primer coating compositions of the present invention may be applied in any standard manner in the art, such as electroplating, spraying, electrostatic spraying, dipping, roller coating, brushing, etc. Once the primer coating composition is applied to at least a portion of the substrate, the composition may be dehydrated and / or cured to form a primer coating. The primer coating composition may, for example, be dehydrated and / or cured at a temperature of 175°C to 205°C to form a primer coating.

[0114] It has been discovered that the multilayer coatings of this invention can be formed at lower dehydration / curing temperatures than other coatings typically applied to automotive substrates such as vehicles. Thus, the multilayer coatings of this invention help reduce costs, decrease the number of coating equipment required, and accelerate the overall coating process.

[0115] The present invention also relates to a method for preparing a multilayer coating. The method comprises: forming a first base coat on at least a portion of a substrate by depositing a first coating composition onto at least a portion of the substrate; and forming a second base coat on at least a portion of the first base coat by depositing a second coating composition directly onto at least a portion of: (1) the first base coat after dehydration of the first coating composition; or (2) the first coating composition before dehydration of the first base coat composition. The first and second base coat compositions may be dehydrated individually or simultaneously, and then cured as previously described. Optionally, a top coat is formed on at least a portion of the second base coat by depositing a top coat composition directly onto at least a portion of the second base coat. When a top coat is used, the base coat and the top coat may cure simultaneously.

[0116] The substrate may optionally include a primer coating, and the first primer coating is applied over at least a portion of the primer coating by directly depositing a first primer coating composition onto at least a portion of the primer coating. The primer coating can be formed by depositing the primer coating composition onto at least a portion of the substrate prior to depositing the first primer coating composition, such as by electrodepositing an electrodeposable coating composition onto at least a portion of the substrate.

[0117] Multicoatings can be applied to any type of substrate as described above, such as automotive parts in an automotive assembly plant. In some instances, during the application of multicoatings in an automotive assembly plant, optionally, a metal substrate is first conveyed to an electrodeposition station where a primer coating composition is electrodeposited onto the metal substrate and dehydrated and / or cured. A first primer coating composition is then applied directly onto the electrodeposited coating, or alternatively, the first primer coating composition is applied directly onto at least a portion of the substrate in a primer coating zone comprising one or more coating stations. The primer coating zone may be located downstream of and adjacent to the electrodeposition oven. The first primer coating station has one or more conventional applicators, such as bell or gun applicators, connected to or in flow communication with a source of the first primer coating composition. The first primer coating composition can be applied in one or more sprays, such as spraying onto the substrate, by one or more applicators at the first primer coating station, to form a first primer coating on the substrate.

[0118] The first primer coating can be dehydrated using a conventional drying apparatus, such as an oven, located downstream and / or adjacent to the second and / or first coating stations. After the application of the second primer composition, if the first primer has already been pre-dehydrated, the second primer composition can be dehydrated separately. Alternatively, when the second primer composition is applied wet-to-wet to the first primer composition, both primer compositions can be dehydrated simultaneously. The primers can then be cured using an oven.

[0119] After the first and second primer compositions have been dehydrated and / or cured, one or more conventional topcoat compositions may be applied over the primers at a topcoat station. The topcoat station contains one or more conventional applicators, such as bell applicators, which are connected to and in flow communication with a source of the topcoat composition. An oven is located downstream of and / or adjacent to the topcoat station to allow the topcoat composition to be dehydrated and / or cured, alone or simultaneously with the primers.

[0120] A non-limiting example of an automotive assembly plant for applying a multilayer coating is described in column 3, line 1 through column 4, line 43 of U.S. Patent No. 8,846,156 and Figure 1, which is incorporated herein by reference.

[0121] Example

[0122] The following examples are presented to illustrate the general principles of the invention. The invention should not be considered limited to the specific examples presented. Unless otherwise indicated, all parts and percentages in the examples are by weight.

[0123] Furthermore, in the following examples, Brookfield viscosity was measured at 60 RPM at 25°C using a Brookfield DV-II+Pro viscometer manufactured by Brookfield Engineering, Inc. (Middleboro, MA), with rotor #2. Acid and hydroxyl values ​​were determined using a Metrohm 798MPT Titrino automatic titrator manufactured by Metrohm AG, Inc. (Herisau, Switzerland) according to ASTM D 4662-15 and ASTM E1899-16, respectively. Non-volatile (solids) content was measured by comparing the initial sample weight with the sample weight after exposure at 110°C for 1 hour.

[0124] The weight-average and number-average molecular weights of the polymer samples were determined by gel permeation chromatography (GPC) associated with linear polystyrene standards ranging from 800 to 900,000 Da. GPC was performed using a Waters 2695 separation module equipped with a Waters 2414 differential refractometer (RI detector) manufactured by Waters Corporation (Milford, MA). Tetrahydrofuran (THF) was used as the eluent at a flow rate of 1 mL / min. Separation was performed using two PLgel Mixed-C (300 × 7.5 mm) columns manufactured by Agilent Technologies Corporation (Santa Clara, CA). The pH measurements presented herein were taken using a Fisherbrand-accumet AE150 Benchtop pH meter, manufactured by Thermo Fisher Scientific Corporation (Waltham, MA) at room temperature (i.e., 23–25 °C). The dry film thickness was measured at room temperature (i.e., 23-25°C) using an Elcometer PG70ABDL precision thickness gauge manufactured by Elcometer USA (Manchester, United Kingdom).

[0125] Comparison Example 1:

[0126] Comparison of the preparation of polyester A

[0127] Polyester A is prepared as polyester A1 as described in EP 1454971. The acid value of polyester A is 29-31.

[0128] Example 2:

[0129] Preparation of Polyester B

[0130] Polyester B according to the present invention is prepared from the components listed in Table 1.

[0131] Table 1

[0132]

[0133] 1 Polytetramethylene ether diol is commercially available from Invista (Wichita, KS). 2 Dipropylene glycol methyl ether is commercially available from Dow Chemical Company (Midland, MI).

[0134] Add the contents of charge 1 to a four-necked 5-liter reaction flask equipped with a stirrer, gas inlet, thermometer, small packed column, and condenser. Heat the reaction mixture to a maximum temperature of 175°C and measure the acid value hourly after removing water. When the acid value reaches at least 80, reduce the temperature to 165°C. Continue the reaction until the cut viscosity (60% in xylene) is within the Gardner Holdt viscosity range of VY, where the acid value is 51 to 55 based on total resin solids. Reduce the temperature to 130°C and add charge 2 to the reaction mixture. Then reduce the temperature to 100°C and produce an aqueous dispersion by alternately adding charges 3 and 4 to the reaction mixture. The final dispersion has a solids value of 37% at room temperature (i.e., 23–25°C), a Brookfield viscosity of 3000 cps, and a pH of 6.6.

[0135] Comparison Example 3:

[0136] Comparison of the preparation of polyester C

[0137] Polyester C is prepared from the components listed in Table 2.

[0138] Table 2

[0139]

[0140]

[0141] The contents of charge 1 were added to a four-necked 5-liter reaction flask equipped with a stirrer, gas inlet, thermometer, small packed column, and condenser. The contents were heated to 175°C, and the acid value was measured hourly after water removal. When the acid value reached 80, the temperature was lowered to 165°C, and the reaction was continued until the acid value was measured to be 76. The temperature was then lowered to 130°C, and charge 2 was added to the flask. After cooling to 100°C, an aqueous dispersion was prepared by alternately adding charges 3 and 4 to the flask. The final dispersion had a solids value of 36% at room temperature (i.e., 23–25°C), a Brookfield viscosity of 400 cps, and a pH of 6.5.

[0142] Comparison Example 4:

[0143] Comparison of the preparation of polyester D

[0144] Polyester D is prepared from the components listed in Table 3.

[0145] Table 3

[0146]

[0147] 3Polytetramethylene ether diol is commercially available from Invista (Wichita, KS).

[0148] The contents of charge 1 were added to a four-necked 5-liter reaction flask equipped with a stirrer, gas inlet, thermometer, small packed column, and condenser. The contents were heated to 175°C, and the acid value was measured hourly after water removal. When the acid value reached 75, the temperature was lowered to 165°C, and the reaction was continued until the acid value was measured to be 65. The temperature was then lowered to 130°C, and charge 2 was added to the flask. After cooling to 100°C, an aqueous dispersion was prepared by alternately adding charges 3 and 4 to the flask. The final dispersion had a solids value of 36% at room temperature (i.e., 23–25°C), a Brookfield viscosity of 800 cps, and a pH of 6.6.

[0149] Example 5-12

[0150] Coating preparation

[0151] Prepare the coating compositions using the following method, according to the quantities shown in Table 4. Mix each coating composition in a plastic cup using a stirrer until fully blended. Once each coating composition is fully blended, allow each composition to stand under ambient conditions for 2–3 hours before applying it to the test panels. Apply each composition to the test panels using a doctor blade. Each test panel is a 4" x 12" steel substrate pre-coated with ED7400 electrophoretic coating primer (commercially available from PPG Industries, Pittsburgh, PA), and the steel substrate was processed and baked according to the manufacturer's recommendations. Place the test panels containing the wet-applied coating compositions under ambient conditions for up to 5 minutes, and then bake them in an oven at 80°C for 30 minutes. The cured coating composition has a dry film thickness of 15–18 micrometers. Allow each coated test panel to stand under ambient conditions for 20 to 60 minutes before performing solvent resistance testing.

[0152] Table 4

[0153]

[0154] 4 Methylated melamine-formaldehyde resin is commercially available from Prefere Resins Holding GmbH (Erkner, Germany).

[0155] Coating evaluation

[0156] Solvent resistance tests were performed on each cured coating composition using the following procedure. The test panel was placed on a flat, firm surface. A piece of Fisher brand 4"x4" 12-ply gauze was placed on the ball end of a (1) pound round-headed hammer. It was secured to the gauze on the test panel using a rubber band to prevent wrinkling. The gauze was soaked in methyl ethyl ketone (MEK). Immediately afterward, the soaked gauze was rubbed with the hammer over the test area by 4-6 inch back-and-forth strokes. No downward or upward pressure should be applied to the hammer handle, as the weight of the hammer itself controls the downward pressure. Every 25 double rubs, the gauze was re-soaked in MEK. Double rubs were continued, where each "double rub" involved both forward and backward movement until the exposed substrate was exposed at the center of the rubbed band. The test results shown in Table 5 indicate the number of double rubs required to expose the exposed substrate at the center of the rubbed band. The gauze area should be rotated for the next test setup. The gauze used for testing should always be rotated to the new spot each time a new area is tested. A single 4x4 gauze sheet typically contains 5-10 test areas.

[0157] Table 5

[0158] Example Solvent resistance (MEK dual friction) Comparison Example 5 11 6 45 Comparison Example 7 15 Comparison Example 8 13 Comparison Example 9 25 10 45 Comparison Example 11 18 Comparison Example 12 17

[0159] The results in Table 5 show that polyester B (acid value 51-55) exhibits significantly better solvent resistance compared to polyester A (acid value 29-31). Polyester C and polyester D also show poorer solvent resistance compared to polyester B. Based on the total resin solids content, the acid values ​​of polyester C and polyester D are 76 and 65, respectively.

[0160] Although specific embodiments of the invention have been described above for illustrative purposes, it will be apparent to those skilled in the art that many detailed changes may be made to the invention without departing from the invention as defined in the appended claims.

Claims

1. A coating composition comprising: (a) A melamine resin comprising an imino functional group and a hydroxymethyl functional group, wherein the imino functional group and the hydroxymethyl functional group together account for 30 mol% or more of the total functionality of the melamine resin; as well as (b) at least one polymer, said at least one polymer being reactive with (a), and obtained from a component comprising polytetrahydrofuran and a carboxylic acid or its anhydride. The polytetrahydrofuran constitutes more than 20% by weight of the component forming the polymer (b), and the carboxylic acid or its anhydride constitutes more than 13% by weight of the component forming the polymer (b). Wherein, if the polymer (b) does not include core-shell particles, then based on the total resin solids of the polymer (b), the acid value of the polymer is in the range of 40 to 60; or The polymer (b) reactive with the melamine resin (a) comprises polymer core-shell particles, wherein at least a portion of the polymer shell of the core-shell particles is covalently bonded to at least a portion of the polymer core of the core-shell particles, and The polymer shell of the core-shell particles is obtained from a composition comprising more than 20% by weight of polytetrahydrofuran and more than 13% by weight of carboxylic acid or its anhydride, and wherein the acid value of the polymer shell is in the range of 40 to 60 based on the total resin solids of the polymer forming the polymer shell.

2. The coating composition according to claim 1, wherein the carboxylic acid or its anhydride comprises at least one aromatic ring, and wherein the carboxylic acid functional group or the anhydride functional group is directly bonded to the aromatic ring.

3. The coating composition according to claim 1 or 2, wherein the carboxylic acid or its anhydride comprises trimellitic anhydride.

4. The coating composition according to claim 1 or 2, wherein the polymer shell of the core-shell particles comprises ether bonds and ester bonds, urethane bonds, or combinations thereof.

5. The coating composition according to claim 1 or 2, wherein the polymer shell of the core-shell particles comprises carboxylic acid functional groups and hydroxyl functional groups.

6. The coating composition according to claim 1 or 2, wherein the polymer core of the core-shell particles comprises an addition polymer derived from an olefinic unsaturated monomer.

7. The coating composition according to claim 1 or 2, wherein the polymer (b) that is reactive with the melamine resin (a) comprises a self-emulsifying dispersion polymer.

8. The coating composition according to claim 7, wherein the polytetrahydrofuran accounts for more than 40% by weight of the component forming the self-emulsifying dispersion polymer.

9. The coating composition according to claim 7, wherein the self-emulsifying dispersion polymer comprises ether bonds and ester bonds, urethane bonds, or combinations thereof.

10. The coating composition according to claim 1 or 2, wherein the polymer (b) reactive with the melamine resin (a) comprises both of the following: (i) the polymer core-shell particles; and (ii) the self-emulsifying dispersion polymer.

11. The coating composition according to claim 1 or 2, wherein the melamine resin (a) accounts for 5% to 40% by weight of the coating composition based on the total resin solids of the coating composition.

12. The coating composition according to claim 1 or 2, wherein the polymer (b) that is reactive with the melamine resin (a) accounts for 50% to 90% by weight of the total resin solids of the coating composition.

13. A substrate having at least partially coated with a coating formed from the coating composition according to any one of claims 1 to 12.

14. The substrate of claim 13, wherein the substrate forms at least a portion of a vehicle.

15. The substrate of claim 13, wherein the substrate forms at least a portion of the packaging.

16. The substrate of claim 15, wherein the packaging comprises a metal can, an aerosol can or tube, or a single-piece aerosol can or tube.

17. A multilayer coating system comprising: A first base coating is applied to at least a portion of the substrate; as well as A second base coat is applied over at least a portion of the first base coat. At least one of the first base coating and the second base coating is formed from the coating composition according to any one of claims 1 to 12.

18. The multilayer coating system of claim 17, further comprising a primer coating applied over at least a portion of the substrate, wherein the first primer coating is positioned between the first primer coating and the substrate.

19. The multilayer coating system according to claim 17 or 18, further comprising a top coating layer applied over at least a portion of the second base coating layer.

20. A method for coating a substrate with a multilayer coating, the method comprising: A first base coating is formed on at least a portion of a substrate by depositing a first base coating composition onto the substrate. as well as A second base coat is formed on at least a portion of the first base coat by directly depositing the second base coat composition onto (1) the first base coat composition after dehydration or (2) at least a portion of the first base coat composition before dehydration. The first and second primer compositions are dehydrated for two minutes or less at a temperature ranging from 20°C to 90°C, and At least one of the first base coating and the second base coating is formed from the coating composition according to any one of claims 1 to 12.

21. The method of claim 20, wherein the first base coat composition is dehydrated before the second base coat composition is applied.

22. The method according to claim 20 or 21, wherein both the first base coat composition and the second base coat composition are simultaneously dehydrated.

23. The method of claim 22, wherein after dehydration, the first and second base coats together comprise at least 80% by weight of solids content based on the total weight of the first and second base coats.

24. The method of claim 20 or 21, further comprising curing the first base coat and the second base coat at a temperature of 120°C or lower.

25. The method of claim 20 or 21, further comprising applying a topcoat composition over at least a portion of the second basecoat composition and simultaneously curing the first coating composition, the second coating composition, and the topcoat composition at a temperature of 120°C or lower.

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