Peelable coating composition and method for preparing a peelable coating
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- DOW GLOBAL TECHNOLOGIES LLC
- Filing Date
- 2023-04-06
- Publication Date
- 2026-05-27
Abstract
Description
[Technical Field]
[0001] The present invention relates to a peelable coating composition and a method for preparing a peelable coating from a coating composition. [Background technology]
[0002] Introduction Peelable coatings (also known as removable protective coatings) protect surfaces for a period of time from hazardous environmental conditions, such as contact with sharp objects, objects with transferable colorants, and degradation from acid rain and ultraviolet (UV) radiation. While the time interval for which the coating must provide protection can be several months or even years, it is even more desirable that such temporary coatings be removable when the level of protection they provide is no longer needed. For example, the need for removable protective coatings exists during the manufacture, storage, and distribution of vehicles, ships, electrical appliances, computers, furniture, sports equipment, and the components on which they are manufactured, as well as building materials. It is highly desirable that the entire coating can be removed quickly and smoothly, without labor-intensive processes, the use of any additional materials (e.g., solvents, acids, bases, and aqueous detergents), or the generation of waste flows, maintaining the "just off the assembly line" appearance of the coated vessel, leaving no residue, and causing damage to the underlying layers. The peelability of a coating is closely related to the type of substrate to which the coating is applied. While coating compositions can provide desirable release properties on glass substrates, they are typically unsuitable for other substrates, such as metals (optionally coated with polymers). Therefore, providing good release properties to various substrates in different coating applications, including glass, metals, and pre-coated surfaces (e.g., steel substrates coated with polyurethane coatings), is particularly challenging for a single release coating composition. Furthermore, since release coatings are widely used in outdoor applications, water resistance and release properties after UV exposure or rainfall are especially important.
[0003] International Publication No. 2008 / 063411(A2) discloses a peelable protective coating composition for protecting the exterior surfaces of automobiles and other products. The aqueous coating composition comprises an aqueous mixture or solution containing a polyvinyl butyral film-forming agent and an extender, but the mixture or solution does not contain polyurethane, and the peelability properties of a peelable coating made from the aqueous coating composition after UV exposure have not been evaluated.
[0004] Furthermore, some manufacturers and end-users require the release coating to be transparent. In furnishing applications, transparent release coatings allow end-users to easily select furnishings with their desired color and appearance (e.g., wood grain). For temporary protection of electronic devices (e.g., laptops), transparent release coatings are also desirable so that surface defects on the electronic device can still be visually inspected when covered with the release coating.
[0005] Therefore, it is desirable to provide a coating composition that protects the surface of various substrates from, for example, UV exposure or the harmful effects of rain, while simultaneously providing a coating film made from the coating composition that is transparent, easily removed as a single sheet, and leaves no residue. [Overview of the Initiative]
[0006] The present invention relates to an aqueous coating composition that can be applied to the surface of a substrate to form a transparent, releaseable film (used interchangeably with a "releaseable coating") that is easily removable, preferably as a continuous sheet, and protects the surface from various harmful environmental conditions, such as UV exposure. The aqueous coating composition of the present invention provides a coating (i.e., a releaseable coating) made from the aqueous coating composition that exhibits good release properties from several types of substrates, for example, showing a rating of 4 or higher when the coating is peeled off the surface of glass, metal (such as tin), and polyurethane (PU) coated metal, even after UV exposure. On the other hand, the coating is transparent and has high tensile strength (at least 8 megapascals (MPa)) and good water resistance (rated 4 or higher). These properties can be measured according to the test methods described in the following Examples section.
[0007] In a first aspect, the present invention relates to an aqueous coating composition, (A) an aqueous polyurethane dispersion containing the reaction products of components (i) and (ii), (i) an isocyanate component comprising an aliphatic or alicyclic polyisocyanate containing at least two isocyanate groups, (ii)(ii-a) a polyol containing a lactone-based polyester polyol, (ii-b) an anionic emulsifier containing at least one isocyanate-reactive group and an anionic group or a latent anionic group, and (ii-c) an isocyanate-reactive component containing a monofunctional polyalkylene ether containing one hydroxyl group or an amino group, in an amount of less than 0 to 1.0% by weight based on the total weight of the isocyanate component and the isocyanate-reactive component; an aqueous polyurethane dispersion comprising: (B) Based on the total solids weight of the aqueous coating composition, an amphoteric surfactant having an isoelectric point at pH 3 to pH 8 is present in an amount of 0.1% to 10.0% by solids weight, (C) An aqueous coating composition comprising a light absorber, a light stabilizer, or a mixture thereof.
[0008] In a second aspect, the present invention relates to a method for preparing a peelable coating. This method is (I) To provide an aqueous coating composition according to the first embodiment, (II) Applying an aqueous coating composition to the surface of a substrate, (III) Drying the applied aqueous coating composition, or drying it to form a peelable coating. [Modes for carrying out the invention]
[0009] The test method refers to the test method most recent to the priority date of this document unless the date is indicated along with the test method number. References to test methods include both references to the testing association and the test method number. In this specification, the following abbreviations and identifiers for test methods apply: ASTM refers to ASTM International Law, ISO refers to the International Organization for Standardization, and JG / T refers to the Chinese Building and Construction Industry Standard (Recommended). Products identified by trade names refer to compositions available under those trade names as of the priority date of this document.
[0010] "And / or" means "and, or as an alternative." All ranges include the endpoint unless otherwise specified.
[0011] In this specification, “aqueous” dispersion means that particles are dispersed in an aqueous medium. In this specification, “aqueous medium” means water and, based on the weight of the medium, 0 to 30% by weight of a water-miscible compound(s), such as alcohols, glycols, glycol ethers, glycol esters, or mixtures thereof.
[0012] The aqueous coating composition of the present invention (also called the "peelable coating composition") comprises (A) an aqueous anionic polyurethane dispersion, preferably an aqueous anionic aliphatic polyurethane dispersion. The aqueous polyurethane dispersion comprises the reaction product (e.g., addition polymerization reaction) of (i) an isocyanate component and (ii) an isocyanate-reactive component as described below. The aqueous polyurethane dispersion may or may not contain an external emulsifier of component (iii).
[0013] An isocyanate is a compound containing one or more pendant isocyanate groups (for example, an isocyanate containing two or more isocyanate groups per molecule is a polyisocyanate, and an isocyanate containing exactly two isocyanate groups is a diisocyanate). Unless otherwise specified, the term isocyanate as used herein includes monomeric isocyanates and prepolymeric isocyanates.
[0014] In the present invention, useful isocyanate component (i) includes one or more aliphatic polyisocyanates containing at least two isocyanate (NCO) groups, one or more alicyclic polyisocyanates containing at least two NCO groups, or a mixture thereof. "Aliphatic polyisocyanate" refers to a polyisocyanate that does not contain an aromatic ring and typically contains a linear or branched alkylene residue having 3 to 16 carbon atoms or 4 to 12 carbon atoms. That is, in this specification, "aliphatic polyisocyanate" excludes "alicyclic polyisocyanate" as described later. "Alicyclic polyisocyanate" refers to a polyisocyanate that typically contains a cycloalkylene residue having 4 to 18 carbon atoms or 6 to 15 carbon atoms. Preferably, isocyanate component (i) is an alicyclic polyisocyanate. Isocyanate component (i) may have an average NCO functional value of at least 2, which may be 2 to 10, 2 to 8, or 2 to 6. Alicyclic diisocyanates include isophorone diisocyanate and diisocyanatodicyclohexylmethane (H 12This refers to NCO groups that are attached in both cyclic and aliphatic forms, such as MDI. Examples of aliphatic and alicyclic polyisocyanates include hexamethylene diisocyanate (HDI), cyclohexane diisocyanate, methylcyclohexane diisocyanate, ethylcyclohexane diisocyanate, propylcyclohexane diisocyanate, methyldiethylcyclohexane diisocyanate, propane diisocyanate, butane diisocyanate, pentane diisocyanate, hexane diisocyanate, heptane diisocyanate, octanediocyanate, nonane diisocyanate, nonane triisocyanate, for example, 4-isocyanatomethyl-1,8-octanediocyanate (TIN), decanedio and triisocyanates, undecanedi and triisocyanates, as well as dodecanedi and triisocyanates, isophorone diisocyanate (IPDI), diisocyanatodicyclohexylmethane (H 12MDI), 2-methylpentane diisocyanate (MPDI), 2,2,4-trimethylhexamethylene diisocyanate / 2,4,4-trimethylhexamethylene diisocyanate (TMDI), norbornane diisocyanate (NBDI); dimers of these monomeric polyisocyanates; trimers of these monomeric polyisocyanates; and mixtures thereof. Desirably, the isocyanate component comprises or consists of one or more alicyclic diisocyanates, more desirably IPDI. If the average functionality of the isocyanate component (i) is 2 or more, a mixture of two or more aliphatic polyisocyanates, a mixture of two or more alicyclic polyisocyanates, or a mixture of an aliphatic polyisocyanate and an alicyclic polyisocyanate can be used. The isocyanate component (i) can include a monomeric aliphatic or alicyclic polyisocyanate, and a prepolymer of a monomeric aliphatic or alicyclic polyisocyanate containing at least two isocyanate groups (used interchangeably with "isocyanate prepolymer" and "prepolymer isocyanate"), or a mixture thereof. The isocyanate prepolymer can be obtained by reacting the above polyisocyanate with an isocyanate-reactive component described below (ii) in the presence of an internal emulsifier described below, provided that the isocyanate prepolymer still contains at least two isocyanate groups. Then, the isocyanate prepolymer can further react with the isocyanate-reactive component to produce a polyurethane dispersion (PUD).
[0015] The isocyanate-reactive component is (ii-a) a polyol containing a lactone-based polyester polyol, and (ii-b) an anionic emulsifier, and optionally, one or more of components (ii-c) monofunctional polyalkylene ether, (ii-d) chain extender, and (ii-e) polyhydric alcohol, all of which are described below. Desirably, the isocyanate-reactive component (ii) can comprise or consist of components (ii-a), (ii-b), and (ii-d) described below.
[0016] In the present invention, the useful isocyanate-reactive component (ii) includes a polyol comprising component (ii-a) one or more lactone-based polyester polyols having at least two hydroxyl (OH) groups. In this specification, "polyol" means a compound having two or more hydroxyl groups in one molecule and having a number-average molecular weight of 500 grams / mol (g / mol) or more. The lactone-based polyester polyols useful in the present invention may have a number average molecular weight of 500 g / mol to 5,000 g / mol, and may be 500 g / mol or more, 600 g / mol or more, 800 g / mol or more, 1,100 g / mol or more, 1,500 g / mol or more, and even 2,000 g / mol or more, while also being 5,000 g / mol or less, 4,500 g / mol or less, 4,000 g / mol or less, 3,500 g / mol or less, or even 3,000 g / mol or less, preferably 2,000 g / mol to 3,000 g / mol. The molecular weight of the polyol can be measured by gel permeation chromatography (GPC) or calculated by the formula 56100 (mg / mol) * f / OHV (mg KOH / g), where OHV represents the hydroxyl value of the polyol and f represents the functional value of the polyol. Lactone-based polyester polyols may have a hydroxyl value of 20–225 mg KOH / g, and can be 20 mg KOH / g or more, 30 mg KOH / g or more, and even 40 mg KOH / g or more, while generally being 225 mg KOH / g or less, 200 mg KOH / g or less, 175 mg KOH / g or less, or even 150 mg KOH / g or less. The hydroxyl value (OHV) is defined as the number of milligrams of potassium hydroxide (KOH) chemically equivalent to the activity of 1 gram of polyol, and can be measured according to ASTM D 4274. Lactone-based polyester polyols may be homopolymers or copolymers of lactones, preferably terminal hydroxyl functionalization products of lactones and suitable difunctional initiator molecules. Suitable bifunctional initiator molecules may include compounds represented by the general formula HO-(CH2)z-OH (wherein z is an integer from 2 to 20, and one hydrogen atom in the methylene unit may be replaced by a C1-C4 alkyl group); or mixtures thereof.Examples of lactones include ε-caprolactone, methyl-ε-caprolactone, β-propiolactone, γ-butyrolactone, or mixtures thereof. Preferably, the lactone-based polyester polyol is a polycaprolactone polyol. Polycaprolactone polyols can be obtained by ring-opening polymerization of ε-caprolactone monomers under the catalytic action of a metal anion complex catalyst by controlling the polymerization conditions. Based on the total weight of the polyol in the isocyanate-reactive component (ii), the lactone-based polyester polyol can be present in concentrations of 80% to 100%, and can be 80% or more, 82% or more, 85% or more, 88% or more, 90% or more, 92% or more, 94% or more, and even 95% or more, while generally being 100% or less, and can be 99% or less, 98% or less, 96% or less, 95% or less, and preferably 95% to 100%. Alternatively, the lactone-based polyester polyol can be present in an amount of 80% to 99% based on the total weight of the isocyanate-reactive component (ii), and may be 80% or more, 82% or more, 85% or more, or even 87% or more, while generally being 99% or less, 98% or less, 96% or less, or even 95% or less, preferably 85% to 95% by weight.
[0017] The isocyanate-reactive component (ii) useful in the present invention comprises (ii-b) an anionic emulsifier (hereinafter also referred to as the "internal emulsifier") comprising at least one isocyanate-reactive group and at least one anionic group or latent anionic group. The internal emulsifier can act as a copolymerizable comonomer. A latent anionic group refers to a group that can be converted to an anionic group, which is typically done by adding a tertiary amine such as triethylamine. The expression "anionic group or latent anionic group" will hereafter be abbreviated as "(latent) anionic group". The internal emulsifier can be appropriately selected such that the molar content of (potential) anionic groups is 30 to 1,000 mmol / kg per kilogram of isocyanate component (i) and isocyanate reactive component (ii), based on the total weight (i.e., combined weight) of isocyanate component (i) and isocyanate reactive component (ii) (i.e., the total weight of the reactants for preparing the polyurethane dispersion), and may be 30 mmol / kg or more, 50 mmol / kg or more, 80 mmol / kg or more, and even 100 mmol / kg or more, while simultaneously being 1,000 mmol / kg or less, 800 mmol / kg or less, 500 mmol / kg or less, 400 mmol / kg or less, 350 mmol / kg or less, or even 300 mmol / kg or less, preferably 100 to 400 mmol / kg. (Potential) anionic groups may include anionic groups such as sulfonates, carboxylates, and phosphates in the form of alkali metal salts or ammonium salts. Potential anionic groups may include those that can be converted to the above-mentioned anionic groups, such as carboxylic acid groups or anhydride groups, by simple neutralization or hydrolysis reactions. Anionic internal emulsifiers may include aliphatic, alicyclic, aromatic aliphatic, or aromatic carboxylic acids, carbonates, and sulfonic acids that independently have at least one alcoholic hydroxyl group or at least one primary or secondary amino group.Preferably, the internal emulsifier can be a dihydroxyalkyl carboxylic acid having 3 to 10 carbon atoms, such as dihydroxymethylpropionic acid (DMPA) and dimethylolbutanoic acid (DMBA), dihydroxy sulfonic acid, dihydroxy phosphonic acid, such as 2,3-dihydroxypropane phosphonic acid, or a mixture thereof. More preferably, the internal emulsifier is DMPA. When internal emulsifiers having potentially anionic groups are used, they can be converted into anionic forms before, during, and preferably after the isocyanate addition polymerization. Preferably, a sulfonate group or a carboxylate group is present in the internal emulsifier.
[0018] The isocyanate-reactive component (ii) useful in the present invention may or may not substantially contain a monofunctional polyalkylene ether containing one hydroxy or amino group. The monofunctional polyalkylene ether contains a polyalkylene oxide chain that may include ethylene oxide units, propylene oxide units, butylene oxide units, or a combination thereof. Suitable monofunctional polyalkylene ethers include, for example, poly(ethylene glycol) monomethyl ether, poly(propylene glycol) monomethyl ether, or a mixture thereof. "Substantially not containing" means that the monofunctional polyalkylene ether is present in an amount of less than 0 to 1 wt%, less than 0.6 wt%, less than 0.5 wt%, less than 0.1 wt%, or even 0, based on the total weight of the isocyanate component (i) and the isocyanate-reactive component (ii).
[0019] The isocyanate-reactive component (ii) useful in the present invention may comprise one or more chain extenders selected from (ii-d) isocyanate-reactive diamines, amine compounds having another isocyanate-reactive group, or mixtures thereof. The chain extenders typically have molecular weights of 32 g / mol to less than 500 g / mol, 50 g / mol to 400 g / mol, or 50 g / mol to 200 g / mol. The chain extenders may be selected from amination polyetherdiols; ethanolamine; piperazine; 2,5-dimethylpiperazine; diamines, e.g., ethylenediamine, diaminoethane, diaminopropane, e.g., 1,2-propanediamine, diaminobutane, diaminohexane, piperazine, amino-3-aminomethyl-3,5,5-trimethylcyclohexane (isophoronediamine, IPDA), 4,4'-diaminodicyclohexylmethane, 1,4-diaminocyclohexane, aminoethylethanolamine, and mixtures thereof; or combinations thereof. Preferably, the chain extender is 1,2-propanediamine. The concentration of the chain extender may be in the range of 0 to 10% by weight, based on the total weight of the isocyanate component (i) and the isocyanate reactive component (ii), and may be 0% or more, 0.1% or more, 0.5% or more, 1.0% or more, 2.0% or more, 3.0% or more, and even 3.5% or more by weight, while generally being 10% or less by weight, and may be 8.0% or less, 6.0% or less, 5.0% or less by weight, or even 4.0% or less by weight, preferably 3.0% to 5.0% by weight.
[0020] In the present invention, the useful isocyanate-reactive component (ii) may include (ii-e) one or more polyhydric alcohols having a molecular weight typically less than 500 g / mol. The polyhydric alcohols may be C2-C2. 16 Aliphatic polyhydric alcohols, C6-C 15Examples include alicyclic polyhydric alcohols or mixtures thereof. Suitable examples of polyhydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butenediol, 1,4-butynediol, 1,5-pentanediol, neopentyl glycol, bis(hydroxymethyl)cyclohexane, e.g., 1,4-bis(hydroxymethyl)cyclohexane, 2-methylpropane-1,3-diol, methylpentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, polybutylene glycol, and mixtures thereof. Preferably, the polyhydric alcohol has a structure represented by the general formula HO-(CH2)x-OH, where x is an integer from 1 to 20 or an even number from 2 to 20. (ii-d) The concentration of the polyhydric alcohol may be 0 to 5% by weight, based on the total weight of the isocyanate component (i) and the isocyanate-reactive component (ii), and may be less than 5% by weight, less than 4% by weight, less than 1% by weight, less than 0.5% by weight, or even 0% by weight.
[0021] The above components for preparing the polyurethane dispersion are present in amounts that provide a molar ratio of total isocyanate groups to total isocyanate-reactive groups within the ranges of 0.5:1 to 2:1, 0.8:1 to 1.5:1, and 0.9:1 to 1.2:1, or such a molar ratio may be 1:1.
[0022] The aqueous polyurethane dispersion useful in the present invention may or may not contain an external emulsifier (also referred to as "external surfactant") other than the above internal emulsifier or the following amphoteric surfactant. The "external emulsifier" is an ionic or non-ionic emulsifier that is not covalently bonded to the main chain within the polyurethane particles dispersed in the aqueous medium in the polyurethane dispersion through a urethane bond derived from the reaction between an isocyanate group and an isocyanate-reactive group (such as a hydroxyl group) in order to stabilize the polyurethane dispersion. The external emulsifier typically does not contain a copolymerizable group or an isocyanate-reactive group. The external emulsifier can be cationic, anionic, or non-ionic, and is preferably anionic. Suitable examples of the external emulsifier include sulfates of ethoxylated phenols such as poly(oxy-1,2-ethanediyl) α-sulfo-ω-(nonylphenoxy) salt; alkali metal fatty acid salts such as alkali metal oleate and stearate; alkali metal C 12 ~C 16 alkyl sulfate; amine C 12 ~C 16 alkyl sulfate, more preferably triethanolamine lauryl sulfate; alkali metal C 12 ~C 16 alkylbenzene sulfonate; amine C 12 ~C 16 alkylbenzene sulfonate; fluorinated C4~C 16 alkyl ester and alkali metal C4~C 16Examples include anionic and nonionic fluorocarbon emulsifiers such as perfluoroalkyl sulfonates; and organosilicon emulsifiers such as modified polydimethylsiloxanes. Preferably, the external emulsifier is sodium lauryl sulfate. The amount of external emulsifier may be in the range of 0 to 10% by weight, based on the total weight of the isocyanate component (i) and the isocyanate reactive component (ii), and may be 0% or more, 0.1% or more, 0.5% or more, 1.0% or more, 2.0% or more, 3.0% or more, 4.0% or more, and even 5.0% or more by weight, while generally being 10% or less by weight, and may be 9% or less, 8.0% or less, 7.5% or less, 7% or less, or 6.5% or less by weight.
[0023] Aqueous polyurethane dispersions useful in the present invention can be prepared according to known methods, preferably by the "acetone method" or the "prepolymer mixing method." A general procedure involves first preparing a prepolymer or polyurethane in an inert organic solvent, and then dispersing the prepolymer or polyurethane in water. The prepolymer can be further polymerized into polyurethane using water or by adding the above-mentioned chain extenders such as diamines. Polyurethane dispersions prepared using an anionic internal emulsifier are also known as internally emulsified polyurethane dispersions, in which a polyurethane dispersion stabilized by incorporating anionic hydrophilic pendant groups into polyurethane particles is dispersed. A typical method for preparing such a polyurethane (PU) dispersion may include: (I) reacting a polyisocyanate or isocyanate prepolymer with (ii-a) the above polyol and (ii-b) an anionic internal emulsifier, optionally adding a tertiary amine (e.g., triethylamine) to convert the latent anionic groups (e.g., carboxylic acid groups) to anionic groups, thereby forming a PU prepolymer containing pendant anionic groups attached to the PU chain; (II) dispersing the PU prepolymer in an aqueous solvent (e.g., water) with the anionic groups attached to the PU chain as the main emulsifier, optionally with the help of an external emulsifier in this step; and optionally reacting the resulting emulsion with an additional isocyanate-reactive component (e.g., a chain extender) containing at least two isocyanate-reactive groups to form an anionic internally emulsified polyurethane dispersion.
[0024] Polyurethane particles in aqueous polyurethane dispersions, as measured by a Brookhaven BI-90 Plus particle size analyzer, may range from 30 nanometers (nm) to 150 nm, 40 nm to 120 nm, or 50 nm to 80 nm.
[0025] The aqueous polyurethane dispersion useful in the present invention also includes water. The polyurethane dispersion may have a solid content of 20% to 65% by weight, 25% to 60% by weight, or 30% to 50% by weight, based on the weight of the aqueous polyurethane dispersion.
[0026] The aqueous polyurethane dispersion may be present in the aqueous coating composition at a concentration of 60% to 98% by solids weight, based on the total solids weight of the aqueous coating composition, and may be 65% or more, 70% or more, 74% or more, 75% or more, 80% or more, 82% or more, 83% or less, 85% or more, and even 90% or more, while generally being 98% or less by solids weight, and may be 97% or less, 96% or less, 95% or less, 992% or less, or even 90% or less.
[0027] The aqueous coating composition of the present invention comprises (B) one or more amphoteric surfactants (also called "amphiphilic surfactants"). Amphoteric surfactants have both acidic and basic functional groups and are well known in the art, for example, Amphoteric Surfactants, ed. B.R. Bluestein and C.L. Hilton, Surfactant Series Vol. 12, Marcel Dekker, NY, NY (1982). Amphoteric surfactants useful in the present invention may include those having an isoelectric point between pH=3 and pH=8. The isoelectric point is the pH at which a characteristic pH occurs for each amphoteric surfactant, and is the pH at which the negative charge on the surfactant molecule is precisely in equilibrium with the positive charge on the same molecule.
[0028] Amphoteric surfactants useful in the present invention may include those having a weakly acidic functional group, particularly a carboxyl functional group. The carboxyl moiety may exist in a fully protonated (carboxylic acid) form as a salt with at least one type of cation, and as a mixture of the protonated form and the salt form. The carboxylic acid moiety may be part of an intramolecular salt. As used herein, an intramolecular salt refers to a molecule having an anionic charged moiety, the counterion (i.e., cation) of which is also a moiety bonded to the same molecule.
[0029] Suitable amphoteric surfactants useful in the present invention include, for example, aminocarboxylic acids, amphoteric imidazoline derivatives, betaines, and high molecular weight amphoteric electrolytes. Amphoteric surfactants from any of these classes may be further substituted with fluorocarbon substituents, siloxane substituents, or combinations thereof. Additional useful amphoteric surfactants can be found in Amphoteric Surfactants, ed. B.R. Bluestein and C.L. Hilton, Surfactant Series Vol. 12, Marcel Dekker, NY, NY (1982).
[0030] In the present invention, aminocarboxylic acids useful as amphoteric surfactants may have a carboxyl moiety that exists in either a protonated or carboxylate form. When two or more carboxyl groups are present on the molecule, these carboxyl groups may all be in a protonated form, a carboxylate form, or a mixture of several protonated and carboxylate forms. Furthermore, the ratio of protonated to unprotonated carboxyl moieties may differ from molecule to molecule in a given system, or may be the same otherwise. Examples of cations present as counterions to the carboxylate moiety include lithium, sodium, potassium, amines (i.e., ammonium cations derived from the protonation of amines or other quaternary substitutions), zinc, zirconium, calcium, magnesium, and aluminum cations. Any aminocarboxylic acid may have an amino moiety that exists in either a protonated (ammonium) or free amine form (i.e., as a deprotonated primary, secondary, or tertiary amine). When two or more amino groups are present on a molecule, these amino groups may all be in protonated form, free amine form, or they may exist as a mixture of several protonated and free amine forms. The ratio of protonated to unprotonated amine moieties may differ from molecule to molecule in a given system, or it may be the same otherwise. Anions that exist as counterions to the ammonium moiety include chloride, bromide, sulfate, carbonate, hydroxide, formate, acetate, propionate, and other carboxylate salt anions.
[0031] Suitable aminocarboxylic acids useful as amphoteric surfactants in the present invention include, for example, α-aminocarboxylic acids having the general structure R1-NH-CH2COOH, where R1 is C4-C 20Examples include α-aminocarboxylic acids having linear or branched, alkyl, alkenyl, or fluoro or silicone-functional hydrophobic groups; and β-aminocarboxylic acids having the general structures R1-NH-CH2CH2COOH and R1N(CH2CH2COOH)2; where R1 is as described above for α-aminocarboxylic acids. β-aminocarboxylic acids are available under the name DERIPHAT® from Henkel Corporation (King of Prussia, PA). Unless otherwise specified, DERIPHAT amphoteric electrolytes have the general formula R2-NHCH2CH2COOH, where R2 is a residue of coconut fatty acid, a residue of animal fat fatty acid, lauric acid, myristic acid, oleic acid, palmitic acid, stearic acid, linoleic acid, or other C4-C 20 These are linear or branched chains, alkyl groups, alkenyl groups, and mixtures thereof. Examples of suitable aminocarboxylic acids useful in the present invention include sodium-N-coco-β-aminopropionate; N-coco-β-aminopropionic acid; N-lauryl / myristyl-3-aminopropionic acid; disodium-N-talo-β-iminodipropionate, R2N(CH2CH2COONa)2; disodium-N-lauryl-β-iminodipropionate; partial sodium salts of N-lauryl-β-iminodipropionic acid; and R2N(CH2CH2COOH)(CH2CH2COONa). A useful polyaminocarboxylic acid is R3C(=O)NHC2H4(NHC2H4). y Examples include HCH2COOH and R3-substituted ethylenediaminetetraacetic acid (EDTA), where R3 is C4-C 20 It is a linear or branched alkyl or alkenyl molecule; y is between 0 and 3.
[0032] In the present invention, amphoteric imidazoline derivatives useful as amphoteric surfactants include those derived from various substituted 2-alkyl-2-imidazolines and 2-alkenyl-2-imidazolines, which have nitrogen atoms at positions 1 and 3 of a 5-membered ring and double bonds at positions 2 and 3. The alkyl or alkenyl group is C4-C 20It can be a linear or branched chain. Amphoteric imidazoline derivatives are produced by a reaction in which the imidazoline ring undergoes hydrolytic ring-opening under conditions that allow for further reaction with alkylating agents such as sodium chloroacetate, methyl (meth)acrylate, ethyl (meth)acrylate, and (meth)acrylic acid. Examples of suitable amphoteric surfactants derived from the reaction of 1-(2-hydroxyethyl)-2-(R4)-2-imidazoline with acrylic acid or acrylic acid esters (wherein R4 is a coconut fatty acid residue) include cocoamphocarboxypropionic acid; R4-C(=O)NHCH2CH2N(CH2CH2OH)(CH2CH2COONa); cocoamphopropionate; R4-C(=O)NHCH2CH2N( CH2CH2COOH)(CH2CH2OCH2CH2COOH);R4-C(=O)NHCH2CH2N(CH2CH2COONa)(CH2CH2OCH2CH2COONa);cocoamphoglycinate, R4-C(=O)NHCH2CH2N(CH2CH2OH)(CH2COONa);cocoamphocarboxypropionate;cocoamphocarboxyglycinate;and[R4-C(=O)NHCH2CH2N + (CH2CH2OH)(CH2COONa)2]OH is one example.
[0033] In the present invention, betaine, which is useful as an amphoteric surfactant, refers to an intramolecular surfactant salt containing at least one quaternary ammonium cation and at least one carboxyanion. The nomenclature of betaine is called betaine and is derived from a single compound (trimethylammonium) acetate that exists as an internal salt. A suitable betaine useful as an amphoteric surfactant in the present invention is, for example, one with the general formula: R5CONHCH2CH2CH2N + (CH3)2CH2COO - The compound; R5-O-CH2-N + (CH3)2CH2COO - ; and R5N + (CH3)2CH2COO - The following can be listed; in the formula, R5 is C4~C 20The linear or branched alkyl, alkenyl, or fluoro or silicone-functional hydrophobic group. Specific examples of betaines include N-dodecyl-N,N-dimethylglycine and cocamidopropyl betaine, as well as MONATERIC® CAB and MIRANOL® CM-SF, available from Solvay Chemicals.
[0034] Typically, when fluorocarbon substituents are bonded to the above-mentioned amphoteric surfactants, these substituents are branched or unbranched perfluoroalkyl groups having 6 to 18 carbon atoms. However, these substituents may instead be partially fluorinated. They may also have aryl functional groups. Examples of suitable fluorocarbon amphoteric surfactants include fluorinated alkyl FLUORAD® FC100, available from 3M, and fluorinated alkyl ZONYL® FSK, available from DuPont.
[0035] A typical siloxane-functionalized amphoteric surfactant may have the following structure:
[0036] [ka] In the formula, R represents the amphoteric moiety, n is in the range of 3 to 50, and m+n is in the range of 3 to 50. One example is the polyalkylbetaine polysiloxane copolymer ABIL® B9950, available from Goldschmidt Chemical Corporation.
[0037] Examples of useful polymeric amphoteric surfactants in the present invention include proteins, protein hydrolysates, derivatives of protein hydrolysates, starch derivatives, and synthetic amphoteric oligomers and polymers, such as those described in Chapter 5 of Amphoteric Surfactants, ed. B.R. Bluestein and C.L. Hilton, Surfactant Series Vol. 12, Marcel Dekker, NY (1982). Particularly useful are polymeric amphoteric electrolytes having carboxyl functional groups.
[0038] Amphoteric surfactants may be present in aqueous coating compositions at a concentration of 0.1% to 10.0% by solids weight, based on the total solids weight of the aqueous coating composition, and may be 0.1% or more, 0.2% or more, 0.5% or more, and even 1.0% or more, while generally being 10% or less by solids weight, and may be 9.0% or less, 8.0% or less, 7.5% or less, 7.0% or less, 6.5% or less, 5.0% or less, 4.0% or less, or even 3.0% or less, preferably 1.0% to 3.0%.
[0039] The aqueous coating compositions of the present invention also comprise (C) a light absorber, a light stabilizer, or a mixture thereof, preferably an ultraviolet (UV) absorber, a UV light stabilizer, or a mixture thereof. The light absorbers and light stabilizers may be selected from hindered amines; benzophenones; benzophenone derivatives, e.g., those described in Industrial Photoinitiators: A Technical Guide by Green, W. Arthur; CRC Press of the Taylor & Francis Group, 2010, ISBN 978-1-4398-2745-1 (Paperback); triazines, oxanilides; benzotriazoles, particularly hydroxyphenylbenzotriazole compounds, many of which are available from BASF under the trademark "TINUVIN"; or mixtures thereof. A typical example of a benzotriazole is 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, preferably TINUVIN 1130. Examples of suitable UV light stabilizers include bis-(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate (TINUVIN 123, etc.) and 2,4-bis[N-butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidine-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine (TINUVIN 152, etc.). The light absorber and / or light stabilizer (C) in the aqueous coating composition may be present in a concentration of 0.1% to 15% by solids weight, based on the total solids weight of the aqueous coating composition, and may be 0.1% or more, 0.2% or more, and even 0.5% or more, while generally being 15% or less, 12% or less, 10% or less, 5% or less, or even 3% or less, preferably 0.5% to 3% by solids weight.
[0040] The aqueous coating composition of the present invention may or may not contain (D) one or more pigments. The term "pigment" includes opacifying pigments, colorants, and special effect pigments. The term "opacifying pigment" as used herein specifically excludes organic filler particles that contain one or more voids as described below when dry (i.e., the term "opacifying pigment" as used herein excludes the opaque polymers described below). The opacifying pigments as used herein include inorganic pigment particles that scatter essentially all wavelengths of visible light without high absorption, such as titanium dioxide. The term "colorant" as used herein includes inorganic and organic colorants and includes both color-imparting pigments and dyes. The term "special effect pigment" includes metallic effect pigments, transparency effect pigments, thermochromic pigments, photochromic pigments, and luminescent pigments such as fluorescent pigments and phosphorescent pigments. Pigments may be present in amounts that do not impair the properties of the coating film made from the aqueous coating composition, in particular the peelability and transparency properties described below. For example, an aqueous coating composition may contain a pigment at a concentration of less than 2% by solids weight, based on the total solids weight of the aqueous coating composition, and may be less than 1.8%, less than 1.5%, even less than 1.2%, preferably less than 1%, less than 0.5%, less than 0.1%, or even 0 by solids weight.
[0041] Pigments useful in the present invention may include one or more opacifying pigments, colorants, or special effect pigments. Opacifying pigments include inorganic pigment particles that scatter essentially all wavelengths of visible light without high absorption. Specific examples of opacifying pigments include titanium dioxide (TiO2); metal oxides such as zinc oxide, tin oxide, antimony oxide, zirconium oxide, and lead oxide; zinc sulfide; lithopone; or mixtures thereof. Preferably, the amount of opacifying pigment is less than 1%, less than 0.5%, less than 0.1%, or even 0 by solids weight, based on the total solids weight of the aqueous coating composition.
[0042] The colorants useful in the present invention may include one or more of coloring pigments, dyes, and black pigments. The colorant particles include inorganic and organic colorant particles. Typically, the colorant particles have an average particle size in the range of 10 nm to 50 micrometers (μm), preferably in the range of 20 nm to 5 μm, and more preferably in the range of 40 nm to 2 μm. Soluble dyes may also be used. Suitable inorganic colorant particles include, for example, iron oxide pigments such as goethite, lepidocrocite, hematite, maghemite, and magnetite; chromium oxide pigments; cadmium pigments such as cadmium yellow, cadmium red, and cadmium cinnabar; bismuth pigments such as bismuth vanadate and bismuth molybdate vanadate; mixed metal oxide pigments such as cobalt green titanate; chromate and molybdate pigments such as chromium yellow, molybdate red, and molybdate orange; ultramarine pigments; cobalt oxide pigments; nickel antimony titanate; lead chromium; blue iron pigment; and carbon black. One group of preferred inorganic colorant particles is selected from bismuth pigments; mixed metal oxide pigments; chromate and molybdate pigments; ultramarine pigments; cobalt oxide pigments; nickel antimony titanate; lead chromium; blue iron pigment; and carbon black. Suitable organic colorant particles include, for example, azo pigments, monoazo pigments, diazo pigments, azo pigment lakes, β-naphthol pigments, naphthol AS pigments, benzimidazolone pigments, diazo condensation pigments, metal complex pigments, isoindolinone and isoindoline pigments, polycyclic pigments, phthalocyanine pigments, quinacridone pigments, perylene and perinone pigments, thioindigo pigments, anthrapyrimidone pigments, flavanthron pigments, antantron pigments, dioxazine pigments, triarylcarbonium pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, and mixtures thereof.
[0043] In the present invention, useful special effect pigments may be transparent effect pigments such as transparent iron oxide.
[0044] The aqueous coating compositions of the present invention may optionally contain small amounts of one or more (E) fillers. Fillers as used herein include organic and inorganic filler particles (different from the (D) pigments described above) and do not impart primary color or opacity to compositions containing them. The amount of filler may be less than 1%, less than 0.5%, less than 0.1%, or even 0, based on the total solids weight of the aqueous coating composition. Preferably, the aqueous coating composition does not contain fillers. Suitable inorganic fillers include, for example, metal oxides such as aluminum oxide and silicon oxide; calcium carbonate, calcium sulfate, barium sulfate, mica, clay, calcined clay, feldspar, nepheline syenite, wollastonite, diatomaceous earth, magnesium silicate, alumina silicate, talc, and combinations thereof. Organic fillers include, for example, polymer particles containing one or more voids when dry, polymer particles without voids, or mixtures thereof. Polymer particles containing one or more voids upon drying are typically core-shell polymer particles in which the polymer particles contain at least one void (often referred to as "opaque polymers") upon drying, such as ROPAQUE® Ultra E opaque polymer (ROPAQUE is a trademark of The Dow Chemical Company), commercially available from The Dow Chemical Company. Polymer particles without voids may have an average particle size of 1 to 20 μm according to ASTM E2651-10 and typically provide a matting effect to compositions. Examples of such fillers include polyethylene (PE) waxes, such as ULTRALUBE® E-340 PE wax emulsion available from The Keim-Additive Co., CERAFLOUR® 929 pulverized PE wax available from BYK Additives and Instruments, DEUTERON® MK polyurea matting agent available from Deuteron Co., or mixtures thereof.
[0045] The aqueous coating composition of the present invention may or may not contain one or more defoaming agents. “Defoaming agent” as used herein refers to a chemical additive that reduces and inhibits foam formation. The defoaming agent may be a silicone-based defoaming agent, a mineral oil-based defoaming agent, an ethylene oxide / propylene oxide-based defoaming agent, an alkyl polyacrylate, or a mixture thereof. Suitable commercially available defoaming agents include, for example, TEGO® Airex 902 W and TEGO Foamex 1488 polyethersiloxane copolymer emulsions, both available from Evonik Industrial; BYK®-024 silicone defoaming agent, available from BYK; NOPCO® NDW and NXZ mineral oil defoaming agents, available from San Nopco; DOWSIL® 109F and 106F defoaming agents (DOWSIL is a trademark of The Dow Chemical Company), available from The Dow Chemical Company; or a mixture thereof. The defoaming agent may be present in concentrations of 0-1%, 0.01%-0.8%, or 0.1%-0.6% by weight, based on the total solids content of the aqueous coating composition.
[0046] The aqueous coating composition of the present invention may or may not contain one or more thickening agents, also known as "rheological modifiers." The thickening agents may include polyvinyl alcohol (PVA), clay materials, acid derivatives, acid copolymers, urethane association type thickening agents (UAT), polyether urea polyurethane (PEUPU), polyether polyurethane (PEPU), or mixtures thereof. Suitable examples of thickeners include alkali swellable emulsions (ASE) such as sodium or ammonium neutralized acrylic acid polymers, hydrophobically modified alkali swellable emulsions (HASE) such as hydrophobically modified acrylic acid copolymers, associative thickeners such as hydrophobically modified ethoxylated urethane (HEUR), and cellulose thickeners such as methylcellulose ether, hydroxymethylcellulose, hydroxyethylcellulose, hydrophobically modified hydroxyethylcellulose, sodium carboxymethylcellulose, sodium carboxymethyl 2-hydroxyethylcellulose, 2-hydroxypropylmethylcellulose, 2-hydroxyethylmethylcellulose, 2-hydroxybutylmethylcellulose, 2-hydroxyethylethylcellulose, and 2-hydroxypropylcellulose. Preferably, the thickener is HEUR-based. The thickener may be present in concentrations of 0-3% by weight, 0.1%-2.5% by weight, or 0.3%-2.0% by weight, based on the total solids content of the aqueous coating composition.
[0047] The aqueous coating composition of the present invention may contain, or may not contain, one or more neutralizing agents in an amount sufficient to adjust the pH value of the aqueous coating composition to, for example, a range of 7 to 9. The neutralizing agent may include an organic base, an inorganic base, or a mixture thereof. Suitable neutralizing agents include, for example, ammonia, sodium hydroxide, potassium hydroxide, zinc oxide, monoethanolamine, triethylamine, diethylamine, dimethylamine, sodium borate, potassium borate, aluminum hydroxide, 2-amino-2-methyl-1-propanol, or a combination thereof. 2-amino-2-methyl-1-propanol is preferred as the neutralizing agent.
[0048] In addition to the above components, the aqueous coating composition of the present invention may further contain one or a combination of the following additives: buffering agents, dispersants, wetting agents, antifungal agents, biocides, antiskinning agents, fluidizing agents, antioxidants, plasticizers, leveling agents, and grinding vehicles. These additives may be present in a total amount of 0 to 5% by weight or 0.01% to 2% by weight, based on the total solids weight of the aqueous coating composition.
[0049] The aqueous coating composition of the present invention can be prepared using techniques known in the field of coatings. A method for preparing the aqueous coating composition of the present invention may involve mixing an aqueous polyurethane dispersion, an amphoteric surfactant, and a light absorber and / or light stabilizer. Any other optional components may also be added as described above. The components in the aqueous coating composition may be mixed in any order to provide the aqueous coating composition. Any of the optional components described above may also be added to the composition during or before mixing to form the aqueous coating composition.
[0050] The aqueous coating composition of the present invention provides a coating film that, when applied to a substrate and dried, exhibits good peelability to various surfaces, including glass, tin, and the surface of coated metal substrates. "Good peelability" means a coating that has a peelability level of 4 or higher, or even 5, on the surface of all substrates, including glass, tin, and metals pre-coated with a two-component polyurethane coating (described below), both before and after exposure to a 500-hour QUV test using a QUV accelerated weathering tester (also called "post-QUV peelability"). In addition, it is also desirable that the coating has high tensile strength so that the coating has sufficient durability during its service life. When dried, the aqueous coating composition provides a coating with a tensile strength of at least 8 MPa, good water resistance rated 4 or higher, and good transparency with a transmittance value of over 85% (preferably 90% or higher) and a haze value of less than 10% (preferably 5% or lower), according to JG / T 172-2014. All properties are measured according to the test methods described in the Examples section below.
[0051] The present invention also relates to a method for preparing a release coating (i.e., a coating film) from the above-described aqueous coating composition. The method comprises (I) providing the above-described aqueous coating composition, (II) applying the aqueous coating composition to a substrate, and (III) drying the applied coating composition, or allowing it to dry, thereby forming a release coating, preferably a transparent release coating. "Transparent coating" means a coating that exhibits a transmittance value greater than 85% and a haze value less than 10% as measured using a Transmittance and Haze Tester apparatus according to ASTM D1003 (further details are provided in the transparency test below). The aqueous coating composition can be applied to and adhered to a variety of substrates to protect the substrate surface from UV and water exposure, while being easily removable (i.e., exhibiting good release properties). Examples of suitable substrates include wood, metal, plastics such as polyvinyl chloride and polyurethane, foam, stone, elastomer substrates, glass, cloth, concrete, tile, putty, or cement-based substrates. The surface of the substrate may be either a metal surface (e.g., a steel surface) or a metal surface coated such that at least a portion of the substrate surface is covered by such a coating (also known as a "painted metal surface"). For example, the substrate may be a metal substrate coated with a coating other than the release coating of the present invention (also known as a "precoat"), such as an epoxy coating, a two-component polyurethane coating, or an aqueous acrylic coating, preferably a two-component polyurethane coating. In particular, the two-component polyurethane coating is prepared by an aqueous composition comprising (a) a hydroxy-containing acrylic polymer dispersion and (b) an isocyanate, for example, a hydrophilic aliphatic isocyanate based on HDI, which can be commercially available from Covestro Chemical as BAYHYDUR XP-2655. Subsequently, the aqueous coating composition of the present invention is applied onto the precoat, thereby forming the release coating on the precoat such that the precoat is located between the release coating and the substrate.Remarkably, the aqueous coating composition can provide good peelability from a variety of substrates, including glass, tin, and polyurethane-coated metal substrates, even after UV exposure and water resistance testing, achieving a peelability rating of 4 or higher on all of these substrates (further details are provided in the Examples section below). The aqueous coating composition is suitable for a wide range of applications, including marine protective coatings, automotive coatings, traffic coatings, exterior insulation finishing systems (EIFS), roof mastic, wood coatings, coil coatings, plastic coatings, can coatings, building coatings, and civil engineering coatings. The aqueous coating composition is particularly suitable for building coatings for glass exteriors, as well as protective coatings for electronic devices and automobiles.
[0052] The aqueous coating composition may be applied by conventionally used means including brushing, dipping, rolling, and spraying, preferably spraying. Standard spraying techniques and equipment for spraying, such as air atomization spraying, air spraying, aerosol spraying, high-volume low-pressure spraying, and electrostatic spraying such as electrostatic bell coating, can be used, either manually or automatically. The aqueous coating composition may be dried at room temperature (23°C) or at high temperatures, for example, above 23°C to 60°C, thereby forming a release film (which is a release coating). [Examples]
[0053] Some embodiments of the present invention are described herein in the following examples, and all percentages (%) are weight percentages of the composition unless otherwise specified. Table 1 lists the materials to be used in the coating composition samples described herein below. Note: "PUD" stands for polyurethane dispersion.
[0054] [Table 1] BAYDERM, TRITON, ACRYSOL, DOWSIL, TERGITOL, ROVACE, ROPAQUE, and PROSPERSE are all trademarks of The Dow Chemical Company.
[0055] IE 1-8 Aqueous Coating Compositions Table 2 shows the component composition of the IE sample, and the amount of each component is reported in grams (g). In the first step, the PUD binder was added to the tank, followed by the addition of a neutralizing agent, and the PUD binder was neutralized to a pH value in the range of 7 to 9 while stirring. Next, a mixture of surfactant and light absorber was supplied to the tank over 30 minutes. The wetting agent was added over 20 minutes while stirring, followed by the addition of a leveling agent, rheological modifier, and deionized (DI) water if used. Finally, biocides and defoamers, if present, were added to form the aqueous coating composition. The mixture was stirred using a high-speed disperser at a speed in the range of 400 to 800 revolutions per minute (RPM).
[0056] CE 1-13 and 15 Aqueous Coating Compositions Samples CE 1-13 and 15 were prepared substantially in the same manner as IE 1-8 above, using the amounts of each component reported in grams (g), according to the formulations shown in Table 3. To prepare samples containing pigments and / or matting agents, the pigments and / or matting agents were added immediately after the wetting agent.
[0057] CE 14 Aqueous Coating Composition The component composition of CE 14 is shown in Table 3, and the amount of each component is reported in grams. CE 14 was prepared using the same procedure as IE 1-8 described above, except that the first step (the step before adding the mixture of surfactant and light absorber) was performed as follows.
[0058] AMP-95 was added to the acrylic latex binder to neutralize the binder to a pH of 7-9. Ultra E opaque polymer was added to the binder over 30 minutes using a high-speed disperser with stirring at a speed in the range of 400-800 RPM. Then, a fusion aid was added over 20 minutes.
[0059] Samples of the coating compositions obtained above were evaluated for peelability, tensile strength, water resistance, and transparency according to the following test methods.
[0060] Peel test The peel test is used to determine the ease of removal, or peelability, of the film (i.e., coating) formed from the coating composition. The test coating compositions were sprayed onto glass, tin, and PU-coated Q-PANEL steel substrates, respectively. The resulting panels were dried at room temperature for 7 days to obtain coated panels with a dry film thickness of 20–50 μm. The glass, tin, and steel substrates are all available from Q-Lab. The PU-coated steel was prepared by mixing a PROSPERSE 500 dispersion with XP-2655 isocyanate in a 1.2:1 NCO / OH molar ratio, then applying the resulting two-component (2K) aqueous PU composition onto the steel, followed by curing the PU composition to form steel pre-coated with a PU coating (also known as "PU-coated steel"). When PU-coated steel was used as the substrate, the test coating composition was applied onto the PU coating layer of the PU-coated steel.
[0061] Some of the obtained coated panels were directly evaluated for film peelability (indicated as "Pre-QUV Peelability") according to the peel test and evaluation criteria described below, however, some coated panels were first exposed to a QUV test before the peel test. The QUV test was performed by placing the coated panels in the QUV chamber of a QUV accelerated weathering tester (model: Q-Lab Co. QUV / SPRAY-67) for 500 hours, then removing them and cooling to room temperature for 24 hours. Subsequently, the coated panels obtained after the QUV test / exposure were evaluated according to the peel test and evaluation criteria described below to determine the peelability, indicated as "Post-QUV Peelability".
[0062] The films on the coated panels (before and after QUV exposure, respectively) were peeled off by hand, and their ease of removal (i.e., peelability) was evaluated on a scale of 1 to 5. 1. The film is extremely difficult to remove by hand, and when removed using tools, it tends to crumble during the removal process. 2. The film is difficult to peel off by hand and tends to crumble rather than peel off as a continuous sheet. 3. The film can be peeled off by hand with considerable effort, leaving behind residue on more than 20% of the panel's surface area. 4. The film can be peeled off by hand with little effort, either as a continuous sheet or leaving a residue of less than 5% of its surface area. 5. The film peels off almost effortlessly as a continuous sheet (i.e., the film does not break), and no residue is left behind.
[0063] For all glass, tin, and PU-coated steel substrates, the acceptable rating for both pre-QUV and post-QUV peelability must be 4 or higher. A higher rating indicates better peelability.
[0064] Tensile test The test coating composition was applied to release paper using an applicator to prepare a 300 μm thick wet film, which was then dried for 7 days in a controlled temperature chamber (CTR) (23 ± 2°C, 50% to 60% relative humidity). The resulting dried films, ranging in thickness from 50 to 70 μm, were peeled from the release paper by hand, turned over, and dried for another 7 days in the CTR. The resulting dried films were cut into dogbone test pieces and measured using a Universal Testing Machine (AI-7000M, Gotech Testing Machines Co., Ltd.) according to the JG / T 172-2005 method. The acceptable tensile strength is at least 8 MPa.
[0065] Water resistance test The test coating composition was applied from the Q-Lab onto a glass substrate using an applicator to create a wet film with a thickness of 200 μm. This film was then dried at room temperature for 7 days to form a coated panel with a dry film (thickness: 50 μm). The coated panel was immersed in water for 24 hours, then removed and the coating film was visually inspected. The appearance of the coating film was evaluated on a scale of 1 to 5, as described below. 1. When the panel is removed from the water, the film is completely destroyed and peels off from the substrate. 2. The film turns white, wrinkles, and begins to tear in places. 3. The film turns white, develops many wrinkles, and cannot be restored to its appearance before immersion in water after 2-4 hours. 4. The film will turn white and become wrinkle-free. After 2-4 hours, the film can recover to its appearance before being immersed in water. 5. The film shows no difference compared to its appearance before immersion in water.
[0066] If the appearance of the coating film on the coated panel after water immersion was rated 4 or higher, the panel was further dried at room temperature for 7 days, and its peelability was evaluated according to the same evaluation criteria as described in the peel test above. If the appearance of the coated panel after water immersion was rated less than 4, the test was stopped.
[0067] Coated panels that receive a rating of 4 or higher for both appearance and peelability have passed the water resistance test and demonstrate good water resistance. If a panel receives either an appearance rating of 3 or lower, or an appearance rating of 4 or higher and a subsequent peelability rating of 3 or lower, the panel has failed the water resistance test and indicates poor water resistance.
[0068] Transparency Test A test coating composition was applied to release paper using an applicator to prepare a 200 μm thick wet film, which was then dried at room temperature for 7 days. After drying, the resulting dry coating film, with a thickness of 50-70 μm, was peeled off the release paper by hand. The transmittance and haze values of the coating film were measured using a Transmittance and Haze Tester (YH1000, manufactured by Shenzhen China Technology Co., Ltd. (Threenh)) according to ASTM D1003. Acceptable transparency characteristics require a transmittance value greater than 85% (>85%) and a haze value less than 10% (<10%).
[0069] The characteristics of the IE 1-8 and CE 1-15 samples are shown in Tables 2 and 3, respectively. As shown in Table 2, the IE 1-8 samples provided good peelability on the surface of all substrates (i.e., glass, tin, and PU-coated steel) with each rating ≥ 4, both before and after QUV exposure. The desired tensile strength (at least 8 MPa) and good water resistance (rating ≥ 4) were simultaneously demonstrated, as indicated by transmittance values > 85% and haze values < 10%, indicating good transparency. All IE samples yielded a transparent coating film (green film for IE4).
[0070] As shown in Table 3, using samples CE 1, 3, and 5, and similar types of PUD, surfactant, and defoamer, Examples 3, 1, and 2 of U.S. Patent No. 11008468(B2) were substantially repeated, respectively. The coating films produced from these samples were all black, opaque (not transparent) films and failed to meet the release requirements for all substrates. It should be noted that even when the pigment and matting agent were omitted (CE 2, 4, and 6), the transparency of the resulting coating films improved, but these samples still failed to pass the release test simultaneously for all substrates (for example, one or more substrates had a release rating of less than 4).
[0071] Compared to IE 1, CE 7, containing PUD-4 based on polycarbonate ester polyol and IPDI, showed poor peelability (before and / or after QUV) on all three types of substrates. CE 8, containing PUD-3 derived from polyether polyol and IPDI, showed poor peelability on PU-coated steel (before QUV), and after QUV exposure, showed poor peelability, poor water resistance, and unacceptable transparency (high haze values, etc.) on tin and PU-coated steel. Samples containing DS-4 anionic surfactant (CE 9) or 15-S-40 nonionic surfactant (CE 10) (instead of amphoteric surfactants) all showed significantly lower peelability on all substrates than the IE 1 sample containing CAB amphiphilic surfactant, both before and after QUV exposure. CE 11, containing aromatic polyurethane dispersion (PUD-2), showed poor peelability (before and after UV exposure) on one or more types of substrates, and exhibited worse transparency and water resistance than the IE sample. CE 12, containing a polyurethane dispersion (PUD-5) derived from a monofunctional polyalkylene ether, failed to meet the requirements for peelability on tin and PU-coated steel substrates, peelability after QUV exposure on all substrates, and water resistance. Samples containing MDI and (polyether and polyester)-based nonionic PUD-6 (CE 13) or 15% CAB (CE 15) exhibited poorer peelability (before and after UV exposure), lower tensile strength, and poorer transparency on all substrates compared to the IE samples. The acrylic coating system of CE 14 provided an opaque coating film. In contrast, the IE samples of the present invention provided a transparent coating film with significantly improved tensile strength and water resistance compared to CE 14, without compromising peelability.
[0072] [Table 2]
[0073] [Table 3]
Claims
1. A water-based coating composition, (A) an aqueous polyurethane dispersion containing the reaction products of components (i) and (ii), (i) an isocyanate component comprising an aliphatic or alicyclic polyisocyanate containing at least two isocyanate groups, (ii) (iii-a) a polyol containing a lactone-based polyester polyol, (iii-b) an anionic emulsifier containing at least one isocyanate-reactive group and an anionic group or a latent anionic group, and (iii-c) an isocyanate-reactive component containing a monofunctional polyalkylene ether containing one hydroxyl group or an amino group, in an amount of 0 to less than 1.0% by weight based on the total weight of the isocyanate component and the isocyanate-reactive component; an aqueous polyurethane dispersion comprising: (B) Based on the total solids weight of the aqueous coating composition, an amphoteric surfactant having an isoelectric point at pH 3 to pH 8 is present in an amount of 0.1% to 10.0% by solids weight, (C) An aqueous coating composition comprising a light absorber, a light stabilizer, or a mixture thereof.
2. The aqueous coating composition according to claim 1, wherein the isocyanate component comprises isophorone diisocyanate.
3. The aqueous coating composition according to claim 1, wherein the lactone-based polyester polyol is a polycaprolactone polyol.
4. (ii-a) The aqueous coating composition according to claim 1, wherein the polyol comprises 80% to 100% by weight of the lactone-based polyester polyol, based on the total weight of the polyol in the isocyanate-reactive component.
5. The aqueous coating composition according to claim 1, wherein the anionic emulsifier is selected from dihydroxyalkyl carboxylic acid, dihydroxysulfonic acid, dihydroxyphosphonic acid, or a mixture thereof.
6. The aqueous coating composition according to claim 1, wherein the amphoteric surfactant is a compound selected from the group consisting of aminocarboxylic acid; aminocarboxylic acid substituted with a fluorocarbon substituent, a siloxane substituent, or a combination thereof; amphoteric imidazoline derivative; amphoteric imidazoline derivative substituted with a fluorocarbon substituent, a siloxane substituent, or a combination thereof; betaine; betaine substituted with a fluorocarbon substituent, a siloxane substituent, or a combination thereof; or a mixture thereof.
7. The aqueous coating composition according to claim 1, comprising 0.1 to 15% by weight of the light absorber, the light stabilizer, or a mixture thereof, based on the total solids weight of the aqueous coating composition.
8. The aqueous coating composition according to claim 1, comprising less than 1% by solids weight of the filler based on the total solids weight of the aqueous coating composition.
9. The aqueous coating composition according to claim 1, wherein the aqueous polyurethane dispersion is present at a concentration of 60% to 98% by solids weight, based on the total solids weight of the aqueous coating composition.
10. A method for preparing a peelable coating, (I) To provide an aqueous coating composition according to any one of claims 1 to 9, (II) Applying the aqueous coating composition to the surface of the substrate, (III) A method comprising drying or freezing an applied aqueous coating composition to form a peelable coating.