EP4085108A1

EP4085108A1 - Aqueous composition and method of preparing the same

Info

Publication number: EP4085108A1
Application number: EP19958139.8A
Authority: EP
Inventors: Yawei Xu; Xiaohong Yang; Dong Yun; Yujiang Wang; Yan Wu; Fengzhe SHI; Juan ZHAO
Original assignee: Dow Global Technologies LLC; Rohm and Haas Co
Current assignee: Dow Global Technologies LLC; Rohm and Haas Co
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2022-11-09
Also published as: WO2021134164A1; CN114867800A

Abstract

An aqueous composition with extended working time and providing films with high clarity, comprising: (a) an oligomer with a number average molecular weight of from 250 to 30,000 g/mol comprising, by weight based on the weight of the oligomer, from 5%to 20%of structural units of an acid monomer, a salt thereof, or mixtures thereof; (b) a hydroxypropyl methylcellulose with a degree of substitution of methoxyl groups of 1.5 or higher; and (c) a diol containing from 2 to 6 carbon atoms and having a boiling point of from 110 to 280℃.

Description

Aqueous Composition and Method of Preparing the Same

FIELD OF THE INVENTION

The present invention relates to an aqueous composition and a method of preparing the same.
INTRODUCTION
American style furniture is a very popular furniture segment which uses solvent-based coating system with more than 15-20 coats to make fresh wood panels finally look old. In such coating system, wiping stains play a key role in staining wood and giving furniture an antique look. Conventional wiping stains typically comprise, by weight based on the total weight of the wiping stain, 10-15%of an oil, 30%of a colorant, and from 55%to 60%of a solvent. Aqueous (also known as waterborne) coating compositions are becoming increasingly more important than solvent-based coating compositions for less environmental problems. One of the key unmet needs for incumbent waterborne wiping stains is short working time (e.g., about 15-20 minutes) , which limits their applications on large surfaces such as big furniture. In addition, dry film clarity of wiping stains is critical to demonstrate desired stain colors and have limited impacts on the film clarity of the whole coating system.
Therefore, it is desirable to provide an aqueous composition particularly suitable for wiping stains that has extended working time and can provide films made therefrom with high clarity.
SUMMARY OF THE INVENTION
The present invention provides an aqueous composition comprising a novel combination of a specific cellulose ether, a diol having from 2 to 6 carbon atoms and a certain boiling point, and an oligomer comprising structural units of an acid monomer, a salt thereof, or mixtures thereof. Such aqueous composition of the present invention, particularly suitable for wiping stains, demonstrates an extended working time of at least 34 minutes at room temperature (20-25℃) and 45±5%relative humidity. The aqueous composition of the present invention upon drying can also provide films with a clarity of 80%or higher. These properties may be measured according to the test methods described in the Examples section below.
In a first aspect, the present invention is an aqueous composition comprising:
(a) at least 3%, by weight based on the total weight of the aqueous composition, of an oligomer with a number average molecular weight of from 250 to 30,000 g/mol,
wherein the oligomer comprises, by weight based on the weight of the oligomer, from 5%to 20%of structural units of an acid monomer, a salt thereof, or mixtures thereof;
(b) from 45%to 65%of a hydroxypropyl methylcellulose with a degree of substitution of methoxyl groups of 1.5 or higher, by weight based on the total weight of the oligomer and the hydroxypropyl methylcellulose; and
(c) 2%or more, by weight based on the total weight of the aqueous composition, of a diol containing from 2 to 6 carbon atoms and having a boiling point of from 110 to 280℃.
In a second aspect, the present invention is a method of preparing the aqueous composition of the first aspect. The method comprises admixing:
(a) at least 3%, by weight based on the total weight of the aqueous composition, of an oligomer with a number average molecular weight of from 250 to 30,000 g/mol,
wherein the oligomer comprises, by weight based on the weight of the oligomer, from 5%to 20%of structural units of an acid monomer, a salt thereof, or mixtures thereof;
(b) from 45%to 65%, of a hydroxypropyl methylcellulose with a degree of substitution of methoxyl groups of 1.5 or higher, by weight based on the total weight of the oligomer and the hydroxypropyl methylcellulose; and
(c) 2%or more, by weight based on the total weight of the aqueous composition, of a diol containing from 2 to 6 carbon atoms and having a boiling point of from 110 to 280℃.

DETAILED DESCRIPTION OF THE INVENTION

“Aqueous” dispersion herein means that particles dispersed in an aqueous medium. By “aqueous medium” herein is meant water and from 0 to 30%, by weight based on the weight of the medium, of water-miscible compound (s) such as, for example, alcohols, glycols, glycol ethers, glycol esters, and the like.
“Structural units” , also known as “polymerized units” , of the named monomer, refers to the remnant of the monomer after polymerization, that is, polymerized monomer or the monomer in polymerized form. For example, a structural unit of methyl methacrylate is as illustrated: where the dotted lines represent the points of attachment of the structural unit to the polymer backbone.
“Acrylic” in the present invention includes (meth) acrylic acid, alkyl (meth) acrylate, (meth) acrylamide, (meth) acrylonitrile and their modified forms such as hydroxyalkyl (meth) acrylate. Throughout this document, the word fragment “ (meth) acryl” refers to both “methacryl” and “acryl” . For example, (meth) acrylic acid refers to both methacrylic acid and acrylic acid, and methyl (meth) acrylate refers to both methyl methacrylate and methyl acrylate.
The aqueous composition of the present invention comprises one or more oligomers. “Oligomer” herein refers to a polymer having a number average molecular weight (Mn) of 30,000 g/mol or less. The oligomer may have a Mn of 250 g/mol or more, 500 g/mol or more, 800 g/mol or more, 1,000 g/mol or more, 1, 200 g/mol or more, 1,500 g/mol or more, 1, 800 g/mol or more, 2,000 g/mol or more, 3,000 g/mol or more, 3,500 g/mol or more, 4,000 g/mol or more, 4,500 g/mol or more, or even 5,000 g/mol or more, and at the same time, 30,000 g/mol or less, 28,000 g/mol or less, 25,000 g/mol or less, 22,000 g/mol or less, 20,000 g/mol or less, 15,000 g/mol or less, 12,000 g/mol or less, 10,000 g/mol or less, 9,500 g/mol or less, 9,000 g/mol or less, 8,000 g/mol or less, 7,000 g/mol or less, or even 6,500 g/mol or less. Mn may be determined by gel permeation chromatography (GPC) analysis using a polystyrene standard as described in the Examples section below or calculation according to the following equation:
Mn= [W (monomer) +W (CTA) ] /Mole (CTA)
where W (monomer) is the total weight of monomers used for preparing the oligomer, W (CTA) is the total weight of a chain transfer agent used for preparing the oligomer, and Mole (CTA) is the total moles of the chain transfer agent used for preparing the oligomer.
The oligomer useful in the present invention may comprise structural units of one or more acid monomers, salts thereof, or mixtures thereof. The acid monomers are selected from carboxylic acid monomers, phosphorous-containing acid monomers, sulfonic acid monomers; salts thereof; or mixtures thereof. The carboxylic acid monomers can be α, β-ethylenically unsaturated carboxylic acids, monomers bearing an acid-forming group which yields or is subsequently convertible to, such an acid group (such as anhydride, (meth) acrylic anhydride, or maleic anhydride) ; or mixtures thereof. Specific examples of carboxylic acid monomers include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, or mixtures thereof. Examples of suitable phosphorous-containing acid monomers and salts thereof include phosphoalkyl (meth) acrylates such as phosphoethyl (meth) acrylate, phosphopropyl (meth) acrylate, phosphobutyl (meth) acrylate, salts thereof, and mixtures thereof; CH ₂=C (R ₁) -C (O) -O- (R ₂O) _q-P (O) (OH) ₂, wherein R ₁=H or CH ₃, R ₂=alkylene, such as an ethylene group, a propylene group, or a combination thereof; and q=1-20, such as SIPOMER PAM-100, SIPOMER PAM-200, SIPOMER PAM-300, SIPOMER PAM-600 and SIPOMER PAM-4000 all available from Solvay; phosphoalkoxy (meth) acrylates such as phospho ethylene glycol (meth) acrylate, phospho di-ethylene glycol (meth) acrylate, phospho tri-ethylene glycol (meth) acrylate, phospho propylene glycol (meth) acrylate, phospho di-propylene glycol (meth) acrylate, phospho tri-propylene glycol (meth) acrylate, salts thereof, and mixtures thereof. The sulfonic acid monomers and salts thereof may include sodium vinyl sulfonate (SVS) , sodium styrene sulfonate (SSS) , acrylamido-methyl-propane sulfonate (AMPS) and salts thereof; or mixtures thereof. Preferred acid monomers are selected from acrylic acid, methacrylic acid, itaconic acid, phosphoethyl (meth) acrylate, SIPOMER PAM-100, SIPOMER PAM-200, SIPOMER PAM-300, or mixtures thereof. The oligomer may comprise, by weight based on the weight of the oligomer, 5%or more of structural units of the acid monomer, 5.1%or more, 5.2%or more, 5.5%or more, 6% or more, 6.5%or more, 7%or more, 7.5%or more, 8%or more, 8.5%or more, 9.5%or more, or even 10%or more, and at the same time, 20%or less, 19.5%or less, 19%or less, 18.5%or less, 18%or less, 17.5%or less, 17%or less, 16.5%or less, 16%or less, 15.5%or less, 15.0%or less, 14.5%or less, 14.0%or less, 13.5%or less, 13.0%or less, 12.5%or less, or even 12%or less. “Weight of the oligomer” in the present invention refers to dry weight of the oligomer.
The oligomer useful in the present invention may also comprise structural units of one or more ethylenically unsaturated functional monomers carrying at least one functional group selected from a carbonyl, acetoacetate, ureido, silane, hydroxy, amide, alkyloxy, or amino group. Suitable ethylenically unsaturated functional monomers may include, for example, amino-functional monomers such as dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylate; ureido-functional monomers such as hydroxyethyl ethylene urea methacrylate, hydroxyethyl ethylene urea acrylate, such as SIPOMER WAM II; monomers bearing acetoacetate-functional groups such as acetoacetoxyethyl methacrylate (AAEM) , acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxypropyl acrylate, allyl acetoacetate, acetoacetoxybutyl methacrylate, acetoacetoxybutyl methacrylate, acetoacetamidoethyl methacrylate, acetoacetamidoethyl acrylate; monomers bearing carbonyl-containing groups such as diacetone acrylamide (DAAM) , diacetone methacrylamide; vinyltrialkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, vinyldimethylethoxysilane vinylmethyldiethoxysilane or (meth) acryloxyalkyltrialkoxysilanes such as (meth) acryloxyethyltrimethoxysilane and (meth) acryloxypropyltrimethoxysilane; hydroxy-functional alkyl (meth) acrylates including hydroxyethyl (meth) acrylates such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate; hydroxypropyl (meth) acrylates such as 2-hydroxypropylacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, and 3-hydroxypropyl methacrylate; alkoxylated (meth) acrylates such as methoxy polyethylene glycol methacrylate; (meth) acrylamides such as acrylamide and methacrylamide; or mixtures thereof. The oligomer may comprise, by weight based on the weight of the oligomer, zero or more of structural units of the ethylenically unsaturated functional monomer, 0.1%or more, 0.5%or more, 1%or more, 1.5%or more, 2%or more, 2.5%or more, or even 3%or more, and at the same time, 20%or less, 18%or less, 15%or less, 12%or less, 10%or less, 9%or less, 8%or less, 7%or less, 6%or less, 5%or less, or even 4%or less.
The oligomer useful in the present invention may further comprise structural units of one or more additional nonionic ethylenically unsaturated monomers that are different from the monomers described above. Suitable additional ethylenically unsaturated nonionic monomers may include, for example, alkyl esters of (meth) acrylic acid, vinyl aromatic monomers such as styrene, acrylonitrile, vinyl esters such as vinyl acetate, or mixtures thereof. The alkyl esters of (meth) acrylic acid may contain an alkyl having from 1 to 18 carbon atoms, from 1 to 12 carbon atoms, or from 1 to 8 carbon atoms, including, for example, methyl (meth) acrylate, ethyl acrylate, butyl acrylate, n-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl acrylate, or mixtures thereof. The oligomer may comprise, by weight based on the weight of the oligomer, from 60%to 95.4%, from 65%to 90%, or from 70%to 88%of structural units of the additional ethylenically unsaturated nonionic monomers.
Types and levels of the monomers described above may be chosen to provide the oligomer with a glass transition temperature (Tg) suitable for different applications. The oligomer useful in the present invention may have a T _g of from -10 to 100℃, from 0 to 95℃, or from 10 to 90℃. Tg herein may be measured by differential scanning calorimetry (DSC) according to the test method described below.
The oligomer useful in the present invention may be soluble in water at room temperature or may be present as particles with a particle size of from 10 nanometers (nm) to 500 nm, from 20 nm to 400 nm, from 70 nm to 300 nm, or from 70 nm to 250 nm. Particle size can be determined by the test method described in the Examples section below.
The aqueous composition of the present invention may comprise, by weight based on the total weight of the aqueous composition, 3%or more of the oligomer, for example, 4%or more, 4.5%or more, 5%or more, 5.5%or more, 6%or more, or even 6.5%or more, and at the same time, 25%or less, 22%or less, 20%or less, 18%or less, 15%or less, 12%or less, 10%or less, or even 8%or less.
The aqueous composition of the present invention may optionally comprise one or more additional emulsion polymers that are different from the oligomer, for example, a film-forming polymer (also known as a “binder” ) . The additional emulsion polymer may include, for example, an acrylic polymer, a styrene-acrylic copolymer, a blend of polyurethane and an acrylic polymer or copolymer, a polyurethane-acrylic hybrid polymer, or mixtures thereof. The additional emulsion polymer typically comprises, by weight based on the weight of the additional emulsion polymer, from 0 to 10%or from 0.5%to 8%of one or more acid monomers including those described above in the oligomer section. Preferably, the aqueous composition comprises a substantial absence of the additional emulsion polymer. A substantial absence means less than 10%, by weight based on the weight of the oligomer, of the additional emulsion polymer, for example, less than 8%, less than 5%, less than 3%, less than 1%, or even zero.
The process of preparing the oligomer useful in the present invention may be conducted by free-radical polymerization, such as suspension polymerization or emulsion polymerization, of the monomers described above. Emulsion polymerization is a preferred process. Total weight content of monomers for preparing the oligomer is equal to 100%. A mixture of monomers for preparing the oligomer may be added neat or as an emulsion in water; or added in one or more additions or continuously, linearly or nonlinearly, over the reaction period of preparing the oligomer. Temperature suitable for emulsion polymerization processes may be lower than 100℃, in the range of from 30 to 95℃, or in the range of from 50 to 90℃. The polymerization can be conducted by one-stage or multistage free-radical polymerization which at least two stages are formed sequentially.
In the polymerization process of preparing the oligomer, free radical initiators may be used. The polymerization process may be thermally initiated or redox initiated emulsion polymerization. Examples of suitable free radical initiators include hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, ammonium and/or alkali metal persulfates, sodium perborate, perphosphoric acid, and salts thereof; potassium permanganate, and ammonium or alkali metal salts of peroxydisulfuric acid. The free radical initiators may be used typically at a level of 0.01 to 3.0%, by weight based on the total weight of monomers. Redox systems comprising the above described initiators coupled with a suitable reductant may be used in the polymerization process. Examples of suitable reductants include sodium sulfoxylate formaldehyde, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids, such as sodium sulfite, bisulfite, thiosulfate, hydrosulfite, sulfide, hydrosulfide or dithionite, formadinesulfinic acid, acetone bisulfite, glycolic acid, hydroxymethanesulfonic acid, glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaric acid and salts of the preceding acids. Metal salts of iron, copper, manganese, silver, platinum, vanadium, nickel, chromium, palladium, or cobalt may be used to catalyze the redox reaction. Chelating agents for the metals may optionally be used.
In the polymerization process of preparing the oligomer, a surfactant may be used. The surfactant may be added prior to or during the polymerization of the monomers, or combinations thereof. A portion of the surfactant can also be added after the polymerization. These surfactants may include anionic and/or nonionic emulsifiers. Examples of suitable surfactants include alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates, sulfonates or phosphates; alkyl sulfonic acids; sulfosuccinate salts; fatty acids; ethylenically unsaturated surfactant monomers; and ethoxylated alcohols or phenols. In some preferred embodiments, the alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates surfactant are used. The surfactant is usually used in an amount of from 0.1%to 6%, preferably from 0.3%to 1.5%, by weight based on the weight of total monomers used for preparing the oligomer.
In the polymerization process of preparing the oligomer, a train transfer agent can be used to control the molecular weight of the oligomer. Examples of suitable chain transfer agents include 3-mercaptopropionic acid, dodecyl mercaptan, methyl 3-mercaptopropionate, butyl 3-mercaptopropionate, benzenethiol, azelaic alkyl mercaptan, or mixtures thereof. The chain transfer agent may be used in an effective amount to control the molecular weight of the oligomer. For example, the chain transfer agent may be used in an amount of from 0.1%to 5%, from 0.3%to 4%, from 0.4%to 3%, or from 0.45%to 2.5%, by weight based on the total weight of monomers used for preparing the oligomer.
After completing the polymerization of the oligomer, the obtained oligomer may be neutralized by one or more bases as neutralizers to a pH value, for example, at least 6, from 6 to 10, or from 7 to 9. The bases may lead to partial or complete neutralization of the ionic or latently ionic groups of the oligomer. Examples of suitable bases include ammonia; alkali metal or alkaline earth metal compounds such as sodium hydroxide, potassium hydroxide, calcium hydroxide, zinc oxide, magnesium oxide, sodium carbonate; primary, secondary, and tertiary amines, such as triethyl amine, ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, diethyl amine, dimethyl amine, di-npropylamine, tributylamine, triethanolamine, dimethoxyethylamine, 2-ethoxyethylamine, 3-ethoxypropylamine, dimethylethanolamine, diisopropanolamine, morpholine, ethylenediamine, 2-diethylaminoethylamine, 2, 3-diaminopropane, 1, 2-propylenediamine, neopentanediamine, dimethylaminopropylamine, hexamethylenediamine, 4, 9-dioxadodecane-1, 12-diamine, polyethyleneimine or polyvinylamine; aluminum hydroxide; or mixtures thereof.
In addition to the oligomer, the aqueous composition of the present invention may further comprise a polyfunctional carboxylic hydrazide containing at least two hydrazide groups per molecule. The polyfunctional carboxylic hydrazides may act as a crosslinker and may be selected from adipic dihydrazide, oxalic dihydrazide, isophthalic dihydrazide, polyacrylic polyhydrazide, or mixtures thereof. The polyfunctional carboxylic hydrazide may be present in an amount of from 0.5%to 10%, from 1%to 8%, or from 1.5%to 6%, by weight based on the weight of the oligomer.
The aqueous composition of the present invention may further comprise one or more hydroxypropyl methylcellulose having a degree of substitution of methoxyl groups of 1.5 or higher, for example, 1.6 or higher, 1.7 or higher, or even 1.8 or higher, and at the same time, 2.0 or lower, 1.95 or lower, or even 1.9 or lower. The degree of substitution of methoxyl groups is the average number of hydroxyl groups substituted by methoxyl groups per anhydroglucose unit in the cellulose ether. The degree of substitution can be determined by ¹H and ¹³C nuclear magnetic resonance (NMR) in DMSO-d ₆ (deuterated dimethyl sulfoxide) at 80℃. Analysis of the spectra was performed after identification of different signals according to literatures including, for example, Polymers, Volume 7, pages 777-803 (2015) ; Polymer, Volume 33, pages 4087-4094 (1992) ; and Journal of Polymer Science, Part A: Polymer Chemistry, Volume 40, pages 4167-4179 (2002) . The aqueous composition may comprise the hydroxypropyl methylcellulose in an amount of 45%or more, 45.5%or more, 46%or more, 46.5%or more, 47%or more, 47.5%or more, 48%or more, 48.5%or more, 49%or more, 49.5%or more, or even 50%or more, and at the same time, 65%or less, 64%or less, 63%or less, 62%or less, 61%or less, 60%or less, 59%or less, 58%or less, 57%or less, 56%or less, or even 55%or less, by weight based on the total weight of the oligomer and the hydroxypropyl methylcellulose. Weight of hydroxypropyl methylcellulose refers to the dry weight of the hydroxypropyl methylcellulose.
The aqueous composition of the present invention may further comprise one or more diols containing from 2 to 6 carbon atoms, from 2 to 5 carbon atoms, or from 2 to 4 carbon atoms. “Diols” herein refers a compound containing two hydroxy groups. The diols useful in the present invention may have a boiling point of from 110 to 280℃, from 130 to 270℃, from 140 to 260℃, from 150 to 250℃, from 160 to 245℃, from 170 to 240℃, from 175 to 230℃, from 180 to 225℃, or from 185 to 215℃. The boiling point of a liquid is the temperature at which its vapor pressure is equal to the external pressure on the surface of the liquid. The boiling point herein is defined as the temperature at which a diol boils at 760 mm Hg.The diols useful in the present invention may have the following formula (I) or (II) :
HO-R ¹-OH (I) ,
where R ¹ is a C ₂-C ₆ alkylene group; or
HO- (AO) n-H (II) ,
where n is from 1 to 3, each A is the same or different and selected from ethylene, propylene, butylene, or combinations thereof; provided that the total number of carbon atoms in formula (II) is no more than 6.
Examples of suitable diols in the present invention include propylene glycol, 1, 4-butylene glycol, ethylene glycol, diethylene glycol, or mixtures thereof. The diols may be present in the aqueous composition in an amount of 2%or more, by weight based on the total weight of the aqueous composition, for example, 2.1%or more, 2.2%or more, 2.3%or more, 2.4%or more, 2.5%or more, 2.6%or more, 2.7%or more, 2.8%or more, 2.9%or more, 3%or more, 3.1%or more, 3.2%or more, 3.3%or more, or even 3.4%or more, and at the same time, 30%or less, 28%or less, 25%or less, 22%or less, 21%or less, 20%or less, 19%or less, 18%or less, 17%or less, 15%or less, or even 14%or less.
The aqueous composition of the present invention may further comprise one or more colorants including, for example, phthalo blue, phthalo green, monoazo yellow, carbon black, or mixtures thereof. The colorant may be present in an amount of from 0 to 20%, from 0.1%to 18%, from 3%to 16%, by weight based on the total solids weight of the aqueous composition.
The aqueous composition of the present invention may further comprise one or more pigments and/or extenders. The term “pigment” refers to a material capable of materially contributing to the opacity or hiding capability of a coating. The term “extender” refers to a particulate material having a refractive index of less than or equal to 1.8 and greater than 1.3. Examples of suitable extenders include calcium carbonate, aluminium oxide (Al ₂O ₃) , clay, calcium sulfate, aluminosilicate, silicate, zeolite, mica, diatomaceous earth, solid or hollow glass, ceramic bead, or mixtures thereof. The pigment and extender may be present, by weight based on the total solids weight, in a combined amount of from zero to 20%, from 0.1%to 18%, or from 0.5%to 15%.
The aqueous composition of the present invention may further comprise one or more defoamers. “Defoamers” herein refer to chemical additives that reduce and hinder the formation of foams. Defoamers may be silicone-based defoamers, mineral oil-based defoamers, ethylene oxide/propylene oxide-based defoamers, alkyl polyacrylates, or mixtures thereof. Suitable commercially available defoamers include, for example, TEGO Airex 902 W and TEGO Foamex 1488 polyether siloxane copolymer emulsions both available from TEGO, BYK-024 silicone deformer available from BYK, or mixtures thereof. The defoamer may be present, by weight based on the total weight of the aqueous composition, generally from 0 to 4%, from 0.1%to 2%, or from 0.2%to 0.8%.
The aqueous composition of the present invention may further comprise one or more wetting agents. “Wetting agents” herein refer to chemical additives that reduce the surface tension of a composition, causing the composition to more easily spread across or penetrate the surface of a substrate. Wetting agents may be polycarboxylates, anionic, zwitterionic, or non-ionic. Suitable commercially available wetting agents include, for example, SURFYNOL 104 nonionic wetting agent available from Air Products, BYK-346 and BYK-349 polyether-modified siloxanes both available from BYK, or mixtures thereof. The wetting agent may be present, by weight based on the total weight of the aqueous composition, from 0 to 5%, from 0.01%to 2%, or from 0.2%to 1%.
The aqueous composition of the present invention may further comprise one or more coalescents. “Coalescents” herein refer to solvents that are different from the diol described above. Coalescents typically can fuse polymer particles into a continuous film under ambient conditions. Examples of suitable coalescents include 2-n-butoxyethanol, dipropylene glycol n-butyl ether, propylene glycol n-butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol n-propyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, triethylene glycol monobutyl ether, dipropylene glycol n-propyl ether, or mixtures thereof. Preferred coalescents include dipropylene glycol n-butyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, or mixtures thereof. The coalescent may be present, by weight based on the total weight of the aqueous composition, from 0 to 10%, from 0.01%to 9%, or from 1%to 8%.
In addition to the components described above, the aqueous composition of the present invention may further comprise any one or combination of the following additives: buffers, neutralizers, dispersants, humectants, mildewcides, biocides, anti-skinning agents, flowing agents, anti-oxidants, plasticizers, leveling agents, thixotropic agents, adhesion promoters, and grind vehicles. These additives may be present in a combined amount of from zero to 2.5%or from 0.01%to 2%, by weight based on the total weight of the aqueous composition.
The aqueous composition of the present invention may further comprise water. The aqueous composition may have a solids content of from 0.5%to 40%, from 1%to 30%, or from 1.5%to 25%, by weight based on the total weight of the aqueous composition. Depending on various solids contents of the aqueous composition, the aqueous composition of the present invention may comprise the hydroxypropyl methylcellulose in an amount of 6.1%or more, 6.2%or more, 6.3%or more, 6.4%or more, 6.5%or more, 7%or more, or even 7.5%or more, and at the same time, 10%or less, 9.5%or less, 9%or less, 8.5%or less, or even 8%or less, by weight based on the total weight of the aqueous composition.
The present invention also provides a method of preparing the aqueous composition, comprising: admixing the oligomer, the hydroxypropyl methylcellulose, and the diol, with other optional components described above, thus forming the aqueous composition of the present invention. The amount of each component used in the method is as described in the aqueous composition section above. Components in the aqueous composition may be mixed in any order to provide the aqueous composition of the present invention. Any of the above- mentioned optional components may also be added to the composition during or prior to the mixing to form the aqueous composition.
The aqueous composition of the present invention has an extended working time. For example, the aqueous composition, when applied to a substrate with a wet film thickness of 80±5 μm, has a working time of at least 34 minutes, at least 35 minutes, at least 36 minutes, at least 37 minutes, at least 38 minutes, or even at least 40 minutes, at room temperature (20-25℃) and 45±5%relative humidity. The aqueous composition of the present invention upon drying can also provide films (dry film thickness: 10±3 μm) with a clarity of 80%or higher, 82%or higher, 85%or higher, or even 90%or higher. The working time and clarity may be measured according to the test methods described in the Examples section.
A process of using the aqueous composition of the present invention may comprise the following: applying the aqueous composition to a substrate, and drying, or allowing to dry, the applied aqueous composition. The aqueous composition of the present invention can be applied to a substrate by incumbent means including brushing, dipping, rolling and spraying. The aqueous composition is preferably applied by brushing. After the aqueous composition of the present invention has been applied to a substrate, the aqueous composition can dry, or allow to dry, to form a film at room temperature, or at an elevated temperature, for example, from 35℃ to 60℃.
The aqueous composition of the present invention can be applied to, and adhered to, various substrates. Examples of suitable substrates include wood, metals, plastics, foams, stones, elastomeric substrates, glass, fabrics, concrete, or cementious substrates, particularly wood. The aqueous composition is particularly suitable for wood wiping stains. The aqueous composition can be used alone, or in combination with other coatings to form multilayer coatings.
EXAMPLES
Some embodiments of the invention will now be described in the following Examples, wherein all parts and percentages are by weight unless otherwise specified. The following materials are used in the examples:
Methyl methacrylate (MMA) , butyl acrylate (BA) , methacrylic acid (MAA) , methyl 3-mercaptopropanoate (MMP) , phosphoethyl methacrylate (PEM) , ammonium persulfate (APS) , propylene glycol (PG) (boiling point: 188.2℃) , glycerol (boiling point: 290.9℃) , 1, 4- Butylene glycol (BD) (boiling point: 228℃) , ethylene glycol (EG) (boiling point: 197.3℃) , and diethylene glycol (DEG) (boiling point: 245℃) are all available from Sinoreagent Group.
Methoxy polyethylene glycol 2000 methacrylate (MPEGMA 2000) is available from BASF.
Phosphoethyl methacrylate (PEM) is available from Solvay.
Diacetone acrylamide (DAAM) is available from Shandong Heda.
BYK-345 wetting agent is available from BYK.
DOWANOL ^TM DPnB glycol ether, available from The Dow Chemical Company, is di(propylene glycol) butyl ether (DOWANOL is a trademark of The Dow Chemical Company) .
DISPONIL FES 32 surfactant is available from BASF.
The following cellulose ethers are available from DuPont Company:
METHOCEL A4M FG methylcellulose has a methoxyl degree of substitution ( “DS (methoxy) ” ) of 1.8.
METHOCEL E15 FG hydroxypropyl methylcellulose (HPMC) and METHOCEL E50 FG HPMC both have a DS (methoxy) of 1.9.
METHOCEL F50 FG HPMC has a DS (methoxy) of 1.8.
METHOCEL K99 FG HPMC has a DS (methoxy) of 1.4.
METHOCEL VLV HPMC has a DS (methoxy) of 1.8.
The following standard analytical equipment and methods are used in the Examples.
Solids content
The solids content of an aqueous composition sample was measured by weighting 0.7±0.1 g of the sample (wet weight of the sample is denoted as “W1” ) , putting the sample into an aluminum pan (weight of aluminum pan is denoted as “W2” ) in an oven at 150℃ for 25 min, and then cooling and weighting the aluminum pan with the dried sample with a total weight denoted as “W3” . “W3-W2” refers to dry or solids weight of the sample. Solids content is calculated by (W3-W2) /W1*100%.
GPC Analysis
GPC analysis was performed generally by Agilent 1200. A sample was dissolved in tetrahydrofuran (THF) /formic acid (FA) (5%) with a concentration of 2 mg/mL and then filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter prior to GPC analysis. The GPC analysis was conducted using the following conditions:
Column: Two Mixed B columns (7.8mm x 300mm) in tandem; column temperature: 35 ℃; mobile phase: THF/FA (5%) ; flow rate: 1.0 mL/minute; Injection volume: 100 μL; detector: Agilent Refractive Index detector, 35℃; and calibration curve: PL Polystyrene Narrow standards (Part No. : 2010-0101) with PS equivalent molecular weights ranging from 2329000 to 162 g/mol.
Tg Measurement
Tg was measured by DSC. A 5-10 milligram (mg) sample was analyzed in a sealed aluminum pan on a TA Instrument DSC Q2000 fitted with an auto-sampler under a nitrogen (N ₂) atmosphere. Tg measurement by DSC was with three cycles including, from -40 to 180℃, 10 ℃/min (1 ^st cycle, then hold for 5 minutes to erase thermal history of the sample) , from 180 to -40℃, 10 ℃/min (2 ^nd cycle) , and from -40 to 180 ℃, 10 ℃/min (3 ^rd cycle) . The measured Tg was obtained from the 3 ^rd cycle by taking the mid-point in the heat flow versus temperature transition as the Tg value.
Particle Size Measurement
The particle size of polymer particles in an aqueous dispersion was measured by using Brookhaven BI-90 Plus Particle Size Analyzer, which employs the technique of photon correlation spectroscopy (light scatter of sample particles) . This method involved diluting 2 drops of an aqueous dispersion to be tested in 20 mL of 0.01 M sodium chloride (NaCl) solution, and further diluting the resultant mixture in a sample cuvette to achieve a desired count rate (K) (e.g., K ranging from 250 to 500 counts/sec for diameter in the range of 10-300 nm) . Then the particle size of the aqueous polymer dispersion was measured and reported as a Z-average diameter by intensity.
Dry film clarity
A coating composition was coated on a glass plate to form a wet film with a thickness of 80 microns using a winding rod and then dried in an oven at 50℃ for 48 hours to form a coated panel. The clarity of the obtained coating film on the panel was measured by using BYK Haze-gard Dual Haze Meter.
Wiping Stain Working Time Test
The test was conducted at room temperature and 45±5%relative humidity. Test aqueous compositions were applied onto glass panels by drawdown with a wet film with a thickness of 80 μm. Immediately thereafter, the wet film was wiped with a finger. The time starting from wiping the wet film with the finger until the wet film becomes sticky and not movable with the finger is recorded as the working time.
Preparation of Oligomer 1 (O1)
DISPONIL Fes 32 surfactant (38.55 grams (g) , 31%active) was dissolved in deionized (DI) water (227 g) with stirring. Then MMA, MAA, PEM, DAAM, and MMP, based on dosages described in Table 1, were slowly added into the resulting surfactant solution to obtain a monomer emulsion.
A solution containing FES 32 surfactant (24.09 g, 31%active) and DI water (1587.70 g) was added into a 4-neck, 5-liter round bottom flask equipped with a thermocouple, a cooling condenser and an agitator, and was heated to 85℃ under a nitrogen atmosphere. An aqueous initiator solution of APS (3.91 g APS in 56.48 g DI water) and 4.0%by weight of the monomer emulsion obtained above were then added into the flask. Within about 5 minutes (min) , initiation of polymerization was confirmed by a temperature increase by 3℃ and a change of the external appearance of the reaction mixture. After heat generation stopped, an aqueous solution of Na ₂CO ₃ (1.66 g in 57.4 g DI water) was charged into the flask. The remaining monomer emulsion was then added gradually to the flask over a period of 40 min with stirring, and at the same time, an aqueous initiator solution of APS (1.64 g APS in 77.82 g DI water) was added gradually to the flask over a period of 50 min. The temperature of the reaction mixture was maintained at 84-86℃. After the monomer emulsion and the initiator solution were consumed, the contents of the flask were further held for 30 min. An aqueous ammonia solution (63.04 g, 25%active) was added into the flask over 15 min and held for 20 min to dissolve or partially dissolve the resulting oligomer O1. Then DI water was added to adjust the solids content of the resultant dispersion. The oligomer O1 had a Tg of 102℃ as measured by DSC.
Preparation of Oligomers 2 (O2)
FES 32 surfactant (5.81 g, 31%active) was dissolved in DI water (207.10 g) with stirring. Then MMA, BA, MAA, PEM, and MMP, based on dosages described in Table 1, were slowly added into the resulting surfactant solution to obtain a monomer emulsion.
A solution containing FES 32 surfactant (5.81 g, 31%active) and DI water (866.20 g) was added into a 4-neck, 3-liter round bottom flask equipped with a thermocouple, a cooling condenser and an agitator, and was heated to 85℃ under a nitrogen atmosphere. An aqueous initiator solution of APS (0.44 g APS in 28.24 g DI water) and 5.0%by weight of the monomer emulsion obtained above were then added into the flask. Within about 5 min, initiation of polymerization was confirmed by a temperature increase by 3℃ and a change of the external appearance of the reaction mixture. After heat generation stopped, the remaining monomer emulsion was added gradually to the flask over a period of 60 min with stirring, and at the same time, an aqueous initiator solution of APS (1.03 g APS in 65.67 g DI water) was added gradually to the flask over a period of 70 min. The temperature of the reaction mixture was maintained at 84-86℃. After the monomer emulsion and the initiator solution were consumed, the contents of the flask were further held for 30 min. An aqueous ammonia solution (62.50 g, 25%active) was added into the flask over 15 min and held for 20 min to dissolve or partially dissolve the resulting oligomer O2. Then DI water was added to adjust the solids content of the resultant dispersion.
Preparation of Oligomers 3 (O3)
The oligomers O3 were prepared according to the same procedure as preparing the oligomer O2 above, except monomers and chain transfer agent (CTA) used for preparing the monomer emulsion are given in Table 1.
Preparation of Oligomer 4 (O4)
FES 32 surfactant (26.02 g, 31%active) was dissolved in DI water (153.11 g) with stirring. Then MMA, MAA, PEM, DAAM, and MMP, based on dosages described in Table 1, were slowly added into the resulting surfactant solution to obtain a monomer emulsion.
A solution containing FES 32 surfactant (16.26 g, 31%active) and DI water (900 g) was added into a 4-neck, 3-liter round bottom flask equipped with a thermocouple, a cooling condenser and an agitator, and then heated to 85℃ under a nitrogen atmosphere. An aqueous initiator solution of APS (2.64 g APS in 56.48 g DI water) and 4.0%by weight of the monomer emulsion obtained above were then added into the flask. Within about 5 min, initiation of polymerization was confirmed by a temperature increase by 3℃ and a change of the external appearance of the reaction mixture. After heat generation stopped, an aqueous solution of Na ₂CO ₃ (1.12 g in 39 g DI water) was charged into the flask. The remaining monomer emulsion was added then gradually to the flask over a period of 40 min with stirring, and at the same time, an aqueous initiator solution of APS (1.70 g APS in 80 g DI water) was added gradually to the flask over a period of 50 min. The temperature of the reaction mixture was maintained at 84-86℃. After the monomer emulsion and the initiator solution were consumed, the contents of the flask were further held for 30 min. An aqueous ammonia solution (20 g, 25%active) was added into the flask over 15 min and held for 20 min to dissolve or partially dissolve the resulting oligomer O4. Then DI water was added to adjust the solids content of the resultant dispersion.
Preparation of Oligomer 5 (O5)
The oligomer O5 were prepared according to the same procedure as preparing the oligomer O4 above, except monomers and CTA used for preparing the monomer emulsion are given in Table 1 and the amount of the aqueous ammonia solution used was 46 g (25%active) .
Properties of the obtained O1-O5 oligomer dispersions are summarized in Table 2.
Table 1. Ingredients (monomers and CTA) used for preparing oligomers
Table 2. Properties of oligomer dispersions
¹Mn and Mw of oligomers were measured by GPC analysis above. ²Mn of oligomers was calculated by the equation described above.
Preparation of cellulose ether solution/mixture
Water and a solvent if used were first mixed evenly. A cellulose ether was slowly added to water (or a mixture of water with a solvent) and stirred until no visible cellulose particles existed at room temperature, indicating complete swelling of the cellulose ether (except A4M cellulose ether) . Ingredients for preparing the cellulose ether solutions/mixtures are given in Table 3. The obtained solutions/mixtures were used for preparing coating compositions.
Table 3. Formulations of cellulose ether solutions/mixtures

Solutions/mixtures	Cellulose ether &dosage	Solvent &dosage	Water
15%E-15 (25.5%PG) solution	E-15 (15 g)	PG (25.5 g)	59.5 g
15%K99 (25.5%PG) solution	K99 (15 g)	PG (25.5 g)	59.5 g
15%VLV (25.5%PG) solution	VLV (15 g)	PG (25.5 g)	59.5 g
15%E-15 (0PG) solution	E-15 (15 g)	None	85 g
10%E-15 (27%PG) solution	E-15 (10 g)	PG (27 g)	63 g
20%E-15 (24%PG) solution	E-15 (20 g)	PG (24 g)	56 g
15%E-15 (25.5%glycerol) solution	E-15 (15 g)	glycerol (25.5 g)	59.5 g
15%E-15 (25.5%BD) solution	E-15 (15 g)	BD (25.5 g)	59.5 g
15%E-15 (25.5%EG) solution	E-15 (15 g)	EG (25.5 g)	59.5 g
15%E-15 (25.5%DEG) solution	E-15 (15 g)	DEG (25.5 g)	59.5 g
13%E-15 (26.1%PG) solution	E-15 (13 g)	PG (26.1 g)	60.9 g
17%E-15 (24.9%PG) solution	E-15 (17 g)	PG (24.9 g)	58.1 g
18%E-15 (24.6%PG) solution	E-15 (18 g)	PG (24.6 g)	57.4 g
15%E-15 (6.8%PG) solution	E-15 (15 g)	PG (6.8 g)	78.2 g
15%E-15 (15.3%PG) solution	E-15 (15 g)	PG (15.3 g)	69.7 g
15%F-50 (25.5%PG) solution	F-50 (15 g)	PG (25.5 g)	59.5 g
15%A4M (25.5%PG) mixture*	A4M (15 g)	PG (25.5 g)	59.5 g

*A4M cellulose ether failed to form a solution.
Coating Composition
The as prepared oligomers, cellulose ether solutions/mixtures, and other raw materials including BYK-345, DPnB, and water were added sequentially and slowly, and then stirred at 800-1,000 revolutions per minute (rpm) for 10-20 min to give the coating compositions of Examples (Exs) 1-14 and Comparative (Comp) Exs 1-10, based on formulations given in Tables 4 and 5, respectively. Properties of these coating compositions were evaluated according to the test methods described above.
As shown in Table 4, aqueous compositions of Exs 1-14 all showed extended working time (34 min or longer) and also provided dry coating films with good clarity of 80%or higher.
In contrast, as shown in Table 5, the aqueous coating compositions of Comp Exs 1-3 and 6-8 all showed shorter working time than the aqueous coating compositions of Exs 1-14. The aqueous coating compositions of Comp Ex 3 also provided dry coating films with low clarity. When the 15%A4M (25.5%PG) mixture was mixed with other components in Comp Ex 4, the resultant mixture became too sticky to make a coating composition suitable for use and property evaluation. When the aqueous coating composition comprising a large amount of the K99 solution (Comp Ex 5) was stored at room temperature overnight, the coating composition gelled and failed to evaluate properties. The aqueous coating composition of Comp Ex 9 comprising glycerol didn’t dry through after dried in an oven at 50℃ for 3 days.
The aqueous coating composition of Comp Ex 10 provided dry coating films with undesirable low clarity.
Table 4. Coating Compositions (Exs 1-14)
¹Cellulose content: by weight based on the total weight of the oligomer and hydroxypropyl methylcellulose.
²Solvent content: by weight based on the total weight of the aqueous coating composition.
Table 5. Comparative Coating Compositions (Comp Exs 1-10)
¹Cellulose content, by weight based on the total weight of the oligomer and hydroxypropyl methylcellulose.
²Solvent content, by weight based on the total weight of the aqueous coating composition.

Claims

An aqueous composition, comprising:

(a) at least 3%, by weight based on the total weight of the aqueous composition, of an oligomer with a number average molecular weight of from 250 to 30,000 g/mol,

wherein the oligomer comprises, by weight based on the weight of the oligomer, from 5%to 20%of structural units of an acid monomer, a salt thereof, or mixtures thereof;

(b) a hydroxypropyl methylcellulose with a degree of substitution of methoxyl groups of 1.5 or higher in an amount of from 45%to 65%, by weight based on the total weight of the oligomer and the hydroxypropyl methylcellulose; and

(c) 2%or more, by weight based on the total weight of the aqueous composition, of a diol containing from 2 to 6 carbon atoms and having a boiling point of from 110 to 280℃.
The aqueous composition of claim 1, wherein the hydroxypropyl methylcellulose has a degree of substitution of methoxyl groups of from 1.8 to 1.9.
The aqueous composition of claim 1, wherein the hydroxypropyl methylcellulose is present in an amount of from 46%to 62%, by weight based on the total weight of the oligomer and the hydroxypropyl methylcellulose.
The aqueous composition of claim 1, wherein the diol is selected from the group consisting of propylene glycol, 1, 4-butylene glycol, ethylene glycol, diethylene glycol, or mixtures thereof.
The aqueous composition of claim 1, wherein the oligomer has a number average molecular weight of from 1,000 to 10,000 g/mol.
The aqueous composition of claim 1, comprising from 3%to 20%of the diol by weight based on the total weight of the aqueous composition.
The aqueous composition of claim 1, wherein the acid monomer is selected from the group consisting of an α, β-ethylenically unsaturated carboxylic acid, a phosphorous-containing acid monomer, or mixtures thereof.
A method of preparing the aqueous composition of any one of claims 1-7, comprising admixing:

(a) at least 3%, by weight based on the total weight of the aqueous composition, of an oligomer with a number average molecular weight of from 250 to 30,000 g/mol,

wherein the oligomer comprises, by weight based on the weight of the oligomer, from 5%to 20%of structural units of an acid monomer, a salt thereof, or mixtures thereof;

(b) a hydroxypropyl methylcellulose with a degree of substitution of methoxyl groups of 1.5 or higher in an amount of from 45%to 65%, by weight based on the total weight of the oligomer and the hydroxypropyl methylcellulose; and

(c) 2%or more, by weight based on the total weight of the aqueous composition, of a diol containing from 2 to 6 carbon atoms and having a boiling point of from 110 to 280℃.