Aqueous dispersion of (meth)acrylic polymer and polysilsesquioxane nanoparticles

Abstract

The aqueous dispersion contains (meth)acrylate polymer particles and substituted silsesquioxane-based particles dispersed in an aqueous carrier, wherein (a) the substituted silsesquioxane-based particles have a volume average size of 5 nanometers or more and less than 500 nanometers, as determined by dynamic light scattering, and (b) the substituted silsesquioxane-based particles are substituted only with one or more moieties selected from the group consisting of alkyl, aryl, hydroxyl, trace amounts of alkoxy, and combinations thereof, and contain 50 mole percent or less of hydroxyl substitution in the form of silanol functional groups, based on moles of the substituted silsesquioxane-based particles, as determined by infrared spectroscopy.

Description

[Technical Field]

[0001] Background of the Invention The present invention relates to an aqueous dispersion of (meth)acrylic polymer particles and polysilsesquioxane nanoparticles, which is useful as a coating material. Summary of the Invention [Problem to be solved by the invention]

[0002] Introduction A common challenge with (meth)acrylic coatings is block resistance. Blocking is adhesion between coatings that are in contact with each other for a period of time. Blocking is generally undesirable in coatings. When two articles come into contact with each other (such as a window and a window frame), it is often desirable for the articles to move freely relative to each other. For example, when the articles are coated with paint, it is desirable for the paint to have block resistance to prevent adhesion between the coated articles.

[0003] The block resistance of (meth)acrylic coatings can be enhanced by the inclusion of micron-sized inert fillers. However, micron-sized fillers tend to affect the appearance of the coating because the fillers scatter visible light, increasing surface roughness and resulting in a matte appearance. In coatings intended for a glossy appearance, it is desirable to avoid matte-inducing fillers.

[0004] Fluorinated surfactants are also known for use in establishing block resistance in coatings, but there is a desire to move away from fluorinated materials.

[0005] It is therefore desirable to identify (meth)acrylic polymer coating compositions that exhibit block resistance without the need for fluorinated surfactants. It is even more desirable to identify such compositions that do not substantially affect the 60 degree gloss of the coating.

[0006] The present invention provides a solution for providing a (meth)acrylic polymer coating that exhibits block resistance without the need for fluorinated surfactants. Surprisingly, the present invention further provides a solution for solving the aforementioned problems by reducing the 60° gloss by no more than 10%, preferably no more than 5%, even more preferably no more than 1%, and even more preferably no reduction, and most preferably increasing the 60° gloss relative to coatings that do not contain silsesquioxane-based particles.

[0007] The present invention functions as a coating formulation in which, when silsesquioxane-based particles having a size of 5 nanometers (nm) or greater, preferably 20 nm or greater and less than 500 nm, preferably 400 nm or less, more preferably 200 nm or less, are dispersed in an aqueous (meth)acrylic dispersion, the resulting dispersion forms a coating that exhibits greater block resistance, generally without a significant decrease in gloss, and in some cases, increased gloss, compared to the same coating without the substituted silsesquioxane-based particles.

[0008] In a first aspect, the present invention provides an aqueous media1. An aqueous dispersion comprising (meth)acrylate polymer particles and substituted silsesquioxane-based particles dispersed therein, wherein: (a) the substituted silsesquioxane-based particles have a volume average size of 5 nanometers or more and less than 500 nanometers, as determined by dynamic light scattering; and (b) the substituted silsesquioxane-based particles are substituted exclusively with one or more moieties selected from the group consisting of alkyl, aryl, hydroxyl, trace amounts of alkoxy, and combinations thereof, and contain 50 mole percent or less of hydroxyl substitution in the form of silanol functional groups, based on moles of substituted silsesquioxane-based particles, as determined by infrared spectroscopy.

[0009] In a second aspect, the invention is a method comprising applying the aqueous dispersion of the first aspect to a surface.

[0010] The aqueous dispersions of the present invention are useful for preparing polyacrylic (i.e., poly(meth)acrylate) coatings with surprisingly reduced blocking, with similar gloss properties, compared to similar polyacrylic coatings that do not contain substituted silsesquioxane-based particles. DETAILED DESCRIPTION OF THE INVENTION

[0011] Test methods, if not accompanied by a test method number and dated, refer to the most recent test method as of the priority date of this document. Test method references include both the testing society reference and the test method number. The following test method abbreviations and identifiers apply herein: ASTM refers to the American Society for Testing and Materials; EN refers to European Norm; DIN refers to the Deutsches Institut fur Normung; ISO refers to the International Organization for Standards.

[0012] Products identified by trade names refer to compositions available from suppliers under those trade names on October 1, 2018.

[0013] "Plurality" means two or more. "And / or" means "and, or alternatively." Unless otherwise stated, all ranges are inclusive of their endpoints.

[0014] The present invention is an aqueous dispersion, which is herein referred to as an aqueous media This means that the aqueous phase is called media The water may be water or a mixture of water and one or more other ingredients. Desirably, the water is aqueous. media It is the continuous phase inside.

[0015] aqueous media An aqueous dispersion comprising (meth)acrylate polymer particles dispersed therein. The "(meth)acrylate" polymer can be an acrylate polymer, a methacrylate polymer, a copolymer comprising acrylate and methacrylate, or a blend of any combination thereof. An acrylate polymer has structural units of acrylate monomers ("acrylate units"). A methacrylate polymer has structural units of methacrylate monomers ("methacrylate units"). A copolymer comprising acrylate and methacrylate contains structural units of both acrylate and methacrylate monomers. The "structural units" of a monomer are what remains of the monomer after polymerization.

[0016] Desirably, the (meth)acrylate polymer contains 30 or more, preferably 50 or more, and most preferably 80 or more weight percent (wt%) of structural units of acrylate and methacrylate monomers. Examples of suitable acrylate and methacrylate monomers include methyl methacrylate, ethyl methacrylate, butyl methacrylate, ureido methacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and 2-propylheptyl acrylate. Preferred combinations of acrylate and methacrylate monomers include methyl methacrylate and one or more monomers selected from the group consisting of ethyl acrylate, butyl acrylate, ureido methacrylate, 2-propylheptyl acrylate, and 2-ethylhexyl acrylate. More preferred combinations of acrylic monomers include methyl methacrylate and butyl acrylate, methyl methacrylate and 2-ethylhexyl acrylate, and methyl methacrylate, butyl acrylate, and ethyl acrylate, with methyl methacrylate and butyl acrylate being most preferred.

[0017] The (meth)acrylate polymer can contain polymer units other than acrylate and methacrylate units—i.e., the (meth)acrylate polymer can be a copolymer of additional monomers other than acrylate and methacrylate monomers. Examples of suitable additional monomers include styrene, acetoacetoxyethyl methacrylate, acrylonitrile, acrylamide, methacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid. The (meth)acrylate polymer preferably contains at least 0.2 wt. %, preferably at least 0.5 wt. %, more preferably at least 1 wt. %, and at the same time at most 5 wt. %, preferably at most 3 wt. %, of structural units of an ethylenically unsaturated carboxylic acid monomer, such as acrylic acid, methacrylic acid, or itaconic acid.

[0018] The aqueous dispersion further comprises an aqueous mediaThe present invention includes substituted silsesquioxane-based particles dispersed in a silsesquioxane polymer. By "silsesquioxane-based" it is meant that the particles contain 50 mole percent (mol%) or more of T units, based on the total of M, D, T, and Q units in the molecule (defined below). Preferably, the silsesquioxane-based particles contain 60 mole% or more, 70 mole% or more, 80 mole% or more, 90 mole% or more of T units, based on the total of M, D, T, and Q units, and can be 100 mole% of T units. By "substituted" it is meant that the silicon is bonded to a pendant group other than hydrogen, and desirably has no hydrogen bonded directly to the silicon. The "pendant" group is a group that is attached to the siloxane (SiO) backbone of the silsesquioxane polymer. n It is a group extending from

[0019] The substituted silsesquioxane-based particles of the present invention are substituted exclusively with one or more groups selected from alkyl, aryl, hydroxyl, minor alkoxy, and combinations thereof. This means that each pendant group is independently selected from the group consisting of alkyl, aryl, hydroxyl, minor alkoxy, and combinations thereof. Preferably, the alkyl group has 1 to 18 carbon atoms, more preferably selected from the group consisting of methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, hexadecyl, and octadecyl. Most preferably, the alkyl group is methyl. Preferably, the aryl group has 6 to 18 carbon atoms and may be substituted with or without halogen atoms. More preferably, the aryl group is selected from the group consisting of phenyl, naphthyl, benzyl, tolyl, xylyl, xenyl, methylphenyl, 2-phenylethyl, 2-phenyl-2-methylethyl, chlorophenyl, bromophenyl, and fluorophenyl. Most preferably, the aryl group is phenyl. Preferably, the substituted silsesquioxane-based particles do not contain acrylate copolymerized in the substituted silsesquioxane-based particles. The substituted silsesquioxane-based particles may contain trace amounts of alkoxy (-OR) substitution residues from the monomers used to prepare the substituted silsesquioxane-based particles. The alkoxy is typically methoxy or ethoxy, more typically methoxy. The amount of "trace" means less than 5 mol%, preferably less than 3 mol%, more preferably 2.5 mol% or less, 2 mol% or less, 1.5 mol% or less, 1.0 mol% or less, or even 0.5 mol% or less. The substituted silsesquioxane-based particles may not have any measurable alkoxy substitution.

[0020] The degree of hydroxyl substitution is limited to 50 mol% or less, based on moles of substituted silsesquioxane-based particles, and can be 40 mol% or less, 30 mol% or less, 20 mol% or less, 10 mol% or less, or can be 0 mol% or less, based on moles of substituted silsesquioxane-based particles. The hydroxyl substitution is in the form of silanol functional groups. Samples of substituted silsesquioxane-based particles were analyzed at 3373 cm -1 The height of the -OH peak at 29 The 3373 cm peak of a standard with the same siloxane unit composition (M, D, T, Q, R composition) of known Si-OH content determined by Si NMR. -1 Determine the mole % hydroxyl substitution by infrared spectroscopy by comparing the -OH peak height with that of the hydroxyl group.

[0021] The substituted silsesquioxane-based particles have the composition of Formula I: M a D b T c Q d (I) During the ceremony, M = R3Si(OR') w O (1-w) / 2 D=R2Si(OR') x O (2-x) / 2 T=RSi(OR') y O (3-y) / 2 Q = Si(OR') z O (4-z) / 2 R is independently at each occurrence selected from the group consisting of alkyl and aryl, preferably from the group consisting of methyl and phenyl. R' at each occurrence is selected from the group consisting of alkyl and hydrogen, preferably from the group consisting of methyl, ethyl and hydrogen. w is a value in the range of 0 to less than 1, x is a value in the range of 0 to less than 2, y is a value in the range of 0 to less than 3, z is a value in the range of 0 to less than 4, and R', w, x, y, and z are such that the hydroxyl concentration resulting from R' being hydrogen is within the concentration limits set forth above, and the alkoxy concentration resulting from R' being alkyl keeps the alkoxy concentration within the "trace" amount range defined above. a = 0 or more and 0.4 or less, b = 0 or more and 0.3 or less, c = a value between 0.5 and 1.0, d = 0 to 0.1, and a+b+c+d=1.0

[0022] The subscripts a, b, c, and d indicate the average mole fractions of M, D, T, and Q units, respectively, in the substituted silsesquioxane-based particles. Determine a, b, c, and d from the molar ratios of the monomer feed amounts used to prepare the substituted silsesquioxane-based particles. If the monomer feed amounts are unknown, 29 Determine a, b, c, and d using Si nuclear magnetic resonance spectroscopy.

[0023] The subscript "a" can be 0. The subscript "d" can be 0. Desirably, the subscripts "a" and "d" are 0, so that the substituted silsesquioxane-based particle has the composition of Formula II: D b T c (II) In the formula, "b" is equal to or greater than 0 and less than 0.3, and "c" is equal to or greater than 0.7 and less than 1.0.

[0024] The subscripts a, c, and d can all be 0, and b can be 1.0, corresponding to substituted silsesquioxane-based particles composed only of "T" units.

[0025] The substituted silsesquioxane-based particles can be of any shape. The substituted silsesquioxane-based particles are generally spherical. The substituted silsesquioxane-based particles have a volume average size of 5 nanometers (nm) or more, and can be 10 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, or even 100 nm or more; and at the same time, the substituted silsesquioxane-based particles have a volume average size of less than 500 nm, and can be 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less, 200 nm or less, 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, or even 100 nm or less. The volume average size of the substituted silsesquioxane-based particles is determined using dynamic light scattering. To determine particle size using dynamic light scattering, prepare a 1-5 weight percent solution of sample particles and add the solution to a polytetrafluoroethylene cell. Collect data using a 30-second run time on a Microtrac Nanotrac Waver particle sizer. Collect data until three components are obtained. Use the analytical method for transparent, spherical particles with a refractive index of 1.42. The resulting particle size is the volume-average particle size.

[0026] The aqueous dispersion of the present invention desirably contains 0.20 wt. % or more, preferably 0.25 wt. % or more, 0.30 wt. % or more, 0.40 wt. % or more, or 0.50 wt. % or more, based on the weight of the aqueous dispersion, of substituted silsesquioxane-based particles, while generally 25 wt. % or less, typically 20 wt. % or less, 15 wt. % or less, 10 wt. % or less, 5 wt. % or less, 4 wt. % or less, even 3 wt. % or less, 2 wt. % or less, or 1.5 wt. % or less, and may be 1 wt. % or less, 0.90 wt. % or less, 0.80 wt. % or less, or even 0.70 wt. % or less.

[0027] The aqueous dispersion of the present invention desirably contains 10% by weight or more of (meth)acrylate polymer particles, and can contain 20% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, or even 60% by weight or more of (meth)acrylate polymer particles, based on the weight of the aqueous dispersion, and at the same time, typically contains 80% by weight or less, preferably 75% by weight or less of (meth)acrylate polymer particles, based on the weight of the aqueous dispersion.

[0028] The aqueous dispersion may include one or more additional components other than the acrylate polymer particles and the substituted silsesquioxane-based particles. media Examples of suitable additional ingredients include any one or any combination of two or more of the following: surfactants and dispersants (nonionic, anionic, cationic, or any combination thereof), pigments and fillers (such as titanium dioxide and clay), rheology modifiers, stabilizers (such as polyvinylpyrrolidone), coalescent aids (such as 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, ester alcohols, glycol ethers, and the like), and antifoaming agents (such as polysiloxanes and hydrophobic solids in polyglycols).

[0029] The aqueous dispersions of the present invention are useful for preparing polyacrylic coatings that have surprisingly low blocking while maintaining gloss properties similar to comparable polyacrylic coatings that do not contain substituted silsesquioxane-based particles.

[0030] Polyacrylate coatings are prepared from the aqueous dispersions of the present invention by applying the aqueous dispersion to a surface. The aqueous dispersion is applied by any method suitable for acrylic dispersions, including brushing, spraying, and wiping. Once the dispersion is applied to a surface, the aqueous mediaThe water in the coating evaporates, drawing the (meth)acrylate polymer particles together and promoting their coalescence into an acrylic film. At least a portion of the substituted silsesquioxane-based particles migrate to the surface of the coating as the water evaporates, providing substituted silsesquioxane-based particles on the surface of the resulting acrylic polymer coating, which is believed to enhance the blocking resistance of the acrylic polymer coating. It has been discovered that the substituted silsesquioxane-based particles tend to aggregate into clusters scattered throughout the surface of the acrylic polymer coating, which is believed to enhance the blocking resistance of the resulting acrylic polymer coating. [Example]

[0031] The following examples are illustrative of the present invention and are not necessarily meant to define the full scope of the invention.

[0032] The characterization of the examples and comparative examples herein includes gloss evaluation and block resistance evaluation, and the following procedures are used for the characterization.

[0033] Gloss. Prepare samples for gloss evaluation by drawing down a 3 mil thick wet film onto a Leneta chart (WB plain white) and aging for 24 hours at 23°C and 50% relative humidity. Measure gloss in a manner similar to ASTM D-523-89 using a BYK Gardner Micro TRI Glossmeter. Determine gloss values ​​at angles of 20 degrees (20°) and 60 degrees (60°).

[0034] Block Resistance. Prepare specimens for block resistance evaluation by drawing down 10 mil thick wet films onto cold-rolled steel or aluminum Q-panels and aging the films at 23°C and 50% relative humidity for 24 hours before characterization. Characterize block resistance according to the ASTM D4946-89 Peel Block Resistance Test. For each coating, cut eight 3.8 cm x 3.8 cm squares from the 24-hour aged film samples.

[0035] For the room temperature (RT) test, two square specimens are stacked face-to-face at room temperature so that the coatings are in contact with each other. A No. 8 rubber stopper is placed on top of the stack of two square specimens, and a 1-kilogram weight is then placed on top of the stopper. After 30 minutes at room temperature, the weight and stopper are removed, and the stack of specimens is peeled apart with slow, steady force to evaluate the room temperature block resistance. The results are evaluated according to the ratings in Table 1.

[0036] For the hot block test, a square specimen is placed on a flat metal plate, along with a No. 8 rubber stopper and a 1-kilogram weight, in a 50°C oven and allowed to equilibrate to a temperature of 50°C. Once equilibrated, two square specimens are stacked face-to-face in the oven, with the coatings in contact with each other. A temperature-equilibrated stopper is placed on top of the stack of square specimens, and then a temperature-equilibrated 1-kilogram weight is placed on top of the stopper, and the whole is placed in a 50°C oven for 30 minutes. The specimens are then removed from the oven, and the stack is peeled apart with a slow, steady force to assess hot block resistance. Results are evaluated according to the ratings in Table 1. [Table 1]

[0037] Substituted silsesquioxane-based particle synthesis Table 2 shows the ingredients used to prepare each of the substituted silsesquioxane-based particles P1-P8, as well as particle characterization. The values ​​indicate grams (g) of the ingredients used to prepare each substituted silsesquioxane-based particle. The particle characterization is as described previously in this specification.

[0038] Prepare the example substituted silsesquioxane-based particles by combining water, ammonium hydroxide (as a 29 wt% solution), surfactant, and stabilizer components, if used, in a glass bottle. While stirring with a polytetrafluoroethylene magnetic stir bar, add the monomer components at the addition rate (milliliters / minute) listed in Table 2 (if two or more monomer components are present, add them simultaneously). Continue stirring for one hour after monomer addition is complete. The result is an aqueous dispersion of substituted silsesquioxane-based particles. [Table 2]

[0039] TERGITOL and DOWFAX are trademarks of The Dow Chemical Company.

[0040] (Meth)acrylate aqueous dispersion Each example includes one of four (meth)acrylate aqueous dispersions: Dispersion A, Dispersion B, Dispersion C, or Dispersion D. Each of the four (meth)acrylate aqueous dispersions is formulated as a paint formulation in which (meth)acrylate polymer particles are present as a binder. The formulation for each of the (meth)acrylate aqueous dispersions is shown below. The components listed in the recipe are mixed to prepare a dispersion, and a paint formulation is formed in a manner common in the paint industry. [Table 3]

[0041] KRONOS is a trademark of Kronos International, Inc. TAMOL is a trademark of Rohm and Haas Company. BYK is a trademark of BYK-Chemi GmbH Corporation. TEXANOL and OPTIFILM are trademarks of Eastman Chemical Corporation. ACRYSOL is a trademark of The Dow Chemical Company. CAPSTONE is a trademark of Chemours Company FC.

[0042] Synthesis of binder A A first monomer emulsion is formed by combining 130 g of deionized water, 28.9 g of DISPONIL™ FES993 surfactant (30 wt% active fatty alcohol polyglycol ether sulfate, sodium salt), 96.9 g of butyl acrylate, 411.06 g of methyl methacrylate, 2.27 g of sodium 4-vinylbenzenesulfonate (90 wt% active), and 1.28 g of n-dodecyl mercaptan. DISPONIL is a trademark of Cognis IP Management GmbH.

[0043] Separately from the first monomer emulsion, combine water (300 g), DISPONIL™ FES993 surfactant (47.6 g, 30 wt% active), butyl acrylate (357 g), ethyl acrylate (357 g), methyl methacrylate (299.2 g), acetoacetoxyethyl methacrylate (143.16 g, 95 wt% active), phosphoethyl methacrylate (30.6 g, 60 wt% active), sodium 4-vinylbenzenesulfonate (11.33 g, 90 wt% active), and n-dodecyl mercaptone (5.95 g) to form a second monomer emulsion.

[0044] A 5-liter, four-necked, round-bottom flask equipped with a paddle stirrer, thermometer, nitrogen inlet, and reflux condenser is charged with deionized water (1100 g) and DISPONIL™ FES 933 surfactant (28.33 g, 30 wt. % active). The contents of the flask are heated to 85°C under nitrogen. While stirring, 105 g of the first monomer emulsion is added, followed immediately by an aqueous solution of ammonium persulfate (5.1 g) dissolved in deionized water (25 g), followed by a rinse with deionized water (5 g). Stir for 10 minutes, then over 35 minutes, sequentially add the remainder of the first monomer emulsion, followed by a solution containing ammonium persulfate (0.52 g) dissolved in deionized water (25 g). The contents, holding the first monomer emulsion, are rinsed with 25 g of deionized water and added to the flask. The temperature is maintained at 85°C with mixing for 15 minutes. Over 80 minutes, the second monomer emulsion is added sequentially, followed by a solution containing ammonium persulfate (1.18 g) dissolved in deionized water (55 g). The container holding the second monomer emulsion is rinsed with 25 g of deionized water and added to the flask. The mixture is held at 85°C for 10 minutes. A solution containing ammonium hydroxide (10 g, 29 wt% active) and deionized water (10 g) is added over 5 minutes. The flask is cooled to 70°C, and a catalyst / activator pair (such as tert-butyl hydroperoxide / isoascorbic acid) is added to the flask to reduce residual monomer. Binder A is obtained by neutralizing to a pH of 9.5 with a dilute solution of ammonium hydroxide. Binder A has a solids content of 45.3 wt%. The (meth)acrylate polymer particles of Binder A have a volume average particle size of 85 nm.

[0045] Dispersion B Dispersion B is the same as Dispersion A except that the CAPTSTONE FS-63 water-soluble anionic fluorosurfactant is absent and the amount of water is 35.22 g. [Table 4]

[0046] TIONA is a trademark of Cristal Pigment UK Limited. RHOPLEX is a trademark of Rohm and Haas Company. [Table 5]

[0047] T M Examples using particles (P1 to P3) Substituted silsesquioxane-based particles P1 to P3 contain only T units. As shown in Table 2, the T units are primarily substituted with methyl groups, with only a small amount of hydroxyl substitution. The mean volume particle sizes range from 22 nm for P1 to 118 nm for P3.

[0048] Examples are prepared by combining a substituted silsesquioxane-based particle dispersion with a (meth)acrylate dispersion and adding additional water as shown in Table 3. The additional water is to achieve the same volume of solids for each example. Examples 1-6 are prepared by combining substituted silsesquioxane-based particles P1 or P3 with (meth)acrylate dispersion B. Examples 7-10 are prepared by combining substituted silsesquioxane-based particles P1 or P2 with (meth)acrylate dispersion C. Examples 11-14 are prepared by combining substituted silsesquioxane-based particles P1 or P2 with (meth)acrylate dispersion D.

[0049] The examples are characterized according to the gloss and block resistance methods described above. For reference, Comparative Example A is simply Dispersion B, which does not contain any substituted silsesquioxane-based particles. Comparative Example B is Dispersion C, which does not contain any substituted silsesquioxane-based particles. Comparative Example C is Dispersion D, which does not contain any substituted silsesquioxane-based particles. The results of the characterization are shown in Table 4. [Table 6] [Table 7]

[0050] The results in Table 4 show that the inclusion of substituted silsesquioxane-based particles in the (meth)acrylate dispersions at least improved hot block, which is the most stringent of the block resistance evaluations. In most cases, there was comparable or even improved (higher) gloss values ​​when substituted silsesquioxane-based particles were included.

[0051] T Ph Examples using contained particles (P4 to P7) Substituted silsesquioxane-based particles P4–P7 contain only T units. As shown in Table 2, the T units are substituted with phenyl groups (P4) or a combination of phenyl and methyl groups (P5–P7), and contain only small amounts of hydroxyl substitution. Average volume particle sizes range from 9 nm for P4 to 51 nm for P6.

[0052] Examples are prepared by combining a substituted silsesquioxane-based particle dispersion with a (meth)acrylate dispersion and adding additional water, as shown in Table 5. The additional water is used to achieve the same level of solids in each example. Substituted silsesquioxane-based particles selected from P4 to P7 are combined with (meth)acrylate Dispersion A to prepare Examples 17 to 22. The examples are characterized according to the gloss and block resistance methods described above. For reference, Comparative Example D is simply (meth)acrylate Dispersion A without any substituted silsesquioxane-based particles. The characterization results are shown in Table 6. [Table 8] [Table 9]

[0053] The results in Table 6 show that the inclusion of substituted silsesquioxane-based particles in the (meth)acrylate dispersion improved at least one of the block resistance ratings. In most cases, there was a comparable or even improved (higher) gloss value when the substituted silsesquioxane-based particles were included.

[0054] Example using mixed siloxane particles (P8) As shown in Table 2, the substituted silsesquioxane-based particle P8 contains only T and D units, each of which is substituted primarily with methyl groups, with only a small amount of hydroxyl substitution. The mean volume particle size of P8 is 123 nm.

[0055] 20 grams of (meth)acrylate Dispersion A is combined with 0.65 grams of P8 and 0.82 grams of water to prepare Example 23. 20 grams of (meth)acrylate Dispersion B is combined with 1.32 grams of P8 and 0.15 grams of water to prepare Example 24. In each case, water is used to achieve the same level of solids in each example.

[0056] The examples were characterized according to the gloss and block resistance methods described above. For reference, Comparative Example D is simply (meth)acrylate Dispersion A without any substituted silsesquioxane-based particles. Example 23 has a 20° gloss of 52.2, a 60° gloss of 74.4, a room temperature block resistance of 7, and a hot block resistance of 6. Example 24 has a 20° gloss of 52.4, a 60° gloss of 74.5, a room temperature block resistance of 6.5, and a hot block resistance of 5.5.

[0057] The results of Examples 23 and 24 show that the inclusion of substituted silsesquioxane-based particles in the (meth)acrylate dispersion improved both block resistance ratings, with comparable or even improved (higher) gloss values ​​when substituted silsesquioxane-based particles were included.

Claims

1. 1. An aqueous dispersion comprising (meth)acrylate polymer particles and substituted silsesquioxane-based particles dispersed in an aqueous medium, (a) the substituted silsesquioxane-based particles have a volume average size, as determined by dynamic light scattering, of 5 nanometers or more and 150 nanometers or less; (b) the substituted silsesquioxane-based particles are substituted only with one or more moieties selected from the group consisting of alkyl, aryl, hydroxyl, trace amounts of alkoxy, and combinations thereof, and contain 50 mole percent or less of hydroxyl substitution in the form of silanol functional groups, based on moles of the substituted silsesquioxane-based particles, as determined by infrared spectroscopy; the (meth)acrylate polymer is an acrylate polymer, a methacrylate polymer, a copolymer comprising an acrylate and a methacrylate, or a blend of any combination thereof; When the (meth)acrylate polymer is a copolymer of additional monomers other than acrylate and methacrylate monomers, the additional monomers are selected from styrene, acrylonitrile, acrylamide, methacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid; the concentration of the (meth)acrylate polymer particles is 20 weight percent or more and 80 weight percent or less based on the weight of the aqueous dispersion; An aqueous dispersion in which the concentration of the substituted silsesquioxane-based particles is 0.20 weight percent or more and 10 weight percent or less based on the weight of the aqueous dispersion (however, this does not include aqueous resin compositions containing a fatty acid-modified acrylic resin aqueous dispersion and a silicone resin aqueous dispersion, in which the fatty acid-modified acrylic resin is an acrylic resin modified with a drying oil-modified fatty acid, a semi-drying oil-modified fatty acid, or a non-drying oil-modified fatty acid).

2. 2. The aqueous dispersion of claim 1, wherein the alkyl group is a methyl group.

3. The aqueous dispersion of any one of claims 1 to 2, wherein the substituted silsesquioxane-based particles do not contain a (meth)acrylate copolymerized therein.

4. 4. The aqueous dispersion of claim 1, wherein the concentration of the substituted silsesquioxane-based particles is greater than or equal to 0.20 weight percent and less than or equal to 5 weight percent based on the weight of the aqueous dispersion.

5. The substituted silsesquioxane-based particles have a composition according to Formula I: M ａ D ｂ T ｃ Q ｄ (I) In the formula, M is R ３ Si(OR') ｗ O （１－ｗ）／２ and D is R ２ Si(OR') ｘ O （２－ｘ）／２ and T is RSi(OR') ｙ O （３－ｙ）／２ and Q is Si(OR') ｚ O （４－ｚ）／２ 5. The aqueous dispersion of claim 1, wherein R, at each occurrence, is independently selected from the group consisting of alkyl and aryl; R', at each occurrence, is selected from the group consisting of alkyl and hydrogen; "w" has a value ranging from 0 to less than 1; "x" has a value ranging from 0 to less than 2; "y" has a value ranging from 0 to less than 3; and "z" has a value ranging from 0 to less than 4; R', "w," "x," "y," and "z" are selected such that the concentration of hydroxyl resulting from R' being hydrogen is 50 mole percent or less, and the concentration of alkoxy resulting from R' being alkyl is at most a trace amount of alkoxy, as determined by infrared spectroscopy; "a" has a value equal to or greater than 0.4, "b" has a value equal to or greater than 0.3, "c" has a value equal to or greater than 0.5, and "d" has a value equal to or greater than 0.1; and the sum of "a," "b," "c," and "d" is 1.

0.

6. 6. The aqueous dispersion of claim 5, wherein "a" and "d" are 0.

7. 7. The aqueous dispersion of claim 5 or claim 6, wherein R at each occurrence is independently selected from the group consisting of methyl, phenyl, and hydroxyl, with the proviso that hydroxyl is present in 50 mole percent or less based on moles of substituted silsesquioxane-based particles as determined by infrared spectroscopy.

8. The aqueous dispersion of any one of claims 1 to 7, wherein the aqueous dispersion is free of fluorinated surfactants.

9. A coating method comprising the step of applying the aqueous dispersion according to any one of claims 1 to 8 to a surface of an article.

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