Liquid-applied sound damping article

Abstract

The present invention relates to a composition comprising an aqueous dispersion of a) binder-coated opacifying polymer particles; b) extender particles; c) starch; d) a blowing agent; and e) a rheology modifier. The composition of the present invention is useful as a coating in liquid-applied sound damping applications.

Description

[0001] Liquid- Applied Sound Damping Article

[0002] Background of the Invention

[0003] The present invention relates to an article suitable for liquid- applied sound damping (LASD).

[0004] LASD coatings are widely used in automotive markets to reduce vibration in rigid structures. The LASD market is dominated by waterborne coatings, which are typically composed of a dispersion of viscoelastic polymer, mineral fillers, processing additives, and baking additives. These coatings are usually applied as a 1- to 5-mm layer on sheet metal then dried at high temperatures. The dried coatings dissipate resonant vibrations within the substrate and reduce the overall noise level in application.

[0005] Automotive manufacturers are continuing to seek materials that further reduce vibration, thereby improving damping performance. While LASD coatings are higher performing than some damping solutions like bitumen pads, there is still a need for even better damping solutions that can be easily applied on the manufacturing line.

[0006] Summary of the Invention

[0007] The present invention addresses a need in the art by providing an article comprising a coating superposing a metal substrate, wherein the coating comprises an aqueous dispersion of a) binder-coated opacifying polymer particles; b) extender particles; c) starch; d) a blowing agent; and e) a rheology modifier; wherein the binder-coated opacifying polymer particles comprise: i) a water-occluded core comprising from 20 to 60 weight percent structural units of a salt of a carboxylic acid monomer and from 40 to 80 weight percent structural units of a nonionic monoethylenically unsaturated monomer; ii) a polymeric shell having a Tgin the range of from 60 °C and 120 °C; and iii) a polymeric binder layer superposing the shell, which polymeric binder layer has a Tgof not greater than 50 °C and comprises structural units of at least one monoethylenically unsaturated monomer; wherein the weight-to-weight ratio of structural units of monomers in the water-occluded core to the shell 1: 10 to 1:20; the weight-to- weight ratio of the polymeric binder layer to the sum of the shell and the structural units of monomers in the core is in the range of from 1: 1 to 3.5: 1 ; wherein the z-average particle size of the polymer particles is in the range of from 300 nm to 750 nm; and wherein the coating has a Brookfield viscosity in the range of from 200,000 cP to 20,000,000 cP; and wherein coating has wet areal density in the range of from 0.35 kg / m2to 10 kg / m2.

[0008] The article of the present invention is useful in liquid applied sound damping applications.

[0009] Detailed Description of the Invention

[0010] The present invention is an article comprising a coating superposing a metal substrate, wherein the coating comprises an aqueous dispersion of a) binder-coated opacifying polymer particles; b) extender particles; c) starch; d) a blowing agent; and e) a rheology modifier; wherein the binder-coated opacifying polymer particles comprise: i) a water-occluded core comprising from 20 to 60 weight percent structural units of a salt of a carboxylic acid monomer and from 40 to 80 weight percent structural units of a nonionic monoethylenically unsaturated monomer; ii) a polymeric shell having a Tgin the range of from 60 °C and 120 °C; and iii) a polymeric binder layer superposing the shell, which polymeric binder layer has a Tgof not greater than 50 °C and comprises structural units of at least one monoethylenically unsaturated monomer; wherein the weight-to-weight ratio of structural units of monomers in the water-occluded core to the shell 1: 10 to 1:20; the weight-to-weight ratio of the polymeric binder layer to the sum of the shell and the structural units of monomers in the core is in the range of from 1 : 1 to 3.5: 1 ; wherein the z-average particle size of the polymer particles is in the range of from 300 nm to 750 nm; and wherein the coating has a Brookfield viscosity in the range of from 200,000 cP to 20,000,000 cP; and wherein coating has wet areal density in the range of from 0.35 kg / m2to 10 kg / m2. The binder-coated opacifying pigment polymer particles comprises a water-occluded core, a shell superposing the core, and a binder superposing the shell. The water-occluded core comprises from 20, preferably from 25, more preferably from 30, and most preferably from 32 weight percent, to 60, preferably to 50, more preferably to 40, and most preferably to 36 weight percent structural units of a salt of a carboxylic acid monomer based on the weight of structural units of monomers in the core.

[0011] As used herein, the term “structural units” refers to the remnant of the recited monomer after polymerization. For example, a structural unit of a salt of methacrylic acid, where M+is a counterion, preferably a lithium, sodium, or potassium counterion, is as illustrated: structural unit of a salt of methacrylic acid

[0012] Examples of suitable carboxylic acid monomers include acrylic acid, methacrylic acid, itaconic acid, and maleic acid.

[0013] The water-occluded core further comprises from 40, preferably from 50, more preferably from 55, more preferably from 60, and most preferably from 64 weight percent to 80, preferably to 75, more preferably to 70, and most preferably to 68 weight percent structural units of a nonionic monoethylenically unsaturated monomer based on the weight of structural units of monomers in the core. Examples of nonionic monoethylenically unsaturated monomers include one or more acrylates and / or methacrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, / -butyl acrylate 2-ethylhexyl acrylate, methyl methacrylate, n-butyl methacrylate, / -butyl methacrylate, isobutyl methacrylate, isobomyl methacrylate, lauryl methacrylate, and cyclohexyl methacry late; and one or more monoethylenically unsaturated aromatic compounds such as styrene, a-methylstyrene, and 4- / -butylslyrene. A preferred nonionic monoethylenically unsaturated monomer is methyl methacrylate.

[0014] The polymeric shell preferably has a Tgin the range of not less than 80 °C, more preferably not less than 90 °C, and most preferably not less than 95 °C, and preferably not greater than 115 °C, and most preferably not greater than 110 °C. As used herein, Tgrefers to the glass transition temperature as calculated by the Fox equation. Preferably, the shell comprises structural units of methyl methacrylate, styrene, a-methylstyrene, isobomyl methacrylate, lauryl methacrylate, acrylonitrile, or cyclohexyl methacrylate. In one embodiment, the shell comprises at least 70 weight percent structural units of styrene.

[0015] The polymeric shell may also further comprise from 0.2 to 5 weight percent structural units of other multiethylenically unsaturated monomers such as allyl methacrylate (ALMA), divinyl benzene (DVB), trimethylolpropane trimethacrylate (TMPTMA), or trimethylolpropane triacrylate (TMPTA).

[0016] As used herein, “polymeric binder” refers to a polymeric material that is film forming on a desired substrate, with or without a coalescent. The Tgof the polymeric binder as calculated by the Fox equation is not greater than 50 °C, or not greater than 35 °C; and not less than -20 °C, or not less than -10 °C. Examples of suitable polymeric binders include acrylic, styrene- acrylic, vinyl esters such as vinyl acetate and vinyl versatates, and vinyl ester-ethylene polymeric binders. Acrylic binders comprising structural units of methyl methacrylate and structural units of one or more acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, or 2-ethylhexyl acrylate, are especially preferred, as are styrene-acrylic binders.

[0017] Preferably, the weight-to-weight ratio of structural units of monomers of the core to the shell of the polymer particles is in the range of 1 : 12 to 1: 16. Preferably, the weight-to-weight ratio of the polymeric binder to the sum of the structural units of monomers of the core and the shell of the polymer particles is in the range of from 1.2: 1, more preferably from 1.5:1, and most preferably from 1.8:1, to preferably 3.0:1, more preferably to 2.5:1, and most preferably to 2.2:1.

[0018] The z-average particle size of the polymer particles is in the range of from 300 nm or from 400 nm or 450 nm or from 475 nm, to 700 nm or to 600 nm or to 550 nm. As used herein, z-average particle size refers to particle size as determined by dynamic light scattering, for example using a BL90 Plus Particle Size Analyzer (Brookhaven). The binder-coated polymer particles can be prepared as described in US 7,691,942 B2 and in the example section hereinbelow.

[0019] The composition further comprises extender particles, which typically have a median diameter average (D50) particle size in the range of from 1 m to 50 pm. Examples of suitable extender particles, also referred to in the art as fillers, include calcium carbonate; silica; alumina; kaolin; clay; talc; graphite; mica; diatomaceous earth; glass powder, fibers, or microspheres; aluminum hydroxide; perlite; barium sulfate; magnesium carbonate; calcium dihydrate; rock wool; Wollastonite; zeolite; ceramic and thermoplastic microspheres; polymeric fibers, and crosslinked rubber particles. A combination of calcium carbonate and mica are preferred extender particles. The weight-to-weight ratio of the extender particles to the binder-coated opacifying polymer particles is preferably in the range of from 20:80 to 80:20. Preferably, the extender particles and the binder-coated opacifying pigment particle compose at least 90 or at least 95 weight percent of the components in the composition, excluding water.

[0020] The composition further includes a starch, which is typically potato starch or corn starch, a blowing agent that expands upon heating such as the commercially available Expancel 031 WUF 40 Microspheres, and a rheology modifier such as alkali swellable emulsions. Defoamers, dispersants, and surfactants are advantageously used to prepare the composition of the present invention, and it may also be desirable to include a colorant. The composition has a Brookfield viscosity in the range of from 200,000 cP or from 500,000 cP, to 20,000,000 cP or to 10,000,000 cP. As used herein “Brookfield viscosity” refers to Brookfield viscosity when not under shear conditions. The method for measuring Brookfield viscosity is described below.

[0021] The composition can be applied to a metal substrate at an areal density (i.e., wet areal density) in the range of 0.35 kg / m2or from 1 kg / m2, to 10 kg / m2, then baked at a temperature in the range of from 100 °C to 200 °C to dry and cure the composition. The areal density of the cured coating (i.e., dry areal density) is in the range of from 0.3 kg / m2or from 0.5 kg / m2to 5 kg / m2. The wet areal density refers to the mass of the uncured coated sample minus the mass of the substrate divided by the area of the metal substrate; similarly, the dry areal density of the sample is the mass of the dry substrate minus the mass of uncoated substrate divided by the area of the of the metal substrate. Examples of suitable metals include steel, stainless steel, iron, aluminum, magnesium, and titanium. It has been surprisingly discovered that binder-coated opacifying polymer particles give improved damping as compared with cured LASD formulations that contain binder and opacifying polymer particles as distinct components.

[0022] Examples

[0023] In the following Intermediate Examples, MMA refers to methyl methacrylate: MAA refers to methacry lic acid; AA refers to acrylic acid; BA refers to zr-butyl acrylate; PEM refers to 2-phosphoethyl methacrylate; CHMA refers to cyclohexyl methacrylate; LOFA refers to linseed oil fatty acid; AN refers to acrylonitrile; ALMA refers to allyl methacrylate; DVB refers to divinyl benzene; NaPS refers to sodium persulfate; f-BHP refers to / -butylhydroperoxide: IAA refers to isoascorbic acid; EDTA refers to the tetrasodium salt of ethylene diamine tetraacetic acid; DMEA refers to dimethylethanol amine; and Core #1 refers to an aqueous dispersion of polymer particles (66 MMA / 34 MAA, solids 32.0%, z-average particle size of 135 nm) prepared substantially as described in US 6,020,435.

[0024] Intermediate Example 1 - Preparation of OAP 1

[0025] A 5-L, four-necked round bottom flask was equipped a paddle stirrer, thermometer, N2 inlet and reflux condenser. DI water (500 g) was added to the vessel and heated to 89 °C under N2. NaPS (1.90 g in 20 g water) was added to the vessel immediately followed by Core #1 (125 g). Monomer emulsion 1 (ME 1), which was prepared by mixing DI water (125.0 g), Disponil FES-32 emulsifier (10.0 g), styrene (436.8 g), linseed oil fatty acid (2.8 g), AN (112.0 g), and DVB (7.0 g), was then added to the kettle over 85 minutes. The temperature of the reaction was controlled at 78 °C at the start of ME 1 feed, was allowed to increase to 84 °C after 40 minutes and allowed to increase to 92 °C after 55 minutes. Two minutes after the start of ME 1 addition, a solution of AA (5.6 g) in DI water (35 g) was added to the flask. Forty minutes after the start of ME 1 addition, a solution of NaPS (0.5 g in 30 g water) was added to the kettle over 45 minutes. Upon completion of the ME 1 feed, the reaction was cooled to 72 °C.

[0026] When the kettle temperature reached 80 °C, an aqueous mixture of ferrous sulfate and EDTA (20 g, 0.1 wt. % FeSCU, and 2 g, 1 wt. % EDTA) was added to the kettle. When the kettle temperature reached 72 °C, co-feeds including a solution of (1.9 g) and NaPS (5.0 g) mixed with DI water (100 g), along with a separate solution of IAA (2.6 g in 100 g water) were both added simultaneously to the kettle at a rate of 1.2 g / min. Two minutes after the start of charging the co-feed solutions, ME 2, which was prepared by mixing DI water (260 g), Disponil FES-32 emulsifier (17.0 g), BA (543.6 g), MMA (409.2 g), and PEM (67.2 g, 60% active), was added to the kettle over 55 minutes while allowing the temperature to rise to 80 °C without providing any additional external heat. Thirty minutes after the start of ME 2, 13.8 g of 1 -dodecanethiol was added to ME 2 with adequate mixing. Upon completion of ME 2 additions, the co-feed solutions were stopped and the batch was held for 5 minutes at 80 °C. A solution of NH4OH (5 g, 28 wt. % aq.) mixed with DI water (5.0 g) was then added to the kettle along with hot (90 °C) DI water (225 g).

[0027] ME 3, which was prepared by mixing DI water (54.0 g), Disponil FES-32 emulsifier (3.0 g), BA (104.4 g), MMA (75.6 g), and 4-hydroxy TEMPO (3.0 g), was fed to the kettle over 5 minutes. Immediately after the ME 3 feed addition was complete, NH4OH (83.3 g, 28 wt. % aq.) mixed with DI water (35 g) was added to the kettle over 3 min. When NH4OH addition was complete, the batch was held for 5 minutes. The addition the co-feed solutions was resumed at a rate of 1.2 g / min until completion. Additional co-feeds including a solution of t-BHP (1.5 g) in DI water (25 g), along with a separate solution of IAA (0.7 g) in water (25 g) were both added simultaneously to the kettle at a rate of 1.2 g / min. Upon completion of addition of the second co-feed the dispersion was cooled to 25 °C. When the kettle temperature reached 45°C a solution of ACRYSOL™ ASE-60 Thickener (A Trademark of The Dow Chemical Company or its Affiliates, 13.35 g in 53 g water) was added to the kettle over 10 minutes. The dispersion was filtered to remove any coagulum. The filtered opaque acrylic polymer dispersion (GAP) had a solids content of 48.1%.

[0028] Intermediate Example 2 - Preparation of GAP 2

[0029] The preparation of Intermediate Example 2 was prepared substantially as described for the preparation of Intermediate Example 1 except that ALMA (5.6 g) was used instead of DVB in the preparation of MEI. The filtered opaque acrylic polymer dispersion (GAP) had a solids content of 48.7%.

[0030] Intermediate Example 3 - Preparation of GAP 3

[0031] A 5-liter, four-necked round bottom flask was equipped a paddle stirrer, thermometer, N2 inlet and reflux condenser. DI water (500 g) was added to the kettle and heated to 89 °C under N2. NaPS (1.90 g in 20 g water) was added to vessel immediately followed by Core #1 (125 g). Monomer emulsion 1 (ME 1), which was prepared by mixing DI water (125.0 g), Disponil FES-32 emulsifier (10.0 g), styrene (380.8 g), LOFA (2.8 g), AN (1 12.0 g), CHMA (56.0 g), and DVB (7.0 g), was then added to the kettle over 85 min. The temperature of the reaction was controlled at 78°C at the start of ME 1 feed, was allowed to increase to 84 °C after 40 minutes, then allowed to increase to 92 °C after 55 minutes. Two minutes after the start of ME 1 addition, a solution of AA (5.6 g) in DI water (35 g) was added to the flask. Forty minutes after the start of ME 1 addition, a solution of NaPS (0.5 g in 30 g water) was added to the kettle over 45 minutes. Upon completion of the ME 1 feed, the reaction was cooled to 72 °C.

[0032] When the kettle temperature reached 80 °C, an aqueous mixture of ferrous sulfate and EDTA (20 g, 0.1 wt. % FeSO4, and 2 g, 1 wt. % EDTA) was added to the kettle. When the kettle temperature reached 72 °C, co-feeds including a solution of t-BHP (1.9 g) and NaPS (5.0 g) mixed with DI water (100 g), along with a separate solution of IAA (2.6 g in 100 g water) were both added simultaneously to the kettle at a rate of 1.2 g / mins. Two minutes after the start of charging the co-feed solutions, ME 2, which was prepared by mixing DI water (260 g), Disponil FES-32 emulsifier (17.0 g), BA (543.6 g), MMA (409.2 g), and PEM (67.2 g, 60% active), was added to the kettle over 55 minutes while allowing the temperature to rise to 80 °C without providing any external heat. Thirty minutes after the start of ME 2 addition, 1 -dodecanethiol (13.8 g) was added to ME 2 with mixing. Upon completion of ME 2 addition, the co-feed solutions were stopped and the batch was held for 5 minutes at 80 °C. A solution of NH4OH (5 g, 28 wt. % aq.) mixed with DI water (5.0 g) was then added to the kettle along with hot (90 °C) DI water (225 g).

[0033] ME 3, which was prepared by mixing DI water (54.0 g), Disponil FES-32 emulsifier (3.0 g), BA (104.4 g), MMA (75.6 g), and 4-hydroxy TEMPO (3.0 g), was fed to the kettle over 5 minutes. Immediately after the completion of ME 3 feed addition, NH4OH (70.0 g, 28 wt. % aq.) mixed with DI water (35 g) was added to the kettle over 3 minutes. When NH4OH addition was complete, the batch was held for 5 minutes. The addition of the co-feed solutions was resumed at a rate of 1.2 g / min until completion. Additional co-feeds including a solution of t-BHP (1.5 g) in DI water (25 g), along with a separate solution of IAA (0.7 g) in water (25 g) were both added simultaneously to the kettle at a rate of 1.2 g / min. Upon completion of addition of the second co-feed the dispersion was cooled to 25 °C. When the kettle temperature reached 45°C a solution of ACRYSOL™ ASE-60 Thickener (13.35 g in 53 g water) was added to the kettle over 10 minutes. The dispersion was filtered to remove any coagulum. The filtered opaque acrylic polymer dispersion (OAP) had a solids content of 48.3%.

[0034] Intermediate Example 4 - Preparation of OAP 4

[0035] A 5-liter, four-necked round bottom flask was equipped a paddle stirrer, thermometer, N inlet and reflux condenser. DI water (500 g) was added to the kettle and heated to 89 °C under N2. NaPS (1.90 g in 20 g water) was added to vessel immediately followed by Core #1 (125 g). Monomer emulsion 1 (ME 1), which was prepared by mixing DI water (125.0 g), Disponil FES-32 emulsifier (10.0 g), styrene (380.8 g), LOFA (2.8 g), AN (112.0 g), CHMA (56.0 g), and DVB (7.0 g), was then added to the kettle over 85 minutes. The temperature of the reaction, which was controlled at 78 °C at the start of ME 1 feed, was allowed to increase to 84 °C after 40 minutes, then allowed to increase to 92 °C after 55 minutes. Two minutes after the start of ME 1 addition, a solution of AA (5.6 g) in DI water (35 g) was added to the flask. Forty minutes after the start of ME 1 addition, a solution of NaPS (0.5 g in 30 g water) was added to the kettle over 45 minutes. Upon completion of the ME 1 feed, the reaction was cooled to 72 °C.

[0036] When the kettle temperature reached 80 °C, an aqueous mixture of ferrous sulfate and EDTA (20 g, 0.1 wt. % FeSO4, and 2 g, 1 wt. % EDTA) was added to the kettle. When the kettle temperature reached 72 °C, co-feeds including a solution of f-BHP (1.9 g) and NaPS (5.0 g) mixed with DI water (100 g), along with a separate solution of IAA (2.6 g in 100 g water) were both added simultaneously to the kettle at a rate of 1.2 g / mins. Two minutes after the start of charging the co-feed solutions, ME 2, which was prepared by mixing DI water (260 g), Disponil FES-32 emulsifier (17.0 g), BA (598.8 g), MMA (409.2 g), and MAA (12.0 g), was added to the kettle over 55 minutes while allowing the temperature to rise to 80 °C without providing any external heat. Thirty minutes after the start of ME 2 addition, 1 -dodecanethiol (13.8 g) was added to ME 2 with adequate mixing. Upon completion of ME 2 addition, the co-feed solutions were stopped and the batch was held for 5 minutes at 80°C. A solution of NH4OH (5 g, 28 wt. % aq.) mixed with DI water (5.0 g) was then added to the kettle along with hot (90 °C) DI water (225 g).

[0037] ME 3, which was prepared by mixing DI water (54.0 g), Disponil FES-32 emulsifier (3.0 g), BA (104.4 g), MMA (75.6 g), and 4-hydroxy TEMPO (3.0 g), was fed to the kettle over 5 minutes. Immediately after the completion of the ME 3 feed addition, NH4OH (70.0 g, 28 wt. % aq.) mixed with DI water (35 g) was added to the kettle over 3 minutes. When NH4OH addition was complete, the batch was held for 5 minutes. The addition the co-feed solutions was resumed at a rate of 1.2 g / min until completion. Additional co-feeds including a solution of z-BHP (1.5 g) in DI water (25 g), along with a separate solution of IAA (0.7 g) in water (25 g) were both added simultaneously to the kettle at a rate of 1.2 g / min. Upon completion of addition of the second co-feed, the dispersion was cooled to 25 °C. When the kettle temperature reached 45°C a solution of ACRYSOL™ ASE-60 Thickener (13.35 g in 53 g water) was added to the kettle over 10 minutes. The dispersion was filtered to remove any coagulum. The filtered opaque acrylic polymer dispersion (OAP) had a solids content of 48.2%.

[0038] Comparative Intermediate Example 1 - Preparation of an Acrylic Binder

[0039] A 5-liter, four necked round bottom flask was equipped a paddle stirrer, thermometer, N2 inlet and reflux condenser. DI water (952 g) and Disponil FES-32 (1.76 g) was added to the vessel and heated to 88 °C under N2. A monomer emulsion was prepared by mixing DI water (550.7 g), Disponil FES-32 (49.25 g), 1 -dodecanethiol (20.48 g), BA (1191.9 g), MMA (890.75 g), and PEM (68.95 g, 60% active). A portion of the monomer emulsion (133 g) was added to the flask, followed by addition of ammonium persulfate (5.3 g in 48 g water). After the peak exotherm was noted, the balance of the monomer emulsion was added to the flask over 80 minutes; concurrently, ammonium persulfate (2.3 g in 96 g water) was added to the flask over 80 minutes. When the monomer emulsion and ammonium persulfate solution feeds were completed, the contents were cooled to 75 °C.

[0040] While cooling, ammonium hydroxide (7.43 g of 28% solution in 18.7 g water), an aqueous mixture of ferrous sulfate and EDTA (14 g, 0.1 wt. % FeSO4, and 1.4 g, 1 wt. % EDTA), t-BHP (1.9 g of 70% solution in 11 g water), and IAA (1.3 g in 24 g water) were sequentially added to the flask. When temperature reached 75 °C, additional t-BHP (1.9 g of 70% solution in 11 g water) was added to the flask, followed by the addition of IAA (3 g in 47 g water) over 20 minutes. The flask was then cooled to below 40°C. When temperature reached 50°C, DMEA (65.8 g in 53 g water) was added to the flask over 10 minutes. The dispersion was then filtered to remove any coagulum.

[0041] Comparative Intermediate Example 2 - Preparation of a Dispersion of Opaque Polymer Particles

[0042] A 5-liter, four necked round bottom flask was equipped a paddle stirrer, thermometer, N2 inlet and reflux condenser. DI water (730.64 g) and acetic acid (0.28 g in 1.64 g water) was added to the vessel and heated to 89 °C under N2. Sodium persulfate (NaPS, 3.39 g in 24.55 g water) was added to vessel immediately followed by Core #1 (218.53 g). Monomer emulsion 1 (ME 1), which was prepared by mixing DI water (69.55 g), Polystep A- 16-22 emulsifier (5.5 g), styrene (69.95 g), MAA (8.43 g), and MMA (61.53 g), was then added to the vessel over 60 minutes. The temperature of the reaction was held constant at 78 °C for the duration of ME 1 feed and a DI water rinse (32.73 g) was added upon completion. Upon completion of the ME 1 feed, monomer emulsion 2 (ME 2), which was prepared by mixing DI water (217.64 g), Polystep A- 16-22 emulsifier (11.09 g), styrene (657 g), linseed oil fatty acid (4.17 g), allyl methacrylate (2.13 g), and methacrylic acid (12.6 g) was fed to the vessel over 60 minutes. The temperature of the reaction mixture was allowed to increase to 84 °C after 15 min and allowed to increase to 92 °C after 25 min. Simultaneously with the start of the ME 2 feed, a solution of NaPS (0.93 g in 62. 18 g water) was cofed to the vessel over 65 minutes. Upon completion of the ME 2 feed, a DI water rinse of 32.73 g was added to the vessel followed by an aqueous mixture of ferrous sulfate and EDTA (16.36 g, 0.1 wt. % FeSCU, and 1.64 g, 1 wt. % EDTA) along with DI water (182.45 g, >60°C) and the reaction was held at 90-92 °C for 15 minutes. During the hold, 182.48 g of DI water (>60°C) was added to the vessel.

[0043] ME 3, which was prepared by mixing DI water (57.27 g), Polystep A-16-22 emulsifier (2.05 g), styrene (167.73 g), and 4-hydroxy TEMPO (1.88 g), was fed to the vessel over 5 min and temperature was allowed to drop to 85°C. Immediately after the ME 3 feed addition was complete, a DI water rinse of 32.73 g was added to the vessel followed by sodium hydroxide (NaOH, 29.45 g, 50 wt. % aq.) mixed with DI water (572.73 g, >60°C) was added to the vessel over 10 min. When NaOH addition was complete, the batch was held for 5 min. Upon completion of the hold, a post-polymerization solution of t-BHP (2.12 g, 70 wt. % aq.) in DI water (24.55 g) was added to the vessel and a separate solution of isoascorbic acid (IAA, 1.1 g) in water (65.45 g) was fed to the vessel over 25 minutes. Upon completion of addition of the second co-feed, DI water (94.11 g) was added to the vessel and the dispersion was cooled to room temperature and filtered to remove any coagulum.

[0044] Table 1 shows the components and amounts used to prepare the LASD wet formulations. TAMOL, TERGITOL, and ACRYSOL are Trademarks of The Dow Chemical Company or its Affiliates. Starch refers to Penford Gum 200 Potato Starch: Blowing Agent refers to Expancel 031 WUF 40 Blowing Agent; and Thickener refers to ACRYSOL™ ASE-60 Thickener. All units are in parts by weight (pbw).

[0045] Table 1 - LASD Wet Formulation

[0046] Coating formulations were prepared from the components listed in Table 1 in the order listed. The components were mixed with an overhead stirrer for 10 min, then allowed to equilibrate overnight. Viscosity Measurement

[0047] Brookfield viscosity was measured at 25 °C using a Brookfield RV DV-I+ viscometer with a Brookfield Helipath stand and a T-Bar type T-E spindle for coatings with viscosities between 1,000,000 and 10,000,000 centipoise (cP). A Brookfield T-Bar type T-C and Type T-F spindle may be used for viscosities between 200,000 and 1,000,000 cP, and 10,000,000 and 20,000,000 cP, respectively. The speed of rotation of the spindle is 0.5 rpm and the spindle is run for 120 seconds (i.e., under no shear conditions) before the measurement is made. The stand allows the spindle to move down into the coating during rotation to ensure proper measurement of highly viscous materials. Brookfield viscosity (B.V) is measured in centipoise (cP) x 104. Table 2 illustrates the corrected material amounts (pbw) for the dry LASD formulation.

[0048] Table 2 - LASD Dry Formulation

[0049] Preparation of Coated Substrates

[0050] LASD formulations were manually applied to 1.6-mm x 12.7-mm x 200-mm hardened carbon steel Oberst bars to create a coating with a wet areal density of 4 kg / m2to 5 kg / m2. The coatings were then cured at ambient temperature for 30 min, then baked at 150 °C for 30 min to create a cured coating with dry areal density of 3 kg / m2. After cooling, the coated bars were tested according to ASTM E-756 to determine composite loss factor (CLF, which is a metric for damping performance) at an interpolated frequency of 200 Hz at 7 different temperatures (9 °C, 19 °C, 29 °C, 39 °C, 48°C, 58 °C, and 69 °C). Table 3 shows the measured CLF values for all compositions at each temperature. Table 3 - Area Under the CLF Curve

[0051] Total damping performance was determined by summing the measured CLF values at each temperature to calculate a metric (CLFSUM) for overall damping performance independent of peak temperature. The viscosities for the samples were in the range of from 500,000 cP to 2,000,000 cP. Table 4 illustrates CLFSUM for the examples.

[0052] Table 4 - Properties of Cured LASD Coatings

[0053] The data demonstrate that cured coatings formed from compositions containing the binder- coated opacifying polymer particles exhibited improved damping performance as compared with compositions prepared using opaque polymer particles and distinct binder particles or binder particles alone. Remarkably, cured formulations containing binder particles alone exhibited better damping than formulations containing a combination of binder particles and opaque polymer particles.

Claims

Claims:

1. An article comprising a coating superposing a metal substrate, wherein the coating comprises an aqueous dispersion of a) binder-coated opacifying polymer particles; b) extender particles; c) starch; d) a blowing agent; and e) a rheology modifier; wherein the binder-coated opacifying polymer particles comprise: i) a water-occluded core comprising from 20 to 60 weight percent structural units of a salt of a carboxylic acid monomer and from 40 to 80 weight percent structural units of a nonionic monoethylenically unsaturated monomer; ii) a polymeric shell having a Tgin the range of from 60 °C and 120 °C; and iii) a polymeric binder layer superposing the shell, which polymeric binder layer has a Tgof not greater than 50 °C and comprises structural units of at least one monoethylenically unsaturated monomer; wherein the weight-to-weight ratio of structural units of monomers in the water-occluded core to the shell 1: 10 to 1:20; the weight-to-weight ratio of the polymeric binder layer to the sum of the shell and the structural units of monomers in the core is in the range of from 1 : 1 to 3.5: 1 ; wherein the z-average particle size of the polymer particles is in the range of from 300 nm to 750 nm; and wherein the coating has a Brookfield viscosity in the range of from 200,000 cP to 20,000,000 cP; and wherein coating has wet areal density in the range of from 0.35 kg / m2to 10 kg / m2.

2. The article of Claim 1 wherein the weight-to-weight ratio of the extender particles to the binder-coated opacifying polymer particles is preferably in the range of from 20:80 to 80:20.

3. The article of Claim 2 wherein the binder-coated opacifying polymer particles and extender particles comprise at least 90 weight percent of the components in the composition, excluding water.

4. The article of Claim 3 wherein the water-occluded core of the binder-coated opacifying polymer particles comprises from 30 to 40 weight percent structural units of a salt of the carboxylic acid monomer based on the weight of structural units of monomers in the core, and60 to 70 weight percent structural units of the nonionic monoethylenically unsaturated monomer, based on the weight of the shell.

5. The article of Claim 4 wherein the carboxylic acid monomer is acrylic acid or methacrylic acid; the nonionic monomer is an acrylate or methacrylate selected from the group consisting of ethyl acrylate, n-butyl acrylate, / -butyl acrylate 2-ethylhexyl acrylate, methyl methacrylate, n- butyl methacrylate, / -butyl methacrylate, isobutyl methacrylate, isobomyl methacrylate, lauryl methacry late, and cyclohexyl methacrylate; and the shell has a Tgin the range of from 90 °C to 115 °C.

6. The article of Claim 5 wherein the nonionic monomer is methyl methacrylate, and at least 70 weight percent of the shell is comprised of structural units of styrene.

7. The article of Claim 3 wherein the extender particles are calcium carbonate; silica; alumina; kaolin; clay; talc; graphite: mica; diatomaceous earth; glass powder, fibers, or microspheres; aluminum hydroxide; perlite; barium sulfate; magnesium carbonate; calcium dihydrate; rock wool; Wollastonite; zeolite; ceramic or thermoplastic microspheres; polymeric fibers, or crosslinked rubber particles.

8. The article of Claim 6 wherein the filler particles are a combination of calcium carbonate and mica particles; wherein the composition has a Brookfield viscosity in the range of from 500,000 cP to 10,000,000 cP.

9. The article of Claim 1 where the starch is potato starch or com starch, wherein the composition further comprises a defoamer, a dispersant, a surfactant, and a colorant.

10. A method comprising the step of curing the coating of the article of any of Claims 1 to 9 to create a cured coated article with an areal dry density in the range of from 0.3 kg / m2to 5 kg / m2.

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