Liquid applied sound damping composition

Abstract

The present invention relates to a composition comprising an aqueous dispersion of a) polymer particles; b) a rheology modifier; c) extender particles; and d) a dialkanol amine or trialkanol amine; wherein the polymer particles have a calculated Tg in the range of from -30 °C to 60 °C; and wherein the composition has a Brookfield viscosity at 25 °C in the range of from 200,000 cP to 20,000,00 cP. The composition of the present invention is useful for forming coatings in abating blistering in liquid applied sound damping applications with little or no blistering.

Description

[0001] LIQUID APPLIED SOUND DAMPING COMPOSITION

[0002] Background of the Invention

[0003] The present invention relates to a composition suitable liquid applied sound damping (LASD) coatings. The composition forms a coating with little or blister formation when dried above the boiling point of water.

[0004] Coatings for LASD applications are designed to reduce vibration in rigid structures through viscoelastic damping. In the automotive industry, for example, vibration is typically reduced by applying a coating of a highly viscous water-borne dispersion of a viscoelastic polymer and mineral filler on the floor pan of the vehicle, then drying the coating at a temperature between 120 °C and 190 °C. At such temperatures, water vaporizes with concomitant rapid expansion of the coating, which sometimes results in the formation of large and undesired cavities within the coating. These craters are commonly referred to as “pita defects” because the structure resembles a pita bread pocket. These large defects often lead to mechanical failure during application and are therefore deemed unacceptable by automotive OEMs.

[0005] In addition to reducing coating defects, it is desirable to control the extent of coating expansion because automobiles are currently designed with reduced space and narrow clearance. Thinner LASD coatings, therefore, lessen the risk of interference with nearby components.

[0006] Accordingly, it would be desirable in the field of LASD compositions to discover a formulations that can be applied to a substrate and subjected to high temperatures with substantial reduction in blister formation and controlled expansion.

[0007] Summary of the Invention

[0008] The present invention addresses a need in the art by providing a composition comprising an aqueous dispersion of a) polymer particles; b) a rheology modifier; c) extender particles; and d) a dialkanol amine or trialkanol amine; wherein the polymer particles have a calculated Tgin the range of from -30 °C to 60 °C; and wherein the composition has a Brookfield viscosity at 25 °C in the range of from 200,000 cP to 20,000,00 cP.

[0009] The composition of the present invention is useful as coatings in LASD applications. Detailed Description of the Invention

[0010] The present invention is a composition comprising an aqueous dispersion of a) polymer particles; b) a rheology modifier; c) extender particles; and d) a dialkanol amine or trialkanol amine; wherein the polymer particles have a calculated Tgin the range of from -30 °C to 60 °C; and wherein the composition has a Brookfield viscosity at 25 °C in the range of from 200,000 cP to 20,000,00 cP.

[0011] Examples of suitable aqueous dispersions of polymer particles (latexes) include acrylic latexes, styrene- acrylic latexes, and vinyl esters such as vinyl acetate or vinyl versatate. The Tgof the polymer particles, as calculated by the Fox equation, is in the range of from -30 °C or from -20 °C or from -10 °C, to 60 °C or to 40 °C or to 30 °C. The concentration of the polymer particles is typically in the range of from 20 to 40 weight percent, based on the weight of the composition.

[0012] Examples of suitable rheology modifiers include hydrophobically modified ethylene oxide urethanes (HEURs); alkali -swellable emulsions (ASEs); hydrophobically modified alkali-swellable emulsions; (HASEs); and hydroxyethyl cellulose. The concentration of the rheology modifier is sufficient to adjust the viscosity of the composition to the desired level, which is 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 in the Examples section. The concentration of the rheology modifier is typically in the range of from 0.5 or from 1 weight percent, to 10 or to 5 weight percent based on the weight of the composition.

[0013] The composition further comprises extender particles, which typically have a median diameter average (D50) particle size in the range of from 1 pm to 50 pm as measured by laser diffraction. 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, glass microspheres, aluminum hydroxide, perlite; barium sulfate, magnesium carbonate, calcium dihydrate, rock wool, Wollastonite, zeolite, ceramic microspheres, thermoplastic microspheres, polymeric fibers, and crosslinked rubber particles. Extenders that include calcium carbonate particles are preferred. The concentration of the extender particles is preferably in the range of from 50 to 75 weight percent, based on the weight of the composition. Preferably, the extender particles and the polymer particles compose at least 90 or at least 95 weight percent of the solids in the composition.

[0014] Dialkanol and trialkanol amines are secondary or tertiary amines functionalized with two or three hydroxyl groups. Examples of suitable dialkanol and trialkanol amines include diethanol amine, methyl diethanolamine, ethyl diethanolamine, triethanolamine, tri-n-propanol amine, diisobutanolamine, triisopropanol amine, diisopropanol amine, bis(2-hydroxypropyl)amine, bis(3-hydroxypropyl)amine, 3- [(2-hydroxyethyl)amino]-l -propanol, N-butyldiethanolamine, and 3-(diethylamino)-l,2-propanediol. A combination of amines may also be used.

[0015] The concentration of the dialkanol amine or trialkanol amine is preferably in the range of from 0.1 or from 0.2 or from 0.5 or from 1 weight percent, to 10 or to 5 weight percent, based on the weight of the composition.

[0016] Preferably, the composition has a solids content in the range of from 65 or from 70 or from 75 weight percent, to 90 or to 85 or to 80 weight percent, based on the weight of the composition.

[0017] The composition of the present invention may further comprise other additives including dispersants, colorants, surfactants, defoamers, starch, and expandable microspheres. In another aspect, the present invention is a method comprising the steps of applying a coating of the composition onto the surface of a substrate such as metal, plastic, or ceramic, then heating the coating to a temperature in the range of from 100 °C or from 130 °C, to 200 °C or to 170 °C, to form a dried coating with an areal density in the range of from 0.5 1 Kg / m2or from 1 Kg / m2, to 5 Kg / m2or to 4 Kg / m2.

[0018] The composition of the present invention has been found to form a dried coating that is especially resistant to blister formation when heated to a temperature above the boiling point of water.

[0019] Examples

[0020] Table 1 illustrates the materials and amounts used to prepare the LASD composition. Acrylic Emulsion refers to a 2.5 acrylic acid / 16 acrylonitrile / 67.5 butyl acrylate / 14 styrene latex with a solids content of 50%; Defoamer refers to DOWSIL™ 8590 Additive; Dispersant refers to TAMOL™ 1254 Polyacid Pigment Dispersant; Surfactant refers to TERGITOL™ 15-S-40 Nonionic Surfactant; Colorant refers to UCD 1530E Jet Carbon Black; CaCCL refers to Titan 200 Calcium Carbonate Filler; Mica refers to Mica 325 Filler; Baking Additive 1 refers to Penford Gum 200 Starch Baking Additive; Baking Additive 2 refers to Expancel 031WUFX40 Expandable Microspheres Baking Additive; to RM refers to ACRYSOL™ ASE-60 Rheology Modifier (50% wt% aq.). (ACOUSTICRYL, DOWSIL, TAMOL, and TERGITOL are all Trademarks of The Dow Chemical Company or its Affiliates.)

[0021] LASD formulations were prepared by blending the materials with an overhead mixer, then (optionally) adding 2 pbw of the amine. The mixture was equilibrated for 24 h prior to testing.

[0022] Table 1 - LASD Formulation

[0023] 1Sufficient RM was added to achieve a Brookfield viscosity between 1,000,000 and 2,000,000 cP. Viscosity Measurement

[0024] Brookfield viscosity of the compositions 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. The stand allows the spindle to move down into the coating during rotation to ensure proper measurement of highly viscous materials. Brookfield viscosity measurements were taken 24 h after blending the materials with an overhead mixer. Prior to measuring viscosity, the coatings were de-aerated using an overhead mixer at 1600 RPM for 1 min.

[0025] Table 2 illustrates the amines used in evaluating blistering and the Brookfield viscosities of the samples with the initial rheology modifier unadjusted (RMBVO) and post addition of rheology modifier (RMBVf). AMP 95 refers to AMP-95 2-amino-2-methyl-l- propanol. Viscosities are in units of cP x 104. %RM add, refers to additional rheological modifier. Table 2 - Amines Evaluated for Blistering Sample Testing

[0026] Amine additives were added to 9 separated LASD compositions to target 2 pbw for each additive. Each of the amines listed in Table 2 was added into pre- weighed formulations; the compositions were then mixed with a Flacktek high-speed mixer at 2000 rprn for 1 min. Coatings were cast on pre-weighed, untreated aluminum panels using a 2.9-mm mold to create a 2” x 3.5” drawdown. The cast coatings were cured at room temperature for 30 min, then baked in an oven at 150 °C for 30 min. The coated panels were removed from the oven and each sample was visually inspected for any defects. The panels were then weighed and measured for coating thickness using a digital thickness gauge; 5 measurements of the coating were taken at the top left, top right, bottom left, bottom right, and center.

[0027] Table 3 illustrates the pita formation (or non-formation) of expanded samples. Percent Expansion is reported where no defects (pita) were observed.

[0028] The data demonstrate the effectiveness of dialkanol and trialkanol amines in abating blistering.

[0029] In contrast, monoalkanol amines and trialkylamines were found to be just as ineffective as no additive in abating blistering.

Claims

Claims:

1. A composition comprising an aqueous dispersion of a) polymer particles; b) a rheology' modifier; c) extender particles; and d) a dialkanol amine or trialkanol amine; wherein the polymer particles have a calculated Tgin the range of from -30 °C to 60 °C; and wherein the composition has a Brookfield viscosity at 25 °C in the range of from 200,000 cP to 20,000,00 cP.

2. The composition of Claim 1 wherein, based on the weight of the composition, the concentration of the polymer particles is in the range of from 20 to 40 weight precent; the concentration of the rheology modifier is in the range of from 0.5 to 10 weight percent; the concentration of the extender particles is in the range of from 50 to 75 weight percent; and the concentration of the dialkanol amine or trialkanol amine is in the range of from 0.1 to 10 weight percent; wherein the composition has a Brookfield viscosity’ at 25 °C in the range of from 1,000,000 cP to 10,000,00 cP.

3. The composition of Claim 2 wherein the extender particles are one or more particles selected from the groups consisting of calcium carbonate, silica, alumina, kaolin, clay, talc, graphite, mica, diatomaceous earth, glass powder, fibers, glass microspheres, aluminum hydroxide, perlite; barium sulfate, magnesium carbonate, calcium dihydrate, rock wool, Wollastonite, zeolite, ceramic microspheres, thermoplastic microspheres, polymeric fibers, and crosslinked rubber particles.

4. The composition of Claim 3 wherein the extender particles comprise calcium carbonate particles, and the dialkanol amine or trialkanol amine is one or more amines selected from the groups consisting of diethanol amine, methyl diethanolamine, ethyl diethanolamine, triethanolamine, tri-zi-propanol amine, diisobutanolamine, triisopropanol amine, diisopropanol amine, bis(2-hydroxypropyl)amine, bis(3-hydroxypropyl)amine, 3-[(2-hydroxyethyl)amino]-l- propanol, N-butyldiethanolamine, and 3-(diethylamino)-l,2-propanediol; wherein the concentration of the dialkanol amine or trialkanol amine is in the range of from 1 to 5 weight percent, based on the weight of the composition.

5. The composition of Claim 3 where the di alkanol amine or trialkanol amine is one or more amines selected from the groups consisting of diethanol amine, methyl diethanolamine, triethanolamine, and triisopropanol amine, wherein the concentration of the dialkanol amine or trialkanol amine is in the range of from 1 to 5 weight percent, based on the weight of thecomposition; and wherein the extender particles comprise calcium carbonate particles and mica particles.

6. The composition of Claim 3 wherein the polymer particles are acrylic, styrene-acrylic, or vinyl ester polymer particles which have a Tgin the range of from -10 °C to 30 °C.

7. A process comprising the steps of applying a coating of the composition of any of Claims 1 to 6 onto the surface of a substrate, then heating the coating to a temperature in the range of from 100 °C to 200 °C to form a dried coating with an areal density in the range of from 0.5 Kg / m2to 5 Kg / m2.

8. The process of Claim 7 wherein the coating is heated to a temperature in the range of from 130 °C to 170 °C, wherein the substrate is metal.

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