Patent Application
20080039564
The aqueous dispersion of polymeric microparticles suitable for use in the present invention, may be thermoplastic and may include functionality that permits crosslinking with suitable crosslinking agents such as but not limited to aminoplasts or polyisocyanates. The polymeric microparticles are essentially hydrophobic, and dispersible in water. The term “dispersion” and like terms mean the polymeric microparticles are capable of being distributed throughout the water as finely divided particles such as latex. See Hawley's Condensed Chemical Dictionary, (12th edition, 1993) at page 435.
Aqueous dispersions of polymeric microparticles and their methods of preparation are disclosed in U.S. Pat. No. 6,531,541 at col. 3, line 59, to col. 11, line 11, the portions of which are hereby incorporated by reference.
Generally, the polymeric microparticles are present in the coating composition of the present invention in an amount of from 4 to 70, or 5 to 40 percent by weight based on total weight of the composition. Water is present in the composition in an amount of from 5 to 40, or 15 to 30 percent by weight based on total weight of the coating composition. The coating composition of the present invention comprises a filler. While the inventors do not wish to be bound by any theory, it is believed that the filler is responsible for the sound dampening properties of the coating. The filler is present in the coating composition of the present invention in an amount of from 20 to 90 percent by weight, or 40 to 70 percent by weight based on total weight of the composition.
In an embodiment, the filler may comprise calcium magnesium carbonate, barium sulfate, a mineral fiber such as calcium metasilicate and mixtures thereof. In a further embodiment, the filler may optionally include an organically modified clay (organoclay) such as those commercially available under the trademark BENTONE.
Not intending to be bound by any theory, it is believed that calcium magnesium carbonate provides sound dampening properties and may be present in the coating composition of the present invention in an amount of from 5 to 90 percent by weight based on total weight of the coating composition.
Not intending to be bound by any theory, it is believed that barium sulfate improves coating appearance and may be present in the coating composition of the present invention in an amount of from 5 to 50 percent by weight based on total weight of the coating composition.
Not intending to be bound by any theory, it is believed that mineral fiber provides sound dampening properties and may be present in the coating composition of the present invention in an amount of from 10 to 70 percent by weight based on total weight of the coating composition.
Organoclays may be present in the coating composition of the present invention in an amount of from 0.05 to 2 percent by weight, based on total weight of the coating composition.
The plasticizer for use in the coating composition of the present invention comprises at least two different plasticizers. Non-limiting examples of suitable plasticizers may include adipates, benzoates, glutarates, phthalates, butyrates, phosphates, polyesters, sebacates, glycols such as but not limited to alkylene glycol containing from two to six carbon atoms, sulfonamides and mixtures thereof. In an embodiment, the plasticizer comprises a mixture selected from phthalates, butyrates and glycols. In a further embodiment, the plasticizer is a mixture of benzyl phthalate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate and propylene glycol. The amount of plasticizer present in the coating composition may be from greater than 0.1 to less than 20 percent by weight based on total weight of the coating composition. Amounts of 0.1 percent or less by weight do not result in good appearance, whereas amounts of 20 percent or more by weight adversely affect appearance and sound dampening properties of the coating.
The coating composition of the present invention may include a variety of other optional ingredients and/or additives. The use of these ingredients and/or additives may be dependent on the particular application of the composition. Non-limiting examples of such ingredients and/or additives may include but are not limited to dyes or pigments such as carbon black or graphite, reinforcements, organic rheology agents, surfactants, corrosion inhibitors, organic solvents, foam control agents, expandable microspheres, antioxidants, and mixtures thereof. These optional ingredients and additives, may be present individually in amounts of from 0 to 20 percent by weight based on total weight of the coating composition.
In another embodiment of the present invention plastisols such as polyvinyl chloride may be present in the coating composition in an amount of from 2 to 10 percent by weight based on total weight of the coating composition. Not intending to be bound by any theory, it is believed that plastisols may improve sound dampening properties.
The viscosity of the coating composition of the present invention may depend on its use or application as well as type of equipment employed, desired film thickness and sag resistance. In alternate embodiments, the viscosity of the coating composition of the present invention may be greater than 1000, or from 1000 to 1,000,000 centipoise (“cp”) measured at 2 RPM with a #7 spindle Brookfield measurement. In a further embodiment, a sprayable composition may have a viscosity less than 100,000 cp at 20 RPM reading on the Brookfield viscometer at ambient temperature (about 25° C.).
The coating composition of the present invention may be prepared using various conventional techniques and equipment known in the art. In an embodiment, the polymeric microparticle dispersion may be mixed with the filler and other components of the coating composition in a high-energy vacuum mixer such as Dual Disperser Model HHL-2-1000 commercially available from Hockmeyer.
The coating composition of the present invention may be applied to the surface of a substrate using a wide variety of conventional techniques and equipment known in the art, Non-limiting examples may include spraying, extrusion, or by hand with a blade. Suitable substrates for use in the present invention are numerous and varied. Non-limiting examples may include but are not limited to those formed from metal, polymers such as thermoset materials and thermoplastic materials, and combinations of metal and polymeric substrates. Suitable metal substrates that can be coated according to the present invention include ferrous metals such as iron, steel, and alloys thereof non-ferrous metals such as aluminum, zinc, magnesium and alloys thereof, and combinations thereof. In non-limiting embodiments, the substrate may be formed from cold rolled steel, electrogalvanized steel such as hot dip electrogalvanized steel or electrogalvanized iron-zinc steel, aluminum or magnesium. The substrate to be coated may be bare, pretreated or prepainted (for example by electrocoating) prior to application of the sound dampening composition.
Useful thermoset materials may include polyesters, epoxides, phenolics, polyurethanes such as reaction injected molding urethane (RIM) thermoset materials and mixtures thereof. Useful thermoplastic materials include thermoplastic polyolefins such as polyethylene and polypropylene, polyamides such as nylon, thermoplastic polyurethanes, thermoplastic polyesters, acrylic polymers, vinyl polymers, polycarbonates, acrylonitrile-butadiene-styrene (ABS) copolymers, EPDM rubber, copolymers and mixtures thereof.
The thickness of the applied coating in the present invention is not believed to be critical and may be adjusted such that the final dried coating is effective in suppressing noise and vibration transmission to a desired extent. In alternate embodiments, the dried coating may have a thickness of at least 1000 microns thick, or from 2000 to 5000 microns. After applying the aqueous coating composition of the present invention to the substrate surface, it may first be permitted to dry partially at ambient or slightly elevated temperature, followed by heating of the coated substrate. Drying of the coating can be performed by any suitable method such as air drying, oven drying or induction heating. When heat is applied, drying temperatures will typically be in the range of from about 110° C. to 175° C.
In general, the coating composition of the invention finds application in the quarter panels, the roof, the door, the interior, the floor pan, and the wheel house of motor vehicles. In other applications, the coating composition can be used in a suitable position on the inside or outside of a structure, e.g., a vehicle or an aircraft or a building, to provide maximum sound damping performance.
The following examples are intended to illustrate the invention, and should not be construed as limiting the invention in any way.
The Examples show the preparation of various aqueous sound dampening compositions. Example 1 was a control with no plasticizer in the composition. Examples 2, 3, 5 and 6 were of the invention containing at least two different plasticizers in the composition. Examples 4, 7, 8 and 9 were comparative Examples. Example 7 contained only one plasticizer, Example 4 contained three different plasticizers, but at a low total plasticizer content. Examples 8 and 9 contained three different plasticizers but at a high total plasticizer content. Table 1 below summarizes the various formulations.
The ingredients of each of the compositions shown in Table 1 below were mixed at low agitation in a pint-sized container using an air-driven motor. The ingredients were added to the container in the order shown in Table 1, and the mixing speed was increased to maintain a vortex throughout the addition. Each sample was placed in a vacuum chamber equipped with an agitator and a vacuum of at least 700 mm Hg to the agitated sample. The sample was removed when foaming subsided (35 minutes).
1Aqueous resinous dispersion of polymeric microparticles prepared as generally described in U.S. Pat. No. 6,531,541. Resin solids content of about 40 percent.
2PM 210: Water dispersion of 33% sodium salt of naphthalenesulfonic acid.
3Aquablack 245: Water dispersion of carbon black commercially available from Borden Chemical Company.
4Foamaster 111: Hydrocarbon defoamer commercially available from Cognis Canada.
5Dolocron 4512: Dolomite calcium magnesium carbonate commercially available from Specialty Minerals.
6Vansil W-10: Calcium metasilicate from R.T. Vanderbilt Company.
7Sparwite W-10: Barium sulfate commercially available from Mountain Minerals Company.
8Santicizer 278: 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate ester commercially available from Monsanto Chemical Company.
9Propylene Glycol: Commercially available from Dow Chemical.
10TXIB: 2,2-dimethyl-1-(methylethyl)-1,3-propanediyl bis(2-methylpropanoate) commercially available from Eastman Chemical Company.
11Acrysol RM-8: Rheology modifier water-soluble polyurethane commercially available from Rohm & Haas.
12PM 495: Rheology modifier water dispersion of 10% Bentone EW organoclay.
Draw downs of 3-4 inch long samples using a 3-inch wide 120-mil thick coating template were prepared on test panels coated with ED-6060 electrocoat which is commercially available from PPG Industries, Inc. of Pittsburgh, Pa. Each draw down was air dried at ambient temperature (25° C.).
Mudoracking was evaluated on a separate set of panels. The mudcracking determination was a visual determination based upon number, width and length of cracks. The coating on each panel was cured for one hour at ambient temperature (25° C.) and then for 7 minutes at 110° C., followed by a 30-minute exposure to ambient temperature and finally a 15-minute exposure to 175° C.
The sound damping of each coating was measured using the Oberst ASTM Test Method E756-93 (“Standard Test Method for Measuring Vibration-Damping Properties of Materials”), Sections 3 and 10. The principal measure of sound deadening in this test is loss factor, the ratio of loss modulus to storage modulus of the material. Oberst values typically range from 0.001 for uncoated steel (thickness 30 mils) (if the steel panel is struck, one would hear a “clang”) to 0.01 (“bong”) to 0.1 (“bunk”) to 0.5 (“thud”) for increasingly efficient coatings. The Oberst test measures the sound loss factor of the coating-substrate composite.
Each test sample was applied to an Oberst Bar, which is a metal bar formed from special oil-hardening ground flat stock, AISI/SAE GRD 0-1, 1/32 inch (0.8 mm) thick, ½ inch (12.7 mm) wide from McMaster-Carr, part number 89705-K121 and cured as described above. The weight of each cured coating was 9.0±0.12 grams. The Oberst loss factor values were normalized to 9.0 grams for comparison. Composite loss factors were compared at 200 Hz at temperatures of 0, 20 and 40° C. The results are reported in Table 2 below.
The experimental results summarized in Table 2 above show that the composition of the invention (Examples 2, 3, 5 and 6) have in general better appearance and better sound dampening properties than the control (Example 1) and the comparative Examples (Examples 4, 7, 8 and 9).
Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.
