SOUND DAMPING MULTI-LAYERED METALLIC SHEET, ARTICLES INCLUDING SAME, AND METHODS THEREOF

The teachings herein relate to sound damping materials and particularly to sound damping materials for castings. The sound damping material includes a surface layer including an elastomer and a filler. Preferably the filler includes glass or ceramic beads. The surface layer preferably has a textured surface for contacting with the casting. Preferably the filler has a diameter that provides or contributes to the textured surface. For example, a portion of the filler may have a diameter that is greater than the average thickness of the surface layer. The sound damping material includes one or more metallic layers, preferably for applying a force to a surface of the casting. The sound damping material preferably includes two metallic layers that are separated by a core polymeric layer.

FIELD

The teachings herein relate to composite materials having improved sound damping performance, devices including the composite materials and related methods. The composite material preferably includes a polymeric core layer. The composite materials preferably include a surface layer includes an elastomer having a glass transition temperature of about 10° C. or less and/or a crystallinity of about 5 percent or less.

BACKGROUND

There continues to be a need for new materials and articles for sound damping of components that generate or transmit sound, particularly components that include a casting (e.g., a metal casting).

Many sound damping materials use foams, or other materials having voids and or porous structures. However, such materials may deteriorate and/or lose sound damping performance over time and/or at elevated temperatures.

There is a need for sound damping materials having one or more of the following properties: the sound damping performance does not deteriorate over time; the sound damping performance does not deteriorate at elevated temperatures; the sound damping material is light weight; the sound damping material can be used on castings that are not machined to a smooth surface; the sound damping material is effective at reduce peak sound in the 400 Hz to 800 Hz range; the sound damping material is corrosion resistant; the sound damping material has good adhesion; the sound damping material has good resistance to humidity, acids, base, oil, or any combination thereof; the sound damping material applies pressure over a large portion of the contact area with the casting; or any combination thereof. There is a similar need for sound damping articles having the same properties. There is also a need for methods for making new sound damping materials.

SUMMARY

One or more of the aforementioned needs are achieved with the sound damping material and sound damping articles according to the teachings herein. In particular, applicant has identified composite structures that provide surprising sound damping performance while being generally light weight, easy to manufacture and useful in a variety of applications with different temperature and environmental exposures.

One aspect of the teachings herein is directed at a sound damping article for attaching to a casting comprising a multi-layer composite including: a first metallic layer; a second metallic layer; one or more core layers interposed between the first metallic layer and the second metallic layer so that direct contact between the first metallic layer and the second metallic layer is avoided, wherein each of the one or more core layers is formed of a polymeric material; and a surface layer (i.e, damping surface) for contacting the casting, wherein the surface layer is an outside layer over the first metallic layer or the second metallic layer, wherein the surface layer includes an elastomeric composition having a glass transition temperature of about 10° C. or less, a crystallinity of about 5 percent or less at 23° C., or both.

Another aspect of the teachings herein is directed at a sound damping article, wherein the sound damping article is formed of a composite material, the sound damping article is configured for attaching to a casting, the composite material includes a metallic layer (preferably two or more metallic layers) and a surface layer including an elastomer and glass or ceramic beads, wherein the sound damping article results in a reduction in the maximum value of the noise transfer function in the frequency range of 400 Hz to 800 Hz by about 10 dB or more at one or more of the following temperatures: about 20° C., about 50° C., about 60° C., about 70° C., about 80° C., or about 90° C.

Another aspect according to the teachings herein is directed at a device including a metal casting and a sound damping article (preferably a sound dampening article as described herein), wherein a surface layer of the sound damping article contacts a surface of the metal casting.

This aspect of the teachings may be further characterized by one or any combinations of the following: the surface layer includes a elastomer; the surface layer has a textured surface; the surface layer includes glass or ceramic beads; the sound damping article is attached to the metal casting with a plurality of spaced apart attachment components (e.g., bolts, screws, or other connectors); the sound damping article is attached to an outer surface of the casting; the sound damping article is attached to an inner surface of the casting (preferably wherein the sound damping article is hidden by the casting); about 70 percent or more of a face surface of the surface layer of the sound damping article applies pressure directly to the casting; the surface of the casting in contact with the sound damping article is a painted or unpainted; the sound damping article has a generally flat, planar configuration (preferably wherein the sound damping article is cut from a blank and/or is attached to the casting without a forming step); the casting is an inverter cover, a power train component, or an oil pan; the surface layer of the sound damping article conforms to a surface of the casting and/or applies pressure to the surface of the casting; the surface of the casting is a surface that is an as-cast surface (i.e., without machining); the sound dampening article is a generally planar article; the surface of the casting is a rough surface (e.g., having an RAof about 3 μm or more, about 5 μm or more, about 10 μm or more, or about 20 μm or more); the face surfaces of the sound dampening article are generally planar.

Another aspect according to the teachings herein is the use of a sound damping article (such as described herein) for an automotive application or for a non-automotive application.

Another aspect according to the teachings herein is directed at a method of forming the sound damping article (preferably a sound damping article according to the teachings herein) comprising a step of: coating a surface of one of the metallic layers with a composition including an elastomer and glass or ceramic beads in a carrier fluid; and removing at least a portion of the carrier fluid. The method may include a step of at least partially cross-linking the elastomer (e.g., for increasing a molecular weight of the elastomer, for forming long chain or short chain branches, for increasing the viscosity of the elastomer, for forming a network structure, or any combination thereof).

DETAILED DESCRIPTION

The sound damping articles according to the teachings herein are composite materials including at least one metallic layer and a surface layer including an elastomer. The composite material preferably includes two or more metallic layers. As illustrated inFIG.1, the composite material10may include a first metallic layer20and a second metallic layer22. The first metallic layer preferably is an outer layer of the composite. The composite material10includes a surface layer40that includes an elastomer. The surface layer is an outer layer of the composite material. In use, the surface layer will typically contact a casting. The composite material preferably includes a core layer30interposed between the first metallic layer and the second metallic layer.

Metallic Layer

The composite material of the sound damping article includes two or more metallic layers. The metallic layers assist in applying a compressive force to the surface of the casting. The metallic layers may be formed of the same or different metal layers. If the thickness of the metallic layers (individually or combined) is too high, the sound damping article will heavy and costly. If the thickness of the metallic layers is too low, there may be insufficient compressive force between the surface layer of the sound damping article and the casting and the sound damping properties will be lacking.

The first metallic layer and the second metallic layers preferably are formed from metallic sheets. The metallic sheets preferably are provided as rolls so that a roll of the composite material can be produced. The first metallic layer and the second metallic layer may have the same thickness or may have different thickness. Preferably a ratio of the thickness of the two metallic layer (i.e., the thinnest metallic layer to the thickest metallic layer) is about 0.1 or more, about 0.2 or more, about 0.4 or more, about 0.50 or more, about 0.75 or more, about 0.8 or more, or about 0.90 or more. A ratio of the thickness of the two metallic layers may be about 1.00 or less. It will be appreciated that in some applications it may be desirable for the first metallic layer (e.g., on the inner side of the tube) to have a wall thickness greater than the wall thickness of the second metallic layer (e.g., on the outer side of the tube). In other applications, it may be desirable for the second metallic layer to have a wall thickness greater than a wall thickness of the first metallic layer. Preferably, the total thickness of the first and second metallic layers is about 0.30 mm or more, more preferably about 0.40 mm or more, even more preferably about 0.50 mm or more, even more preferably about 0.65 mm or more, and most preferably about 0.80 mm or more. The total thickness of the first and second metallic layers preferably is about 7.0 mm or less, more preferably about 5.0 mm or less, even more preferably about 3.0 mm or less, even more preferably about 1.8 mm or less, and most preferably about 1.3 mm or less.

One of the metallic layer (e.g., the first metallic layer or first metal sheet) preferably is an outer layer of the sound damping article. In use, this metallic layer typically is positioned away from the casting. The other metallic layer (e.g., the second metallic layer or the second metal sheet) preferably is interposed between the core layer and the surface layer. The composite materials according to the teachings herein preferably includes at least the first metallic layer, the second metallic layer, the core layer, and the surface layer. Although the composite material may include one or more additional layers, the use of the core layer, the surface layer and the metallic layers, may eliminate the need any other layers.

The metal layers may have one or more surfaces plated or coated (e.g., with a thin film), or having one or more other surface treatment (e.g., a treatment that cleans, etches, roughens, or chemically modifies a surface). A metal face may have one or more coatings, platings or surface treatments that improves the adhesion of a filled polymeric material to the metal layer. The metal layers may have one or more surfaces plated, coated or otherwise treated that provides corrosion resistance, improves adhesion to a paint or primer, improves stiffness, or any combination thereof. Exemplary coatings and platings may include one or any combination of galvanized, electrogalvanized, chrome plating, nickel plating, corrosion resistance treatment, e-coat, zinc coated, Granocoat, Bonazinc and the like. It will be appreciated that one or more coatings, platings, or surface treatments may be performed on the composite material, (e.g., after the composite material is prepared). As such, a surface of the metal layer facing the filled polymeric layer may be free of a coating, plating or surface treatment and an exposed surface of the metal layer may have a coating, plating or surface treatment. One or both metal faces may be free of a coating, plating or surface treatment (for example, the filled polymeric material may be treated or selected so that it provides good adhesion to the metal layer without the need for a coating, plating, or surface treatment).

Core Layer

The core layer(s) provides a separation between the two metallic layers. The core layer, preferably reduces or eliminates transmission of sound and/or heat between the two metallic layers. The core layer preferably includes one or more non-metallic material. The amount of non-metallic material in the core layer may be about 50 volume percent or more, about 70 volume percent or more, 80 volume percent or more, about 90 volume percent or more, or about 95 volume percent or more, based on the total volume of the core layer. The amount of non-metallic material in the core layer may be about 100 volume percent or less, or about 99 volume percent or less. Examples of materials that may be employed in the core layer include polymers, oligomers, cross-linkable and/or polymerizable compounds, glasses, ceramic materials, woven or non-woven fabrics, organic materials, clays, mineral fillers, or any combination thereof. The core layer preferably includes a polymer or other viscoelastic material capable of absorbing sound, reducing or preventing the transfer of sound, or both.

The core layer(s) preferably fills a substantial amount of the space between the first and second metallic layers. Preferably the core layer material fills about 30% or more of the volume, more preferably about 50% or more of the volume, even more preferably about 75% or more of the volume, even more preferably about 90% or more of the volume, and most preferably about 95% or more of the volume between the first and second metallic layers. The amount of any voids in the core layer and/or between the metallic layers may be about 70 volume percent or less, about 50 volume percent or less, about 25 volume percent or less, about 10 volume percent or less or about 5 volume percent or less, based on the total volume between the first and second metallic layers.

The thickness of the core layer preferably is about 0.50 mm or less, more preferably about 0.25 mm or less, even more preferably about 0.15 mm or less, even more preferably about 0.10 mm or less, even more preferably about 0.07 mm or less, and most preferably about 0.05 mm or less. The thickness of the core layer preferably is about 0.005 mm or more, about 0.010 mm or more, about 0.015 mm or more, about 0.020 mm or more, or about 0.025 mm or more.

Materials for the Core Layer

The core layer(s) may include or be formed of a polymeric material (i.e., polymeric composition) that includes, consists essentially of, or consists entirely of one or more polymers. Preferably, the amount of the polymer in the core layer is about 30 weight percent or more, more preferably about 50 weight percent or more, even more preferably about 80 weight percent or more, and most preferably about 90 weight percent, based on the total weight of the core layer and/or based on the total weight of the polymeric composition. The core layer preferably includes one or more polymers having a generally low hardness. As used herein, polymer having a generally low hardness may be characterized by a Shore A durometer (measured according to ASTM D2240) of about 90 Shore A or less, preferably about 75 Shore A or less, and more preferably about 65 Shore A or less). Preferably the core layer includes a polymer having a hardness of about 10 Shore A or more (e.g., about 20 Shore A or more, or about 30 Shore A or more). The polymer of the core lay may have a crystallinity (e.g., as measured by differential scanning calorimetry according to ASTM D3418) of about 60% or less, about 50% or less, about 40% or less, about 30% or less, about 20% or less, or about 10% or less. For example, the polymer may be a generally amorphous polymer having a crystallinity of about 5% or less or about 0%. The core layer may include a filler at a concentration of 3 wt. % or more, or may be substantially free (i.e., a filler concentration of less than 3 weight percent, or about 1 weight percent or less) or may be entirely free of filler. The polymeric material of the core layer preferably includes an elastomeric material. A particularly preferred elastomeric material is an acrylic elastomer. The polymeric material (i.e., the polymeric composition of the core layer) may be formed from a composition that includes one or more components for cross-linking an elastomer. For example, the polymeric material may include a cross-linking agent, a cross-linking activator, a cross-linking accelerator, or any combination thereof. As such, the polymeric material may include a cross-linked elastomer. The polymeric material may include a generally high molecular weight polymer (e.g., having a molecular weight of about 30,000 or more, about 80,000 or more, or about 200,000 or more). The polymeric material may be selected to provide adhesion to the first and/or second metallic layers and/or an adhesive or other bonding agent may be employed for improving adhesion between the polymeric material and a metallic layer.

The multi-layer composite and/or the sound damping article preferably has a uniform thickness (except for the textured surface of the surface layer). For example, a large portion (e.g., 60% or more, 70% or more, 80% or more, 90% or more, or about 100%) of the composite may have a thickness, t, that is within a range of t1≤t≤t2, where (i) the ratio of t2/t1 is about 1.50 or less, about 1.40 or less, about 1.30 or less, about 1.20 or less, about 1.10 or less, or about 1.05 or less and/or the difference between t2−t1 is about 0.30 mm or less, about 0.20 mm or less, about 0.15 mm or less, about 0.10 mm or less, about 0.07 mm or less, about 0.05 mm or less, about 0.03 mm or less, about 0.02 mm or less, or about 0.01 mm or less. The ratio of t2/t1 may be about 1.00 or more and/or the of t2-t1 may be about 0.00 or more.

The surface layer may be smooth or may be a rough surface layer. The surface layer preferably is configured and/or arranged for contacting the casting. The surface layer preferably has a rough surface.

The surface layer includes an elastomeric composition having a glass transition temperature of about 10° C. or less, a crystallinity of about 5 percent or less at 23° C., or both. Preferably the elastomeric composition includes one or more elastomers. The elastomer may be any elastomer having a low glass transition temperature and/or low crystallinity. Without limitation, the elastomer may be an ethylene copolymer (e.g., having a comonomer that is an olefin and/or a comonomer that includes one or more heteroatoms), a polyisoprene, a polybutadiene, an ethylene propylene diene rubber, a silicone elastomer, a fluoroelastomer, a natural rubber, a styrene-butadiene block copolymer, a polyurethane elastomer, an polyacrylic rubber, an epichlorohydrin rubber, polyether block amide, an ethylene-vinyl acetate rubber, a chloroprene rubber, a halogenated butyl rubber, a hydrogenated nitrile rubber, a nitrile rubber, a copolymer thereof, or any combination thereof. The elastomer preferably is free of any melting temperature or glass transition temperature of about 35° C. or more (preferably about 20° C. or more, and more preferably about ° C. or more). The elastomer preferably has a hardness (i.e., durometer) of about 90 Shore A or less (as measured according to ASTM D 2240) at a temperature of about 20° C., preferably the elastomer has a hardness of about 80 Shore A or less, about 70 Shore A or less, about 60 Shore A or less, about 50 Shore A or less, or about 40 Shore A or less.

The elastomeric layer may include one or more fillers. Preferably the elastomeric layer includes glass or ceramic beads. The glass or ceramic beads may be solid or hollow. Preferably the elastomeric layer includes beads that are hollow. The beads may have an average specific gravity of about 0.10 or more, about 0.20 or more, about 0.30 or more, about 0.40 or more, about 0.50 or more, about 0.60 or more about 0.70 or more, or about 0.75 or more. The beads may have an average specific gravity of about 3.0 or less, about 2.2 or less, about 2.0 or less, about 1.7 or less, about 1.4 or less, about 1.1 or less, about 1.0 or less, about 0.90 or less, or about 0.80 or less. The glass or ceramic beads may have a narrow size distribution (e.g., a ratio of the weight average diameter to the number average diameter is about 2.0 or less, about 1.80 or less, about 1.60 or less, about 1.40 or less, about 1.20 or less, or about 1.10 or less). In one preferred aspect, the beads (e.g., the glass or ceramic beads) have a broad size distribution (e.g., a ratio of the weight average diameter to the number average diameter is more than about 2.0, about 2.5 or more, about 3.0 or more, about 4.0 or more, about 5.0 or more, about 7.0 or more, or about 9.0 or more). In particular, it may be advantageous to choose the filler so that a portion of the filler has a diameter that is equal to or less than the average thickness of the surface layer and a portion of the filler has a diameter that is greater than the average thickness of the surface layer. As such, the filler may contribute to or provide a desired texture or surface roughness to the surface layer. Preferably the amount of the filler that has a diameter greater than the average thickness of the surface layer is about 3 volume percent or more, more preferably about 5 volume percent or more, even more preferably about 10 volume percent or more, and most preferably about 20 volume percent or more. Preferably the amount of the filler that has a diameter greater than the average thickness of the surface layer is about 80 volume percent or less, more preferably about 65 volume percent or less, even more preferably about 50 volume percent or less, and most preferably about 40 volume percent or less.

The concentration of the one or more fillers (e.g., beads) in the surface layer may be about 5 volume percent or more, about 10 volume percent or more about 20 volume percent or more, about 30 volume percent or more, or about 40 volume percent or more and/or about 70 volume percent or less, or about 60 volume percent or less, based on the total volume of the surface layer. A ratio of a thickness of the surface layer to a maximum diameter or average diameter (e.g., weight average diameter or number average diameter) of the filler (e.g., the glass or ceramic beads or hollow beads) preferably is about 10 or less, about 7 or less, about 5 or less, about 3 or less, about 2 or less about 1.6 or less, about 1.4 or less, about 1.3 or less, about 1.2 or less, about 1.1 or less about 1.0 or less and/or about 0.20 or more, about 030 or more, about 0.40 or more, about 0.50 or more, about 0.60 or more, about 0.75 or more, or about 0.9 or more.

A ratio of the specific gravity of the elastomer to a specific gravity of the filler (e.g., glass or ceramic beads or hollow beads) preferably is about 0.20 or more about 0.35 or more, about 0.50 or more, about 0.60 or more, about 0.70 or more, or about 0.75 or more and/or about 3.0 or less, about 2.0 or less, about 1.60 or less, about 1.50 or less, about 1.40 or less, about 1.30 or less, or about 1.25 or less.

The elastomeric layer may include one or more additives for curing or cross-linking the elastomer. For example, the elastomeric layer may include a curative or other cross-linking agent, a cure accelerator, a cure initiator, or any combination thereof.

The composite material, when contacted with a casting, reduces noise from the casting. Preferably the acoustical damping performance is characterized by a reduction in the noise transfer function, such that the maximum noise transfer function in the 400 Hz to 800 Hz range is reduced by about 6 dB or more, preferably reduced by about 8 dB or more, even more preferably reduced by about 10 dB or more, even more preferably reduced by about 12 dB or more, and most preferably reduced by about 14 dB or more. The noise transfer function may be measured as a spatial average noise transfer function. In the 400 Hz to 800 Hz range, a primary vibration mode may be evident. The reduction in NTF at higher modes may be about 3 dB or more, about 4 dB or more, about 6 dB or more, about 8 dB or more, or about 9 dB or more. The reduction in NTF preferably is maintained at temperatures of about 50° C. to about 90° C. (e.g., at about 50° C., about 60° C., about 70° C., about 80° C., or about 90° C. The reduction in NTF preferably is maintained at temperatures of about 20° C.

Coefficient of Friction

The core layer and/or the surface layer (i.e., damping surface) preferably are dense materials having little or no voids. Preferably the core layer has a void concentration of about 20 volume percent or less, about 10 volume percent or less, about 4 volume percent or less, about 2 volume percent or less, about 1 volume percent or less, about 0.5 volume percent or less, or about 0 volume percent, based on the total volume of the core layer. Preferably the surface layer has a void concentration of about 20 volume percent or less, about 10 volume percent or less, about 4 volume percent or less, about 2 volume percent or less, about 1 volume percent or less, about 0.5 volume percent or less, or about 0 volume percent, based on the total volume of the surface layer.

The composite material (e.g., sound damping component) may be used to reduce sound transmitted from a casting. Preferably, the composite material is attached to the casting with the surface layer (i.e., damping surface) facing the casting. The surface layer preferably directly contacts the casting. The composite material may be attached to the casting using a plurality of attachment components that provide a compressive force between the composite material and the casting. Preferably attachment components are spaced apart and/or present in sufficient number so that a large portion of the surface area of the surface layer contacts the casting. For example, the percentage of the surface area of the surface layer that contacts (e.g., compressively contacts) the casting is about 30% or more, about 40% or more, about 50% or more, about 60% or more, about 70% or more, about 80% or more, or about 90% or more, based on the total surface are of the surface layer facing the casting. The percentage of the surface area of the surface layer that contacts (e.g., compressively contacts) the casting may be about 100% or less. The area of contact (e.g., compressive contact) between the surface layer and the casting may be measured using a pressure sensitive paper (e.g., FUJIFILM PRESCALE® pressure sensitive paper).

With reference toFIG.2, the sound damping article may include spaced apart attachment components or features16,18. The sound damping article may include attachment components or attachment features16positioned near a periphery region12of the sound damping article. The sound damping article may include attachment components or attachment features18positioned near a central region14of the sound damping article.

The sound damping article may have a generally planar shape, such as illustrated inFIG.1.

The composite material and sound damping articles according to the teachings herein maintain good performance even after exposure to oils, transmission fluid, alkaline cleaners, acidic environments, or combination thereof.

General Information Applicable to the Teachings

The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. The term “consisting essentially of” to describe a combination shall include the elements, ingredients, components or steps identified, and such other elements ingredients, components or steps that do not materially affect the basic and novel characteristics of the combination. The use of the terms “comprising” or “including” to describe combinations of elements, ingredients, components or steps herein also contemplates embodiments that consist essentially of, or even consisting of, the elements, ingredients, components or steps.

Relative positional relationships of elements depicted in the drawings are part of the teachings herein, even if not verbally described. Further, geometries shown in the drawings (though not intended to be limiting) are also within the scope of the teachings, even if not verbally described.

Examples

A composite sound damping article is prepared with a polymeric core layer (thickness of about 0.03 mm) between two layers of galvanized cold rolled steel (thickness of about 0.050 mm each). The composite includes a surface layer of an elastomeric composition directly attached to one of layers of galvanized CRS. The surface layer has a textured outer surface for contacting with a casting. The total thickness is about 1.11 mm. The elastomer in the surface layer is heated and cross-linked. The elastomeric composition includes ceramic beads having a. The areal density of the composite material is about 1.82 lbs/ft2.

Acoustical damping performance is measured (at room temperature of about 20° C.) for a bare casting (without the sound damping article) and with the composite material attached. The sound damping article is attached to casting using spaced apart bolts with the surface layer directly contacting the casting. The bolts are tightened to a predetermined torque. Pressure sensitive paper shows that the entire surface of the sound damping article applies pressure to the casting. The acoustical performance is shown inFIG.3. Without the sound damping article, the casting has a maximum noise transfer function of about 91 dB in the frequency range of 400 to 800 Hz. With the sound dampening article attached to the casting, the maximum of the noise transfer function in the range of 400 to 800 Hz is about 75 dB. The reduction in the maximum NTF is about 16 dB. At higher frequency modes, the reduction in the NTF is about 10 dB.

The acoustical dampening performance is measured at a temperature of about 50° C. and similar reductions in the NTF are expected. The acoustical dampening performance is measured at a temperature of about 60° C. and similar reductions in the NTF are expected. The acoustical dampening performance is measured at a temperature of about 70° C. and similar reductions in the NTF are expected. The acoustical dampening performance is measured at a temperature of about 80° C. and similar reductions in the NTF are expected. The acoustical dampening performance is measured at a temperature of about 90° C. and similar reductions in the NTF are expected.

The composite material is expected to have a peel resistance of about 2.6 N/mm or more and/or a shear resistance of about 2.4 MPa or more.

The composite material is expected to have good resistance to oils, transmission fluid, alkaline cleaners, acidic environments, or any combination thereof.

The composite material, after heating to 110° C. for about 1006 hours, is expected to have no signs of delamination or loss of sound damping performance.

The concentration of voids in the core layer is expected to be about 1 volume percent or less.

The concentration of any voids in the surface layer is expected to be about 1 volume percent or less.