WO2012092093A1

WO2012092093A1 - Noise damping compositions

Info

Publication number: WO2012092093A1
Application number: PCT/US2011/066696
Authority: WO
Inventors: Yinjuan WANG; Feng Wang
Original assignee: E. I. Du Pont De Nemours And Company
Priority date: 2010-12-27
Filing date: 2011-12-22
Publication date: 2012-07-05
Also published as: JP2014501322A; CN102558840A; CN102558840B; KR20130132961A

Abstract

Disclosed are thermoplastic compositions having excellent vibration damping and noise suppression properties and molded articles made therefrom that can be manufactured inexpensively. The noise damping compositions of the present invention being (a) about 50-85 weight % of a polyamide; (b) about 5-45 weight % of a fibrous reinforcing agent; (c) about 1-25 weight % of zinc oxide; and (d) about 0-15 weight % of other additive; wherein the weight % is based on the total weight of the noise damping composition, and provided that the composition has essentially no flame retardants.

Description

TITLE

NOISE DAMPING COMPOSITIONS

This application claims the benefit of Chinese Patent Application No. 201010624765.4, filed December 27, 2010 which is herein

incorporated by reference.

FIELD OF THE INVENTION

This invention relates to thermoplastic compositions having improved vibration damping and noise reduction properties. The invention is particular useful as components in damping noise generated within the powertrain system in transportation vehicles. The invention also relates to noise-damping articles molded from such compositions.

BACKGROUND OF THE INVENTION

Fiber reinforced composites have been attractive lightweight substitutes for metals when high specific stiffness, strength and controlled expansion are required. These composites have been particularly effective for applications in commercial transportation systems. Although the tailorability of composites provides an effective means for design optimization of components which must be lightweight and must meet stressing thermal and mechanical systems requirements, these structures nevertheless experience undesirable levels of vibration and noise. For example, vehicle engine noise transmitted to the passenger compartment of the vehicle contributes to rider discomfort.

A normal human ear is able to hear sounds with frequencies from 20 Hz to 20,000 Hz. Nonetheless, the response of the ear to sound is very dependent on the frequency content of the sound. The human ear has peak response around 2,500 to 3,000 Hz and has a relatively low response at low frequencies. The audible sound pressure range for human ear is from 0 dB to 120 dB. The noise heard by people in the passenger compartment of an automobile originates basically from: (a) the powertrain system including the engine, the transmission system and accessories ; (b) road excitation, and (c) aerodynamic excitation. While a subjective rating of noise inside vehicles are as follows: when noise level not exceeding 67 dB is considered as "quiet", 73 dB as "noticeable", and 79B as "intrusive", because the dB is the log scale of the sound pressure level, 1 dB reduction in noise level means 1/10 of the sound pressure level. In order to reduce the noise level inside the passenger

compartment, the interior has to be well isolated from road and wind noise, and have subdued powertrain noise levels.

Vibration frequencies which typically are produced by the powertrain system are in the low frequency range, typically around 500 Hz to 3,000 Hz. In an effort to reduce the powertrain noise levels, a variety of techniques have been employed, including the use of polymer coatings on engine parts, sound absorbing barriers, and laminated panels having viscoelastic layers. Other noise reducing efforts have included the use of noise reducing engine mount designs, including active engine mounts that employ magneto-rheological fluid actuators.

The use of laminated panels having viscoelastic layers has resulted in a modest damping of vibration and noise, of a value generally less than 5%. Another disadvantage of this approach is in the considerable weight added to the underlying structure, perhaps as much as 20-30%.

Thermoplastic resins that have good sound damping properties by blending with a viscoelastic elastomer generally have insufficient rigidity, modulus strength, or high temperature tolerance to be useful in many applications such as oil pan, or the like.

US 6,849,684 to Poppe et al, discloses a blend of a soft

thermoplastic copolyether ester elastomer and a hard polyester resin reinforced with a fibrous filler, i.e. carbon fiber.

In summary, while existing noise reducing efforts may have a positive effect on reducing the transmission of noise to the passenger

compartment, there remains a need for a thermoplastic composition having excellent vibration damping and noise suppression properties and that can be manufactured inexpensively.

SUMMARY OF THE INVENTION

This invention provides a noise damping composition comprising a mixture of: (a) about 50-85 weight % of a polyamide;

(b) about 5-45 weight % of a fibrous reinforcing agent;

(c) about 1 -25 weight % of zinc oxide; and

(d) about 0-15 weight % of other additive;

wherein the weight % is based on the total weight of the noise damping composition, and

provided that the composition comprises essentially no flame retardants.

In one embodiment, in the noise damping composition of the present invention, the polyamide is selected from the group consisting of nylon 66, nylon 6, nylon 66/6, nylon 46, nylon1010, nylon 10, nylon 12, nylon 1212, nylon 610, nylon 612, nylon 66/6T, nylon 6T/DT, nylon MXD-6, and blends thereof.

In one embodiment, in the noise damping composition of the present invention, the polyamide is nylon 66, nylon 6, nylon 66/6, or a blend thereof; and the amount of the polyamide ranges from about 50 to 75 weight %, based on the total weight of the noise damping composition.

In one embodiment, in the noise damping composition of the present invention, the fibrous reinforcing agent is glass fiber, carbon fiber, or para- aramid fiber.

In one embodiment, in the noise damping composition of the present invention, the fibrous reinforcing agent is glass fiber, and amount of the fibrous reinforcing agent ranges from about 20 to 40 weight %, based on the total weight of the noise damping composition.

In one embodiment, in the noise damping composition of the present invention, the weight ratio between the polyamide and the fibrous reinforcing agent ranges from about 50:50 to 95:5.

In one embodiment, in the noise damping composition of the present invention, the zinc oxide is nano-zinc oxide or zinc oxide whisker, and the amount of zinc oxide ranges from about 5 to 10 weight % based on the total weight of the noise damping composition.

In one embodiment, in the noise damping composition of the present invention, the zinc oxide is nano-zinc oxide having a particle size ranging from about 5 to 100 nm, preferably, from about 10 to 60 nm. In one embodiment, in the noise damping composition of the present invention, the zinc oxide is zinc oxide whisker and has a size in the micrometer range.

In one embodiment, in the noise damping composition of the present invention, the zinc oxide is tetrapod-shaped zinc oxide whisker, and is not been surface treated with silane coupling agent.

In one embodiment, in the noise damping composition of the present invention, the amount of zinc oxide ranges from about 5 to 10 weight % based on the total weight of the noise damping composition.

In one embodiment, in the noise damping composition of the present invention, the other additive is selected from the group consisting of antioxidants, thermal stabilizers, ultraviolet light stabilizers, colorants including dyes and pigments, lubricants, hydrolysis resistants, demolding agents, minerals, mica, flow modifiers, and chain extenders.

This invention also provides a molded article comprising or produced from the noise damping composition of present invention.

In one embodiment, the molded article of the present invention is a noise-damping part of a transportation vehicle, wherein the transportation vehicle is an automobile, an airplane or a boat. In one embodiment, the molded article of the present invention is selected from the group

consisting of parts used in the transmission system such as bearing carrier, transmission cover assembly, and transmission housing; parts used in the intake and exhaust devices such as air duct, housings of air cleaner, air intake manifolds, exhaust manifolds, exhaust muffler, EGR housing, exhaust pipes, and housing of three-way catalytic converter; parts used in the cooling system such as shields, reservoir caps, radiator end tanks, intercooler tanks, charged air cooler, and thermostat housing; parts used in the engine system such as engine covers, engine mounts, oil reservoir tanks, oil pans, oil buffer, oil strainers, cylinder head cover, timing belt cover, hinged clips, binding bands, and electrical motor bracket or housing; parts used in the electronic fuel injection system such as gasoline tanks, gasoline sub-tanks, oil reservoir tanks, fuel delivery modulus, fuel delivery pipes, oil strainers, canisters, junction blocks, resonators, relay blocks, connectors, corrugated tubes, and protectors; parts used in the body such engine front cover and rear cover.

In another embodiment, the molded article of the present invention is a noise-damping part selected from the group consisting of a power tool, an electrical motor, and a home appliance including washing machine, air conditioning, air fan, microwave oven, refrigerator, and freezer.

This invention further provides use of the molded article of the present invention as noise-damping parts in transportation vehicles.

The noise damping compositions of the present invention possess excellent vibration damping and noise suppression properties and that can be manufactured inexpensively. Additionally, the inventive compositions still posses high mechanical strength and high temperature tolerance which make them suitable for applications that have working temperature higher than 150°C. The noise-damping articles molded from the inventive compositions are particular useful as parts in damping noise generated within the powertrain system in transportation vehicles.

Various other features, aspects, and advantages of the present invention will become more apparent with reference to the following description, examples, and appended claims.

DETAILS OF THE INVENTION

All publications, patent applications, patents and other references mentioned herein, if not otherwise indicated, are explicitly incorporated by reference herein in their entirety for all purposes as if fully set forth.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

Unless stated otherwise, all percentages, parts, ratios, etc., are by weight.

As used herein, the term "produced from" is synonymous to

"comprising". As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains" or "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

The transitional phrase "consisting of" excludes any element, step, or ingredient not specified. If in the claim, such a phrase would close the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase "consisting of appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

The transitional phrase "consisting essentially of is used to define a composition, method or apparatus that includes materials, steps, features, components, or elements, in addition to those literally discussed, provided that theses additional materials, steps features, components, or elements do not materially affect the basic and novel characteristic(s) of the claimed invention. The term "consisting essentially of occupies a middle ground between "comprising" and "consisting of.

The transitional phrase "essentially no" components or "essentially free" of components, it is meant that the compositions of the invention should contain less than 1 % by weight, preferably zero percent by weight, of the components, based on the total weight of the noise damping compositions.

The term "comprising" is intended to include embodiments

encompassed by the terms "consisting essentially of and "consisting of. Similarly, the term "consisting essentially of is intended to include embodiments encompassed by the term "consisting of.

When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is recited, the recited range should be construed as including ranges "1 to 4", "1 to 3", "1 -2", "1 -2 & 4-5", "1 -3 & 5", and the like. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range.

When the term "about" is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to.

Further, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not to an exclusive "or". For example, a condition A "or" B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Also, the indefinite articles "a" and "an" preceding an element or component of the invention are intended to be nonrestrictive regarding the number of instances (i.e. occurrences) of the element or component.

Therefore "a" or "an" should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

In describing and/or claiming this invention, the term "homopolymer" refers to a polymer derived from polymerization of one species of monomer; "copolymer" refers to a polymer derived from polymerization of two or more species of monomers. Such copolymers include dipolymers, terpolymers or higher order copolymers.

In describing certain polymers it should be understood that sometimes applicants are referring to the polymers by the monomers used to produce them or the amounts of the monomers used to produce the polymers. While such a description may not include the specific

nomenclature used to describe the final polymer or may not contain product-by-process terminology, any such reference to monomers and amounts should be interpreted to mean that the polymer comprises those monomers (i.e. copolymerized units of those monomers) or that amount of the monomers, and the corresponding polymers and compositions thereof. In this invention, the term "flame retardant" refers to commonly known flame retardants, which include halogen-containing flame retardants consisting of tetrabromo-bisphenol A (TBBA),

tetrabromophthalic acid anhydride (TBPA), tetrabromobisphenol A bis(dibromopropyl ether) (BDDP), hexabromocyclododecane (HBCD), decabromodiphenyl ether (DBDE), 1 ,2-bis(pentabromophenyl)ethane (DBPE), tris(2,3-dibromopropyl) isocyanurate (TBC),

dodecachloropentacyclooctadecadiene, and chlorinated paraffins;

inorganic flame retardants consisting of magnesium hydroxide, aluminum hydroxide, antimony oxide, and zinc borate; phosphorus-containing flame retardants consisting of resorcinol bis(diphenyl phosphate) (RDP), bisphenol-A bis(diphenyl phosphate) (BDP), resorcinol bis(2,6-dixylenyl phosphate) (RDX), diphenyl isopropylphenyl phosphate (IPPP), triphenyl phosphate (TPP), dimethyl methylphosphonate (DMMP), tris(2-chloro-1 - methyl-ethyl)phosphate (TCPP), tris(2-chloro-1 -

(chloromethyl)ethyl)phosphate (TDCPP), red phosphorus, ammonium polyphosphate (APP), and melamine polyphosphate(MPP); and other flame retardants consisting of melamine (MA) and melamine cyanurate (MC).

Embodiments of the present invention as described in the Summary of the Invention include any other embodiments described herein, can be combined in any manner, and the descriptions of variables in the embodiments pertain to the noise damping compositions of the present invention and molded articles made therefrom.

The materials, methods, and examples herein are illustrative only and, except as specifically stated, are not intended to be limiting.

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

The invention is described in detail hereinunder.

(a) Polvamide

Molded products produced from thermoplastic resins such as polyamides have been frequently used for under-hood parts for automobiles due to their high heat resistance (e.g., nylon-66) and/or high toughness (e.g., nylon-6).

Polyamides serve as the base resin for the present noise damping composition. Any polyamides produced from lactams or amino acids, known to one skilled in the art, can be used.

Polyamides derived from single reactants such as lactams, amino carboxylates, copolymers of these components referred as AB type polyamides are disclosed in Nylon Plastics (edited by Melvin L. Kohan, 1973, John Wiley and Sons, Inc.) and can include aliphatic polyamides such as nylon 6, nylon 1 1 (ροΐν-ω-undecanoannide), nylon 12 (poly-ω- dodecanoamide), and mixtures or copolymers thereof. Another type of well known polyamides prepared from condensation of diamines and diacids, referred to as AABB type polyamides including aliphatic

polyamides such as nylon 66, nylon 610 (polyhexamethylene

sebacamide), nylon 612 (polyhexamethylene dodecanamide), nylon 46 (polytetramethylene adipamide) and nylon 1212 (polydodecamethylene dodecanamide). Other non-aliphatic polyamides including nylon MXD-6 (poly(m-xylene adipamide)) , polyhexamethylene terephthalamide (nylon 6T), poly(2-methylpentamethylene terephthalamide) (nylon DT), poly(2- methylpentamethylene)terephthalamide (nylon MST), polyhexamethylene isophthalamide (nylon 6I) or poly(2-methylpentamethylene)- isophthalamide (nylon M5I) may be suitable.

Examples of polyamide copolymers include nylon 66/6, nylon 66/610, nylon 66/6T, nylon 66/61, nylon 6T/DT, nylon 6T/6I/66, nylon 6T/6I/610, nylon 6T/6I, andnylon 6T/MST.

Because polyamide and process therefor are well known to one skilled in the art, the disclosure of which is omitted herein for the interest of brevity.

In one embodiment, the polyamides suitable for use in the present invention includes nylon 66, nylon 6, nylon 66/6, nylon 46, nylon1010, nylon 10, nylon 12, nylon 1212, nylon 610, nylon 612, nylon 66/6T, nylon 6T/DT, nylon MXD-6, and blends thereof. In a preferred embodiment, the polyamide of the invention is nylon 66, nylon 6, nylon 6/66, or a blend thereof.

Polyamides based on a blend of nylon 66, and nylon 6 may be useful if the presence of nylon 6 is less than 40 wt %.

Among the above-mentioned polyamide resins, those having a number-average molecular weight of about 7,000 to 30,000 are preferably used in the present invention.

The amount of polyamide employed in the noise damping

composition of the present invention ranges from about 50 to 85 weight %, preferably from about 50 to 75 weight %, more preferably from about 55 to 70 weight %, based on the total weight of the noise damping composition.

(b) Fibrous Reinforcing Agent

To the noise damping composition used in the present invention, a fibrous reinforcing agent is added in order to improve the mechanical strength such as tensile strength, flexural strength, and to suppress the shrinkage of the molded product.

Examples of the fibrous reinforcing agent include: inorganic fiber such as glass fiber, carbon fiber, graphite fiber, silica-alumina fiber, zirconia fiber, ceramic fiber, metal fiber such as fiber of stainless steel, aluminum, titanium, copper, or brass; and organic fiber such as para- aramid fiber, meta-aramid fiber, fluorine resin fiber, or liquid crystalline aromatic fiber. One or two or more of them may be used or in combination thereof. In terms of reinforcing effect, the fibrous reinforcing agent is preferably glass fiber, carbon fiber or para-armid fiber such as Kevlar® fiber, available from DuPont Co., US. Considering availability and cost, glass fiber is more preferred.

In one embodiment, in the noise damping composition of the present invention, the fibrous reinforcing agent is glass fiber, carbon fiber, or para- aramid fiber. In another embodiment, in the noise damping composition of the present invention, the fibrous reinforcing agent is glass fiber.

As the glass fiber, there may be used those glass fibers ordinarily used for thermoplastic resins. Among these glass fibers, preferred are chopped strands produced from E-glass (alkali-free glass). The average fiber diameter of the fibrous reinforcing agent is not specifically limited, for example, is within the range of 1 to 100 μιτι, preferably about 3 to 30 μιτι, and more preferably about 5 to 15 μιτι. The mean fiber length of the fibrous reinforcing agent is also not specifically limited, and for example, is within the range of about 2 to 4 mm.

Examples of suitable glass fiber include NEG275H manufactured by Nippon Electric Glass Co., Ltd., and ChopVantage™ available from PPG Industries Fiber Glass. In addition, the fibrous reinforcing agent may be surface-treated, as necessary, through the use of a surface-treatment agent (such as functional compound including epoxy-based compound, acrylic-based compound, isocyanate-based compound, silane-based compound, or titanate-based compound). The fibrous reinforcing agent may be preliminary surface-treated by the surface-treatment agent described above, or may be surface-treated in preparing the material by the addition of the the surface-treatment agent. The glass fiber is preferably surface-treated with a silane-based compound (also known as silane coupling agent), in order to enhance adhesion to the polyamide resin.

The fibrous reinforcing agent may be blended in the polyamide resin at an optional stage from production (polycondensation) of the polyamide resin to molding thereof. The fibrous reinforcing agent is preferably charged into an extruder which is in the course of molding the polyamide resin, and melt-kneaded with the polyamide resin therein.

The amount of the fibrous reinforcing agent employed in the noise damping composition of the present invention ranges from about 5 to 45 weight %, preferably from about 20 to 40 weight %, more preferably from about 25 to 35 weight %, based on the total weight of the noise damping composition.

In the noise damping compositions of the present invention, the weight ratio between the polyamide and the fibrous reinforcing agent ranges from about 50:50 to 95:5; preferably, from about 55:45 to 85:15; more preferably, from about 60:40 to 80:20; and most preferably, from about 65:35 to 75:25. When the amount of the fibrous reinforcing agent is more than that of the polyamide (by weight), the resultant composition tends to be deteriorated in fluidity. (c) Zinc Oxide

Zinc oxide (ZnO) is a white crystalline material that has found use in many and various applications. The unique combination of properties of ZnO, namely that it is a transparent, UV absorbing, luminescent, piezoelectric, semi-conductive, wear-proof, microwave absorption, antibacterial, non-toxic and a low cost material, makes it technologically important. It is currently used in cosmetic sunscreens, varisters, white pigment in plastics and ink, semiconductor related application. See Pearton et al, "Recent progress in processing and properties of ZnO", Prog. Mater. Sci., Vol. 50, pp 293-340 (2005).

The Applicant discovered that the addition of ZnO to the polyamide matrix in the presence of a fibrous reinforcing agent provides compositions having improved vibration damping and noise reduction properties.

Therefore, the zinc oxide plays a critical role as a noise attenuator in the noise damping composition of the present invention. Without wishing to be bound by theory, it has been hypothesized that the damping effect of zinc oxide may be due to its piezoelectric property.

Preferably, the zinc oxide is a crystalline zinc oxide in needle, dendrite or wire shape. In the more preferred embodiment, the zinc oxide is nano-zinc oxide (N-ZnO) or zinc oxide whisker a e.g., tetrapod-shaped zinc oxide whisker (T-ZnOw).

Nano-zinc oxide or zinc oxide nanoparticle is known to improve the thermal stability of polyacrylates and polyethylene. See Cho et al, "Effects of ZnO Nano Particles on Thermal Stabilization of Polymers", Polym. Eng. Sci., Vol 44, pp 1702-1706 (2004). In order to maximize the benefits that nano-ZnO may bring to polymers, full dispersion of the nanoparticles within the polymeric matrix must be achieved. "Nanoparticles" are understood by the expert to be particles which, through suitable production processes, have mean particle sizes of 5 to 100 nm.

Zinc oxide whisker, e.g., T-ZnOw has a tetrapod shape in a micro- image and a porous appearance in bulk. Under a microscope, the zinc oxide crystal has four needle crystals extending from the central body. Each needle (or whisker) has a length of greater than 3 micrometers measuring from its basal part contacting the central body to the tip. The whiskers of the T-ZnOw are known to be flexible and have a high modules of elasticity and a very high specific density of about 5.8. T-ZnOw possess additional good properties compared to zinc oxide in other crystalline forms due to its peculiar shape such as high strength and high elasticity.

The zinc oxide similar to the fibrous reinforcing agent may be surface-treated, as necessary, through the use of a surface-treatment agent as described above. The zinc oxide may be preliminary surface- treated by a surface-treatment agent, or may be surface-treated in preparing the material by the addition of the surface-treatment agent. Nano-zinc oxide is preferably surface-treated with a silane-based compound (also known as silane coupling agent) in order to provide a good dispersion of the nanoparticles within the polymeric matrix. Zinc oxide whiskers are less prone to particulate aggregation and are preferably not surface-treated with a silane coupling agent.

In one embodiment, in the noise damping composition of the present invention, the zinc oxide is nano-zinc oxide or zinc oxide whisker.

In another embodiment, in the noise damping composition of the present invention, the zinc oxide is nano-zinc oxide having a particle size ranges from about 5 to 100 nm, preferably, from 10 to 60 nm.

In a further embodiment, in the noise damping composition of the present invention, the zinc oxide is zinc oxide whisker and has a size in the micrometer range. In one embodiment, in the noise damping composition of the present invention, the zinc oxide is a tetrapod-shaped zinc oxide whisker, and has not been surface treated with silane coupling agent.

The amount of the zinc oxide employed in the noise damping composition of the present invention ranges from about 1 to 25 weight %, preferably from about 5 to 10 weight %, based on the total weight of the noise damping composition.

(d) Other Additives

The noise damping composition of the present invention may further comprise small amounts of optional additives commonly used and well known in the polymer art. Examples of additives include without limitation antioxidants, thermal stabilizers, ultraviolet light stabilizers, colorants including dyes and pigments, lubricants, hydrolysis resistants, demolding agents, minerals, mica, flow modifiers, and chain extenders. These additive(s) may be present in the compositions in quantities that are generally from about 0.01 to about 15 weight %, preferably from about 0.01 to about 10 weight %, so long as they do not detract from the basic and novel characteristics of the composition and do not significantly adversely affect the performance of the composition.

As described above, the noise damping composition of the present invention may be formed into a desired shape by an optimal molding method such as injection-molding, a coinjection molding, a compression molding, overmolding, profile extrusion, blow-molding, vacuum forming, and form molding. For example, the noise damping composition of the present invention may be used in molded products used in automotive parts and parts for other transportation vehicles.

Specific examples of the applications of the noise damping

composition of the present invention may include parts or products related to automobile and other transportation vehicles such as airplane and boat. More specifically, molded parts for automobiles include parts used in the transmission system such as bearing carrier, transmission cover assembly, and transmission housing; parts used in the intake and exhaust devices such as air duct, housings of air cleaner, air intake manifolds, exhaust manifolds, exhaust muffler, EGR housing, exhaust pipes, and housing of three-way catalytic converter; parts used in the cooling system such as shields, reservoir caps, radiator end tanks, intercooler tanks, charged air cooler, and thermostat housing; parts used in the engine system such as engine covers, engine mounts, oil reservoir tanks, oil pans, oil buffer, oil strainers, cylinder head cover, timing belt cover, hinged clips, binding bands, and electrical motor bracket or housing; parts used in the electronic fuel injection system such as gasoline tanks, gasoline sub- tanks, oil reservoir tanks, fuel delivery modulus, fuel delivery pipes, oil strainers, canisters, junction blocks, resonators, relay blocks, connectors, corrugated tubes, and protectors; parts used in the body such engine front cover and rear cover.

Also, the invention may be applicable to products, such as steering knuckles, control arms, cast cradles, cast instrument panel beams, or any structural or closure casting. Also, the invention may benefit traction drive motors for hybrid electric and pure electric propulsion systems, as well as containment/housings for high voltage contactors.

Additionally, the noise damping composition of the present invention may include parts or products related to power tools, electrical motors, or home appliances including washing machine, air conditioning, air fan, microwave oven, refrigerator, and freezer.

Other potential applications include any structure which produces audible and objectionable noise in service, such as manufacturing machines, railroad equipment, passenger planes, etc. However, the invention seems particularly well suited for molded parts which house or enclose one or more rotating, noise-generating components of a transportation.

EXAMPLES

The abbreviation "E" stands for "Example" and "C" stands for

"Comparative Example" is followed by a number indicating in which example the composition is prepared. The examples and comparative examples were all prepared and tested in a similar manner. Percentages are by weight unless otherwise indicated.

Materials

PA1 : a polyamide 66 resin, manufactured under by DuPont Co. under the trade name of Zytel^®101 L NC010.

PA2: a polyamide 66 containing 35% by weight of reinforcing glass fibers, manufactured by DuPont under the trade name of Zytel®70G35 BK267.

PA3: a polyamide 6 containing 35% by weight of reinforcing glass fibers, manufactured by DuPont under the trade name of

Zytel®73G35 BK262.

N-ZnO: abbreviated for nano-zinc oxide having an average size of about 30 nm, surface modified with 2 wt% of KH570; purchased from Veking, Hanzhou, China. KH570 is a siliane coupling agent, 3-methacryloxypropyltrimethoxysilane (cas number

2530-85-0).

T-ZnOw: abbreviated for tetrapod-shaped ZnO whiskers, which has the needles or whiskers of at least 3 μηι long, typically 10-50 pm; purchased from Chengdu Crystrealm Co. Ltd. GF: a glass fiber filament of chopped strand, the fiber is about 2.75-

3.00 mm in length and a diameter about 10 μιτι, obtained from Nippon Electric Glass Co. Ltd. under the trade name of NEG 275H.

General Compounding Procedure for Working Examples and

Comparative Examples

The polyamides were dried at 80oC for 12 hour, and the zinc oxides were dried at 120oC for 12 hour. The ingredient amounts of each example according to Tables 1 -5 were fed to a twin screw extruder (Eurolab 16) to obtain the corresponding thermoplastic composition as pellets.

The temperature of the extruder was set to be

270/275/275/275/275/275/275/275/280/280°C for the extruder of 10 heating block configuration. The die temperature was 265-275°C and the screw speed was at 400-430 rpm. The polymer feeder speed was set as 2.45 Kg/hour and the zinc oxide feeder was set at 0.05 Kg/hour.

General Molding Procedure

The extruded pellets were dried to a moisture level of less than 40 ppm prior to molding. For mechanical property tests, multipurpose test specimen according to ISO3167 were molded on a Sumitomo 100 Ton molding machine with a screw diameter of 32 mm and 5 mm for the nozzle diameter. The barrel temperature was set to be 280°C and mold temperature was 100°C. The multipurpose test specimen has the basic dumbbell shape, 150 mm long, with the center section 10 mm wide by 4 mm thick by 80 mm long.

Test Methods

Damping loss factor (η): damping loss factor is a measurement of sound damping properties representing how much vibration related energy is absorbed by the material at a given temperature. The measurements were done by a Dynamic Mechanical Analyzer (manufactured by Perkin Elmer) at 150°C according the ASTM E756-05. Reported 3 data points at representative frequencies within the range of 500 Hz to 4000 Hz for a given sample to demonstrate the effectiveness in noise damping of the composition.

Transmission loss: the reduction in noise level resulting from passage through a test sample (a disk shape having diameter 100 mm, thickness 2 mm) at frequency ranging from 0-3200 Hz. The experiment setup involved in an acoustic room, using a speaker as the sound source, 2 microphones, one placed in front and the other at the back of the test sample to compare the difference of noise isolated by both microphones. Values are analyzed through 1 /3 octave band method and expressed in decibels and as such form a logarithmic scale. The higher the

transmission loss, the more effective the material is.

Tensile modulus was measured on universal material testing machine Instron 5567 according to ISO527:1993(E). Flex modulus was tested on universal material testing machine Instron 5567 according to ISO178:2001 (E).

Heat deflection temperature (HDT) was determined at a load of 1 .80 MPa according to ISO75.

Embodiments of the present invention are further defined in the following Examples. Compositions of the examples and comparative examples as well as the evaluation results are shown in Tables 1 to 5.

Table 1

From the results of Table 1 , the following are evident.

When the amount of polyamide resin were kept at 65%, the vibration damping effect tends to be increasing as the amount of zinc oxide increased. Because the glass fiber (i.e. the fibrous reinforcing agent) functioned as reinforcement filler for the noise damping composition of the invention, as the amount of glass fiber decreased, the tensile modulus and flex modulus also decreased. Therefore, depends on the specific application of the noise damping composition, one can obtain a noise damping composition of this invention by selecting a suitable ratio between the fibrous reinforcing agent and the polyamide resin which meets the mechanical property requirements; then varying the amount of the zinc oxide to provide the desired damping effect. Preferably, for applications used in the powertrain system of a transportation vehicle, the ratio between the polyamide resin and the fibrous reinforcing agent, in the present noise damping compositions, is from 55:45 to 85:15; more preferably, 60:40 to 80:20; most preferably, 65:35 to 75:25.

In one embodiment, in the noise damping compositions of the present invention, the weight ratio between the polyamide resin and the fibrous reinforcing agent is from 55:45 to 85:15; more preferably, 60:40 to 80:20; and most preferably, 65:35 to 75:25.

The heat deflection temperature (HDT) data of the working examples (E1 -E5) showed the same or higher than that of the control sample (C1 ), which suggest that the present inventive noise damping compositions can be used for applications have high temperature requirement, e.g., for powertrain system with working temperature around 150°C.

Table 2

Table 3

From the results of Tables 2-3, the following are evident.

From the comparison between E6-E10 vs. C1 and E1 1 -E16 vs. C2, the compositions containing 2-13 wt% of zinc oxide effectively provided vibration damping results as judged by the greater damp loss factor (at 625 Hz, 1562 Hz, and 3124 Hz) than that of the C1 or C2, respectively. Note that the ratio of polyamide resin to glass fiber was 65:35 for E6-E10 and E1 1 -E16, and the resulting noise damping compositions still have about 90 to 105% of the tensile modulus and flexural modulus compared to that of the respective control sample (C1 or C2).

Additionally, the noise damping compositions of the invention (i.e. E7-E9 vs. C1 ) also demonstrated which can effectively attenuate the sound transmission up to 2.5 dB.

In one embodiment, the noise damping composition of the present invention comprises, consists essentially of, contains from about 1 to 15 weight% of zinc oxide, wherein the zinc oxide is a nanoparticle having a average particle size less than 60 nm, and the weight % is based on the total weight of the noise damping composition. Table 4

From the results of Table 4, the following are evident.

From the comparison between E17-E21 vs. C3 and E22 vs. C2, the 5 compositions containing 2-9 wt% of zinc oxide whisker effectively

provided vibration damping results as judged by the greater damp loss factor (at 625 Hz, 1562 Hz, and 3124 Hz) than that of the C3 or C2.

Comparing the tensile modulus and flexural modulus data of the working examples (E17-E21 and E22) and that of the respective control 10 example (C3 or C2), the presence of zinc oxide didn't adversely affect the mechanic properties of the noise damping compositions.

Furthermore, the noise damping compositions of the invention (i.e. E17-E21 vs. C3) also demonstrated which can effectively attenuate the sound transmission up to 3.8 dB.

15 In one embodiment, the noise damping composition of the present invention comprises, consists essentially of, contains from about 1 to 10 weight% of zinc oxide, wherein the zinc oxide is a tetrapod-shaped zinc oxide whisker, and the weight % is based on the total weight of the noise damping composition. While the invention has been illustrated and described in typical embodiments, it is not intended to be limited to the details shown, since various modifications and substitutions are possible without departing from the spirit of the present invention. As such, modifications and equivalents of the invention herein disclosed may occur to persons skilled in the art using no more than routine experimentation, and all such modifications and equivalents are believed to be within the spirit and scope of the invention as defined by the following claims.

Claims

CLAIMS What is claimed is:

1 . A noise damping composition comprising:

(a) 50-85 weight % of a polyamide;

(b) 5-45 weight % of a fibrous reinforcing agent;

(c) 1 -25 weight % of zinc oxide; and

(d) 0-15 weight % of other additive; and

wherein the weight % is based on the total weight of the noise damping composition, and provided that the composition comprises essentially no flame retardants.

2. The noise damping composition of Claim 1 , wherein the polyamide is selected from the group consisting of nylon 66, nylon 6, nylon 66/6, nylon 46, nylon1010, nylon 10, nylon 12, nylon 1212, nylon 610, nylon 612, nylon 66/6T, nylon 6T/DT, nylon MXD-6, and blends thereof.

3. The noise damping composition of Claim 2, wherein the polyamide is nylon 66, nylon 6, nylon 66/6, or a blend thereof; and the amount of the polyamide ranges from 50-75 weight %, based on the total weight of the noise damping composition.

4. The noise damping composition of Claim 1 , wherein the fibrous reinforcing agent is glass fiber, carbon fiber, or para-aramid fiber.

5. The noise damping composition of Claim 1 , wherein the fibrous reinforcing agent is glass fiber, and amount of the fibrous reinforcing agent ranges from 20-40 weight %, based on the total weight of the noise damping composition.

6. The noise damping composition of Claim 1 , wherein the weight ratio between the polyamide and the fibrous reinforcing agent ranges from 50:50 to 95:5.

7. The noise damping composition of Claim 1 , wherein the zinc oxide is selected from nano-zinc oxide or zinc oxide whisker, and the amount of zinc oxide ranges from 5-10 weight % based on the total weight of the noise damping composition.

8. The noise damping composition of Claim 7, wherein the zinc oxide is nano-zinc oxide having a particle size ranging from 5-100 nm,

9. The noise damping composition of Claim 7, wherein the zinc oxide is zinc oxide whisker and has a size in the micrometer range.

10. The noise damping composition of Claim 7, wherein the zinc oxide is tetrapod-shaped zinc oxide whisker and is not surface treated with silane coupling agent.

1 1 . The noise damping composition of Claim 1 , wherein the amount of zinc oxide ranges from about 5 to 10 weight %, based on the total weight of the noise damping composition.

12. The noise damping composition of Claim 1 , wherein the other additive is selected from the group consisting of antioxidants, thermal stabilizers, ultraviolet light stabilizers, colorants including dyes and pigments, lubricants, hydrolysis resistants, demolding agents, mineral, mica, flow modifiers, and chain extenders.

13. A molded article comprising the noise damping composition of Claim 1 .

14. The molded article of Claim 13 which is a noise-damping part of a transportation vehicle, wherein the transportation vehicle is an

automobile, an airplane or a boat.

15. The molded article of Claim 13 or noise-damping part of Claim 14 is selected from the group consisting of parts used in the transmission system, parts used in the intake and exhaust devices, parts used in the cooling system, parts used in the engine system, parts used in the electronic fuel injection system, and parts used in the body.

16. The molded article of Claim 13 is selected from the group consisting of a power tool, an electrical motor, and a home appliance.