The present invention relates to coating materials for acoustic attenuation.
More particularly, invention relates to usage of spray-able type filler-modified
polyurethane resin (acrylic poly-ol) and hardener (aliphatic iso-cyanate) based
coating materials for its specific compositions and preparations for the purpose
of acoustic attenuation in various industrial machineries and allied areas.
BACKGROUND OF THE INVENTION
Numerous methods have been described in prior art, for the control of noise and
vibration utilizing simple passive barrier, damping concepts, absorptive
techniques and electronic noise canceling approaches. Absorptive techniques
are utilized to prevent or reduce air borne acoustic energy from reaching a
receiving site. Acoustic absorptive materials are usually porous, e.g., foams,
felts, porous or expandable graphite etc., with the pores inter-connecting
throughout the material. These materials are usually light in weight and most
effective at shorter wavelengths (i.e., higher frequencies), however their
structural strength is often limited. While the 'mass law' applies to a relatively

thin, homogeneous and single layer panel. The mass law states that the loss of
energy, as it transits a barrier over a wide frequency range, is a function of the
surface density of the barrier material and the frequency. By increasing the mass
of the material and thickness of the layer and density, the acoustic barrier for all
frequencies including those in the lower region in the spectrum could be
improved. In this regard, filler material play significant role and this gain in
transmission loss is at the cost of added barrier weight.
A variety of filler materials have been reported to use in acoustic and vibration
damping applications. United States Patent Number 6,872,761 B2 dated March
29, 2005 by Kevin J LeStarge et. al., used so-called expandable microspheres in
an aqueous coating composition comprising at least one dispersed polymer and
one inorganic filler helps that improved the appearance and/or sound damping
properties of the coating which was obtained by heating the aqueous coating
composition prior applying to the surface of a substrate.
Chinese Patent Publication Number CN101891990 B dated August 1, 2012
discloses a water-based sound damping coating comprising various
combinations of inorganic fillers, i.e., talc, mica, calcium carbonate, kaolin,
barium sulfate or their mixtures thereof including usage of flame retardant
materials like, aluminum hydroxide or magnesium hydroxide, zinc borate,
aluminum phosphate etc or any combinations of their mixtures thereof. The base
material includes po.yurethane, which is part by weight, i.e., 15 to 35 parts of

polymer emulsion, 10 to 20 parts of powdery flame retardant, 2 to 5 parts of
auxiliary agent, 35 to 55 parts of inorganic filler, and 10 to 20 parts of de-ionized
water. The polymer emulsion is described as styrene-acrylic emulsion, acrylic
emulsion or copolymer emulsion and polyurethane emulsion of any two of the
emulsion. The coating is used as internal coating of carriage floors, side walls
and roofs of vehicles, and can play a good role in inhibiting vibration and
reducing noise.
Chinese Patent Publication Number CN101665654 A, dated March 10, 2010
discloses a spraying type polyurethane-carbamide vibration and noise
attenuation material combining various filler materials, i.e., calcium carbonate,
quartz powder, graphite, titanium dioxide, clay, vermiculite, mica, heavy crystal
stone, talc, glass flake in one or several in the formulations. As claimed, the
material has the advantages of fast curing speed, good visco-elasticity, high
intensity, excellent damping vibration attenuation noise-reduction property and
can efficiently construct under a complex to severe environmental condition.
United States Patent Publication Number US20080039564 A1 dated February 14,
2008 by U.C. Desai et. al. describes an aqueous coating composition exhibiting
sound dampening properties that comprise an aqueous dispersion of polymeric
micro-particles, a filler that may include barium sulfate and/or calcium
metasilicate and at least two different plasticizers. The plasticizer comprises at
least two different plasticizers and the plasticizer is present in the coating

composition in an amount of from 0.1 to less than 20 percent by weight based on
total weight of the coating composition. The sound dampening properties
exhibited by the aqueous coating composition are measured by a composite loss
factor of at least 0.01, or 0.1, at a frequency of 200 Hz measured at a
temperature of 0, 20 and 40° C respectively.
Chinese Patent Publication Number CN203497126 U, dated March 26, 2014
describes the utilization of polyurethane materials for the construction of sound
proof structures for ship crew cabins. As per the invention, the combination of
materials for sound proofing is, i.e., an adhesive layer with thickness of 1 mm, a
foam of 4 mm (with compression of 40% to the aluminum layer), a fireproof
nonwoven fabric with thickness of 0.6 mm, a damping rubber layer of 2 mm and
finally a polyurethane-based two-component noise damping paint (so-called T54
and T60 commercial trade name) with thickness of 3 mm; all for bringing down
the desired noise level at 50 dB (A).
Chinese Patent Publication Number, CN102876159 A, dated January 16, 2013
describes a noise-proof damping coating utilizing 4-9% of waterborne
polyurethane materials including other components, which are 23-30% of acrylic
emulsion, 36-50% of ultrapure water, 3-5% of silicone, 10-14% of waterborne
styrene-acrylic emulsion, 5-8% of antimony oxide, 6-8% of hydrated magnesium
silicate ultrafine powder and 2-3% of a plasticizer. As claimed, the noise-
proof damping coating is advantageous in that objects of decreasing housing

vibration and reducing noise, can be reached by applying the coating on movable
articles, besides the coating to be environment-friendly and has good
performance and physical stability, and can not generate sagging.
Chinese Patent Publication Number CN101625856 B dated August 31, 2011
describes a multi-frequency sound-absorbing polyurethane based foam material
comprising a foam layer, a paint layer and the plastic foil layer, wherein the foam
layer is an intermediate layer having thickness of in the range of 1 - 20 mm, the
thickness of the coating layer is from 0. 01 -1 urn, thickness of the plastic layer is
0.01 - 100 mm that has good sound absorbing effect in the frequency range of
250-1000 Hz.
French Patent Publication Number WO2011162740 A1 dated December 29,
2011 by S.G. Iyer et. al. describes sound damping compositions that include a
polymer, a polyacrylate rheology modifier, and a polyurethane rheology modifier
respectively. These compositions can alternatively include a polymer derived
from greater than 80% of one or more monomers selected from the group
consisting of butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, methyl
acrylate and ethyl acrylate and combinations thereof and greater than 0% and
less than 4% of one or more functional monomers, at least one rheology modifier,
and a surfactant. These sound damping products, as described, could be used in
structures, including, for example, textiles, floors, automobile dashboards, doors,
and roofs and also for damping sound in a structure etc.

French Patent Publication Number WO2006007273 A2 dated January 19, 2006
by Corina Bisog et. al. describes noise and vibration damping applications using
blocked polyurethane pre-polymers as coated structures or compositions on thin
metal substrates. This formulations were obtained by reacting at least one poly-ol,
a first poly-isocyanate comprising diphenylmethane di-isocyanate, a second poly-
isocyanate having a viscosity at 25°C of less than about 250 mPa.s, a phenol
blocking agent, and an oxime blocking agent, wherein the weight ratio of 'second
poly-isocyanate: first poly-isocyanate' is not more than 0.65 :1.00. As described,
such compositions are relatively low in viscosity, are comparatively inexpensive
to produce, are storage-stable, and are capable of providing cured coatings upon
heating that are highly adhesive and chip-resistant.
United States Patent Number US6316514 B1, dated November 13, 2001 by
Peter Falke et. al. (BASF Aktiengesellschaft) describes a process for producing
sound-damping and energy-absorbing polyurethane foams by reacting organic
and/or modified organic poly-isocyanates (a) with a poly-etherol mixture (b) and,
if desired, further compounds (c) bearing hydrogen atoms which are reactive
toward isocyanates, in the presence of water and/or other blowing agents (d),
catalysts (e) and, if desired, further auxiliaries and additives (f), in which a
specific poly-etherol mixture is used.

United States Patent Publication Number US20130253107 A1 dated September
26, 2013 by S.G. Iyer et. al. (BASF ) describes sound damping compositions that
can combine a polymer, a poly-acrylate rheology modifier, and
a polyurethane rheology modifier respectively. The compositions can
alternatively include a polymer derived from greater than 80% of one or more
monomers selected from the group consisting of butyl acrylate, 2-ethylhexyl
acrylate, methyl methacrylate, methyl acrylate and ethyl acrylate and
combinations thereof and greater than 0% and less than 4% of one or more
functional monomers, at least one rheology modifier, and a surfactant. The
methods include applying the compositions to the surface of a structure and
drying the composition thereof.
Polyurethane formulations have also been used in order to improve the tactile
properties of plastic parts in the car interiors, against external influences, such as
sunlight and chemical, thermal and mechanical stress and also to obtain
particular colours and colour effects in the interiors. United States Patent
Publication Number US20060079635 A1, dated April 13, 2006 by T. Pohl et. al.
(Bayer Materialscience Ag) describes preparations comprise aqueous
polyurethane-polyurea dispersions, hydroxy-functional, aqueous or water-
dilutable binders, polyisocyanates which may have been hydrophilically modified,
and foam stabilizers. Polyurethane resin coating preparations (30-50 parts) have
also been used as a super hydrophobic self cleaning purposes besides
maintaining other properties like antifouling, anti-sticking, de-noise and

drag reduction, etc in the same material using poly-tetrafluoroethylene powder as
a filler (100 parts), mixed solvents of acetone and ethyl acetate (300-500 parts)
and y- aminopropyl trimethoxysilane with refractive index of 1.42-1.43 (1-5 parts)
respectively in the preparation (Chinese Patent Publication Number
CN101205439 A dated June 25, 2008).
Another known approach of sound damping comprises dual-layered structures in
which polymers with different viscosities are stacked in layers using 'plastisol
layers' on PVC or metbacrylate substrates are explained in the US Patent
Numbers US5.227.592 by Kosters et. al., and US4,346,782 by Bohm et. al.,
respectively. In Kosters invention, at least one of the layers is foamed, though
such patch structures suffer from limited adherence with PVC and/or acrylic
including metal surfaces, besides the foamed materials can absorb liquids, such
as processing fluids, and/ or liquids encountered in ambient storage or use of the
articles that could cause corrosion, and can interfere with subsequent processing
operations. Other issues include relatively high glass transition temperature of
the polymers, which are also prone to cracking, de-lamination etc.
US 2009/0277716 A1, describes a composite structure containing a so-called
extension layer and rigid layer for noise damping of articles, out of which, in
some instances, the constraining layer may cover all of the extensional layer,
while in other instances, it may cover only a portion of the extensional layer. In
particular instances, the modulus of elasticity of the constraining layer is greater

than that of the modulus of elasticity of the material comprising the extensional
layer. The first polymeric material may comprise a viscoelastic polymer. In
particular instances, at least one of the polymeric materials is a thermally curable
material. In particular instances, the thickness of the extensional layer is in the
range of 1 - 6 mm, while in some particular instances, the thickness of this layer
is in the range of 2 - 4 mm with loss factor of the composite structure is greater
than 0.1 for frequencies in the range of 200 - 800 HZ. Usage of viscoelastic
damping materials in various forms of sheets and laminates for noise and
vibration reduction is known and Journal of Sound and Vibration, Volume 319,
Issues 1-2, 2009, Pages 58-76 discusses this effect.
Though viscoelastic polymers are unique in several ways, there are also certain
limitations. One such limitation is the relatively higher level of curing temperature,
which is usually in the range of 180 - 200°C, which is often disadvantageous for
applications as a coating material. For example, in case of industrial machineries,
the vibrating parts of machines could be associated with numerous shapes,
geometry and dimension etc, and hence an ambient temperature curing for the
coated objects or parts would be preferred. Besides, several viscoelastic
polymers are not available commercially because of proprietary nature. Hence,
there is a need for developing spray-able type liquid-based coating materials
preferably by using common polymers as a base material with required
modifications by desired filler materials etc and importantly cures at ambient
temperature. This would let the vibrating parts of the machines with complex

shapes etc to be spray coated without employing any arrangement for heat
treatment for curing and noise attenuation could be achieved. Also, there is a
further need to develop such materials with appropriate modifications etc, in a
manner that the noise and vibration could be maximized with structures or coated
layers even with relatively low level of thickness, i.e., in the range of 1 - 3 mm.
Machineries belonging to numerous industries related to manufacturing,
automobiles, appliances, processing, operations related to grinding, cutting,
mixing, milling etc are usually composed of various metal structures or sheets etc.
Such metallic parts (particularly sheets etc) are indeed a good source of acoustic
vibrations and hence often pose significant noise problems while in operation.
Various measures have been addressed to control such noise problems.
However, the materials those could be applied by conventional spray coating
method that cures at ambient temperature, pressure and humidity conditions
would be advantageous.
OBJECTS OF THE INVENTION
Accordingly, an object of the invention is to propose a process to prepare filler-
modified commercial grade polyurethane resin (acrylic poly-ol) hardener
(aliphatic iso-cyanate) based coating materials for acoustic attenuation and
vibration damping.

Another object of the invention is to propose a process to prepare filler-modified
commercial grade polyurethane resin (acrylic poly-ol) hardener (aliphatic iso-
cyanate) based coating materials for acoustic attenuation and vibration damping,
in which various pre-defined solid filler material/s are incorporated in the
polyurethane resin to generate various filler-modified polyurethane resin-based
coating materials with variable levels of modulus of elasticity (MOE).
Further object of the invention is to propose a process to prepare filler-modified
commercial grade polyurethane resin (acrylic poly-ol) hardener (aliphatic iso-
cyanate) based coating materials for acoustic attenuation and vibration damping,
in which various 'bi-layer composite structure/s' of the derived coating materials
are generated by chossing one material as a 'base coat' and another material as
a 'top coat' respectively on the basis of differential levels of MOE.
Still another object of the invention is to propose a process to prepare filler-
modified commercial grade polyurethane resin (acrylic poly-ol) hardener
(aliphatic iso-cyanate) based coating materials for acoustic attenuation and
vibration damping, which ensures adherence in base layer to top layer in the bi-
layer composite structure including a long-term stability of the structure, i.e.,
protecting against environment, pilling off, cracking, voids, defects etc.
Yet another object of the invention is to propose a process to prepare filler-
modified commercial grade polyurethane resin (acrylic poly-ol) hardener

(aliphatic iso-cyanate) based coating materials for acoustic attenuation and
vibration damping, which includes typical combinations of 'bi-layer composite
structures' associated with superior acoustic attenuation characteristics within
numerous possible combinations of the 'bi-layer composite structures' of the
derived coating materials.
Those and further objects of the invention would be understood by accomplishing
various examples and process demonstrations in the subsequent sections.
SUMMARY OF THE INVENTION
According to this invention, there is provided Spray-able type filler modified
polyurethane resin hardener based coating materials for acoustic attenuation in
the form of coated structure or fabricated sheets wherein the said structure is bi-
layer composite structure having a "base coat" that has lower level of MOE and a
top coat having higher levels of MOE, wherein the said coating materials,
comprises of a commercial-grade liquid polyurethane resin (acrylic poly-ol), pre-
defined solid filler material/s and a liquid hardener material (aliphatic iso-cyanate)
respectively.
In accordance with this invention there is provided A process for preparing a filler
modified polyurethane resin-based liquid coating material for acoustic attenuation
comprising the steps of:

mixing and dispersing the solid filler material with commercial grade liquid
polyurethane resin using a ball mill machine for 4 to 8 hrs to form "filler-modified
polyurethane resin emulsion",
subjecting the said "filler-modified polyurethane resin emulsion" to the step of
mixing it with a hardener material for a period of another 15-30 minutes to form
"filler-modified polyurethane coating materials",
casting and curing the said filler-modified polyurethane coating materials" into
solid performs under natural conditions and ambient temperature pressure and
humidity;
evaluating modulus of elasticity (MOE) of the said "filler-modified polyurethane
coating materials; and
generating multiple "bi-layer composite structures" by selecting the "filler modified
polyurethane coating materials" those associated with lower levels of MOE as
"base coat" and the "top coat" having higher level of MOE.
DETAILED DESCRIPTION OF THE INVENTION
As would be explained in detail herein below, the present invention provides
processing and manufacturing of a liquid-based, spray-able type, filler-modified
polyurethane resin (acrylic poly-ol) hardener (aliphatic iso-cyanate) based
coating material for the purpose of noise and vibration damping, besides using
the same material as environmental protection of corrosion and aesthetics. The

invention also provides how the modulus of elasticity (MOE) of the polyurethane
resin could be altered, both in positive and negative directions by incorporating
suitable filler material/s to the blank polyurethane resin. The invention would
further demonstrate how noise attenuation could be maximized by using a so-
called 'bi-layer composite structure' in the polyurethane coating materials by
incorporating various filler materials in the blank resin with an objective to vary
the MOE in the filler-modified polyurethane coating materials. These and other
advantages of the invention, i.e., choice of commercial grade liquid-based two-
component polyurethane resin system, incorporation of the identified filler
materials, ambient temperature curing of the coating material etc would be
apparent from the discussion and descriptions in the subsequent sections.
The present invention refers to preparation of spray-able type liquid-based filler-
modified polyurethane resin (acrylic poly-ol) and hardener (aliphatic iso-cyanate)
coating materials for the purpose of acoustic attenuation. The coating materials
are prepared by incorporating suitable filler material/s in the commercial-grade
polyurethane resin-hardener system. The derived materials in isolation or in
combination could be used for the purpose of acoustic attenuation and vibration
damping. The derived composite materials could be applied on the surface of
various vibrating objects or parts (that contribute to noise generation), by coating
or by spraying the material with desired level of thickness and then by natural
curing the material with the help of a hardener that cures at ambient temperature,
pressure, humidity conditions etc.

According to the present invention and in order to accomplish the above objects,
there is provided a process for incorporating pre-defined filler material/s into the
commercial-grade polyurethane resin for the preparation of filler-modified
polyurethane resin coating materials in the form of spray-able type liquid paints.
The filler-modified polyurethane resin paints are prepared by incorporating
variable amounts of different filler materials in the range of 20 - 60 weight
percentage into the polyurethane resin system, so as to generate numerous
types of filler-modified polyurethane resin composite materials, all of which are
associated with variable levels of modulus of elasticity (MOE) in the said coating
materials.
In a more particular embodiment of the present invention, the filler materials are
defined as i) melamine powder (C3H6N6) and ii) barium sulphate (BaSO4)
respectively. As stated, the incorporation of the said filler materials in the
commercial-grade polyurethane resin would generate various composite
materials with variable levels of MOE in the composites. Table 1 presents the
MOE levels of some representative filler-modified polyurethane coating materials.
As per the invention, desired amounts (in volume parts) of polyurethane resin
(acrylic poly-ol) and the filler materials, i.e., melamine powder and barium
sulphate powder respectively are to be mixed separately and milled by using a
ball mill machine or a suitable mixing/milling machine for a period of 4 - 8 hours

in order to get homogenized filler-mixed polyurethane resin emulsions. To this
filler-mixed polyurethane resin emulsions, an appropriate amount of hardener
(aliphatic iso-cyanate) depending on the proportion of the polyurethane resin is to
be mixed and thereafter milling operation by ball mill is to be continued for a
period of another 15-30 minutes, after which spray-able type filler-modified
coating materials would result.
For the purpose of evaluating the MOE profile of the resultant filler-modified
polyurethane resin, the material is to be casted in the form of blocks with desired
dimension and to be cured naturally at ambient temperature, pressure and
humidity etc for a period of 15 - 20 hours. After curing, the material turns into a
solid structure, which is used for measuring MOE of the materials. The Table 1
shows how MOE level of blank polyurethane resin could be altered in the
resultant filler-modified polyurethane resin composite materials, by suitably
incorporating the filler materials into the polyurethane resin-hardener system.
For the purpose noise attenuation and vibration damping, the filler-modified
polyurethane resin composite material could be applied or coated by spraying or
brushing the material on the surface of the vibrating parts or objects of any target
or any identified machine. In case of spray coating, any standard spray gun could
be used by maintaining a corresponding pressure of 70 - 80 psi and layers of the
composite materials could be generated on the surface of the target object or
parts. However, such coated layers could consist either a single composite

material or a combination of two composite materials as per the Table 1 or
outside the Table 1, just by varying the filler amount in the polyurethane-hardener
system. Hence Table 1 presents only certain representative filler-modified
polyurethane resin based composite materials. The spraying process could be
repeated in order to eliminate surface voids or defects of the spray-coated layer
and also to generate higher level of thickness.
Hence, various 'bi-layer composite structure* could be generated by selecting any
two composite materials on the basis of differential MOE using Table 1. The layer
which is coated directly to the surface of the vibrating or noise generating
structure or part is called 'base coat" and the layer above this 'base coat' is called
'top coat'. The 'top coat' is usually generated after the curing of the 'base coat'
layer. The composite material belonging to such 'base coat' is associated with
lower level of MOE as compare to that of the 'top coat" which has relative higher
level of MOE in this tri-component 'polyurethane resin-hardener-filler' system.
The noise attenuation and vibration damping for each bi-layer composite
structure could be evaluated by identifying certain industrial machine and the
effectiveness of noise attenuation involving such bi-layer composite structure
could be realized. By this process, the 'bi-layer composite structure' that is more
effective for noise attenuation and vibration damping could also be realized.

In order to accomplish the noise attenuation characteristics of various 'bi-layer
composite structures' of the derived materials, one industrial machine, i.e.,
ceramic tile cutting blade wheel (which is made of stainless steel with a thickness
of 2.54 ± 0.05 mm), which is operated by an electric motor with rpm about 2800
was chosen. It was also realized that the metallic blade wheel is a vibrating part
in the identified machine for generating the noise while cutting the ceramic tiles.
Since the blade wheel has two sides, the 'bi-layer composite structure' was
generated on the surface of the said wheel in both the sides by spraying the
identified 'base coat' and 'top coat', respectively.
In order to understand the effectiveness of the bi-layer composite structure/s for
noise attenuation characteristics, the measurements were carried out in both 'un-
coated (blank)' and 'coated with 'bi-layer composite structure' conditions in the
blade wheel. All the noise level measurements of the blade wheel (while cutting
the ceramic tiles) were carried out under identical conditions. It has been
observed that the noise attenuation is more effective, as the difference in MOE
increases in the bi-layer composite structure.
The process could be more realized by citing more examples which are brought
out in the following sections.
Example 1:

The 'base coat', which is termed as 'PUM20' was prepared as per following
procedure in this example:
80 volume parts of polyurethane resin (acrylic poly-ol) and) was mixed with 20
weight percentage of melamine (C3H6N6) filler material in a plastic container and
allowed to be milled (dispersed) for a period of about 4 hours in a standard 'ball
mill machine' using ceramic balls as the mixing/grinding media and by
maintaining a rpm of 80, after which a 'melamine-modified polyurethane resin
emulsion' resulted. To this 'filler-mixed polyurethane resin emulsion', 20 volume
parts of hardener (aliphatic iso-cyanate) was added and mixing operation was
continued for a period another 20 minutes that results a spray-able type
'melamine-modified polyurethane resin emulsion' and this preparation is
regarded as the 'base coat' (PUM20) in this example. This 'base coat'
preparation, when casted in the form of blocks with dimensions of about 100 x 30
x 10 mm in the cured state showed a MOE value of 3.37 GPa.
In order to prepare the 'top coat' in this example, 80 volume parts of
polyurethane resin (acrylic poly-ol) was mixed and milled with 60 weight
percentage of barium sulphate filler material in a plastic container for a period of
about 4 hours in a standard a 'ball mill machine' using ceramic balls as
mixing/grinding with a counter rpm of about 80 in the machine, after which a
'barium sulphate modified polyurethane resin' resulted. To this preparation,
about 20 volume parts of hardener (aliphatic iso-cyanate) was added and mixing

operation was continued for another period of 20 minutes that results a barium
sulphate-modified polyurethane resin emulsion' and this preparation is regarded
as the 'top coat' and termed as 'PUB60' in this example. This 'top coat'
preparation, when casted in the form of blocks with dimensions of about 100 x 30
x 10 mm in the cured state showed a MOE value of 5.71 GPa.
The 'base coat' (PUM20) was sprayed on the surface of the ceramic tile cutting
wheel blade (which is made of stainless steel with a thickness of 2.54 ± 0.05 mm)
on both the sides by using a spray gun and by maintaining the pressure level of
about 70 psi and then cured under natural conditions of temperature, pressure
and humidity etc. The spraying operation was continued until a thickness profile
of 1.43 ± 0.05 mm resulted after curing, which accounts about 0.715 mm in each
side of the blade wheel.
The 'top coat' (PUB60) was then sprayed on the surface of the cured layer of the
base coat of ceramic tile cutting wheel blade on both the sides by using a spray
gun and by maintaining the pressure level of about 70 psi and thereby cured
under natural conditions. The total thickness after the curing resulted to 2.08 ±
0.05 mm, which accounts about 1.04 ± 0.05 mm in each side together the base
and the top coat respectively.
Ceramic tile (alumina ceramic tile with density of about 3.3 ± 0.05 g/cc) was
chosen for evaluating the noise attenuation characteristics of the cutting wheel

blade. The blade wheel was operated by an electric motor with rpm of about for
cutting the ceramic tiles. The 'A-weighted noise levels' of both 'LAeq(dB)' and
'LAFmax(dB)' were recorded by maintaining identical conditions of ceramic tile
cutting operation in both 'blank (un-coated)' and 'bi-layer composite structure
coated' conditions of the blade wheel, by following IEC 61672-2:2006 noise
measurement standard.
The 'LAeq(dB)' noise level of the blade wheel (blank or un-coated conditions)
during operation is 87.2 ± 1 dB and to that of 'coated bi-layer composite
structure' is 83.7± 1 dB respectively. This example demonstrates the noise
reduction of about 3.5 ± 1 dB for the blade wheel, which is associated with this
specific 'bi-layer composite structure' in with a thickness of about 2.08 ± 0.05 mm.
Example 2:
The 'base coat', which is termed as 'PUM40' was prepared as per following
procedure in this example:
80 volume parts of polyurethane resin (acrylic poly-ol) was mixed with 40 weight
percentage of melamine filler material in a plastic container and allowed to be
milled (dispersed) for a period of about 4 hours in a standard 'ball mill machine'
using ceramic balls as the mixing/grinding media and by maintaining a rpm of 80,

after which a 'melamine-modified polyurethane resin' resulted. To this 'filler-
mixed polyurethane resin', 20 volume parts of hardener (aliphatic iso-cyanate)
was added and mixing operation was continued for a period another 20 minutes
that results a spray-able type 'melamine-modified polyurethane resin emulsion'
and this preparation is regarded as the 'base coat" (PUM40) in this example.
This 'base coat' preparation, when casted in the form of blocks with dimensions
of about 100 x 30 x 10 mm in the cured state showed a MOE value of 2.79 GPa.
The preparation of the 'top coat' in this example remains the same to that of
Example 1 and hence of MOE value remains the same.
The coating procedure and creating 'bi-layer composite structure' remained the
same to that of Example 1. The thickness profile of 'base coat' (PUM40) in this
example was 1.47 + 0.05 mm that accounts 0.735 ± 0.05 mm in each side of the
blade wheel. The total thickness after the curing the 'top coat' resulted to 2.07 ±
0.05 mm, which accounts about 1.035 ± 0.05 mm in each side together the base
and the top coat respectively.
Similar types of ceramic tile (alumina ceramic tile with density of about 3.3 ± 0.05
g/cc) was chosen for evaluating the noise attenuation characteristics of the
cutting wheel blade and the operation conditions remained the same for cutting
the ceramic tiles. The 'A-weighted noise levels' of both 'LAeq(dB)' and
'LAFmax(dB)' were recorded by maintaining identical conditions of ceramic tile

cutting operation in both 'blank (un-coated)' and 'bi-layer composite structure
coated' conditions of the blade wheel, by following IEC 61672-2:2006 noise
measurement standard.
The 'LAeq(dB)' noise level of the blade wheel (blank or un-coated conditions)
during operation is 87.2 ± 1 dB and to that of 'coated bi-layer composite
structure' is 83.1 ± 1 dB respectively. This example demonstrates the noise
reduction of about 4.1 ±1 dB for the blade wheel, which is associated with this
specific 'bi-layer composite structure' in with a thickness of about 2.07 ± 0.05 mm.
Example 3:
The 'base coat', which is termed as 'PUM60' was prepared as per following
procedure in this example:
80 volume parts of polyurethane resin (acrylic poly-ol) was mixed with 60 weight
percentage of melamine filler material in a plastic container and allowed to be
milled for a period of about 4 hours in a standard 'ball mill machine' using
ceramic balls as the mixing/grinding media and by maintaining a rpm of 80, after
which a 'melamine-modified polyurethane resin' resulted. To this 'filler-mixed
polyurethane resin', 20 volume parts of hardener (aliphatic iso-cyanate) was
added and mixing operation was continued for a period another 20 minutes that
results a spray-able type 'melamine-modified polyurethane resin emulsion' and

this preparation is regarded as the 'base coat' in this example. This 'base coat'
(PUM60) preparation, when casted in the form of blocks with dimensions of
about 100 x 30 x 10 mm in the cured state showed a MOE value of 3.75 GPa.
The preparation of the 'top coat' (PUB60) in this example remains the same to
that of Example 1 and hence the MOE remains the same here as well.
The coating procedure and creating 'bi-layer composite structure' remained the
same to that of Example 1. The thickness profile of 'base coat' in this example
was 1.41 ± 0.05 mm that accounts 0.705 ± 0.05 mm in each side of the blade
wheel. The total thickness after the curing the 'top coat' resulted to 2.08 ± 0.05
mm, which accounts about 1.04 + 0.05 mm in each side together the base and
the top coat respectively.
Similar types of ceramic tile (alumina ceramic tile with density of about 3.3 ± 0.05
g/cc) was chosen for evaluating the noise attenuation characteristics of the
cutting wheel blade and the operation conditions remained the same for cutting
the ceramic tiles. The 'A-weighted noise levels' for both 'LAeq(dB)' and
'LAFmax(dB)' were recorded by maintaining identical conditions of ceramic tile
cutting operation in both 'blank (un-coated)' and 'bi-layer composite structure
coated' conditions of the blade wheel, by following IEC 61672-2:2006 noise
measurement standard. However, only 'LAeq(dB)' values have been considered

in each case for comparison from one 'bi-layer composite structure' to another
structure.
The 'LAeq(dB)' noise level of the blade wheel (blank or un-coated conditions)
during operation is 87.2 ± 1 dB and to that of 'coated bi-layer composite
structure' is 83.5 ± 1 dB respectively. This example demonstrates the noise
reduction of about 3.7 ± 1 dB for the blade wheel, which is associated with this
specific 'bi-layer composite structure' in with a thickness of about 2.08 ± 0.05 mm.
Table 2 demonstrates the summary of the of noise damping characteristics of
various bi-layer composite structures by taking a typical industrial ceramic cutting
blade wheel operation as an example, noise attenuation of which has been
generated by maintaining under identical conditions of operation.
Therefore, the acoustic attenuation characteristics of the aforesaid filler-modified
polyurethane resin based composite emulsion by coating such materials on noise
generating surfaces with typical bi-layer composite structures is established in
this invention.

WE CLAIM:
1. Spray-able type filler modified polyurethane resin hardener based coating
materials for acoustic attenuation in the form of coated structure or
fabricated sheets wherein the said structure is bi-layer composite structure
having a "base coat" that has lower level of MOE and a top coat having
higher levels of MOE, wherein the said coating materials, comprises of a
commercial-grade liquid polyurethane resin (acrylic poly-ol), pre-defined
solid filler material/s and a liquid hardener material (aliphatic iso-cyanate)
respectively.
2. A process for preparing a filler modified polyurethane resin-based liquid
coating material for acoustic attenuation comprising the steps of:
mixing and dispersing the solid filler material with commercial grade liquid
polyurethane resin using a ball mill machine for 4 to 8 hrs to form "filler-
modified polyurethane resin emulsion",
subjecting the said "filler-modified polyurethane resin emulsion" to the step
of mixing it with a hardener material for a period of another 15-30 minutes
to form "filler-modified polyurethane coating materials",
casting and curing the said filler-modified polyurethane coating materials"
into solid performs under natural conditions and ambient temperature
pressure and humidity;

evaluating modulus of elasticity (MOE) of the said "filler-modified
polyurethane coating materials; and
generating multiple "bi-layer composite structures" by selecting the "filler
modified polyurethane coating materials" those associated with lower
levels of MOE as "base coat" and the "top coat" having higher level of
MOE.
3. The process as claimed in claim 1, wherein the filler materials for lowering
the modulus of elasticity (MOE) in the blank commercial grade
polyurethane resin is melamine powder (C3H6N6) and wherein, for
enhancing the MOE is barium sulphate (BaSO4) respectively.
4. The process as claimed in claim 1, wherein the MOE of the coating
material after filler modifications is in the range of 2.79 - 5.71 + 0.1.
5. The process as claimed in claim 1, wherein the derived 'filler-modified
polyurethane emulsions' are coated on the surface of various vibrating or
noise generating part/s of any identified machine by spraying with a
pressure of about 70 psi and thereafter curing under ambiebt temperature,
pressure and humidity in order to obtain the desired level of thickness in
the coated layer.

6. The processes, as claimed in claim 1, wherein a 'bi-layer composite
structure' comprising melamine filler load with about 60 weight percentage
as the 'base coat' and barium sulphate filler with 60 percentage as the 'top
coat' respectively, maximizes acoustic attenuation effect.