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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a novel method for removal of oil or asphalt from
surfaces of inorganic particles having pigment in an outer layer thereof
with a non-chlorocarbon solvent comprising a mixture of monocyclic terpene
and aliphatic petroleum distillates. The method is especially applicable
to the deoiling of roofing granules having pigment in an outer ceramic
coating thereon.
2. Description of the Related Art
Inorganic particles having pigments present in an outer layer thereof, such
as naturally and artificially color-coated granules, are ubiquitous in the
roofing and siding industry. Exemplary applications thereof are in
granular surfaced bituminous roll roofing and asphalt shingles. The
granules, as partially embedded in one surface of asphalt-impregnated and
asphalt-coated fiber sheet material, form a coating to provide an
inherently weather-resistant and decorative exterior surface.
Typically, and as explained, e.g. in U.S. Pat. No. 3,528,842, colored
inorganic particles used as roofing and siding granules are manufactured
by coating a crushed mineral or rock granule substrate with a suitable
pigment to form a ceramic bond. The coating is formed from a solublized
silicate solution which is insolublized either by heat treatment or a
combination of heat treatment and chemical action to a substantially
water-insoluble state and is strongly adherent to the base granule. In
carrying out these methods the pigment is typically uniformly applied to
the granular surface with the soluble silicate solution, and the silicate
is insolubilized as noted above in the presence of an acidic material or
clay. Other patents which are representative of the state of the art in
making pigmented granules include U.S. Pat. Nos. 2,111,131; 3,255,031 and
3,507,676.
In any event, oil, such as naphthenic slate oil, is typically used during
the production of such roofing granules as a carrier for treatments, e.g.
as an adhesion medium, and for dust-suppression. This oil temporarily
remains on the surface portions of the finished roofing granules after
processing is completed. This residual surface oil often can effectively
change the color or chroma of the granules. However, the oil is eventually
removed from the granules as a result of natural weathering once the
granules are put into service and exposed to the elements. This loss of
oil effects an apparent color change in the granules, which is
instrumentally and visually discernible. This color change can occur in a
relatively short period of time once the granules are put into service,
e.g. after only two weeks to three months.
As can be understood, the deoiled color of the granules is of greater
interest and relevance to all concerned in selecting a color of granule to
be put into service than the temporary oiled color as it represents the
ultimate permanent color of the shingled roof, and the like.
Therefore, for quality control in the roofing industry, manufacturing
specifications for granule color are determined industry-wide on a
"deoiled" basis of the production samples of colored granules. Techniques
for removing oil from the granules have been proposed and used in the
field. Since it is inefficient for a roofing granule manufacturer to use
natural weathering to ascertain the deoiled color of a particular produced
batch of granules, organic solvents typically have been used to readily
remove oil from production samples of granules to determine their deoiled
color and ascertain whether such conforms to industrial standards on color
grades before the product is released into the market.
For instance, one widely-accepted procedure for determining the true color
or deoiled color of produced granules involved the use of a chlorocarbon
solvent, namely 1,1,1-trichloroethane. For example, in one standard
procedure using 1,1,1-trichloroethane as a deoiler for pigmented roofing
granules, a sample of oiled granules was first screened to Tyler mesh size
-14/+20 (US Standard -16/+20). The screened sample was then placed in a
100 milliliter beaker, the granules filling up to 50 milliters of a
beaker. The beaker was then filled to the rim with 1,1,1-trichloroethane.
The granules and 1,1,1-trichloroethane were then allowed to sit
undisturbed for about five minutes. The granules and trichloroethane were
then poured into a deoiling funnel and the solvent drained without
stirring into a one gallon can. Next, the funnel was filled with distilled
water to the rim and stirred while draining, being sure to collect all
solvent and water for proper disposal. The remaining granule samples in
the funnel were placed on a white paper towel and dried in a vented oven.
As to the temperature of the drying oven, temperatures ranging from about
80.degree. C. to about 110.degree. C. are suitable, and the samples merely
needed to be taken out when dry. However, the temperature of the drying
oven also could be set at 150.degree. C. Finally, the dried granules were
cooled on paper towels to room temperature on a table top prior to making
any color determinations. Then, to analytically determine the color of the
deoiled granules, the granules preferably have a L*a*b* delta compared
with a standard granule of +/-1.0.
The L*a*b* color space test is discussed in greater detail herein. Briefly,
a sample of deoiled granules is placed in a machine fitted with a defined
light source and the reflectance from the sample recorded on three
different color scales according to the "opponent-colors" scales. The
opponent color scales give measurements of color in units of approximate
visual uniformity throughout the color solid. In general, "L*" measures
lightness and varies from 100 for perfect white to zero for black,
approximately as the eye would evaluate it. The parameters "a*" and "b*",
the chromatacity dimensions, give understandable designations of color as
follows: a* measures redness when plus, gray when zero and greenness when
minus; b* measures yellowness when plus, gray when zero and blueness when
minus.
However, the past use of chlorocarbons solvents, and especially
1,1,1-trichloroethane, for deoiling granules, although satisfactory and
widely used for deoiling per se, now has serious drawbacks. As now widely
acknowledged, chlorocarbons contribute to the depletion of the earth's
ozone layer. In fact, international committments have been made under the
Montreal Protocol to phase out the production and use of chlorocarbons.
Therefore, industries have been urgently seeking effective alternatives to
the obsolescent chlorocarbons, including chlorocarbon solvents such as
1,1,1-trichloroethane.
However, the roofing granule industry has acquired a substantial body of
knowledge and experience on the deoiling action and color space test
attributes of pigmented inorganic particles deoiled by
1,1,1-trichloroethane. Therefore, it would be highly desired and less
traumatic for the roofing and siding particle industry if a replacement
could be identified for 1,1,1-trichloroethane which not only correlates
well with natural weathering but which also has deoiling performance akin
to its predecessor 1,1,1-trichloroethane.
In general, a large number of substitutes for chlorocarbon liquid solvents
have been proposed in recent times. For instance, T&R Chemicals Inc.
proposes certain para-menthadienes formed in a process from pine tree
turpentine as a solvent material, designated MSOL, as general substitute
for chlorocarbon solvents. This MSOL solvent, in turn, is said to be an
effective alternative to a competing non-chlorocarbon solvent of citrus
limonene (d-limonene) produced in the orange juice processing industry,
which, in some cases, depending on the predilections and olfactory
sensitivity of the user, is characterized as having a strong overpowering
odor.
Also, Bush Boake and Allen, a Union Camp Corporation, has advertised a
solvent designated BBA Solvent 401 (or 411) as a terpene-derived solvent
specifically designed for use in a newly-developed cleaning process for
electronic and precision engineering components, which is said to be an
environmentally responsible alternative to the use of CFC's and
chlorinated hydrocarbons. This company also advertises a solvent
designated BBA Solvent K102, which is said to be a proprietary degreasing
mixture of terpene hydrocarbons (p-menthadienes) and terpene alcohols
useful for a wide range of industrial cleaning processes with low
environmental impact.
Another solvent that is touted as containing no chlorinated hydrocarbons or
petroleum distillates is designated ZEP BIG ORANGE.TM., a naturally
occurring citrus solvent made by Zep Manufacturing Company. ZEP BIG
ORANGE.TM. solvent is said to be an industrial degreaser for motors,
engine parts, etc. and industrial parts, a tar and asphalt emulsifier, a
good cleaner for unpainted concrete which may damage painted surface and
an excellent grafitti remover. Another solvent advertised by Zep
Manufacturing Company as having no chlorinated solvents such as
1,1,1-trichlorethane is ZEP C-SOLV.TM., which is said to be useful for
degreasing operations such as tank cleaning and electric motors.
Also, West Penetone advertises a safer degreaser than 1,1,1-trichloroethane
designated CITRIKLEEN.RTM. XPC, which is non-chlorinated and nonpetroleum
based, and said to be used for removal of carbon black, graphite,
liquified polymers, tar, asphalt, greases and oils from hard metal and
non-metal surfaces.
PT Technologies, Inc. advertises a solvent designated PF.TM. Degreaser as a
replacement for harmful solvents such as 1,1,1-trichloroethane, freon,
methyl ethyl ketone, acetone, mineral spirits. PF.TM. Degreaser is said to
be useful for industrial applications where a 100% volatile solvent is
preferred and can be used to remove hydrocarbon, silicone, or polyethylene
based greases, oils, tars and gels. The PF.TM. Degreaser solvent is said
to have passed common carrier aircraft metals compatibility testing, and
is said to be safe to use prior to painting, and on painted surfaces.
However, the deoiling action that any given solvent may have on a pigmented
ceramic-coated granule is highly unpredictable. That is, the solvent used
must deoil the surface regions of granules in a relatively consistent
repeatable manner, e.g., in terms of the color space test readings taken
on the deoiled granules, and without freeing or leaching pigments from the
granules or otherwise permanently disturbing the unique and specific
morphology and composition of the granules and their surface coating(s).
Importantly, the deoiling effected by the solvent used to deoil the
granules must correlate well with deoiling caused by natural weathering in
order to provide an accurate and reliable predetermination of whether the
pigmented granules are either inside or outside industry specifications.
Also, the solvent must be relatively safe to handle such as in terms of
its flammability, noxiousness and pungency.
None of the above literatures specifically describe an application of a
nonchlorocarbon solvent towards meeting the peculiar requirements arising
in and associated with deoiling pigmented inorganic particles, and
especially pigmented ceramic-coated inorganic particles for grading
purposes, and the industry has urgently awaited for and would place value
on such a discovery.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method to deoil
inorganic particles having pigments in at least the outer surfaces thereof
with a solvent which does not disturb the surface morphology, pigments
therein or composition of the particles, has acceptable pungency from
health and safety standpoints, and which deoils the particles in a
consistent manner which correlates well with natural weathering and the
action of obsolescent chlorocarbon solvents such as 1,1,1-trichloroethane.
Among other things, a deoiling action is desired which correlates well
with natural weathering and 1,1,1-trichloroethane in the sense of oil
removal and color space test values, such as described herein, as taken on
the deoiled particulate.
It is another object of the present invention to provide a method to deoil
pigmented inorganic particles having oily residues on surfaces thereof to
determine whether the pigmented inorganic particles, especially roofing
granules and the like, meet industry color specifications. It is yet
another object to provide a method to provide ready-to-use deoiled
pigmented inorganic particles.
These and other objects of the present invention have been attained by the
present inventors' discovery of a method for removing oil residues from
surfaces of inorganic particles each having pigment in an outer layer
thereon, comprising contacting the surfaces with a deoiling solution
comprising a mixture of monocyclic terpene and aliphatic petroleum
distillates in an amount and manner effective to wet substantially all the
surfaces of the inorganic particles, whereby the deoiling solution removes
substantially all the oil residues from the surfaces of the inorganic
particles.
In a preferred embodiment, this invention relates to a method for removing
oil residues from surfaces of inorganic particles each having pigment in
an outer layer thereon, comprising the steps of:
(a) providing a structure having a wall portion which defines a receptacle,
the wall portion including an upper wall portion which includes a first
opening for introducing inorganic particles into the receptacle, a lower
wall portion having a second opening therethrough for discharging liquids
from the receptacle, the structure including a porous support member
having a pore size which permits the passage of liquid but not the
inorganic particles located in the receptacle between the first opening
and the second opening to define a particle holding chamber;
(b) introducing an amount of the inorganic particles, without compacting,
into the particle holding chamber of the receptacle at the first opening,
whereby the inorganic particles are supported on the porous support
member;
(c) introducing a deoiling solution comprising a mixture of monocyclic
terpene and aliphatic petroleum distillates into the first opening in an
amount and manner effective to flow downward through interstices between
the inorganic particles to contact and wet substantially all the surfaces
of the inorganic particles, whereby the deoiling solution removes the oil
residues from the surfaces of the inorganic particles and flows out of the
second opening;
(d) then, introducing water into the first opening to rinse the deoiled
inorganic particles; and
(e) drying the rinsed inorganic particles at a temperature and for a
duration effective to volatize substantially all residual deoiling
solution and water from the surfaces of the inorganic particles.
In a preferred embodiment, the above-mentioned method uses a deoiling
solution comprising d,l-limonene as monocyclic terpene in an amount of
from about 10% to 30%, by weight, and 100% aliphatic petroleum distillates
in an amount of from about 90% to 70% by weight, based on total weight
deoiling solution.
For purposes of the present invention, a "monocyclic terpene" means a
one-ring terpene structure, and its saturated or partially saturated
isomers, as well as its derivatives, e.g., alcohols, aldehydes, and
esters. In a more preferred embodiment, the monocyclic terpene usable in
the present invention is that as defined in CAS# (Chemical Abstracts
Service No.) 5989-27-5, which indicates d,l-limonene.
For purposes of the present invention, "aliphatic petroleum distillates"
are generally defined as a highly complex mixture of aliphatic paraffinic
and cycoparaffinic (naphthenic) hydrocarbons derived from cracked or
distilled petroleum, such as a mixture of any of naptha of several grades,
gasoline, kerosene, fuel oils, gas oil, lubricating oils, paraffin wax and
asphalt. More specifically, the "aliphatic petroleum distillates"
preferred in the present invention are those as defined in CAS# (Chemical
Abstracts Service No.) 64771-28-8.
In another preferred embodiment of the invention, the receptacle which
supports the grains during the deoiling processs is selected to be a
conical funnel structure.
In yet another embodiment, the invention relates to a method for deoiling
oil residues from surfaces of inorganic particles each having pigment in
an outer layer thereon and determining the color grade thereof,
comprising:
(a) providing a structure having a wall portion which defines a receptacle,
the wall portion including an upper wall portion which includes a first
opening for introducing inorganic particles into the receptacle, a lower
wall portion having a second opening therethrough for discharging liquids
from the receptacle, the structure including a porous support member
having a pore size which permits the passage of liquid but not the
inorganic particles located in the receptacle between the first opening
and the second opening to define a particle holding chamber;
(b) introducing an amount of the inorganic particles, without compacting,
into the particle holding chamber of the receptacle at the first opening,
whereby the inorganic particles are supported on the porous support
member;
(c) introducing a deoiling solution comprising a mixture of monocyclic
terpene and aliphatic petroleum distillates into the first opening in an
amount and manner effective to flow downward through interstices between
the inorganic particles to contact and wet substantially all the surfaces
of the inorganic particles, whereby the deoiling solution removes the oil
residues from the outer surfaces of the inorganic particles and flows out
of the second opening;
(d) then, introducing water into the first opening to rinse the deoiled
inorganic particles;
(e) drying the rinsed inorganic particles at a temperature and for a
duration effective to volatize substantially all residual deoiling
solution and water from the outer surfaces of the inorganic particles;
(f) performing a L*a*b* color analysis on the deoiled particles; and
(g) comparing results of the L*a*b* color analysis against the industry
specification applicable to the pigmented inorganic particles.
The invention itself, both as to its method of application and its support
technology, together with additional objects and advantages thereof, will
be better understood from the following description of the preferred
embodiments of the present invention.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a side perspective view of a deoiling receptacle of the present
invention having a funnel structure, where the hatched lines indicate
hidden features.
FIG. 2 depicts .DELTA.L* color data obtained for oiled to deoiled 4100-type
brown roofing granules, which were deoiled in separate tests by
1,1,1-trichloroethane and the deoiling solvent used in the present
invention, as described in Example 2 herein.
FIG. 3 depicts .DELTA.a* color data obtained for oiled to deoiled 4100 type
brown roofing granules, which were deoiled in separate tests by
1,1,1-trichloroethane and the deoiling solvent used in the present
invention, as described in Example 2 herein.
FIG. 4 depicts .DELTA.Ab* color data obtained for oiled to deoiled
4100-type brown roofing granules, which were deoiled in separate tests by
1,1,1-trichloroethane and the deoiling solvent used in the present
invention, as described in Example 2 herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Deoiling Solvent
In a preferred embodiment, the deoiling solvent comprises a blend of
monocyclic terpene in an amount of from about 10% to 30%, by weight, and
aliphatic petroleum distillates (100% aliphatic) in an amount of from
about 90% to 70% by weight, based on total weight deoiling solution.
A suitable source of the above deoiling solvent blend material is available
from PT Technologies, Inc., Safety Harbor, Fla., and is designated as
PF.TM. Degreaser (Category A: 100% volatile solvent ingredients). The
Canadian distributor of PF.TM. Degreaser, AMAC Equipment, Ltd., describes
the PF.TM. Degreaser, in Material Safety literature, as comprising up to
90% by weight 100% aliphatic petroleum distillates (100% aliphatic) {CAS#
64771-28-8} and up to 30% by weight monocyclic terpene hydrocarbon
{CAS#5989-27-5}. Preferably, the amount of monocyclic terpene constitutes
from about 10% to 30% by weight of the total deoiling solvent blend used
in the present invention.
The use of higher amounts of the monocyclic terpene, e.g. d,l-limonene,
such as greater than 30% by weight of the total solvent blend, may be
unacceptable from a health and safety standpoint as the compound is
classified as combustible. Care should be taken to perform the deoiling
method of the present invention in a ventilation hood as a precaution. On
the other hand, if the amount of monocyclic terpene is below 10% by
weight, insufficient deoiling action might occur, depending, in part, on
the particular type of slate oil being removed. In any event, a
satisfactory blending ratio of d,l-limonene and aliphatic petroleum
distillates can be determined empirically by the skilled technician to
suit the materials at hand.
As to physical properties, the PF Degreaser has a vapor pressure less than
1 mm Hg at 25.degree. C.; a vapor density greater than 1 (wt/vol where
air=1); a specific gravity of 0.75; a flashpoint of 62.degree. C.; a
boiling point of 193.degree.-221.degree. C. and upper and lower
flammability limits of 7% and 0.6% by volume, respectively; and is a clear
liquid described as having a faint citrus odor.
The deoiling solvent, as described herein, used in the present invention is
effective, in general, to remove naphthenic slate oils, silicone oils,
paraffinic oils, phenolic oils and asphalt from the surfaces of the
inorganic particles. The amount of solvent used in the deoiling procedure
is not particularly limited. In general, the amount of solvent can be that
which is sufficient to deoil the granules treated with an effective or
reasonable amount of slate oil for conventional purposes such as dust
suppression; that amount being known by those skilled in the art. In
general, amounts of slate oil for roofing granules, and the like, of up to
about 20 lbs oil/ton inorganic particles (up to about 0.1 and 10 kg/metric
ton) are satisfactorily removable by the deoiling method of the present
invention. Freshly manufactured roofing granules, for example, typically
will have about 1 to 20 lbs. oil surface residue/ton of granules (about
0.5 to 10 kg oil surface residue/metric ton of granules).
Inorganic Particles
The pigmented inorganic particles or granules applicable to this invention
generally comprise a substrate of porous mineral or rock having at least
one outer layer containing a pigment. For example, the outer layer can
comprise a ceramic coating containing at least an insolubilized silicate
and the pigments. The inorganic substrate granules of the inorganic
particles applicable to the invention are conventional and can be from any
one of a rather wide class of relativley porous and weather resistant rock
and minerals. Examples of relatively porous materials are trap rocks and
slates. Examples of relatively porous and non-porous rocks and minerals
are argillite or greystone (such as the large greystone deposits locayed
north of Wausau, Wisconsin), greenstone, certain granites and the like.
These substrates have substantial porosity as compared to a typical
ceramic coating provided on the inorganic substrate.
Representative inorganic particles applicable to the invention, include
ceramic-coated granules which are coated with a suitable pigment in an
inorganic bond, such as described in U.S. Pat. Nos. 3,528,842 to Skadulis;
3,507,676 to McMahon and 3,255,031 to Lodge et al. These references
encompass clay-silicate coated pigmented particles and
borate-clay-silicate coated pigmented particles. These types of ceramic
coated particles can have multiple ceramic coatings formed on the
substrate granule, e.g. 1-3 layers, with a pigment selected to render the
desired color as added to any of the ceramic coating layers.
Known pigments for these inorganic particles include carbon black, titanium
dioxide, chromium oxide, yellow iron oxide, phthalocyanine green and blue,
ultramarine blue, red iron oxide, metal ferrites, and mixtures thereof. In
general, the amount of pigment added is that sufficient to coat and color
the particle surface. However, the exact amount of pigment will depend on
many variables including the color desired and the presence of heavy
additives such as cuprous oxide; although, e.g., 20 to 140 lb pigment/ton
of inorganic particles (10 to 70 kg/metric ton) may be a generally
representative range amount. The ceramic coatings also may contain an
algicidal copper compound, such as cuprous oxide, such as described In
U.S. Pat. No. 3,528,842. Though not the particular subject of the present
invention, suitable techniques for forming such pigmented ceramic coatings
on inorganic particles are widely known and practiced in the field.
More relevant to the present invention, prior to the use of the
above-described ceramic coated inorganic particles, the pigmented
particles usually are treated to reduce dust generation during processing
and to improve adhesion to the materials used in a backing support sheet,
e.g. a bituminous asphalt sheet material in the case of roofing granules.
Typical treatments, include oil treatments, such as silicone oils which
help in wicking of pigment into the granule, and, traditionally,
naphthenic slate oil has been utilized for dust control and as an adhesion
medium between the granule and asphalt.
As explained previously, for quality control, ultimate exposed color of the
pigmented inorganic particle is the most critical feature; therefore, the
exposed color must be assimilated through a deoiling process. The deoiling
procedure of the present invention can use the following equipment and
method of operation.
Deoiling Receptacle
Preferably, the receptacle used in the present invention has a
configuration which tapers inward from an upper opening at the top of a
walled structure towards a lower opening at the bottom thereof, wherein a
screen member is located inside the funnel between the two openings. More
preferably, the receptacle has a conical funnel structure to provide an
optimal flow profile for the solvent through the inorganic particles. More
specifically, the conical funnel structures of this invention can be
characterized as having a frustum shape, wherein the upper opening is
circular and can be considered as the cone base while the lower opening
can be considered as within an imaginary plane which cuts the side edges
of a cone below the apex thereof. Therefore, a conical structure of the
receptacle of the invention has a circular upper opening having a larger
diameter than the circular lower opening whereby the side edges of the
structure smoothly taper inward from the upper opening to the lower
opening through a series of successively smaller circular cross-sections.
For example, the receptacle can comprise a regular conical funnel structure
1, as depicted in FIG. 1, having the first opening 2 at the upper wall
portion 7 thereof for introducing the inorganic particles (not shown)
having a diameter of about 7 cm, and a second opening 3 at the lower wall
portion 8 thereof for draining the solvent (not shown) having a diameter
of about 0.4 cm, and a support member 4, such as a screen support, located
inside the funnel in-between the two openings at about 3.2 cm above the
second opening and about 5.8 cm below the first opening, and the diameter
of the funnel at the location of the screen support is about 3.2 cm. The
apertures (not shown) in the support support member have a size that is
greater than 425 .mu.m but less than 710 .mu.m (-24/+40 U.S. standard
sieve mesh size) with the proviso that they are smaller in size than the
inorganic particles to permit passage of liquid but not the inorganic
particles.
In one embodiment, the support member can be arranged as extending
horizontally across the interior of the receptacle, and preferably entends
across an entire cross-sectional are of the receptacle to further ensure
that no oily particles inadvertently fall out of the receptacle through
the lower opening during the introduction of the inorganic particles into
the receptacle, or during deoiling or rinsing. As to the geommetry of the
apertures, square openings in a mesh-like screen structure are
conveniently used. However, the geommetry of the aperture is not
necessarily limited thereto. For instance, circular openings also can be
used. The aperture size can range from greater than 425 .mu.m to less than
710 .mu.m.
By way of example, and also by reference to FIG. 1, the total volume of a
conical shaped receptacle of the invention, such as described herein
above, can be about 130 cm.sup.3, and the volume of holding chamber
compartment 5 for the inorganic particles, as measured as the volume space
delimited by the upper surface of the support member, interior side walls
of the funnel and upper opening of the receptacle, can be about 120
cm.sup.3, and the volume of the drainage compartment 6 below the support
member, as measured as the volume space delimited by the lower surface of
the support member, interior side walls of the funnel and lower opening of
the receptacle can be about 10 cm.sup.3.
Other funnel geommetries, such as rectangular funnel or spheric, also are
within the scope of the invention.
Deoiling Protocol
The inorganic particles to be deoiled usually are first mesh-screened to a
size of at least greater than the aperture sizing in the screen member
housed in a funnel-configured receptacle, such as described herein.
Although screening of the oily particles before deoiling is not essential
to the successful exercise of the invention, if a spectroco | | |
