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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to elastic metallized decorative moldings
composed of a modified polyurethane resin as a substrate coated on the
surface thereof with a metallized layer. More particularly, the present
invention relates to elastic metallized decorative molded articles useful
as impact-absorbing materials in which a metallized layer is coated on the
surface of an elastic substrate composed of a specific plastic
polyurethane resin modified with an AS or ABS resin in a specific
proportion.
In recent years, elastic decorative moldings made of an elastic synthetic
resin have been mounted in place of rubber moldings on bumpers and side
exterior walls of motor vehicles for the purpose of not only protecting
the motor vehicles from damage caused by external impact but also
improving aesthetic value in appearance. Accordingly, resinous materials
for such elastic decorative resin moldings are naturally required to be
excellent in impact-resistance, self-redintegration in shape and size,
strength, abrasion resistance and the like properties. As motor vehicles
are exposed under severe weathering conditions, the resinous materials are
also required, as a matter of course, to be satisfactory in
heat-resistance and cold-resistance. From the economical point of view,
the resinous materials are further required to be suited for processing by
injection molding or extrusion molding operations generally adopted as
advantageous means for mass production.
Hitherto used elastic decorative moldings having metallic appearance for
motor vehicles are (A) soft polyvinyl chloride moldings provided on the
surface thereof with a multi-layer film of polyvinyl fluoride (top
protective layer)-aluminum vapor deposited on polyethylene terephthalate
(metallized layer)-polyvinyl chloride (undercoat layer) or with a thin
layer of stainless steel by the aid of a binder or (B) vulcanized rubber
moldings provided on the surface thereof with a thin metal layer by vacuum
deposition. However, these prior art products have many drawbacks in
practical use. In case of the product (A), disfigurement tends to remain
on the surface when the product is significantly deformed, and moreover,
either of cold-resistance and heat-resistance of the substrate becomes
poor according to the proportion of a plasticizer incorporated into the
polyvinyl chloride substrate. In case of the product (B), vacuum
deposition of a metal is disturbed considerably by evaporation of
processing oils, plasticizers and the like ingredients incorporated into
the vulcanized rubber substrate so that the luster of the metal deposited
is lost or adhesiveness of the metal film to the substrate becomes
extremely poor. For overcoming these drawbacks, an improved process is
proposed wherein melamine, alkyd resin or the like paint is applied onto
the surface of the rubber substrate to form a migration-preventing layer
by which evaporation of ingredients incorporated into the substrate is
prevented. However, the products obtained according to this improved
process still have shortcomings, in that the metal film is cracked or
delaminated on deformation of the products because of poor adhesiveness
between the substrate and the migration-preventing layer or poor
flexibility of the migration-preventing layer. Thus, polyvinyl chloride,
natural and synthetic rubbers are found to be unsatisfactory as the
substrate for elastic decorative moldings for motor vehicles.
On the other hand, other elastic resins such as polyurethane alone or as a
mixture with ABS or AS resin come into question as the elastic substrate.
However, known compositions comprised of polyurethane and ABS or AS resin
disclosed in Japanese Patent Publn. Nos. 19492/61 and 659/71 are also
found to be unsatisfactory as the substrate for elastic decorative
moldings for automobiles since these compositions are extremely poor in at
least one of the several severe conditions as required for motor vehicles.
Thus, an important key to overcoming the drawbacks of the prior art
elastic decorative moldings is to use a special resinous material as
substrate which can satisfy all of the above mentioned necessary physical
properties. Hence, there is a great demand for development of a new
resinous material which satisfies the severe conditions as required for
motor vehicles when it is used as substrate for elastic decorative
moldings.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide elastic
metallized decorative moldings which overcome the drawbacks above
mentioned.
It is another object of the present invention to provide elastic metallized
decorative bumper moldings for motor vehicles.
It is still another object of the present invention to provide the use of a
new modified thermoplastic polyurethane resin as substrate for elastic
metallized decorative moldings.
Other and further objects, features and advantages of the present invention
will become apparent more fully from the following description.
DETAILED DESCRIPTION OF THE INVENTION
As a result of extensive research made on elastic resins as substrates and
on methods for furnishing the substrates with durable metallic luster for
overcoming the drawbacks of the known elastic metallized decorative
moldings, it has now been found that new improved elastic metallic
decorative moldings which are excellent in both heat-resistance and
cold-resistance and are restorable to the original shape and size without
retaining any damage even when significantly deformed can be obtained by
using a specific thermoplastic polyurethane resin as substrate and
processing the surface thereof with a metallized layer or a
metal-containing paint. The present invention has been accomplished on the
basis of the above finding.
In accordance with the present invention, there are provided elastic
metallized decorative moldings composed of a modified polyurethane resin
as a substrate coated on the surface thereof with a metallized layer, the
polyurethane resin comprising 50-95 parts by weight of a thermoplastic
polyurethane resin incorporated with 5-50 parts by weight of an
acrylonitrile-butadiene-styrene resin comprised of at least 75% by weight
of an acrylonitrile-styrene component and not more than 25% by weight of a
butadiene component.
In the elastic metallized decorative moldings of the present invention, the
thermoplastic polyurethane resin is derived from (a)
poly(pentamethylenecarbonyloxy) glycol having an average molecular weight
of about 1800-2200 or (a') polytetramethylene adipate glycol, (b)
tetramethylene glycol in an amount of 2.5-4.5 mols per mol of the
ingredient (a) or (a'), and (c) diphenylmethane-4,4'-diisocyanate in a
molar amount corresponding to the total mols of the ingredients (a) or
(a') and (b) used. The ingredient (a), poly(pentamethylenecarbonyloxy)
glycol, can be prepared by decyclic polycondensation of
.epsilon.-caprolactone, while the ingredient (a'), polytetramethylene
adipate glycol, can be prepared by esterification of tetramethylene glycol
with adipic acid. The preparation of these ingredients (a) and (a') can be
carried out according to a usual method known per se. The thermoplastic
polyurethane can be synthetized by reacting given amounts of these
ingredients (a) or (a'), (b) and (c) together according to a usual method
well known in the art of preparing polyurethanes. The use of a
thermoplastic polyurethane resin derived from polytetramethylene adipate
glycol, tetramethyleneglycol (butane-1,4-diol) and
diphenylmethane-4,4'-diisocyanate, i.e. the ingredients (a'), (b) and (c)
is preferable in the present invention.
The acrylonitrile-butadiene-styrene resin to be incorporated as modifier
into the thermoplastic polyurethane resin to prepare the modified
polyurethane resin is composed of at least 75% by weight of an
acrylonitrile-styrene component and not more than 25% by weight of a
butadiene component and is generally called "ABS resin" or "AS resin" (in
case the content of the acrylonitrile-styrene component is 100% or in
other words the content of the butadiene component is 0%). The
acrylonitrile-butadiene-styrene resin preferably has a molecular weight
within the range from 50,000 to 150,000 and a composition of 10-30 wt.%
acrylonitrile, 45-90 wt.% styrene and 0-25 wt.% butadiene and is easily
commercially available or can be prepared in a manner known per se.
The modified polyurethane resin used in the present invention as substrate
can easily be manufactured by incorporating the thermoplastic polyurethane
resin with the acrylonitrile-butadiene-styrene resin, for example, by
mixing given amounts of these ingredients in powdery or pelletized form,
e.g. in an ordinary mixer and then melting and kneading the mixture at
180.degree.-220.degree. C. by the aid of mixing rolls, a mixing extruder
or an internal mixer.
In the present invention, the proportion of the modified polyurethane resin
to the acrylonitrile-butadiene-styrene resin is limited within the range
from 95:5 to 50:50 on weight basis so as to furnish the substrate with
desired physical properties. If the proportion of the modified
polyurethane resin exceeds 95:5, the heat-resistance of the substrate will
be reduced so that the substrate will incur sagging on molding at high
temperatures by extrusion or injection and will be susceptible to
deformation at a high temperature. On the other hand, if the proportion of
the modified polyurethane resin is less than 50:50, the substrate will
become rigid and brittle so that it will be cracked when deformed and its
cold-resistance, weather resistance and restorability to the original
shape and size will seriously be reduced. A preferable proportion of the
modified polyurethane resin to the acrylonitrile-butadiene-styrene resin
is within the range from 80:20 to 60:40.
According to the present invention, the modified polyurethane resin is
molded into a desired shape, e.g. a bumper molding, by injection or
extrusion through a complicately figured extrusion die. The injection
molding or extrusion molding in this case is performed according to well
known methods. A substrate having a composite structure is thus
manufactured from the modified polyurethane resin.
The substrate thus obtained is then subjected to a metallizing treatment to
apply a thin layer of a metal or an alloy or of a metal-containing paint
onto the surface of the substrate. No limitation is set for the sort of
metals and alloys to be used for the metallizing treatment but aluminum,
stainless steel, Ni-Cr, copper, copper alloys, and the like are preferably
used. The metallizing treatment of the substrate is carried out by a
variety of known conventional methods, for example, by applying a
metal-containing paint or by means of vacuum deposition, ion-plating,
spattering, hot-stamping, electroplating or spray-plating, among which
vacuum deposition, spattering, ion-plating and application of a
metal-containing paint are preferable. In view of similarity in mechanism,
"spattering" and "ion plating" are often involved in the term "vacuum
deposition" in a broader sense of the meaning. Accordingly, the term
"vacuum deposition" is used herein to generally mean "spattering" or "ion
plating" in addition to the inherent meaning of "vacuum deposition". A
thin film of a metal, an alloy or a metal-containing paint (sometimes
called "metallic paint") thus formed on the substrate is usually
overcoated with a top protective film which has generally strong
weather-resistance. As a rule, polyvinyl fluoride is suited as a material
for such protective film.
According to an alternative preferred method for matallizing treatment, the
substrate is overlaid with a multi-layer film composed of polyvinyl
fluoride or chloride top coat/a metal vacuum deposited polyethylene
terephthalate intermediate coat/a vinylic resin under coat. In this case,
there is no necessity of further providing a protective film on the
multi-layer film.
The structure of the elastic metallized decorative moldings of the present
invention will be explained in more detail hereunder in the light of the
accompanying drawings in which:
FIG. 1 is a diagram schematically showing the section of the surface of one
example of the elastic metallized decorative moldings of the present
invention.
FIG. 2 is a diagram schematically showing the section of the surface of
another example of the elastic metallized decorative moldings of the
present invention.
FIG. 3 is a schematic sectional view of a bumper molding as one embodiment
of the present invention.
In FIG. 1 is schematically shown the section of the metallized layer of the
decorative molding obtained by applying a multi-layer film onto the
surface of the substrate. The substrate 1 is overlaid with a multi-layer
film composed of a vinylic resin film 2, vacuum deposited aluminum film 3,
polyethylene terephthalate film 4 and polyvinyl fluoride or transparent
soft polyvinyl chloride 5 in such a manner that the surface of the
substrate 1 is faced to the surface of the vinylic resin film 2.
In FIG. 2 is schematically shown the section of the metallized layer of the
decorative molding obtained by applying a thin metal film by means of
vacuum deposition in a broader sense involving spattering. The substrate 1
is coated with a base coat 6, a thin metal film 7 and a top coat 8
successively in the prescribed order. In case a metallic paint is used for
the metallizing treatment, the above metal film 7 is replaced by the
metallic paint film. The base coat 6 and the top coat 8 are preferably
applied in the same manner as in FIG. 1 but these coats 6 and 8 may be
omitted, if desired. The term "metallized layer" is used herein to mean
generally the thin metal film or the thin metallic paint film alone or in
combination with the other films such as the base coat film and the top
coat film.
The elastic metallized decorative moldings of the present invention are not
only excellent in cold resistance, heat resistance, flexibility and
restorability to the original shape and size without any disfigurement
even when deformed significantly but also advantageous in that the
decorative moldings can easily be manufactured by extrusion molding or
injection molding in contrast to the case of known thermoplastic
polyurethane resins which can hardly be processed by extrusion molding or
injection molding. In the products obtained by applying a multi-layer film
onto the substrate, the surface of the film is substantially free from
disfigurement even in case of deformation and the adhesiveness between the
substrate and the multi-layer is extremely good, because the substrate is
excellent not only in cold resistance and heat resistance but also in
combination of hardness and elongation and because adhesiveness between
the substrate and the vinylic resin is excellent. In the products obtained
by means of vacuum deposition or spattering, the products have brilliant
metallic luster of transparent feeling in addition to the above mentioned
excellent physicochemical properties, since no substance evaporates under
vacuum. In the products obtained by application of a metallic paint such
as one having metallic silver tint, adhesiveness between the paint film
and the substrate is excellent in addition to the remarkable merits above
mentioned.
As the elastic metallized decorative moldings of the present invention have
strong resistance to various corrosive attacks such as weathering and
chemical actions, the moldings are hardly susceptable to "whitening"
generally caused by degradation of the resinous materials and oxidation of
the metal applied so that the metal film itself or metal paint film can
keep its brilliant luster for a prolonged period of time.
The present invention is especially valuable in making it possible to
provide for the first time practically attractive elastic moldings with
durable metallic luster. Accordingly, the moldings of the present
invention are particularly suited as parts of motor vehicles and similar
transporting vehicles, such as bumper moldings, side moldings, step
moldings, lamp moldings and luggage moldings. Besides this, the moldings
of the present invention find various applications, for example, indoor
and outdoor ornaments, buffer materials, shock-absorbers, sporting goods
and parts of machines, such as slip-preventing strips, belts, packings,
protecting guard, soles of shoes, and the like. The moldings of the
present invention can be mounted or fixed to objects by the aid of a
binder, a dual-adhesive tape, clips or bolts and nuts or by means of
insertion.
The present invention will now be illustrated in more detail by way of the
following examples.
EXAMPLE 1
A mixture of 30 parts by weight of ABS resin composed of 15% by weight of a
butadiene component and 85% by weight of an acrylonitrile-styrene
component and 70 parts by weight of a thermoplastic polyurethane resin
derived from polytetramethylene adipate glycol having a hydroxyl number of
37.0, an acid number of 0.4 and a molecular weight of about 3000,
1,4-butanediol and diphenylmethane-4,4'-diisocyanate was prepared to form
a modified polyurethane resin. Table 1 shows physical characteristics of
this modified polyurethane resin.
TABLE 1
______________________________________
Tensile strength (kg/cm.sup.2)
590
Fracture elongation (%) 500
100% Modulus (kg/cm.sup.2)
130
Tear strength (kg/cm) 145
Cold embrittlement temperature* (.degree.C.)
<-70
JIS Hardness (A) 96
______________________________________
*The test for measuring the cold embrittlement temperature was carried ou
according to JIS K6723. The testing methods for measuring the other
characteristics were carried out according to JIS K6301.
This modified polyurethane resin was molded by extrusion into a bumper
molding having a section as shown in FIG. 3. A multi-layer film containing
a metallized film was thermally welded on the surface of the bumper
molding. The resultant bumper molding was fixed onto the surface of a RIM
(reaction injection molding) polyurethane bumper. The following tests were
performed for test samples of the resulting product.
[Test Conditions and Evaluation Standards]
(1)Impact Test
(i) Front Impact with a pole*:
The front surface of the test sample (the bumper onto which the bumper
molding having the metallized layer had been fixed was struck two times
each with a pole* moving lengthwise at a speed of 8 km/hr.
*A pole with a semispherical tip having a radius of 150 mm on one hand
having an appearance of a long-stem mushroom was used in this impact test
in such manner that the front surface of the test sample (the RIM
polyurethane bumper having on the surface thereof the bumper molding) was
struck two times each with the semispherically round tip of the pole
moving lengthwise at a speed of 8 km/hr.
(ii) Corner impact with a flat panel:
A corner of the test sample was struck once at an angle of 30.degree. with
a flat panel at a speed of 5 km/hr.
Considerable deformation or formation of cracks should not be observed in
the sample test under the above conditions.
(2) High Temperature Oscillation Test
______________________________________
Temperature 80.degree. C.
Frequency 1500 cs/min
Oscilatory acceleration
3.5 G
Total number of oscilation
1,000,000
______________________________________
Imperfections in appearance such as serious waving and deformation should
not be observed in the sample tested under the above conditions.
(3) Heat Cycle Test
______________________________________
Temp.
(.degree.C.)
80 ord* -30 ord 50** ord -30 ord
Time
(hr) 15.5 0.5 7.5 0.5 15.5 0.5 7.5 0.5
______________________________________
*"ord" means ordinary (ambient) temperature.
**tested in a high humidity of 98%
Imperfactions in appearance such as deformation, discoloration or fading***
should not be observed in the sample after repeating the test 5 times
under the above conditions.
***Discoloration or fading in this case means all of the phenomena wherein
the metallic luster becomes cloudy or is decreased or lost, the tint of
the metallic paint is discolored or faded, and the color of the resinous
layers is changed or faded.
(4) Water Immersion Test
Immersion of the test sample in warm water maintained at 40.degree. C. for
240 hours.
Considerable discoloration or fading and delamination of the film should
not be observed in the sample tested under the above conditions.
(5) Salt Spray Test
Immersion of the test sample in a 5 wt.% NaCl solution maintained at
35.degree. C. for 240 hours after thermal aging of the sample at
90.degree. C. for 100 hours.
Rust should not be observed in the sample tested under the above
conditions.
(6) Abrasion Test
A reciprocally moving (2000 cycles) sailcloth was used as an abrasive
surface under a load of 500 g (Ford test).
Streaks or abrasion should not be significant in the sample tested under
the above conditions.
(7) Accelerated Weather-resistance Test
The test sample was subjected to accelerated degradation in a sunshine
weather-o-meter for 400 hours.
Considerable discoloration or whitening* should not be observed in the
sample tested under the above conditions.
*"whitening" is caused by both degradation of the resinous materials and
oxidation of the metal.
A result of these tests is shown in Table 2.
TABLE 2
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Test item Result obtained
______________________________________
Front impact
55.degree. C. .circle.
ordinary temperature
.circle.
-30.degree. C. .circle.
Corner impact
55.degree. C. .circle.
ordinary temperature
.circle.
-30.degree. C. .circle.
High temperature oscilation test
.circle.
Heat cycle test .circle.
Water immersion test .circle.
Salt spray test .circle.
Accelerated weather-resistance test
.circle.
Abrasion test .circle.
______________________________________
*Circle (.circle.) means passing the test.
EXAMPLE 2
A modified thermoplastic polyurethane resin was prepared from 20 parts by
weight of an acrylonitrile-styrene resin composed of 24% by weight of an
acrylonitrile component and 76% by weight of a styrene component and 80
parts by weight of the thermoplastic polyurethane resin used in Example 1.
Table 3 shows physical characteristics of this modified thermoplastic
polyurethane resin.
TABLE 3
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Tensile strength (kg/cm.sup.2)
570
Fracture elongation (%) 520
100% Modulus (kg/cm.sup.2)
115
Tear strength (kg/cm) 147
Cold embrittlement temperature (.degree.C.)
<-70
JIS Hardness (A) 96
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The testing methods for measuring the physical characteristics were
identical with those described in Example 1.
The modified polyurethane resin was subjected to extrusion molding to
obtain a bumper molding of the same size as described in Example 1. A two
component polyurethane paint was applied onto the surface of the bumper
molding by means of spray coating to form a paint film having a thickness
of about 10.mu.. The coated bumper molding was subjected to a compulsory
drying treatment conducted at 80.degree. C. for 1.5 hours. A Ni-Cr alloy
was then applied by the aid of a spattering device of DC magnetron type
[Model CFS-24PV-120B, Tokuda Seisakusho (Tokuda Mfg. Co.), Japan] onto the
surface of the bumper molding to form thereon a film of the alloy having a
thickness of about 250 A. The metallic film was further coated with a
non-yellowing two-component polyurethane paint as a protective top coat.
The product thus obtained exhibited excellent physical characteristics in
comparison with an ordinary metal-deposited bumper molding made of rubber,
as will be evident from Table 4. The bumper molding was fixed onto the
surface of a RIM polyurethane bumper to form a product Test samples of the
product were subjected to the same test as referred to in Example 1
whereby the test samples exhibited excellent properties for elastic
metallized decorative molded articles. A result of the test is shown in
Table 5.
TABLE 4
__________________________________________________________________________
Test Product of
Metal-deposited
Test item condition this invention
rubber molding
__________________________________________________________________________
Metal luster
observation with
Good Cloudy for
naked eyes opacified)
Adhesiveness
cross-cut adhesion
no lamination
Partially delami-
test (100/100)
nated (70/100)
Flexibility 15 mm .PHI. no crack
Cracks formed
Warm water resistance
40.degree. C., 400 hrs
no change
Delaminated
Heat resistance
80.degree. C., 400 hrs
" "
Humidity and heat
50.degree. C., 95% RH, 400 hrs
" "
resistance
Abrasion test
Tabor, 1000 r.
" Substrate exposed
Cold flexibility
-20.degree. C., 15 mm .PHI.
" Cracks formed
Cold impact resistance
-20.degree. C., 30 kg . cm
" "
__________________________________________________________________________
(Remarks)
(1) Test for abrasion resistance: A sample was subjected to a rotary
rubbing action of a taber abraser defined in ASTM D1175 (Tests for
abrasion of textile fabrics) in which an abrasive wheel CS #10 is used
under a load of 500 g, to measure the number of revolutions required to
give exposure of the substrate by wearing out the brilliant surface of th
metal film.
(2) Test for cold impact resistance: The sample was allowed to stand for
at least 2 hours at -20.degree. C., then quickly placed on a supporting
table of a DuPont's impact tester and subjected to a hammering action of
shaft with a semispherical tip having a radius of 1/4 inch on one end
therof which action was produced when a load of 500 g was dropped on the
other end of the shaft. Any change in appearance of the sample in this
case was observed and recorded.
(3) Warm water resistance, heat resistance and humidity and heat
resistance: After these tests, observation of appearance of the tested
sample as well as an adhesion test with a taping was made.
TABLE 5
______________________________________
Test item Result obtained
______________________________________
Front impact
55.degree. C. .circle.
ordinary temperature
.circle.
-30.degree. C. .circle.
Corner impact
55.degree. C. .circle.
ordinary temperature
.circle.
-30.degree. C. .circle.
High temperature oscilation test
.circle.
Heat cycle test .circle.
Water immersion test .circle.
Salt spray test .circle.
Accelerated weather-resistance test
.circle.
Abrasion test .circle.
______________________________________
*Circle (.circle.) means passing the test.
EXAMPLE 3
A mixture of (1) 40 parts by weight of ABS resin composed of 15% by weight
of a butadiene component and 85% by weight of an acrylonitrile-styrene
component and (2) 60 parts by weight of a thermoplastic polyurethane resin
derived from polytetramethylene adipate glycol having a molecular weight
of about 2000, tetramethylene glycol and diphenylmethane-4,4'-diisocyanate
was prepared. A modified polyurethane resin thus obtained possesses
physical characteristics shown in Table 6. Using this modified
polyurethane resin in the same manner as described in Example 1, a bumper
molding was molded and a multilayer film was heat welded onto the surface
of the bumper molding. The resultant bumper molding was then fixed to a
RIM polyurethane bumper in the same manner as described in Example 1 to
form a product. Table 7 shows a result of various tests made in the same
manner as described in Example 1 for evaluating the performance of the
product. As is evident from Table 7, this product exhibits excellent
properties useful for elastic metallized decorative moldings.
TABLE 6
______________________________________
Tensile strength (kg/cm.sup.2)
600
Fracture elongation (%) 500
100% Modulus (kg/cm.sup.2)
152
Tear strength (kg/cm.sup.2)
150
Cold embrittlement temperature (.degree.C.)
-60
JIS Hardness (A) 97
______________________________________
The testing methods for measuring the physical characteristics were
identical with those described in Example 1.
TABLE 7
______________________________________
Test item Result obtained
______________________________________
Front impact
55.degree. C. .circle.
Ordinary temperature
.circle.
-30.degree. C. .circle.
Corner impact
55.degree. C. .circle.
Ordinary temperature
.circle.
-30.degree. C. .circle.
High temperature oscilation test
.circle.
Heat cycle test .circle.
Water immersion test .circle.
Salt spray test .circle.
Accelerated weather-resistance test
.circle.
Abrasion test .circle.
______________________________________
*Circle (.circle.) means passing the test.
It is understood that the preceding representative examples may be varied
within the scope of the present specification, both as to the components
and conditions, by one skilled in the art to achieve essentially the same
results.
As many apparently widely different embodiments of the present invention
may be made without departing from the spirit and scope thereof, it is to
be understood that the present invention is not limited to the specific
embodiments thereof except as defined in the appended claims.
* * * * *
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