Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: IMPROVED INSULATOR
BACKGROUND OF T~IE I~VENTIO~I
The present invention pertains to the field of
insulating material and relates to a generally free
flowing composition which may be either applied as a
loose fill or as a wet spray in conjunction with an
adhesive. By variance of the ratio of the respective
components, the insulation composition hereof may serve
as a minimal heat insulator, on the one hand, or in the
extreme, as a fire retardant wall.
The invention hereof has found particularly useful
application in the interior of metallic buildings.
In relatively recent years, the advent of metallic
building structures, primarily for small office buildings
and warehouses, has noticeably replaced or supplemented
conventional wooden building structures. These metallic
building structures are not readily amenable to the same
type of insulating materials and methods as has been
commonly been used heretofore with other building struc-
tures. Conventional building structures have in the pastfrequently been insulated with a variety of known insula-
tion materials, such as asbestos or glass fiber composi~
tions, such as is shown in United States Patent 3,687,850,
where there is disclosed a fiber composition structure
useful at temperatures of about 2,000F and made out of silica
and alumina fibers primarily. Fibers of this general type
have heretofore been manufactured into thermal insulation
compositions preformed into fiber glass batts or the like,
and placed in sidewall cavities and attics. The fiber
glass batts are sized to fit between upright studs in a
wall cavity or horizontal joists in an attic. While such
fiber glass batts provide good insulation properties, -that
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is an R value (in hr-ft -F/BTU) of about 11 or 12, the
installation of such fiber glass batts is not only
difficult after construction of the building is completed,
but sometimes, particularly in metal bullclings or the
li~e, is not feasible, because there may be no inter-
mediate roof on which to lay the batt. Even if there is,
it may become more desirable to simply "blow" the thermal
insulation directly on the surface of the metal building,
that is on the interior ceiling surface. This is quite
acceptable, except where the heat insulation material
contains the component of boric acid, a commonly used
compound which is particularly corrosive to metal, and
as a result, the boric acid must be neutralized or
"buffered" with a chemical agent such as borax. The addi-
tion of borax to boric acid significantly increases thecost of the insulation material and adds relatively nothing
to its principal objective, that is heat insulation. Now
that the construction of metal buildings has risen
dramatically and partially replaced conventional type
building construction, and as a result significantly
- greater amounts of blown on insulation is being used, there
is greater opportunity for economy and savings in construc-
tion if an improved thermal insulator were developed and
in which the borax component were eliminated.
The present invention is thus directed to an improved
thermal insulator in which borax and the like types of
chemical buffers and/or neutralizers is eliminated.
A principal advantage and feature of the invention thus
exists in a thermal insulator having no per se chemical
buffer or neutralizer.
A further fea-ture and advantage of the invention
exists in a thermal insulator composition providing
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improved thermal insulation as a result of the neutralizer
ingredient itself.
A further feature and advantage of the invention
residesin an improved insulator in which the buffer and/or
neutralizer is an expanded glass.
A further feature and advantage of the invention
resides in an insulating material in which the thermal
transmission properties may be varied predictably by
v'ariance of thë ratio of the constant composition com-
ponents.
Yet another feature and advantage of the in-
vention is an improved thermal insulator in which the heat
transmission characteristics may be varied by adjustment
of the ratio of the component ingredients so that heat
insulation can be minimized and so that heat insulation
can be maximized, the latter to the extent of presenting
a substantial fire wall insulator.
Yet another feature and advantage of the in-
vention resides in an insulating material which is less
expensive than materials presently used while yet improving
the overall heat insulating characteristics per unit of
thickness thereof~
In accordance with the invention, there is thus
provided a thermal insulation composition comprising:
a) cellulose,
b) boric acid in an amount sufficient for
reducing flammability of the cellulose; and
c) expanded silicate glass in an amount suffi-
cient for neutralizing the acidic character of the boric
acid, the expanded glass also serving to both lighten the
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overall weight of the thermal insulation composition and to
enhance the thermal insulation characteristics thereof.
DESCRIPTION OF THE INVENTION
The present invention involves an improved ther-
mal insulator comprising essentially three components of
ingredients, and which effective over a wide range of
temperatures. The effectiveness of the thermal insulator
hereof is related to the relative proportion of the various
ingredients thereof. The present description will explain
the manner in which the present heat insulation composition
is manufactured, and the relationship and influence of
the various components thereof on the heat insulation
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characteristics. It should he recognized that the
present insulator may be manufactured in a variety of
forms, these including, but not limited to, that which is
commonly known as loose fill, such as would be placed
between the beams on an attic floor, or between studs in
a building, and which may take the form of fabricated
batts or the like; or the invention may take the form of
a wet spray insulator intxoduced under pressure through
the nozzle on a hose in connection with an appropriate
adhesive directed into the stream of the insulator and
onto a beam or other exposed surface of the building
structure. In all instances of application, the heat
insulating characteristic of the material may be varied
so as to produce an insulator having only nominal insulat-
ing capacity, on the one hand, while, on the other, aninsulator reaching Governmental standards for a two hour
` fire wall may be produced.
The invention comprises a mechanical mixture of
cellulose or wood-like fiber, boric acid and amorphous
expanded silicate glass. These cons-tituents, each intended
to perform their respective functions, may be varied -to
accomplish a broad range of thermal insulation capabilities.
With a relatively high glass component, by weight, the com-
position is found to constitute a superior fire resistant
agent. The composition also finds use as a sound absorbing
agent.
The cellulose component of the invention may be pro-
vided in the form of wood shavings, for example, or pre-
ferably in the form of old newspapers intended to con-
stitute the bulk of the product. The newspapers or othercellulose component must be thorou~hly ground to a mush-
like consistency, which is dry in character and therefore
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not unlike the fibrous appearance of rock wool. The
processing of the cellulose to this appearance is best
accomplished in a hammermill where the cellulose is ~ed
to the mill on semi-continuous basis for production of
the processed component. The processed component of
cellulose is particularly light in weight, easily com-
pressible, but highly absorptive of sound and radiant
energ~ waves. Since the cellulose is inherently flamm-
able, a fire retardant agent is necessarily introduced
to the hammermill during processing of the cellulose.
The fire retardant agent should be dry in form, and would
preferably constitute boric acid or -the like. The boric
acid may be fed to the hammermill through an auger or other
appropria-te means. It is here discovered that the
corrosive effect of boric acid may be neutralized by
introduction of the aforementioned expanded glass.
Although the borax or the like used heretofore was effec-
tive for neu-tralizing or buffering the boric acid, i-t had
no other beneficial effect upon the insulating composition
and in fact had several adverse effects. It first pro-
duced excessive dust which was difficult to combat and
increased adversity of the working environment. Further-
more, it added weight to the insulating composition, and
this weight provided no advantage. But more so, it added
nothing to the objective of the product itself, namely
reduction of thermal transmission through the insulating
medium. Of prime importance, however, was the cost which
borax or the like added to the finished product, since the
necessary borax quantity for neutralizing the boric acid
often ran to over 20~ to 25% of the -total material weigh-t.
Thus, the cost of chemicals for the insulating composition
was a significant factor, since the cost of cellulose (paper~
constitutes a relatively low cost component in the overall
produet. In substitution of the expanded glass component
proposed herein markedly reduces the overall weight of
the insulator composition. Furthermore, as explained above,
it effectively buffers the boric acid of the composition.
A third advantage in use of the expanded glass resides in
-~ the markedly improved thermal insulation provided to the
finished produet, and there is, therefore, provided a
resultant thermal insulation which is lo~er in cost, lighter
in weight, and superior in its principal Eunetion, namely
thermal insulation.
In manufaeture praetiee, the pulverizing of the
eellulose preferably takes plaee in a first hammermill,
whereafter the eellulose of lint-like eonsistency is au-to-
lS matieally withdrawn sueh as through a eonduit, and trans-
ferred to a seeond hammermill where the boric acid is
augered into the processed eellulose during i-ts movement
within the second harnmermill. Thereafter, the eellulose
is removed from the second hammermill and drawn into an
agitating bin. Transfer may take place by the inherent
eentrifugal foree of the eellulose allowing it to be blown
into a transfer conduit containing a cyclone in operative
communication with the conduit and an accumulator bin
there beneath. The cyclone is intended to rernove the dust
and allow filtra-tion of the cellulose into the bin. There
is also disposed in communieating relation with the bin a
reservoir supply of expanded glass, which is introduced
thereto and interspersed with the cellulose-boric acid by
a plurality of appropriate agitators, whleh thoroughly mix
the glass into and through the cellulose. The finishecl
product is then in-termittently withdrawn from the agitator
bin and prepared for packaging in appropriate form and si~e.
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DESCRIPTION OF T~IE PREFERRED E~IBO~IMENT:
In a preferred embodiment of the invention wherein
the insulating material is manifest in the form of loose
fill, relatively inexpensive in cost, yet meeting the
required Government standards fo.r insulating material, the
product manifests itself as follows:
(1) paper - 70~ by weight
(2) boric acid - 10-1/2% by weight
(3) glass - 19-1/2~ by weight
In the above mixture, and generally, it is sugyested
that the boric acid constitute approximately 15% by weight
of the cellulose, which, in example (1) above, constitutes
approximately 10-1/2% by weight oE -the total. Therefore,
the remainder would exist in the form of glass, this
being 19-1/2%. In a second example, -the following mix-
ture may be proposed wherein the weight of cellulose is
significantly greater, and thus requires a larger amount
of boric acid -to impart a heat resis-tant and flame re-tar-
dant character.
Example 2
(1) paper - 80% by weight
(2) boric acid - 9.6% (15% of 80%) by weight
(3) glass - 10.4% by weight
~ere it would be found that the thermal insulation of
the composition will be somewhat less than that to be
expected from the composition of Example 1, due to the
increased overall bulk of cellulose and the reduced compon-
ent of glass. Since a decreased component of glass will
tend to increase thermal transmission, it will be recog-
nized that the insulating cha.racteristic of this Example(2) is less than that of Example 1.
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In a third example of the invention, there is set
forth a relatively expensive thermal insulator composition
due to the existence of a high component of expanded
glass and a relatively low component, by weight, of
cellulose. The thermal insulating characteristics of
this composition, however, are markedly superior to either
of the compositions set forth in Examples (1) or (2).
(1) cellulose - 30% by weight
(2) boric acid - 4.5% by weight (15~ of 30%)
(3) glass - 65.5~ by weight
In experimentation, it has been found that the boric
acid component in a range of about 10% by weight or less
of the total, is considered relatively low, and that like-
wise the weight of glass at 10% or less of the total is
likewise considered low. In such a composition, there
would, of course, be 80% by weight of cellulose. So long
as the respective components of boric acid and glass are
both at around 10% or less (either), their comparative
amount is approximately the same, and no significantly
discernible change occurs in the thermal insulation
efficiency of the product. If the two ingredients (boric
acid and glass) begin to exceed about 10% each by weight
of the total, it is found that the glass component may be
increased in relation to the desired thermal insulation
characteristic in the final product, and independently of
the boric acid component in the mixture. Thus, the follow-
ing extremely low heat transmission thermal insulator may
be prepared:
Example ~
(1) cellulose - 65% by weight
(2) boric acid - 11% (15% of 65%) by weight
(3) glass - 24% by weight
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Thus~ it will be recognized that the percentage of
boric acid shall always be based upon the amount of
cellulose in the final product, and that this shall be
and constitute approximately 15% of the cellulose, by
weight, until the amount of boric acid approximates 10%
of the total weight of the mixture. Once the boric acid
approximates 10~, more or less, of the total weight of the
mixture, it is permissible to add glass in any amount
desired and in relation to the heat insulation characteris-
tics which are sought. It readily appears, therefore, tha-t
a cellulose component in the range of 70% by weight will
produce a boric acid requirement of 10-1/2% by weight of
the total (boric acid constitu-ting 15% by weight of -the
cellulose equalling 15~ times 70% equals 10.5%). There-
fore, the balance of the composition would necessarilycomprise 19-1/2% by weight of total of glass; see Example
(1) . :
Numerous experiments have been conducted with the
subject thermal insulator to determine the efficiency
thereof. In one such experiment, a fire test was con-
ducted on five steel plates sprayed with the subject
thermal insulator. The thermal insulator was mixed with
adhesives, as is commonly done when the insulating material
is blown onto an interior ceiling or beam, the adhesive
being simultaneously blown into the stream of the insulator
so as to affix the insulating material to the wall surface.
During the course of this experimentation, both the charac-
teristics of the adhesive under elevated temperature and
the thermal insulating efficiency of the material were
observed. Only the latter is here relevant, and the
results are therefore set forth.
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The overall steel plate dimensions were 42" x ~2"
x 1/4". One side of each plate was sprayed with the subject
thermal insulation material ana was identified as:
PLATESTIIIC KNESS _( IN. ) ADHESIVE TYPE
. . _ _ _
1 1.0 A
2 1.5 A
3 1.0 B
4 1.5 B
. 5 - 1.5 C
The tests were conducted at the Smithers's Fire
Technology Laboratory located in Ravenna, Ohio. The
furnace used in this test measures 3 ft. x 3 ft. x 3 ft.
The outside construction is steel and the furnace is lined
with a ceramic refractory insulation (Kaowool-Babcock &
Wilcox Mfg.). The furnace dimensions inside the insulation
are 27 in. x 27 in. x 27 in. A single burner is centered
vertically in the wall opposite the sample. This burner
is rated for 1.5 million BTU/hour and is of the ~lat flame
or non-impinging flame design. The burner and air supply
are designed to cover a wide range of air~to-fuel ratios.
Furnace conditions are monitored by three Inconel*-sheathed
Chromel*-Alumel* thermo-couples. Two positioned 8 inches
from the face of the sample and the third positioned 12
inches away.
The exterior surface temperature of each steel
plate was monitored by six CHROMEL-ALUMEL thermocouples
positioned at separate locations. Each of the six thermo-
couples were covered with a 6 in. x 6 in. insulating pad
having essentially the same characteristics as described for
the asbestos pads in Appendix A2 of ASTM E119-76.
* Trade mark
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The thickness of the coating on each of the plates
was 1 inch. There follows a time-temperature table com-
piled during the tests aforedescribed:
TIME AVERAGE STEELAVERA&E FURNACE
(MINUTES) TEMP (F) TEMP (F)
.
THERMOCOUPLE NOS.
1 _ 6 9 10 12
0 6570 70 65 65 65 70
7070 70 65 70 70 1235
130145 120 130 145 135 1435
185190 170 185 195 185 1515
~l0 200195 200 195 205 200 1555
245325 210 220 305 250 1640
375465 305 330 455 375 1670
605745 595 565 780 595 1735
100 1000 1165 975 930 1105850 1785
AVERAGE TIME TO TEMPERATURE:
TI~ (MIN.) ~VG. STEEL TEMP. (F) THERMOCOUPLE INSTALL~TION:
. . ~
102 1000
1 1 3 6 1 ,
I 9 10 12
In another experiment, the coating thickness on the
plates was increased to 1.5 inches. The following is a
time-temperature table conducted during the ex~erimen-t
aforedescribed:
:
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TIME AVEP~GE STEEL AVERAGE FURNACE
(MIN~TES~ TE~lP. (F) TEMP. (F)
.
THE~OCOUPLE NOS.
1 3 6 910 12
5 0 70 70 85 7070 70 190
70 75 70 75~5 80 1270
120130 90 120145135 1435
165185 135 165185170 1530
185185 160 175190175 1570
1050 1~5185 165 180245195 1640
195195 180 240325235 1675
260245 200 335~40305 1700
AVERAGE TIME TO TEMPER~TURE:
_
TIr~ (MIN.) AVG S~EEL TEMP~ (F) THE~MOCOUPLE INSTALLATION:
.. .. ~
15 77 1000
1 3 6
I 9 10 12
The amorphous e~panded silicate glass referred to
herein is commonly available in the market place and is
marketed by both the Diamond Shamrock Corporation of
Cleveland, Ohio, and Insulation Distributors, Inc. of
Shreveport, Louisiana, under the trademarks "Daccotherm"
and "Fireproof" respectively. Reference to the term
"glass" herein, however, is intended to refer to any type
of expanded glass product. The ~lass hereof is gen-
erally absorbant of water and will retain 10~ to 15% by
weight in moisture, even while in the hammermill, where
elevated temperatures are produced by reason of the
rotating action of the hammers. Although boric acid
retains water, its moisture content is markedly reduced by
the elevated temperatures produced within the hammermill
and which elevated temperatures tend to hea-t the cellulose
sourrounding the boric acid ingredient. It has been found
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that the flame reduction propensity inparted to the
eellulose by the borie aeid may be enhaneed by the
introduetion of live steam to the eyclone intermediate
the firs-t and seeond hammermill operations. The intro~
duetion of sueh live steam enhanees the boric aeid fune-
tion, sinee the water has been baked out of the borie acid
by the high temperatures (150F) aehieved in the first
hammermill, and it has been baked ou-t of the glass during
the popping operation thereof.
It has been found that reduc-tion of the component of
expanded glass mueh below that (by weight) of borie acid,
may eause substantial reduction in -the P~l fae-tor of the
finished produet, and as a result, applieation of the
produet to struetural beams of metal produees exeessively
eorrosive results. It thus becomes desirable to maintain
the PH faetor in the range of 7 to 7.2 or above. If it
is desired to modify the aforedescribed eomposition to
impart any of the aforedeseribed compositions to impart
fireproof characteristies there-to, as opposed to mere
heat insulation eharacteristies, one eould do so by
signifieantly inereasing the proportion of expanded glass
while reducing the proportion of eellulose therein. In
this cireumstance, the eellulose serves primarily as a
binder for the purpose of preventing the expanded glass
eomponent from craeking under in-tense heat. Thus, once
the maximum practieal amount of glass is incorporated into
the mixture, the fire wall rating of the product is pri-
marily influenced by the thickness thereof. Standard
criterion set forth by the Consumer Products Safety
Commission for a Class I insulation calls for boric acid
content of less than 15~, and it has been found en-tirely
feasible to accomplish a Class I insulation designation
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in accordance with the invention as follows:
( 1 ) boric acid - 10%
( 2) cellulose - 75~/0
( 3) glass - 15%
(all by weight).
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