Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ICE MELTER AND METHOD OF MAKING S~ME
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BACKGROUND OF THE INVENTION
Field of The Invention:
This invention relates to compositions ~or
melting ice and more par-ticularly for melting ice on
drivewa~s, sidewalks, and the like.
The invention also contemplates the method of
making the composition.
Description Of T~e Prior Art:
Unre~ined rock salt has long been used to melt
ice on driveways, sidewalks and the like; however, the
wide variation in particle size makes it nearly impossible
to spread uniformly. Moreover, the impurities in the
salt leave an unsightly coating on the melted surface
which, when tracked indoors, i5 damaging to floors and
carpeting. Vegetation is also vulnerable to damage from
salt. Sodium builds up in the soil and ultimately can
result in the soil becoming completely toxic to plant growth.
Examples of patents which relate to compositions
for melting ice are U.S. Patent No. 2,626,219 which deals
with a sawdust sprayed with a salt solution; U.S. Patent
No. 3,108,075 which deals with the use of urea; U.S. Patent
No. 3,227,654 which deals with a urea alkali-metal nitrate
composition; UOS~ Patent No. 2,988,509 which deals with a
mixture of sodium chloride and calcium chloride; U.S. Patent
No. 2,980,620 which does not use any chlorides at all;
U.S. Patent No. 4,283,297 which does not use any salts;
U.S. Patent No. 2,158,854 which deals with an aluminum
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chloride, sodium chloride and potassium chloride composition;
U.S. Patent No. 3,772/202 which does not use urea;
U~S. Patent No. 4,081,256 which does not use sodium chloride;
U.S. Patent No. 4,119,556 which is a thermal energy storage
material that does not use urea; and U.S. Patent No. 4,175,613
which is an energy s-torage material which is not pertinent
at all.
None of these references shows the composition
of this invention.
SUMMARY OF THE INVENTION
The salt, i.e., sodium chloride and/or potassium
chloride, used in the composition of this invention is
completely soluble and virtually free of calcium sulfate
and other materials forming white deposits on melted
surfaces. A predetermined size range of solid materials
that are most effective in reducing hazardous conditions
has been determined for sodium chloride and/or potassium
chloride to be approximately 94~ between 1.19 - 2.36
millimeters. Since potassium chloride is included as a
substantial component, the danger of damage to vegetation
is reduced to near zero.
The hygroscopicity of sodium chloride and
potassium chloride is low; however, by coating the two
materials with an amide such as urea, the melting action
of the composition is greatly enhanced. Urea, being very
hygroscopic, goes into solution at once when exposed to
ice or snow, thus providing an aquatic solution to speed
the disolution of the sodium and potassium chloride.
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DESCRIPTION OF PREFER~D EMBODIMENT
The present invention provides an ice melting
composition designed primarily for use on driveways,
sidewalks and the like, which is in a dry,stable form
that lends itself readily to application~ The inven-tion
relates to a chemical composition including a salt such as
sodium chloride and/or potassium chloride and an amide
such as urea, which is characterized by an enhanced ice
melting capability.
From the foregoing, it can be seen that an ice
melter composition has been provided which is simple to
use and harmless to the user and wherein the composition
includes a salt, preferably a mixture of sodium and/or
potassium chloride together with an amide which is preferably
urea. The urea is coated on the sodium chloride/potassium
chloride combination from about 1% to about 4~ by weight
of the salt. The sodium chloride/potassium chloride
combination is present by weight in about three parts of
sodium chloride to one part of potassium chloride.
The peculiar combination of ingredients in the
ice melter of this invention produces a synergistic action
which causes the mixture to perform better in combination
than it would in its component parts. For example, the
application of sodium chloride or potassium chloride by
itself to an ice-coated surface will not give the same
results as will the combination of the chemicals of this
invention. In the following -table, it will be noted that
a 3:1 ratio by weight of sodium chloride to potassium
chloride produces a eutectic temperature which is lower
than that of other comblnations of sodium chloride and
potassium chloride. In particular, a 3:1 ratio of
sodium chloride to potassium chloride with 3% by weight
of the salt of urea provides a 0.5 F. freezing point
which is lower than all other combinations of sodium chlo-
ride/potassium chloride and urea.
EREEZXNG POINT ANALYSES
Wt Ratio0% Urea1% Urea 2% Urea 3% Urea 4% Urea
NaCl/KCL Freezing Points
10 1:1 7.0 F 7.5 F5.2 F 4.0 F 3.g F
2:1 2.0 F 5.5 F2.0 F 4.0 F 4.5 F
3:1 2.6 F 1.0 F1.8 F 0.5 F 3.6 F
4:1 2.5 F 3.5 F3.0 F 2.0 F 2.0 F
It will be seen from the table that 20 separate
samples were made up in the ratio as shown in the table
of results. The mixtures were all on a weight/weight
basis. A portion of each mixture was used to make a
20% solution in deionized water. Each of these was then
placed in an acetone/dry ice bath and stirred vigorously
with a Teflon coated stir bar. The temperature was
monitored with an antifreeze thermometer with a range
of 35 F. to -35 F. The freezing point temperature was
recorded just as the solution turned to slush.
The lowest freezing temperature was obtained on
the 3:1 sodium chloride/potassium chloxide solution with
3~ urea. It was recorded as 0.5 F. All other tempera-
tures ranged from 7 F. to 0.5 F.
In the method of making the ICE MELTER compo-
sition of this invention, the salt mixture is screened to
a uniform size, i.e., +8 14 Tyler mesh, and is fed into
a rotating drum mixer. The drum is approximately five feet
in diameter and six feet in length. It has a perpherial
speed of 149-154 feet per minute. A six inch dam on the
discharge end o the incllned drum mixer retains a rolling
bed of the mixed salts. A flat fan spray nozzle
(Spraying Systems H.25 W 8003 or equivalent) at pressures
between 25 and 40 PSIG is used to coat the urea solution
on the salt mixture. Water solutions of urea with varying
concentrations of from 40% to 70% by weight are used.
Urea solutions can be stabilized or unstabilized depending
on ambient conditions. The rolling action of the bed
in the mixer acts to pass each particle of salt through
the spray solution resulting in uniform coating. The
material from the mixer acts to pass each particle of salt
thxough the spray solution resulting in uniform coating.
The material from the mixer is discharged into a rotary
dryer, 5 feet in diameter and 30 feet long, for removal
of water and crystallization of the urea. The dryer is
heated with a gas burner to give the material exiting
the dryer a temperature of between 140 F - 180 F.
Product material is discharged from the dryer
into a cooler through a closed chute tha-t is also a
counterair plenum for both dryer and cooler. ~ir flow
control through the cooler is by means of adjustable valves
in the discharge plenum. Ambient air is drawn into the
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discharge end of the cooler, thereby flowing counter cur-
rent to material flow at approximately 2000 cubic feet per
minute. Continued moisture removal by surface evapora-
tion tends to control final product moisture content at
about 0.05%. Also, evaporative cooling tends to stabilize
and harden the urea coating to prevent phase changes as
environmental conditions fluctuate.
From the foregoing, it can be seen that an ice
melter composition has been provided which is simple to
use and harmless to the user and wherein the composition
includes a salt, more particularly sodium chloride and/or
potassium chloride and preferably a mixture of sodium
chloride and potassium which is coated with an amide,
more particularly urea. The method of making the lce melting
composition is also disclosed.
