U.S. patent application number 15/810842 was filed with the patent office on 2018-03-08 for exothermic gel-forming composition.
This patent application is currently assigned to FOREVER YOUNG INTERNATIONAL, INC.. The applicant listed for this patent is FOREVER YOUNG INTERNATIONAL, INC.. Invention is credited to Daniel L. Young.
Application Number | 20180066869 15/810842 |
Document ID | / |
Family ID | 43544588 |
Filed Date | 2018-03-08 |
United States Patent
Application |
20180066869 |
Kind Code |
A1 |
Young; Daniel L. |
March 8, 2018 |
EXOTHERMIC GEL-FORMING COMPOSITION
Abstract
An expandable, exothermic gel-forming compositions that are
predominately useful in the consumer products and medical
industries. More particularly, it relates to expandable particulate
exothermic gel-forming compositions with efficient and long-lasting
heat production for heating surfaces and objects without the need
for electricity or combustible fuel.
Inventors: |
Young; Daniel L.; (Las
Vegas, NV) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FOREVER YOUNG INTERNATIONAL, INC. |
Las Vegas |
NV |
US |
|
|
Assignee: |
FOREVER YOUNG INTERNATIONAL,
INC.
Las Vegas
NV
|
Family ID: |
43544588 |
Appl. No.: |
15/810842 |
Filed: |
November 13, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13387258 |
Apr 9, 2012 |
9816727 |
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PCT/US2010/043226 |
Jul 26, 2010 |
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15810842 |
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61315807 |
Mar 19, 2010 |
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61228594 |
Jul 26, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24V 30/00 20180501 |
International
Class: |
F24J 1/00 20060101
F24J001/00 |
Claims
1. A method of forming an expandable exothermic gel, the method
consisting of: combining a first galvanic particle and a second
galvanic particle to form a galvanic alloy and blending the
galvanic alloy with a super absorbent polymer by a blending
apparatus to form a powder mixture; and adding water and an
electrolyte, separately or together in solution, to the powder
mixture thereby forming the expandable exothermic gel comprised of
the powdered mixture, the water, and the electrolyte and actuating
an exothermic reaction.
2. The method of claim 1, wherein the exothermic gel has an
absorption capacity of greater than 400 g/g of wet weight per
starting dry weight.
3. The method of claim 1, further comprising: mixing a weight ratio
of 20:1 to 5:1 galvanic alloy particles to the super absorbent
polymer.
4. A gel-forming composition, comprising: a powder mixture formed
from first and second galvanic particles that are alloyed and
blended with a super absorbent polymer; and an electrolyte;
wherein, when exposed only to water, a gel composition is formed
that produces an exothermic reaction and expands to a volume at
least two fold (volume/volume) larger than the volume of the powder
mixture and the electrolyte as the powder mixture and the
electrolyte are hydrated.
5. The composition according to claim 4, wherein the super
absorbent polymer comprises an absorption capacity of at least 200
g/g of wet weight per starting dry weight.
6. The composition according to claim 4, wherein the electrolyte
comprises potassium chloride, sodium chloride or calcium
chloride.
7. The composition according to claim 4, wherein the first and
second galvanic particles comprise magnesium and iron.
8. The composition according to claim 4, further comprising a
hinder.
9. The composition according to claim 8, wherein the binder is
selected from a group consisting of natural resins, synthetic
resins, gelatins, rubbers, poly(vinyl alcohol)s, hydroxyethyl
celluloses, cellulose acetates, cellulose acetate butylates,
poly(vinylpyrrolidone)s, casein, starch, poly(acrylic acid)s,
poly(methylmethacrylic acid)s, poly(vinyl chloride)s,
poly(methacrylic acid)s, styrene-maleic anhydride copolymers,
styrene-acrylonitrile copolymers, styrene-butadiene copolymers,
poly(vinyl acetal)s (e.g., poly(vinyl formal) and poly(vinyl
butyral)), poly(ester)s, poly(urethane)s, phenoxy resins,
poly(vinylidene chloride)s, poly(epoxide)s, poly(carbonate)s,
poly(vinyl acetate)s, poly(olefin)s, cellulose esters, and
poly(amide)s.
10. The composition according to claim 4, wherein the super
absorbent polymer is sodium polyacrylamide.
11. The composition according to claim 10, wherein the super
absorbent polymer is selected from a group consisting of a
polyacrylic acid salt-based polymer, a vinyl alcohol-acrylic acid
salt-based polymer, a PVA based polymer or an isobutylene-maleic
anhydride polymer. Other examples of SAPs include polysaccharides
such as carboxymethyl starch, carboxymethyl cellulose and
hydroxypropyl cellulose; nonionic types such as polyvinyl alcohol
and polyvinyl ethers; cationic types such as polyvinyl pyridine,
polyvinyl morpholinione, and N,N-dimethylaminoethyl or
N,N-diethylaminopropyl acrylates and methacrylates; and carboxy
groups which include hydrolyzed starch-acrylonitrile graft
copolymers, partially neutralized hydrolyzed starch-acrylonitrile
graft copolymers, hydrolyzed acrylonitrile or acrylamide copolymers
and polyacrylic acids
12. The composition according to claim 4, wherein the composition
expands to a volume at least five fold (volume/volume) larger than
the volume of the powder mixture and the electrolyte.
13. The composition according to claim 4, wherein the composition
expands to a volume at least ten fold (volume/volume) larger than
the volume of the powder mixture and the electrolyte.
14. The composition according to claim 4, wherein the composition
has an absorption capacity of greater than 400 g/g of wet weight
per starting dry weight.
15. The composition according to claim 4, wherein the composition
is housed in a bag, tea bag, or permeable sachet.
16. The composition according to claim 4, wherein the exothermic
reaction generates heat for at least an hour.
17. An exothermic composition comprising: a galvanic alloy particle
blended by a blending apparatus with a super absorbent polymer to
form a powder mixture, wherein the composition is formed by adding
an aqueous solution to the composition thereby causing the
composition to expand at least two fold (volume/volume) and produce
an exothermic reaction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is Continuation application of U.S.
Non-provisional application Ser. No. 13/387,258 which was a U.S.
national stage entry of International Application no.
PCT/US2010/043226 entitled "Expandable Exothermic Gel-Forming
Composition" and filed Jul. 26, 2010, which claims priority to U.S.
Provisional Application Ser. No. 61/228,594, filed on Jul. 26,
2009, entitled "Exothermic Gel with Long Lasting Heat Formation";
and 61/315,807, filed on Mar. 19, 2010, entitled "Expandable
Exothermic Gel-Forming Compositions." The contents of each of these
prior patent applications are incorporated into this application by
reference in their entirety as if set forth verbatim.
FIELD
[0002] This invention is in the field of expandable, exothermic
gel-forming compositions that are predominately useful in the
consumer products and medical industries. More particularly, it
relates to the use of expandable particulate exothermic gel-forming
compositions with efficient and long-lasting heat production for
heating surfaces and objects without the need for electricity or
combustible fuel.
BACKGROUND
[0003] The ability to produce heat "on the spot" without the use of
electricity or burning fuels is desirable in a variety of different
applications. In the cosmetic industry, heat is desired for the
application of various cosmetics to the skin and scalp. In the
medical profession, application of heat is important in physical
therapy, orthopedics, wound healing, arthritis treatment, etc. In
consumer products, the ability to keep food and other substances
hot, as well as to heat them initially, is desired when other means
of heating are not convenient or unavailable.
[0004] The utility of exothermic chemical reactions in such
applications has been described. For example, the military has used
a "flameless heating device" (FDE) for heating rations in the field
since at least 1973. This FDE was in the form of a "hot sheet"
consisting of a magnesium anode, a carbon electrode and an
electrolyte salt. More recently, the military developed a
dismounted ration heating device (DRHD) utilizing chemical heating
pads composed of magnesium-iron alloy particles trapped in a
semi-solid polyethylene matrix (U.S. Pat. No. 4,522,190).
[0005] Other examples of metal alloy particles to produce heat in
the cosmetic industry have been described for use in conjunction
with paper-based "fluff" as the absorptive material. However, such
systems have relatively low energy potential and thus exhibit a
short duration exothermic reaction, as well as non-uniform
heating.
[0006] Accordingly, there is a need for compositions that can be
used to generate heat in a convenient format that is uniform,
controllable and long-lasting.
SUMMARY
[0007] The following presents a simplified summary in order to
provide a basic understanding of some aspects of the claimed
subject matter. This summary is not an extensive overview, and is
not intended to identify key/critical elements or to delineate the
scope of the claimed subject matter. Its purpose is to present some
concepts in a simplified form as a prelude to the more detailed
description that is presented later.
[0008] In one embodiment, the present invention relates to an
expandable, exothermic particulate gel-forming composition
comprising galvanic alloy particles blended with a super absorbent
polymer (SAP) wherein the gel expands at least two fold (volume per
volume) and produces heat for at least one hour when exposed to an
aqueous liquid and salt.
[0009] The salt may be present in the aqueous liquid, or it may be
incorporated into the gel-forming composition, in which case it
dissolves in the aqueous liquid when it comes in contact with the
gel-forming composition, thus exposing it to the galvanic alloy
particles and the SAP.
[0010] In one embodiment the electrolyte comprises potassium
chloride, sodium chloride or calcium chloride, or mixtures
thereof.
[0011] The galvanic alloy particles may comprise magnesium and
iron.
[0012] In addition, the composition may optionally include a binder
and/or an encapsulant.
[0013] The SAP may, for example be sodium polyacrylate.
[0014] The expandable composition can expand, for example, two
fold, five fold or even ten fold, volume per volume, when contacted
with an aqueous solution such as water.
[0015] In one exemplary embodiment, the gel-forming composition has
an absorption capacity of greater than 400 grams of wet weight per
starting grams of dry weight.
[0016] The composition can be formed from galvanic alloy particles
which are in turn formed from a mixture of between 2-20% by weight
iron and 80-98% by weight magnesium. In addition, it can be formed
by mixing a weight ratio of 20:1 to 5:1 galvanic alloy particles to
super absorbent polymer.
[0017] In another embodiment, the galvanic alloy particles are
microencapsulated by a polymer, such as hydroxypropyl
methylcellulose.
[0018] The composition can also be part of a kit, along with an
aqueous activator solution. In such a kit, the electrolyte is
either contained in the exothermic particulate gel-forming
composition or the aqueous activator solution.
[0019] Other aspects of the invention are found throughout the
specification.
DETAILED DESCRIPTION
[0020] This invention is in the field of expandable, exothermic
gel-forming compositions that are predominately useful in the
consumer products and medical industries. More particularly, it
relates to the use of expandable, particulate exothermic
gel-forming compositions with long-lasting and efficient heat
production for heating surfaces and objects without the need for
electricity or combustible fuel.
[0021] The exothermic gel-forming compositions of the present
invention are generally formulated from galvanic alloy particles
mixed with super absorbent polymers. In one embodiment, the
galvanic alloy particles and/or the particulate gel-forming
compositions are further processed to include some degree of
encapsulation of components to control the exothermic reaction. The
gel-forming compositions are activated upon contact with an
activator solution, such as an aqueous electrolyte solution. The
galvanic alloy particles generally consist of two metallic agents
with different oxidation potentials, and either the gel forming
composition or the activator solution also includes at least one
electrolyte.
Galvanic Alloy Particles
[0022] The alloy particles of the present invention generally
consist of a mixture of two or more metallic agents, each with a
different oxidation potential, such that one serves as the cathode
and the other serves as the anode in an electrochemical reaction,
once the two components of the composition are brought into
electrical contact with one another via an activator solution.
[0023] Exemplary metallic agents for use in the present invention
include mixtures of copper, nickel, palladium, silver, gold,
platinum, carbon, cobalt, aluminum, lithium, iron, iron(II)oxide,
iron(III)oxide, magnesium, Mg.sub.2Ni, MgNi.sub.2, Mg.sub.2Ca,
MgCa.sub.2, MgCO.sub.3, and combinations thereof. For example,
platinum may be dispersed on carbon and this dispersion used as a
cathode material. See U.S. Pat. Nos. 3,469,085; 4,264,362;
4,487,817; and 5,506,069.
[0024] An exemplary anode material is magnesium, which reacts with
water to form magnesium hydroxide (Mg(OH).sub.2) and hydrogen gas,
and generates large amounts of heat. Other metallic agents having
high standard oxidation potentials (such as lithium) may also serve
as the anode material, but are less preferred from a cost and
safety standpoint. The cathode material will have a lower standard
oxidation potential than the anode material. The cathode is not
consumed in the electrochemical interaction, but serves as a site
for electrons given up by the corroding anode to neutralize
positively charged ions in the electrolyte. Exemplary cathode
materials include iron, copper and cobalt.
[0025] Any of the usual methods can be employed in the production
of a galvanic alloy, such as conventional dissolution or mechanical
alloying. The process of mechanical alloying involves inducing a
solid state reaction between the components of an initial powder
mixture by repeated mechanical deformations caused by
ball-powder-ball collisions using a high energy ball mill. Such
mechanical deformations may include, for example, repeated
flattening, fracturing, and welding of metal constituents i.e.,
active and passive metal particles. The resultant energy produced
from the impact of colliding steel balls with particles trapped
between them creates atomically clean particle surfaces. These
atomically clean particle surfaces allow them to cold-weld
together.
[0026] The particle sizes of the metallic components before milling
may vary from a few microns to a few hundred microns. In one
embodiment, it may be desirable to have an average particle size
less than 200 microns, such as 100-150 microns, to facilitate
efficient alloying.
[0027] Exposure to oxygen or certain other reactive compounds
produces surface layers that reduce or completely eliminate the
cold welding effect. Therefore, an inert atmosphere is usually
maintained in the mill to prevent reoxidation of the clean
surfaces, thereby avoiding the formation of oxide coatings on the
particle surfaces which reduce galvanic cell reactions. An "inert
gas" as used herein is an unreactive gas, such as nitrogen, helium,
neon, argon, krypton, xenon, radon and also includes the
nonoxidizing gas, carbon dioxide. The inert gas should be
essentially free of water (less than 10 ppm, such as less than 5 or
less than 1 ppm).
[0028] Generally, when the milling process is allowed to progress
for an extended period of time, the particle structure becomes more
refined and the cathode particles reduce in size. However, after a
certain point in the milling process, any additional milling will
result in a reduction of the corrosion rate due to the cathode
material becoming too finely dispersed throughout the anode
material. When this occurs, the ratio of cathode/anode particle
surface area available for contact with the electrolyte decreases
and hence the corrosion rate decreases. The resulting mechanically
alloyed powders from a milling process are small particles
consisting of matrices of active metal having smaller particles of
passive metals dispersed throughout. Accordingly, milling time
should be optimized for the best outcome in terms of electrical
conductivity. In one embodiment, the galvanic alloy particles
consist of magnesium and nickel, magnesium and iron, magnesium and
copper, and magnesium and cobalt (U.S. Pat. No. 4,264,362). In
magnesium-containing alloys, the magnesium is usually present in
greater abundance, such as greater than 75%, 80%, 90% or 95% by
weight.
Super Absorbent Polymer
[0029] The gel-forming compositions of the present invention
comprise a superabsorbent polymer (SAP), also referred to as "slush
powder," "water-insoluble absorbent hydro gel-forming polymer,"
"hydrogel-forming" polymer or "hydrocolloid." The use of SAPs is
important because, when combined with an aqueous solution, an
expanded gel is created. This water-based gel is able to store a
significant amount of the heat generated by the exothermic reaction
due to its high specific heat capacity. Thus, the gel stays hot for
a relatively long period of time (compared to the exothermic
reaction carried out in the absence of gel) and prolongs the
duration of time that the object being heated can be maintained at
a relatively constant elevated temperature. Additionally, the
gel-forming composition expands, thereby providing greater surface
area for heat transfer to external objects.
[0030] The term "super absorbent polymer" means that the polymer is
capable of swelling to 200 gms per gm of dry polymer when exposed
to water. Generally, SAPs are loosely cross-linked,
three-dimensional networks of flexible polymer chains that carry
dissociated, ionic functional groups. The absorption capacity of a
SAP relative to a particular material, such as water, is determined
by osmotic pressure and the polymer's affinity with that material
as well as the polymer's rubber elasticity. The difference between
the ion concentration inside a SAP and that of the surrounding
water solution determines the intensity of available osmotic
pressure. Therefore, the osmotic pressure enables a SAP to absorb a
large quantity of water. Additionally, a particular polymer's
affinity for its surrounding solution also affects the absorption
capacity of the polymer. Thus, based on a polymer's absorptive
capacity due to the surrounding osmotic pressure and the polymer's
affinity for water, a SAP can absorb large quantities of water and
other aqueous solutions without dissolving by solvation of water
molecules via hydrogen bonds, increasing the entropy of the network
to make the SAPs swell tremendously.
[0031] The factor that suppresses a SAP's absorbing power, in
contrast, is found in the elasticity of the gel resulting from its
network structure. The specific rubber elasticity of a polymer
increases with the crosslinking density of the polymer, wherein the
absorption capacity of a given SAP reaches its maximum when its
rubber elasticity attains equilibrium with its water absorbing
power.
[0032] Examples of super absorbent polymers are: a polyacrylic acid
salt-based polymer, a vinyl alcohol-acrylic acid salt-based
polymer, a PVA based polymer or an isobutylene-maleic anhydride
polymer. Other examples of SAPs include polysaccharides such as
carboxymethyl starch, carboxymethyl cellulose and hydroxypropyl
cellulose; nonionic types such as polyvinyl alcohol and polyvinyl
ethers; cationic types such as polyvinyl pyridine, polyvinyl
morpholinione, and N,N-dimethylaminoethyl or N,N-diethylaminopropyl
acrylates and methacrylates; and carboxy groups which include
hydrolyzed starch-acrylonitrile graft copolymers, partially
neutralized hydrolyzed starch-acrylonitrile graft copolymers,
hydrolyzed acrylonitrile or acrylamide copolymers and polyacrylic
acids.
[0033] Methods of making super absorbent polymers are well known
and can be easily optimized to achieve a desired swellability. For
example, SAPs can be made from the polymerization of acrylic acid
blended with sodium hydroxide in the presence of an initiator to
form a polyacrylic acid sodium salt (i.e. "sodium polyacrylate.)
Other materials also used to make SAPs are polyacrylamide
copolymer, ethylene maleic anhydride copolymer, cross-linked
carboxy-methyl-cellulose, polyvinyl alcohol copolymers and
cross-linked polyethylene oxide.
[0034] Although there are many types of SAPs commercially
available, most are lightly cross-linked copolymers of acrylate and
acrylic acid, and grafted starch-acrylic acid polymers prepared by
inverse suspension, emulsion polymerization or solution
polymerization. Inverse suspension polymerization is generally used
to prepare polyacrylamide-based SAPs and involves dispersing a
monomer solution in a non-solvent, forming fine monomer droplets to
which a stabilizer is added. Polymerization is then initiated by
radicals from thermal decomposition of an initiator..RTM.
[0035] Super absorbent polymers found to be particularly suitable
include, for example, AQUA KEEP.RTM. Super Absorbent Polymer
manufactured by Sumitomo Seika Chemical Company (Osaka, Japan). For
some embodiments, a fast-acting version of AQUA KEEP.RTM. found to
be suitable is AQUA KEEP.RTM. 10SH-P. Additional polymers can be
found commercially as CABLOC 80NS, available from Stockhausen Inc.,
Greensboro, N.C.; LIQUIBLOCK.RTM. 2G-40, available from Emerging
Technologies, Inc., Greensboro, N.C.; SANWET IM1000F, available
from Hoechst Celanese Corporation, Bridgewater, N.J.; AQUALIC CA,
available from Nippon Shokubai Co., Ltd., Osaka, Japan; and SUMIKA
GEL, available from Sumitomo Kagaku Kabushiki Kaisha, Japan.
Additional SAPs are also commercially available from a number of
manufacturers, such as Dow Chemical (Midland, Mich.) and Chemdal
(Arlington Heights, Ill.). Any of the aforementioned SAPs can be
included as a blend of two or more polymers, so long as the
majority of the polymer (more than 50% and preferably more than
70%, weight per weight) has an absorption capacity equal to or
greater than 200 gms per gram.
[0036] Absorption measurements can be conducted under several
methods, including the tea-bag method, centrifuge method and sieve
method. According to the tea-bag method, a sample is placed in a
bag measuring about 5.times.5 cm and the bag is then sealed around
its perimeter. The bag is then placed in a dish with an excess of
either water or 0.9% NaCl solution and the sample is allowed to
absorb the solution and swell freely in the bag for one hour or
until it reaches equilibrium. The bag is then removed to separate
the sample from any excess solution and weighed to calculate the
swelling capacity. The absorption capacity of the polymer sample
can then be calculated in accordance with the following
formula:
A s = m m - m b ( 1 + A b ) - m s m s ##EQU00001##
[0037] Where: A.sub.s=sample absorbency; A.sub.b=tea bag material
absorbency; m.sub.m=weight of tea bag with sample after absorption;
m.sub.b=weight of empty, dry tea bag; and m.sub.s=weight of dry
sample.
[0038] In one embodiment, the SAP (or at least a majority of the
SAP if a blend of two or more is used) has an absorption capacity
of at least 200 g/g, where 1 g of SAP is capable of absorbing up to
200 g of water.
[0039] In another embodiment, the SAP is also a "fast acting
polymer," or "FAP," which has an absorption rate of no more than 20
seconds, and more preferably no more than 10 seconds or no more
than 5 seconds. These water absorption rates in seconds are usually
included in manufacturer's specifications for the various SAPs.
Optional Binders
[0040] The gel-forming composition optionally includes at least one
binder, such as a polymer or plastic, in addition to the SAP.
Exemplary binders include natural resins, synthetic resins,
gelatins, rubbers, poly(vinyl alcohol)s, hydroxyethyl celluloses,
cellulose acetates, cellulose acetate butylates,
poly(vinylpyrrolidone)s, casein, starch, poly(acrylic acid)s,
poly(methylmethacrylic acid)s, poly(vinyl chloride)s,
poly(methacrylic acid)s, styrene-maleic anhydride copolymers,
styrene-acrylonitrile copolymers, styrene-butadiene copolymers,
poly(vinyl acetal)s (e.g., poly(vinyl formal) and poly(vinyl
butyral)), poly(ester)s, poly(urethane)s, phenoxy resins,
poly(vinylidene chloride)s, poly(epoxide)s, poly(carbonate)s,
poly(vinyl acetate)s, poly(olefin)s, cellulose esters, and
poly(amide)s. The binders may added to the gel-forming composition
as a solution or emulsion in water or an organic solvent and
blended together using known methods.
Optional Encapsulation
[0041] In order to control the exothermic reaction and extend the
time during which the exothermic gel remains at an elevated
temperature, one approach is to encapsulate the galvanic alloy
particles or the gel-forming composition to both extend its shelf
life and control the release of energy once exposed to the
activating solution.
[0042] "Encapsulation," as used herein, means that at least
portions of the galvanic alloy particles or the gel-forming
composition are substantially enclosed in a suitable encapsulation
material, such that the encapsulation material is adhered to the
surface of the particles.
[0043] "Suitable encapsulation material," or "encapsulant," as used
herein, means a material that is sufficiently robust to withstand
formulation and manufacturing conditions of the gel-forming
compositions, is compatible with the formulation and does not
adversely impact its performance, with the caveat that extending
heat production is not an adverse effect. In addition, a suitable
encapsulation material adheres to the composition. Adhesion of the
encapsulant may occur through covalent chemical bonding or through
non-covalent interactions (e.g., ionic, Van der Waals,
dipole-dipole, etc.).
[0044] "Microencapsulated," as used herein, means that the average
diameter of the encapsulated component is from about 1 .mu.m to
about 1000 .mu.m. If the encapsulated component is oblong or
asymmetrical, then the average diameter is measured across that
part of the component having the greatest length.
[0045] In one embodiment, the composition is microencapsulated, and
the encapsulated product has an average diameter from about 1 .mu.m
to about 1000 .mu.m, alternatively from about 1 .mu.m to about 120
.mu.m, alternatively from about 1 .mu.m to about 50 .mu.m, and
alternatively from about 1 .mu.m to about 25 .mu.m. In another
embodiment, the encapsulated product has an average diameter from
about 100 .mu.m to about 800 .mu.m, or from about 500 .mu.m to
about 700 .mu.m, such as 600 .mu.m
[0046] Non-limiting examples of suitable encapsulation materials
include polystyrene, methacrylates, polyamides, nylons, polyureas,
polyurethanes, gelatins, polyesters, polycarbonates, modified
polystyrenes, and ethylcellulose degradable polymer matrices. In
one embodiment, the encapsulation material is
poly(lactide-co-glycolide) (PLG), poly(glycidylmethacrylate)(PGMA),
polystyrene, or combinations thereof. In an alternative embodiment,
the encapsulant is hydroxypropyl methylcellulose. Suitable
encapsulation materials may have a molecular weight of from about 5
kDa to about to about 250 kDa, alternatively from about 200 kDa to
about 250 kDa, alternatively from about 50 kDa to about 75 kDa,
alternatively from about 10 kDa to about 50 kDa and alternatively
from about 10 kDa to about 25 kDa.
[0047] It should also be understood that it is possible to
encapsulate any or all of the alloy components (i.e., both the
cathode and anode), either the cathode and/or the anode separately,
with or without the binder. Through routine optimization using
different combinations of coatings of varying components and using
known encapsulation techniques, the ideal encapsulation format can
be determined based on the use to which the composition is being
put. For example, for a body wrap intended to achieve a therapeutic
benefit for a longer period of time, a less dissolvable coating
would be desirable to extend the time period of the heat
production. Alternatively, for the administration of a medicament,
a more dissolvable coating would be desirable to achieve a higher
temperature over a shorter time span.
[0048] The chemical properties of the above-described coatings and
their use in a variety of fields such as nanotechnology, energetic
materials and the medical field is well known and such optimization
could be easily achieved based on this vast body of knowledge.
Manufacturing Methods
[0049] The gel-forming composition can be prepared from a mixture
of SAP and galvanic alloy particles using any of a variety of
commercially available mixers and blenders, such as drum mixers,
braun mixers, ribbon blenders, blade blenders, V-shaped blenders,
batch mixers, etc. A preferred blender is one that does not
excessively shear the galvanic alloy particles or the super
absorbent polymer. Depending on the type of equipment used, the two
main components and any optional components are added to the mixing
vessel either sequentially or simultaneously and mixing is carried
out until a uniformly blended product is formed.
[0050] The particulate gel-forming composition is tested by
measuring expansion volume and rate, as well as heat production and
retention. A particulate gel-forming composition is considered
optimal if it expands (volume/volume) at least two fold, and
preferably five fold or even ten fold. It is considered to be
"efficient" if it is capable of achieving a temperature of at least
110.degree. F. and maintaining a temperature of at least
105.degree. F. for one hour.
Activating Solution
[0051] The activating solution of the present invention is
generally an aqueous solution, such as water. It is also important
to note that either the gel-forming composition or the activating
solution contains at least one electrolyte, which is needed to
initiate the exothermic reaction. As used herein, the term
"electrolyte" means a substance containing free ions that is
electrically conductive. Electrolyte solutions are usually ionic
solutions and commonly exist as solutions of acids, bases or salts.
Salts when placed in an aqueous solvent such as water dissociate
into their component elements. Examples of preferred electrolytes
include potassium chloride, sodium chloride and calcium
chloride.
Uses
[0052] The gel-forming compositions of the present invention are
useful because they form an expanding gel matrix when hydrated, and
create a balance between energy release and energy governance. This
is brought about by the almost symbiotic relationship between the
SAP and the galvanic alloy particles. The gellable particulate
absorbs the water very quickly, which limits the reaction potential
of the alloy. A controlled reaction then ensues as moisture is
transferred from the gel component to the alloy component. This
reaction liberates heat and hydrogen gas, and creates oxides of the
alloy. This heat is transferred back into the gel which stores the
heat rather than letting it escape into the air. This synergistic
heat storage and distribution system provides a beneficial effect
for commercial applications such as medical, therapeutic and beauty
treatments. Since the gel-forming particles expand as they are
hydrated, they can be incorporated into any of a number of
different apparatuses and as they swell, they expand where desired,
which can be used to create an even blanket of exothermic gel,
thereby maximizing surface area contact and eliminating areas of
non-uniform heat.
EXAMPLES
[0053] In the examples that follow, the conditions such as weight
ratios, mixing times, etc., can easily be optimized for the
particular intended use. For example, in a consumer product such as
a beverage warming cup, it would be desirable to manufacture a
composition that achieves a higher temperature than for a medical
product intended to contact the skin.
Example 1
Galvanic Alloy Particles
[0054] In one embodiment, magnesium-iron particles are prepared by
mixing together 2-20% by weight iron with 80-98% by weight
magnesium in a hermetically sealed ball mill. Air is evacuated with
an inert dry gas prior to milling. Milling continues at or near
room temperature (e.g., 15 to 50 C.) until the product is
uniform.
[0055] The galvanic alloy product is tested for its ability to
react when contacted with saline solution (e.g., 0.5 to 10% sodium
chloride) by measuring a loss in weight, primarily due to the
emission of water vapor.
Example 2
Gel-Forming Composition
[0056] The galvanic alloy particles as described above are mixed
with a super absorbent polymer in a weight ratio of 20:1 to 5:1
galvanic alloy particles to super absorbent polymer. An electrolyte
such as sodium chloride is added to the mixture at a weight
percentage of, for example, between 0.05 to 10%. Because the
electrolyte is the exothermic reaction catalyst, the higher
percentage would achieve a hotter temperature than the lower
percentage.
[0057] The mixture is placed in a suitable blending apparatus and
blended to homogeneity.
Example 3
Performance of Gel-Forming Compositions
[0058] A given weight of the particulate gel-forming composition
from Example 2 is placed in a tared beaker, and the beaker is
placed in a bath of water at a constant temperature, such as
125.degree. F. A given volume of aqueous solution (e.g., water) is
added to the beaker. The temperature of the composition in the
beaker is monitored for one hour and recorded at intervals such as
every 5 minutes.
[0059] The composition is considered acceptable if it reaches a
temperature of at least 110.degree. F. and maintains a temperature
of at least 105.degree. F. for one hour.
[0060] It will be understood that many additional changes in the
details, materials, steps and arrangement of parts, which have been
herein described and illustrated to explain the nature of the
invention, may be made by those skilled in the art within the
principle and scope of the invention as expressed in the appended
claims.
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