U.S. patent application number 10/270905 was filed with the patent office on 2003-03-20 for controlled rellease of oxygen scavengers in cooling systems.
This patent application is currently assigned to Dober Chemical Corporation. Invention is credited to Blakemore, Thomas J., Chen, Yu-Sen, Drozd, Joseph C..
Application Number | 20030053927 10/270905 |
Document ID | / |
Family ID | 46281356 |
Filed Date | 2003-03-20 |
United States Patent
Application |
20030053927 |
Kind Code |
A1 |
Drozd, Joseph C. ; et
al. |
March 20, 2003 |
Controlled Rellease of oxygen scavengers in cooling systems
Abstract
Provided are compositions and methods for releasing oxygen
scavengers into a coolant. The compositions include a controlled
release component and an oxygen scavenger component which includes
at least one oxygen scavenger. Methods and devices for releasing
oxygen scavengers into a coolant are also provided.
Inventors: |
Drozd, Joseph C.; (Park
Ridge, IL) ; Blakemore, Thomas J.; (Flossmoor,
IL) ; Chen, Yu-Sen; (Naperville, IL) |
Correspondence
Address: |
STOUT, UXA, BUYAN & MULLINS LLP
4 VENTURE, SUITE 300
IRVINE
CA
92618
US
|
Assignee: |
Dober Chemical Corporation
Midlothian
IL
|
Family ID: |
46281356 |
Appl. No.: |
10/270905 |
Filed: |
October 15, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10270905 |
Oct 15, 2002 |
|
|
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09539914 |
Mar 31, 2000 |
|
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|
Current U.S.
Class: |
422/14 ;
252/188.28; 252/387; 252/394; 252/395; 422/16 |
Current CPC
Class: |
C09K 5/10 20130101; C02F
2303/08 20130101; C02F 1/70 20130101; C23F 11/00 20130101; C02F
2103/023 20130101 |
Class at
Publication: |
422/14 ; 422/16;
252/188.28; 252/395; 252/387; 252/394 |
International
Class: |
C23F 011/14; C23F
011/16; C23F 011/18 |
Claims
What is claimed is:
1. A coolant additive composition comprising: a controlled release
component and an oxygen scavenger component wherein the controlled
release component is effective to reduce the rate of release of the
oxygen scavenger component into a coolant in a cooling system.
2. The additive composition of claim 1 wherein the oxygen scavenger
component is not effective to form a protective complex with
metal.
3. The additive composition of claim 1 wherein the rate of release
is reduced relative to an identical composition without the
controlled release component.
4. The additive composition of claim 1 wherein the oxygen scavenger
component is effective to inhibit oxidative degradation of the
coolant when the oxygen scavenger component is released into the
coolant.
5. The additive composition of claim 1 wherein the cooling system
is a circulating cooling system.
6. The additive composition of claim 5 wherein the circulating
cooling system is not completely closed.
7. The additive composition of claim 1 wherein the cooling system
cools an internal combustion engine.
8. The additive composition of claim 1 wherein the oxygen scavenger
component is selected from the group consisting of thiosulfite,
thiosulfate, mercaptopropionic acid, bisulfite, hydrosulfite,
dithionate, hyposulfite, sulfite, sulfide, stannous, hydroxylamine
and hydrazine or mixtures thereof.
9. The additive composition of claim 1 wherein the coolant is
glycol-based.
10. The additive composition of claim 1 wherein the controlled
release component is partially soluble in the coolant.
11. The additive composition of claim 1 wherein the controlled
release component includes a matrix material.
12. The additive composition of claim 1 wherein the controlled
release component includes a coating material.
13. The additive composition of claim 1 wherein the controlled
release component includes both a matrix material and a coating
material.
14. A method of producing a coolant additive composition,
comprising the step of: combining an oxygen scavenger component
with a matrix material to form a mixture wherein the matrix
material is effective to reduce a rate of release of the oxygen
scavenger component into a coolant in a cooling system.
15. The method of claim 14 wherein the rate of release of the
oxygen scavenger component into the cooling system is reduced
relative to an identical additive composition without the matrix
material.
16. The method of claim 14 wherein the oxygen scavenger component
is effective to inhibit oxidative degradation of the coolant when
the oxygen scavenger component is released into the coolant.
17. The method of claim 14 wherein the matrix material comprises a
polymeric material.
18. The method of claim 14 which further comprises providing a
coating material, the coating material being effective to reduce
the rate of release of the oxygen scavenger component into the
coolant relative to an identical oxygen scavenger component without
the provided coating material.
19. The additive composition of claim 14 wherein the oxygen
scavenger component is selected from the group consisting of
thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite,
hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous,
hydroxylamine and hydrazine or mixtures thereof.
20. The method of claim 14 wherein the cooling system cools an
internal combustion engine.
21. A method of producing an additive composition comprising the
steps of: providing a coolant additive composition which includes
an oxygen scavenger component; and providing a coating material on
the additive composition to form a coated additive composition, the
coating material being partially coolant soluble and effective,
when the coated additive composition is contacted with a coolant,
to reduce the rate of release of the additive composition into a
coolant in a cooling system.
22. The method of claim 21 wherein the rate of release of the
additive composition is reduced relative to an identical additive
composition without the coating material.
23. The method of claim 21 wherein the oxygen scavenger component
is effective to inhibit oxidative degradation of the coolant when
the oxygen scavenger component is released into the coolant.
24. The additive composition of claim 21 wherein the oxygen
scavenger component is selected from the group consisting of
thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite,
hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous,
hydroxylamine and hydrazine or mixtures thereof.
25. The additive composition of claim 21 wherein the cooling system
cools an internal combustion engine.
26. A coolant additive assembly comprising: a housing including a
coolant inlet and a coolant outlet; and an additive composition
disposed within the housing including a controlled release
component and an oxygen scavenger component wherein the controlled
release component is effective to reduce the rate of release of the
oxygen scavenger component into a coolant in a cooling system.
27. The additive assembly of claim 26 wherein the rate of release
of the oxygen scavenger component into the coolant is reduced
relative to an identical additive composition without the
controlled release component.
28. The additive assembly of claim 26 wherein the controlled
release component is partially soluble in the coolant.
29. The additive assembly of claim 26 wherein the oxygen scavenger
component is effective to inhibit oxidative degradation of the
coolant when the oxygen scavenger component is released into the
coolant.
30. The additive assembly of claim 26 wherein the controlled
release component comprises a coating on the oxygen scavenger
component.
31. The additive assembly of claim 26 wherein the controlled
release component comprises a matrix material.
32. The additive assembly of claim 31 wherein the matrix material
comprises a polymeric material and is substantially coolant
insoluble or is partially coolant soluble.
33. The additive assembly of claim 26 wherein the controlled
release component comprises a coating on the oxygen scavenger
component and a matrix material.
34. The additive composition of claim 26 wherein the oxygen
scavenger component is selected from the group consisting of
thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite,
hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous,
hydroxylamine and hydrazine or mixtures thereof.
35. The additive composition of claim 26 wherein the cooling system
cools an internal combustion engine.
36. A method for releasing an oxygen scavenger component into a
coolant comprising contacting the additive composition of claim 1
with a coolant.
37. The method of claim 36 wherein the oxygen scavenger removes
molecular oxygen from the coolant.
38. A method for releasing an oxygen scavenger component into a
coolant comprising contacting the additive composition produced by
the method of claim 14 with a coolant.
39. A method for releasing an oxygen scavenger component into a
coolant comprising contacting the additive composition produced by
the method of claim 21 with a coolant.
40. A method for releasing an oxygen scavenger component into a
coolant comprising contacting an additive composition included in
an assembly of claim 26 with a coolant.
Description
RELATED APPLICATION
[0001] This application is a continuation in part of U.S. patent
application Ser. No. 09/539,914 filed Mar. 31, 2000 the disclosure
of which is incorporated herein in its entirety by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to devices and methods for
providing a controlled release of oxygen scavengers to coolant in
cooling systems, for example, but not limited to, such systems in
internal combustion engines, for example, diesel engines, open
circulating cooling systems such as cooling towers, and the
like.
BACKGROUND OF THE INVENTION
[0003] It is well known that with extended use of a coolant the
coolant degrades resulting in a lessening of effectiveness of the
coolant which is usually a glycol based composition, for example,
propylene glycol or ethylene glycol.
[0004] The main cause of coolant degradation, particularly at high
temperatures, is oxidation of elements that comprise the coolant.
Typically, air enters a cooling system due to "breathing" caused by
the heating and cooling cycles in the cooling system which cause
the coolant to expand and contract. As the coolant cools, a vacuum
is created which draws air into the system.
[0005] Coolant degradation, for example, oxidative degradation of a
coolant can be reduced or eliminated in some cases by closing the
cooling system to an intake of air. However, this approach is not
practical in many cooling system applications.
[0006] Alternatively, oxidative degradation can be minimized or
eliminated by adding to the coolant a substance that will scavenge
(e.g. remove) oxygen that enters a cooling system. Since air may
enter a cooling system slowly and constantly over a long period of
time, it is preferable that protective amounts of oxygen scavenger
be introduced slowly into the cooling system in amounts effective
to remove or lessen the oxygen concentration.
[0007] Therefore, there is a need for compositions, methods and
devices for releasing oxygen scavengers and/or oxygen scavengers
into the coolant of a cooling system at a controlled rate in order
to prevent oxidative degradation of one or more components of a
coolant in the cooling system.
SUMMARY OF THE INVENTION
[0008] New compositions, methods and devices for providing release,
preferably controlled release, of at least one oxygen scavenger
into a coolant of a cooling system have been discovered. The
present compositions, methods and devices effectively provide for
gradual, preferably sustained, and more preferably substantially
controlled, release of a oxygen scavenger into a coolant, for
example, a liquid coolant. A liquid coolant may include an aqueous
phase. The liquid coolant may also include at least one freezing
point depressant, such as at least one glycol; a liquid coolant
which includes at least one freezing point depressant and does not
include an aqueous phase; and the like. Examples of glycols which
may serve as freezing point depressants include, without
limitation, propylene glycol and ethylene glycol.
[0009] The present invention provides for coolant additive
compositions which include a controlled release component and a
oxygen scavenger component. The present invention also provides for
methods for releasing an oxygen scavenger component into a coolant
which include the step of contacting an additive composition with a
coolant. The controlled release component is effective to reduce
the rate of release of the oxygen scavenger component into a
coolant in a cooling system. The oxygen scavenger component
includes one or more oxygen scavengers. Examples of oxygen
scavengers that may be included in the oxygen scavenger component
are thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite,
hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous,
hydroxylamine or hydrazine or mixtures thereof.
[0010] Liquid oxygen scavengers such as hydrazine may require a
special composition and/or device in order to effectively remove
oxygen from a coolant. For example, aryl amine compounds and other
compounds disclosed in U.S. Pat. No. 3,983,048 may be useful in
this regard.
[0011] Examples of hydroxylamines that are useful in accordance
with the present invention include, without limitation,
hydroxylamine hydrochloride, hydroxylammonium acid sulfate,
N,N-diethylhydroxylamine, Hydroxylamine phosphate,
N-Ethylhydroxylamine, N,N-Dimethylhydroxylamine,
O-Methylhydroxylamine, O-Hexylhydroxylamine, N-Heptylhydroxylamine,
N,N-Dipropylhydroxylamine, O-Methyl N,N-diethylhydroxylamine,
N-Octylhydroxylamine, O-Ethyl N,N-dimethylhydroxylamine,
N,N-Diethylhydroxylamine hydrochloride, N-Methyl
N-ethylhydroxylamine, O-Methylhydroxylamine phosphate,
N-Butylhydroxylamine, N-Benzylhydroxylamine
(.beta.-Benzylhydroxylamine), O-Benzylhydroxylamine
(.alpha.-Benzylhydroxylamine) and N,N-Diethylhydroxylamine
acetate
[0012] The rate of release of the oxygen scavenger component may be
reduced relative to the rate of release of an identical composition
without the controlled release component.
[0013] The controlled release component may include, for example, a
matrix material and/or a coating material. The matrix material
and/or a coating material may be effective to reduce the rate of
release of the oxygen scavenger component into the coolant relative
to an identical oxygen scavenger component without the provided
coating material. In addition, the controlled release component may
include one or more polymeric materials. Further, the controlled
release component may be partially soluble in the coolant.
[0014] The oxygen scavenger component, when released in the
coolant, is effective to provide at least one benefit to the
coolant and/or cooling system. In one embodiment, the oxygen
scavenger component is effective to inhibit degradation of the
coolant when the oxygen scavenger component is released into the
coolant in a cooling system. For example, the oxygen scavenger
component may be effective to inhibit oxidative degradation of the
coolant.
[0015] In accordance with the present invention, the coolant
additive composition may be employed in a cooling system that is a
circulating cooling system. In one embodiment, the circulating
cooling system is not completely closed.
[0016] In one embodiment, the cooling system cools an internal
combustion engine, for example, a diesel engine.
[0017] The present invention provides for methods of producing the
herein described coolant additive compositions. In one embodiment,
methods include the step of combining a oxygen scavenger component
with a matrix material to form a mixture wherein the matrix
material is effective to reduce a rate of release of the oxygen
scavenger component into a coolant in a cooling system.
[0018] In another embodiment the methods include the steps of: 1)
providing a coolant additive composition which includes a oxygen
scavenger component; and 2) providing a coating material on the
coolant additive composition to form a coated additive composition.
The coating material may be partially coolant soluble and
effective, when the coated additive composition is contacted with a
coolant, to reduce the rate of release of the coolant additive
composition into a coolant in a cooling system.
[0019] The present invention also provides for combining methods of
producing additive compositions, for example, a method which
includes the steps of: 1) combining a oxygen scavenger component
with a matrix material to form a mixture wherein the matrix
material is effective to reduce a rate of release of the oxygen
scavenger component into a coolant in a cooling system; 2)
providing a coating material on the mixture to form a coated
mixture. The matrix material and coating material being effective
to reduce the rate of release of the additive composition into a
coolant in a cooling system.
[0020] The present invention also provides for methods for
releasing a oxygen scavenger component into a coolant which include
the step of contacting an additive composition produced by a method
of the invention with a coolant.
[0021] The present invention also provides for coolant additive
assemblies. The present invention also provides for methods for
releasing a oxygen scavenger component into a coolant which include
the step of contacting an additive composition included in a
coolant additive assembly with a coolant.
[0022] The coolant additive assemblies may include a housing which
may include a coolant inlet and a coolant outlet. The housing may
include an additive composition disposed within the housing which
includes a controlled release component and a oxygen scavenger
component. The controlled release component may be effective to
reduce the rate of release of the oxygen scavenger component into a
coolant in a cooling system.
[0023] Commonly assigned U.S. patent application Ser. Nos.
09/939,527; 09/781,842; 09/939,214; 09/939,212; 09/539,914 and U.S.
Provisional Patent Application No. 60/360,482 are directed to
subject matter somewhat related to the present patent application.
The disclosure of each of these co-pending U.S. Patent Applications
and Provisional Patent Application is incorporated in its entirety
herein by reference.
[0024] In addition U.S. Pat. Nos. 6,264,833; 5,024,268; 4,782,891;
5,772,873; 5,803,024; 5,948,248; 6,290,870; 6,010,639; 3,962,109;
3,959,166; RE37,369; 5,895,778; 4,711,735; 3,728,281; 3,808,138;
3,687,610; 3,645,896; 4,079,018; 3,639,263; 3,983,048; 3,843,547;
5,366,651; 4,655,930; 4,026,664 and European Patent Application EP
1170348 are directed to subject matter somewhat related to the
present patent application. The disclosure of each of these U.S.
Patents and the European Patent Application is incorporated in its
entirety herein by reference.
[0025] Unless otherwise expressly noted to the contrary, each of
the words "include", "includes", "included" and "including," and
the phrase "for example" and abbreviation "e.g. " as used herein in
referring to one or more things or actions means that the reference
is not limited to the one or more things or actions specifically
referred to.
[0026] Each and every feature described herein, and each and every
combination of two or more of such features, is included within the
scope of the present invention provided that the features included
in such a combination are not mutually inconsistent.
[0027] Additional aspects and advantages of the present invention
are set forth in the following description and claims, particularly
when considered in conjunction with the accompanying drawings in
which like parts bear like reference numerals.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The present invention is directed to the inclusion of an
oxygen scavenger component in a coolant, for example, a coolant in
a cooling system. The cooling systems, include, but are not limited
to boilers, systems in or associated with motors, engines, such as
internal combustion engines, for example, in vehicles such as
automobiles, planes, trains, trucks and the like, in heavy
equipment, including both stationary and mobile equipment, as well
as open circulating coolant or cooling systems, such as cooling
towers and the like.
[0029] In one broad embodiment, the present invention includes an
oxygen scavenger component and a controlled release component.
[0030] The oxygen scavenger component may be any suitable
composition effective for use in a coolant in accordance with the
present invention. In one embodiment, the oxygen scavenger
component is effective to eliminate or reduce the molecular oxygen
concentration in coolants, for example, in aqueous based or glycol
based coolants. In another embodiment, the oxygen scavenger
component is effective to eliminate or reduce the concentration of
oxidative species in coolants, for example, in aqueous based or
glycol based coolants. The oxygen scavenger component may be
effective to prevent oxidative degradation of components present in
solution or in dispersion in the coolant. For example, the oxygen
scavenger components may prevent the oxidative degradation of
freezing point depressants such as glycols, glycol based freezing
point depressants and the like, other coolant additives and
mixtures thereof present in the coolant. The oxygen scavenger
component selected should be effective, as noted above, and have no
substantial or significant detrimental effect on the coolant or the
cooling system in which the coolant is used. In one embodiment, an
oxygen scavenger component for use in accordance with the present
invention is not intended, and preferably does not function, to
form a protective complex with metal to protect the metal from
degradation, for example, corrosion. Examples of oxygen scavengers
which can be included in an oxygen scavenger component include
without limitation, thiosulfite, thiosulfate, mercaptopropionic
acid, bisulfite, hydrosulfite, dithionate, hyposulfite, sulfite,
sulfide, stannous, hydroxylamine and hydrazine and the like and
mixtures thereof. In one embodiment, one or more oxygen scavengers
employed in an oxygen scavenger component is/are provided as a
salt. Examples of oxygen scavenger salts include without limitation
alkali metal (e.g., sodium or potassium), alkaline earth metal
(e.g., magnesium or calcium) ammonium and the like salts. Any and
all combinations of the embodiments disclosed in the present
invention are included within the scope of the present
invention.
[0031] Preferably, an oxygen scavenger component is released over a
prolonged period of time, for example, under sustained conditions
into a coolant, preferably a liquid coolant. The oxygen scavenger
component is effective when released into the coolant to confer or
maintain one or more benefits or beneficial properties to the
coolant and/or the cooling system in which the coolant is used, in
particular, the prevention of coolant degradation. The present
invention may also be effective to, for example, prevent corrosion
in a cooling system.
[0032] Representative coolants include, but are not limited to,
liquids, such as substantially an aqueous liquid including at least
one freezing point depressant, such as at least one glycol, for
example ethylene glycol and/or propylene glycol; substantially a
non-aqueous liquid including a freezing point depressant, such as
at least one glycol, for example ethylene glycol and/or propylene
glycol; and the like.
[0033] The coolant may include one or more of the following: (1) a
buffering component to maintain a neutral or alkaline pH, including
for example, alkali metal salts or sodium phosphates, borates and
the like, (2) a cavitation liner pitting inhibitor component,
including for example, alkali metal or sodium nitrites, molybdates
and the like, (3) a metal corrosion and hot surface corrosion
inhibitor component, including for example, alkali metal, salts of
nitrates, nitrates and silicates, carboxylic acids, phosphonic
acids, phosphonate, pyrophosphate, azoles, sulfonic acids,
mercaptobenzothiazoles, metal dithiophosphates and metal
dithiocarbonates (one particular corrosion inhibitor that has been
found to be highly satisfactory is a phenolic anti-oxidant,
4,4'-methylenebis (2,6-di-tertbutylphenol) that is commercially
available under the trademark Ethyl 702 manufactured by Ethyl
Corporation), and the like, (4) a defoaming agent component
including for example, silicone defoamers, alcohols such as
polyethoxylated glycol, polypropoxylated glycol or acetylenic
glycols and the like, (5) a hot surface deposition and scale
inhibitor component including for example, phosphate esters,
phosphino carboxylic acid, polyacrylates, styrene-maleic anhydride
copolymers, sulfonates and the like, (6) a dispersing component,
including for example, non-ionic and/or anionic surfactants such as
phosphate esters, sodium alkyl sulfonates, sodium aryl sulfonates,
sodium alkylaryl sulfonates, linear alkyl benzene sulfonates,
alkylphenols, ethoxylated alcohols, carboxylic esters and the like,
(7) an organic acid, including for example adipic acid, sebacic
acid and the like, (8) an anti-gel such as that disclosed by
Feldman et al in U.S. Pat. No. 5,094,666, the content of which is
incorporated in its entirety herein by reference (for example, such
anti-gel additive comprises copolymers of ethylene and vinyl esters
of fatty acids with molecular weight of 500-50,000; or Tallow amine
salt of phthalic anhydride, used at 0.01-0.2%; or Tallow amine salt
of dithio benzoic acid, used at 0.005-0.15%; or 4-hydroxy,
3,5-di-t-butyl dithiobenzoic acid; or ethylene-vinylacetate
copolymers) and/or microbiocides, for example, microbiocides used
in open circulating cooling water systems of cooling towers, as
disclosed by Sherbondy et al. U.S. Pat. No. 5,662,803, wherein the
disclosures of which is incorporated in its entirety herein by
reference.
[0034] In one embodiment, the controlled release component includes
a coating or coating material encapsulating an oxygen scavenger
component core which enables a reduced rate of release of the
oxygen scavenger component into coolant in a cooling system, for
example a circulating cooling system. Preferably, the rate of
release is reduced relative to that of an identical composition
without the coating material. Any type of coating conventionally
known in the art which provides controlled-release properties may
be used in the present invention.
[0035] A coated coolant additive composition may be of any size or
any shape to accommodate the circumstance of use. For example,
composition may be in the form of a single object, for example a
single, puck-shaped, or "doughnut" shaped object. In one
embodiment, the composition is present as a plurality of irregular
or regular shaped pellets or tablets. Different shapes and sizes,
and the various surface to volume ratios provided thereby, can be
selected to provide a desired oxygen scavenger component release
rate.
[0036] The coating or coating material may be soluble or partially
soluble in the coolant. The soluble portion of the coating material
may be effective, when released into the coolant, to provide a
benefit to the coolant. Such coatings are highly advantageous in
that they are effective both to reduce the rate of release of the
oxygen scavenger component into the coolant and to provide a
further benefit to the coolant when solubilized or partially
solubilized into the coolant. Alternatively, the controlled release
component, for example, a coating material may be substantially
insoluble or insoluble in a coolant.
[0037] A coating material may constitute about 1% to about 60% of
the total coolant additive composition weight. For example, the
coating may constitute about 5% to about 48% or about 8% to about
30% of the total coolant additive composition weight.
[0038] In one particularly useful embodiment, the coating is a
polymer dispersion. The polymer dispersion may have one or more the
following properties:
[0039] 1. Viscosity: The polymer dispersion may be of a low to
medium viscosity. When the viscosity is to high, it may become
impossible to pump the polymer dispersion through a coating system.
This may cause the line and spray gun to become plugged. Also, in
this case, the droplets of polymer dispersion may be too thick and
difficult to lose moisture. They may not have the desired level of
dryness before they reach the tablet surface. Therefore, the
polymer may not form a good and homogeneous coating.
[0040] It may be noted that reducing the viscosity of a polymer
dispersion through dilution with water is not always a viable
solution. Often the dilution leads to changes of physical
properties for the polymer dispersion and renders the polymer not
appropriate for coating applications.
[0041] 2. Low film forming and glass transition temperatures: Every
polymer has its own characteristic film forming temperature and
glass transition temperature, T.sub.g. To form a good coating, the
polymer may have a film forming temperature lower than the
operating temperatures inside the chamber of the drum coater in the
coating process. A high T.sub.g may lead to a brittle and fragile
film which may easily peel off. Generally, a polymer with lower
film forming temperature and T.sub.g forms better film than those
polymers with higher corresponding temperatures.
[0042] 3. Good film forming ability onto tablet surface: In the
early stage of coating process, the polymer may have good adherence
to the tablet surface, so that the coating film can gradually build
up. The polymer particles may pack well without large spaces or
holes in between. This can be examined and confirmed under a
microscope. The polymer with small particle size will result in
better packing. Preferably, the polymer possesses good elasticity;
otherwise, the coating may crack, especially upon cooling.
[0043] 4. Insolubility of the polymer in an operating aqueous
system: Typically, an operating aqueous system, has high
temperatures. For example, an operating open circulating cooling
water system may be about 70 degrees F. to about 150 degrees F.,
for example, about 80 degrees F. to about 100 degrees F., or about
90 degrees F. to about 95 degrees F. The polymer coatings may
remain insoluble and stable in these systems. If the polymer
coating dissolves, it may lose the slow release function.
[0044] 5. Stability of polymer coating in solutions of aqueous
systems under operating conditions: Many polymers degrade because
they undergo alkaline hydrolysis reaction in operating aqueous
system conditions. As degradation or dissolution occurs, the
coating is damaged. As a result, the coating forms holes and loses
the control of slow release. Subsequently, all chemical ingredients
rapidly enter the bulk cooling.
[0045] Without wishing to limit the invention to any particular
mechanism or theory of operation, it is believed that the release
of the oxygen scavenger component from a coolant additive
composition which comprises a polymer coating material into the
coolant involves three steps: (a) coolant enters the coolant
additive composition through the polymer coating; (b) chemical
ingredients of the coolant additive composition dissolve in contact
with cooling; and (c) the resulting concentrated solution diffuses
through the polymer coating back into the bulk of the coolant. The
path and size of channels, microscopically, within the polymer
coating, which are characteristics of each specific polymer and are
closely related to the physical properties of each polymer in
coolant at elevated temperatures, may control the kinetics of these
actions.
[0046] Suitable polymers useful in forming a controlled release
component, for example, a coating material include, for example,
homopolymers, copolymers and mixtures thereof, wherein the monomer
units of the polymers may be derived from ethylenically unsaturated
monomers, for example, two different such monomers.
[0047] A particularly useful ethylenically unsaturated monomer is
compound I with the formula (R.sub.1) (R.sub.2)
(R.sub.3)C--COO--(CH.dbd.CH.sub.2)- , wherein R.sub.1, R.sub.2 and
R.sub.3 are saturated alkyl chains. In one embodiment, R.sub.3 of
compound I is CH.sub.3, and R.sub.1 and R.sub.2 of compound I have
a total of about 2 to about 15 carbons; such a molecule is also
known as a vinylversatate. In a one embodiment, R.sub.3 is
CH.sub.3, and R.sub.1 and R.sub.2 have a total of about 5 to about
10 carbons. In another embodiment, R.sub.3 is CH.sub.3, and R.sub.1
and R.sub.2 have a total of 7 carbons., i.e.
R.sub.1+R.sub.2.dbd.C.sub.7H.sub- .16.
[0048] In one embodiment, each of the R.sub.1, R.sub.2, and R.sub.3
of compound I is a single chemical element. For example, the
element may be a hydrogen. Compound I having a hydrogen as the
element for R.sub.1, R.sub.2 and R.sub.3 is known as
vinylacetate.
[0049] In another embodiment, R.sub.1 of compound I may be a single
chemical element, and R.sub.2 of compound I may be a saturated
alkyl chain.
[0050] Other examples of ethylenically unsaturated monomers that
may be used in accordance with the present invention include:
monoolefinic hydrocarbons, i.e. monomers containing only carbon and
hydrogen, including such materials as ethylene, ethylcellulose,
propylene, 3-methylbutene-1, 4-methylpentene-1,
pentene-1,3,3-dimethylbutene-1, 4,4-dimethylbutene-1, octene-1,
decene-1, styrene and its nuclear, alpha-alkyl or aryl substituted
derivatives, e.g., o-, or p-methyl, ethyl, propyl or butyl styrene,
alpha-methyl, ethyl, propyl or butyl styrene; phenyl styrene, and
halogenated styrenes such as alpha-chlorostyrene; monoolefinically
unsaturated esters including vinyl esters, e.g., vinyl propionate,
vinyl butyrate, vinyl stearate, vinyl benzoate,
vinyl-p-chlorobenzoates, alkyl methacrylates, e.g., methyl, ethyl,
propyl, butyl, octyl and lauryl methacrylate; alkyl crotonates,
e.g., octyl; alkyl acrylates, e.g., methyl, ethyl, propyl, butyl,
2-ethylhexyl, stearyl, hydroxyethyl and tertiary butylamino
acrylates, isopropenyl esters, e.g., isopropenyl acetate,
isopropenyl propionate, isopropenyl butyrate and isopropenyl
isobutyrate; isopropenyl halides, e.g., isopropenyl chloride; vinyl
esters of halogenated acids, e.g., vinyl alpha-chlorocetate, vinyl
alpha-chloropropionate and vinyl alpha-bromopropionate; allyl and
methallyl compounds, e.g., allyl chloride, ally alcohol, allyl
cyanide, allyl chlorocarbonate, allyl nitrate, allyl formate and
allyl acetate and the corresponding methallyl compounds; esters of
alkenyl alcohols, e.g., beta-ethyl allyl alcohol and beta-propyl
allyl alcohol; halo-alkyl acrylates, e.g., methyl
alpha-chloroacrylate, ethyl alpha-chloroacrylate, methyl
alphabromoacrylate, ethyl alpha-bromoacrylate, methyl
alpha-fluoroacrylate, ethyl alpha-fluoroacrylate, methyl
alpha-iodoacrylate and ethyl alpha-iodoacrylate; alkyl
alpha-cyanoacrylates, e.g., methyl alpha-cyanoacrylate and ethyl
alpha-cyanoacrylate and maleates, e.g., monomethyl maleate,
monoethyl maleate, dimethyl maleate, diethyl maleate; and
fumarates, e.g., monomethyl fumarate, monoethyl fumarate, dimethyl
fumarate, diethyl fumarate; and diethyl glutaconate;
monoolefinically unsaturated organic nitriles including, for
example, fumaronitrile, acrylonitrile, methacrylonitrile,
ethacrylonitrile, 1,1-dicyanopropene-1, 3-octenonitrile,
crotononitrile and oleonitrile; monoolefinically unsaturated
carboxylic acids including, for example, acrylic acid, methacrylic
acid, crotonic acid, 3-butenoic acid, cinnamic acid, maleic,
fumaric and itaconic acids, maleic anhydride and the like. Amides
of these acids, such as acrylamide, are also useful. Vinyl alkyl
ethers and vinyl ethers, e.g., vinyl methyl ether, vinyl ethyl
ether, vinyl propyl ether, vinyl n-butyl ether, vinyl isobutyl
ether, vinyl 2-ethylhexyl ether, vinyl-2-chloroethyl ether, vinyl
propyl ether, vinyl n-butyl ether, vinyl isobutyl ether,
vinyl-2-ethylhexyl ether, vinyl 2-chloroethyl ether, vinyl cetyl
ether and the like; and vinyl sulfides, e.g., vinyl
beta-chloroethyl sulfide, vinyl beta-ethoxyethyl sulfide and the
like. Other useful ethylenically unsaturated monomers are styrene,
methyl methacrylate, and methyl acrylate.
[0051] The coating material may be a mixture of polymers selected
to achieve a desired release rate hardness and/or solubility. In
one embodiment, the polymer forming the coating is made up of a
copolymer of vinylacetate and vinylversatate. In a one embodiment,
about 45% to about 95% by weight of the units are from vinylacetate
and about 5% to about 55% by weight of the units are from
vinylversatate. In one embodiment, about 65% by weight of the units
are from vinylacetate and about 35% by weight of the units are from
vinylversatate.
[0052] The vinylversatate used may be sold under the trademark
VEOVA 10 sold by Shell Chemicals. In one embodiment, the
water-based emulsion polymer is a vinylacetate-vinylversatate
copolymer, sold under the trademark EMULTEX VV575 sold by Harlow
Chemical Co. (England). Additionally, a surfactant may also be
added to stabilize the dispersion. In one embodiment, the polymer
solid in the dispersion is about 54% to about 56% by weight of
active polymer solid.
[0053] EMULTEX VV575 is particularly advantageous because it meets
all of the six requirements for a good coating as set forth above.
That is, it (1) exhibits a viscosity low enough for coating
processing without difficulties, for example about 500 to about
1,500 mPa.s (RVT 2-20 at 23.degree. C.), (2) has a film forming
temperature of 10 degrees C. and a glass transition temperature,
T.sub.g, of 11 degrees C., low enough for forming a good coating,
(3) has a fine to medium particle size of 0.37 micron and forms an
elastic coating, (4) is insoluble in coolings at operating engine
conditions, (5) is stable in coolings at operating engine
conditions and (6) gives excellent release rates for
ingredients.
[0054] In one embodiment, a copolymer which may be used as a
coating in accordance with this invention includes
acrylate-vinylversatate. For example, NeoCAR 820 sold by Union
Carbide may be used for forming coatings.
[0055] A polymer forming a coating in accordance with this
invention may be made up of a copolymer of vinylacetate and
ethylene. In one embodiment, about 45% to about 95% by weight of
the units are from vinylacetate and about 5% to about 55% by weight
of the units are from ethylene. In another embodiment, about 60% to
about 80% by weight of the units are from vinylacetate and about
30% to about 40% by weight of the units are from ethylene. In still
another embodiment, about 90% by weight of the units are from
vinylacetate and about 10% by weight of the units are from
ethylene. A controlled release component of the present invention
may advantageously comprise about 5% to about 15% of a
vinylacetate-ethylene copolymer.
[0056] A copolymer comprising vinylacetate and ethylene may be
purchased under the trade name AirFlex 410, sold by Air Products
and Chemicals, Inc., Allen Town, Pa., U.S.A. Such copolymer may
have a viscosity of about 250 to about 900 cps.
[0057] In another embodiment, the polymer for coating is made up of
a homopolymer. The monomer unit of the homopolymer may be
ethylcellulose. Ethylcellulose may be used for forming coatings is
purchased from Dow Chemical sold under the trademark ETHOCEL S10,
S20, S45 and S100.
[0058] Specific properties of the various ETHOCEL's are determined
by the number of anhydrous units in the polymer chain (expressed by
the molecular weight or the solution viscosity), and, the degree of
ethoxyl substitution (expressed as the percent of hydroxyl group,
--OH, in cellulose substituted by ethoxyl group,
--OC.sub.2H.sub.5). ETHOCEL S45 has a solution viscosity of about
41 to about 49 cP and about 48 to about 49.9% ethoxyl content. The
viscosity is for a 5% solution in 80/20 toluene/ethanol measured at
25 degrees C. in an Ubbelohde viscometer.
[0059] Controlled release components may include a matrix material.
The matrix material may be effective to reduce a release rate of
the oxygen scavenger component from the coolant additive
composition into the coolant, for example, relative to an identical
coolant additive composition without the controlled release
component. The level of oxygen scavenger component in the
circulating coolant is thereby stabilized, maintained or
replenished.
[0060] It is to be appreciated that a matrix material may comprise
a material that is soluble or partially soluble in a liquid
coolant. For example, a coolant additive composition in accordance
with the present invention may comprise a coolant-soluble matrix
material mixed with an oxygen scavenger component, wherein the
soluble matrix material provides sustained oxygen scavenger
component release by gradually dissolving into the coolant, thereby
gradually releasing the oxygen scavenger component located in the
matrix material. Preferably, a suitable soluble matrix material
dissolves cleanly in the coolant without clogging or otherwise
degrading components of the cooling system. In one useful
embodiment, the coolant soluble matrix material, when dissolved in
the coolant also functions as an additive, that is acts to provide
at least one benefit to the coolant. Alternatively, a matrix
material may be substantially soluble or substantially
insoluble.
[0061] The matrix material may be effective to allow the coolant
additive composition to be compressed into, and maintain the shape
of, for example, a pellet or tablet. Particularly useful such
matrix materials include, without limitation, dispersants,
polyvinyl pyrrolidone, acrylates, for example, sodium acrylate and
sodium polyacrylate, carboxymethylcellulose, metal
carboxymethylcelluloses, for example, sodium
carboxymethylcellulose, hydroxypropylcellulose, metal
hydroxypropylcelluloses, for example, sodium
hydroxypropylcellulose, corn starch, microcrystalline cellulose,
propylene glycol, ethylene glycol, silicates, for example, sodium
silicate and potassium silicate, methacrylate/acrylate copolymers,
metal lignosulfonate, for example, sodium lignosulfonate and
water.
[0062] In one embodiment, the matrix material includes one or more
polymeric materials. A suitable polymeric material for use in the
compositions of the present invention may remain stable in a high
temperature cooling system. In one embodiment, the polymeric
material has a melting point in excess of the coolant operating
temperature, for example, a melting point in the range of about
50.degree. C. to about 200.degree. C., or, for example, about
120.degree. C. to about 150.degree. C. or higher. In one
embodiment, the polymeric material is insoluble or partially
soluble in the coolant at the operating temperature of the cooling
system.
[0063] The matrix material may be a viscous liquid, a gel or a
solid. The matrix material, e.g., in a molten form or a soluble
form, is combined, for example, mixed with the oxygen scavenger
component. After the mixing step, the oxygen scavenger
component/matrix mixture is formed into one or more discrete units
having irregular or regular shape and size. The polymeric material
may be at least partially soluble in the coolant and, in one very
useful embodiment, may be useful to provide a benefit to the
coolant.
[0064] A coolant additive composition comprising a matrix material
may be of any size or any shape to accommodate the circumstance of
use. For example, composition may be in the form of a single
object, for example a single, substantially spherical shaped or
puck-shaped, or "doughnut" shaped object. In one embodiment, the
composition is present as a plurality of irregular or regular
shaped pellets, tablets, etc. Different shapes and sizes and the
various surface to volume ratios provided thereby, can be selected
to provide a desired oxygen scavenger component release rate.
[0065] Without wishing to limit the invention to any mechanism or
theory of operation, it is believed that when these discrete units
of oxygen scavenger component/matrix material are placed in contact
with coolant in a cooling system, the solid polymeric material
serves as a physical barrier between the coolant and the oxygen
scavenger component to limit the rate of exposure of the oxygen
scavenger component to the coolant, and thus reduce the rate of
diffusion of the oxygen scavenger component into the coolant.
[0066] The polymeric material may include polymer repeating units
derived from an olefin component having 2 to about 12 atoms per
molecule. Such polyolefins are generally polymers of unsubstituted,
aliphatic hydrocarbon olefins of 2 to about 12 carbon atoms, and
are more particularly polymers of an unsubstituted, aliphatic
hydrocarbon olefin of 2 to about 12 carbon atoms and a substituted,
aliphatic hydrocarbon olefin of 2 to about 12 carbon atoms. In one
embodiment, the polymeric material is oxidized. In another
embodiment, the polymeric material is amidized.
[0067] The matrix material may include an aliphatic acid component,
for example, as aliphatic acid component which includes aliphatic
acid molecules having about 18 or about 28 to about 36 carbon
atoms. A particularly useful aliphatic acid component is montanic
acid, nominally C.sub.28H.sub.56O.sub.2. Suitable aliphatic acid
components, for example, montanic acids may have melting points
from about 76.degree. C. to about 87.degree. C., for example, about
76.degree. C., to about 81.degree. C. The aliphatic acid component
may have a melting point of at least about 80.degree. C. or at
least about 82.degree. C. Montanic acids with these characteristics
are known, for example, under the trade name S-Wachs.
[0068] Other polymeric materials are also capable of forming the
controlled release component comprising, for example, a matrix
material. These polymeric materials include: ethylcellulose,
cellulose, silicones, rubbers, fatty and synthetic surfactants,
thermoplastic resins, adsorbents (clays) and mixtures thereof.
[0069] Polyolefins may be prepared from unsubstituted, aliphatic
hydrocarbon monoolefins, including straight chain and branched
chain compounds such as ethylene, propylene and butene-1,
isobutene, pentene, hexene, heptene, octene, isobutene,
3-methylbutene-1, 4-methylpentene-1, 4-methylhexene-1, and
5-methylhexene-1.
[0070] The polyolefin may contain an unsubstituted, aliphatic
hydrocarbon polyene, such as diene or triene, as a monomer unit.
Such unsubstituted compounds can be straight chain, branched chain
or cyclic compounds. In certain embodiments polyenes of from about
4 to about 12 carbon atoms are employed.
[0071] Suitable comonomers for preparing the polyolefins are those
utilized to prepare homopolymers as listed above such as propene or
butene-1 with ethylene or isobutylene with isoprene and the like.
Suitable termonomers are those utilized to prepare homopolymers and
copolymers as disclosed above such as propene, ethylene and the
like containing up to 15 percent, for example, up to about 10
percent by weight of polyene, for example, a diene such as
dicyclopentadiene, 1,3-butadiene, 1,5-cyclooctadiene,
2-ethylidenenorbornene-5, 1,4 hexadiene, 1,4-heptadiene, bicyclo
(2.2.1)hepta-2,5-diene and other conjugated and especially
non-conjugated dienes with linear or cyclic chains.
[0072] Trienes such as isopropylidene cyclopentadiene and the
Diels-Alder mono- and di-adducts thereof with cyclopentadiene can
be used in place of the diene.
[0073] Unsubstituted aliphatic diolefins can also be used for
preparing useful polyolefins such as butadiene, isoprene,
octadiene, and the like. Especially useful are the various forms of
polybutadiene, such as made in emulsion, suspension or solution
processes, and random, block, and star block polymers with monomers
such as styrene.
[0074] In another embodiment, the polymeric material further
includes different polymer repeating units derived from an
ethylenically unsaturated monomer. In one embodiment, such
polymeric material is polyethylene.
[0075] In one embodiment, the polymeric material is a copolymer of
ethylene and vinyl acetate, for example, a polyethylene/vinyl
acetate copolymer sold by Dupont under its trademark ELVAX.
Polyethylene/vinyl acetate copolymer is able to withstand very high
temperatures. The polymeric material may be a copolymer of ethylene
and butylene.
[0076] In another embodiment, the polymeric material is
polypropylene, for example polypropylene wax , e.g., having a
molecular weight of about 500,000. Such polypropylene is sold under
the trademark Coathylene PY 0787F. Other ethylenically unsaturated
monomers include ethylene-propylene copolymers ranging in molecular
weight from about 200,000 to about 300,000; ethylene-ethylacrylate
polymers ranging in molecular weight from about 200,000 to about
300,000. A polyisobutylene ranging in molecular weight from
approximately about 60,000 to about 135,000 may be. Repeating units
derived from an ethylenically unsaturated monomer used to form the
polymeric material includes: monoolefinic hydrocarbons, i.e.
monomers containing only carbon and hydrogen, including such
materials as ethylene, propylene, 3-methylbutene-1,
4-methylpentene-1, pentene-1,3,3-dimethylbutene-1,
4,4-dimethylbutene-1, octene-1, decene-1, styrene and its nuclear,
alpha-alkyl or aryl substituted derivatives, e.g., o-, - or
p-methyl, ethyl, propyl or butyl styrene, alpha-methyl, ethyl,
propyl or butyl styrene; phenyl styrene, and halogenated styrenes
such as alpha-chlorostyrene; monoolefinically unsaturated esters
including vinyl esters, e.g., vinyl acetate, vinyl propionate,
vinyl butyrate, vinyl stearate, vinyl benzoate,
vinyl-p-chlorobenzoates, alkyl methacrylates, e.g., methyl, ethyl,
propyl, butyl, octyl and lauryl methacrylate; alkyl crotonates,
e.g., octyl; alkyl acrylates, e.g., methyl, ethyl, propyl, butyl,
2-ethylhexyl, stearyl, hydroxyethyl and tertiary butylamino
acrylates, isopropenyl esters, e.g., isopropenyl acetate,
isopropenyl propionate, isopropenyl butyrate and isopropenyl
isobutyrate; isopropenyl halides, e.g., isopropenyl chloride; vinyl
esters of halogenated acids, e.g., vinyl alpha-chloroacetate, vinyl
alpha-chloropropionate and vinyl alpha-bromopropionate; allyl and
methallyl compounds, e.g., allyl chloride, ally alcohol, allyl
cyanide, allyl chlorocarbonate, allyl nitrate, allyl formate and
allyl acetate and the corresponding methallyl compounds; esters of
alkenyl alcohols, e.g., beta-ethyl allyl alcohol and beta-propyl
allyl alcohol; halo-alkyl acrylates, e.g., methyl
alpha-chloroacrylate, ethyl alpha-chloroacrylate, methyl
alphabromoacrylate, ethyl alpha-bromoacrylate, methyl
alpha-fluoroacrylate, ethyl alpha-fluoroacrylate, methyl
alpha-iodoacrylate and ethyl alpha-iodoacrylate; alkyl
alpha-cyanoacrylates, e.g., methyl alpha-cyanoacrylate and ethyl
alpha-cyanoacrylate and maleates, e.g., monomethyl maleate,
monoethyl maleate, dimethyl maleate, diethyl maleate; and
fumarates, e.g., monomethyl fumarate, monoethyl fumarate, dimethyl
fumarate, diethyl fumarate; and diethyl glutaconate;
monoolefinically unsaturated organic nitriles including, for
example, fumaronitrile, acrylonitrile, methacrylonitrile,
ethacrylonitrile, 1,1-dicyanopropene-1, 3-octenonitrile,
crotononitrile and oleonitrile; monoolefinically unsaturated
carboxylic acids including, for example, acrylic acid, methacrylic
acid, crotonic acid, 3-butenoic acid, cinnamic acid, maleic,
fumaric and itaconic acids, maleic anhydride and the like. Amides
of these acids, such as acrylamide, are also useful. Vinyl alkyl
ethers and vinyl ethers, e.g., vinyl methyl ether, vinyl ethyl
ether, vinyl propyl ether, vinyl n-butyl ether, vinyl isobutyl
ether, vinyl 2-ethylhexyl ether, vinyl-2-chloroethyl ether, vinyl
propyl ether, vinyl n-butyl ether, vinyl isobutyl ether,
vinyl-2-ethylhexyl ether, vinyl 2-chloroethyl ether, vinyl cetyl
ether and the like; and vinyl sulfides, e.g., vinyl
beta-chloroethyl sulfide, vinyl beta-ethoxyethyl sulfide and the
like can also be included as can diolefinically unsaturated
hydrocarbons containing two olefinic groups in conjugated relation
and the halogen derivatives thereof, e.g., butadiene-1,3;
2-methylbutadiene-1,3, 2,3-dimethylbutadiene-1,3;
2-methylbutadiene-1,3; 2,3-dimethylbutadiene-1,3;
2-chlorobutadiene-1,3; 2,3-dichloro-butadiene-- 1,3; and
2-bromo-butadiene-1,3 and the like. Mixtures of the foregoing
compounds can also be employed. Particularly useful monomer
compositions also include styrene, methyl methacrylate, methyl
acrylate, vinyl acetate, mixtures of styrene and acrylonitrile, and
mixtures of styrene and various maleates.
[0077] In one embodiment, the matrix material may be a mixture of
polymers selected to achieve a desired release rate, hardness
and/or solubility. Such mixtures may include, for example,
polyethylene/polypropylene, and/or ethylene/butylene. The
controlled matrix material may further serve as a structural agent
to the coolant additive composition by retaining the shape of the
composition.
[0078] To form an oxygen scavenger component/matrix coolant
additive composition in accordance with the present invention, an
oxygen scavenger component may be physically mixed with the matrix
material in molten form and allowed to solidify in a mold. In
another example a solid (e.g., a powder) oxygen scavenger component
may be mixed with a solid (e.g., a powder) matrix component and the
mixture is pressed into a shape, for example a pellet.
[0079] In one embodiment, the matrix material may be a
one-component or multiple component cure. For example, a monomer
with catalyst or a two part polymer, such as an epoxy or urethane,
that is mixed with the oxygen scavenger component and will
polymerize and harden to a solid.
[0080] In one embodiment, a controlled release component, for
example a matrix material is partially soluble in the coolant. The
controlled release component may include a portion which is soluble
in the coolant and is effective when released into the coolant, for
example, when solubilized into the coolant, to provide a benefit to
the coolant. Thus, the matrix material may be effective not only to
reduce the release rate of the oxygen scavenger component into the
coolant, but in addition, can also act as an additional additive
component in that the coolant is provided with a benefit when the
soluble portion of the controlled release component is released
into the coolant.
[0081] In accordance with the present invention, the controlled
release component may be a matrix material and/or a coating
material. In one embodiment of the invention, the coolant additive
composition of the present invention includes an outer coating
material which encases the discrete units of oxygen scavenger
component/matrix material. The polymeric material or materials used
to produce the controlled release component (e.g. matrix material
and/or coating material) can be selected or chosen so that a
portion of the polymeric material or materials in the controlled
release component is soluble in the coolant. The materials included
within the controlled release component can be customized to
provide the desired degree of coolant solubility and a desirable
benefit to the coolant when the soluble portion is solubilized in
the coolant. Such partially soluble controlled release components
are included within the scope of the present invention. If the
coating material is coolant-insoluble, the coating may be
sufficiently porous, or breakable when exposed to high temperature
coolant, to allow the coolant to penetrate or break the coating and
contact the oxygen scavenger component/matrix material encased
therein.
[0082] If both a matrix material and a coating material are
present, the release rate of the oxygen scavenger component from
the coolant additive composition may be reduced relative to an
identical coolant additive composition without one of the matrix
material and the coating material.
[0083] In one embodiment, the coolant additive composition is
layered. For example, the innermost core of the coolant additive
composition may be a mixture of an oxygen scavenger component and a
first matrix material. The next layer of the coolant additive
composition may be a mixture of an oxygen scavenger component and a
matrix material different from the first. Alternatively, the next
layer may be a mixture of the oxygen scavenger component and the
matrix material of the first layer, but having a different mixture
ratio. The coolant additive composition of the present invention
may include more than one layer to achieve a varied release
pattern. In one embodiment, the coolant additive composition
comprises more than two layers. In another embodiment, the coolant
additive composition comprises more than three layers. Such layered
coolant additive composition provides for a variable release
profile, for example, a pattern of release varying between low and
high. For example, the coolant additive composition may include an
outer layer structured to provide a minimal, low level rate of
oxygen scavenger release and an inner layer structured to provide a
relatively higher rate of oxygen scavenger release.
[0084] Other arrangement schemes may serve to vary the release
pattern of the oxygen scavenger component. For example, an additive
composition of the present invention may comprise an oxygen
scavenger component which is mixed with a matrix material which is
then formed into discrete pellets, which are then mixed with
another matrix material and then formed into a unitary object sized
and shaped to be placed within a coolant line of a cooling
system.
[0085] In one embodiment, a coolant additive composition of the
present invention may further include a release enhancer component
to increase the release rate. A release enhancer component may be
selected from wicking materials, surfactants, for example,
non-ionic surfactants, e.g., polyoxyethylene-polyoxypropylene block
copolymers and the like, and mixtures thereof. Such wicking
materials may include, without limitation, cotton and polyester
fibers and mixtures thereof. The fibers provide a wicking mechanism
for exposing coolant to inner portions of the coolant additive
composition.
[0086] In one embodiment, a coolant additive composition of the
present invention may further include a reinforcement component to
reinforce the structure of the coolant additive composition, making
it less susceptible to erosion by flowing coolant. Such a component
may include, for example, fibers, for example, cotton, polyester
and/or fiberglass fibers.
[0087] Release-enhancer components and reinforcement components may
be added to the matrix material and or coating material. For
example, one or more of these components may be added to a matrix
material prior to, or during, mixing of the matrix material with
the oxygen scavenger component.
[0088] The rate of release of the oxygen scavenger component may be
adjusted by the relative percentage of matrix material to oxygen
scavenger component. For example, more matrix material content in
the coolant additive composition generally may reduce the rate of
oxygen scavenger component release. In one embodiment, the matrix
material constitutes about 1% to about 99% of the total coolant
additive composition weight. In a one embodiment, the matrix
material constitutes about 25% to about 70%. For example, the
matrix material may constitute about 50% of the total coolant
additive composition weight.
[0089] In the embodiment of the present invention in which the
composition comprises a coated oxygen scavenger component/matrix
material composition, the rate at which the oxygen scavenger
component is to be released may be adjusted by the thickness of the
coating and/or the relative percent of matrix material content to
oxygen scavenger component. For example, the coating material may
constitute about 1% to about 50% of the total coolant additive
composition weight. For example, the coating may constitute about
8% to about 25% of the total coolant additive composition weight.
In addition, the matrix material may constitute about 5% to about
90% of the total coolant additive composition weight, for example,
about 15% to about 70% of the total coolant additive composition
weight.
[0090] The coolant additive composition may include a die release
agent. Suitable die release agents include, for example, calcium
stearate, magnesium stearate, zinc stearate, stearic acid,
propylene glycol, ethylene glycol, polyethylene glycol,
polypropylene glycol, polyoxypropylene-polyoxyethylene block
copolymers, microcrystalline cellulose, kaolin, attapulgite,
magnesium carbonate, fumed silica, magnesium silicate, calcium
silicate, silicones, mono-and dicarboxylic acids and corn
starch.
[0091] The coolant additive compositions of the present invention
may be in the form of a single object, for example a single,
puck-shaped, or "doughnut" shaped object. In one embodiment, the
composition is present as a plurality of irregular or regular
shaped pellets, tablets, etc. Different shapes and sizes and the
various surface to volume ratios provided thereby, can be selected
to provide a desired oxygen scavenger component release rate.
[0092] In one embodiment, the coolant additive composition is in
the form of a cylindrical tablet. The tablet may be of any size and
any shape. For example, the tablet may be about 9 mm
length.times.about 9 mm diameter. Alternatively, the tablet may be
substantially cubical with all sides being about 9 mm. In yet
another embodiment, the coolant additive composition is a flat puck
with a central aperture. The puck may have, for example, an outside
diameter of about 8 cm, an inside diameter of about 5 cm and a
height of about 3 cm.
[0093] In one embodiment, release of an oxygen scavenger component
into a coolant in a cooling system may be achieved by use of a
container which includes a casing, for example, a coolant-insoluble
and coolant-impermeable casing, having or defining a substantially
hollow interior. The casing has at least one opening. The casing
may have any suitable shape and size, which are often chosen to be
compatible with the particular application involved. The casing,
for example, may have a generally cylindrical shape, a generally
bowl shape or any of a large number of other shapes. The casing may
have one or more curved and/or planar walls or it can have all
curved or planar walls. Further aspects of containers that may be
used in accordance with the present invention are included in U.S.
patent application Ser. No. 09/939,527 which is incorporated in its
entirety herein by reference.
[0094] The coolant additive composition provided within a container
of the invention comprises at least one oxygen scavenger effective
when released into the coolant to confer or maintain one or more
benefits or beneficial properties to the coolant and/or the cooling
system in which the coolant is used. The coolant additive
composition may be provided in the form of a liquid, gel, paste or
solid particles, for example, beads, tablets, pellets or grains,
and the like, as well as mixtures thereof, within the casing. A
coolant additive composition of the invention can advantageously
further comprise a coating material that at least partially
surrounds or encapsulates or coats the oxygen scavenger component,
as discussed elsewhere herein. Such coating material may be
provided in order to at least assist in controlling, or to control,
the release of oxygen scavenger component from the casing, as
desired. The coating material may be either coolant-soluble or
coolant insoluble. The coating on the oxygen scavenger component
may be such as to allow or permit at least some release of oxygen
scavenger component from the casing into the coolant.
[0095] The coolant additive compositions of the present invention
may be provided within a container and may include a matrix
material. The matrix material, if any, should be such as to allow
or permit release of the oxygen scavenger component from the casing
into the coolant. The matrix material advantageously is effective
to at least assist in controlling, or to control, the release of
the oxygen scavenger component into the coolant.
[0096] In one embodiment, the oxygen scavenger component is present
in the casing and no matrix material and no coating material are
employed. In another embodiment, the oxygen scavenger component is
present in the casing and both a matrix material and a coating
material are employed.
[0097] In one embodiment, a container for use in the present
invention may include a coolant-permeable element or elements such
as a polymer-containing membrane, for example, a polymer-coated
membrane, in order to achieve enhanced oxygen scavenger component
release control. The membrane may be suitably coated, impregnated
or otherwise associated, for example, by spray coating, dip coating
and the like, with a polymer material. Suitable polymer materials
include without limitation, coolant insoluble materials which have
no significant detrimental effect on the coolant being treated, on
the oxygen scavenger components in the casing or on the performance
of the present container. Examples of such coating materials
include those listed by Mitchell et al U.S. Pat. No. 6,010,639, the
disclosure of which is incorporated in its entirety herein by
reference. One useful polymer material is polyethylene vinyl
acetate copolymer. In addition, or alternatively, a retention
member(s) of the coolant-permeable element or elements can be
coated, impregnated, or otherwise associated with a material, for
example, a coolant-insoluble polymer material, such as those
disclosed in Mitchell et al U.S. Pat. No. 6,010,639, to at least
assist in controlling or to control, release of the oxygen
scavenger composition from the casing, as desired.
[0098] In a one embodiment, a coating material can also be used to
coat an aforementioned membrane of the invention. Moreover, a
preferred release rate for oxygen scavenger component through the
membrane can be provided by adjusting the coating thickness to
produce the preferred release rate. Suitable film forming polymers
may include, for example, homopolymers, copolymers, and mixtures
thereof, wherein the monomer units of the polymers may be derived
from ethylenically unsaturated monomers or cellulose
derivatives.
[0099] A coating material is applied to the membrane by any
suitable method. Certain methods include dipping, spray coating,
and drum or pan coating. In one embodiment, a coating material is
spray-coated onto the membrane in an amount ranging from about 1%
to about 95% by weight of the membrane.
[0100] The container of the present invention may be filled with an
oxygen scavenger component through the opening or openings of the
casing or otherwise.
[0101] The containers of the invention, for example, the casings of
the containers, may include one or more coolant-impermeable cap
members or coolant-impermeable plugs, which can be detachable or
removable from the casing or the remainder of the casing, for
example, to facilitate filling the interior space of the casing
with coolant additive composition.
[0102] In one embodiment of the present invention wherein the
casing is substantially cylindrical shaped and the opening or
openings are located at the end or ends of the casing, one or both
ends of the casing may include a cap member, with at least one of
the cap members being removable to allow the casing or cartridge to
be filled or refilled with coolant additive composition. Another
open end of the casing, if desired, may include a cap member that
is permanently sealed thereto, for example, during manufacture, for
example, during injection molding of the container. Whenever the
cap or plug is attached by threading or screwing it onto the
casing, screw threads can be applied to the respective pieces
during or after molding with suitable dies or within the mold. The
cap member can alternatively be applied to the casing by a press
fit. In this case, suitable tolerances to make a snap fit between
the casing and the end piece can be provided, for example, to the
plastic injection molds used to make the respective pieces. The end
piece can also be formed integrally with the casing, e.g., during
injection molding.
[0103] The cap or end piece used to close at least one end of the
casing containing the oxygen scavenger component typically is
provided with at least one opening to permit release of oxygen
scavenger component therethrough, and to provide fluid
communication between the coolant located exterior to the container
and the coolant additive composition disposed within the casing
interior. Whenever an end piece is formed integrally with the
casing, the opening can be provided therein during or after
formation of the casing, for example, by injection molding.
[0104] It will be appreciated by those of skill in the art that
release of an oxygen scavenger component into a cooling system
utilizing a container of the present invention is provided, and the
release rate may be substantially controlled by several factors.
The following factors, as well as others, may also have an effect
on the performance and effectiveness of the containers of the
present invention. For example, where a membrane is used, a desired
oxygen scavenger component release rate may be obtained by
appropriate selection of: the number and type of membrane layers;
membrane thickness; membrane composition; surface area of the
membrane; membrane pore size, if any; the presence, type and
amount, if any, of polymer associated with, e.g., coated, on a
support member or membrane and/or retention member; and the
presence, type and amount, if any, of the matrix material in and/or
coating on the oxygen scavenger component, if any. The rate of
release may also be influenced by the number and size of openings
in the casing, the type and form of oxygen scavenger in the coolant
additive composition, solubility of the oxygen scavenger, coolant
temperature, and velocity of coolant through the coolant line,
viscosity of oxygen scavenger component and/or coolant additive
composition, surface tension and membrane wetting ability of the
oxygen scavenger, operating temperature and the like factors.
[0105] Contemplated within the invention is a method for releasing
an oxygen scavenger component at a controlled rate into a liquid
coolant. The method comprises placing a coolant in contact with a
coolant additive composition. In one embodiment, a coolant contacts
a coolant additive composition which is contained in a container or
cartridge as described herein. The container or cartridge
configuration described herein preferably permits a release,
preferably a controlled release, of oxygen scavenger component from
the casing interior into the coolant. It is contemplated that, in
some configurations, coolant is permitted to flow around and
encircle the casing containing the oxygen scavenger component.
However, even in these configurations, release of oxygen scavenger
component is preferably sustained and/or controlled, for example,
by passive diffusion, rather than by forced flow of coolant through
the casing.
[0106] A oxygen scavenger component for use in a container or
cartridge of the invention may be provided as a liquid, gel, paste
or as particles, for example, beads, tablets, pellets, grains,
coated versions of these, and the like, as well as mixtures
thereof. The particles have a physical size large enough to prevent
passage through the coolant-permeable components of the invention
as described elsewhere herein.
[0107] A solid coolant additive composition of the present
invention may be shaped and sized in a manner that facilitates its
handling, and conveniently is molded in the form of a pellet or
tablet having a spherical or irregular shape. It may be large
enough to avoid passing through porous components, if any, used to
retain the oxygen scavenger component composition in the casing of
the container.
[0108] Such tablets or pellets can break apart upon exposure to
coolant, however, in certain embodiments, the fragmented particles
are retained by a porous component, with dissolution occurring
inside the vessel.
[0109] In one embodiment, a concentrated solution of oxygen
scavenger is formed within the container, which is permitted to
pass, e.g., diffuse through a membrane as desired for combining
with the coolant. The rate of diffusion is controlled by parameters
including flow rate and temperature of the coolant, pore size,
orifice diameter, the presence or absence of a coating material on
the porous membrane, the presence or absence of a membrane, the
inclusion of a plug between the membrane and oxygen scavenger
material to further restrict release, oxygen scavenger component
solubility and the presence or absence of a coating material and/or
matrix material, and the like. Each dimension of length, width and
thickness of the particle may be in the range from about {fraction
(1/32)} inch to about 3 inch. Suitable binders may be used, as
known in the art, and include water-soluble acrylates, cellulosics,
polyglycols, and silicates. The coolant additive composition may
include one or more additional materials used, for example, to
strengthen, stabilize and/or otherwise enhance the composition.
[0110] A device of the present invention can be placed in a coolant
filter, either upstream or downstream of the filter medium, or it
can be provided in a substantially fixed position in a coolant
line, either upstream or downstream of a coolant filter.
[0111] The invention will now be described with reference to
certain examples. These examples are non-limiting and serve only to
illustrate certain aspects of the present invention.
EXAMPLES
Example 1
Oxygen Scavenger Added to a Commercial Coolant at Specified
Intervals
[0112] A commercial coolant based on propylene glycol was placed in
a sealed, stainless steel vessel and stirred and heated to simulate
operation of an internal combustion engine. Periodically the vessel
and coolant were cooled and air was bubbled through the vessel to
introduce oxygen in the coolant. Coolant samples were removed
periodically and analyzed for test parameters indicative of coolant
degradation (pH, reserve alkalinity, glycol oxidation products and
corrosion inhibitors). In this first experiment, the values for
these parameters at the end of the test were similar to those of
coolant used in a diesel engine for 200,000 to 300,000 miles. The
coolant was no longer considered suitable for use.
[0113] In a second experiment, the same type of coolant was
subjected to these same conditions except that the vessel was kept
sealed and no air was allowed to enter the system. In this case,
coolant degradation was not detectable.
[0114] In a third experiment, the same type of coolant was again
subjected to the same conditions as described for the first
experiment except that sodium sulfite, an oxygen scavenger, was
added to the coolant at specified intervals. Coolant samples were
removed periodically and analyzed for test parameters indicative of
coolant degradation. The values for these parameters at the end of
the test showed much less degradation of the coolant than in the
first experiment. These results demonstrate that use of an oxygen
scavenger in an engine coolant has the beneficial effect of
decreasing the degradation of the coolant.
Example 2
Forming a Coolant Additive Composition/Matrix Material
Composition
[0115] One or more oxygen scavenger additive(s) in solid form, for
example, powder or granules, or in liquid form are mixed with a
matrix material comprising molten polyethylene wax. The materials
are mixed only long enough to distribute the oxygen scavenger
additive(s) somewhat uniformly throughout the molten wax. The
pellets or granules are not dissolved into the molten wax, but
retain substantially their original pellet or granular form. While
in the molten state, the oxygen scavenger additive/polyethylene wax
mixture is then deposited into a mold to form a flat puck-shaped
form, the puck-shaped form having a central hole an outside
diameter of 8 cm, an inside diameter of 5 cm and a height of 3 cm.
The mixture is allowed to solidify while in the mold and then the
solid puck-shaped composition is removed from the mold.
Alternately, the molten oxygen scavenger additive/polyethylene wax
mixture is cooled to form small pellets, which can be considered
pastilles.
Example 3
Forming a Coated Coolant Additive Composition
[0116] A mixture of sodium sulfite and carboxymethyl cellulose is
compressed into pellets of about {fraction (1/32)} inch to about
{fraction (1/16)} inch in diameter. The pellets are placed onto a
rotating pan inside a drum coater chamber. While the pan is
rotated, a dispersion of commercially available ethylene/vinyl
acetate copolymer is pumped and sprayed through a nozzle onto the
surfaces of the forms. The spray rate is maintained at about 15
grams of dispersion per minute. The spray pattern is controlled to
give a good mist of copolymer droplets.
[0117] At the same time, through a very slightly reduced pressure,
a stream of warm air of about 40.degree. C. is passed through the
chamber to remove the water vapor from the polymer mist (or small
droplets), before and after they reach the composition
surfaces.
[0118] With time, the copolymer gradually forms a layer of coating
on each of the forms. After all copolymer dispersion is sprayed to
reach the desired thickness of coating, the resulting coated forms
are allowed to stay on the rotating pan for a few more minutes,
then are decanted from the pan into a container for storage.
[0119] Alternately, the solid which includes an oxygen scavenger
additive is coated with the copolymer in a spray drum coater.
Example 4
Forming a Coolant Additive Composition/Matrix Material
Composition
[0120] The puck-shaped oxygen scavenger additive/matrix material
composition of Example 2 is coated with a coating material by
placing a plurality of such puck-shaped forms onto a rotating pan
inside a drum coater chamber. While the pan is rotated, a
dispersion of commercially available ethylene/vinyl acetate
copolymer is pumped and sprayed through a nozzle onto the surfaces
of the forms. The spray rate is maintained at about 15 grams of
dispersion per minute. The spray pattern is controlled to give a
good mist of copolymer droplets.
[0121] At the same time, through a very slightly reduced pressure,
a stream of warm air of about 40.degree. C. is passed through the
chamber to remove the water vapor from the polymer mist (or small
droplets), before and after they reach the composition
surfaces.
[0122] With time, the copolymer gradually forms a layer of coating
on each of the forms. After all copolymer dispersion is sprayed to
reach the desired thickness of coating, the resulting coated forms
are allowed to stay on the rotating pan for a few more minutes,
then are decanted from the pan into a container for storage.
[0123] Alternately, the pastilles noted in Example 1 are coated
with the copolymer in a spray drum coater.
Example 5
Method of Using a Coolant Additive Composition/Matrix Material
Composition
[0124] Several oxygen scavenger additive/matrix material
composition puck-shaped forms of Example 2 are placed into a
coolant filter canister assembly during manufacture of the
canister. In use, the coolant filter canister is placed in fluid
communication with a circulating aqueous-based coolant system in a
vehicle spark-ignited engine. Once connection has been made and
fluid communication is established between the cooling system and
the canister, the coolant is circulated when the engine is running,
allowing the aqueous-based coolant to contact the oxygen scavenger
additive/matrix material composition forms disposed in the
canister. Upon contact with the forms, the high temperature coolant
will diffuse into and out of the polymer matrix material
sufficiently to release the oxygen scavenger additive into the
coolant. The released oxygen scavenger additive dissolves in the
circulating coolant. The gradual release of oxygen scavenger
additive, for example, at a substantially uniform rate, continues
during each circulation of coolant through the filter canister
until, eventually, all oxygen scavenger additive is depleted from
the polymer matrix material. In this example, the canister includes
filtering media for filtering coolant exiting the canister and
preventing larger particulate oxygen scavenger additive from
entering the coolant system. The spent matrix material form is
removed from the circulating system by simply removing and properly
disposing the filter canister and thereafter replacing the canister
with another new filter canister containing oxygen scavenger
additive/matrix material composition forms produced in accordance
with the present invention.
Example 6
Method of Using a Coated Oxygen Scavenger Containing Coolant
Additive Composition
[0125] Coated additive composition produced according to the method
of example 2 is packed into a reservoir or housing connected, e.g.,
along and in the fluid communication with an engine cooling system
line. An aqueous coolant is pumped through the cooling system line
and through the packed reservoir. Upon contact with the high
temperature coolant, the coating of the composition in the
reservoir begins to soften and break, allowing the coolant to
contact the oxygen scavenger additive encased therein. The oxygen
scavenger additive is released into the coolant providing benefits
thereto.
[0126] As an alternative to the coated additive composition
disclosed above, the ethylene/vinyl acetate copolymer coating is
replaced with a partially soluble coating material. Upon contact
with the high temperature coolant, the coating of the cylindrical
forms in the reservoir partially dissolves, releasing a portion of
the coating into the coolant to provide at least one benefit to the
coolant. In addition, the coolant is able to penetrate the
partially solubilized coating to contact the coolant additive
encased therein.
Example 7
Method of Using a Coated Oxygen Scavenger Containing Coolant
Additive Composition/Matrix Material Composition
[0127] Coated oxygen scavenger additive/matrix material composition
produced according to the method of example 3 is packed into a
reservoir or housing connected, e.g., along and in the fluid
communication with an engine cooling system line. An aqueous
coolant is pumped through the cooling system line and through the
packed reservoir. Upon contact with the high temperature coolant,
the coating of the composition in the reservoir begins to soften
and break, allowing the coolant to contact the oxygen scavenger
additive/matrix material encased therein. The oxygen scavenger
additive in the matrix material is released into the coolant
providing benefits thereto.
[0128] As an alternative to the coated additive/matrix material
composition disclosed above, the ethylene/vinyl acetate copolymer
coating is replaced with a partially soluble coating material. Upon
contact with the high temperature coolant, the coating of the
cylindrical forms in the reservoir partially dissolves, releasing a
portion of the coating into the coolant to provide at least one
benefit to the coolant. In addition, the coolant is able to
penetrate the partially solubilized coating to contact the oxygen
scavenger component/matrix material encased therein. The oxygen
scavenger additive in the matrix material is released into the
coolant, providing benefits thereto.
[0129] While the present invention has been described with respect
of various specific examples and embodiments, it is to be
understood that the invention is not limited thereto and that it
can be variously practiced within the scope of the following
claims.
* * * * *