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Description  |
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FIELD OF INVENTION
This invention relates to cleaning formulations and method of handling
cloths soaked therewith. More particularly, it relates to a formulation or
solvent that can be employed to effect good cleaning and alleviate current
problems; for example, a solvent blend that can be employed to remove
soils from a surface when applied to a cloth and a method of handling the
solvent-laden cloths that alleviates problems experienced heretofore.
BACKGROUND OF THE INVENTION
The prior art is replete with a wide variety of different types of
formulations and allusion to the problems created with their use. For
example, the nearest approach of which we are aware involves wiping the
surface to be cleaned with a cloth on which a solvent; such as methyl
ethyl ketone; or a solvent blend, or formulation, such as methyl ethyl
ketone, aromatic naptha, isopropyl alcohol, and ethyl acetate has been
applied. Other solvent blends that include chlorofluorocarbons and
trichloroethane are also used. The wipe cloths are then open to the
atmosphere or are transferred to a metal can for temporary storage. The
cloths then go through several stages of transfer and storage until they
are eventually laundered, buried as a solid waste or incinerated.
Alternatively, the wiping operation is performed or the cloths stored in an
enclosed area equipped with forced ventilation and a carbon absorption
system. The solvent vapors from the surfaces being cleaned and from the
used wipe cloths are carried into the filtration media where they are
partially absorbed. Periodically the solvents are stripped from the carbon
and are incinerated.
Several disadvantages are inherent in these prior art type systems and
deleterious effects result therefrom. Using the first approach, the
solvents evaporate rapidly from the work piece during the wiping operation
and further evaporation takes place from the solvent-laden wipe cloths
during storage and transfer prior to their final disposal. The emissions
from certain solvents eventually reach the atmosphere where they react
with other air emissions in the presence of sunlight to form ozone and/or
create smog.
Alternatively, certain other solvent emissions will reach the stratosphere
where they deplete the protective ozone layer, causing extensive damage to
animal and plant life on earth. These solvents are primarily
chlorofluorocarbons and trichloroethane. There are federal, state and
local regulations that restrict volatile emissions from cleaning
operations and violations can lead to severe penalties including fines,
incarceration of managing personnel, and shut down of the offending
facility.
Many of these solvents have been banned by federal statute. The federal
statute entitled "Clean Air Act" was passed by Congress in 1990 and signed
into law. This law curtails the use of such common solvent cleaners as
chloroform, dichloromethane, methyl ethyl ketone, methyl isobutyl ketone,
toluene, trichloroethylene, trichloroethane and xylenes. A formulation
which contains none of these curtailed ingredients but which are efficient
cleaners and have low flammability, low toxicity and slow evaporation
rates should have wide acceptance in many industries.
The carbon absorption system for collection and disposal of wipe solvents
has other disadvantages. It is expensive to install and to operate and has
limited collection efficiency and capacity. Moreover, such a system is not
feasible in large facilities where cleaning operations are required in
widely scattered locations, but requires rather closely located areas and
a central facility.
This invention overcomes these disadvantages and deleterious effects.
Specifically, it is desirable that a cleaning formulation have the
following features:
1. The formulation should achieve superior cleaning with a considerable
reduction of volatile emissions to the atmosphere.
2. The formulation should have excellent cleaning efficiency for a wide
variety of soils.
3. The cleaning formulation should have a low evaporation rate, low
toxicity, and be nonflammable; for example, as demonstrated by having a
flash point of 100 degrees Fahrenheit or higher when measured by the
closed cup method.
In addition, the method of disposing of cloths soaked in the formulation
should be adequate to keep the emissions to the atmosphere low.
SUMMARY OF THE INVENTION
The invention should provide at least one of the features described
hereinbefore as desirable and not heretofore provided by the prior art.
Specifically, it is an object of this invention to provide substantially
all of the advantages described hereinbefore as desirable and not
heretofore provided by the prior art.
These and other objects will become apparent from the descriptive matter
hereinafter, particularly when taken in conjunction with the appended
drawings.
In accordance with this invention there is provided a cleaning formulation
that can be applied to a cloth and employed to wipe a variety of soils
from a surface on which other operations are to be performed.
In accordance with one embodiment of this invention, such a cleaning
formulation is shown by a combination of a major and effective amount; for
example, 98-75 percent by volume of a first ingredient comprising
propylene glycol methyl ether acetate; and a minor and effective amount;
for example, 2 to 25 percent by volume of a second ingredient consisting
essentially of methyl isoamyl ketone.
An alternative second ingredient is 2 to 20 percent by volume of normal
butyl acetate.
In accordance with another embodiment of this invention, there is provided
a composition that has a less irritating odor than that of the
compositions described hereinbefore. This composition comprise up to 50%
propylene glycol methyl ether acetate, from 15 to 65% propylene glycol
methyl ether, up to 35% isoparaffins and up to 35% normal butyl acetate.
In accordance with another embodiment of this invention there is provided a
method of disposing of cloths onto which the formulation has been applied
which comprises the steps of:
1. applying the solvent into the cloth and wiping the surface;
2. placing the solvent-laden cloth in a bag designed and constructed of
materials to prevent permeation of solvent liquid or vapors through the
walls of the bag;
3. closing the bag opening, such as tying off the opening with wire or
string or sealing closed the opening to prevent loss of solvent liquid or
vapors;
4. storing the vapor-proof bag and solvent laden cloth in an enclosed
collection can;
5. storing in covered bins in a lined transfer bag the vapor-proof bags and
solvent-laden cloths that have been dumped thereinto;
6. compacting the sealed bags containing the solvent-laden cloths into
steel or fibre drums; and
7. disposing of the compacted sealed bags and contents.
As an example, the respective bags may be combustible and the entire bags
and solvent-laden cloths burned in an incinerator to produce harmless
gaseous emissions.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, FIG. 1 represents a prior art collection system.
FIG. 2 represents a proposed collection system.
FIG. 2a shows respective steps in the proposed collection system in
somewhat greater detail.
FIG. 2b shows further details of the disposal of the solvent-laden rags.
DESCRIPTION OF PREFERRED EMBODIMENTS
It should be borne in mind that this invention may be useful in multiple
areas. The specific instance in which it has been employed most zealously
has been in the attempts to upgrade the wiping of surfaces for elimination
of various "soils" to form light-weight but strong components for making
aircraft parts or the like. Accordingly, it is in this environment that
this invention will be described most closely hereinafter.
In this invention, the chemicals are listed in the Condensed Chemical
Dictionary, 11th Ed., Van Nostrand Reinhold, New York, 1987. No statement
was found therein of the chemicals of this invention being used as
cleaning chemicals.
An important consideration in selecting the components in the blend was the
volatility, or evaporation rate. If the volatility was too low, the
cleaner would not dry off the surface being cleaned. On the other hand, if
the volatility was too high, an excessive amount evaporated to the
atmosphere, creating atmospheric contamination. The ideal evaporation rate
was found to be between 30 and 100 percent of the evaporation rate of
n-butyl acetate which is used as a reference to define evaporation rates
of liquids.
A typical example of a major ingredient is propylene glycol methyl ether
acetate, having a structural formula I, C.sub.6 H.sub.12 O.sub.3, as
follows:
##STR1##
It is projected that other glycol ethers or glycol ether acetates can be
used instead of propylene glycol methyl ether acetate, but such
modification would alter the evaporation rate and other critical
properties.
In this invention, a propylene glycol methyl ether acetate should have a
flash point no lower than 116 degrees Fahrenheit if it is desired that the
material be nonflammable, or have a flash point above 100 degrees
Fahrenheit as measured by the closed cup method. Similarly, the propylene
glycol methyl ether should have a flash point no lower than 89 degrees
Fahrenheit if compositions of this invention are to be nonflammable, or
have a flash point above 100 degrees Fahrenheit as measured by the closed
cup method. If the lower flash points can be tolerated, even greater
quantities of impurities are acceptable so as to lower the flash point.
This is not normally desirable in most of the cleaning applications in
which we have tried the formulation of this invention. Care must be taken
that any alteration does not exceed the limits set forth in accordance
with this formulation; specifically, the flash point of the formulation,
if it is to be nonflammable must be 100 degrees Fahrenheit or higher when
measured by the closed cup method.
It has been found advantageous to have a formulation that has sufficiently
low toxicity, reported as Threshold Limit Value-Time Weighted Average
toxicity, (TLV-TWA toxicity). This is sometimes variously referred to only
as "TLV" or "TWA" (toxicity). It must be low enough to allow eight hours
continuous human exposure to at least 100 ppm without ill effects.
The Threshold Limit Value-Time Weighted Average (TLV-TWA) is the
time-weighted average concentration for a normal eight hour workday and a
forty hour workweek, to which nearly all workers may be repeatedly
exposed, day after day, without adverse effect. It is expressed in the
reference as parts per million (ppm) which is parts of vapor or gas per
million parts of contaminated air by volume at 25 degrees C. and 760 torr.
The optimum result has been found to be where only about 2 percent by
volume of a total amount of the formulation is the second ingredient with
the proportion of the first and major ingredient being about 98 percent by
volume of the first and second ingredients comprising the formulation. In
optimum formulations, our formulation has been found to be able to provide
a TLV-TWA toxicity well above 200 parts per million, since the major
ingredient has no established TLV toxicity. Even higher TLV toxicity
values can be obtained; for example, TLV-TWA value up to about 1000 parts
per million. As a consequence, the optimum formulation has extremely low
toxicity, or recognized high TLV-TWA toxicity value.
Table I hereinafter lists the properties of some typical glycol ethers and
glycol ether acetates It can be seen that propylene glycol methyl ether is
slightly too flammable since its flash point is only 97 degrees
Fahrenheit.
On the other hand, ethylene glycol methyl ether is too toxic, since its
maximum exposure limit is only 25 ppm. In like manner, ethylene glycol
butyl ether is too toxic, since its maximum exposure limit is only 50 ppm.
Ethylene glycol ethyl ether, ethylene glycol ethyl ether acetate, and
diethylene glycol methyl ether each evaporate too slowly.
Herein when the specific chemical is described, the allusion is to that
chemical alone without being significantly modified by the presence of
other ingredients.
TABLE I
__________________________________________________________________________
PROPERTIES OF GLYCOL ETHERS AND GLYCOL ETHER ACETATES
TLV-TWA
EVAPORATION RATE
FLAMMABILITY
TOXICITY
(based on n-Butyl
(Flash Pt.,
(Max Exposure
COMPOUND Acetate = 1) Deg. F) Limit, PPM)
__________________________________________________________________________
1)
ETHYLENE GLYCOL
0.5 110 25
METHYL ETHER
2)
ETHYLENE GLYCOL
0.3 120 100
ETHYL ETHER
3)
ETHYLENE GLYCOL
0.2 120 100
ETHYL ETHER ACETATE
4)
ETHYLENE GLYCOL
0.06 190 50
BUTYL ETHER
5)
DIETHYLENE GLYCOL
0.02 200 NONE ESTABLISHED
METHYL ETHER
6)
PROPYLENE GLYCOL
0.7 97 100
METHYL ETHER
7)
PROPYLENE GLYCOL
0.4 116 NONE ESTABLISHED
METHYL ETHER
ACETATE
__________________________________________________________________________
Deg. = Degrees
Pt. = point
Max = maximum
There are several other compounds in this family of chemicals as shown in
the Condensed Chemical Dictionary, 11th Ed., but they do not exhibit the
optimum chemical and physical properties as does the major ingredient
delineated herein.
Similarly, other ketones or aliphatic esters could be used instead of the
methyl isoamyl ketone or n-butyl acetate but such substitution may alter
the evaporation rate, toxicity and flammability. Care must be taken that
the alteration is not intolerably great.
Table II shows the properties of several ketones and aliphatic esters
compared with the ones described in this invention.
Herein when the specific chemical is described, the allusion is to that
chemical alone without being significantly modified by the presence of
other ingredients.
TABLE II
__________________________________________________________________________
TLV-TWA
EVAPORATION RATE
FLAMMABILITY
TOXICITY
(based on n-Butyl
(Flash Pt.,
(Max Exposure
COMPOUND Acetate = 1) Deg. F) Limit, PPM)
__________________________________________________________________________
KETONES
1)
METHYL ETHYL
KETONE 3.8 24 200
2)
METHYL PROPYL
KETONE 2.3 45 200
3)
METHYL ISOBUTYL
KETONE 1.6 73 100
4)
METHYL HEXYL
KETONE .1 160 100
5)
METHYL ISOAMYL
KETONE 0.5 96 100
ALIPHATIC ESTERS
6)
ETHYL ACETATE
4.1 24 200
7)
PROPYL ACETATE
2.3 55 200
8)
AMYL ACETATE
0.4 101 200
9)
N-BUTYL ACETATE
1.0 72 150
__________________________________________________________________________
Deg. = Degrees
Max 32 maximum
Pt. = point
The methyl ethyl ketone and the methyl propyl ketone have a higher
evaporation rate than desired. In addition, they are too flammable in that
their flash point is down to about 24 to 45 degrees F. These components
would lower the flash point of the formulation to under 100 degrees
Fahrenheit.
Methyl isobutyl ketone also evaporates too rapidly. Methyl hexyl ketone has
too low an evaporation rate. The methyl isoamyl ketone is about the
optimum ketone compound.
The methyl isoamyl ketone has about the optimum vapor pressure and by
virtue of its slow evaporation it is relatively non-toxic.
An alternative minor component is n-butyl acetate, an aliphatic ester. This
compound was selected from a list of aliphatic esters shown in Table II
based on their physical and chemical properties. Ethyl acetate and propyl
acetate evaporate too rapidly and their flash points are too low. Amyl
acetate has a satisfactory evaporation rate and flash point, but has a
strong odor even when diluted to 5 percent by volume. The n-butyl acetate
has a relatively low flash point, but it does not lower the flash point of
the total formulation to under 100 degrees Fahrenheit when mixed at 5 to
20 percent by volume.
An odor masking ingredient is frequently employed. Typical of an odor
masking ingredient is a concentration within the range of a trace up to
5.0 percent by volume of d-limonene, a C.sub.10 H.sub.16 cyclic
hydrocarbon.
Although there are several blends of cleaning formulations on the market,
none of these combinations exhibit the efficiency and have the scientific
approach employed in this invention.
The formulation can clean surfaces in preparation for applying sealants,
adhesives, paints and can effectively clean machinery, automobiles,
structures such as walls or floors or even the light weight parts for
aircraft. It can be used inside buildings and in non-ventilated areas with
no danger of fire or toxicity.
The formulation can be employed to clean a variety of different kinds of
soil such as oils, greases, waxes, uncured resins, dirt, stains, carbon,
marking inks, wet paints and others. In this way the surface is made ready
for further work as indicated in the preceding paragraph.
A formulation with a mild-odor is shown in Table III.
TABLE III
__________________________________________________________________________
OPTIMUM ALLOWABLE
CONCENTRATION
RANGE
(Percentage)
(Percentage)
__________________________________________________________________________
PROPYLENE GLYCOL METHYL
25 5-35
ETHER ACETATE
PROPYLENE GLYCOL METHYL
40 30-60
ETHER
ISOPARAFFINS (ISO-DECANE AND ISO-
28 10-33
UNDECANE IN ANY PROPORTION)
NORMAL BUTYL ACETATE 5 2-33
D-LIMONENE 2 trace-5
__________________________________________________________________________
The percentages given herein are percent by volume.
The ranges given in Table III have been formulated based on laboratory
tests. For example, it has been found that the combined concentrations of
propylene glycol methyl acetate and propylene glycol methyl ether must be
at least 65 percent in order for the formulation to have a satisfactory
cleaning efficiency. At least 5 percent of this total must be propylene
glycol methyl ether acetate to reduce the flammability. The concentration
of propylene glycol methyl ether acetate is also limited by its odor, 35
percent being the maximum desirable. These findings then set the range of
propylene glycol methyl ether acetate at 5 to 35 percent and the range of
propylene glycol methyl ether at 30 to 60 percent. In the case of normal
butyl acetate, it has been found that at least 2 percent is needed to
clean certain types of soils, particularly marking inks. On the other hand
if more than 15 percent is added, the flash point is lowered to the point
where the formulation becomes too flammable. The isoparaffins,
specifically iso-decane and iso-undecane, increase the flash point of the
formulation which is desirable. If, on the other hand, 65 percent is the
minimum concentration of the two glycol ethers and 2 percent is the
minimum concentration of the butyl acetate, the maximum concentration of
the isoparaffins becomes 33 percent. The d-limonene is added to improve
the odor. If more than 5 percent is added, the citrus odor becomes too
strong.
Table IV compares the properties of the mild-odor formulations with those
of the formulation described in an earlier filed application of which this
is a continuation-in-part. Table IV shows that the mild-odor formulation
is an efficient cleaner, has a low toxicity, is nonflammable at ambient
temperatures up to 91 degrees Fahrenheit, has a low vapor pressure and low
evaporation rate to reduce volatile organic compound emissions so it can
be used with the wipe cloth management system as described hereinafter in
subject invention to further reduce emissions. The mild-odor formulation
evaporates from surfaces at ambient conditions leaving no residue. It
conforms to government environmental regulations and has a mild, pleasant
odor. The new formulation has a wide application in industry where odors
associated with formulations such as the strong odors given hereinbefore
may be objectionable.
TABLE IV
__________________________________________________________________________
COMPARISON OF PROPERTIES OF
ORIGINAL AND NEW FORMULATIONS
Original Formulation
(From Pending Patent)
New Formulation
__________________________________________________________________________
Cleaning efficiency Excellent Good
Flash Point deg. Fahrenheit
110 91-101
Toxicity, TLV-TWA (max.
400 150
exposure limits)
Odor Strong Mild
Vapor pressure 4.5 6.4
(mm mercury @ 20 degrees C.)
Evaporation rate (n-butyl
30 50
acetate = 100)
Compatible with wipe cloth management
Yes Yes
system per pending patent)
__________________________________________________________________________
The new formulations described immediately hereinbefore have certain
properties which may make them less desirable than the original
formulation; for example, they may be more flammable or more toxic. About
50 percent of the workers may be bothered by the odor of the older
formulation. All the original and the new formulations are increasingly in
demand as a result of a Clean Air Act passed by Congress in 1990. As
indicated hereinbefore, this law curtails the use of some common solvent
cleaners such as chloroform, dichloromethane, methyl ethyl ketone, methyl
isobutyl ketone, toluene, trichloroethylene, trichloroethane, and xylenes.
A formulation which contains none of these curtailed ingredients but which
is an efficient cleaner, nonflammable, and has low toxicity and evaporates
slowly leaving no residue is desirable. This is particularly true where it
has a pleasant odor that will have wide acceptance in the manufacturing
industries. Where it is desired to eliminate any problem with
flammability, formulations have been developed which contain a higher
portion of higher flash point ingredients and a lower portion of low flash
point ingredients. For example, propylene glycol methyl ether acetate has
a flash point of 117 degrees Fahrenheit. By increasing the concentration
of this component to 55 to 75 percent (% by vol.) level as opposed to 25
percent in the flammable formulation, the flash point of the admixture is
increased. On the other hand, propylene glycol methyl ether has a flash
point as low as 89 degrees (although some batches are as high as 98
degrees). The flash point of the admixture is lower when the concentration
of the lower flash point ingredient is kept low. Care must be taken to
maintain a combination of the two ingredients mentioned above to at least
65 percent of the total formulation to maintain cleaning efficiency.
There are a large number of variations of the formulation available. If too
much propylene glycol methyl ether acetate (PMA) is added, the odor
becomes too strong. If too little PMA is added, the cleaning efficiency is
reduced. If too much propylene glycol methyl ether is added, the
flammability is increased. This is frequently intolerable. The proportion
of propylene glycol methyl ether must be decreased. If too little
propylene glycol methyl ether is included, however, the cleaning
efficiency is reduced. If too much isoparaffins are added, the cleaning
efficiency is reduced; if too little, the other components must be
increased to undesirable levels. N-butyl acetate is included in some of
the formulations to help clean certain types of inks and dyes. If too much
n-butyl acetate is present the formulation smells too "fruity" and the
flash point is reduced. If this is intolerable, then the proportion of
n-butyl acetate must be decreased.
Further details of the new formulation are shown in Table V. These
formulations differ from each other, each having specific advantages.
Formulation A is the least flammable and the least toxic and has the
lowest vapor pressure and evaporation rate. Formulation B has the mildest
odor of the three formulations. Formulation C is the best cleaner, being
composed of two components having good cleaning efficiencies.
Table VI along with a comparison of the formulations and properties of
earlier formulations that we have developed, show the advantages and the
industrial applications in terms of cleaning efficiency, flash point,
toxicity, odor, vapor pressure, evaporation rate and the like.
TABLE V
______________________________________
NONFLAMMABLE, MODERATE ODOR
CLEANING FORMULATIONS
Formulations
A B C
All. Opt. All. Opt. All. Opt.
Range Conc. Range Conc. Range Conc.
______________________________________
Ingredients
Propylene
65-75 65 55-75 55 60-75 60
Glycol
Methyl
Ether
Acetate
(PMA)
Propylene 5-10 10 25-40 40
Glycol
Methyl
Ether
(PM)
Isoparaffins
25-30 30 25-33 33
(C11, C12)
Butyl 2-5 5 2-5 2
Acetate
______________________________________
Concentrations are % by volume
Conc. = Concentration
Opt. = optimum
All. = allowable
TABLE VI
__________________________________________________________________________
COMPARISON OF PRIOR AND NEW FORMULATIONS
New
SERIAL NO.
SERIAL NO.
Formulations
07/614,228
07/686,180
A B C
__________________________________________________________________________
INGREDIENTS
Propylene 67-98
67-98
5-35 65 55 60
Glycol
Methyl
Ether
Acetate
(PMA)
Propylene 30-60 10 40
Glycol
Methyl
Ether (PM)
Isoparaffins 10-33 30 33
(C10, (C11,
(C11,
C11) C12)
C12)
Butyl 2-33 2-33 5 2
Acetate
Methyl 2-33
Isoamyl
Ketone
d-Limonene
0-5 0-5
PROPERTIES
Cleaning Efficiency
Excell Good Good
Good
Excell
Flash Point Degrees
110 112 91 105 101 101
Fahrenheit
Toxicity, TLV-
400 400 150 300 200 150
TWA
Odor Strong
Strong
Mild Mod.
Mod.
Mod.
Vapor Pressure
5.0 4.3 6.4 3.5 4.0 6.6
mm Hg
Evaporation rate
30 30 50 28 29 46
(butyl acetate
= 100)
Evaporate at
Yes Yes Yes Yes Yes Yes
Ambient Temp.
Residue after
None
None
None None
None
None
Evaporation
Curtailed Chemicals
None
None
None None
None
None
Use with Wipe-
Yes Yes Yes Yes Yes
Cloth Management
System
__________________________________________________________________________
*Concentrations are shown as % by volume
Isoparaffins are isoform
Mod. = Moderate
Excell Excellent
An improved series of mild-odor formulations have been developed for
facilities which are able to use flammable solvents and which prefer a
mild-odor. These formulations (Tables VII, IX, and X) are similar to those
shown in Table III. The differences are a wider allowable range of some of
the components and elimination of d-limonene. D-limonene has been
eliminated because it is not necessary to improve the odor and it has been
found that d-limonene is very slow to evaporate and may leave a residue.
TABLE VII
______________________________________
Compositions of New Mild-Odor Formulations
ALLOW- OPTIMUM
ABLE CONCENTRATION
RANGE (Percent By
(Percent By
Volume)
Volume) (A) (B)
______________________________________
PROPYLENE GLYCOL
0-50 25
METHYL ETHER
ACETATE
PROPYLENE GLYCOL
15-65 40 65
METHYL ETHER
ISOPARAFFINS (ISO-
0-35 30 30
DECANE AND ISO-
UNDECANE IN ANY
PROPORTION)
NORMAL BUTYL 0-35 5 5
ACETATE
______________________________________
The ranges given in Table VII have been formulated based on laboratory
tests. For example, it has been found that the combined concentrations of
propylene glycol methyl ether acetate and propylene glycol methyl ether
must be at least 65% in order for the formulation to have a satisfactory
cleaning efficiency. Concentrations of propylene glycol methyl ether
acetate over 50% have a strong odor. Therefore, since the maximum
concentration of propylene glycol methyl ether acetate is 50% and the
minimum combined concentration of propylene glycol methyl ether acetate
and propylene glycol methyl ether is 65%, then the minimum concentration
of propylene glycol methyl ether must be 15%. Furthermore, concentrations
of propylene glycol methyl ether over 65% would result in a blend with a
TLV-TWA of less than 150. Isoparaffins up to 35% may be added to provide a
more desirable higher TLV-TWA. Normal butyl acetate has been found to be
an efficient cleaner for certain dyes and inks; therefore concentrations
up to 35% may be included.
Table VIII shows the properties of the new mild-odor formulations. Even
though the TLV's are the same formulation (A) is less toxic by inhalation
than formulation (B) because of the lower vapor pressure. It is also
slightly less flammable. Formulation (B) has a milder odor than (A) due to
the absence of propylene glycol methyl ether acetate. Formulation (B) is
also faster drying. Both of these formulations are efficient cleaners,
have low toxicities, mild odors, and low evaporation rates to reduce
volatile organic compound emissions. The new mild-odor formulations
evaporate from surfaces at ambient conditions leaving no residue and they
conform to government environmental regulations. Although the new
formulations are flammable, they have a wide application in industry where
odors associated with formulations, given hereinbefore, may be more
irritating.
TABLE VIII
______________________________________
PROPERTIES OF NEW FORMULATIONS
(A) (B)
______________________________________
Cleaning efficiency good good
Flash point, F. 92 90
Toxicity, TLV-TWA 150 150
(max. exposure limit)
Odor mild mild
Vapor pressure 6.4 8.0
(mm mercury at 20 C.)
Evaporation rate 50 60
(n-butyl acetate = 100)
______________________________________
TABLE IX
______________________________________
COMPONENTS PERCENT BY VOLUME
______________________________________
Propylene Glycol 40
Methyl Ether Acetate
Propylene Glycol 25
Methyl Ether
Isoparaffins (Iso-decane &
30
Iso-undecane in any proportion)
Normal Butyl Acetate
5
______________________________________
TABLE X
______________________________________
COMPONENTS PERCENT BY VOLUME
______________________________________
Propylene Glycol 45
Methyl Ether Acetate
Propylene Glycol 20
Methyl Ether
Isoparaffins (Iso decane &
30
Iso-undecane in any proportion)
Normal Butyl Acetate
5
______________________________________
The formulations of Tables IX and X include propylene glycol methyl ether
acetate above 35% and up to about 50% by volume. These formulations will
have excellent cleaning abilities and have relatively mild odors, but both
will be flammable blends. The formulation of Table X will have a slightly
stronger odor than formulation of Table IX. The formulation of Table IX
will have a slightly stronger odor than the 35% Propylene Glycol Methyl
Ether Acetate blend. The formulation of Table X will have a higher flash
point (estimated at 95.degree. F.) than the formulation of Table IX, but
still under 100.degree. F. For some facilities, the higher flash point may
be desired. The formulation of Table IX has a higher flash point than the
35% Propylene Glycol Methyl Ether Acetate blend. There is no increase in
toxicity for these two blends over the 35% Propylene Glycol Methyl Ether
Acetate blend. The formulations of Table IX and X do not have hazardous
air pollutants.
Another aspect of this invention is the use of vapor-proof bags to store
the solvent-laden cloths to prevent the emission of volatile organic
compounds to the atmosphere. Several types of materials to form the bags
were evaluated for this application, including metal foils, various
plastics, and materials combined as coextruded multi-layer films. To
conduct these evaluations, normal butyl acetate was applied to wipe-cloths
which were then placed in a bag constructed of the material being
evaluated. The bag opening was tied closed and the bag weighed. The bag
was then reweighed after various time periods to determine the solvent
loss. The solvent loss using various bagging materials is shown in Table
XI. It is seen that metal foils such as 2 mil aluminum effectively
prevented permeation of solvent vapors, but the foils tore easily and were
difficult to seal into bags. Single layer plastics such as polyethylene,
polypropylene and polyolefins had high solvent losses, even with wall
thicknesses up to 10 mils. The best results were obtained with
multi-layered materials, particularly those having metal foil as one of
the layers. A bag constructed of 0.3 mil of aluminum foil in the center
with 1.0 to 1.5 mil layers of polyethylene coextruded and bonded to the
aluminum foil on each side lost less than 0.1% of the solvent in a 24 hour
period. This bag was also tear resistant and its opening was easy to tie
closed. Another coextruded material consisting of multi-layers of
polyethylene, polypropylene, and vinyl alcohol (bonded together) was also
effective, having a loss of 0.3% of the solvent in 24 hours. The
aluminized polyethylene bag was preferred, however, because of its low
solvent loss, ease of handling, and lower cost. It was found that the most
effective means of sealing the bag closed was by twisting the top of the
bag and sealing with wire ties or string. It must be cautioned that
staples are not to be used to close the bag because the staples create
holes through which solvent vapors will escape.
TABLE XI
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EFFICIENCY OF BAGGING MATERIAL TO
PREVENT SOLVENT PERMEATION
Solvent Loss
Material (% in 24 hrs)
Strength
______________________________________
4.6 mil Polyethylene
12.1 Tear resistant
10 mil Polyethylene
11.0 Tear resistant
1.1 mil Polyolefin
7.2 Tear resistant
4 mil Polypropylene
2.9 Tear resistant
2 mil Aluminum <0.1 Tears easily
2 mil Aluminum, Poly-
<0.1 Tear resistant
ethylene coextrusion
2 mil Polypropylene,
0.3 Tear resistant
Polyethylene, Vinyl
alcohol coextrusion
______________________________________
Although vapor-proof bags have been used to store certain food products
such as potato chips, their use for storing used solvent-laden wipe cloths
is not known to the inventors. It | | |
