Note: Descriptions are shown in the official language in which they were submitted.
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WATER-BASED EMULSION POLYMERS WHICH RESIST BLOCKING
This invention relates to emulsion polymers and to paints and other coatings
containing emulsion polymers.
Water-based coatings and paints are well known and have been sold
commercially for many years. These coatings and paints are based on emulsion
polymers,
which are referred to as latexes. In addition to the latex, these coatings
usually contain
additional ingredients such as pigments, opacifiers, coalescents and
crosslinkers, among
others.
Quite often, these water-based coatings and paints will contain a small
quantity of an organic solvent. These solvents tend to be volatile and produce
vapors when
the coating or paint is applied. For environmental and safety reasons, it is
desired to reduce
the level of solvent and other volatile components in the water-based coatings
and paints.
A problem frequently encountered with water-based coatings and paints is
"blocking". "Blocking" refers to the tendency of the coating or paint to
adhere to itself or to
have a tacky surface after drying. Water-based coatings and paints need to
form highly
coalesced films when they are dried at their particular application
temperature. To achieve
this high degree of coalescence, the emulsion polymer must either have a T9
below the
2 o application temperature, or else be used in conjunction with coalescing
solvents. Both
approaches usually lead to bad "blocking" properties of the coatings or
paints. Polymers with
a low T9 usually cause the coating to exhibit poor "final" blocking
properties, in that the
polymer will block even when completely dried. Coatings formulated with
coalescing
solvents dry slowly and therefore exhibit poor "early" blocking
characteristics for an extended
2 s period until drying is complete. When the level of coalescing solvent is
increased, this
blocking problem is often worsened because the coating or paint dries more
slowly. In both
cases, objects coated with these coatings tend to block when the coating is
applied and
when the objects are stacked. This blocking often causes the coating to fail
when the
objects are separated.
3o In addition, the coating or paint must be able to resist damage caused by
exposure to water and solvents such as are commonly present in household
cleaners.
Attempts to improve blocking resistance by blending hard components with soft
components
can lead to reduced resistance to water and/or solvents.
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It would therefore be desirable to provide an emulsion polymer which resists
both early and final blocking, water spotting and spotting from common
solvents such as
ethanol. It would also be desirable to provide a coating or paint composition
which is
similarly resistant.
s In one aspect, this invention is an aqueous emulsion having an aqueous
phase and a dispersed polymer phase, wherein the dispersed polymer phase
comprises
particles of a polymer of monomer mixture including
(a) from 5.5 to 15 percent, based on the weight of all monomers, of a mixture
of ethylenically unsaturated functional monomers, wherein said functional
monomer mixture
to includes:
( 2 ) at least 0.5 percent, based on the total weight of all monomers, of at
least one monomer having a carboxyl or carboxylate group
( 2 ) at least 0.8 toy percent, based on the total weight of all monomers, of
at
least one monomer having a sulfonic acid, sulfonate group or
15 sulfosuccinate group,
or both (1 ) and (2);
(b) from 0.5 to 10 percent, based on the weight of all monomers, of one or
more ethylenically unsaturated, addition polymerizable monomers) containing a
silicon atom
to which is bound at least one hydroiyzable group, provided that the linkage
between the
2o silicon group and the ethylenic unsaturation is not hydrolyzable;
(c) from 75 to 94 percent, based on the weight of all monomers, of a
nonfunctionalized vinyl aromatic monomer, a nohfunctionalized ester of acrylic
or
methacrylic acid, or a mixture thereof,
2s provided that when less than about 1.5 percent by weight of monomer (b) is
present, said monomer mixture further comprises
( d ) at least about 0.1 percent, based on the weight of all monomers, of a
monomer having at least two ethylenically unsaturated, addition polymerizable
groups.
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In a second aspect, this invention is an aqueous emulsion having an aqueous
phase and a dispersed polymer phase, wherein the dispersed polymer phase
comprises
particles of a polymer of monomer mixture including
(a) from 3.5 to 15 percent, based on the weight of all monomers, of a mixture
of ethylenically unsaturated functional monomers, wherein said functional
monomer mixture
includes:
( 1 ) at least 0.5 percent, based on the total weight of all monomers, of at
least one monomer having a carboxyl or carboxylate group
( 2 ) at least 0.8 percent, based on the total weight of all monomers, of at
to least one monomer having a sulfonic acid, sulfonate or sulfosuccinate
group,
or both (1 ) and (2);
(b) from 0.5 to 10 percent, based on the weight of all monomers, of one or
more ethylenically unsaturated, addition polymerizable monomers containing a
silicon atom
15 to which is bound at least one hydrolyzable group, provided that the
linkage between the
silicon group and the ethylenic unsaturation is not hydrolyzable;
(c) from about 75 to about 96 percent, based on the weight of all monomers,
of a nonfunctionaiized vinyl aromatic monomer, a nonfunctionalized ester of
acrylic or
methacrylic acid, or a mixture thereof;
2 o provided that when less than 1.5 percent by weight of monomer (b) is
present, said monomer mixture further comprises at least 0.1 percent, based on
the weight
of all monomers, of a monomer having at least two ethylenically unsaturated,
addition
polymerizable groups;
wherein said monomer mixture is polymerized in two stages, in which
2s monomers which together form a polymer having a T9 of less than 25°C
are polymerized in a
first stage and monomer which together form a polymer having a T9 of at least
80°C are
polymerized in a second stage.
In a third aspect, this invention is a coating composition comprising the
aqueous emulsion of the first aspect.
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The emulsion of this invention surprisingly exhibits excellent resistance to
both early and final blocking, even when dried at temperatures well above the
T9 of the
dispersed polymer particles. Moreover, this blocking resistance is not
obtained at the
expense of a significant loss of water and solvent resistance; this emulsion
provides for
adequate to excellent resistance to both water and ethanol/water mixtures.
The aqueous emulsion of this invention includes a continuous aqueous phase
and a dispersed polymer phase. The dispersed polymer phase is in the form of
particles of
a size such that they can remain stably dispersed in the aqueous phase. A
suitable size
range for the particles is from 40 nm to 350 nm in diameter ("diameter" here
referring to the
io longest dimension of the particle), preferably 50 to 120 nm.
The dispersed particles comprise a polymer which is prepared by
polymerizing a mixture of monomers of at least three different types. In this
context,
"mixture of monomers" or "monomer mixture" means only that the polymer
contains
repeating units from each member of the mixture, but does not require that all
the monomers
15 must be mixed together before polymerizing, or that the monomers must all
be polymerized
simultaneously. As discussed further below, the monomers may be polymerized
all at one
time, polymerized sequentially, polymerized in groups, or any combination of
these.
In the general case, the monomer mixture contains at least 5.5 weight
percent, up to 15 weight percent, of an ethylenically unsaturated functional
monomer.
2 o However, the level of the functional monomer may be reduced to as low as
3.5 percent or 3
percent when the emulsion polymer is prepared in a two-stage polymerization
reaction as
described below. For the purposes of this invention, a "functional monomer" is
one which
contains a highly polar group. Such functional monomers include those
containing one or
more ionic groups, such as sulfonate or carboxylate groups, precursors of such
ionic groups,
25 such as sulfonic acid and carboxyl groups, and other highly polar groups
which, although
they are not ionic in character, impart high polarity to the monomer. These
groups include
hydroxy, poly(oxyethylene), nitrite, and amide. Specific functional monomers
useful in this
invention include methacrylic acid, acrylic acid, fumaric acid, malefic acid,
itaconic acid,
succinic acid, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylamide,
acrylonitrile,
3 o methacrylonitrile, acetoxy ethyl methacrylate, acetoxy ethyl acrylate,
acetoacetoxy ethyl
methacrylate, sodium styrene sulfonate, sodium 1-acrylamido-2-methylpropane
sulfonate,
sodium alkyl allyl sulfosuccinate (in which the alkyl group contains up to
about 20 carbon
atoms), and glycidyl methacrylate. Sulfonated monomers or monomers with a
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sulfosuccinate group, containing a long hydrocarbon chain (C6 or higher,
preferably up to
C2o) often operate as a surfactant during the polymerization reaction; in that
case, added
surfactant may be minimized or unnecessary. However, when such sulfonated or
sulfosuccinated monomers are used, it is preferred to also include another
sulfonated
s monomer which does not contain a long-chain hydrocarbon group. Those
monomers
containing acid groups may be used in the form of their salts, preferably
salts with a
monovalent cation, more preferably of an alkali metal or ammonium salt.
Conversely, those
monomers containing acid salt groups may be used in the free acid form.
The functional monomer mixture includes one or more monomers containing
1 o at least one carboxyl or carboxylate group or one or more monomers
containing at least one
sulfonic acid, sulfonate or sulfosuccinate group. Preferably, monomers of both
type are
present. The sulfonate group is preferably in salt form, with the cation being
monovalent
and preferably an alkali metal or ammonium. When present, the sulfonated
monomers)
constitutes at least 0.8 percent, preferably at least 1.5 percent, more
preferably at least 2
15 percent, up to 10 percent, preferably up to 5 percent, more preferably up
to 4 percent, based
on the combined weight of all monomers.
When a monomer containing a carboxyl or carboxylate group is present, it
constitutes at least 0.5 percent, preferably at least 1.5 percent, more
preferably at least 2.5
percent, up to 10 percent, preferably up to 5 percent of the total weight of
all monomers.
2 o The second type of monomer is one or more ethyienically unsaturated
monomers) containing a silicon atom to which is bound at feast one
hydrolyzable group. In
those monomers, the ethylenic unsaturation is bound to the silicon atom
through a linkage
which is not itself hydrolyzable. The monomers) of this type constitute at
least about 0.5
percent, preferably from about 1.6 percent, more preferably at least about 2
percent, up to
2s 10 percent, preferably up to 7 percent, more preferably up to 4 percent of
the weight of all
monomers.
The monomers of the second type have at least one, preferably at least two,
and more preferably three hydrolyzable groups bound to the silicon atom.
Suitable such
hydrolyzable groups include aceto (-C(H)=O) and halogen groups, and groups of
the form
3 0 -O-R, wherein R is branched-, straight-chain or cyclic hydrocarbyl, or a
hydrocarbyl group
which is substituted with ether, hydroxyl or other inert substituents.
Examples of such
hydrolyzable groups include aceto groups and those in which the R group
corresponds to
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methyl, ethyl, propyl, 1-methylethyl or 1-methyl-2-methoxyethyl. Illustrative
monomers of the
second type include methacryloxypropyl trimethoxy silane, vinyl tris(1-
methoxypropyl-2-oxy)
silane, vinyl triethoxy silane, vinyl trimethoxysilane, 'y methacryloxy propyl
trimethoxy silane,
or vinyl triacetoxysilane.
When less than 1.5 percent of the monomer of the second type is used, then
the monomer mixture must also contain at least 0.1 percent of a monomer having
at least
two ethylenically unsaturated, addition polymerizable groups. In other cases,
this last type
of monomer is optional, but not required. This type of monomer may constitute
up to 5
percent of the monomer mixture, preferably up to 1.5 percent. Examples of such
monomers
io include divinylbenzene and ethylene glycol dimethacrylate. Preferably, this
monomer
contains at least two ethylenically unsaturated groups of significantly
differing reactivity, such
as allyl methacrylate or allyl acrylate. When the monomer contains
ethylenically unsaturated
groups of differing reactivity, it is possible to provide a polymer which can
be post-
crosslinked, because the more reactive monomer will polymerize as the polymer
is
15 prepared, but the less reactive unsaturated group will remain unreacted and
available for
reaction at a later time, such as during the curing of the polymer.
The third type of monomer is one or more nonfunctionalized vinyl aromatic
monomer(s), acrylic esters or methacrylic esters. By "nonfunctionalized", it
is meant that the
monomer contains (1 } no groups which cause the monomer to be highly polar (as
defined
2 o above), (2) no groups other than a pofymerizable group which react during
the course of
polymerization, and (3) no silicon atoms having hydrolyzable substituents.
Suitable such
monomers include styrene, a-methyl styrene, vinyl toluene, vinyl naphthalene,
any of which
can be inertly-substituted, such as with alkyl or alkoxyl groups; acrylic and
methacrylic esters
in which the ester group is C,-CZO alkyl, preferably Cz-CB alkyl, such as
butyl acrylate,
25 2-ethylhexyl acrylate, butyl methacrylate, 1-ethylhexyl acrylate, methyl
and methacrylate.
The monomer or monomers of the third type can be selected to provide
desirable properties to the polymer. In particular, the monomers can be
selected so that the
dispersed polymer particles have a T9 within a desired range, or so that the
polymer particles
will form a film at a desired temperature. For example, when the third type of
monomer is
3 0 largely selected from "hard monomers" like styrene and/or methyl
methacrylate and/or
tertiary-butyl methacrylate, the T9 and the minimum film formation temperature
(MFFT) of the
resulting polymer tend to be high, such as, for example above 35°C,
preferably above 60°C.
On the other hand, when the third type of monomer is largely selected from
"soft monomers"
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like n-butyl acrylate and/or n-hexyl acrylate and/or n-heptyl acrylate and/or
2-ethyl hexyh
acrylate, then the T9 and MFFT tend to be lower, such as below 35°C,
preferably below
15°C, more preferably less than or equal to 6°C. By selecting
the third type of monomer
properly, the T9 and MFFT of the polymer particles may be adjusted to a
desired value.
s The MFFT is measured by casting a 150 ffm film of the emulsion on a heating
plate that has a temperature gradient. The film is dried and the minimum
temperature at
which a coherent film is formed is recorded as the MFFT.
The emulsion of this invention is conveniently prepared by polymerizing the
monomer mixture just described in an emulsion polymerization in an aqueous
phase. Such
1 o polymerization methods are well known and are described, for example, in
Emulsions:
Theory and Practice, by P. Becher Reinhold, New York (1959), High Polymer
Latices, by D.
C. Blackley, Pamerton Publishing Co., New York (1966); and Emulsion Polymer
Technology,
by Robert D. Athey, Jr. Marcel Dekker, Inc., New York (1991 ).
In general, the emulsion polymerization process includes mixing the
is monomers into a continuous aqueous phase under agitation sufficient to
disperse the
monomers into fine droplets. Unless one or more of the monomers has surface
active
characteristics, one or more surfactants are present in order to form micelles
as reaction loci
and to form a stable emulsion having discrete particles of desirable size. A
free radical
initiator or redox catalyst is usually employed to provide an acceptable rate
of polymerization
2 o and a high conversion of monomers to polymer.
The monomers may be added to the aqueous phase all at once in a
batchwise operation, or all of a portion may be added continuously or in
increments as the
polymerization proceeds. The different monomers may be added at different
times during
the polymerization, or at varying relative rates at different times, or at the
same relative rates
2s throughout the polymerization.
Seed polymer particles may be added at the start of the polymerization in
order to help control the nucleation of particles and the size of the final
polymer particles.
The weight of the seed particles is preferably no greater than 2.0 percent of
that of the
monomer mixture; in such a case, the composition of the seed particles is
ignored when
3 o calculating the amounts of the various monomer types in the monomer
mixture.
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In an illustrative polymerization process, water, surfactant and optional seed
particles are initially charged #o a suitable reactor and heated to the
desired polymerization
temperature. The desired polymerization temperature depends on the particular
catalyst
and monomers employed, and typically ranges from 30°C to 100°C,
preferably from 50°C to
s 100°C, more preferably from 60°C to 100°C. The initial
charge to the reactor may include all
or a portion of the monomer mixture. After the initial charge is heated to the
desired
temperature, one or more streams is fed to the reactor. One of those streams
contains the
free radical initiator (or redox catalyst). The monomer mixture may be added
in one or more
separate streams. Additional surfactant may also be added, either as a
separate stream or
to mixed with the catalyst or one or more of the monomers. When the monomers
are not
added together as a single mixture, they can be added as two or more separate
streams,
which may be added simultaneously, sequentially, or staggered with respect to
each other.
Following the addition of all streams, the reactor contents are typically
heated for a period to
complete polymerization. Often, this post addition heating is conducted at a
higher
15 temperature.
Alternatively, a two-stage polymerization process can be used. This two-
stage process has the advantage of requiring a smaller amount of the
functional monomer.
In the two-stage process, monomers selected from one or more of the types
previously
described, which together from a polymer having a T9 of 25°C or less,
are polymerized in a
2o first stage. The monomers polymerized in the first stage may or may not
contain a
functional monomer, and may or may not contain the monomer containing a
silicon atom
having hydrolyzable substituents; all that is required is that the first stage
monomers
polymerize to form a polymer having the requisite T9. The monomers polymerized
in the first
stage can be mixed and polymerized, or may be fed into the reaction mixture as
separate
2s streams. One or more of the monomers polymerized in the first stage may be
added as part
of the initial charge to the reactor, with the remaining monomers in the first
stage added as a
stream. Once the first stage monomers are added, they are polymerized to a
conversion of
at least 70 weight percent, preferably at feast 80 weight percent, and then
the second stage
monomers are added. The second stage monomers are selected from the types
described
3 o before, and are chosen so that they form a polymer having a T9 of at least
60°C. The
second stage monomers may or may not contain a functional monomer, and may or
may not
contain the monomer containing a silicon atom having hydrolyzable
substituents; all that is
required is that the second stage monomers polymerize to form a polymer having
the
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requisite T9. The functional monomers and the monomer containing the silicon
atom having
hydrolyzable substituents may be added in either the first stage, the second
stage, or both.
In this invention, all references to Tg are those obtained by differential
scanning calorimetry (DSC) on a dried latex sample made by pouring one drop of
latex into
an aluminum crucible and drying for 12 to 20 hours at room temperature in a
desiccator.
The samples are evaluated using a Mettler DSC 30 calorimeter, scanning at a
rate of
10°C/minute over a range of -40 °C to 110°C.
In some cases, it may be difficult to measure the separate T9's of the polymer
using DSC. In those cases, the T9 of the polymer formed in each stage can be
determined
Zo by polymerizing the monomer or monomer mixture alone in a single stage
polymerization
process, and measuring the T9 of the resulting polymer in the manner just
described. For
example, the T9 of a styrene/2-ethylhexyl acrylate mixture can be determined
by
polymerizing that mixture in a single-stage polymerization, and measuring the
T9 of the
resulting polymer. To the extent that the T9 is affected by the selection of
reaction conditions
15 such as temperature and free radical initiator, those conditions should be
kept constant
when T9 is determined in this way.
A convenient way to estimate the T9 of a polymer formed from a particular
monomer mixture is through the Fox equation:
1/T9AN = wA/T9A + wB/T9B = . . . +wN/T9N
2 o wherein A, B and N represent individual monomers in the mixture containing
N monomers,
wA, wB and wN represent the weight fractions of monomers A, B and N,
respectively, TgAN
represents the T9 of the polymer formed, and T9A, T9B and TeN represent the T9
of
homopolymers of monomers A, B and N, respectively. See T.G. Fox, Bull. Am.
Physics
Soc., vol. 1 (3), page 123 (1956). By using the Fox equation, it is possible
to screen
25 combinations of monomers to estimate which combinations will provide a
polymer having the
required T9.
The amount of monomers added and polymerized is selected so that the
resulting polymer emulsion has a desired solids content, and the copolymer
particles have a
desired size. Preferably, the resulting emulsion has a solids content from 10
to 70 percent
3 o by weight, more preferably from 25 to 55 percent by weight, and the
copolymer particles
have a volume average diameter from 40 nm to 350 nm, preferably from 50 to 120
nm.
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Any surfactant which stabilizes the monomer mixture as discrete droplets and
the subsequent copolymer as discrete particles in the aqueous phase can be
used. The
surfactant may be of the nonionic, anionic or amphoteric type. Exemplary
surfactants
include alkali metal alkyl carboxylates, polyoxyethylene alkyl phenols, linear
alkyl sulfonates,
s alkyl aryl sulfonates, alkylated sulfosuccinates, Cs Czo amine oxides, N,N-
bis(carboxyl alkyl)
and Cs Czo alkyl amines. SIPONATETM A246L brand surfactant (available from
Rhone
Poulenc), sodium dodecyl benzene sulfonate, sodium lauryl sulfate, disodium
dodecyldiphenylether disulfone, N-octadecyl disodium sulfosuccinate, dioctyl
sodium
sulfosuccinate, N,N-bis-carboxyethyl lauramine, and sulfonated alkylated
phenyl ethers such
so as DOWFAX* 2EP and DOWFAX* 2A1 (Trademark of The Dow Chemical Company and
both are available from The Dow Chemical Company), are all suitable
surfactants. The
surfactant is advantageously used in an amount from 0.1 to 2 percent,
preferably from 0.1 to
0.5 percent, based on the weight of the monomer mixture.
Suitable free radical initiators include peroxy compounds such as
15 peroxydisulfates (commonly known as persulfates), perphosphates, t-butyl
hydroperoxide,
cumene hydroperoxide and hydrogen peroxide. Ammonium persulfate, sodium
persulfate
and potassium persulfate are preferred initiators. Redox catalysts, which are
activated in the
water phase through a water-soluble reducing agent, can also be used. The free
radical
initiator is advantageously used in an amount from 0.01 to 5 percent,
preferably 0.1 to 2
2 o percent, based on the weight of the monomers. If desired, an amount of
initiator or catalyst
in excess of the foregoing amounts may be added after the addition of the
monomer
streams, in order to finish off the polymerization.
When the monomer mixture contains a monomer having free acid groups,
and in particular free carboxyl groups, it is preferred to stabilize the
resulting polymer
2s emulsion by adjusting the pH to above 5Ø This can be done by adding a
fugitive base like
ammonia, dimethyfamine, diethyl amine, aminopropanol, ammonium hydroxide or 2-
amino-
2-methyl-1-propanol, or through the addition of an alkali such as sodium
hydroxide,
potassium hydroxide or sodium, potassium or ammonium carbonate. This base may
be
added toward the end of the addition of the monomer stream(s), after all the
monomer
3 o addition has been completed, or after the polymerization reaction is
finished.
Other ingredients can also be used during the polymerization process as
desired, such as chain transfer agents, buffers, or preservatives.
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Following the polymerization, the resulting emulsion may be steam-stripped
or otherwise treated to remove impurities and unreacted monomers.
The emulsion of this invention can be formulated into a variety of paints and
coatings. The coatings can be formulated for use in a wide variety of
applications, and the
selection of the emulsion of this invention for use in the coating does not
require any special
ingredients or formulating techniques. Accordingly, those ingredients and
paint and coating
formulations which are well understood in the art may be used to formulate
paints and
coatings with the emulsion of this invention.
The latex can be formulated in clear and pigmented coatings and paints. The
1 o pigmented formulation, for example, will generally contain a filler,
opacifying agent or
pigment, such as calcium carbonate, talc, silica, aluminum hydroxide, glass
powder, titanium
dioxide, zinc phosphate, red oxide, carbon black, Hansa Yellow, Benzidine
Yellow,
Phthaiocyanine Blue, or Quinacridone Red. These are generally used in amounts
sufficient
to provide the coating with a pigment volume concentration of 15 to 80
percent.
is In addition, the formulation may contain inorganic dispersants such as
sodium
hexametaphosphate or sodium tripolyphosphate, organic dispersants such as the
pofycarboxylic acid polymers (for example, NopcoperseT"~ 44c, from Summopco
Co., Ltd.
and OrotanT"~ 681, from Rohm & Haas); wetting agents; thickeners such as
polyvinyl
alcohols, polyurethanes such as Acrylsol RMB, from Rohm & Haas, and cellulosic
2o derivatives; crosslinking agents such as water soluble polyvalent metal
salts, aziridine
compounds, water-soluble epoxy or melamine resins, or water dispersible
blocked
isocyanates; surfactants; matting agents and defoamers. Solvents such as
alcohols, glycol
ethers, hydroxy-tertiary amines, ketoximes, active methylene compounds and
lactams may
also be added. However, it is an advantage of this invention that the use of
coalescing type
2s solvents are not necessary in order to obtain good early and final blocking
properties.
The following examples are provided to illustrate the invention, but are not
intended to limit
its scope. All parts and percentages are by weight unless otherwise indicated.
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examples 1. 1 a and 2-15
A. Preparation of the Latexes
The following general procedure was used to make latex Examples 1, 1 a and
2 to 15. The composition of the monomer mixture used in each Example is given
in Table I.
In each case, a latex with approximately 42.5 percent solids was obtained.
A stainless steel reaction vessel is charged with 81 parts of deionized water
and 0.42 part of sodium C,o-,2 alkyl allyl sulfosuccinate and heated to
80°C. Then, 10
percent of the total charge of styrene (when used), 2-ethyl hexyl acrylate and
methyl
methacrylate (when used) are fed to the reactor over 20 minutes. Following the
addition of
i o the monomer stream, the contents of the reaction vessel were held at
80°C while feeding
0.12 part potassium persulfate dissolved in 5.25 parts water for 30 minutes to
form seed
polymer particles. Three streams were then fed to the vessel, all starting at
the same time.
The first stream contained the reminder of the styrene, 2-ethyl hexyl acrylate
and
methacrylic acid and methacryl oxypropyl trimethoxy silane, and was added to
the reactor
s5 over 170 minutes. The second stream consisted of the sodium p-
styrenesulfonate, the rest
of the sodium alkyl(C,o-,2) alfyl sulfosuccinate and 28 parts of water. It was
added over 180
minutes. The third stream contained 0.35 parts of potassium persulfate and
15.75 parts
water, and was added over 190 minutes. After the streams were completed, the
reaction
temperature was held at 80°C for an additional 120 minutes to complete
polymerization.
2o The monomer compositions used are given in the following table.
All amounts provided are parts by weight. The monomers used in making the
in situ seed particles are included, since the seeds constitute in excess of 5
percent of the
mass of the final polymer.
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TABLE I
Example Styrene EHA' MMA2 MAA3 NaSS AASSS MPTSs
No.
1 36.8 50.0 0 6.8 1.7 1.7 3.0
1 A 37.8 50.0 0 6.8 1.7 1.7 2.0
2 37.2 50.0 0 6.8 1,7 1.7 1.7
3* 35.95 52.5 0 6.8 1.7 1.7 0.75
4 25.1 50.0 14.15 5.1 1.7 1.7 2.25
25.1 50.0 13.3 6.8 0.85 1.7 2.25
6 25.1 50.0 7 4.85 5.1 1.7 1.0 2.25
7 25.1 50.0 12.9 6.8 0.85 7.35 3.0
8 25.1 50.0 15.35 5.1 0.85 1.35 2.25
9 25.1 50.0 14.0 6.8 0.85 1.0 2.25
25.1 50.0 13.75 5.1 1.7 1.35 3.0
11 25.1 50.0 14.95 5.1 0.85 1.0 3.0
12 25.1 50.0 14.25 5. i 0.85 1.7 3.0
13 25.1 50.0 12.8 6.8 1.7 1.35 2.25
14 10.0 50.0 26.8 6.8 1.7 1.7 3.0
0 50.0 36.8 6.8 1.7 1.7 3.0
*Also contains 0.6 parts by weight allyl methacrylate;
s ' 2-ethylhexyl acrylate;
2 Methyl methacrylate; 3 Methacrylic acid;
" Sodium styrene sulfonate;
5 Sodium alkyl (C,o-,2}allyl sulfosuccinate;
6 y-methacryloxy propyl trimethoxysilane (commercially available from DOW
Corning as Z-
10 6030.
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B. Evaluation of the Latexes
Multiple films were prepared from each of Latex Example Nos. 1-15. The
films were cast on a black plastic foil commercially available from Leneta
Company (Leneta
foil) at a wet thickness of 150 pm. The resulting films were evaluated for hot-
blocking
s resistance, water spot resistance and ethanol/water spot resistance as
follows.
For hot-blocking resistance testing, duplicate film samples were dried for one
day and others for one week at ambient temperature (approximately 21
°C) in a room held at
a constant relative humidity of 50 percent. Two duplicate films were blocked
at 50°C for two
hours under a weight of 4 kg/cm2, and then peeled apart. The films were then
visually
1 o inspected for damage and rated on a scale of from 0 (complete destruction)
to 5 (no
damage). The results of this blocking test are as reported in Table II. The
values reported
include a composite rating of the samples cured for 1 day and those cured for
one week.
For water spot resistance testing, a drop of water was applied to a film
sample and covered with a watch glass. The time required for the film to
visibly whiten was
15 rated on a scale of (-) (whitening in less than one hour), (0) (whitening
occurred after more
than one hour but less than four hours, and (+) (no more than barely
observable whitening
after four hours). The results of this water spot resistance test are as
reported in Table II.
For ethanol/water spot resistance testing, a filter paper soaked in a 50/50
ethanol/water mixture was placed onto the film, covered with a watch glass and
visually
2o inspected after four hours. The results were evaluated on a +/- scale, with
(+) indicating no
more than barely observable whitening after four hours, which faded within 30
minutes after
the filter paper was removed and (-) indicating easily visible whitening which
required greater
than 30 minutes to fade. The results of this testing are also reported in
Table II.
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TABLE II
Example No. Blocking Water Spot Ethanol/ Minimum Film
Rating Resistance Water Formation
Rating Resistance Temp., C
Rating
1 5 + + 4
2 5 + + 5
3 4_5 + _ 1
4 5 + _. 0
5 + _
6 5 + + 0
7 4-5 +
8 4-5 + + 3
9 4-5 + + 0
4 + + 0
11 4-5 0 + 3
12 4-5 0 5
13 4-5 + + 0
14 4-5 + + 4
4-5 + + 5
As can be seen from the data in Table II, each of these latexes has excellent
early and final blocking resistance and good to excellent resistance to water
and ethanol
spotting.
C. Evaluation of Coating Formulations.
C1. Clear Coatings
Clear Coating Formulations 1 to 9 and 11 to 15 were made from each of
1 o Latex Examples 1 to 9 and 11 to 15, respectively, by blending the
following components at
room temperature:
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TABLE III
Latex (50% solids) 84 parts by weight
Water 11 parts by weight
Dehydran 1293a 0.3 parts by weight
Surfynol 104Eb 0.3 parts by weight
Byk 346' 0.3 parts by weight
Ammonia (25% aq. sol.) 0.5 parts by weight
Acrysol RM8d (10% active) 0.2 parts by weight
Syloid ED 508 2.5 parts by weight
°A defoamer commercially available from Henkel;
°a nonionic tenside commercially available from Air Products;
s 'a wetting agent commercially available from Byk Chemie;
°a polyurethane thickener commercially available from Rohm & Haas as
30% solution;
ea matting agent commercially available from W.R. Grace & Co.
Each of Clear Coating Formulations 1 to 9 and 11 to 15 was tested for
s o blocking under four sets of conditions. The results are as reported in
Table III below. Under
Condition 1, 150 pm (wet thickness) films are applied to Leneta foil and dried
for two hours
at approximately room temperature. Samples of the films were blocked
(Condition 1 A) for 1
hour at 50°C under a weight of 0.5 metric ton/square meter and other
samples were blocked
(Condition 1 B) for 24 hours at room temperature and under a weight of 1
metric ton/square
is meter. The films were then separated and evaluated as described above.
Under Condition 2, 150 pm (wet thickness) films were applied to Leneta foil
and dried for 48 hours at approximately room temperature. Some samples of the
films were
blocked (Condition 2A) for 24 hours at 50°C under a weight of 1 metric
ton/square meter and
other samples were blocked (Condition 2B) for 24 hours at room temperature and
under a
2 o weight of 1 metric ton/square meter. The films were then separated and
evaluated as
described above.
Under Condition 3, 100 p.m (wet thickness) films were applied to Leneta foil
and dried for 48 hours at approximately room temperature. Samples of the films
were
blocked for 12 hours at 35°C under a weight of 2 metric ton/square
meter. The films were
2s then separated and evaluated as described above.
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Under Condition 4, two coatings of 150 pm (wet thickness) films were applied
to beech wood and dried for 48 hours at approximately room temperature.
Samples of the
films were blocked (Condition 4A) for 2 hours at 50°C under a weight of
2.7 metric
ton/square meter and other samples were blocked (Condition 4B) for 24 hours at
room
s temperature and under a weight of 2.7 metric ton/square meter. The films
were then
separated and evaluated as described above.
Water/ethanol resistance was evaluated for all coatings by applying a 150 ~.m
(wet thickness) film of the coating on samples of beech wood and drying at
ambient
conditions for 30 minutes, followed by application of a second 150 pm film and
drying under
Zo ambient conditions. Resistance to spotting by an ethanoUwater mixture was
evaluated on
multiple samples which were dried for two hours after application of the
second film, and on
other samples which were dried for 24 hours after application of the second
film. The
samples were evaluated by applying to each of them a filter paper soaked in a
50/50
ethanol/water mixture. The filter paper was removed from various samples after
15 minutes,
15 30 minutes and 2 hours. The films were then visually examined 24 hours
after the filter
paper was removed.
The films are tested for water spotting resistance in the same manner, except
that the filter paper is removed from various samples after 30 minutes, 1 hour
and 2 hours.
The results of the ethanol/water spotting and water spotting tests were rated
20 on a scale from 0 to 5, with 5 being best. These results are as reported in
Table IV below.
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TABLE IV
Coating Blocking Blocking Blocking Blocking
Example No. Condition Condition Condition Condition
1 A/1 B 2A/2B 3 4A/4B
1 2-3/4-5 4/4-5 3-4 4/4-5
2 5/4 1-2/4-5 4-5 3-4/3-4
3 5/5 5/5 5 4-5/4-5
4 4/4 4/4-5 3/a 4/4
3-4/3-4 3/5 3 2-3/4-5
6 4/4 3-4/5 3 4/4
7 4-5/5 5/5 4 4/5
8 3-4/3 3-4/4 3 3/4
9 5/5 4/5 4-5 4-5/4
11 4/3-4 4/5 4 4/4-5
1 2 0/0 ' 2/3-4 1-2 2-3/4
13 3 /4 5/5 1 4/4-5
14 4-5/5 4-5/5 4 4/5
4/4-5 4-5/5 4 4-5/4-5
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TABLE V
Coating Water Water Ethanol/ WaterEthanol/ Water
Example Resistance, Resistance, Resistance, Resistance,
No. 2 24 2 hr 24
hour D in hour D in D in 2 hour D in 2
' '
1 4/3-4/3 4-5/4/3-4 3/3/2-3 3/3/3
2 3/3/5 5/3/5 3/2/4 4-5/3/4-5
3 3/3/3-4 4-5/3/3 3/2/3 1/-/3
4 3/3/3 4/4/4 4/4/3-4 3-4/3/3
4/4/3-4 4/4/4 4/4/4 3/3/2-3
6 2-3/2-3/2-3 3-4/3-4/3 3-4/3-4/3-4 3/2-3/2-3
7 2-3/2/2 3-4/3-4/3 3-4/3-4/3-4 3/2-3/2-3
8 3-4/3/3-4 4-5/4/3-4 3-4/3-4/3-4 4-5/4-5/4
9 2/2-3/3 3/3/2-3 3/3/3 3-4/3/3
11 4-5/4/4 3-4/3-4/3 4/4/4 3-4/3/3
12 4/3-4/3-4 4/3-4/3-4 2-3/2/2 2-3/2-3/2-3
13 4/3-4/3-4 4-5/4/4 3/3/2-3 2-3/2-3/2-3
14 Not done 4-5/4/2-3 Not done 3-4/3/3
Not done 4-5/4/3-4 Not done 5/3-4/3
"_,. .
_
~mues repo~ea Tor ~u mmnei~ nouriz nour exposure time.
2Values reported for 15 minute/30 minute/1 hour exposure time.
C2. Pigmented Coatings
Examples 1 and 1 B were evaluated in a pigmented coating designed for
architectural gloss paint applications in the following formulation:
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TABLE VI
Raw Materials Parts by weight
Propylene glycol 6.05
Dehydran 1293 0.24
Orotan 6818 (35%)1.66
Triton X 100 0.10
Acrysol RM 1020' 1.46
Tiona RCL-535 20.41
Latex (42%) 67.14
Dehydran 1293 0.10
eOrotan 1 is an anionic
88 dispersant commercially
available from
Rohm & Haas;
Triton
X100 is
a nonionic
surfactant
commercially
available
from Union
Carbide;
s 'Acrysol
RM 1020
is a polyurethane
thickener
commercially
available
from Rohm
& Haas;
e'Tiona
RCL-535
is titanium
dioxide
commercially
available
from SCM
Chemicals.
The pigmented coatings were prepared by mixing the first four ingredients
and grinding them together for 20 minutes, and then adding the remaining
ingredients in the
Zo order listed, with slow stirring.
The pigmented coatings were tested for blocking resistance at ambient and at
elevated temperature, 20° gloss and water, ethanol and hand cream
resistance according to
the following test conditions:
23°C Blocking resistance:
15 150 Nm wet thickness films were applied to Leneta foil. Some samples were
dried for 1 day and others were dried for 7 days at a temperature of
23°C and 50 percent
relative humidity. Identically dried films are blocked for 24 hours at
23°C and 50 percent
relative humidity under a load of 4 kg/ 25 cm2. The films were then pulled
apart and the
force required to pull them apart was rated on a scale of 0 to 5, with 5
meaning that no force
2 o was required to separate the samples and 0 meaning that the films cannot
be separated.
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50°C Blocking resistance (Hot Blocking Resistancy
150 Nm wet thickness films were applied to Leneta foil. Some samples were
dried for 1 day and others were dried for 7 days at a temperature of
23°C and 50 percent
relative humidity.
s Identically dried films were blocked for 1, 3 or 5 hours at 50°C/50
percent
relative humidity under a load of 4 kg/25 cm2. The films were then pulled
apart and the force
required to pull them apart was rated on a scale of 0 to 5, with 5 meaning
that no force was
required to pull them apart and 0 meaning that the samples cannot be pulled
apart. The
amount of surface damage was also evaluated, and reported as a percentage of
the total
to surface area.
20° Gloss:
The paints were applied with a drawdown bar (150 Nm wet film thickness) on
glass, dried for 1 day at 23°C and 50 percent relative humidity and
evaluated for 20° gloss
using a Byk Glossmeter.
15 Water/Ethanol/Hand cream resistance'
The pigmented coatings were applied on glass with a drawdown bar (150 Nm
wet film thickness), dried for 7 days at a temperature of 23°C and 50
percent relative
humidity and evaluated for water resistance by applying a drop of water on the
dried film for
either 5 minutes or 30 minutes. The film was evaluated for softening and
formation of
2 o blisters 10 minutes after the water was removed, and rated on a scale of 0
to 2, with 2
meaning no film softening, 1 indicating slight film softening, 0 indicating
severe film
softening. The coatings were tested for ethanol and hand cream resistance in
the same
manner.
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TABLE VII
example No. 1 1 B
23C Blocking resistance
after 1 day drying 3/0% 3/20%
after 7 days drying 4/0% 4/0%
50C Blocking resistance
after 1 day drying, 1 hr 3/0% 3/20%
blockin
after 1 day drying, 3 hrs 3/20% 3/40%
blockin
after 7 days drying, 1 hr 4/0% 4/0%
blockin
after 7 days drying, 5 hrs 4/0% 4/0%
blockin
20 Gloss 51 % 51
Water resistance
after 5 min 2 2
after 30 min 2 1
Hand cream resistance
after 5 min 2 2
after 30 min 1 1
Ethanol resistance
after 5 min 2 2
after 30 min 2 2
Exam,~les 16 to 19
Latex Example 16 was prepared in the same manner as Latex Examples i-
15, using the following monomer mixture:
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TABLE VIII
Styrene 26.8 parts by weight
2-ethyl hexyl acrylate 40 parts by weight
methyl methacrylate 20 parts by weight
methacrylic acid 6.8 parts by weight
sodium styrene sulfonate 1.7 parts by weight
Sodium alkyl(C,o-,2) allyl 1.7 parts by weight
sulfosuccinate
y methacryloxy propyl 3.0 parts by weight
trimethoxysilane
Latex Example 16 had an MFFT of 15°C. The formulation of Latex
Example
No. 17 can be adjusted (Example No. 17) by substituting 5 parts by weight of
methyl
s methacrylate for an equal amount of the 2-ethyl hexyl acrylate. In this
manner, the MFFT
can be further increased to-32°C. By substituting another 5 parts by
weight of methyl
methacrylate for an equal amount of the 2-ethyl hexyl acrylate, the MFFT can
be increased
to 60°C (Example 18) and by substituting yet another 5 parts by weight
of methyl
methacrylate for an equal amount of the 2-ethyl hexyl acrylate, the MFFT can
be increased
io to 80°C (Example 19).
Coatings were prepared from blends of Latex Examples 17 and 18 with Latex
Example 1. The same coating formulation was used as described with respect to
Examples
1-15, except that a 1:1 (by weight) blend of c
15 TABLE IX
Latex Blend Coalescent Hardness Hardness Hardness
Ratio Level Condition Condition Condition
1 100/0 0 1 15/19/20 3
15 14/18/20
1 /17 70/30 5.5 16 15/25/29 13/18/21
1 /18 40/60 7.4 34 27/51 /73 26/55/73
1 /18 50/50 7.4 27 25/48/61 21 /50/64
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Examples 20 to 22
Example 20 was prepared by charging a stainless reaction vessel with 49
parts of deionized water, 0.17 part of sodium alkyl(C,o-,2} allyl
sulfosuccinate, 0.92 part of
itaconic acid and 0.09 part of sodium hydroxide (10 percent), followed by
heating to 82°C.
s Then, a stream containing 0.12 part of sodium alkyl(C,o-,2) allyl
sulfosuccinate in 2.6 parts
water and a second stream containing 2.3 parts styrene, 0.15 part MPTS, 2.1
parts butyl
acrylate and 0.33 part 2-HEMA were added over 20 minutes. A second stream of
0.18 part
of potassium persulfate dissolved in 7.5 parts of water was started 15 minutes
after the start
of the monomers and was fed to the reactor over 30 minutes, to form in situ
seed particles.
io After this initial seeding step monomer streams containing 44.56 parts
styrene, 38.9 parts
butyl acrylate, 6.17 parts HEMA, 1.43 parts sodium alkyl(C,o-,2) allyl
sulfosuccinate and 2.85
parts MPTS and a stream containing 0.18 part of initiator in 7.5 parts of
water were added
continuously to the reactor over 200 minutes. To assure good conversion, an
additional 0.2
part of potassium persulfate in 5 parts of water were added over a 30 minute
period after the
z5 end of the monomer addition. The reaction temperature was then held at
82°C for an
additional 90 minutes to complete polymerization.
Example 21 was prepared in essentially the same manner, except that the
styrene level was decreased by 1 weight percent and the MPTS level was
increased by the
same amount.
z o Example 22 was prepared in essentially the same manner as Example 20
except no MPTS was added to the reactor during the initial seeding step.
Instead, all the
MPTS was added to the reactor over 60 minutes as a separate stream after the
seeding
step.
The resulting latex Examples 20 to 22 were evaluated for hot-blocking
z5 resistance, water and ethanol spotting resistance and MFFT in the same
manner as
Examples 1 to 9 and 11 to 15. All are rated "+" in both water and ethanol
spotting
resistance, and all had an MFFT of 24°C. Example 20 scored a "4" on the
hot-blocking
resistance test, whereas Example 21 scores a "4 to 5" and Example 22 scores a
"5".
Exam~ole 23
3 o Example 23 was prepared by charging a stainless reaction vessel with 85
parts of deionized water, 2.24 parts of a polystyrene seed latex following by
heating to 80°C.
Then, 0.32 part ammonium persulfate dissolved in 45 parts deionized water are
added
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t ~_. ____.r____._._. _~._..__. _ ~ .r. _..._._.. _._ _
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continuously to the reactor over 300 minutes. A monomer stream containing 36.4
parts of 2-
ethyl hexyl acrylate, 26.0 parts methyl methacrylate, 1.43 parts methacrylic
acid and 1.17
parts acrylic acid was added over 156 minutes. Then from 156 to 240 minutes a
stream of
27.4 parts of methyl methacrylate, 4.7 parts of 2-ethylhexyl acrylate, 1.5
parts MPTS, 0.77
s part methacrylic acid and 0.63 part acrylic acid was added to the reactor.
Example 23 was evaluated in a clear coat formulation of the following
composition:
TABLE X
Latex (42.9% solids) 73.4 parts by weight
Water 13.6 parts by weight
Dehydran 1293a 0.5 parts by weight
Surfynol 104Ea 0.5 parts by weight
Byk 346a 0.5 parts by weight
Ammonia (25% aq. Sol.) 0.5 parts by weight
Acrysol RM8a (10% active) 1.7 parts by weight
Syloid ED 50a 2.5 parts by weight
Aquacer 531f
2.0 parts by weight
Butylglycol:Methoxybutanol
2:1
5.0
parts
by
weight
1
o
eSee
notes
e~e
from
Tabie
III.
'A
wax
additive
commercially
available
from
Byk
Chemie.
The coating was evaluated for blocking by condition 1 A/1 B as described
above in section C1 Example i . The samples for evaluating water and
ethanol/water
is resistance were prepared by applying a 150 p,m wet film onto wood and
drying for 2 days at
room temperature. The samples were evaluated by applying to each of them a
filter paper
soaked in a 50/50 ethanol/water mixture. The filter paper was removed from
various
samples after 30 minutes, 1 hour and 5 hours. The films were then visually
inspected. The
sample exposed to the filter paper for 5 hours was inspected 24 hours after
the filter paper
2 o was removed.
The films were tested for water-spotting resistance in the same manner,
except that all films were inspected immediately after removal of the filter
paper.
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The results of the ethanol/water spotting and water spotting tests were rated
on a scale from 0 to 5, with 5 being best.
Coating Blocking Water Ethanol/ Water
Example No. Condition Resistance
1 A/1 B
23 3-4/5 4-5/3/4 4-5/4-5/4-5
s Examples 24 to 28
These latex Examples 24-28 were prepared according to the procedure given
for Example 1. The composition is given in Table XI.
TABLE XI
Example Styrene EHA6 MAA' COMONOME AASSB MPTS9
No. R
24 35.5 50.0 6.8 3.0 H EA' 1.7 3.0
25 35.5 50.0 6.8 3.0 GMAZ 1.7 2.0
26 36.8 50.0 6.8 1.7 AAEM3 1.7 1.7
27 36.8 50.0 6.8 1.7 SEM 1.7 0.75
28 ~ 36.8 ~ 50.0 6.8 1.7 AMPSS 1.7 2.25
~ ~ ~
so ' 2-hydroxyethyl acrylate;
2 glycidyl methacrylate;
3 aceto acetoxy ethyl methacrylate;
sulfoethyl methacrylate- sodium salt
2-acrylamido-2-methylpropane sulfonic acid sodium salt
1s s See notes 2, 3, 5 and 6 from Table I.
The resulting latexes were evaluated in essentially the same formulation as
Example 23 except that only 2 parts by weight of the
methylglycol:methoxybutanol mixture
were used. The latexes were evaluated for blocking, water resistance and
ethanol
a o resistance using the same methods used for evaluating Example 23. The
results are as
reported in Table XII.
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TABLE XII
Example Blocking Water Spot Ethanol Spot
No.
24 2/4-5 4/4/3-4 3/3/2
25 1 / 4 4-5/4/3 3/3/3
26 2-3/5 3/5/3-4 4/4/4
27 3-4/5 3/3/3 3-4/3-4/3
28 3-4/5 4-5/4-5/4-5 3/3/3
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