Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF TH~ INVENTION
This invention relates primarily to a water based
protective coating composition which is most particularly use-
ful for undercoating of vehicles to prevent corrosion. As
explained later herein, the composition may if desired, be
modified to provide a solvent base system; however, it is most
preferred that the composition be aqueous in order to eliminate
some inherent problems in solvent based systems such as odor,
potential flame hazards, and the like.
Generally in the metal coating industry, and parti-
cularly in the automobile undercoating industry, there is acontinuing need for coatings which provide good corrosion
resistance. ~n effective undercoating for metal substrates,
particularly automobiles, should be one which upon drying
; provides a goodl strong, tough film. ~dditionally, the film
should have a high solids content which not only enhances
corrosion resistance but also allows the film to provide some
sound, or noise, insulation. Then too, a satisfactory film
should be one which has ~ood adherence properties to the under-
lying substrate. Finally, a good undercoating composition
should be one which is not only effecti~e but economical to
manufacture and one which is easy for a user to apply. With
regard to ease of application, one problem which often occurs
in spraying of undercoating compositions is that they will
; have a tendency to "overspray". Ideally~ a good composition
will have a narrow but effective spray pattern.
A primary object of this invention is to provide
a butadiene styrene latex coating composition, particularly
an aqueous composition, which achieves each of the above
desirable attributesu
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Another object of this invention is to provide a
butadiene styrene late~ coating composition using mica as a
filling and flattening agent, and also employing a newly found
advantage that if mica is employed as a filling and flattening
agent, it also stabilizes the composition to prevent premature
gelling.
A further object of this invention is to provide a
product of enhanced anti foaming properties. That is to say~
foaming is undesirable and providing that ammonium hydroxide
is used as a pH control agent to provide a pH within the range
of 7.5 to 10.0, for reasons that are unknown, the ammonium
hydroxide enhances the effectiveness of the defoaming a~ents
employed.
Yet another object of this invention is to provide
a method of manuacture of a latex, butadiene styrene car
undercoating system.
An even further object of this invention is to
provide a hiyh solids content coating, even as high as 45-50%,
; for a solvent based butadiene styrene polymer system.
Yet another object of the invention is to provide
a coating composition which upon drying provides a barrier to
moisture which is effective because of overlapping platelets
of mica.
The method and means of accomplishing these
objectives, and others, will become apparent from the detailed
description of the invention which follows.
DETAILED DESCRIPTION OF THE INVENTION
_
The emulsion system, or film former of this invent-
ion, is a polymer substance made by emulsion polymerization of
a co-po]ymer of styrene and 1,3 butadiene. Butadiene styrene
copolymers, of course, are generally known. Those satisfactory
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for use herein have a butadiene:styrene ratio between about
30:70 and about 95:5, pxeferably between about 60:40 and 80:20
with an optimum ratio being in the range of 70:30 to 75:25.
One particularly satisfactory latex is sold by the B.F.
Goodrich Company Chemical Division under the trade mark Good-
Rite Latex No. 1800-X-73. This latex contains approximately
45% solids. It, of course, goes without saying that other
butadiene styrene latex emulsion systems are available and
may be used herein~
While butadiene styrene latex emulsion systems
ha~e in the past been used for coating compositions, to the
knowledge of the applicants, they have not heretofore been
used as car wndercoating compositions~ Primarily, they have
been used in conventional paint compositions and for uses such
as carpet backing. In the recent past, -they have not been
used signi~icantly in paints because of their tendency to
oxidize in the presence of ultraviolet light. Upon oxidation
their coating effecti~eness is decreased.
In accordance with applicants' invention, it has
been discovered that ef~ecti~e butadiene styrene emulsion
systems can be used ~or car undercoating, providing that the
system is formulated in accordance with the hereinafter des-
cribed techniqu~s. In particular, i~ the composition employs
mica as a ~iller and 1attening agent, the composition has
improved corrosion resistance in that it is impermeable to
moisture transmission and in addition, the mica also seems to
stabilize against premature gelling during the manufacturing
of the composition by substantially increasing the mechanical
stability o the composition.
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As heretofore explained, the primary latex emulsion
or polymer of this system is a butadiene styrene system of the
type previously described. The butadiene styrene emulsion
typically may comprise from about 40% to about 65% by wei~ht of
the emulsion systemO It is conceivable that an even broader
range, for example, from 10% to about 70% may be employed; how-
ever, for the compositions of this invention, it is highly
preferred that the amount be wi~hin the range of 40% to 65% by
weight of styrene butadiene emulsion.
Turning now to the aqueous amulsion system which
employs mica as the filler and ~lattening agent. Mica can be
defined as any of several silicates of varying chemical com-
position, but all haviny similar physical properties and crystal
structure. The uniqueness of mica is its characteristic crystal
structure which allows it to cleave into thin sheets which are
flexible and elastic. Thus, mica differs from other silicates
primarily by crystaline structure in that even after bein~
~round, it still is in the form of thin platelets. ~n the com-
position of the present inveIltion, the amount of mica which ma~
be employed can be from about 5% to about 20% by weight of the
composition, preferably from about 8~ to about 15% by weight
of the composition.
In the compositions of the present invention,
primarily the aqueous butadiene styrene emulsion system, the
mica performs several important functions from the standpoint
; of enhancing the corrosion resistance, when compared to other
butadiene styrene emulsion systems not using mica. First,
after coating of a metal substrate, when the water evaporates
and the latex emulsion coalesces, the individual particles of
mica are drawn closer togeth~r and themselves form an over-
lapping structure to provide a substantially moisture
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impervious barrier. Thls moisture impervious barrier effect-
ively prevents water vapor transmission to the underlying metal
substrate. This cannot be achieved with other filling and
flattening agents which do not exhibit a platelike crystaline
structure, since they will not form and overlap upon setting
of the emulsion, as will mica. Secondly, for reasons which
are unknown, the mica seems to prevent premature gelling of
the system during mixing. This is a problem which often occurs,
but for reasons unknown to the applicants, seems not to occur
when mica is employed. Thus~ the mica can be ~hou~ht of as
enhancing the processability of this system from the stand
point of preventing premature gelling during mixing.
Mica, of course, can be obtained fram a variety of
sources. One which has been used satisfactorily herein is 325
mesh water ground mica produced by English Mica. Another
which is satisfactory is 325 mesh water ground mica produced
by Smithko. Satisfactory and preferred mica can be obtained
from Thompson, Weinman and Company, with offices at Carterville,
~.eorgia. The mica product obtained from them is described in
their product belletin, PB-10. Microscopic examination of
the mica described in the previously referenced bulle~in which
chemically is a combination of hydrated magnesium and aluminum
silicates, reveals that it shows a large proportion of ~he
particles to be "plate-like" in structure. The Thompson,
Weinman and Company mica is the preferred for use in this
invention.
Certain of the minors, hereinafter described, tend
to make the composition acidic which is undesirable from the
standpoint of use and stability. Therefore, a base must be
added. Numerous bases have been tried but it has been found
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that ammonium hydroxide is the most suitable. The amount of
ammonium hydroxide can vary, but it should be a sufficient
amount to provide a pH within -the range of 7.5 to 10.0, pre-
ferably within ~.5 to 9Ø Typically the amount can be from
about .05% to about ~% by wei~ht, assuming 26 Baume ammonium
hydroxide. Of course, if the ammonium hydroxide concentration
varies from that specified herein, the amount of ammonium
hydroxide will vary. But the important factor is a sufficient
amount to provide a pH within the range of 7.5 to 10.0 and for
maximum stability, within the range of 8.5 to 9Ø
Foaming is, of course, undesirable during process-
ing and application, since foaming would cause air voids which
would allow permeability of the coating after drying. There-
fore, defoamers are employed in the compositlon. Surprisingly,
and for reasons not fully understood, the ammonium hydro~ide
enhances the effectiveness of the anti-foaming agents. Other
bases do not seem to pro~ide this ef~ect.
In addition to these major components heretofore
listed, that is, the butadiene s-tyrene latex emulsion, the
mica ~iller and flattening agent, and the base adjusting
component (ammonium hydroxide), the emulsion system is com-
prised of several other conventional ingredients, referred to
herein as minors. These minors, include bacteriostatic agents,
wetting agents, defoaming agents, pigment, and viscosity
modifiers. Each of these will only be described briefly.
Suitable bacteriostatic agents are added, as the
term implies, in order to provide bacterial resistance.
Typically the amount employed may be ~rom .02% by weight to
about .2% by weight of the composition. One which has been
found particularly useful in the aqueous butadiene styrene
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emulsion systems of this invention is Troysan's C~P acetate.
"CMP acetate" is chloromethoxypropyl mercuric acetate and is
a preservative for water bas~d paints available from Troysan
Chemicals, and is described in Bulletin FP-104~ of March 1,
1977. Of course, other bacteriostatic and preservative agents,
other than Troysan CMP Acetate, may also be employed.
Wetting agents to allow and assure that the latex
emulsion system will wet and spread over the metal substrate
are commonly employed at levels ranging from .1% to about 1%
by weight of the composition of this invention. Such are
typically surfactants which facilitate adherence of the paint
to the substrate surface. For example, Aerosol OT 75 avail-
able from Cyanamid is one suitable wetting agent which may be
employed. Others well known to those in paint formulation
business may also be employed.
Deoaming agents are utilized in order to prevent
tha composition from foaming during ~ormulation and also in
order to prevent foaming during application. Such anti-
foaming agents may be employed in the compositions o~ this
invention at levels of from .05% to about 1% by wei~ht, most
typically from about .OB% to about .2% by weight.
Typical defoaming agents are well known in the
paint formulation industry, and therefore a detailed descript-
ion need not be given. However, suitable results have been
~5 achieved when using as a defoaming agents, AF-100, an anti-
foaming agent available from Tenneco Chemicals sold under the
trade mark Nuodex AF-100, which is quoternory ammonium naph-
thenate. Other anti-foaming agents may, of course, also be
used.
Another minor ingredient commonly employed is a
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viscosity control agent, typically at levels of from .5% to
2.0~ by weight and most preferred in this composition at levels
from about 1~ to about 1.5~ by weight. Again, such viscosity
control agents are well known and therefore a detailed descript-
ion need not be given. One which has been found satisfactoryis Acrysol (T.M.~ ASE 60, an aqueous solution of polyacrylate
or other polymeric acrylic salts sold by Rohm and Haas Company.
Of course, pigment is also employed and since the
compositions are used for undercoating most commonly the pig-
ments are black pigments, such as lampblack. The amount mayvary over a fairly wide range, but satisfactory results have
been achieved with from about 1% to about 5% more typically
within the preferred range of about 2% to about 3%. Suitable
pigment can be lampblack No. 866-9907, sold by Tenneco. Other
pigments may be employed, with the precise pigment not being
critical.
: The compositions so far described is an aqueous
latex emulsion system, primarily designed for undercoating
use for vehicles. This system besides the advantages hereto-
fore mentioned, has good stability and shelf life, exhibits
effective coating and sealing as well as good corrosi.on
resistance.
While for some uses solvent based undercoating
systems are perhaps less desirable because of odor and applic-
ation problems, there are times when users prefer such systems~Therefore, in addition to the aqueous system previously des-
cribed herein, applicants have discovered a satisfactory so~-
vent based system which importantly may have a high solids
content~ typically as high as 40~ to 50~. This solvent base
system, like the previously mentioned aqueous base system,
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is one which employs a butadiene styrene polymer. Its ingred-
ients are shown in the table below, including the preferred
specific components.
SOLVENT BASE SYSTEM
TABLE l
Ingredient Proportion
Solvent, Mineral Spirits
Solvesso ~T.~.) 150 (Amsco Division,
Union Oil) - Methanol or the like30% - 50%
Viscosity modifier
(Bentone (T.M.) 34 (National Lead
Pigments and Chemicals Division)0% - 3%
Butadiene Styrene
(Kraton (T.M.~ 1101 Shell) 5% - 40%
Alkylated ~romatic hydrocarbon
(Nevchem (T.M.) 100 ~Neville) 0% - 20%
Filler and Flattening Agent
(Microtalc ~Pfizer) 5% - 15%
Pigment ~Tenneco 866-6607 Lampblack)1% - 5%
While each of the components of the solvent system mentioned
herein are individually known, it is noteworthy that this
system is a successful one which is able to achieve a solids
concentration of as high as 40%-50~, something which has not
heretofore been obtainable. A high solids content is desir-
able in that it improves the impervious nature of the coating
and therefore its effectiveness for corrosion inhi~iting.
The following examples are offered to illustrate
both the method of preparation and use of the undercoating
systems in this invention.
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EXAMPLE 1
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A latex aqueous emulsion system was prepared in
the following manner. The following ingredients were blended
in a high speed disperser under slow agitation.
~ounds
Water, CMP acetate 200
Aerosol (T.M.) OT - 75 0.50
Ammonia 26 Baume 4.00
Defoamer (AF-100) 1.00
Gradually the speed of the high speed disperser was increased
and 100 pounds of mica 325 mesh as perviously described here-
in, was added. Mixing continued until the composition was
completely dispersed and free of lumps. A pH check was made
and the pH was adjusted to within the range of 8.5 to 9.0 with
15 ammonium hydroxide (26 Baume). F:ive hundred and eight (508)
pounds of butadiene styrene emuls:ion sold under the trade
mark Goodrite 1800-X-73 was added and mixing continued at slow
sp0ed .
The following ingredients were premixed:
20 Acrysol (T.M.) ASE 60, 4.4 pounds, and water 17 pounds. This
premix was added to the other ingredients along with 20 pounds
of Aquasperse(T.M.) black paste 877-9910. Thereafter, the
addition tank for the ingredients was washed with 50 pounds
of water and 6.6 pounds of Acrysol ASE 60 which was added to
the mixture. The viscosity was checked and found to be with-
in the range of 68-72 KU. Final viscosity upon checking the
next day showed a viscosity within the range of 70-75 KU.
This total batch comprises 912.5 po~mds. The solids content
was 37.6%.
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This composition was used in a spraying application
for car undercoating. Upon spraying, the composition was noted
to efEiciently and effectively coat the car undersurface. The
composition also exhibited yood stability and shelf life. Upon
examination of the cured film of the composition, it sho~ed
that the mica platelets formed an overlapped structure to pro-
vide an effective substrate barrierr Subsequent checking re-
vealed a substantially moisture impervious barrier. There was
also noted a lack of voids which might be caused by air bubbles
formed from foaming.
If similar compositions are made, utilizing convent-
ional filler and flattening agents such as magnesia silicate or
microtalc, the compositions are noted to be considerably less
stable, and their integrity from the standpoint of moisture
transmission is not nearly as good.
EXAMPLE 2
The following example is offered to illustrate an
example of a usable solvent base system.
Ingredient Amount
Solvesso 150 81.29 pounds
~entone 34 ~gelling ayent) 22 pounds
Methanol 95% 6.67 pounds
Mineral spirits 240 pounds
~utadiene Styrene
~Kraton 1101 ru~ber) 71 pounds
Nevchem 100 165 pounds
Microtalc (magnesium silicate filler) 109 pounds
Pigment (Tenneco 866-6607) 35.20 pounds
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The Solvesso and Bentone were dispersed to a gel and mixing
continued until all lumps disappeared. Thereafter, the methanol
and mineral spirits were added along with the Kraton 1101 and
Nevchem 100. Mixing was continued until all of the polymers
dissolved. Thereafter, while continually under agitation, the
Microtalc was added, as well as the pigment.
This system showed stabilityr ease of manufacturing
and efficiency in terms of spray coating.
The solids content of this system was ~8.9%.
While the coatiny compositions of this inVentiQn
have specifically been referred to as primarily ~or car under-
coating, and application by spray gun, it should also be noted
that other means of application such as brush or roller might
also be employed, although significantly less practical.
It can therefore be seen that applicant has provided
a useful butadiene sytrene a~ueous emulsion system for car under-
coating, and, in addition, has shown a modified system which
employs butadiene styrene in a so:Lvent composition. Moreover,
these compositions are effective coating barriers to moisture
penetration.
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