Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
107673f~
This invention relates to a vehicle composition, and parti-
cularly to a vehicle composition containing particulate solids. More
particularly, it relates to a one-package zinc-filled vehicle composi-
tion which, when applied to a me~allic surface, will impart galvanic
protection thereto.
Zinc-filled protective coatings have been used to protect
metal surfaces, particularly ferrous surfaces, against corrosion. For
example, ~nited States Patent No. 3,056,684 issued Oct. 2, 1962
to Lopata discloses a zinc-filled coating which utilizes a partially
hydrolyzed tetraethyl orthosilicate as a vehicle. Another approach to
preparing zinc-filled protective coatings is disclosed in United States
Patent No. 3,730,743 issued May 1, 1973 to McLeod, in which
zinc dust is incorporated in a vehicle composition obtained from the
hydrolysis and condensation of an alkyl polysilicate. When these
vehicles are mixed with zinc and applied to a surface, the resultant
coating sets up or dries in a matter of a few hours. However, if the
zinc is added to the vehicle at the time of packaging, the reactivity of
the zinc with the vehicle causes gelation within a matter of hours,
resulting in an unacceptable short "shelf life".
Many of the single package zinc-filled protective coatings
prepared heretofore have a secondary problem with gas evolution. In such
formulations, a gas, apparently hydrogen, is generated in the container
when stored at room temperature for periods exceeding two months. One
approach to the problem of gas evolution in a one-package zinc-filled
coating is to package the material in a container having a pressure
release valve which will permit hydrogen to escape. However, such
deviation from standard packaging procedures is undesirable, requiring
specialized containers and complicates the manufacturing procedure. ~Sore-
over, such an approach involves a safety hazard since evaporating
flammable solvents also may escape tllrough the pressure release valve.
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107~;73~
Other zinc-rich coating compositions which contain a substan-
tially non-aqueous colloidal silica suspended in an organic solvent,
zinc chloride and zinc dust have been described in United States Patent
No. 3,615,730 issued October 26, 1971 to Law. It has been found that
these coatings have certain disadvantages, e.g., they are stable only for
periods up to one month.
Thus, it has been virtually impossible to prepare the single
package zinc-filled silicate coating compositions described above which
are stable up to several months and which produce coatings equal to the
coating qualities of this invention.
Therefore, it is an object of one broad aspect of this inven-
tion to prepare a vehicle composition.
An object of another aspect of this invention is to provide a
single package coating composition containing cathodically active metals.
An object of yet another aspect of this invention is to provide
a single package zinc-filled coating composition for ferrous substrates.
An object of still another aspect of this invention is to pro-
vide a single package zinc-filled coating composition which is substan-
tially free of hydrogen evolution.
An object of a further aspect of this invention is to provide
a single package zinc-filled coating composition which provides a hard
abrasion resistant coating on a ferrous substrate in from 1 to 24 hours
and has a "shelf life" of at least 4 months.
It has now been found that a superior single package protective
coating can be prepared from a vehicle containing an alkyl polysilicate
which has been hydrolyzed to a level of from 50 to 65 percent, zinc
chloride and an organic solvent. The resultant vehicle is combined with
a cathodically active metal and, if desired, fillers, and applied to
ferrous substrates to form a protective coating thereon.
Thus, by one broad aspect of this invention a vehicle for a
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single package coating composition is provided, consisting essentially
of: a hydrolyzed alkyl polysilicate having a hydrolysis level of from
50 to 65 percent; an organic solvent; and from 3 to 5.5 percent by
weight of zinc chloride based on the total weight of the hydrolysate;
the hydrolysate being obtained by hydrolyzing the alkyl polysilicate
containing 40 percent SiO2 in the presence of an organic solvent, and
water in an amount of from 0.08 to 0.21 mole per mole of alkoxy present
on the alkyl polysilicate at a pH of from 1.0 to 6.5.
By one variant, the alkyl polysilicate is ethyl silicate "40".
By another aspect, the coating composition also contains
particulate solids.
By a variant thereof, the solids are cathodically active metals.
By another variant, the particulate solids also include a
filler.
By yet another variant, the cathodically active metal is æinc.
By a further variant, the vehicle to particulate solids are in
a ratio of from 10:90 to 70:30.
By another aspect of this invention, a process is provided for
preparing a single package coating composition, which process comprises:
mixing particulate solids with a vehicle and after agitating for at least
0.5 hour in an inert atmosphere packaging the composition, the vehicle
consisting essentially of a hydrolyzed alkyl polysilicate having a hydro-
lysis level of from 50 to 65 percent and zinc chloride in an amount of
from 3 to 5.5 percent by weight based on the total weight of the hydroly-
sate, the hydrolysate being obtained by hydrolyæing the alkyl polysili-
cate containing 40 percent SiO2 with from 0.08 to 0.21 mole of water per
mole of alkoxy present on the alkyl polysilicate at a pH of from 1.0 to
6.5 in the presence of an organic solvent to form the hydrolysate.
By a variant, the particulate solids are cathodically active
metals, e.g., zinc.
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10~7673~1
sy another variant, the vehicle to particulate solids is in a
ratio of from 10:90 to 70:30.
By yet another varlant, the vehicle to cathodically active
metal is in a ratio of from 10:90 to 50:50.
The aLkyl polysilicate useful in aspects of this invention is
an alkyl polysilicate,preferably ethyl polysilicate, which is a mixture
of ethyl polysilicates having 40 percent availabe silica and contains an
average of 5 silicon atoms per molecule. It may be derived from the
controlled hydrolysis of tetraethyl silicate. The formula for the ethyl
polysilicate may be represented as follows:
~OC2H5
C2H50-Si-OC2H5
loc2H5 i 2 5 1 1 2 5
C2H50 - Si - O - Si - O - Si - O - Si - OC2H5
C2H5 OC2H5 C2 5 C2H5
;~ [Additional information for preparing the partial hydrolysis
products of the monomeric organosilicon compounds described above may be
found in the article by H.D. Hogan and C.A. Setterstrom entitled "Ethyl
Silicates" in Industrial and Engineering Chemistry, Volume 39, page 1364,
No. 11 (1947)].
The vehicle composition is generally prepared by mixing the
ethyl polysilicate with sufficient water and acid catalyst to hydrolyze
the ethyl polysilicate to a level of from 50 to 65 percent in the
presence of an organic solvent having a boiling range of from 80C. up to
250C. It has been found that the level of hydrolysis is critlcal in
order to provide a one package coating composition having the desired
hardness, "shelf life" and "pot life". If the hydrolysis level of the
alkyl polysilicate is below 50 percent, the pencil hardness of the resul-
tant coating after one hour is less than 4B and after 24 hours the pencil
hardness is F. When the hydrolysis level of the alkyl polysilicate
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1~7673~
exceeds 65 percent, the pencil hardness of the resultant coating after
one hour is 3B and after 24 hours 6H; however, the "pot life" of the
coating composition is only 2 days and the shelf life is only 10 days.
The term 'hydrolysis level" or "degree of hydrolysis" refers
to the amount of water that is necessary to hydrolyze from 50 to 65 ~:
percent of the alkoxy groups linkea to the silicon atoms, calculated on
the basis of tetraethyl orthosilicate. Thus, when an alkyl polysilicate
is employed, the amount of water necessary to provide a hydrolysis level
of from 50 to 65 percent ranges from 0.08 to 0.21 mole of water per mole
of alkoxy on the alkyl polysilicate.
Although it is not essential it is preferred that a solvent be
employed in the preparation of the vehicle composition of an aspect of
this invention. Examples of preferred solvents are the higher boiling
ethers, e.g., monoalkylene glycol monoalkyl ethers, dialkylene glycol
monoalkyl ethers, dialkylene glycol dialkyl ethers and the monoalkylene
glycol dialkyl ethers. Others which may be employed are ketones, e.g.,
acetone; alcohols, e.g., ethanol, isopropanol, butanol, hexanol, diace-
tone alcohol; glycols, e.g., ethylene glycol and polyalkylene glycols;
hydrocarbon solvents, e.g., hexane, heptane, benzene, toluene, xylene;
chlorinated hydrocarbon solvents and mixtures thereof. The drying time,
viscosity and so forth may be adjusted by proper choice of solvents or
mixtures thereof.
The solvent to alkyl polysilicate ratio is subject to wide
variation depending on the characteristics desired in the finished binder.
Thus, the ratio may lie anywhere within the limits of from 0.5:1 to 10:1.
Although the amount of acid necessary for the hydrolysis of the
alkylPlYsilicate is not critical, it is preferred that sufficient
acid be present to provide a pH of from 1.0 to 6.5 and more preferably
from 1.4 to 5.5. Suitable inorganic acids which may be employed are
hydrochloric acid, sulfuric and hydrofluoric acid. These acids may be
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107673~
used either alone or in combination.
Also, monobasic and dibasic organic acids may be used as well
as metal chlorides, nitrates, sulfates, and metal salts of carboxylic
acids where the metal i9 a member selected from Groups II, III and IV
of the Periodic Table. Examples of suitable organic acids are acetic
acid~ butyric acid, caproic acid, capric acid, palmitic acid, oleic acid,
oxalic acid, fumaric acid, crotonic acid, acrylic acid, maleic acid,
malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid,
and sebacic acid. Other organic acids which may be used are benzoic acid,
toluene sulfonic acid, alkyl phosphoric acids in which the alkyl groups
contain from 1 to 4 carbon atoms and halogenated carboxylic acids.
The techniques for preparing the vehicle compositions are known
in the art; however, it is preferred that the above polysilicate be
dissolved in an organic solvent and thereafter sufficient water, prefer-
ably an acidized water, is added to provide a hydrolysis range of from
50 to 65 percent. The hydrolysis temperature is not critical and may
range from 25C. up to 80C. and more preferably from 30 to 50C.
The vehicle composition is prepared by adding zinc chloride to
the hydrolysate in an amount of from 3 to 5.5 percent and more preferably
from 3.5 to 5 percent by weight based on the total weight of the hydroly-
sate (hydrolyzed silicate and organic solvent).
A coating composition may be prepared by mixing the vehicle
composition described above with finely divided particulate solids, e.g.,
cathodically active metals, e.g., zinc dust and, if desired, fillers and
thereafter agitated in the presence of an inert atmosphere for at least
0.5 hour. The coating composition is applied to metal substrates to
impart galvanic protection thereto. Other cathodically active metals
which may be employed are aluminum and magnesium. Fillers or extenders
which may be employed in these coatings are metal oxides, e.g., lead
- 30 oxide, iron oxide, alumina, titanium dioxide, di-iron phosphide and the
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like. Frequently, it is desirable to employ in lieu of the pure metal
dust, a mixture of metal dust and a suitable filler, e.g., calcium and
magnesium meta-silicate or minerals containing the same. Other fillers,
particularly fibrous mineral fillers, e.g., asbestos, silica, refined
clays, fibrous talc, fibrous calcium meta-silica.e, gypsum and the like
mays also be incorporated with the metal dust, e.g., zinc dust in these
coating compositions. Additional materials which may be included in the
coating compositions are pigments, e.g., zinc chromate, cadmium sulfide,
and most of the lithopones.
The ratio of vehicle to particulate solids is largely a matter
of customer preference or of the specifications to be met. Generally,
the ratio of vehicle to particulate solids, i.e., a cathodically active
metal and filler, is within the range of from 70:30 to 10:90 on a weight
basis. However, where a filler is not included in the composition, e.g.,-
the previously mentioned calcium and magnesium meta-silicates, then the
ratio of vehicle to cathodically active metal is preferably from 10:90
to 50:50 on a weight basis.
Generally, these coatings can be cured at ambient temperature
in from 1 to 24 hours; however, if desired, the coatings may be heat
cured at temperatures ranging from 40C. to as high as 500C. Obviously,
at these elevated temperatures, the cure time will be substantially
reduced.
The preferred coatings conforming to aspects of the present
invention have a flash point from 80F. to 150F. (tag open cup method)
and a pot life meeting the requirements of substantially any field of use.
Oftentimes it is desirable to add additional organic solvent
to these coating compositions to form thin film coatings on metal sub-
strates. These dilute compositions are particularly suitable as "shop
primers", i.e., they are especially adaptable for use as preconstruction
primers to provide protection for steel plates prior to their incorpora-
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tLon into a structure, e.g., a ship. The finished structure may then be
coated with the more concentrated coating composition of aspects of this
invention.
These coating compositions may be applied to a cleaned metal
substrate by painting, spraying or other conventional techniques known
in the art. They display excellent adhesion on application and in some
cases, may be applied successfully to clean, steel surfaces without prior
sandblasting. Good adherence to damp galvanized surfaces has been
achieved. These coating compositions will not freeze nor are the coatings
adversely affected by bright sunlight at tropical temperatures. The
coatings show very good resistance to salt spray, fuels and organic sol-
vents. These coatings may be easily pigmented, hence they can be
employed without any overcoat.
The coating compositions of aspects of this invention have very
unique properties, i.e., they can be formulated into a single package
system, stored for periods of at least 6 months without gel formation
and are substantially free of gas formation.
The invention is further illustrated by the following examples
in which all parts are by weight unless otherwise specified.
EXAMPLE 1
(a) A hydrolysate i5 prepared by slowing adding with agitation
22.5 parts of deionized water to a reactor containing 1000 parts of
ethyl silicate "40", 1177 parts of ethylene glycol monoethyl ether and
3 parts of zinc chloride and thereafter the reaction mixture is agitated
for 2 hours at a temperature up to 60C.
To 1000 parts of the hydrolysate prepared above are added 40
parts of zinc chloride and the mixture is heated for 2 hours at 45C. with
agitation to form a vehicle composition.
(b) A coating composition is then prepared by mixing 241 parts
of the vehicle composition prepared above with 21 parts of siliceo~us
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107673~
materials known by the Trade ~arks CELITE 499 and 3 parts of BENTONE 27,
and 735 parts of zinc dust (2 to 7 microns) with agitation in an inert
atmosphere for 0.5 hour and thereafter applied to a light sandblasted
steel substrate. After drying at a 50 percent relative humidity at 77F.,
the coating is tested after l hour and again after 24 hours for hardness
in accordance with the standard hardness test. In this test, a pencil
lead is employed having varying degrees of hardness corresponding to the
scale 6B, 4B, 3B, F, H, 2H, 3H, 4H, 5H, etc. These values represent a
progressive increase in hardness. The pencil lead is held at a 45 angle
relative to the zinc coating as laid down on the steel panel and
moderate force is applied until the coating is removed. The properties,
e.g., hardness, "shelf life" and "pot life" are illustrated in the
following Table. The "shelf life" and "pot life" was determined at 25C.
EXAMPLE 2
(a) The procedure described in Example l(a) is repeated except
that 48 parts of water are added to a reactor containing 1115 parts of
ethylene glycol monoethyl ether, 1000 parts of ethyl silicate "40" and 3
parts of zinc chloride. To 1000 parts of the hydrolysate thus formed are
added 40 parts zinc chloride and the mixture is heated for 2 hours at 45C.
to form a vehicle
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composition.
¦ ~b) A coating composition is prepared in accordance with
Example l(b) except that the vehicle composition prepared in ' I
Example 2(a) is substituted for the vehicle prepared in Example l(a),.
The composition is applied to a steel panel and the hardness value 1,
s determined after drying for 1 hour and again after 24 hours at
50 percent relative humidity at a temperature of 77F. The proper-
¦ties are illustrated in the following Table.
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~ EXAMPLE 3
'I ' (a) The procedure described in Example l(a) is repeated
except that 60 parts of water are added to a reactor containing
1140 p'arts of ethylene glycol monoethyl ether, 1000 parts of ethyl j I
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' j,silicate "40" and 3 parts of zinc chloride. ¦
~l A vehicle composition is prepared by adding about 40 parts',
¦lof zinc'chloride to about 1000 parts of'the hydrolysate prepared
above.
('b) A coating composition is prepared in accordance with
, I Example l(b) except that the vehicle composition prepared in
Example 3(a) is substituted for the veh~cle prepared in Example l(a),.
I The composition is applied to a s'teel panel and the hardness value
- ~lls determined after drying for 1 hour and again after 24 hours at
!i50 percent relative humidity at a temperature of 77F. The proper-
,, , ¦ ties are illustrated in the following Table.
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I ' EXAMPLE 4 - 25 ll (a) The procedure described in Example l~a) is repeated
e-xcept that 72 parts- of water are added to a reactor containing
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!¦ 1076734 . I
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¦~1128 parts of ethylene glycol monoethyl ether, 1000 parts of ethyl
;silicate "40" and 3 parts of zinc chloride.
The resultant hydrolysate is.then mixed with zinc chloride~
¦ln a ratio of 40 parts zinc chloride for each 1000 parts of the
¦~hydro1ysate to form a vehicle composition. I
¦ (b) A coating composition is prepared in accordance with
iExample l(b) except that the vehicle composition prepared in
¦jExample 4(a) is substituted for the vehicle of Example l(a). The
~coating is applied to a steel panel and the hardness value is
lldetermined after drying for 1 hour and again after 24 hours at 50
¦percent relative humidity at a temperature of 77F. The properties -
of the coating composition are illustrated in the following Table.
EXAMPLE 5 ~ ¦
!l (a) The procedure described in Example l(a) is repeated
~ 15 liexcept that 96 parts of water are added to a reactor containing
j ¦i1096 parts of ethylene glycol monoethyl ether, 1000 parts of ethyl
t Ijsili cate ~40 and 3 parts zinc chloride to form a hydrolysate.
The resultant hydrolysate is then mixed with zinc chlo-
ride in a ratio of 40 parts zinc chloride for each 1000 parts of
Ijthe hydrolysate to form a vehicle composition. I
! (b) A coating composition is prepared in accordance with
jExample l(b) except that the vehicle composition prepared in
ilExample 5(a) is substituted for the vehicle of Example l(a). The
¦Icoating is applied to a steel panel and the hardness value
I!determined after drying for 1 hour and again after 24 hours at 50
,percent relative humidity at a temperature of 77F. The properties
are illustrated in the following Table.
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107673~
¦ EXAMPLE 6
(a) For purposes of comparison, a composition is pre- ¦
¦pared in accordance with the procedure described in Example l(a)
~in which 1000 parts of ethyl silicate "40" is mixed w~th 1200 parts
S ~of ethylene glycol monoethyl ether and 3 parts of zinc chloride. I
: The resultant composition is then mixed with zinc chloride'
in a ratio of 40 parts zinc chloride for each 1000 parts of the
omposition to form a vehicle.
I ~b) A coating is prepared ~n accordance with Example l(b)'
~lexcept that the vehicle composition prepared in Example 6(a) is
substituted for the vehicle of Example i(a). The composition is
iapplied to a steel panel and the hardness value determined after
¦Idrying for 1 hour and again after 24 hours at S0 percent relative
~Ihum~dity at a temperature of 77F. The properties are illustrated
! lS lin the following Table.
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EXAMPLE 7
¦l (a) For purposes of comparison, a vehicle composition is
~prepared in accordance with the procedure described in Example l(a)
¦lexcept that the 40 parts of zinc chloride is omitted.
¦! (b) A coating composition is then prepared in accordance
¦Iwith Example l(b) except that the vehicle composition prepared in
¦¦Example 7(a) is substituted for the vehicle of Example l(a). The
¦composition is applied to a steel substrate and the properties deter'-
¦mined in accordance with Example ltb). The properties are
lillustrated in the following Table.
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107~73~ ~
, EXAMPLE 8
I
l ~a) For purposes of comparison, 20 parts of zinc chloride
¦ s mixed with the hydrolysate prepared in accordance with the
~rocedure described in Example l(a). ~
. 5 1¦ (b) The resultant vehicle composition is then mixed with
~inc dust in accordance with Example l(b) except that the vehicle
composition prepared in Example 8(a) is substituted for the vehicle
pf Example l(b). The composition is applied to a steel substrate.
The properties of the coating composition are shown in the following
lable.
l I EXAMPLE 9
I l~ (a) A hydrolysate is prepared by mixing 1000 parts of
~ thyl silicate "40" with 1220 parts of ethylene glycol monoéthyl
¦ !lether, 44 parts of water and 3 parts of zinc chloride in accordance !
¦~with the procedure described in Example l(a). To about 1000 parts
of the hidrolysate prepared above are added 124 parts of zinc
¦chloride and the mixture is heated to 45C. for 2 hours with
agitation to form a vehicle composition.
(b) A coating composition is prepared by adding 735 parts
iof zinc dust (2 to 7 microns), 25 parts of "Celite 499" and 3 parts
¦of "Bentone 27" to about 241 parts of the vehicle composition
¦prepared in 9(a) above and agitated for 0.5 hour in an inert atmos-
phere. The properties of the resulting coating are illustrated in
~- ¦Ithe following Table.
1~ EXAMPLE 10
l~ (a) For purposes of comparison, a hydrolysate is prepared
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107f~73~
by mi~ing L500 parts of tetraethyl orthosilicate with 655 parts of
ethylene glycol monoethyl ether, 154 parts of water and 3 parts zinc
chloride in accordance with the procedure described in Example l(a~. To
1000 parts of the hydrolysate composition are added 40 parts of zinc
chloride and the mi~ture is heated to 45C. for 2 hours with agitation
to form a vehicle composition.
(b) A coating composition is prepared by adding 21 parts of
CELITE 499, 3 parts of BENTONE 27 and 735 parts of zinc dust (2 to 7
microns) to 241 parts of the vehicle composition prepared in 10(a) above
and agitated for 0.5 hour in an inert atmosphere. The properties of
the resulting coating are illustrated in the following Table.
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1076734
It will be observed from the Table that coating compositions
containing zinc chloride and ethyl polysilicate which have been hydrolyzed
to a level of from 50 to 65 percent have a "shelf life" greater than 3
months, whereas similar coating compositions in which the ethyl poly-
silicate is hydrolyzed to a level of at least 70 percent, have a "shelf
life" of only lO days or less. ~Ioreover, the Table shows that when zinc
chloride is omitted from a coating composition containing ethyl polysili-
cate hydrolyzed to a level of 50 percent, the hardness after 1 hour and
: again after 24 hours was unacceptable. Also, it can be observed that
10 when tetraethyl orthosilicate is substituted for ethyl polysilicate and
hydrolyzed to the same degree, the hardness value of the resulting
coating after 1 hour is unsatisfactory and after 24 hours is inferior to
the coa~lngs of aspscts of th~s lnvsntlon.
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