CA1076734A - Polysilicate vehicle for one package coating compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A vehicle for a single package coating composition is provided herein. It consists 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. The resulting vehicle composition is mixed with a cathodically active metal and, if desired, fillers to form a coating which exhibits a high degree of stability and is highly resistant to corrosion.

Description

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.

: . . ~
:;: .

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 D
~ - 2 -'~ ' ' ::
: ' ' -. , : ~ ' :

10'~t~73~ -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.
,~ 3 :: .

.. . . .
.. . , ; .. . .
:- . . . .

~ .

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 ;~ [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 ~
~

- -: ' ' ' ' ~ , , ' ' ' ' , '. ' ' '' ' ' .

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 .

.. . ~ . .. .
..

. :, . , : : ' 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 ~ ~ - 6 -"
: ' .~ . . : ' ', ~- :
' 107673~
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-_ 7 _ .F~' ' , - ~ : . .': ,, ' .
- .. ' : . . ~ ',~.

:

iO7~:;73~

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.

(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 ' , , .

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.

(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 .

' r~2 ~ _ 9 _ ~-~i ~ .
~., ', ! ~

' ' ' ' . ' , '' ' ' ' ' ~ .
': ~ ' " ' ', ' ~ ' ' ' , ' ' ' ' ~ '' ' :' ' .

S ~ t~

Ii 1 107~;7;~

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.
- li ' ' ' ' . I
~ 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
~ . l ' 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.
,,, , . I . .. I
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 !
- 1 O- .
` I

,. !
i,j I
!¦ 1076734 . I
Il !
¦! . I
¦~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.

i -11-- ~ ~c ' i~

` l l 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.
. I .~ . 1.

¦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.

' !l ..

-l2-_ ~

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 !!
~ 13- l 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.

.

- , - . :

--1 . . . I
., 1()7673 0 o ~
~ _ -- s s s c -- s c _ V ~ ~ ~ ~U~
, _ C_ C C C ~ C C C
_~ o o o ~ ~ o o o o o ~_ ~ o E E E ~ ~I E E E E E
O E ~ ~ ~ O ~ ~ ' ~
--~. ~ ~ ~ . ~ ~ A A
. .
e . ', ,. .' . .
, . . ~ o . . ~ _ c s s s c c c ~ c .
_ ~ ~ ~ ~ ~ ~ Vl ~, ~ ~ ~ ~ .
., . . ___ C C ~ C ~, C C C ~ C .
.~, ~ o o o o ~ o o o o o ~_ O E E E E ~ E E F E E
.- . _--O.
. . _ ~ E ~ ~r ~ ~ O ~ ~t ~ ~ d : ~ /~ ~ ~ ~ A ~\ A ~ `
' ' I ~ ' " ` '- '- ''' ' '. ' - . ~ . _ ~ O O Ir~ ~ N O O O O O
.. ' ! ~ ~ .
, . . j ., o_ . . , . .
,., I .
~ .
I m s -- I I S ~ tl~
- . . ¦ J¦ C N It) ~ J, , -! _-.. . . I .. ., -. . ''-i . ~
' - . . I . "~ o o o o o o -~ o t~ o : j . I 5 ~ . . . . . . . . .~ .
- ! ~ ~ ~ ~ ~ t~ t~ t~ t~
~ ~ ~

~ -' ' I ' . . ~ - ` . . ` . I
I tt . -. I . ~ . ... ,~ .. I
, 0 , o o U. o o o o o 0 ~-l . ~ o a~ ~
"- ! ~ o . . ~U I

~'., . I ~ '' ' '~
. ~ o co co In o~ s '' I
X O _ N C~ ~ O O O . C~
. ~0 ~ . . . ... . . . . .
: ¢ O O O O O O O O O C) O

.
. . _ ., . ~ . . . . . . . . . . . . ~
I ~ -- c'J ~ ~ u~ o r~ ~ cr~ o ~ I
'. j X o _ ~ I

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.

.

~. , .
. 20 ~ ' .` ' .

: , : ' ' '

Claims (12)

The embodiments of the invention in which an exclusive prop-erty or privilege is claimed are defined as follows:

1. A vehicle for a single package coating composition consis-ting 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; said 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 mols per mole of alkoxy present on the alkyl polysilicate at a pH of from 1.0 to 6.5.

2. The vehicle of claim 1 wherein the alkyl polysilicate is ethyl silicate "40".

3. A single package coating composition containing the vehicle of claim 1 and particulate solids.

4. The composition of claim 3 wherein the particulate solids are cathodically active metals.

5. The composition of claim 4 wherein the particulate solids also include a filler.

6. The composition of claim 4 wherein the cathodically active metal is zinc.

7. The composition of claim 5 wherein the vehicle to particu-late solids are in a ratio of from 10:90 to 70:30.

8. A process for preparing a single package coating composi-tion, 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, said vehicle consisting essentially of a hydrolyzed alkyl polysilicate having a hydrolysis 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 hydrolysate, said hydrolysate being obtained by hydrolyzing the alkyl polysilicate 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.

9. The process of claim 8 wherein the particulate solids are cathodically active metals.

10. The process of claim 9 wherein the cathodically active metal is zinc.

11. The process of claim 8 wherein the vehicle to particulate solids is in a ratio of from 10:90 to 70:30.

12. The process of claim 9 wherein the vehicle to cathodically active metal is in a ratio of from 10:90 to 50:50.