Composition process for aqueous base coatings for corrodible metals

Water base latex compositions suitable for coating corrodible metals, such as sand blasted ferrous metal, are prepared by a process characterized by the essential steps of (1) emulsifying under alkaline conditions a film forming oxidatively curable oil or alkyd modified polyurethane, and (2) blending therewith a copolymeric or homopolymeric acrylic or vinyl acetate latex. For metal coatings or for universal coatings for both (bleeding) woods and metal, a single pigment or a combination of pigments with corrosion inhibiting characteristics can be used with the polyurethane-acrylic latex, or polyurethane vinyl latex.

BACKGROUND OF THE INVENTION 
In the case of corrodible metals, such as sand blasted ferrous metals, the 
water as well as certain ingredients often found in latex coatings (such 
as surfactants) corrode the metal beneath the coating to destroy the bond 
and discolor the surface. It is important to develop latex corrosion 
resistant coatings which work in order to meet our ever growing and more 
stringent regulations for chemicals in the envirionment. 
SUMMARY OF THE INVENTION 
To inhibit corrosion on ferrous metal surfaces requires a coating 
containing a resin which will not be corrosive per se and where the resin 
will accept highly reactive pigments. The highly reactive pigments are the 
most desirable from a performance standpoint (the plating of the substrate 
with the release of ions such as the chromate ion) but have not been used 
in latex coatings because the resultant paint was not viscosity stable in 
the container. Now for the first time we have latex coatings containing 
reactive pigments which are stable. The basic polyurethane and a film 
forming interpolymer, such as an acrylic emulsion, can be used with one or 
more of a selection of pigments selected from among barium metaborate, 
barium chromate, lead silica chromate, zinc yellow chromate, strontium 
chromate, zinc oxide, calcium chromate, and calcium borosilicate 
composite. These resin/pigment combinations not only provide corrosion 
control of steel but the same combinations also provide control of the 
tannin bleed in certain woods such as cedar and redwood.

PREFERRED EMBODIMENTS 
Of the following examples, six have to do with the manufacture of the basic 
resin system, the seventh with a formulation for a paint, and the eighth 
through tenth with components and coatings particularly useful for 
corrosive metals. 
EXAMPLE 1 
The first example typifies the production of an intermediate for a 
high-solids oxidatively curable alkyd-modified polyurethane resin 
dissolved in a hydrocarbon solvent. High solids are used for ease and 
efficiency in manufacture and to hold the quantity of solvent within 
limits specified in legislation controlling solvent emissions from applied 
coatings. 
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Soybean oil 1,256 pounds 
Litharge 91 grams 
Pentaerythritol, 
technical grade 146 pounds 
Phthalic anhydride 214 pounds 
Ethylene glycol 56 pounds 
Xylol 334 pounds 
Anti-foam solution* 1/2 fl. oz. 
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*A common anti-foam solution consists of a 2% solution of a silicone resi 
such as Dow-Corning Anti-foam A in a heavy solvent, such as Solvesso 150. 
In a suitable reactor, such as an alkyd reactor, heat the soybean oil while 
sparging with nitrogen at 5 cubic feet per minute (5cfm). Add the 
pentaerythritol at 215.degree. F. and continue the upheat, gaining 
408.degree. F. in 1 hour. At 408.degree. F. add the litharge slurried in a 
small amount of oil. Continue the upheat to 453.degree. F., taking about 1 
hour. At 453.degree. F. add the phthalic anhydride and the anti-foam 
solution. The elapsed time to this point is about 3 hours. Cool to 
400.degree. F. and add the ethylene glycol. After all the ethylene glycol 
has been added, heat to 430.degree. and hold at 430.degree. F. for 
approximately four hours, at which time the acid number will be 
approximately 6 to 7. Cool the batch to 300.degree. F. and add the xylol 
to reduce the nonvolatile content to 84%. Pass the solution through a 
filter press and pump to a steam-jacketed reactor for the next stage, 
typified by Example 3 which illustrates the reaction of the alkyd 
intermediate with toluene diisocyanate. 
EXAMPLE 2 
This example typifies the production of an intermediate for an oxidatively 
curable oil-modified polyurethane. 
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Linseed oil 1,053 pounds 
Litharge 2.5 ounces 
Glycerol 162 pounds 
Mineral spirits 1,200 pounds 
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Heat linseed oil to 440.degree. F. under an inert gas blanket. Add litharge 
and then glycerol. Reheat to 440.degree. F. and hold for completion of the 
alcoholysis reaction, as indicated by solubility of a test portion in two 
volumes of methyl alcohol. Cool and add mineral spirits with stirring. 
Pass through a filter press and pump to a steam-jacketed reactor for use 
in the next stage, typified by Example 4 which illustrates the reactor of 
this type of intermediate with toluene diisocyanate. 
EXAMPLE 3 
Example 3 illustrates the conversion of the alkyd-modified intermediate of 
Example 1 into an alkyd-modified polyurethane. 
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Intermediate as prepared 
in Example 1, at 84% solids 
6,609 pounds 
Xylol 43.5 pounds 
Methyl alcohol 96.5 pounds 
Toluene diisocyanate 836 pounds 
1,10-phenanthroline 
(38% solution)* 16.5 pounds 
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*Commercially available as Activ-8. 
Charge intermediate and xylol to a steam-jacketed reactor fitted with a 
reflux condenser and agitator. Use slow speed agitation (about 40 rpm). 
Begin heating the mixture of intermediate and xylol while adding the 
toluene diisocyanate over a period of a half hour. Heat to 200.degree. F. 
and maintain the temperature at 200.degree. F. Cook to an anticipated 
viscosity of 120 seconds in a standard 10.65 mm Gardner viscosity vial, 
which requires about four hours. Commence cooling at the anticipated end 
point and pump in 96.5 pounds of methyl alcohol below the liquid level 
with the condenser on. Cool to 120.degree. F., add the phenanthroline 
solution and pump the mixture to storage. 
The finished product has the following properties: 
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Body Z3-Z4 
Non-volatile content 85% 
Color (Gardner) 5-7 
Acid value of non- 
volatile resin 5 
Pounds per 
U.S. gallon 8.35 
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EXAMPLE 4 
Example 4 illustrates the conversion of the oil-modified intermediate of 
Example 2 into an oil-modified polyurethane. 
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Oil-modified inter- 
mediate of Example 2 2,415 pounds 
Toluene diisocyanate 435 pounds 
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Heat the intermediate to 110.degree. F. in a reactor equipped with an 
agitator. To the stirred intermediate, add the toluene diisocyanate at the 
rate of 0.15 gallons per minute. After four gallons have been added, 
increase the flow rate to 0.4 gallons per minute. When all toluene 
diisocyanate has been added, hold at 110.degree. for one hour, then allow 
to cool. 
The final product has the following properties: 
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Body Z-Z1 
Non-volatile content 60.3% 
Color (Gardner) 6-7 
Acid value of non- 
volatile resin 0.38 
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EXAMPLE 5 
This example illustrates the preparation of a 1,000-gallon batch of the 
alkaline emulsion of polyurethane and latex: 
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Polyurethane resin at 85% 
solids, from Example 3 
1,335 pounds 
Ammonium hydroxide, 
concentrated 40 pounds 
Polyoxyethylated nonyl- 
phenol containing 
65% ethylene oxide 172 pounds 
Water 832 pounds 
Vinyl acetate-di-2-ethylhexyl 
maleate copolymer latex at 
55% solids or vinylacrylic 
latex at 55% solids 6,561 pounds 
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Heat the polyurethane resin solution to approximately 85.degree. F. in a 
high-shear mixing vessel. Add the ammonia slowly, with agitation. After 
the ammonia is well incorporated as indicated by the homogeneity of the 
mixture, add the polyoxyethylated nonylphenol, then the water. Finally, 
add the vinyl emulsion gradually and observe the inversion from a 
"water-in-oil" state to the "oil-in-water" state. If the inversion is 
properly executed, a small particle size emulsion results, generally below 
3 micron average particle size. After inversion, continue agitation for at 
least ten minutes. Filter and pump to storage. 
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The finished emulsion has the following properties: 
Viscosity 54-60 Krebs units 
Non-volatile 
content 55% 
pH 8.5-9.5 
Pounds per 
U.S. gallon 8.8 
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EXAMPLE 6 
To accomplish a corrosion inhibiting latex coating particularly useful as a 
metal primer, the composition can include the blend of a polyurethane 
solvent resin (any one of examples 1-4 above) emulsified (per example 5) 
and a film forming interpolymer such as an acrylic emulsion (also example 
5). This combination has corrosion resistance per se but preferably is 
combined with corrosion inhibiting pigments such as barium metaborate, 
barium chromate, lead silica chromate, zinc yellow chromate, strontium 
chromate, zinc oxide, calcium chromate, calcium borosilicate composite, 
used singly or in combination. A mixture of 70 parts strontium chromate 
and 30 parts iron oxide forms an improved pigment additive having blister 
resistance and stability, with the iron oxide further reducing both the 
water solubility of the strontium chromate as well as the overall cost of 
the formula. 
EXAMPLE 7 
A universal primer for metal and wood must resist corrosion and tannin 
bleed. A composition for this purpose can include any of the pigments 
listed in Example 6 but since most wood primers are white the preferred 
pigments or combination thereof are: 
Barium metaborate 
Calcium borosilicate composite 
EXAMPLE 8 
A resin where the interpolymer is a 100% acrylic latex can be prepared as 
follows: 
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Preparation of Acrylic Polyurethane Emulsion 
585 gallon batch: 
Polyurethane resin at 85% 
solids, from Example 3 
450 pounds 
Ammonium hydroxide 
concentrated 9 pounds 
Polyoxyethylated nonyl- 
phenol containing 65% 
ethylene oxide 60 pounds 
100% acrylic thermoplastic 
emulsion at 46% solids 
4,737 pounds 
5,256 pounds total 
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Heat the polyurethane resin solution to approximately 85.degree. F. in a 
high-shear mixing vessel. Add the ammonia slowly with agitation. After the 
ammonia is well incorporated, as indicated by the homogeneity of the 
mixture, add the nonylphenol. Finally add the acrylic emulsion gradually. 
After inversion, continue agitation for at least ten minutes, filter and 
pump to storage. The finished emulsion has the following properties: 
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Wt. per gal. 9 pounds 
Visc. 50-55 KU 
pH 9-9.5 
Non vol. 49% plus or minus 1% 
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When this acrylic polyurethane emulsion is used in conjunction with 
corrosion-inhibiting pigments in a properly formulated paint, a highly 
water-resistant and rust-resistant film results. 
EXAMPLE 9 
The properties of water-resistance and corrosion-inhibition may be further 
enhanced by the addition of approximately 1.5% (by weight of the total 
resin) of a silicone polymer (1.5% .times. 5,256 lbs. = 79 lbs). The 
silicone polymer is added directly to the polyurethane resin as 
illustrated below: 
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Preparation of Silicone Acrylic Polyurethane 
Emulsion 614 gallon batch: 
Polyurethane resin at 
85% solids 450 pounds 
33% silicone resin 
dissolved in mineral 
spirits 79 pounds 
Ammonium hydroxide 
concentrated 9 pounds 
Polyoxyethylated nonyl- 
phenol containing 65% 
ethylene oxide 60 pounds 
100% acrylic thermoplastic 
emulsion at 46% solids 
(exterior latex paint grade) 
4,737 pounds 
at 49% N.V. 5,335 pounds total 
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Manufacturing procedure same as Example 6. The physical properties same. As 
measured in a salt fog laboratory testing apparatus, the silicone acrylic 
polyurethane emulsion has more corrosion inhibition than the acrylic 
polyurethane emulsion without silicone. 
EXAMPLE 10 
An illustration of a corrosion-inhibiting paint utilizing the silicone 
acrylic polyurethane emulsion is as follows: 
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Preparation of a Corrosion-Inhibiting Latex 
Paint 106 gallon batch: 
Water 108 pounds 
Hydroxyethylcellulose 
thickener 4400 cps 2 pounds 
Pigment dispersant, sodium 
salt of polymeric 
carboxylic acid 9.9 
Polyoxyethylated nonyl- 
phenol containing 65% 
ethylene oxide 2.2 pounds 
Ethylene glycol 23.3 pounds 
Ester alcohol consisting of 
2,2,4-trimethylpentane- 
diol-1,3,monoisobutyrate 
15.8 
Titanium dioxide 50 pounds 
Mica 325 mesh 12.5 pounds 
Strontium Chromate 
Pigment 70 pounds 
Iron oxide 30 pounds 
1-(3-chloroallyl)-3,5,7- 
triaza-1-azonia 
adamantine chloride 
1 pound 
Anhydrous sodium potassium 
aluminum silicate 
extender pigment 125 pounds 
Let Down Phase 
Alkaline silicone acrylic 
polyurethane emulsion of 
Example 9 at 49% solids 
666 pounds 
Aluminum hydroxide 
concentrated 2 pounds 
Water 8.3 pounds 
1,126 pounds total 
Physical Properties 
P.V.C. 25% 
Wt./gal. 10.66 pounds 
Viscosity 72 KU 
pH 8.5 
Non vol. 55% 
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Manufacturing Instructions 
Use a disc type high speed disperser. 
Add ingredients in the order shown with the disperser on at slow speed. 
Increase agitator speed for dispersion phase and hold for ten minutes 
before the additions of the let down phase. 
Decrease agitator speed for the let down. Filter and pump to storage.