CA1234441A

CA1234441A - Multiple use acrylic primer composition

Info

Publication number: CA1234441A
Application number: CA000428353A
Authority: CA
Inventors: Paul P. Bruylants
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1982-05-21
Filing date: 1983-05-17
Publication date: 1988-03-22
Also published as: BE896806A

Abstract

ABSTRACT OF THE DISCLOSURE
A coating composition useful as a putty, primer surfacer or primer for the finishing or repair of automobile or truck bodies; the composition contains pigments and a binder of (1) an acrylic polymer having a backbone of polymerized styrene, hydroxy alkyl acrylate or methacrylate and side chains containing glycidyl ester groups and (2) a polyisocyanate preferably of a biuret of hexamethylene diisocyanate and the composition contains a corrosion inhibiting pigment such as basic zinc phosphate. The composition can be applied by conventional techniques to painted, primed or unprimed metal substrates, plastic substrates and resin reinforced fiberglass substrates; the composition has excellent adherence to these substrates and provides a surface to which conventional ambient temperature curing acrylic or alkyd resin enamels will adhere.

Description

TITLE
A Multiple Use Acrylic Primer Composition BACKGROUND OF THE INVENTION
This invention is related to a coating composition and in particular to an acrylic primer composition having multiple uses.
In repairing finishes of automobiles and truck bodies after damage or in factory finishing such bodies, a putty is applied to areas which have small surface defects such as scratches or mars. The area then is sanded smooth before application of a primer coat for topcoat of paints. A primer surfacer is applied to areas which have small surface defects and then is sanded to form a smooth surface before the application of a topcoat. A non sanding primer is applied over areas which are relatively free from surface defects but require priming before the topcoat is applied. All of the above compositions must have good adhesion to the substrate which usually is metal but can be resin reinforced fiberglass or a reinforced plastic or an existing paint finish on such substrates and must provide a surface to which a topcoat or finish coat of paint such as an ambient temperature curing acrylic enamel will adhere. The putty and primer surfacer must be soundable. Presently, three different types of compositions are required for the putty, primer surfacer and the primer along with appropriate reducers and activators for each. It would be convenient and result in considerable savings for a user if one composition could be used which could be readily formulated into a putty, primer surfacer or primer by the addition of appropriate reducers end activators.

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2 ~L23~
This invention is directed to such a composition and in addition the composition provides excellent corrosion resistance to metal substrates.
SUMMARY OF THE INVENTION
S The coating composition contains about 20-80% by weight of binder and about 20-80% by weight of an organic liquid and contains pigment in a pigment to binder weight ratio of about 300/100 to 30/100; the binder contains about (a) 60-~0% by weight, based on the weight of the binder, of an acrylic polymer that has a backbone of polymerized units of styrenes hydroxy alkyd acrylate or hydroxy alkyd methacrylate, each having 2-4 carbon atoms in the alkyd group and the side chains are ester groups of O O O OH
.. .. , ...... .
--C--O--R--O--C--R~--C-OCH SHEA O
2 " 2 O O O H OWE
-C-O-R-O-C-Rl-C-O-C-CH2 O

5 or mixtures thereof;
wherein R is a saturated hydrocarbon radical having 2-4 carbon atoms, R is an aromatic radical R is a tertiary aliphatic hydrocarbon group having 8-10 carbon atoms and the polymer has a number average molecular weight of about 1,000-15,000; and (b) 20-40% by weight, based on the weight of the binder, of a polyisocyanate of the formula o 3 I
~C-NH(R3)NCo CN(R3)-N
\ C-NH(R3)NCo O
where R3 is an aliphatic hydrocarbon radical having 1-12 carbon atoms and wherein the composition contains about 1-16% by weight, based on the weight of the pigment, of a corrosion inhibiting pigment.
DESCRIPTION OF TOE PREFERRED EMBODIMENTS
The coating composition of this invention can be used as a putty, a primer surfacer or as a primer by formulating the composition with the proper additives. When the composition is used as a spray able high solids putty, the composition has a binder weight solids content of about 60-80%. When used as a primer surfacer or as a primer, the composition has a binder weight solids content of about owe The composition contains pigments in a pigment to binder weight ratio (P/B ratio) of about 300/100 to 30/100. When used as a putty or a primer surface, the composition has a P/B ratio of about 150/100 to 250/100 and preferably 200/100 to 210/100. When used as a primer, the composition has a P/B ratio of about 100/100 to 200/100 and preferably about 160/100 to 180/100~
Typical pigments that can be used are for example burettes, talc, carbon black, titanium dioxide, black iron oxide, hydrous magnesium aluminum silicate, ferrite yellow iron oxide, red iron oxide and the like. To provide corrosion resistance, the composition contains about 1-16% by weight, based on I
the total weight of pigment, of a corrosion inhibiting pigment which preferably is basic zinc phosphate. Other corrosion inhibiting pigments con be used such as zinc or calcium molybdates or mixtures thereof and can be used in combination with basic zinc phosphate pigments The pigments are formed into mill bases by blending the pigments with the acrylic polymer or another dispersing resin and dispersing the pigment by conventional means such as ball or pebble milling, sand grinding, attritor grinding and the like. The resulting dispersion is then blended with polymer solution and other constituents used in the composition.
Conventional solvents and delineates are used to adjust the application viscosity of the composition such as zillion, Tulane, mineral spirits, ethylene glycol monthly ether acetate, ethylene glycol monobutyl ether acetate, ethyl acetate, acutely acetone, high solvency hydrocarbon solvents having a boiling point of about 150-lg0C and mixtures thereof.
The binder of the composition is about 20-80~ by weight of an acrylic polymer and 20-80% by weight of a polyisocyanate. The preparation of the acrylic polymer is disclosed in Vista U.S. Patent

3,558,564 issued January 28, 1971.

The acrylic polymer has a backbone of polymerized units of styrenes hydroxy alkyd acrylate or hydroxy alkyd methacrylate. The side chains of the acrylic polymer which are attached directly to the carbon atoms of the backbone and comprise about 10-75% by weight of the polymer and have the formulas as set forth above in the summary of the invention.
The side chains are formed by reacting the hydroxy I
alkyd acrylate or methacrylate with an aromatic dianhydride and then further reacting the resulting product with glycidyl ester.
Typical hydroxy alkyd acrylates and methacrylates that can be used to form the acrylic polymer have 2-4 carbon atoms in the alkyd group and are hydroxy ethyl acrylate, hydroxy propel acrylate, hydroxy bottle acrylate, hydroxy ethyl methacrylate, hydroxy propel methacrylate, hydroxy bottle methacrylate and the like.
Androids of dibasic aromatic acids, such as phthalic acid, uvitic acid and cumidinic acid are used to form the acrylic polymer. Often it is desirable to use a halogen substituted android of one of the above aromatic dicarboxylic acids, such as tetrabromophthalic android. Halogen substituted androids in which the halogen substituent is either chlorine, Rumania or fluorine are particularly useful in forming fire retardant coating compositions Other androids that can be used are hexahydrophthalic android, tetrahydrophthalic android, 1, 4, 5, I 7, 7-hexachloro-bicyclo~2.2.1]-Hutton, 3~dicarboxylic android. I-One preferred that provides a good quality polymer is phthalic android.
The preferred glycidyl ester used to form the acrylic polymer is a mixed glycidyl ester described in U.S. Patent 3,275,583, issued September 27, 1966~ and is manufactured and sold by the Shell Chemical Company as Corroder* E ester.
This glycidyl ester is of a synthetic tertiary carboxylic acid and has the general formula *denotes trade mark .. .

......
--. . ..................................................................... ... .... ....................... ......

I

where R2 is a tertiary aliphatic hydrocarbon group S of 8-10 carbon atoms.
One preferred acrylic polymer is the polymerization product of about 40-50% by weight of styrenes 15-20% by weight of hydroxy ethyl acrylate 10-15% by weight of phthalic android and 20-30% by weight of the above preferred glycidyl ester.
The acrylic polymer has a number average molecular weight of about 1,000-15,000 determined by gel permeation chromatography using polystyrene as a standard.
Polyisocyanates are used to cross link the acrylic polymer. Preferred polyisocyanate is a Burt of the formula:

C-N~(~3)NCo CON (R No ~C-MH(R3)NCo . O
wherein R is an aliphatic hydrocarbon group having 1-12 carbon atoms. One particularly preferred Burt, since it forms a high quality coating, R3 is a saturated straight chain hydrocarbon group having 6 carbon atoms. These burettes can be made according to Mayer et at. U.S. 3,245/941, issued April 12, 1966.
For applying the composition, a two component system is used, i.e., the solution of a polyisocyanate is in one package and the solution of the acrylic polymer is in a separate package. The two solutions are thoroughly mixed before applying the coating composition. This is necessary since in I

most cases, the "pot life" of the system is relatively short since the reaction between the acrylic polymer and the polyisocyanate occurs at rapid rate even at room temperatures.
To decrease curing time of the composition after application, about 0.01-1.0~ by weight, based on the weight of the binder, of a reaction catalyst can be added to the coating composition. In a two component system, the catalyst can be added to a solution of the acrylic polymer. Typically useful catalysts are organ tin catalysts, such as dibutyl tin dilaurate, dibutyl tin do 2-ethylhexoate, stuns octet, zinc octet, stuns owlet, and the like; zinc naphthenate, vanadium acutely acetonate, zirconium acutely acetonate and the like.
To further decrease the curing time of the - coating composition, about .01% to about 1%, by weight of the binder, of an amine can be used with one of the aforementioned catalysts. Illustrative of amine which can be used are deathly ethanol amine, triethylene Damon, heptamethylisobiguani~e, triethylamine, pardon, dimethylaniline and methyl morpholine. Deathly ethanol amine is preferred.
The "pot life" of the composition may be extended by the addition of pot life extenders such as those shown in the U.S. Patent 3,314,834, issued April 18, 1967, in particularly 2,4-pentanedione.
A "one-package" coating composition can be prepared by using a polyisocyanate whose isocyanate groups have been blocked with a blocking agent such a methyl ethyl ketoxime. This eliminates the need for mixing the acrylic polymer and polyisocyanate solutions just before use. When this composition is applied and baked at a temperature of 150-160C, the I

blocking agent is released, permitting the isocyanate to react with the acrylic polymer.
The composition can be applied to primed and unpriced metal substrates, to plastic substrates such as polypropylene, polystyrene, styrene/butadiene/acrylonitrile polymers, polyester resin reinforced fiberglass substrates and the aforementioned substrates having an existing pain finish. Any of the usual application methods such as spraying, dipping, brushing, flow coating and the like can be used. These coatings can be air dried or baked at a relatively low temperature of about 50-120C for about 15 minutes-2 hours.
If a composition is applied as a putty relatively thick coats of 5-30 miss are applied. If the composition is used as a primer surfacer or as a primer, coats of 0.5-5 miss in thickness are applied The composition has excellent adhesion to the aforementioned substrates and provides a surface to which an enamel topcoat adheres. Typical topcoats that can be applied are alkyd enamels, ambient temperature curing acrylic enamels, thermosetting acrylic enamels, acrylic dispersion enamels, epoxy enamels and the like.
The following examples illustrate the invention. All quantities are on a weight basis unless otherwise indicated. Molecular weights are determined by gel permeation chromatography using polystyrene as a standard.
EXAMPLE
A high solids pigmented composition is prepared as follows:

I

Parts by portion 1 Weight Polymer solution (16~ polymer 28.450 solids in zillion ox a polymer ox styrene/hydroxyethyl acrylate/
phthalic anhydride/"Cardura" E ester in a weight ratio of about 45/16.5/13.5/25, the glycidyl ester has the formula O\ O
/ if 2 where R is a tertiary aliphatic hydrocarbon group of 8-10 carbon atoms, the polymer has a hydroxy number of 2.4 and a number average molecular weight of about 4500 and prepared according to the process of Vista U.S. Patent 3,558,564 issued 1/26/71) Zillion 3-000 Portion 2 20 Black iron oxide pigment 0.200 Portion 3 Anti-setting dispersion (10 parts 0.950 Ben tone* 34-hydrous magnesium aluminum silicate, 5 parts dispersion agent solids high molecular 25 weight salt of a polycarboxylic acid in zillion, and 85 parts zillion) Dispersion agent 0.650 (described above) Portion 4 Burettes pigment 13.750 Portion 5 White titanium dioxide pigment15.800 * denotes trade mark I
Portion 6 Ferrite yellow iron oxide pigment 3.200 Basic zinc phosphate 3.000 Corrosion inhibiting pigment Red iron oxide pigment 0.300 Portion 7 Talc pigment 14.000 Portion 8 Zillion 1.300 Portion 9 Zillion 5.100 Zinc octet solution (78.5 parts 2.600 zillion, g.36 parts zinc octet, 6.24 mineral spirits and 5.3 parts diethylethanolamine) Ethylene slickly monthly ether astute 20 Ethylene glycol monobutyl ether astute Total 100.00 Portion 1 is charged into a mixing vessel and the constituents are blended together. Portion 2 it added with mixing. Portion 3 is added with mixing. Portion 4, 5 and 6 are separately added with mixing. Portion 7 is added and the resulting composition is charged into a high speed dissolver operated at about 1000 R~P~Mo The composition is ground to a fineness of about 1.2 miss while maintaining the temperature at about 70C my aiding portion 8 during the grind. Portion 9 is then added and the resulting composition is charged into a dyno-mill and ground to a 0.6 mix fineness. The resulting composition has a pigment to binder weight I

ratio of about 280/100 and a weight solids content of about 68~.
An isocyanate activator solution is prepared by thoroughly blending the following constituents together:

Parts by Weight Polyisocyanate solution (75% solids 52.440 in hydrocarbon solvent of the Burt of hexamethylene diisocyanate) Ethyl acetate 23.780 zillion 23.780 Tuttle A reducer solution is prepared by thoroughly blending the following constituents:
Parts by Weight Ethyl acetate OWE
Acetylacetone 10.520 Tulane 20.000 Zillion 24.300 High solvency hydrocarbon 25~000 solvent having a boiling point range of 150-190~C and containing 95~ aromatic solvents Dibutyl tin dilaurate 0.180 Total 100.000 A converter solution is prepared by blending the following ingredients:

...... ....................................................................................................................................................................

Parts by Weight Ethyl acetate 18.000 Tulane 18.000 Zillion 16.800 High solvency hydrocarbon 27~200 solvent (described above) Polymer solution (described above) 20.000 Tuttle A spray able putty is prepared by thoroughly blending the following constituents:
Parts by Volume High solids pigmented 4 composition (prepared above) Isocyanate activator solution (prepared above) The above putty is sprayed onto a steel substrate. A spray gun with a nozzle opening of about 2.0-2.2 mm and a spray pressure of about 3.0-3.5 atmospheres is used. The resulting coating cures at ambient temperatures of about 20C in about 12 hours to a soundable 200 micron thick layer. The putty is useful for filling imperfections in metal substrates such as scratches and seams resulting from welding metal substrates together. After the putty is applied and cured it is readily sanded and-then a top coating or final finish is applied.
A primer surfacer is prepared by blending the following constituents:

... ... ..

Parts by Volume sigh solids pigmented composition 4 (prepared above) 5 Isocyanate activator solution (prepared above) Reducer solution 2 (prepared above) The above primer surfacer is sprayed onto a 10 steel substrate. A spray gun with a nozzle opening of about 1.6 mm and a spray pressure of about 3.5-4 atmospheres are used. The resulting coating cures at ambient temperatures of about 20~C in about lo hours to a coating that is about 40 microns thick and 15 has excellent adhesion to the steel substrate.
The primer surfacer is readily sanded to a smooth even finish to which a topcoat of an ambient .-temperature curing acrylic enamel, an acrylic dispersion enamel, an acrylic lacquer, an acrylic dispersion lacquer or an alkyd resin enamel can be applied These topcoats exhibit excellent adhesion to the primer surfacer.
A nonsandins primer it prepared by blending together the following constituents:
- Parts by Volume High solids pigmented composition 4 (prepared above) Isocyanate activator solution (prepared above) Converter solution (prepared above) 3 The above primer is sprayed onto a steel substrate coated with an alkyd resin primer. A
spray gun with a nozzle opening of about 1.4-1.8 mm and a spray gun pressure of about 3.5-5 atmospheres is used After 15 minutes, a top coating of an ambient temperature curing acrylic enamel is applied to form a smooth, glossy finish with excellent adhesion to the primer.
Steel panels each coated with one of the three compositions, i.e., putty, primer surfacer or primer, are placed in a conventional salt spray test to determine corrosion resistance. Each of the panels had good corrosion resistance.

I

Claims

The embodiments of the invention in which an exlusive property of privilege is claimed are defined as follows:

1. A coating composition comprising about 20-80% by weight of binder and about 20-80% by weight of an organic liquid and contains pigment in a pigment to binder weight ratio of about 300/100 to 30/100; wherein the binder consists essentially of about (a) 60-80% by weight, based on the weight of the binder, of an acrylic polymer having a backbone and side chains wherein the backbone consists essentially of polymerized units of styrene, hydroxy ethyl acrylate and the side chains consist essentially of ester groups selected from the group consisting of or mixtures thereof;
wherein R is a saturated hydrocarbon radical having 2 carbon atoms, R1 is phenylene, R2 is tertiary aliphatic hydrocarbon group having 8-10 carbon atoms and wherein the polymer has a number average molecular weight of about 1,000-15,000, said side chains comprising 10-75% by weight of the polymer; and (b) 20-40% by weight, based on the weight of the binder, of a polyisocyanate of the formula where R3 is (CH2)6 and wherein the composition contains about 1-16% by weight, based on the weight of the pigment, of a corrosion inhibiting pigment selected from the group consisting of basic zinc phosphate and mixtures of basic zinc phosphate and zinc molybdate and calcium molybdate and about 0.01% 01.0% by weight, based on the weight of the binder, of a reaction catalyst selected from the group consisting of zinc octoate, organo tin catalyst, a metal naphthenate and a metal acetonate.

2. The coating composition of Claim 1 having a binder solids content of about 60-80% by weight in the form of a sprayable putty.

3. The coating composition of Claim 1 in which the corrosion inhibiting pigment consists of basic zinc phosphate.

4. The coating composition of Claim 3 in which the acrylic polymer consists of polymerized units of about 40-50% by weight of styrene, 15-20% by weight of hydroxy ethyl acrylate, 10-15% by weight of phthalic anhydride and 20-30% by weight glycidyl ester.

5. The coating composition of Claim 4 in which the catalyst is zinc octoate or dibutyl tin dilaurate.

6. The coating composition of Claim l having a binder solids content of about 30-50% by weight.