CA2032094A1 - Aqueous coating composition - Google Patents

Abstract

AQUEOUS COATING COMPOSITION

ABSTRACT

An aqueous composition comprising a film forming latex binder having a glass transition tempera-ture (Tg) of at least 0°C and a synthetic elastomer composition having a Tg of at least -10°C selected from the group consisting of polybutadiene, ethylene propyl-ene copolymer, butyl rubber, nitrile rubber, poly-chloroprene, polyisoprene, and mixtures thereof wherein the difference between the Tgs of the binder and the elastomer is at least 15°C and the coating composition has a tubular viscosity of about 3 to about 20 seconds to pass a 50 g sample through a 1" cylindrical tube having 0.125" orifice with an applied pressure of 10 pounds/sq" (psi).

Description

2~32~4 AQU~OUS CQATING ~CMMPOSITION

FI~D O~ IN~NTION

- The invention is concerned with a water based coating composition employing synthetic rubber composi-tions.

DESCRIPTION OF T~ PRIOR ART

U.S. Patent No. 4,537,926 describes aqueous chip-resistant coating compositions exhibiting a viscos-ity of at least 5000 centipoise containing binders such as ethylene vinyl acetate copolymers, carboxylated ethylene vinyl acetate, epoxy functional acrylic resin, carboxylated styrene-butadiene resin, carboxylated acrylic, hydroxy functional acrylic, self-crosslinking acrylic. These binders may be applied to a variety of substrates, for example, electrocoated substrates.

U.S. Patent No. 4,130,523 describes aqueous polymer latexes that are produced by emulsion polymer-ization having a total solid content of nearly 70 volume percent.

8~MMARY OF T~ INV~TION

The present invention is an aqueous coating composition comprising a film forming latex binder having a glass transition temperature (Tg) of at least 0C and a synthetic elastomer latex in which synthetic elastomer having a Tg of at least -10~C is selected from the group consisting of polybutadiene, ethylene propyl-ene copolymers, butyl rubber, nitrile rubber, poly-21D3~'094 chloroprene and polyisoprene wherein the difference between the Tg of the binder and the elastomer is at least 15C and the coated co~position has a viscosity of about 3 to about 20 seconcls to pass a 50 g sample through a 1l' cylindrical tube having 0.125 "orifice with an applied pressure of 10 pounds/sq" (psi).

Also described is a method of coating particu-larly difficult to coat substrates such as electrodepos-ited primers with top coats thereon, including those that have a base coat and/or a clear coat coating composition on top thereof.

The coating composition likewise can be characterized as a chip-resistant and/or a sound deadener coating composition.

D~SCRIPTION OF PREFERRED ~MBODIM~NT8 The coating composition of the present inven-tion is comprised of a film forming latex binder. The latex binders that may be utilized are described in U.S.
Patent No. 4,537,926, hereby incorporated by reference.

Generally, any latex binder of the present invention may be used; however, for application to cathodically electrodeposited organic coatings, prefera-bly, the binders used in this invention will be chosen from one of the following groups of polymers:
a. ethylene vinyl acetate copolymer;
b. carboxylated ethylene vinyl acetate;
c. epoxy functional acrylic resin;
d. carboxylated styrene-butadiene resin;
e. carboxylated acrylic;
f. hydroxy functional acrylic; and g. self-crosslinkiny acrylic.

2~c~2~94 Preferably, each of the copolymers used will have an average molecular weiclht of at least 50,000 and more preferably greater than 200,000 with a Tg of at least O~C.
-The synthetic elasto~er latex compositions that may be employed are poly~ers with a Tg of at least -10C such as polybutadiene, ethylene propylene copoly-mers, butyl rubber, nitrile rubber, polychloroprene and polyisoprene and the like. A preferred composition is polychloroprene and, in particular, carboxylated poly-chloroprene, generally available as neoprene latex 115, a trademark of DuPont.

While applicant does not wish to be bound by any theory of operability of the invention, it is believed that due to the strong adherence of the film forming binder latex to the synthetic elastomer compo-sition, that the viscosity has a tendency to increase.
In general in the coating composition, the ratio of the weight of the film forming latex to the synthetic elastomer latex may range from 10-90:90-10 parts by weight. Most preferred is 0.9-1:1 part by weight, and even more preferably, a 1 to l by weight ratio.

As in any high viscosity composition, addi-tives are used such as fillers and thickeners. By "filler" is meant a material which reinforces the coating composition and may or may not be inert.
Although other fillers may be used, some of the commer-cially avaiiable fillers which may be used are the calcium carbonate fillers, a talc, such as Emtal-41, a trademark of the Englehard Company; a clay, a calcium meta~ilicate, such as Wallastonite NYAD-400, a trademark 2~32~94 of Interpace Company; a silico;n dioxide, such as Imsil A-10, a trademark of Illi~ois ~[inerals, or Gold ~ond R, a trademark of Tammsco; a sodium-potassium-aluminum silicate, such as Minex 7, a trademark of Kraft Chemical Company; a ground feldspar, such as LU-330, a trademark ~ of Lawson United; a titanium dioxide, such as TR-900, a trademark of DuPont; an aluminum tri hydrate; a carbon black, such as Raven H-20, a trademark of Columbia Company; and a pyrogenic microsphere processed from fly ash, such as Orbaloid, a trademark of Midwest Filler Products. Preferably the filler will be a fly ash derivative, such as the pyrogenic microspheres provided by Midwest Filler Products Company.

Surfactants may be beneficial. For example, where carbon black or pyrogenic microspheres are used, increased dispersion of the filler may be effectuated by addition of a surfactant, nonyl/octyl phenol ethylene oxid-~ adduct e.g. Igepal type (trademark of GAF Corp.), glycols or their ethoxylated derivatives. Other surfactants may be used.

Other dispersing aids may be employed such as anionic polyelectrolyte carboxylated acrylic polymers, e.g. Nopcosperse 441 of Henkel, Tamol 100 or 150 of Rohm and Haas, and the like.

Many of the conventional flow or filming aids enhance flow, minimize foaming and sometimes improve freeze-thaw stability while retarding the drying rate of the applied coating to enhance leveling and to promote a more continuous coating. Some film forming components include diethylene glycol, butoxyethoxy-ethyl acetate, diacetone alcohol, butoxyethoxy-ethanol, ethoxyethoxy-ethanol, alkyl monoeth~rs of ethylene glycol, propylene 2~209~

glycol, and the like. Mixtures of these flow aids may also be used.

some additives which may be used are humec-tants, azeotroping agents, thickeners, and defoamers.
This coating composition is preferably an air dry system and, therefore, these agents should not be used if they detract from the curing cycle.

Due to the extremely high solids (70-90%) of this coating, without additi~es the coating would tend to dry on its outer surface first to form a skin. This is undesirable because skin formation or skinning traps water underneath, which leads to blistering, and because surface skins break off and become imbedded in the material, which causes the spray nozzle to clog.

To prevent un~esirable clogging, a humectant may be added in an effective amount. Some suitable humectants are hexylene glycol; ethylene glycol; glycer-ine; a defoamer of the high boiling mineral oil type modified with silicone, such as Colloids 681, a trade-mark of Colloids Corporation; butyl Carbitol, a trade-mark of Union Carbide for butyl ether of diethylene glycol; methyl cellosolve acetate (MCA), a trademark of Union Carbide for methyl ether of ethylene glycol acetate; propylene glycol; polypropylene glycol; and 2,2,4-trimethyl-1,3-pentane diol monoisobutyrate. At present, it appears that propylene glycol is the best of these.

Even then, the coating may not dry fast enough. For this reason, an azeotroping agent, a water miscible organic solvent with a faster evaporation rate than water, is added. As the azeotroped mixture of 2~3209~

solvent and water evaporates, it does so at a faster rate than the water would have. Some suitable azeotrope forming agents are acetone, methanol, isopropyl alcohol, and ethanol. Isopropyl alcohol appears to the best azeotroping agent known for use with this invention.

Thickeners may also be added. Generally, thickeners are added in an amount sufficient to attain a desired viscosity and rheology. As a rule, only small amounts will be used, preferably in the 5 to 10% by weight range. However, thickeners are not essential.
The following are some of the commercially available thickeners which are acceptable for use with this invention: a polyacrylate, such as Nalco 955-068, a - trademark of Nalco Corporation; a dispersed acrylic thickener, such as Printing Concentrate 430, a trademark of Polymer Industries, Inc.; a clay, such as Attagel 50, a trademark of Englehard Company; and a kaolin clay, such as McNamee Clay, a trademark of R.T. Vanderbilt Company; Rheolate 1, a trademark of NL Industries;
Bentone EW, a bentonite clay, a trademark of NL Indus-tries.

Defoamers may be used and are added to prevent or minimize foaming. A wide variety of defoamers may be used for this purpose. A few of the commercially available defoamers which may be employed are as fol-lows: stearate type defoamers, such as Deefo M-165 and Deefo 495: an anionic stearate type defoamer, such as Deefo 972; and a silicone modified stearate type defoamer, such as Deefo 918, all trademarks of Ultra Adhesives Corporation; low silicone level defoamers, such as Nalco 2300, a trademark of the Nalco Corpora-tion, and such as Patco 513 and Patco 577, trademarks of C.J. P.atterson Company; a blend of soap, nonionic surfactant and petroleum hydrocarbon modified with low levels of silicone, such as Nopco NDW and Foamaster B, and NXZ, trademarks of Henkel Corporation; a blend of nonionic surfactant and petroleum hydrocarbon, such as Foamaster VL, trademark of Henkel Corporation; a blend of silica derivatives and petroleum hydrocarbon, such as Foamaster S and Foamaster O, trademarks of Henkel Corporation; a mineral oil type defoamer, such as Colloids 999, a trademark of Colloids Corporation; high boiling mineral oil type defoamers modified with sili-cone, such as Colloids 681, Colloids 675 and Colloids 694, trademarks of Colloids Corporation; and a silicon based defoamer, such as Antifoam 60, a trademark of General Electric Corporation.

Although cross-linking agents could be used, the coating compositions of this invention, with the exception of the self-crosslinking acrylic, are prefera-bly thermoplastic.

Other materials may be added such as an effective amount of a preservative e.g., benzisothiazo-line or pyrithione containing materials, preferably Proxel GXL, a trademark of ICI Americas, Inc. for an aqueous solution of l,2-benzisothiazoline-3-one.

The pH of the composition may range from 3 to 11. However, preferably the pH will range from 6 to 8.5.

Due to the high resistance to flow of the coating compositions of the present invention, a need has arisen to describe this resistance. For purpos s of this application, it is called "tubular viscosity". By tubular viscosity is meant the amount of time in seconds ~32~94 that it takes a 50 gram sample to pass through a 1"cylindrical tube having a 0.125" orifice with an applied pressure of 10 pounds per square inch (psi). In the present case, a tubular viscosity of from 3 to about 20 seconds is the desired range, preferably 4 to about 12 seconds, and even more preferably, 4 to about 8 seconds.

Having described the invention in general, listed below are embodiments, wherein all parts are parts by weiqht and all temperatures are in degrees Centigrade unless otherwise indicated.

ExamDle 1 A water base coating composition was prepared from the following materials:
Amount Trademark Material lbs. Chemical Name Owner Neoprene 21.47 Carboxylated Dupont Latex 115 Polychloroprene (47% wt. resin solids in H20) Igepal C0-630 0.12 Nonylphenol GAF
Polyethylene Oxide Adduct Styronal ND11.19 Carboxylated BASF
656 (50% wt. Styrene/Butadiene solids in H20) Dispersion Nopcosperse 44 1.10 Dispersant Henkel Corp.
Nopco NXZ 0.12 Petroleum Henkel Derivative and Corp.
Additives Snowhite 850 42.54 Calcium Carbonate R.J.
Marshall Orabolid 21.27 Fly Ash Megaloid 2~320~

Attagel 50 0.30 Attapulgite Clay Englehardt TINT-AYD WD 0.30 Carbon Black Daniel 2350 Dispersion Products Bentone EW 0.50 Bentonite Clay NL Ind.
- 10% wt. in H20 Rheolate ~1 0.11 Acrylic Rheo- NL Ind.
logical Additive The above composition has the following physical characteristics:

Specific Gravity 13.5+.3 Solids Content, % 81~ +1 Tubular Viscosity 4-8 sec Color Black Particle Size: screen Pass through 0.76mm (0.030 in) mesh The above composition was sprayed onto cold rolled steel that is coated with a cathodic electro-coated composition and air dryed for 72 hours at ambi-ent. The cured product had the following characteris-tics.

Cold Resistance 12"x12" sample was baked @
150F for 14 days and then dryed at 10F for 4 hours.
There was no cracking or loss of adhesion.
Corrosion Resistance No rusting away from scribe;
(ASTM B117 after No lifting on blow off 336 hours) 2~32~9~

Chip ResistanCe Gravelometer Test Spray gravel onto the cured coated substrate using 5 pints of gravel which passes through a 16 mm space screen but retained on a g.5 mm space screen using 70 psi of pressure at -18C, (General Motors specifica-tion number 9508P).
* a. 20 mils (wet film) * b. 40 mils (wet film) ~ No chips, lifting or * c. 80 mils (wet film) ) adhesion loss *Substrates a) PPG Uniprime 3150A
b) PPG Uniprime 3150A; PPG, base coat/clear coat c) PPG Uniprime 3150A; DuPont, base coat/clear coat In a determination of the chip-resistant capabilities of the coating composition, it was applied to three different substrate where the substrates are described as follows:
a) PPG Uniprime 3150A (a cathodic electrodeposited coating composition onto cold rolled steel) with 20 mils of wet film. After curing, there were no chips, lifting or adhesion loss;
b) PPG Uniprime 3150A; a product with a PPG base coat/
clear coat top coat that was applied with 40 mils of the sound deadening composition. After curing, there were no chips, lifting or adhesion loss;
c) The cold rolled steel substrate was electrocoated with PPG Uniprime 3150A and top coated with DuPont base coat and clear cozt with 80 mils wet film of the sound deadening composition. There were no chips, lifting or adhesion loss.

Sound Deadenin~: (Geiger plate method whereby a 20" x 20" metal plate coated with the above composition is excited with an electromagnet at desired temperatures and what is measured is a decay rate of sound, i.e., sound deadening property of coated substrate).

a. 21C (70F) 12 dB (decibel)Jsec. decay rate of sound b. 38 C 10.7 dB/sec., decay rate of sound -Process Requirements sag: The above coating composition was applied to a cathodic electrocoated substrate at the indicated lG thickness and sag of film measured.

a. 40 mils (wet film) o Sag b. 80 mils (wet film) 0 Sag Pressure StabilitY: The above coating composition was subjected to a pressure of 3000 psi for 72 hours to determine any caking.
No Caking Wash Off Resistance: The above ~oating composition was applied to a cathode electrocoated substrate and washed as indicated.
21~C (70F); 70% R.H. No Material displacement or wash off 30-C (90~F); 85% R.H. No material displacement or wash off Stability Requirements: The above coating composition was subject to a temperature of 43-C (110F) for 72 hours. Viscosity measurements were made before and after heating.
Elevated Tubular Viscosity Temperature 72 hrs. Initial 4.2 sec.;
Q 43-C (llO-F) Final 4.4 sec.

To demonstrate the storage stability of the coating composition, it was able to withstand 35ac for 60 days.

2~3209~

Examp l e S 2 - 3 Additional formulations that were prep~red are Neoprene and styrene-butadiene as follows:

Neoprene 115 35.79 22.26 PL-456 (Trademark of 11.09 Polysar, Inc. for carboxy lated styrene/butadiene dispersion 50% by wt.
resin solids in water Igepal 630 0.10 0.09 Noposperse 44 0.53 0.67 Nopco NXZ 0.10 0.09 Snowhite 950 41.04 42.95 Fly Ash 21.01 21.11 Attagel 50 0.51 0.58 Tint hyd 2350 0.51 0.67 Rheolate #1 0.41 0.50 Substrate C of Pass* Pass*
Example 1 Substrate B of Pass* Pass*
Example 1 Pounds per 0.63 0.65 s~uare foot of dried coating on substrate Sound Deadening 3.95 12.4 (Geiger plate method of Example 1~ deter-mined at ambient temperature and pressure (d/b sec) *Gravelometer test of Example 1 run at -lO~F

2032Q9~L

E~mple 4 A modified version of the coating composition of Example 1 was prepared as follows:
Amount Cha~ical Trademark/
~aterialLbs. N~e Owner Neoprene21.42 Carboxylated Poly- Dupont Latex 115 chloroprene Igepal C0630 0.12 Nonylphenol Poly- GAF
ethylene Glycol Styronal ND llo 16 Carboxylated Styrene BASF
656 Butadiene Disperson Nopcosperse 1.10 Proprietary Disper- Henkel 44 sant Corp.
Nopco NXZ0.12 Petroleum Derivative Henkel and Additivies Corp.
Proxcel GXL 0.21 Aqueous Solution of ICI Amer-1,2 benzisothiazoline icas, Inc -3-one Snowhite 850 42.44 Calcium Carbonate R.J.
Marshall Orabaloid21.23 Fly Ash Megaloid Attagell 50 0.30 Attapulgus Clay Englehardt TINT-AYD WD0.30 Surfactant/Water/ Daniel 2350 Carbon Black/Glycol Products Dispersion Bentone EW1.10 Bentonite Clay NL Inds.
10% in water Rheolate 10.50 Acrylic Rheological NL Inds.
~dditive 2~2~

The coating compositions of the present inven-tion may have a wet csating thickness of from 10 mils to 100 mils, preferably 15-90 mils, and even more prefera-bly, 20 to 80 mils.

- 5 While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It i5 not intended herein to mention all of the possible equivalent forms or ramifi-cations of the invention. It is understood that the terms used herein are merely descriptive rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.

Claims (31)

1. An aqueous composition comprising a film forming latex binder having a glass transition tempera-ture (Tg) of at least 0°C and a synthetic elastomer composition having a Tg of at least -10°C selected from the group consisting of polybutadiene, ethylene propyl-ene copolymer, butyl rubber, nitrile rubber, poly-chloroprene, polyisoprene, and mixtures thereof wherein the difference between the Tg of the binder and the elastomer is at least 15°C and the coating composition has a tubular viscosity of about 3 to about 20 seconds to pass a 50 g sample through a 1" cylindrical tube having 0.125" orifice with an applied pressure of 10 pounds/sq" (psi).

2. The composition of claim 1 wherein the ratio of the film forming latex to the synthetic elasto-mer composition ranges from 90-10:10-90 parts by weight.

3. The composition of claim 2 wherein the ratio ranges from 0.9-1.1:1.

4. The composition of claim 1 wherein the film forming latex binder is selected from the group consisting of:
(i) an ethylene vinyl acetate copolymer;
(ii) a carboxylated ethylene vinyl acetate;
(iii) epoxy functional acrylic resin;
(iv) carboxylated styrene-butadiene resin;
(v) carboxylated acrylic;
(vi) hydroxy functional acrylic; and (vii) self-crosslinking acrylic and mixtures thereof, dispersed in the water.

5. The composition of claim 1 wherein the synthetic elastomer is polychloroprene.

6. The composition of claim 5 wherein the polychloroprene is carboxylated polychloroprene.

7. The composition of claim 1 wherein the latex binder is styrene butadiene.

8. The composition of claim 4 wherein the latex binder is an ethylene vinyl acetate copolymer.

9. The composition of claim 4 wherein the latex binder is a carboxylated ethylene vinyl acetate.

10. The composition of claim 4 wherein the latex binder is an epoxy functional acrylic resin.

11. The composition of claim 4 wherein the latex binder is a carboxylated styrene-butadiene resin.

12. The composition of claim 4 wherein the latex binder is a carboxylated acrylic.

13. The composition of claim 4 wherein the latex binder is a hydroxy functional acrylic.

14. The composition of claim 4 wherein the latex binder is a self-crosslinking acrylic.

15. A method for increasing the sound deaden-ing property of a metal substrate comprising the steps of:

a). applying to the metal substrate an effective sound deadening amount of an aqueous composi-tion comprising a film forming latex binder having a glass transition temperature (Tg) of at least 0°C and a synthetic elastomer composition having a Tg of at least -10°C selected from the group consisting of polybuta-diene, ethylene propylene copolymer, butyl rubber, nitrile rubber, poly- chloroprene, polyisoprene, and mixtures thereof wherein the difference between the Tgs of the binder and the elastomer is at least 15°C and the coating composition has a tubular viscosity of about 3 to about 20 seconds to pass a 50 g sample through a 1"
cylindrical tube having 0.125" orifice with an applied pressure of 10 pounds/sq" (psi); and b). drying the coating composition on the substrate.

16. The method of claim 15 wherein the drying of the coating composition in step (b) is by air at ambient temperature and pressure.

17. The method of claim 16 wherein the substrate to be coated has a top coat coating composi-tion applied thereto and a clear coating applied on top of the top coat prior to the application of the coating composition of subsection (a).

18. The method of claim 15 wherein the coating composition of step (a) has a weight ratio of the film forming latex to the synthetic elastomer composition ranges from 90-10:10-90 parts by weight.

19. The method of claim 18 wherein the ratio ranges from 0.9-1.1:1.

20. The method of claim 18 wherein the film forming latex binder is selected from the group consist-ing of:
(i) an ethylene vinyl acetate copolymer;
(ii) a carboxylated ethylene vinyl acetate;
(iii) epoxy functional acrylic resin;
(iv) carboxylated styrene-butadiene resin;
(v) carboxylated acrylic;
(vi) hydroxy functional acrylic; and (vii) self-crosslinking acrylic and mixtures thereof, dispersed in the water.

21. The method of claim 18 wherein the synthetic elastomer is polychloroprene.

22. The method of claim 21 wherein the polychloroprene is carboxylated polychloroprene.

23. The method of claim 15 wherein the substrate to be coated has previously been coated by a cathodic electrodeposition coating composition.

24. The method of claim 15 wherein the latex binder is styrene butadiene.

25. The method of claim 15 wherein the latex binder is an ethylene vinyl acetate copolymer.

26. The method of claim 15 wherein the latex binder is a carboxylated ethylene vinyl acetate.

27. The method of claim 15 wherein the latex binder is an epoxy functional acrylic resin.

28. The method of claim 15 wherein the latex binder is a carboxylated styrene-butadiene resin.

29. The method of claim 15 wherein the latex binder is a carboxylated acrylic.

30. The method of claim 15 wherein the latex binder is a hydroxy functional acrylic.

31. The method of claim 15 wherein the latex binder is a self-crosslinking acrylic and mixtures thereof, dispersed in the water.