CA1267487A - Acrylic and acrylic/epoxy copolymer composition - Google Patents

Abstract

A B S T R A C T
Package and tank stable, low temperature self-curing, cation-active aqueous soluble or dispersible coating compositions are prepared by copolymerizing blocked meta-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate (m-TMI) with various vinyl unsaturated monomers optionally in the presence of epoxy-amine adduct. These cation-active polymers when acidified or partially acidified provide aqueous solutions or dispersions especially useful as low temperature curable vehicles in cathodic electrocoating.

Description

6~48~

ACRYLIC AN~ ACRYLIC/EPOXY COPOLYMER COMPOSITIONS AS
SELF-CURING CATHODIC ELECTROCOATING VEHICLES
BACKGROUND OF THE INVENTION

The invention relates to improved cathodic electrocoating vehicles containing blocked isocyanate functionality together with other functionality i.e.
OH, NH, etc., capable of producing a self-cure in an electrocoating system.
In U.S. 3,984,299 and 4,031,050 Jerabek teaches a method of electrocoating wherein the electro-depositable (cathode) composition comprises a blocked polyisocyanate and a hydroxyl-containing adduct being the reaction product of a primary or secondary amine and a polyepoxide wherein the adduct is solubilized with acid to provide catlonic groups. Hicks, U.S. 4,225,479 teaches aqueous resinous compositions salted with acid for electrodeposition wherein the composition is the reaction product of a polyepoxide and an amine mixture of C8 18 aliphatic monoamine and an aliphatic diamine containing one primary and one tertiary amine group reactive with epoxide groups.
In U.S. 3,947,338, Jerabek and Marchetti teach cathodic electrocoating method using a self-curing polyurethane resin derived ~rom the reaction product oE an epoxide with a primary or secondar~ amine and a partially blocked organic polyi~ocyanate.
More recent systems relate to the copoly-!

j 7 L7~

merization of various vinyl unsaturated monomers inthe presence of epoxy resin adducts. Diefenbach et al, EB 3123536, teach an acidified aqueous binder for cathodic electrocoating wherein acrylic or methacrylic esters, hydroxy or amino substltuted monomers and other non-functional vinyl monomers are copolymerized by emulsion polymerization in the presence of cationic synthetic resins such as adducts of epoxy resin with amines, poly caprolactone and diketimines. Subsequent mixing of a partially blocked diisocyanate further reacted with an alkane type polyol, i.e. trimethylol propane effects the crosslinking of the deposited coating. Gimple el al, U.S. 4,399,256 have conducted polymerizations with copolymerizable N~ alkenyl) isocyanate, particularly vinyl isocyanate.
It is further known to free radical polymerize isocyanoethyl methacrylate (IEM) in dry solvents with itself or with a variety of acrylic or styrenic monomers without substantial damage to the isocyanate functionality (see Paul E. Cranely, A Latent Crosslinker for Coatings and Adhesive Resins, 27th Annual Technical Conference of the Cleveland Society for Coating Technology, May 15, 1984)~
Regulski and momas (Organic Coatings Applied Polymer 25 Science Proc., 48, pp 1006 (1983) determined deblockin~
temperatures for various blocked isocyanatoethyl methacrylates polymerized in the presence of methyl methacrylate and ethyl acrylate. Brixius and Si~ns, U.S. 4,446,175, teaches coatings based on IEM polymers and copolymers with various monomers using mercaptan chain-transfer agents. Bortnick (U.S 2,718,516~ had earlier described high molecular weight polymers based on ~meth) acrylic ester isocyanates having a plurality of isocyanate groups. Oriel et al, U.S. 4,264,748 teach epoxy resin coating compositions cured with IEM/acrylat~ copolymers prepared ~rom IEM or blocked IEM. Ori~l and Flowers, U.S. 4,401,794 teach copoly-~.1 126748'7 merization of various, acrylate and vinyl aromatic monomers with isocyanatoalkyl esters of unsaturated carboxylic acid (IEM) under anhydrous conditions to form moisture curable coatings.
Hazan, U.S. 4,167,499 teaches a graft copolymer comprising a monoepoxide portion said to be grafted onto an acrylicamine backbone having amine or hydroxyl functionality used in conjunction with conventional aminoplast crosslinkers. Sulling and Kuntz, U.S. 3,453,223, teach graft copolymerization of acrylonitrile, blocked polymerizable isocyanates under free radical catalysts in the presence of an aliphatically saturated alcohol having at least two primary or secondary hydroxyl groups. Schafer (U.S. 4,429,096) teaches copolymers prepared from acrylamide and the quaternary salt of para-isopropenyl~ -dimethylbenzyl isocyanate with diethylaminoalkanols or alkamines.
A major shortcoming of existing commercial cathodic electrocoat resin systems is the high (350-400F.) baking temperature required to achieve adequate coating cure and resistance properties.
Where a cure temperature of less than 350F. is possible, there are usually problems such as lack of storage or tank stability.
The present invention relates to improved sel~-curinq amino cation-active aqueous acid dis-persible polymer coating compositions based on polymers and copolymers of unsaturated, polymerizable blocked isocyanate monomers, especially metaisopropenyl-~dimethylbenzyl isocyanate.
SUMMARY OF THE INVENTIOW
The present invention relates to new package-stable an~ tank-stable self-curing cation-active aqueous dispersible coating compositions containing amino, hydroxyl and blocked isocyanate ~unctiona1ity.
These are prepa~ed by polymerizing or copolymerizing:
~1 74~7 (a) at least 5 weight percent of a polymerizable blocked monoisocyanate having the formula:

CH2=c-R2-NcoM
wherein Rl is hydrogen or Cl 3 lower alkyl group;
R2 is a diradical selected from group consisting of phenylene, benzylene or ,-dimethylbenzylene group;
and M is an isocyanate blocking agent residue; said blocked monoisocyanate being polymerized alone or copolymerized with (b) 30 to 95 weight percent polymerizable comonomer comprising at least one member of the group consisting of acrylate and methacrylate esters, styrene, vinyl chloride, vinyl.idene chloride and vinyl acetate and wherein said acrylate or methacrylate esters are selected from alkyl, hydroxyalkyl, alkylaminoalkyl and dialkylaminoalkyl esters; wherein the weight percentage of (a) and (b) total 100; and wherein said polymerization is optional-~o ly carried out in the presence of (c) 60 to 300 weight percent of an amine-epoxy adduct comprising the reaction product of an epoxide and an organic amine having at least one primary or secondary amino group reactive with said epoxide; said percent (c) being based on total weight of (a) and (b) monomer;
the co~x~ition so ~ n~d ~rising sufficient amino or free hydroxyl groups to render the composition self-curable and having an ionizable amino m~x~en, derived either from m~x~r ~b), amulr~pxxy adduct (c) or a combmation thereof, sufficient to provide an amuno cation activity of from about 35 to 175 millie~uivalents per 100 grams of resin solids and to di~se or dissoLve said polymer in an aq~s medium on acidi~ication or partial acidification.
A ~urthex aspect relate~ to the us~ of new cati~nic-v~hicle~ or coating various substrates, particularly u~e~ul in the cathodic electrocoating O~
metal~ and the re~ulting coated product .

7'~

DETAILED DESCRIPTION OF THE INVEMTION
. _ The instant amino cation-active aqueous cathodic electrocoa-tings are acidified or partially acidified compositions derived by polymeri~ation of various vinyl monomers including amino and hydroxy containing monomers with various polymerizable organic monoisocyanates, optionally in the presence of various epoxy-amine adducts. The amino cation-activity of the instant polymer composition can be derived either from the vinyl monomer or from the epoxy-amine adducts which on acidification provide water soluble or dispersible compositions useful in the cathodic electrocoating of metals incluing aluminum, iron, and other substrates.
Useful polymerizible ~locked monoisocyanates (a) include a variety of aryl or aralkyl isocyanates having vinyl unsaturation capable o~ participating in free radical induced copolymerization with other vinyl monomers or oligomers. These include, for example, 2C vinyl benzyl isocyanates, isopropenyl benæyl isocyanates, vinyl aryl isocyanates such as vinyl phenyl and isopropenyl phenyl i~ocyanates and the like. Isopropenyl phenyl isocyanates and isopropenyl benzyl isocyana;tes~can be prepared by known methods including U.S. 3,654,336; 4,379,767; 4,39~,074;
4,399,073; and 4,439,616. ~he most preferred monomer is meta-isopropenyl ~,~-dimethylbenzyl isocyanate wherein the isocyanate ~unctionality is ~ully blocked with common blocking agents. In general the blocked isocyanate polymerizable monomer will have the structure C~2-C - R2-N~ICOM wherein Rl is hydro~en or C'l 3 lower alkyl; R2 is the difunctional radical selected from the group phenylene, benzylene and ~ dl~ub~ u~dbenzyl~ne; and M represents a blocking agent resi~ue. Suitable blockin~ agents ~1 4~

are those known in the art including alcohols, phenols ketoximes, and the like. Especially preferred block-ing agents are caprolactam and 2-ethylhexyl alcohol or mixtures thereof. The general method of preparation is to add the isocyanate to the blocking agent with or without a catalyst, such as an organo-tin compound, over a period of time sufficient to control the exotherm, at a temperature high enough to achieve a reasonable blocking rate but low enough to prevent polymeri.zation through the double bond or the reverse deblocking reaction. This temperature is normally 50-120C., depending on the particular isocyanate/
blocking agent combination and the catalyst in use.
Normally, a 0 to 10% excess of blocking agent is used;
reaction is complete when free NCO content is essential-ly zero, as determined by either infra-red absorption spectroscopy or titration with standard n-butylamine solution.
The copolymerizable vinyl monomers (B) use for copolymerization with the polymerizable blacked monoisocyanate (A) to form the acrylic or acrylic/
epoxy nitro~en containing cationic resin include various monomers, such as styrene, vinyl toluene, (meth) acrylate esters, amino-bearing monomer such as dimethylaminoethyl (meth)- acrylate or hydroxyl-bearing monomer such as hydroxyethyl acrylate. Vinyl halides, vinyl acetate, and vinylidene halides are also useful copolymerization monomers. The copolymerizable vinyl monomers (B) are used in the instant invention in amounts of from 0 to about 95 weight percent basis total combined weight of A and B, pre~erably from about 40 to 85 percent and most advantageously from 45 to 60 weight percent. ~he vinyl monomer is co-polymerizable with the blocked isocyanake monomer and the copolym~rization can be don~ with or wi~hout the am~n~-a~duct compon~n-~ ~C).
he vinyl monomer (B) component usually 3~74~

comprises several different monomers which serve different purposes in the finished polymer. For example, the alkyl ~meth)acrylate esters contribute to the polymer chain; the alXylaminoalkyl (meth)acrylate esters provide the amino functionality from which the amino cation-activity is derived by subsequent full of partial acidification. It is understood that similar cation-activity can be derived totally or in part by the epoxide/amine adduct (C) when the polymerization is conducted in the presence of (C) component. The hydroxyl-bearing vinyl monomer, i.e.
hydroxyalkyl (meth)acrylates is useful in providing active hydrogen moiety, usually as a side chain off the main polymer chain, which contributes to the cross-linking activity for cure with the latent isocyanategroups. I'his functionality (OH) can be provided with (C) components (-C - C - N) or alternatively the -OH
OH
functionality can be provided by glycol compounds added during the polymerization step or later. All three aspects and combinàtions are considered to be part of this invention. It will be appreciated that the amount of hydroxyl-bearing monomer depends in part on the reactive hydro~yl content o~ the epoxy resin. All o~
the hydroxyl-bearing functionality may be derived ~rom either vinyl monomer or the aminated epoxy resin. When the hydroxyl functionality is deri~ed from both monomer and aminated~epoxy resin the content from each source may be varied widely.
Referring next to the amine-epoxy adduct ~C), such adduct~ are well known in the coatings art. These products are formed by reacting an organic polyepoxide hav~ng epoxy equivalents per mole greater than one and pre~erably about two, with an amine. The epoxides are exempli~ied in U.S. 4,294,741 column 3, line 26 through column 4 t line 13. Use~ul amine-epoxy adducts r~ .
~J~

~74&~7 are d~Kxibed in the following patents: U.S. 3,984,299 where such adduct, contrary to the instant invention is used as the do~ant or only resin vehicle; U.S. 3,367,991; U.S. 3,321,548;
U.S. 2,887,458; U.S. 4,066,525; and U.S. 4,119,599.
s Preferred amines useful in preparing the amine-epoxy adduct include amine having hydroxy functionality which can participate in the crosslinking reaction with the deblocked isocyanate functionality in the cure step. Such amines include the alkanolamines such as diethanolamine, ethanolamine, and in some cases triethanolamine. Such primary alcohols are quite reactive with isocyanates and contribute to the polymer crosslink-ability more prominently than do the secondary alcoholio functionality produced in the formation of the a~ne ~t.
Useful amune-ep~cy adducts include the reaction ~ct is the reaction product of diglycidyl bisphenol A resin and a pri-mary or secol~ry amune having a molecular ~ ght o~ from 600 to 4000. Such an adduct conveniently supplies at least 10% of the am~xrcation activity of the self-curable ccmp~siticn.
Although the amine epoxide adducts are pre-ferred, other non-amine adducts can be used, as ~or example, when the amino cation portion is derived from the amino containing acrylates. Such compounds include polyep~des x~d with polyhydric ooqx~rds, polycarb~lic acids and e~es ~n ex~bd ~ith polyols an~ cycl;c polyols, Aqueous coatings of the above type may be appli~d either by conven~ional coa~ techniques or by electrodepoYition. For cathodic electrodeposition it is nece9-~ary ~o neutralize or partially neutralize the amine portion of the polymer. Thus by neutralizing the amino-resins desirable equeous compositions can be obtained for electrodepo~ition from solutions or dlspersions of pH ~etween 3 and 10. This can be aeeompli~hed by aeidifieation o~ all or part of the 35 a~nlno group ~unction~lity by an inorganie acid or an o~:~an~e aald 3ueh a~ ~or exampl~ ~ormie, ae~ia, or laetle aeid and tA~ like~. In determining the degr~e of neutr~lization ~ox a partic:ular sy~tem, an amount o~

, 7~8~

neutralizing acid is selected to solu~ilize or disperse the resin. Phosphoric ~cid is the preferred inorganic acid and lactic acid is a preferred organic acid for the acidification or partial acidification to form the amino ca-tion active polymer compositions.
Usually the cathodic resin composition will be present in water at concentrations from about 1 percent to about 30 percent by weight of resin although more concentrated aqueous compositions may be prepared for storage and shipping. Preferred useful concen-trations are from 5 to 15 weight percent. The un-pigmented compositions may be eiectrocoated to deposit clear aqueous coatings on the cathode electrode. More commonly these compositions will be used in combination with various pigment compositions and other additives known to the electrocoating art. Conventional pigment containing compositions include organic and inorganic pigments and additives such as titanium dioxide, oxides, carbon black, talc, barium sulfate as well as pigments or pseudo pigments known as plastic pigments such as polystyrene particles and the like.
In the electrocoating process the aqueous cathodic bath containing the neutralized cationic resin, pigments, additives etc., is placed in contact with an electrically conductive anode and an electrically con-ductive cathode serving as the article to be coated.
Current is applied (usually D.C.) at voltages between 50 and 500 volts whereby the organic resin migrates and is deposited on the metal substrate to be coated such as for example, steel, aluminum, iron and the like. Other bath components such as pigments, filler and additives are conveyed with the cathodically charged resin and deposited on the substrate. After deposition the coating substrate is removed from the bath and rinsed with deionized water prior to effect~
in~ a cure. ~he depQsited coatings cure at elevated temperatures by the usual ~echniclues o~ heating in ~ J~

7~

ovens or with infrared heaters. While the prior art curing temperatures usually range from about 350F.
to about 425F., an improved aspect of the instant invention allows cure temperatures in the range of from 250F. - 350F. to provide metal coated products having excellent corrosion and detergent resistance.
Various other acrylic backbone or epoxy/
acrylic backbone nitrogen-containing cation resins may be prepared by substituting different monomers or by modifying the type and amount of the epoxy/
amine adducts present during the polymerization.
The following examples are meant to illustrate the invention without implying any limita-tion therein. Unless otherwise defined parts and percentages are expressed as weight percentages and temperatures are given as degrees Centrigrade.
PREPARATION OF BLOCKED _SOCYANATES

Blocked Meta-Isopropenyl ~,a-dimethylbenzyl Isocyanate 452 Grams meta-isopropenyl ~ dimethylbenzyl isocyanate (m-TMI) was added to 279 grams (10~ excess) caprolactam plus 0.68 grams dibutyltin dilaurate (DBTDL) catalyst u~der agitation at 90C. over a

2~ period of 1 hoù~r, and held for a Eurther 4 hours, at which point the free NCO content, by n-butylamine titration, had dropped to 0.35%~ This NCO con-tent corresponds to a conversion of ~7.3%. The product was a crystalline solid, with MP = 60-62C. in the crude state and MP = 62-64C. after crystallization and drying from petroleum ether.

., .~ .
~i ~L~674~3~7 Pre~aration of Aminated EPOXY Resin Weight Parts DER 333 tlow mol. wt. epoxy resin) 1355 from Dow Chemical Co., WPE=200 Bisphenol A 460 Nonyl Phenol 153.4 Ethylene glycol mono-butyl ether (EGMBE) 1013 Di-ethanolamine 219 DER 333,(~rade Mark) bisphenol A and nonyl phenol were charged into a 5 liter flask, and upheated slowly to 140C., at which point the exothermic reaction (with cooling) carried the temperature to 170C.
The reaction was held at 170C. to a constant viscosity as measured on the ICI cone and plate viscometPr. The constants at this stage were: Viscosity at 125C. =
43.8 poise; WPE (wt. per epoxide equivalent) = 940.
The EGMBE solvent was added, the batch cooled to 120C.
and the diethanolamine added all at once, with cooling to hold 120C. This reaction was given 2 hours at 120C. and assumed complete. Final constants were:
Non-volatile 67.8~ by wt.
Base number (NV) 54 m~. KOH per gm Viscosity at 25C. 412 poise Pure Acrylic Resin Formula Wei~ht Parts 1. M-TMI/CPL adduct of Example 1 293 gms.
2. Methyl methacrylate 367 gms.

3. Ethyl acrylate 563 gms.

4. 2-hydroxyethyl acrylate 110 gms.

5. Dimethylaminoethyl methacrylate 184 gms.

6. Vazo 64 (Dupont_Trade Mark1 43 gms. (+8)

7. Ethylene ylycol mono-hexyl ether 507 gms.
Items 1-6 were premixed as follows: Item 1 ~2~74i!~

was dissolved in items 2-5 with warming to 50C. The solution was cooled to 30C. and then item 6 was stirred in till dissolved. The monomer feed premixed was then added to item 7 in a 3 liter vessel equipped with stirrer, thermometer, reflux condenser, inert gas inlet and dropping funnel. The feed period was 2 hours at 85C. The batch was held for 1 hour, at which point a further 8 gms. of the initiator Vazo 64 was added, followed by a further 2 hour hold. Final constants were as follows:
Non-volatile content (determined) 70.0%
Corrected NV (counting caprolactam 75.6 as non-volatile) Base No. (of non-volatile) 41.5 mg. KOH/gm.
Viscosity (60% in EGMBE - 25C) 188 poise Acrylic/Styrene Resin Formula Weight Parts 1. m-TMI/CPL adduct of Example 1 293 gms.
2. Styrene 367 gms.
3. Ethyl acrylate 563 gms.
4. 2-hydroxyethyl acrylate 110 gms.
5. Dimethylaminoethyl methacrylate 184 gms.
6. Vazo 64 (Dupont) 43 gms.
25 7. Ethylene glycol mono-hexyl ether 507 gms.
This resin was processed in similar fashion to Example 3. Final Constants were:
Non-volatile (determined) 69.4 Corrected NV 74.3~
Base No. (of non-volatile~ 41.5 mg. KOH per gm.
Viscosity (60% in EGMBE - 25C. 112 poise ~2~7~

Acrylic_Copol~merized with Epoxy-Amine Adduct Formula Weight Parts 1. m-TMI/CPL adduct of Example 1 226.3 2. Styrene 40 3. Ethyl Acrylate 69.7 4. Dimethylaminoethyl methacrylate 40 5. Vazo 64 24 (+8) 6. EGMBE 215 7. Aminated Epoxy of Example 2 885 This epoxy/acrylic copolymer resin was pre-pared by exactly -the same process as Example 3 except that in this case the epoxy resin served as the "heel"
for the acrylic polymerization instead of solvent.
Also total hold time was 4 hours and a "chaser" of

8 parts of Vazo 64 was necessary to complete the conversion. Final constants were:
Non-volatile (determined) 58.9 Corrected NV 64.2~
Base No. (on NV) 46.3 mg. KOH/gm.
Viscosity (60~ in EGMBE 114 poise at 25C.) ~ Amine Epox~ AddUct 25 Formula Weight Parts 1. m-TMI~CPL adduct o~ Example 1 325.9 2. Styrene 38.5 3. Ethyl acrylate 120 4. DMAEMA 79.6 5. Vazo 64 36 (~5) 6. EGMBE 315 7. Aminated Epoxy of Example 2 885 The monomer mix items 1 to 6, was prepared exactly as for Example 3. Thi9 Was added under agita-tion at 85CI to item 7 over a period Q~ 2 hours.
The non-volatile at this point was 54.3~. Addin~
~"

5 parts of Vazo 64 and holding temperature for a 1 hour period, brought the non-volatile content to 58.6%. Final corrected NV and viscosity were respectively 65.7% and 74 poise at 60~ NV in EGMBE.

This example demonstrates a special advant-age of the present invention, using caprolactam-blocked m-TMI as the blocked isocyanate, in which both fast cure and excellent self stability are obtained. This unexpected result is attributed to the high degree of stearic strain aro~nd the bond facilitating cleavage (deblocking) to the free isocyanate at temperatures above 120C., and at the same time pro-viding a high degree o~ scearic resistance to hydrolysis lS and/or reaction with alcoholic species at ambient (less than 30C.) temperatures.
Formula Weight Parts l. m-TMI/CPL adduct o~ Example l 239.2 2. Styrene 300 3. Ethyl acrylate 460 4. Hydroxyethyl acrylate 90 5. DMAEMA 150 6. Vazo 64 35 7. EGMBE 425 Premixed items 1 to 6 were added to item 7 under agitation ovar a period of 2 hours at 85C., ~ollowed by a 2 hour hold. Corrected, determined non-volatile content was 73.8~. The following were added to convert the base resin into a clear ~eed composition:
8. Lactic acid (88~ 25

9. Deionized water 127 lO. EGMBE 273 ~he batch was held at 50C. for 16 days, checking viscosity every few days. Cure was determined at 3 bake tempera-tures ~or 20 minutes, on films applied by draw-down ~rom the base resin solution on cold-rolled i748~7 steel panels (before addition of items 8-10). The results are shown in Table 1.
The 61% increase in viscosity in 16 days at 50C. is considered excellent stability and the MEK
resistances at 300 and 325F. are very good when compared to a conventional acrylic/urethane system of the caprolactam-blocked isophorone diisocyanate type.

~i 4~7 ~ , I
~ ~ :

E~ o I .
X~
.
~ . I
o ,~ ~ .

,, i ~rl ~ a~
V O ~D 1` CO ~ O
Q .

Id R
a ~ O u. a~
~ u .

i748~

Grey Electrocoating Composition Clear Feed Weight Parts 1. Resin of Example 3 174 2. Aminated epoxy of Example 2 23.6 3. Organo-phosphate resin (a) 19.4 4. 2-ethyl hexanol 15.4 5. Propylene glycol mono-methyl ether (PGMME) 15.4 6. Lactic acid (88%) 1.8 7. Deionized water 15.4 Mix items 1 to 7 Tank .
8. Lactic acid (88~) 3.8 9. Deionized water 982 Add Clear Feed to Tank Pi~ eed Concentrate

10. Resin of Example 3 12.22

11. Lactic acid (88%) 1.46

12. DI water 37.36

13. Hydrous aluminum silicate clay 3.53

14. Rutile titanium dioxide12.34

15. Amorphous Silica 1.76

16. Carbon black .06

17. Quinacridone pigment .014

18. Deionized water 8.23 Sandmilled to a 7-8 Hegman grind fineness.
Added to tank.
(a) Epoxy phosphate: Acid No. 110 r NV 62 A grey electrocoat composition was prepared similar to Example 8 with the exception -that the resin of Example 4 was substituted for that of Example 3.

.~, .

lX67~87 A grey electroc~at composition was formulated as follows:
Clear Feed Weiqht Parts 1. Resin of Example 5 129.1 2. PGMME 8.3 3. 2-Ethyl hexanol 8.3 4. Lactic acid (88~) 1.0 5. DI water 8.3 Mix items 1 to 5 Tank 6. Lactic acid (88%) 5.4 - 7. DI water 1056 Add Clear Feed to Tank ~ d 8. Pigment Dispersion vehicle( ) 12.96 9. Lactic acid (88~) 2.06 10. Surfynol 104(b) 0.42 11. Titanium dioxide 22.1 12. Carbon black 0.42 ' 13. Clay 5O63 14. Fumed Silica 1.56 15. DI water 27.52 Added to Tank.
(a) Reaction product of diethylaminopropylamine, bisphenol A epoxy resin and a C-16 olefin epoxide.
) An acetylenic-glycol type de~oamer.

A grey electrocoating composition was prepared using the procedure o~ Example 10 except that the co-polymer resin of Example 6 was used in place o~ the resin of Example 5.

:~2~74~3~7 O N
O O U~
O O
~J
O O O O I O
Ln 11~ 0 It) U
.
Ul aa~
CO CO ~ ~ ~ Ul E~ . . . . ~ U
O O O O
~) ~Q
~ ~ .
a ,~
U~ ~ ~ ~
.~ ~ a~ ~
E-lcoco a~ ~n O

O U
t~l 1~ U a~
,U~ ^ ~ ~ ~ ~ ~

l.q U~ 1 11 ~1 E-~ ~
aJ

~ s~

U~ . . . . I I
x ~ a~
~0 V
~ Q) ,1 R tn o ~ ~ 1~ 3 _1 ,1 " .. . . ~ ,~ _ ~ X ~ Xl ~ ~

~,~

:~6~7 ~r ~1 oo oo oo oo O O ~ o oo o N N N NN N
~ U~
$
~
U
~I x ~ .-~ ~ o a I N N N N ~ ~~ ~ N a~
X ~ Oa ; O
. ~ ~ 6 o a) j U 6 H --1 O O O OO OO O ' ~d ~ 5-~
a oO o~
! :~ o ,~

O ~ N æ ~o ~ ¦ ~ N o Q~ ~a O ~

~a ~¦ ~ ~ N ~ o o o ~a ~ o ~-s~ u~ ~ ~ ~ O
i ~
u ,~ ~1 oo oo oo oo ~

o~ olno~n ~r) x ~ u 7 ~ ~~ ~ ~ ~
~ ~ o u~ a~ 0 ~
s~ r~ ~
~ ~d h .~
U . ~ S

~ X 0 $ .~::
.~
m ~

l l .~ ~ ~
-~ ,_1 .-1 N ~ ~r ~ x x x x p~ ~

~j7'~

FURTHER ASPECTS OF THE INVENTION
--_ .
An additional aspect of -the invention relates to package-stable and tank-stable self-curing cation-active aqueous dispersible coating compositions con-taining amino, hydroxyl and blocked isocyanatefunctionality. These novel coating vehicles are pre-pared by polymerizing or copolymerizing:
(a) at least 5 weight percent of a polymerizable blocked monoisocyanate having the formula:
Rl H
CH2=C--R2-NCOM
wherein Rl is independently hydrogen or Cl 3 lower alk~l O o group; R2 is a diradical -C-(CHRl)n- or -C-O(CH2)n~
where n is 1 to 3; and M is an isocyanate blocking agent residue; said blocked monoisocyanate being polymerized lS alone or copolymerized with (b) 30 to 95 weight percent polymerizable comonomer comprising at least one member of the group consisting of acrylate and methacrylate esters, styrene, vinyl chloride, vinylidene chloride and vinyl acetate and wherein said acrylate or methacrylate esters are selected from alkyl, hydroxyalkyl, alkylaminoalkyl and dialkylaminoalkyl esters; wherein the weight percentage of (a) and (b) total 100; and wherein said poly~erization is optionally carried out in the presence o~
(c) 60 to 300 weight percent of an amine-epoxy adduct comprising the reaction product o~ an epoxide and an organic amine having at least one primary or secondary amino group reactive with said epoxide; said percent (c) being based on total weight o~ (a) and (b1 monomers;
said polymer or copolymer having an ioniæable amino nitrogen, derived either from monomer (b~, amino ~S
,~

~xt~t74~t7 epoxy adduct (c) or in combination thereof, sufficient to disperse or dissolve said polymer in an aqueous medium or acidification or partial acidification.
A further aspect relates to the use of new cationic-vehicles for coating various substrates, particularly useful in the cathodic electrocoating of metals and the resulting coated product.
Useful polymerizable blocked monoisocyanates (a) for this aspect of the invention include a variety of isocyanoalkyl acrylates and methacrylates having vinyl unsaturation capable of participating in free radical induced copolymerization with other vinyl monomers or oligomers. These include, for example, isocyanatoethyl methacrylate (IEM), isocyanatoethylacrylate, isocyantopropyl acrylate, isocyanatopropyl methacrylate, isocyanatomethyl methacrylate and the like. The most preferred monomer is isocyanatoethyl methacrylate tIEM) wherein the isocyanate functionality is fully blocked with common blocking agents.

Claims (29)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A self-curable amino cation-active aqueous acid-dispersible copolymer composition containing amino, hydroxyl and blocked isocyanate functionality derived from the polymerization of:
(A) at least 5 weight percent of a polymerizable blocked monoisocyanate having the formula:
wherein R1 is hydrogen or C1-3 lower alkyl group, R2 is a diradical selected from the group consisting of phenylene, benzylene or .alpha.,.alpha.-dimethylbenzylene group or is where n is from 1 to 3: and M is an isocyanate blocking agent residue; said blocked monoisocyanate being copolymerized with (B) 30 to 95 weight percent polymerizable vinyl comonomer comprising at least one member of the group consisting of acrylate and methacrylate esters, styrene, vinyl toluene vinyl halides, vinylidene halides and vinyl acetate and wherein said acrylate or methacrylate esters are selected from alkyl, hydroxyalkyl, alkylaminoalkyl and dialkylaminoalkyl esters, wherein the weight percentages are based on the combined weights of A and B monomers and total 100 percent: and wherein said polymerization is carried out in the presence of (C) 60 to 300 weight percent of an amine-epoxy adduct comprising the reaction product of an epoxide and an organic amine having at least one primary or secondary group reactive with said epoxide; said percent (C) being based on total weights of (A) and (B) monomers; wherein said composition comprises sufficient amino or free hydroxy groups to render the composition self curable and the amine cation-activity is derived from monomer (B), amine-epoxy adduct (C) or combinations thereof is suifficient to provide an amino-cation activity of from about 35 to 175 milliequivalents per 100 gram resin solids and to effect polymer solubilization or dispersion on partial or full acidification.

2. The composition of claim 1, wherein the monoisocyanate is meta-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate blocked with caprolactam, and vinyl comonomer (b) is present at 40-85 weight percent.

3. The composition of claim 2, wherein amino-cation activity is derived solely from ionizable amino-containing acrylic or methacrylic ester monomers.

4. The composition of claims 3, wherein the amino-containing ester is dimethylaminoethyl methacrylate.

5. The composition of claim 2, wherein the amine-epoxy adduct is the reaction product of diglycidyl bisphenol A resin and a primary or secondary amine and has a molecular weight from about 600 to about 4000 and wherein said adduct supplies at least 10% of the amino-cation activity of the self-curable composition.

6. A paint comprising the composition of claim 5.

7. The process of coating a substrate which comprises (a) providing a self-curing blocked-isocyanate polymer as claimed in claim 1, 2 or 3;
(b) applying said polymer as an acidified aqueous solution or dispersion to a substrate;
(c) curing the coated substrate.

8. A process of coating a substrate which comprises a) providing a self-curing blocked-isocyanate polymer as claimed in claim 1, 2 or 3, wherein said blocked isocyanate composition is prepared by polymerizing at least 5 weight percent blocked meta-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate polymerized alone or copolymerized with one or more vinyl unsaturated copolymerizable comonomers selected from the group consisting of styrene: and alkyl, hydroxyalkyl, aminoalkyl, alkylaminoalkyl or dialkylaminoalkyl acrylate or methacrylate esters; wherein said polymerization or copolymerization is conducted in the presence of 60 to 300 weight percent of an amine-epoxy adduct, based on the total weight of the blocked isocyanate and vinyl monomers;
said polymer having an amino nitrogen content sufficient to disperse or dissolve the polymer in water on acidification or partial acidification b) applying said polymer as an acidified aqueous solution or dispersion to a substrate and c) curing the coated substrate.

9. The process of coating a substrate which comprises a) providing a self-curing blocked isocyanate polymer as claimed in claim 1, 2 or 3, wherein the copolymer is derived from styrene, hydroxyethyl acrylate, ethyl acrylate and dimethylaminoethyl methacrylate and the amine-epoxy adduct is present at 100-300 weight percent basis total monomer b) applying said polymer as an acidified aqueous solution or dispersion to a substrate and c) curing the coated substrate.

10. The process of claim g, wherein the amine-epoxy adduct is the reaction product of a diglycidyl bisphenol A
ether or ether resin and a primary or secondary amine, said product having a molecular weight from about 600 to about 4000 and wherein said adduct supplies at least 10% of the amino-cation activity of the self-curable composition.

11. The process of claim 8, wherein the self-curing polymer is formed from the monomers blocked meta-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate copolymerized with methyl metacrylate, ethyl acrylate, dimethylaminoethyl metacrylate and 2-hydroxyethylacrylate.

12. The process of claim 9, wherein the total amino content available for amino cation-activity is from about 35 to about 175 milliequivalents per 100 gram resin solids.

13. A method of electrocoating an electrically conductive surface serving as a cathode which comprises passing an electric current between said cathode and an anode in contact with an aqueous electrodepositable composition, wherein said composition comprises the acid/solubilized, or dispersed self curable composition of claim 1.

14. A metal substrate coated by the process of claim 10.

15. The polymer composition of claim 1, wherein a blocked monoisocyanate derived from isocyanoalkyl acrylate or isocyanoalkyl methacrylate is used in place of the benzylene monoisocyanate.

16. Process for cathodic electrocoating a substrate which comprises (a) providing a self-curing blocked-isocyanate polymer prepared by polymerizing at least 5 weight percent blocked isocyanatoethyl methacrylate copolymerized with 30 to 95 weight percent of one or more vinyl unsaturated copolymerizable comonomers selected from the group consisting of styrene, alkyl, hydroxyalkyl, aminoalkyl, alkylaminoalkyl or dialkylaminoalkyl acrylate or methacrylate esters; or mixtures thereof wherein said percentages are based on total weights of the blocked-isocyanate monomer and vinyl unsaturated monomer; and said polymerization is conducted in the presence of 60 to 300 weight percent of an amine-epoxy adduct, based on the total weight of the blended isocyanate and vinyl monomers;
(b) applying said polymer as an acidified aqueous solution or dispersion to a substrate;
(c) curing the coated substrate.

17. The process of claim 16, wherein the copolymer is derived from styrene, hydroxyethyl acrylate, ethyl acrylate and dimethylaminoethyl methacrylate and the amine-epoxy adduct is present at 100-300 weight percent basis total monomer.

18. A self-curable amino cation-active aqueous acid-dispersible copolymer composition containing amino, hydroxyl and blocked isocyanate functionality derived from the polymerization of:
(A) at least 5 weight percent of a polymerizable blocked monoisocyanate having the formula:
wherein R1 is hydrogen or C1-3 lower alkyl group: R2 is a diradial selected from the group consisting of phenylene, benzylene or .alpha.,.alpha.-dimethylenzylene group or is where n is from 1 to 3; and M is an isocyanate blocking agent residue, said blocked monoisocyanate being copolymerized with (B) 30 to 95 weight percent polymerizable vinyl comonomer comprising at least one member of the group consisting of acrylate and methacrylate esters, styrene, vinyl toluene, vinyl halides, vinylidene halides and vinyl acetate and wherein said acrylate or methacrylate esters are selected from alkyl, hydroxyalkyl, alkylaminoalkyl and dialkylaminoalkyl esters, wherein the weight percentages are based on the combined weights of A and B monomers and total 10. percent;
wherein said composition comprising sufficient amino or free hydroxyl groups as to render the composition self curable and the amine cation-activity is derived from monomer (b), is sufficient to provide an amino-cation activity of from about 35 to 175 milliequivalents per 100 gram resin solids and to effect polymer solubilization or dispersion on partial or full acidification.

19. The composition of claim 18, wherein the monoisocyanate is meta-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate blocked with caprolactam, and vinyl comonomer (b) is present at 40-85 weight percent.

20. The composition of claim 16, wherein amino-cation activity is derived solely from ionizable amino-containing acrylic or methacrylic ester monomers.

21. The composition of claim 20, wherein the amino-containing ester is dimethylaminoethyl methacrylate.

22. The process of coating a substrate which comprises (a) providing a self-curing blocked isocyanate polymer composition as claimed in any one of claims 18, 19 or 20, (b) applying said polymer as an acidified aqueous solution or dispersion to a substrate;
(c) curing the coated substrate.

23. The process of coating a substrata which comprises a) providing a self-curing blocked isocyanate polymer composition as claimed in any one of claims 18, 19 or 20, wherein the self-curing blocked iso-cyanate polymer composition employed is one prepared by polymerizing at least 5 weight percent blocked meta-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate polymerized alone or copolymerized with one or more vinyl unsaturated copolymerizable comonomers selected from the group consisting of styrene; and alkyl, hydroxyalkyl, aminoalkyl, alkylaminoalkyl or dialkylaminoalkyl acrylate or methacrylate esters;
said polymer having an amino nitrogen content sufficient to disperse or dissolve the polymer in water on acidification or partial acidification said composition comprising sufficient free hydroxyl group to render it capable of self-curing b) applying said polymer as an acidified aqueous solution or dispersion to a substrate and c) curing the coated substrate.

24. The process of claim 23, wherein the self-curing polymer is formed from the monomers blocked meta-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate copolymerized with methyl methacrylate, ethyl acrylate, dimethylaminoethyl methacrylate and 2-hydroxyethyl acrylate and the total amino content available for amino cation-activity is from 35 to 175 milliequivalents per 100 gram resin solids.

25. The polymer composition of claim 18, wherein the product is one obtained by using a blocked monoisocyanate derived from isocyanoalkyl acrylate or isocyanoalkyl methacrylate.

26. A method of electrocoating an electrically conductive surface serving as a cathode which comprises passing an electric current between said cathode and an anode in contact with an aqueous electrodepositable composition, wherein said composition comprises the acid/solubilized, or dispersed self-curable composition of any one of claims 18, 19 or 20.

27. Process for cathodic electrocoating an electrically conductive surface serving as a cathode which comprises passing an electric current between said cathode and an anode in contact with an aqueous electro depositable composition which comprises the acid/solubilised or dispersed self-curable composition of and one of claims 18, 19 or 20 and wherein said self-curable composition prepared by polymerizing at least 5 weight Percent blocked isocyanatoethyl methacrylate copolymerized with one or more vinyl unsaturated copolymerizable comonomers selected from the group consisting of styrene, alkyl, hydroxyalkyl, aminoalkyl, alkylaminoalkyl or dialkylaminoalkyl acrylate or methacrylate esters; or mixtures thereof.

28. The process of claim 27, wherein the copolymer is derived from styrene, hydroxyethyl acrylate, ethyl acrylate and dimethylaminoethyl methacrylate and the amine-epoxy adduct is present at 100-300 weight percent basis total monomer.

29. A paint comprising the composition of any one of claims 18, 19 or 20.