CA1067639A - Cathodic electrocoating composition and process comprising aqueous amine-substituted polymer with bismaleimide cross linking agent - Google Patents
Cathodic electrocoating composition and process comprising aqueous amine-substituted polymer with bismaleimide cross linking agentInfo
- Publication number
- CA1067639A CA1067639A CA230,735A CA230735A CA1067639A CA 1067639 A CA1067639 A CA 1067639A CA 230735 A CA230735 A CA 230735A CA 1067639 A CA1067639 A CA 1067639A
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- CA
- Canada
- Prior art keywords
- polymer
- amine groups
- cross
- bis
- cathode substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/44—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications
- C09D5/4488—Cathodic paints
- C09D5/4496—Cathodic paints characterised by the nature of the curing agents
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
- C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
- C08G59/4007—Curing agents not provided for by the groups C08G59/42 - C08G59/66
- C08G59/4014—Nitrogen containing compounds
- C08G59/4042—Imines; Imides
Abstract
ABSTRACT
A heat-curable electrocoating composition containing a polymer having pendant amine groups and a bis-maleimide crosslinking agent can be electrodeposited onto a cathode substrate disposed within an aqueous electrocoating bath. The amine groups of the polymer are protonated to render the polymer water-dispersible prior to electrodeposition. Upon electrodeposition, the amine groups become de-protonated and cross-link with the bis-maleimide upon heating to form a fully cured electrodeposited coating on the cathode substrate.
A heat-curable electrocoating composition containing a polymer having pendant amine groups and a bis-maleimide crosslinking agent can be electrodeposited onto a cathode substrate disposed within an aqueous electrocoating bath. The amine groups of the polymer are protonated to render the polymer water-dispersible prior to electrodeposition. Upon electrodeposition, the amine groups become de-protonated and cross-link with the bis-maleimide upon heating to form a fully cured electrodeposited coating on the cathode substrate.
Description
iO~7~39 Th;s invention relates to electrodeposition of water-dispersed, heat-curable polymers onto a cathode substrate and more particularly to cross-linking said electrodeposited polymers with a heat-reactive bis-maleimide.
Several processes for electrodeposition of heat-curable electro-coating polymers onto a cathode substrate disposed in an aqueous electro-coat-ing bath have been suggested. For example U.S. Patent 3,617,458 discloses an electrocoating epoxy polymer having pendant amine groups which are neutralized with an inorganic acid to render the polymer water soluble. The epoxy polymer also contains pendant carboxyl groups which cross-link with the epoxide (oxi-rane) groups of an epoxy resin upon heating to form a cured coating on the cathode substrate. Others have similarly suggested solubilizing through amine groups.
It has now been found that a bis-maleimide cross-linking agent cures a coating which has been electrodeposited onto a cathode substrate. Addition-ally, the electrocoating polymer contains pendant primary or secondary amine groups which are used for rendering the polymer both water soluble and for cross-linking with the bis-maleimides.
The present invention provides in a heat-curable electrocoating com-position containing a polymer having pendant amine groups and a cross-linking .:
agent in an aqueous dispersion for electrodeposition onto a cathode substrate disposed within an aqueous electrocoating bath, said polymer being cross-link-- able upon subsequent heating of said electrocoated cathode substrate, the im-` provement comprising: said polymer having at least about 5% pendant primary or secondary amine groups, said amine groups being protonated with acid to render said polymer water dispersible in said bath, said amine groups adapted to be-come deprotonated upon electrodeposition of said polymer on said cathode sub-! strate; and at least about 5% bis-maleimide of the formula :'' O O
':'` 1 Jl, .
/~ - Ll N - R - N ll I
~1' `~1' ~.'. O O
` :, . ~! -- 1 -- ~
10~7639 wherein R is a divalent aliphatic~ aromatic or mixed aliphatic-aromatic group having a molecular weigllt up to about 3,~no by weight of said polymer, said bis-maleimide serving for cross-linking said polymer by addition polymeriza-tion with said de-protonated pendant primary or secondary amine groups upon heating to form a heat-cured electrodeposited coating.
The invention also provides, in a process for electrodeposition of a heat-curable electrocoating composition containing a polymer having pendant ~;~ amine groups and a cross-linking agent in an aqueous dispersion onto a cathode substrate disposed within an aqueous electrocoating bath, said polymer being cross-linkable upon subsequent heating of said electrocoated cathode substrate, the improvement comprising:
~a) providing said electrocoating co~position containing(i) a polymer having at least about 5% pendant primary or secondary amine , groups, said amine groups being protonated with acid to render said polymer ~: water dispersible in said bath and ; (ii) at least about 5% by weight of the polymer of a bis-maleimide of : formula I defined in claim 1, serving as a cross-linking agent for said polymer;
~; (b) applying an electromotive potential through said bath to electro-~:: deposit said polymer and said cross-linking agent onto said cathode substrate, ~; 20 said pendant amine groups of said polymer becoming de-protonated thereby; and `.~ (c) heating said electrocoated cathode substrate, said bis-maleimide cross-linking said polymer by addition polymerization with said de-protonated . pendant amine groups to form a heat-cured electrodeposited coating.
The reaction mechanism by which cross-linking of the polymer through the bis-maleimide occurs is an addition polymerization reaction known as , . , ` the Michael-type addition reaction, as more particularly described in "Or-i~ , ~............. ganic ReactionsJ" Vol. 10 (pages 179-555), John Wiley and Sons (1959). The ~,, , . Michael-type addition reacts a primary or secondary amine group with alpha-J
~';' ' .
beta-ethylenlcally unsaturated carbon-carbon or carbonyl groups in order to achieve linking of the amine group and the carbon-carbon or ~: ,`: ' t.i';
' ~`
::- - 2 -~ i , ~0~7639 carbonyl groups. The alpha-, beta-ethylenic unsaturation of the bis-male-imides is used in the instant invention.
The electrocoating composition generally is a polymer or resin selec-ted according to final desired use from a wide variety of known polymers in the electrocoating art.
The polymers contain pendant primary and/or secondary amine groups.
By protonating such amine groups, the polymer can be water dispersed. Elec-trodeposition of the polymer de-protonates the amine groups for cross-linking with the bis-maleimide cross-linking agent in a Michael-type addition reaction.
Amine groups can be attached to the polymer by reacting free carboxyl groups on a polymer (polyester, acrylic, urethane, etc.) containing available car-boxyl groups which can be reacted with alkyleneimine or substituted alkylene-imine, as proposed in United States 3,679,564 and United States 3,617,458.
. " ' ' .
Similarly, amine groups can be introduced into the polymer by reacting pendant carboxylic acid groups on a polymer with ethylene imine or derivatives of - ethylene imine. Difunctional amines also can be reacted with reactive pendant ' carboxyl groups on the polymer.
Blocked amines also can be attached to the polymer and subsequently --~ transformed into primary amine groups by an appropriate reaction which will ;:,,`i~
be outlined in detail later herein. Such blocked amine groups can be attached -` to epoxy resins or acrylic resins having pendant oxirane groups by reacting ''7' a ketimine blocked diethylene triamine, formed from reacting diethylene tri-` amine with an excess of methyl ethyl ketone, with the polymer. Such a reaction -; can be illustrated as follows:
.... . .
,,; `
, : ..
,.,~,,, ~", : ;~
: '~
:i :
. . , '`' .
.. . . . .
/ \ /- CH2CH2N = C CH C
polymer - CH - CH2 + HN 2 3 \ CH CH N C ~ CH3 -.
OH / CH2CH2N = C CH2CH
polymer - CH2 ~ CHCH2-N CH3 CH2CH2N = C~
~ 2 3 .-. ,, :
1 Similar blocked dialkyl triamines also can be employed to attach the blocked ' amine groups as above set forth.
: :
The primary and/or secondary amine groups are pendantly attached s to the polymer. For purposes of this application, pendant amine groups : 1 include terminal amine groups. By pendantly attached is meant that such -; amine groups are attached to the polymer chain or to a pendant side chain of the polymer.
The polymer containing pendant amine groups should contain at least about 5% by weight of such pendant amine groups, and up to about ` 50% if desire.
Representative polymers containing pendant amine groups can be .,j;
~ derived from epoxy and epoxy-modified diglycidyl ethers of bis-phenol A
,~ structures, various aliphatic polyethylene or polypropylene glycol ., (diglycidal ether) adducts~ and glycidyl ethers of phenolic resins, such epoxy resins being commercially a~ailable and commonly used in the ~^ electrocoating field.
Other useful polymers containing pendant amine groups include , ...
. . .
1~i7~39 polyamide rcsin~, for example, condensation products of dimerized fatty acids coreacted with difunctional amine, such as ethylene diamine. Polyamide resins generally are between about 5n() and about 5,()0() molecular weight. Further useful electrocoating polymers containing pendant amine groups include acrylic resins having molecular weight of about 1,000 to about 100,000 polyester resins and polyurethane resins both having a molecular weight range of about 500 to about 5,000, vinyl resins, and amine resins.
Various other useful electrocoating polymers containing pendant amine groups can be advantageously employed in the electrocoating composition of this application as will become more apparent in the examples.
The cross-linking agent is a bis-maleimide having alpha, beta-ethylenic unsaturation capable of being heat reactive to cross-link the amine groups on the polymer.
Bis-maleimides are represented by the following general structure:
O O
~ N - R -:- O
where R is a divalent aliphatic, aromatic or mixed aliphatic-aromatic group , :;
~ having a molecular weight up to about 3,000.
; Alkylene-, aryl-bis-maleimides and combinations thereof are par-. ticularly useful as the cross-linking agent of this invention. Specific bis-maleimides which are particularly suited to the precepts of this invention can be selected from the group consisting of dimethylenedimaleimide, tri-methylenedimaleimide, tetramethylenedimaleimide, tetraethylenedimaleimide, pentamethylenedimaleimide, hexame*hylenedimaleimide, heptamethylenedimal-,:
: eimide, decamethylenedimaleimide; the bis-maleimides lf 4,4'-methylene-bis (orthochloro-.
:~
: ~`
10~7639 aniline), 4,4'-methylene-dianiline, 4,4'-methylene-bis (3-nitroaniline), 4-aminophenylether, N,N'-ortho-phenylenedimaleimide, N,N'-para-phenylenedimale-imide, and N,N'-meta-phenylenedimaleimide.
- Bis-maleimides can be synthesized by various methods such as are disclosed in United States Patents 2,444,536 and 3,622,321 and are generally synthesized by adding a diluted ether solution of diamine to a similar dilut-ed ether solution of maleic anhydride which results in a maleamic acid. The maleamic acid can be disposed in acetic anhydride and converted into the cor-responding bis-maleimide in the presence of potassium acetate.
In practicing this invention, the polymer is rendered water soluble :.
by adding sufficient acid to the polymer to completely neutralize the polymer.
Appropriate acids are, for example, proton-donating acids such as phosphoric, sulfuricg hydrochloric, acetic, formic, lactic, and other proton-donating organic and inoTganic acids. Water solubility is achieved by the protonating of all (primary, secondary and tertiary if there be any) amine groups of the polymer by the acid. The protonating of the amine groups of the polymer also renders the polymer positively-charged so that during electrodeposition the polymer can migrate to the cathode substrate and be deposited thereon. Also, while the pendant primary and/or secondary groups of the polymer are proton-ated, such amine groups will not react with bis-maleimide as the polymer is stable in water. A polymer having blocked amine groups is treated with a pro-ton-donating acid in water in order to protonate all amine groups for water solubility of the polymer and to remove the blocking group from the pendant :;
~; amine groups in order to convert such tertiary amine groups into protonated primary amine groups.
The neutralized polymer is blended with at least about 5% bis-male-~` imide cross-linking agent by weight of the polymer and up to about 25% if de-sired. The blend is then dispersed in water to form the electrocoating ; ~ ` r .. . .
~' ~0~7~39 bath of from about 5 to about 20~ non-volatile dispersion. The bath is generally at about 60 to about 125F, with about 70 to about 95F being preferred.
The neutralized ~protonated) polymer and bis-maleimide are both stable in the bath and no int0rreaction there occurs. The cathode substrate to be electrocoated is then immersed in the electrocoating bath while an electric potential is maintained therethrough as disclosed in United States 3,619,398. During electrodeposition the positively charged polymer along with the bis-maleimide migrate to the cathode substrate.
The protonated amine groups of the polymer become de-protonated ~lose protons) due to the electric potential applied. The polymer and bis-- maleimide are codeposited on the cathode substrate. The electric poten-tial applied to the bath is generally between about 20 and about 500 volts, with about 50 to about 300 volts being preferred.
; The coated substrate is removed from the bath, washed with water to remove excess coating, and then conven$ionally heat-cured at a temperature of at least about 100 and preferably between about 200 and : . .
400F for about 5 to about 40 minutes.
` The polymer cross-links through the de-protonated pendant pri-mary and/or secondary amine groups attached to the electrocoated polymer.
Water solubility and cross-linking of the polymer both occur through the ame pendant amine groups of the polymer.
: :~
The alpha-, beta-ethylenic unsaturation of the bis-maleimide is heat-reactive under the conditions of curing and readily reacts with ., ~
the pendant amine groups of the polymer in Michael-type addition reaction :
or addition polymerization. Upon such heating a fully cured electro-deposited coating coats the cathode substrate.
.` The cathode substrate is an electrically conductive metal such as ...
iron, steel, aluminum, copper, galvanized steel, zinc, and the like. The '~'~''` ' ,.
:
, :`' .
~06~7639 cathode substrate can be in the shape of barsg sheets, irregularly shaped forms with rounded or sharp edges, and like shapes.
The electrocoating composition can contain opacifying pigments and inert extenders such as, for example, titanium dioxide, zinc oxide, clays such as kaolinite clays, silica, talc, and the like.
The following examples show how the instant invention can be practiced, but should not be ~ngtrued as limiting the invention. In the specification all parts are parts by weight, all percentages are weight percentages, and all temperatures are in degrees Fahrenheit, unless other-wise expressly indicated.
One mole of DER 332 (trade mark) epoxy resin (Dow Epoxy Resin, . , epoXide equivalent weight 172-196, Dow Chemical Company) was reacted with two moles of cyclohexyl amine in butyl cellulose in order to attach pendant amine groups to the epoxy resin. The resin was completely neutralized with
Several processes for electrodeposition of heat-curable electro-coating polymers onto a cathode substrate disposed in an aqueous electro-coat-ing bath have been suggested. For example U.S. Patent 3,617,458 discloses an electrocoating epoxy polymer having pendant amine groups which are neutralized with an inorganic acid to render the polymer water soluble. The epoxy polymer also contains pendant carboxyl groups which cross-link with the epoxide (oxi-rane) groups of an epoxy resin upon heating to form a cured coating on the cathode substrate. Others have similarly suggested solubilizing through amine groups.
It has now been found that a bis-maleimide cross-linking agent cures a coating which has been electrodeposited onto a cathode substrate. Addition-ally, the electrocoating polymer contains pendant primary or secondary amine groups which are used for rendering the polymer both water soluble and for cross-linking with the bis-maleimides.
The present invention provides in a heat-curable electrocoating com-position containing a polymer having pendant amine groups and a cross-linking .:
agent in an aqueous dispersion for electrodeposition onto a cathode substrate disposed within an aqueous electrocoating bath, said polymer being cross-link-- able upon subsequent heating of said electrocoated cathode substrate, the im-` provement comprising: said polymer having at least about 5% pendant primary or secondary amine groups, said amine groups being protonated with acid to render said polymer water dispersible in said bath, said amine groups adapted to be-come deprotonated upon electrodeposition of said polymer on said cathode sub-! strate; and at least about 5% bis-maleimide of the formula :'' O O
':'` 1 Jl, .
/~ - Ll N - R - N ll I
~1' `~1' ~.'. O O
` :, . ~! -- 1 -- ~
10~7639 wherein R is a divalent aliphatic~ aromatic or mixed aliphatic-aromatic group having a molecular weigllt up to about 3,~no by weight of said polymer, said bis-maleimide serving for cross-linking said polymer by addition polymeriza-tion with said de-protonated pendant primary or secondary amine groups upon heating to form a heat-cured electrodeposited coating.
The invention also provides, in a process for electrodeposition of a heat-curable electrocoating composition containing a polymer having pendant ~;~ amine groups and a cross-linking agent in an aqueous dispersion onto a cathode substrate disposed within an aqueous electrocoating bath, said polymer being cross-linkable upon subsequent heating of said electrocoated cathode substrate, the improvement comprising:
~a) providing said electrocoating co~position containing(i) a polymer having at least about 5% pendant primary or secondary amine , groups, said amine groups being protonated with acid to render said polymer ~: water dispersible in said bath and ; (ii) at least about 5% by weight of the polymer of a bis-maleimide of : formula I defined in claim 1, serving as a cross-linking agent for said polymer;
~; (b) applying an electromotive potential through said bath to electro-~:: deposit said polymer and said cross-linking agent onto said cathode substrate, ~; 20 said pendant amine groups of said polymer becoming de-protonated thereby; and `.~ (c) heating said electrocoated cathode substrate, said bis-maleimide cross-linking said polymer by addition polymerization with said de-protonated . pendant amine groups to form a heat-cured electrodeposited coating.
The reaction mechanism by which cross-linking of the polymer through the bis-maleimide occurs is an addition polymerization reaction known as , . , ` the Michael-type addition reaction, as more particularly described in "Or-i~ , ~............. ganic ReactionsJ" Vol. 10 (pages 179-555), John Wiley and Sons (1959). The ~,, , . Michael-type addition reacts a primary or secondary amine group with alpha-J
~';' ' .
beta-ethylenlcally unsaturated carbon-carbon or carbonyl groups in order to achieve linking of the amine group and the carbon-carbon or ~: ,`: ' t.i';
' ~`
::- - 2 -~ i , ~0~7639 carbonyl groups. The alpha-, beta-ethylenic unsaturation of the bis-male-imides is used in the instant invention.
The electrocoating composition generally is a polymer or resin selec-ted according to final desired use from a wide variety of known polymers in the electrocoating art.
The polymers contain pendant primary and/or secondary amine groups.
By protonating such amine groups, the polymer can be water dispersed. Elec-trodeposition of the polymer de-protonates the amine groups for cross-linking with the bis-maleimide cross-linking agent in a Michael-type addition reaction.
Amine groups can be attached to the polymer by reacting free carboxyl groups on a polymer (polyester, acrylic, urethane, etc.) containing available car-boxyl groups which can be reacted with alkyleneimine or substituted alkylene-imine, as proposed in United States 3,679,564 and United States 3,617,458.
. " ' ' .
Similarly, amine groups can be introduced into the polymer by reacting pendant carboxylic acid groups on a polymer with ethylene imine or derivatives of - ethylene imine. Difunctional amines also can be reacted with reactive pendant ' carboxyl groups on the polymer.
Blocked amines also can be attached to the polymer and subsequently --~ transformed into primary amine groups by an appropriate reaction which will ;:,,`i~
be outlined in detail later herein. Such blocked amine groups can be attached -` to epoxy resins or acrylic resins having pendant oxirane groups by reacting ''7' a ketimine blocked diethylene triamine, formed from reacting diethylene tri-` amine with an excess of methyl ethyl ketone, with the polymer. Such a reaction -; can be illustrated as follows:
.... . .
,,; `
, : ..
,.,~,,, ~", : ;~
: '~
:i :
. . , '`' .
.. . . . .
/ \ /- CH2CH2N = C CH C
polymer - CH - CH2 + HN 2 3 \ CH CH N C ~ CH3 -.
OH / CH2CH2N = C CH2CH
polymer - CH2 ~ CHCH2-N CH3 CH2CH2N = C~
~ 2 3 .-. ,, :
1 Similar blocked dialkyl triamines also can be employed to attach the blocked ' amine groups as above set forth.
: :
The primary and/or secondary amine groups are pendantly attached s to the polymer. For purposes of this application, pendant amine groups : 1 include terminal amine groups. By pendantly attached is meant that such -; amine groups are attached to the polymer chain or to a pendant side chain of the polymer.
The polymer containing pendant amine groups should contain at least about 5% by weight of such pendant amine groups, and up to about ` 50% if desire.
Representative polymers containing pendant amine groups can be .,j;
~ derived from epoxy and epoxy-modified diglycidyl ethers of bis-phenol A
,~ structures, various aliphatic polyethylene or polypropylene glycol ., (diglycidal ether) adducts~ and glycidyl ethers of phenolic resins, such epoxy resins being commercially a~ailable and commonly used in the ~^ electrocoating field.
Other useful polymers containing pendant amine groups include , ...
. . .
1~i7~39 polyamide rcsin~, for example, condensation products of dimerized fatty acids coreacted with difunctional amine, such as ethylene diamine. Polyamide resins generally are between about 5n() and about 5,()0() molecular weight. Further useful electrocoating polymers containing pendant amine groups include acrylic resins having molecular weight of about 1,000 to about 100,000 polyester resins and polyurethane resins both having a molecular weight range of about 500 to about 5,000, vinyl resins, and amine resins.
Various other useful electrocoating polymers containing pendant amine groups can be advantageously employed in the electrocoating composition of this application as will become more apparent in the examples.
The cross-linking agent is a bis-maleimide having alpha, beta-ethylenic unsaturation capable of being heat reactive to cross-link the amine groups on the polymer.
Bis-maleimides are represented by the following general structure:
O O
~ N - R -:- O
where R is a divalent aliphatic, aromatic or mixed aliphatic-aromatic group , :;
~ having a molecular weight up to about 3,000.
; Alkylene-, aryl-bis-maleimides and combinations thereof are par-. ticularly useful as the cross-linking agent of this invention. Specific bis-maleimides which are particularly suited to the precepts of this invention can be selected from the group consisting of dimethylenedimaleimide, tri-methylenedimaleimide, tetramethylenedimaleimide, tetraethylenedimaleimide, pentamethylenedimaleimide, hexame*hylenedimaleimide, heptamethylenedimal-,:
: eimide, decamethylenedimaleimide; the bis-maleimides lf 4,4'-methylene-bis (orthochloro-.
:~
: ~`
10~7639 aniline), 4,4'-methylene-dianiline, 4,4'-methylene-bis (3-nitroaniline), 4-aminophenylether, N,N'-ortho-phenylenedimaleimide, N,N'-para-phenylenedimale-imide, and N,N'-meta-phenylenedimaleimide.
- Bis-maleimides can be synthesized by various methods such as are disclosed in United States Patents 2,444,536 and 3,622,321 and are generally synthesized by adding a diluted ether solution of diamine to a similar dilut-ed ether solution of maleic anhydride which results in a maleamic acid. The maleamic acid can be disposed in acetic anhydride and converted into the cor-responding bis-maleimide in the presence of potassium acetate.
In practicing this invention, the polymer is rendered water soluble :.
by adding sufficient acid to the polymer to completely neutralize the polymer.
Appropriate acids are, for example, proton-donating acids such as phosphoric, sulfuricg hydrochloric, acetic, formic, lactic, and other proton-donating organic and inoTganic acids. Water solubility is achieved by the protonating of all (primary, secondary and tertiary if there be any) amine groups of the polymer by the acid. The protonating of the amine groups of the polymer also renders the polymer positively-charged so that during electrodeposition the polymer can migrate to the cathode substrate and be deposited thereon. Also, while the pendant primary and/or secondary groups of the polymer are proton-ated, such amine groups will not react with bis-maleimide as the polymer is stable in water. A polymer having blocked amine groups is treated with a pro-ton-donating acid in water in order to protonate all amine groups for water solubility of the polymer and to remove the blocking group from the pendant :;
~; amine groups in order to convert such tertiary amine groups into protonated primary amine groups.
The neutralized polymer is blended with at least about 5% bis-male-~` imide cross-linking agent by weight of the polymer and up to about 25% if de-sired. The blend is then dispersed in water to form the electrocoating ; ~ ` r .. . .
~' ~0~7~39 bath of from about 5 to about 20~ non-volatile dispersion. The bath is generally at about 60 to about 125F, with about 70 to about 95F being preferred.
The neutralized ~protonated) polymer and bis-maleimide are both stable in the bath and no int0rreaction there occurs. The cathode substrate to be electrocoated is then immersed in the electrocoating bath while an electric potential is maintained therethrough as disclosed in United States 3,619,398. During electrodeposition the positively charged polymer along with the bis-maleimide migrate to the cathode substrate.
The protonated amine groups of the polymer become de-protonated ~lose protons) due to the electric potential applied. The polymer and bis-- maleimide are codeposited on the cathode substrate. The electric poten-tial applied to the bath is generally between about 20 and about 500 volts, with about 50 to about 300 volts being preferred.
; The coated substrate is removed from the bath, washed with water to remove excess coating, and then conven$ionally heat-cured at a temperature of at least about 100 and preferably between about 200 and : . .
400F for about 5 to about 40 minutes.
` The polymer cross-links through the de-protonated pendant pri-mary and/or secondary amine groups attached to the electrocoated polymer.
Water solubility and cross-linking of the polymer both occur through the ame pendant amine groups of the polymer.
: :~
The alpha-, beta-ethylenic unsaturation of the bis-maleimide is heat-reactive under the conditions of curing and readily reacts with ., ~
the pendant amine groups of the polymer in Michael-type addition reaction :
or addition polymerization. Upon such heating a fully cured electro-deposited coating coats the cathode substrate.
.` The cathode substrate is an electrically conductive metal such as ...
iron, steel, aluminum, copper, galvanized steel, zinc, and the like. The '~'~''` ' ,.
:
, :`' .
~06~7639 cathode substrate can be in the shape of barsg sheets, irregularly shaped forms with rounded or sharp edges, and like shapes.
The electrocoating composition can contain opacifying pigments and inert extenders such as, for example, titanium dioxide, zinc oxide, clays such as kaolinite clays, silica, talc, and the like.
The following examples show how the instant invention can be practiced, but should not be ~ngtrued as limiting the invention. In the specification all parts are parts by weight, all percentages are weight percentages, and all temperatures are in degrees Fahrenheit, unless other-wise expressly indicated.
One mole of DER 332 (trade mark) epoxy resin (Dow Epoxy Resin, . , epoXide equivalent weight 172-196, Dow Chemical Company) was reacted with two moles of cyclohexyl amine in butyl cellulose in order to attach pendant amine groups to the epoxy resin. The resin was completely neutralized with
2 moles of acetic acid. The bis-male;m;de was 1,6 hexamethylene-bis-maleimide :~, ~ which was synthesized by reacting on mole of 1,6 hexamethylenediamine with , i~
;` two moles of maleic anhydride. The resin was blended with 100 grams of the bis-maleimide and added to water to form a 7% non-volatile dispersion.
A steel panel was immersed inthe bath as the cathode and the electrocoating composition was electrodeposited therein at 50 volts for 2 minutes. The coated panel was removed from the bath, washed with water, and baked at 360F for 15 munutes. A solvent-resistant coating covered the ~: :j panel indicating that curing had taken place.
A polyester resin was prepared by reacting one mole of phthalic arhydride, one mole of succinic arhydride, and one mole of propylene glycol.
~ Such reaction was carried out in toluene with azeotropic distillation of ; water. This reaction product, an acid-terminated polyester, then was ~ .
reacted with two moles of hexamethylene diamine and the water removed to form a diamine-terminated polyester resin.
Theamine resin next was completely neutralized with 6 moles of acetic acid and blended with 20% by ~ight of meta-phenylene-bis-maleimide.
The blend was added to demineralized water to form a 10% non-volatile dis-persion. A steel panel then was cathodically electrocoated in the electro-coating bath, washed with water, and baked at 250 for 40 minutes. Again, a fully cured electrodeposited coating covered the panel.
A polyamide resin was formulated by reacting one mole of succinic anhydride with two moles of hexamethylene diamine in toluene with removal of water by azeotropic distillation.
The diamine resin then was completely neutralized with 2.5 moles -: ~
of acetic acid. The neutralized polymer is blended with 20% by weight , ~ .
' '3.' tetramethylene-bis-maleimide and this blend added to water to form a 10%
non-volatile dispersion. A steel panel was cathodically electrocoated, washed with water and baked at 360 for 30 minutes. A fully cured electro-:.
deposited coating covered the panel upon such baking.
One mole of an epoxy resin available under the trade mark DER 664 (epoxy equivalent weight of 900, Dow Epoxy Resin, Dow Chemical Company) was reacted at 60 C with two moles of the ketimine blocked diethylene tri-amine of the specification, ., , :~ CH2CH2~ C~
,.` / CH2CH3 HN
~, ` ~
;~; \ / CH3 CH CH N = C
_9_ ~, ~0~7~39 completely neutra]i~ed with 4 moles lactic acid, and blended with 20%
N,N~-para-phenylenedimaleimide. The blend was then added to deionized water to form a 7% non-volatile (solids) dispersion.
This electrocoating composition was cathodically electrodeposited at 100 volts for one minute onto steel panels. The panels then were removed from the bath, washed with water, and baked at 300 for 30 minutes. A hard, flexible, solvent-resista~tcoating covered the steel panel.
The procedure of Example-4 was followed except that the N,N'-para-phenylenedimaleimide was omitted from the blend. The electrocoated steel panels upon baking did not have a solvent-resistant coating thereon, indicating that the electrocoating had not cured.
; EXAMPLE_6 An acrylic resin was synthesized by the solution polymerization of 30% ethylacrylate, 20% stryene, 30% butyl acrylate, and 20% glycidyl . ~ ~
methacrylate. This reaction was r~ under standard solution acrylic poly-merization conditions using butyl cellulose as the solvent and azobisisobutyl nitrile as the initiator, The solution acrylic polymer contained pendant oxirane groups.
The solution acrylic polymer was reacted with 15% of the ketimine blocked diethylene triamine of Example 4 to form an acrylic resin with pendant amine groups.
The-amine-acrylic resin then was completely neutralized with 4 moles of lactic acid, blended with 20% N,N~-ortho-phenylenedimaleimide, and : ,' added to water to form an 8% non-volatile dispersion.
;
This electrocoating composition was cathodically electrodeposited . .
i onto steel panels in a manner similar to Example 4, washed with water, and baked at 400 for 25 minutes. A hard, flexible, fully cured, solvent-resistant coating covered the panels.
''. ;
:
iOfà7639 E~LE 7 methane resin was synthesized from the reaction of one mole of e~
toluenediisocyanate and one mole of t~f~n~ glycol. The diisocyanate-terminated resin was then reacted with two moles of the ketimine blocked diethylene triamine of Example 4. The amine resin was comp]etely neutralized with 4 moles lactic acid and blended with 15% of hexamethylene-bis-maleimide.
The electrocoating bath was formed by adding the resin and bis-maleimide to water to form an 8% non-volatile dispersion.
The blend was cathodically electrodeposited onto a steel panel at 100 volts for 2 minutes. The steel panel was then removed from the bath, - 10 washed with water, and baked at 400 for 10 minutes. A fully cured electro-deposited coating covered the panel.
~'::, .
A polymer-bis-maleimide was prepared by reacting 2 moles of . . . ~ .
succinic anhydride with 1 mole of polyoxyethylene glycol (molecular weight of 1540), which reaction product was further reacted with 2 moles of hexamethy-lene diamine. This polymer~diamine was dissolved in tetrahydrofuran (10%
` solution by weight) and then added to a solution of 2 moles of maleic : ~:
anhydride (10 % solution by weight in tetrahydrofuran) to form a polyether-.
bis-maleimide compound in the presence of acetic anhydride and of potassium acetate.
.
;s One mole of the epoxy resin of Example 4 (DER 664) was reacted at ~ ;
~, O
~, 60 C with 2 moles of the ketimine blocked diethylene triamine of Example 4 followed by further reaction with one mole of linseed oil fatty acid. This resin was completely neutralized with 4 moles of acetic acid and blended , with 50% polyether-bis-maleimide by weight of the resin. The blend was : , added to deionized water to form an 8% non-volatile dispersion. ~
... . . .
; This electrocoating composition was cathodically electrodeposited at 100 volts for 1 minute onto a steel panel. The panel was removed from the , ~'~ -11-~ .
.
10~7~39 bath, washed with water, and haked at 400 for 35 minutes. A hard, flexible, solvent resistant coating covered the panel.
EX~PLE 9 The neutralized resin of Example 8 (unsaturated oil-modified epoxy resin neutralized with acetic acid) was blended with 20% by weight of the bis-maleimide of 4,4'-methylene-bis-(ortho-chloroaniline). The blend was added to deionized water to form an 8% non-volatile dispersion.
- This electrocoating composition was cathodically electrocoated and baked in a manner similar to Example 8. A hard flexible, solvent resistant ` 10 coating covered the panel.
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.,;
'~' '1 ~.
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1 .
. :
;` two moles of maleic anhydride. The resin was blended with 100 grams of the bis-maleimide and added to water to form a 7% non-volatile dispersion.
A steel panel was immersed inthe bath as the cathode and the electrocoating composition was electrodeposited therein at 50 volts for 2 minutes. The coated panel was removed from the bath, washed with water, and baked at 360F for 15 munutes. A solvent-resistant coating covered the ~: :j panel indicating that curing had taken place.
A polyester resin was prepared by reacting one mole of phthalic arhydride, one mole of succinic arhydride, and one mole of propylene glycol.
~ Such reaction was carried out in toluene with azeotropic distillation of ; water. This reaction product, an acid-terminated polyester, then was ~ .
reacted with two moles of hexamethylene diamine and the water removed to form a diamine-terminated polyester resin.
Theamine resin next was completely neutralized with 6 moles of acetic acid and blended with 20% by ~ight of meta-phenylene-bis-maleimide.
The blend was added to demineralized water to form a 10% non-volatile dis-persion. A steel panel then was cathodically electrocoated in the electro-coating bath, washed with water, and baked at 250 for 40 minutes. Again, a fully cured electrodeposited coating covered the panel.
A polyamide resin was formulated by reacting one mole of succinic anhydride with two moles of hexamethylene diamine in toluene with removal of water by azeotropic distillation.
The diamine resin then was completely neutralized with 2.5 moles -: ~
of acetic acid. The neutralized polymer is blended with 20% by weight , ~ .
' '3.' tetramethylene-bis-maleimide and this blend added to water to form a 10%
non-volatile dispersion. A steel panel was cathodically electrocoated, washed with water and baked at 360 for 30 minutes. A fully cured electro-:.
deposited coating covered the panel upon such baking.
One mole of an epoxy resin available under the trade mark DER 664 (epoxy equivalent weight of 900, Dow Epoxy Resin, Dow Chemical Company) was reacted at 60 C with two moles of the ketimine blocked diethylene tri-amine of the specification, ., , :~ CH2CH2~ C~
,.` / CH2CH3 HN
~, ` ~
;~; \ / CH3 CH CH N = C
_9_ ~, ~0~7~39 completely neutra]i~ed with 4 moles lactic acid, and blended with 20%
N,N~-para-phenylenedimaleimide. The blend was then added to deionized water to form a 7% non-volatile (solids) dispersion.
This electrocoating composition was cathodically electrodeposited at 100 volts for one minute onto steel panels. The panels then were removed from the bath, washed with water, and baked at 300 for 30 minutes. A hard, flexible, solvent-resista~tcoating covered the steel panel.
The procedure of Example-4 was followed except that the N,N'-para-phenylenedimaleimide was omitted from the blend. The electrocoated steel panels upon baking did not have a solvent-resistant coating thereon, indicating that the electrocoating had not cured.
; EXAMPLE_6 An acrylic resin was synthesized by the solution polymerization of 30% ethylacrylate, 20% stryene, 30% butyl acrylate, and 20% glycidyl . ~ ~
methacrylate. This reaction was r~ under standard solution acrylic poly-merization conditions using butyl cellulose as the solvent and azobisisobutyl nitrile as the initiator, The solution acrylic polymer contained pendant oxirane groups.
The solution acrylic polymer was reacted with 15% of the ketimine blocked diethylene triamine of Example 4 to form an acrylic resin with pendant amine groups.
The-amine-acrylic resin then was completely neutralized with 4 moles of lactic acid, blended with 20% N,N~-ortho-phenylenedimaleimide, and : ,' added to water to form an 8% non-volatile dispersion.
;
This electrocoating composition was cathodically electrodeposited . .
i onto steel panels in a manner similar to Example 4, washed with water, and baked at 400 for 25 minutes. A hard, flexible, fully cured, solvent-resistant coating covered the panels.
''. ;
:
iOfà7639 E~LE 7 methane resin was synthesized from the reaction of one mole of e~
toluenediisocyanate and one mole of t~f~n~ glycol. The diisocyanate-terminated resin was then reacted with two moles of the ketimine blocked diethylene triamine of Example 4. The amine resin was comp]etely neutralized with 4 moles lactic acid and blended with 15% of hexamethylene-bis-maleimide.
The electrocoating bath was formed by adding the resin and bis-maleimide to water to form an 8% non-volatile dispersion.
The blend was cathodically electrodeposited onto a steel panel at 100 volts for 2 minutes. The steel panel was then removed from the bath, - 10 washed with water, and baked at 400 for 10 minutes. A fully cured electro-deposited coating covered the panel.
~'::, .
A polymer-bis-maleimide was prepared by reacting 2 moles of . . . ~ .
succinic anhydride with 1 mole of polyoxyethylene glycol (molecular weight of 1540), which reaction product was further reacted with 2 moles of hexamethy-lene diamine. This polymer~diamine was dissolved in tetrahydrofuran (10%
` solution by weight) and then added to a solution of 2 moles of maleic : ~:
anhydride (10 % solution by weight in tetrahydrofuran) to form a polyether-.
bis-maleimide compound in the presence of acetic anhydride and of potassium acetate.
.
;s One mole of the epoxy resin of Example 4 (DER 664) was reacted at ~ ;
~, O
~, 60 C with 2 moles of the ketimine blocked diethylene triamine of Example 4 followed by further reaction with one mole of linseed oil fatty acid. This resin was completely neutralized with 4 moles of acetic acid and blended , with 50% polyether-bis-maleimide by weight of the resin. The blend was : , added to deionized water to form an 8% non-volatile dispersion. ~
... . . .
; This electrocoating composition was cathodically electrodeposited at 100 volts for 1 minute onto a steel panel. The panel was removed from the , ~'~ -11-~ .
.
10~7~39 bath, washed with water, and haked at 400 for 35 minutes. A hard, flexible, solvent resistant coating covered the panel.
EX~PLE 9 The neutralized resin of Example 8 (unsaturated oil-modified epoxy resin neutralized with acetic acid) was blended with 20% by weight of the bis-maleimide of 4,4'-methylene-bis-(ortho-chloroaniline). The blend was added to deionized water to form an 8% non-volatile dispersion.
- This electrocoating composition was cathodically electrocoated and baked in a manner similar to Example 8. A hard flexible, solvent resistant ` 10 coating covered the panel.
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~, ,''' .
."' ~
'.' . -'`:
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.,;
'~' '1 ~.
,,,:;
~.:
1 .
. :
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a heat-curable electrocoating composition containing a polymer having pendant amine groups and a cross-linking agent in an aqueous disper-sion for electrodeposition onto a cathode substrate disposed within an aqueous electrocoating bath, said polymer being cross-linkable upon subsequent heat-ing of said electrocoated cathode substrate, the improvement comprising:
said polymer having at least about 5% pendant primary or secondary amine groups, said amine groups being protonated with acid to render said polymer water dis-persible in said bath, said amine groups adapted to become deprotonated upon electrodeposition of said polymer on said cathode substrate; and at least about 5% bis-maleimide of the formula I
where R is a divalent aliphatic, aromatic or mixed aliphatic-aromatic group having a molecular weight up to about 3,000 by weight of said polymer, said bis-maleimide serving for cross-linking said polymer by addition polymeriaz-tion with said de-protonated pendant primary or secondary amine groups upon heating to form a heat-cured electrodeposited coating.
said polymer having at least about 5% pendant primary or secondary amine groups, said amine groups being protonated with acid to render said polymer water dis-persible in said bath, said amine groups adapted to become deprotonated upon electrodeposition of said polymer on said cathode substrate; and at least about 5% bis-maleimide of the formula I
where R is a divalent aliphatic, aromatic or mixed aliphatic-aromatic group having a molecular weight up to about 3,000 by weight of said polymer, said bis-maleimide serving for cross-linking said polymer by addition polymeriaz-tion with said de-protonated pendant primary or secondary amine groups upon heating to form a heat-cured electrodeposited coating.
2. In a process for electrodeposition of a heat-curable electrocoating composition containing a polymer having pendant amine groups and a cross-link-ing agent in an aqueous dispersion onto a cathode substrate disposed within an aqueous electrocoating bath, said polymer being cross-linkable upon subsequent heating of said electrocoated cathode substrate, the improvement comprising (a) providing said electrocoating composition containing (i) a polymer having at least about 5% pendant primary or secondary amine groups, said amine groups being protonated with acid to render said polymer water dispersible in said bath and (ii) at least about 5% by weight of the polymer of a bis-maleimide of for-mula I defined in claim 1, serving as a cross-linking agent for said polymer;
(b) applying an electromotive potential through said bath to electro-deposit said polymer and said cross-linking agent onto said cathode substrate, said pendant amine groups of said polymer becoming de-protonated thereby; and (c) heating said electrocoated cathode substrate, said bis-maleimide cross-linking said polymer by addition polymerization with said de-protonated pendant amine groups to form a heat-cured electrodeposited coating.
(b) applying an electromotive potential through said bath to electro-deposit said polymer and said cross-linking agent onto said cathode substrate, said pendant amine groups of said polymer becoming de-protonated thereby; and (c) heating said electrocoated cathode substrate, said bis-maleimide cross-linking said polymer by addition polymerization with said de-protonated pendant amine groups to form a heat-cured electrodeposited coating.
3. The electrodeposition process of claim 2 wherein said heating said electrocoated cathode substrate is at a temperature of at least about 100°F.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US519409A US3925181A (en) | 1974-10-31 | 1974-10-31 | Cathodic electrocoating process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1067639A true CA1067639A (en) | 1979-12-04 |
Family
ID=24068204
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA230,735A Expired CA1067639A (en) | 1974-10-31 | 1975-07-03 | Cathodic electrocoating composition and process comprising aqueous amine-substituted polymer with bismaleimide cross linking agent |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1067639A (en) |
-
1975
- 1975-07-03 CA CA230,735A patent/CA1067639A/en not_active Expired
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