CA1123980A - Water-soluble polyamideimides - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Polyamideimide base coating composition having water as a solvent constituent are provided. Amine containing material is added to the polyamideimide along with water or water and a relatively small amount of compatible organic solvent to provide a composition having good coating qualities and salutary electrical insulating and physical characteristics.

Description

~3~ 60 IN 495 'J
`~ This invention relates to-~e~ i~e~ e base coating compositions. More particularly, it relates to such coating compositions which have water as the sole or major solvent constituent.
Resinous coating compositions in the form of varnishes and enamels in which for ease of application the polymer is dissolved in compatible solvents are well known. Among the most useful coating compositions ~ /Ya~n ,d~
are those which are based on ' ~ . Polyamideimide coating compositions form flexible and durable films and are particularly useful as wire enamels~ varnishes, adhesives p~/Y~ ofe ~vn~
for laminates, paints and the like. Such ~o~amide~-mi~e base coating compositions are particularly noted for their long term high temperature capability of the order of 220C which, in addition to their other qualities, makes them particularly useful in electrical insulating applications -~
such as for maynet wire enamels. ~his is as compared to the usual polyester and polyesterimide base coating compositions which do not have such highly continuous heat resistance. Since polyamideimides have heretofore been prepared using relatively expensive organic solvents, the economic use of amideimide coatings has been inhibited.
It has been customary, for example, to use such polyamideimide compositions as overcoats over less expensive polyester or polyesterimide base coats. It would be most desirable and the high temperature characteristics of polyamideimide coating compositions would be more fully realized commercially were cheaper solvents made available. It is a primary object of this invention to provide polyamideimide coating compositions which contain relatively inexpensive solvent systems which are not only more economic but which do not produce undesirable concentrations of pollutants ~3~ 60 ~l 495 when they evaporate durin~ curiny of the resin base.
As pointed out above, polyamideimide compositions are well known, being directed w.idely in the literature and in patents such as U. S. 2,421,021 dated May 27l 1947;
3,260,691 dated July 12, 1966; 3,471,444 dated October 7, 1969; 3,518,230 dated June 30, 1970; 3,817,926 dated June 18, 1974 and 3,847,878 as well as in the foreign paten~
literature as illustrated, for example, by British patent 57018S8 .
As exemplary of the preparation of polyamideimides, there can be reacted together a carboxylic anhydirde and an organic primary amine to form an amideimide prepolymer, there being reacted with this prepolymer a polyisocyanate to produce a relatively hiyh molecular welght block polymer which in solution affords the desirable film-forming and other characteristics inherent in polamideimidesO
Any of a number of carboxylic anhydrides can be used in making polyamideimides including but not limited to the following, among others, which will occur to those skilled in the art: trimellitic anhydride; 2,6,7-naphthalene tricarboxylic anhydride' 3,3',4-diphenyl tricarboxylic anhydride; 3,3',4-benzophenone tricarboxylic anhydride;
1,3,4-cyclopentane tetracarboxylic anhydride; 2,2',3-aiphenyl tricarboxylic anhydride; diphenyl sulfone 3,3',4-tricarboxylic anhydride; diphenyl isopropylidene 3,3',4-tricarboxylic anhydride; 3,4,10-perylene tri.carboxylic anhydride;
3,4-dicarboxyphenyl 3-carboxyphenyl ether anhydride; ethylene tricarboxylic anhydride; l,2,5-naphthalene tricarboxylic anhydride, etc. The tricarboxylic acid materials can be characteri:zed by the followiny formula:

~123~ 60 IN 495 I HO-~-R C \
\C~

where R is a trlvalent organic radical.
The polyamines useful in the above connection are well known and may be expressed by the formula II X - R" ~---{NH2)n : :
where R" is an organic radical and n is at least 2 and X is hydrogen, an amino group or organic group including ..
those also containing at least one amino groupO
The polyamines useful in the above connection can also be express by the formula III R'~'- (NH2)n where R'l' is a member selected from the class consisting of oryanic radicals of at least two carbon atoms (both halogenated and unhalogenated)~including but not limited to, e.g., hydrocarbon radicals of up to 40 carbon atoms9 and groups consisting of at least two aryl residues attached to each other through the medium of a member selected from the class consisting of an alkylene radical of from 1 to 10 carbon atoms, -5-, -SO2- O , and -O-, etcO, and n is at least 2.
Among the specific useful amines, alone or in admixture, are the following:
p-xylene diamine bis(4-amino-cyclohexyl)methane hexamethylene diamine heptamethylene diamine octamethylene diamine 1 ~ 2~ 60 IN 495 nonamethylene diamine decamethylene diamine 3-methyl heptamethylene diamine 4,41-dimethylheptamethylene diamine

2,11-diamino-dodecane 1,2-bis-(3-amino-propoxy)ethane 2,2-dimethyl propylene diamine

3-methoxy-hexamethylene diamine 2,5-dimethylhexamethylene diamine 2,5-dimethylheptamethylene diamine 5-methylnonamethylene diamine 1,4-diamino-cyclo-hexane 1,12-diamino-octadecane 2,5-diamino-1,3,4-oxadiazole 2 (CH2)3O(cH2)2o(cH2)3NH2 H2N(CH2)3S(cH2)3NH2 ~2N(CH2)3N(CH3)(c~2)3NH2 meta-phenylene diamine para-phenylene diamine

4,4'-diamino-diphenyl propane 4,4'-diamino-diphenyl methane benzidine 4,4'-diamino-diphen~l sul~ide 4,4'-diamino-diphenyl sul~one 3,3'-diamino-d.iphenyl sul:Eone 4,4'-diamino-diphenyl ether 2,6-diamino-pyridine bis(4-amino-phenyl)diethyl silane bis(4-amino-phenyl)diphenyl silane bis(4-amino-phenyl)phosphine oxide 4,4'-diaminobenzophenone bis~4-amino-phenyl)-N-methylamine ^` ,~ 60 IN 495 ~3~

bls(4-aminobutyl)tetramethyldisiloxane 1,5-diaminonaphthalene 3,3'-dimethyl-4,41-diamino-biphenyl 3,3'-dimethoxy benzidine 2,4-bis(beta-amino-t butyl)toluene toluene diamine bis(para-beta-amino-t-butyl-phenyl)ether para-bis(2-methyl-4-amino-pentyl)benzene para-bis(l,l-dimethyl-5-amino-pentyl)benzene m-xylylene diamine polymethylene polyaniline Any polyisocyanate, that is, any isocyanate having two or more isocyanate groups, whether blocked or unblocked, can be used in ma};iny polyamideimides. ~locked isocyanates using as the blocking constituent phenols or alcohols, among others, can be used and in general provide a higher molecular weight final material which is advantageous as, for example, in varnishes. On the other hand, the unblocked isocyanates provide more flexible final materials. At any rate, the blocking material must be evaporated off as much as possible and there is no advantage from the purely reaction point of view to using the blocked material except as stated above. Typical of the blocked polyiso-cyanates is Mondur S wherein mixtures of 2,4- and 2,6-tolylene diisocyanate are reacted with trimethylol propane and blocked by esterification with phenol in th proportions of three moles of iosycanate, one mole of trimethylol propane, and three moles of phenol. In Mondur SH the isocyanate groups of mixed 2,4- and 2,6-toly-lene diisocyanate are blocked by es~erification with cresol. Among the specific polyisocyanates which are usefule alone or in admixture are the following:

~ 398~ 60 IN 495 tetramethylenediisocyanate hexamethylenediisocyanate 1,4-phenylenediisocyanate 1,3-phenylenediisocyanate 1,4-cyclohexylenediisocyana~e 2,4-tolylenediisocyanate 2,5-tolylenediisocyanate 2,6-tolylenediisocyanate 3,5-tolylenediisocyanate 4-chloro-1,3-phenylenediisocyanate l-methoxy-2,4-phenylenediisocyanate l-methyl-3,5-diethyl-2,6-phenylenediisocyanate 1,3,5-triethyl 2,4-phenylenedii.socyanate l-methyl-3,5-diethyl-2,4-phenylenediisocyanate l-methyl-3,5-diethyl-6-chloro-2,4 phenylenediiso-cyanate 6-methyl-2,4-diethyl-5-nitro-1,3-phenylenediiso-cyanate p-xylylenediisocyanate m-xylylenediisocyanate 4,6-dimethyl-1,3-xylylenediisocyanate 1,3-dimethyl-4,5-bis-(b-isocyanatoe-thyl)-benzene 3-(a-isocyanatoethyl~-phenylisocyanate 1-methyl-2,4-cyclohexylenediisocyanate 4,4'-biphenylenediisocyanate 3,3'-dimethyl-414l-bi.phenylenediLsocyanate 3,3'-dimethoxy-4,4'-biphenylenediisocyanate 3,3'-diethoxy-4,4-biphenylenediisocyanate 1,1-bix-(4-isocyanatophenyl)cyclohexane 4,4'-diisocyanato-diphenylether 4,4'-diisocyanato-dicyclohexylmethane 4,4'-diisocyanato-diphenylmethane ~3~ 60 IN ~95 4,~'-diisocyanato-3,3'-dimethyldiphenylmethane 4,4'-diisocyanato-3,3'-dichlorodiphenylmethane 4,4'-diisocyanato-diphenyldimethylmethane 1,5-naphthylenediisocyanate 1,4-naphthylenediisocyanate 4,4',4"-triisocyanato-triphenylmethane 2,4,4'-triisocyanato-diphenylether 2,4,6-triisocyanato-1-methyl-3,5-diethylbenzene o-tolidine-4,4'-diisocyanate m-tolidine-4,4'-diisocyanate benzophenone-4,4'-diisocyanate biuret triisocyanates polymethylenepolyphenylene lsocyanate Generally speaking, a slight molar excess of carboxylic acid anhydride and organic polyamine is heated to about 200C to 245C in an inert atmosphere and solvent as above, driving off the water formed and forming an amideimide group containing prepolymer. The polyisocyanate is then added and reacted to form a block amide-imide pre-polymer of relatively high molecular weight. It can be cured as by heating to form flexible film or coatings.
Alterna-tively, the carboxylic anhydride and organic diamine can be reacted in equimolar proportions, still providing desirable flexible films or coatings, wire enamels, paints, laminate adhesives and the like.
As taught, or example, in UO S. patent 3,817,926, up to 75 mole percent of the carboxylic anhydride can be replaced by substituted or unsubstituted aliphatic anhydride or diacid such as oxalic, maleic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic and dodecanedioic as well as unsaturated materials including maleic and fumaric materials, among others. Such acids ~23~ 60 IN ~95 can be expressed by the formula IV ~IOOC - Rl - COOH

where R' is a divalent satuxated or unsaturated aliphatic group or one containing a carbon-to-carbon double bond and having from about one to 40 carbon atoms, while the anhydrides can be expressed by o ~ ,.:
/rc V P~ /0 ' ~ `

The normal organic solvents used for such materials include cresols or cresylic acid, phenol, xylene, N-methylpyrrolidone, dimethylformamide, dimethyl sulEoxide, dimethylacetamide, and the like which not only tend to pollute the atmosphere during the curing process but which in some instances are toxic, flammable or may - cause serious chemical burns.
The above exemp]ary preparation method for polyamideimides is just that, and there are taught in the above patents and the voluminous general literature in this art including but not limited to New Linear Polymers, Lee et al, McGraw-~ill, 19~7.
In addition to avoiding costly organic .solvents which are presently used in connection with polyamideimide coating compositions, it would be most desirable to use a solvent such as water which would not only be cheaper but would be more acceptable ecologically.

3~

Those features of the invention which are believed to be novel are set forth with particularity in the claims appended hereto. The invention will, however, be better understood and further advantages and ob~ects thereof appreciated from a consideration of the following description.
Broadly speaking, in the practice of the present invention, the polamideimide such as the powdered solid is mixed with a secondary or tertiary amine or mixtures along with water as a solvent to which there may be added relatively small amounts of organic solvent in certain instances, the mixture being heated to a temperature of about 80C until a clear solution is obtained. Primary amines can also be used but are generally not reactive enough for an economic process. During the process the amine splits the imide ring of the polyamideimide.
The amines or amine group containing materials.
useful in connection with the present invention are preferably tertiary amines and include, among others, dimethylethanolamine, triethanolamine, phenylmethyle-thanolamine, butyldiethanolamine, phenyldiethanolamine, phenylethylethanolamine, methyldiethanolamines, and triethylamine. Secondary amines are also useful. The present coating compositions may be made in a wide range o~ solids contents to suit any particular application con-sistant with coating ease and capability. Generally, the solids content can range from about 10 percent to ~0 percent by weight solids or even more from a practical point of viewO
Polyamideimides which have up to about 20 percent free carboxyl groups can be used. However, free carboxyl groups are not essential to the invention.

The following examples illustrate the practice ~ 60 IN 495 oE the present invention, it being understood that they are exemplary only. All parts are by weight unless otherwise indicated.
Example 1 Ten parts oE commercial polyamideimide powder, specifically Amoco AI-10 was combined with 35 parts of water,

5 parts of N-methylpyrrolidone and 10 parts of the tertiary amine dimethylethanolamine. The mixture was heated to 80C
until a clear amber color solution was obtained. A portion of the liquid was coated on a metal panel, the coating being cured for one hour at 200C. The p~nel was bent 180 without cracking. Another panel so coated was cured at 175~C for 30 minutes and at 200C for 15 minutes to give a clear, flexible film.
Example 2 Twenty-five parts by weight of polyamideimide powder were combined with 60 parts of water, 15 parts of N-methyl-pyrrolidone and 23 parts of dimethylethanolamine. The mixturP was placed on a roller for mixing and heated to 80C
until a clear solution was obtained. This material was coated on a metal panel and cured for one hour at 135C
and then at 240 for 15 minutes. A clear, flexible film was obtained which did not crack when the panel was doubled upon itself.
Example 3 A mixture of 397 parts of 33 percent by weight solids solution of polyamldeimide and N-methylpyrrolidone was heated to 150C and 112 parts of dimethylethanolamine added thereto. The contents were cooled to 100C and 487 parts of water added. The resulting solution was clear and had a solids content of 25.3 percent with a viscosity of 1430 centistokes at 25C. This wire enamel solution was applied to 18 ~WG copper wire using seven passes to produce a 3.0 mil film buildwp. The enamel was cured in a 15 foot high gasfired oven, the running speed being 50 ft. per minutes with a top oven temperature of 480C
and a bottom -temperature of 270C. The resulting magnet wire had a cut-through of 325C and otherwise acceptable characteristics.
Example 4 . . .
A 33 percent solutlon of polyamideimide in the amount o~ 397 parts was heated to 150C and 50 parts of di-N-butylamine added thereto. The contents were stirred and allowed to cool to 100C and 107 parts of water were added. The resulting clear solution had a solids content of 27.1 percent and a ViSCQSity of Z-5.
When this material was cured on aluminum at 100C for 10 minutes and 160C for 10 minutes and finally at 20QC
for 30 minutes, the resulting film was clear and did not fail during a 90 crease.
Example 5 A container was charged with 10 parts of polyamideimide powder, there being added thereto 13.5 parts of dimethylethanolamine and 76.5 parts of water. The material was heated to 90C with stirring to give a clear, viscous solution. When a portion of the above solution was cured on an aluminum substrate for one hour at 200C, a flexible film was ohtained.
There are provided by the present invention polyamideimide base coating compositions which are characterized by good coating characteristics and parti-cularly by their increased cut through temperature. In addition, such materials are partially or wholly soluble in water, representing a saving in solvent cost as well ~12~

as being ecologically acceptable. While the materials are particularly useful as magnet wire enamels and as varnishes, they can also be used Eor preparing laminates of layered materials, composites of :Eibers, powders, varnishes and the like and for coating purposes in general.

~ 12 -

Claims (6)

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

1. The process of preparing a soluble cleaved polyamideimide containing coating composition excluding polyesteramidesimides, per se, which comprises reacting said polyamideimide with a tertiary amine to cleave at least part of the imide rings in a solvent containing water as a major constituent, said reacting being continued until a clear solution is obtained, wherein the quantity of said tertiary amine is more than sufficient to neutralize any free carboxyl groups present in said polyamideimide.

2. An aqueous polyamideimide coating composition prepared by means of the process of claim 1.

3. A coating composition as in claim 2 wherein water and said tertiary amine is the sole solvent.

4. A coating composition as in claim 2 in which said cleaved polyamideimide contains essentially no free carboxyl groups.

5. A coating composition as in claim 2 wherein said polyamideimide before being cleaved contains free carboxyl groups.

6. A coating composition as in claim 2 wherein said tertiary amine is dimethylethanolamine.