GB1560869A - Amide-acid and imide polyenes - Google Patents

Description

(54) AMIDE-ACID AND IMIDE POLYENES (71) We, W. R. GRACE & CO., a Corporation organized and existing under the laws of the State of Connecticut, United States of America, of Grace Plaza, 1114 Avenue of the Americas, New York, New York 10036, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to new "polyene" compounds, their preparation and curable and polymerisation compositions containing them, particularly for use as coating compositions and especially for coating wire.

It is known that polyenes (compounds having 2 or more pendant or terminal carbon to carbon unsaturated groups per average molecule) are curable by polythiols (compounds having 2 or more -SH groups per average molecule) in the presence of free radical generators, e.g. actinic radiation, to solid polythioethercontaining resinous or elastomeric products. See e.g. our United States Patent No.

3,661,744. However, known polyene-polythiol compositions give a cured product which lacks adequate properties. For example, in the wire coating field compositions containing commercially available polyenes fail the NEMA (the United States National Electric Manufacturers Association) specified heat-shock and cut-through tests at the upper temperature limits at which these tests are run.

These compositions are therefore of no practical use for wire-coating. It has therefore been a problem that a polyene-polythiol composition, which gives a cured polymeric material having good high temperature properties, is not yet available.

The present invention is derived from the idea of trying to alter the properties of the cured product by use of a different type of polyene. The commercially available polyenes have had a predominantly aliphatic molecular structure. We have now found that certain polyenes of completely different molecular structure can impart better high temperature properties to the polythioether (cured polyenepolythiol composition).

The polyenes of the present invention are amide-acid and imide polyenes having the general formula:

wherein R represents a divalent organic group having at least 2 carbon atoms which is a residue of a diamine of formula NH2-R-NH2 and the nitrogen atoms shown are attached to different carbon atoms of the R group; R' represents an aromatic ring comprising group (a group comprising one or more aromatic rings), and at least the pairs of carbonyl groups (a,a) and (b,b) are bonded to pairs of adjacent aromatic ring carbon atoms of the R' group; Z and Z' represent a hydrogen atom and a hydroxyl group respectively, or Z and Z' together represent a single bond between the nitrogen atom and carbon atom to which they are respectively attached, thereby completing a cyclic imide group; A represents an alkylene group having from 1 to 10 carbon atoms; Y represents a group of formula -CR"-CH2,

in which RP represents a hydrogen atom or a methyl group; k and h are 0 or 1; m and d are 1 to 10 and p is 0 to 10, but can only be a positive number when h and k are each 1; and the arrowed bonds indicate "e" denote positional isomerism between substituents bonded by pairs of adjacent arrows.

The amide acid polyenes of the invention have the general formula:

wherein all symbols are as defined above. They are convertible upon heating into imide polyenes of the invention having the general formula:

wherein all symbols are as defined above.

Preferred amide-acid and imide polyenes of the invention include those wherein R' represents a group of formula:

and h and k are 1 or a group of formula:

in which the left-hand bond is present in the 4- or 5-position in each individual R' group and h and k are 0.

R is preferably a hydantoin ring-containing group of formula:

a m-phenylene group, and m-xylylene group or a 4,4'-diaminodiphenylmethane group.

The excellent high temperature properties of cured olyene polythiol compositions are produced by the imidization reaction, i.e. by effecting cyclisation between the -NH- group and its neighbouring acid group, e.g. by heating. This reaction can be carried out on the amide-acid polyene, before it is mixed with a polythiol, on the composition containing the amide-acid polyene and polythiol before it is cured or during curing or on the polythioether, i.e. after curing.

Consequently, the amide-acid polyenes are highly useful precursors of the imide polyenes for the purpose of this invention.

All the polyenes of the invention, whether amide-acid or imide type, can be cured by reaction with a polythiol. For best results a photocuring rate accelerator will usually be required. Accordingly the present invention provldes specifically a photocurable composition comprising a polyene of the invention, a polythiol, and a photoinitiator (photo curing rate accelerator). Of course, each said ingredient may consist of one or more different polyenes, polythiols or photoinitiators respectively.

The total number of "ene" groups in the polyene molecule, i.e. the sum of all "m" values in the above formulae, plus the total number of thiol (-SH) groups in the polythiol molecule, must be greater than 4. The molar ratio of ene to thiol groups is usually from 0.2:1 to 8:1.

The polyenes of the invention which are acrylate or methacrylate-terminated. i.e. in which Y in the formula invention a group of formula

(R" = hydrogen or methyl), are self-polymerisable, i.e. form a polymeric material without curing with a polythiol. Thus, such polyenes, whether imidized or of the amide-acid type, are photopolymerizable per se by U.V. light, preferably in the presence of a photoinitiator (photopolymerisation rate accelerator).

The invention includes also a process of forming a solid cured polythioether, which comprises exposing a polyene-polythiol composition, as defined above, to the action of a free radical generator, preferably ultra-violet light. It also includes a process of forming an addition polymer by exposing an acrylate or methacrylateterminated polyene of the invention, if necessary together with a photoinitiator, to the action of a free radical generator, preferably also ultra-violet light. These processes can, of course, be carried out in situ on a substrate, such as an electrical conductor, to provide a coating. They are of particular value for coating wire (which term also includes a cable of more than one wire), by a process in which the wire is coated with the curable or polymerisable composition, the thickness of the coating of the uncured or unpolymerised composition is adjusted by passing the wire through a die,and the coating is then exposed to the free radical generator, e.g. ultra-violet light, to effect curing or polymerisation. Coating can be effected by immersing the wire in a bath of the composition or by feeding the wire through an extruder to which the curable or polymerisable composition is also fed and extruding the composition onto the wire.

Further, in accordance with the present invention there are provided methods of preparing an amide-acid polyene which comprises reacting, in substantially stoichiometric amounts, in an inert atmosphere and under substantially anhydrous conditions, (1) at least one primary diamine having the structure formula: N2N-R-NH2 wherein R is a divalent organic group containing at least 2 carbon atoms, the two amino groups of said diamine being attached to separate carbon atoms of said divalent organic R group with (2) at least one anhydride-containing member of the group consisting of

wherein R' and the carbonyl groups bonded thereto are as defined above and X is a halide radical and (3) an ethylenically unsaturated alcohol of the formula: HA+(Y)m wherein A is an alkylene group having from 1 to 10 carbon atoms; Y is a member of the group consisting of -CR"=CH2, OCH2)d-CR=CH2,

R" is hydrogen or methyl; and m and d are 1 to 10.

If desired, when using a dianhydride, a polyamide acid structure containing up to 10 repeating units can be obtained by reacting sufficient diamine with the dianhydride prior to reacting the thus formed polymer with the ethylenically unsaturated alcohol.

The procedure for forming the amide-acid from the primary diamine and the anhydride-containing member is well known and conventional. That is, the amideacid is prepared by mixing at least one primary diamine with at least one anhydridecontaining member, preferably in a liquid which is an inert organic solvent for at least the product and preferably also a solvent for one reactant, under substantially anhydrous conditions, for a time preferably of at least 2 minutes and at a temperature not higher than 180"C to provide at least 70% of the corresponding amide-acid. It should be understood that it is not necessary that the resultant product be totally amide-acid but that is desirable that the product contain not more than 30% by weight of imide, the remainder being the amide-acid. Thus, the aforementioned conventional process for preparing amide-acid should be conducted ordinarily at a temperature of from 20 to 1000C, and always low enough to prevent complete conversion to imide by a cyclic imide-forming reaction of the -NH- and neighbouring acid group of the amide-acid polyene. Usually a temperature below 500C will provide substantially 100% by weight of the amideacids, but higher temperatures will still provide a product containing substantial amounts of the amide-acid.

The inert atmosphere for the above-described reactions can be provided by an inert gas (e.g. nitrogen, argon or helium) blanket. Additionally, all the reactions for synthesis of the amide-acid are preferably carried out in the presence of a solvent.

The solvents useful for synthesizing the polyenes of the instant invention are organic solvents which do not chemically react with either of the reactants (the diamines or the dianhydrides) or the final amide-acid product. Additionally, besides being inert to the reaction system and being a solvent for the product, the organic solvent should be a solvent for at least one of the reactants and, preferably, for both of the reactants. The normally liquid organic solvents of the N,N-dialkylcarboxylamide class are useful as solvents in the process of the instant invention.

Preferred solvents are low molecular weight members of this class, particularly N,N-dimethylformamide and N,N-dimethylacetamide. The solvents are readily removed from the amide-acid by evaporation, displacement or diffusion. Other useful solvents include, but are not limited to, N,N-diethylformamide; N,Ndiethylacetamide; N,N-dimethylmethoxyacetamide; N-methl caprolactam; dimethylsulfoxide; N-methyl-2-pyrrolidone; tetramethylene urea; pyridine; dimethylsulfone; hexamethylphosphoramide; tetramethylenesulfone; formamide; N-methylformamide; N-acetyl-2-pyrrolidone; and the like. The solvents can be used alone, in a combination of the aforesaid solvents or in combination with poorer solvents such as toluene, benzonitrile, dioxane, butyrolactone, xylene, chlorobenzene and cyclohexane.

More specifically, the reaction conditions for forming the various polyenes depending on which anhydride-containing member is employed are as follows.

To form the dianhydride amide-acid from a dianhydride and a diamine, each reactant is put into solution prior to mixing together. The admixture during reaction is maintained at a temperature in the range from 25 up to preferably below 100"C. Preferably, the diamine is added to the dianhydride but the reaction is operable if the sequence is reversed. In either sequence, the reactants are added to each other slowly to restrict the formation of very high molecular weight polymers. The mole ratio of the dianhydride to the diamine is 2:1 for monomeric amide-acids. A mole ratio of 1:1 can be employed should polyamide-acid be desired. Any mole ratio between these ratios is operational. The amide-acid polyene is formed by adding an unsaturated alcohol which can be, but need not be, in solution prior to its addition. The reaction is carried out at temperatures between room temperature and below 100"C, preferably 60--80"C for periods ranging from 2 minutes to 3 hours. The resultant product is worked up by repeatedly washing the reaction mixture with a large excess of water while vigorously agitating the mixture.

The water layer is discarded and the resulting viscous gum is then dried by dissolving it in an alcohol/benzene azeotropic mixture and azeotroping off the water. The azeotropic solvent used alone or as a mixture of solvents can be of any kind as long as it dissolves the gum and has an azeotropic boiling point below about 100"C.

To form a dicarboxylic amide-acid from a diamine and an acid anhydride, the reaction can be carried out in the presence or absence of the aforementioned solvent. If no solvent is used, the reactants are mixed in the flask and the flask is heated until the reactants react vigorously at a temperature ranging from 250C up to 1800C, preferably 150--175"C. If a solvent is employed, the diamine solution is preferably added to the anhydride but the reverse of the sequence is operable. The teperature range of the reaction when a solvent is employed is usually between 25"C to 100"C. The dicarboxylic acid amide-acid solution is vigorously washed with water and the resulting viscous gum is then dried by dissolving it into an alcohol/benzene azeotropic mixture and azeotroping off the water. To form the amide-acid polyene from this amide-acid, a conventional esterification reaction is performed. The unsaturated alcohol can act as a solvent per se or additional solvents such as benzene, toluene, isopropyl alcohoUbenzene can be employed. A catalyst such as those well known in the esterification art, e.g. p-toluene sulfonic acid, methane sulfonic acid, sulfuric acid, phosphoric acid, hydrochloric acid, BE*3- etherate, camphor sulfonic acid, organic tin compounds, and the like, may be employed. The solvent and/or unreacted alcohol is stripped off to recover the amide-acid polyene product. With these reactants it is desirable and oftentimes preferable to esterify the acid anhydride with the unsaturated alcohol firstly in the absence of a solvent at a temperature in the range of 100-255 C and thereafter react the anhydride groups with the diamine also in the absence of a solvent at a temperature in the range of 6O-l900C.

When the anhydride-containing member is an anhydride acid halide, it is preferable to form a product comprising monoester anhydride from the reaction of the anhydride acid halide and the unsaturated alcohol, remove the hydrogen halide thereby liberated and then react the product comprising monoester anhydride with the diamine. Preferred details are as follows. The ester anhydride is formed by putting the anhydride acid halide in solution prior to admixing same with the unsaturated alcohol. The reactants are added in a mole ratio of approximately 1:1.

The unsaturated alcohol is added slowly to the anhydride acid halide while the reaction solution is sparged vigorously with a dry inert gas (e.g. nitrogen, argon or helium) to remove the hydrogen halide. The reaction is carried out at slightly below, preferably 10 C below, refluxing temperature. After the addition of all the alcohol is complete, the reaction is continued until all the hydrogen halide has been removed. The diamine with or without a solvent is added to the ester anhydride (at a diamine to anhydride ratio of 1:2) while maintaining the reaction mixture in a range between 25 to about 100 C, preferably between 50 and 80 C, until the IR absorption bands of the anhydride carbonyl groups disappear. The amide-acid polyene product is recovered by distilling off the solvent at low pressure using a temperature of preferably not greater than 100 C.

The diamines operable in the instant invention are primary diamines having the structural formula H2N-R-NH2 wherein R is a divalent organic group, normally derived from or containing an aromatic, aliphatic, cycloaliphatic, heterocvclic or a combination of aromatic and aliphatic groups, containing at least 2 carbon atoms, the 2 airri groups said dhanune are each attw cEied to separate carbon atoms of said divalent organic group. Diamines which are operable in the instant invention include, but are not limited to, 4,4'-diamino-diphenylmethane; benzidine; 3,3'-dichlorobenzidine; 4,4'-diamino-diphenyl sulfide; 3,3'-diamino diphenyl sulfone; 4,4'-diamino-diphenyl sulfone; 4,4'-diamino-diphenyl ether; 1,5 diamino naphthalene; meta-phenylenediamine; 4,4'-diamino-diphenyl propane; para-phenylene-diamine; 3,3 '-dimethyl-4,4'-biphenyl diamine; 3,3 '-dimethoxy benzidine; 2,4-bis(beta-amino-t-butyl)toluene; bis-(para-beta-amino-t-butyl- phenyl) ether' bis-(para-beta-methyl-delta-amino-penty )benzene; bis-para(l,l- dimethyl-5-amino-pentyl)benzene; 1-isopropyl-2,4-metaphenylene diamine; xylylene diamine; p-xylylene diamine; di(para-amino-cyclohexyl)methane; hexamethylene diamine; hepta-methylene diamine; octa-methylene diamine, nonamethlene diamine, decamethylene diamine; 3-aminomethyl-3 ,5 ,S4rimethyl- cyclohexyl amine; 3-methylheptamethylene diamine; 4,4-dimethylheptamethylene diamine; 2,11 -diaminododecane; 1,2-bis-(3-aminopropoxy ethane); 2,2-dimethyl propylene diamine; 3-methoxy-hexamethylene diamine; 2,5-dimethyl hexamethylene diamine; 2,5-dimethylheptamethylenediamine; 3-methylhepta methylene diamine; 5-methylnonamethylenediamine; 2,17-diamino-eicosadecane; 1 ,4-diamino-cyclohexane; 1,10-diamino-1,10-dimethyldecane; 1,1 2-diamino- octadecane; 2,4 toluene diamine; 2,6 toluene diamine; 1,3 bis(aminomethyl)cydohexane; N,N'-bis (3-aminopropyl) dimethyl hydantoin; H2NH2N(CH2) O(CH2)2O(CH2)3NH2; H2N(CA2)3S(CH2)3NH H2N(CH2)3N(CH3XCH2)3NH2 and mixtures thereof.

The anhydride-containing member useful for forming polyenes in the present invention preferably has the formula:

wherein R' is an aromatic residue attached to at least 3 carboxyl groups at least two of which groups are attached to adjacent carbon atoms on the aromatic residue and X is a halide radical. Anhydride-containing members operable in the instant invention to form amide-acid polyenes include, but are not limited to, pyromellitic dianhydride; 2,3,6,7-naphthalene tetracarboxylic dianhydride; 3,3',4,4'-diphenyl tetracarboxylic dianhydride; 1,2,5,6-naphthalene tetracarboxylic dianhydride; 2,2',3,3'-diphenyltetracarboxylic dianhydride; 2,2-bis(3,4-dicarboxyphenyl)- propane dianhydride; bis(3,4-dicarboxyphenyl)sulfone dianhydride; perylene 3,4,9,1 0-tetracarboxylic acid dianhydride; bis(3 ,4-dicarboxyphenyl)ether dianhydride; bis(3 ,4-dicarboxyphenyl)sulfone dianhydride, ethylene tetracarboxylic acid dianhydride; trimellitic anhydride acid halide, e.g. trimellitic an hydride acid chloride benzophenonetetracarboxylic anhydride; trimellitic anhydride and the like.

Ethylenically unsaturated alcohols suitable for use in the instant invention for form amide-acid polyenes are those of the formula: HO+A4(Y)m wherein A is an alkylene group having from 1 to 10 carbon atoms; Y is a member of the group consisting of -CR"=CH2, CH2)d-CR=CH2,

R" is hydrogen or methyl; and m and d are 1 to 10.

Illustrative of the operable reactive unsaturated alcohols which react with the amide-acid to give the desired polyene include, but are not limited to, allyl and methallyl alcohol, crotyl alcohol, w-undecylenyl alcohol, 2-vinyloxyethanol, vinylhydroxyethyl sulfide, propargyl alcohol, I-allylcyclopentanol, 2-methyl-3butene-2-ol, diallyl malate and hydroxyl-substituted oranic ester of acrylic acid or methacrylic acid including, but not limited to, 2-hydroxyethyl acrylate, I (or 2) hydroxy propyl acrylate, 1 (or 2) hydroxybutyl acrylate and the corresponding methacrylates thereof. Reactive unsaturated derivatives of polyhydric alcohols such as glycols, triols, tetraols, are also suitable. Representative examples include trimethylolpropane or trimethylolethane diallyl ethers, pentaerythritol triallyl ether and the like. Mixtures of various reactive unsaturated alcohols are operable as well.

Additionally, a suitable ethylenically unsaturated alcohol can be prepared by reacting one mole of a polyvinyl alcohol containing 10 hydroxyl groups with 9 moles of allyl chloride to obtain an alcohol having 9 ethylenically unsaturated sites.

The amide-acid polyenes of the present invention can be imidized per se by heating the polyene, at a temperature which will usually fall within the range 50250 C. Heating periods at the low end of the temperature range are necessarily of longer duration than those at the high end of the range to effect imidization.

The polyenes of the present invention can also be imidized and cured in combination with a polythiol in the presence of a free radical generating agent. In some instances the polyene/polythiol composition is cured by adding a photosensitizer to the composition and exposing to U.V. radiation followed bv heating to effect imidization. In other instances the same formulation is heated first to cause imidization and, thereafter, subjected to U.V. radiation to effect curing.

Additionally, both imidization and curing can be effected in one step by adding a chemical free radical generating agent, e.g. benzpinacol, to the polyene/polythiol composition, and, thereafter, heating to effect both imidization and curing.

Additionally, the polyene per se can be imidized by heating and, the resulting imide-containing polyene admixed with a polythiol and photosensitizer for U.V. curing. In all these various processes it will usually be necessary to heat the composition to a temperature in the 50 to 250"C range to effect imidization.

However the invention also includes a process in which a polyene-polythiol composition, wherein the polyene component comprises an amide-acid polyene, is merely exposed under ambient conditions to a free radical generator to form a solidified cured imide-containing polythioether. All these processes can be applied to the in situ coating of a substrate but the preferred process is to coat the substrate with a composition comprising an imide-polyene and a polythiol and to expose the coated composition to the action of a free radical generator, such as U.V. radiation.

A "polythiol" is a simple or complex organic compound having a multiplicity (2 or more) pendant or terminally positionedSH functional groups per average molecule.

Ordinarily the polythiol will have a viscosity up to 20 million centipoises (cps) at 70"C as measured by a Brookfield Viscometer either alone or when in the presence of an inert solvent, aqueous dispersion or plasticiser. Operable polythiols in the present invention usually have molecular weights in the range 94 to 20,000, and preferably from 100 to 10,000.

The polythiols operable in the present invention may be exemplified by the general formula R & SH)n where n is at least 2 and R8 is a polyvalent organic group.

Thus Ra may contain cyclic groupings and hetero atoms such as N, P or 0 and primarily contains carbon-carbon, carbon-hydrogen, carbon-oxygen, or silicon oxygen containing chain linkages.

One class of polythiols operable with polyenes to obtain essentially odorless polythioether products are esters of thiol-containing acids of the formula HS-R9-COOH where R9 is an organic group with polyhydroxy compounds of structure Rro+OH)n where R10 is an organic group and n is 2 or greater. These components will react under suitable conditions to give a polythiol having the general structure:

where R9 and R10 are organic groups and n is 2 or greater.

Certain polythiols such as the aliphatic monomeric polythiols (ethane dithiol, hexamethylene dithiol, decamethylene dithiol or tolylene-2,4-dithiol, and some polymeric polythiols such as a thiol-terminated ethylcyclohexyl dimercaptan polymer, and similar polythiols which are conveniently and ordinarily synthesized on a commercial basis, although having obnoxious odors, are operable in this invention but many of the end products are not widely accepted from a practical, commercial point of view. Examples of the polythiol compounds preferred for this invention because of their relatively low odor level include but are not limited to esters of thioglycolic acid (HSCH2COOH), a-mercaptopropionic acid (HS-CH(CH3)-COOH and p-mercaptopropionic acid (HS-CH2CH2COOH) with polyhydroxy compounds such as glycols, triols, tetraols, pentaols or hexaols.

Specific examples of the preferred polythiols include but are not limited to ethylene glycol bis(thioglycolate), ethylene glycol bis(P-mercaptopropionate), trimethylolpropane tris(thioglycolate), trimethylolpropane tris(p-mercapto- propionate), pentaerythritol tetrakis (thioglycolate) and pentaerythritol tetrakis(fi- mercaptopropionate), all of which are commercially available. A specific example of a preferred polymeric polythiol is polypropylene ether glycol bis(p-mercapto- propionate) which is prepared from polypropylene-ether glycol (e.g. Pluracol P2010, Wyandotte Chemical Corp.) and p-mercaptopropionic acid by esterification. "Pluracol" is a Registered Trade Mark.

The preferred polythiol compounds are characterized by a low level of mercaptan-like odor initially, and after reaction, give essentially odorless polythioether end products which are commercially attractive and practically useful resins or elastomers for both indoor and outdoor applications.

Prior to curing, the photocurable polymer may be formulated for use as 100, solids, or disposed in organic solvents, or as solutions, dispersions or emulsions in aqueous media.

The photocurable polymer compositions prior to curing may readily be pumped, poured, syphoned, brushed, sprayed, doctored, or otherwise handled as desired. Following application, curing in place to a solid resin or elastomer may be effected either very rapidly or extremely slowly as desired by manipulation of the compounding ingredients and the method of curling.

To obtain the maximum strength, solvent resistance, creep resistance, heat resistance and freedom from tackiness, the reactive components consisting of the polyenes and polythiols are formulated in such a manner as to given solid, crosslinked, three dimensional network polythioether polymer systems on curing.

In order to achieve such infinite network formation, the individual polyenes and polythiols must each have a functionality of at least 2 and the sum of the functionalities of the polyene and polythiol components must always be greater than 4. Blends and mixtures of various polyenes and various polythiols containing said functionality are also operable herein.

Functionality as used herein refers to the average number of ene or thiol groups per molecule in the polyene or polythiol, respectively. For example, a triene is a polyene with an average of three reactive carbon to carbon unsaturated groups per molecule, and thus has a functionality (f) of three. A dithiol is a polythiol with an average of two thiol groups per molecule and thus has a functionality (f) of two.

The term "reactive unsaturated carbon to carbon groups" means groups which will react under proper conditions as set forth herein with thiol groups to yi weight of the polyene-polythiol curable compositions and preferably 0.005-300 parts on the same basis.

The polythioether-forming components and compositions, prior to curing, may be admixed with or blended with reactive diluents, other monomeric materials (including, of course, other types of polyene) and polymeric materials such as thermoplastic resins, elastomers or thermosetting resin monomeric or polymeric compositions.

Non-limiting reactive diluents operable herein include ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, trimethylol propane triacrylate, trimethylol propane trimethacrylate, pentaerythritol tetracrylate, pentaerythritol tetramethyacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, pentaerythritol triacrylate, neopentyl glycol diacrylate and mixtures thereof. The resulting blend may be subjected to conditions for curing or co-curing of the various components of the blend to give cured products having unusual physical properties.

Although the mechanism of the curing reaction is not completely understood, it appears most likely that the curing reaction may be initiated by most any free radical generating source which dissociates or abstracts a hydrogen atom from an SH group, or accomplishes the equivalent thereof. Generally, the rate of the curing reaction may be increased by increasing the temperature of the composition at the time of initiation of cure. In most applications, however, the curing is accomplished conveniently and economically by operating at ordinarily room temperature conditions.

Operable curing initiators or accelerators include radiation such as actinic radiation, e.g. ultraviolet light, lasers; ionizing radiation such as gamma radiation, x-rays, corona discharge, as well as chemical free radical generating compounds such as azo, peroxidic, compounds.

Azo or peroxidic compounds (with or without amine accelerators) which decompose at ambient conditions are operable as free radical generating agents capable of accelerating the curing reaction include benzoyl peroxide, di-t-butyl peroxide, cyclohexanone peroxide with dimethyl aniline or cobalt naphthenate as an accelerator; hydroperoxides such as hydrogen peroxide, cumene hydroperoxide, t-butyl hydroperoxides; peracid compounds such as tbutylperbenzoate, peracetic acid; persulphates, e.g. ammonium persulphate; azo compounds such as azo-bis-isobutyronitrile and the like.

These free radical generating agents are usually added in amounts ranging from about 0.001 to 10 percent by weight of the curable solid polyene-polythiol composition, preferably .01 to 5 percent.

Additionally, substituted or unsubstituted pinacols or certain derivatives thereof, e.g. as U.S. Patent No. 4,020,233, are also operable as free radical generators to form imide-containing cured polythioethers. That is, the amide-acid polyene, polythiol and pinacol can be heated to form an imide-containing, solid, cured polythioether, thereby effecting simultaneously the steps of exposure to the free radical generator and heating to yield an imide.

The substituted or unsubstituted pinacols or derivatives thereof operable herein have the general formula:

wherein R, and R3 are the same or different substituted or unsubstituted aromatic radicals, R2 and R4 are substituted or unsubstituted aliphatic or aromatic radicals and X and Y which may be the same or different are hydroxyl, alkoxy or aryloxy.

Preferred pinacols are those wherein R1, R2, R3, and R4 are aromatic radicals, especially phenyl radical and X and Y are hydroxyl.

Examples of this class of compounds include but are not limited to benzopinacol, 4,4'-dichlorobenzopinacol, 4,4'-dibromobenzopinacol, 4,4'-diiodobenzopinacol, 4,4',4",4"'-tetrachlorobenzopinacol, 2,42',4'-tetrachlorobenzo- pinacol. 4,4'-dimethylbenzopinacol, 3, 3'-dimethylbenzopinacol, 2,2'-dimethylbenzopinacol, 3,4-3',4'-tetramethyIbenzopinacol, 4,4'-dimethoxybenzopinacol, 4,4',4",4"'-tetramethoxybenzopinacol, 4,4'-diphenylbenzopinacol, 4,4'-dichloro-4", 4"'-dimethylbenzopinacol, 4,4'-dimethyl-4",4"'-diphenylbenzopinacol, xanthonpinacol, fluorenonepinacol, acetophenonepinacol, 4,4'-dimethylacetophenone-pinacol, 4,4'-dichloroacetophenonepinacol, 1,1 ,2-triphenyl-propane-l 1,2- diol, 1,2,3,4-tetraphenylbutane-2,3-diol, 1,2-diphenylcyclobutane-1,2-diol, propiophenone-pinacol, 4,4'-dimethylpropiophenone-pinacol, 2, 2'-ethyl-3 ,3 'dimethoxypropiophenone-pinacol, 1,1,1 ,4,4,4-hexafluoro-2,3-diphenyl-butane-2,3- diol.

As further compounds according to the present invention, there may be mentioned: benzopinacol-mono methylether, benzopinacol-mono-phenylether, benzopinacol monoisopropyl ether, benzopinacol monoisobutyl ether, benzopinacol mono(diethoxy methyl)ether and the like.

The pinacol can be added to the composition most suitably in amounts ranging from 0.015%, preferably 0.13%, by weight based on the weight of the ethylenically unsaturated compound and the polythiol.

The curing period may be retarded or accelerated from less than 1 minute to 30 days or more.

Conventional curing inhibitors or retarders which may be used in order to stabilize the components or curable compositions so as to prevent premature onset of curing may include hydroquinone; p-tert-butyl catechol; 2,6-di-tert-butyl-pmethylphenol; phenothiazine; N-phenyl-2-naphthylamine; phosphorous acid; or pyrogallol.

The preferred free radical generator for the curing reaction is radiation.

The curing reaction can be initiated by radiation having an energy greater than 3 electron volts, i.e. either U.V. radiation or high energy ionizing radiation. The U.V. radiation can be obtained from sunlight or special light sources which emit significant amounts of U.V. light having a wavelength in the range of about 2,000 to about 4,000 Angstrom units. Any type of U.V. light from any source may be used in carrying out the method of this invention. For liquid photocurable compositions, it is preferred that the light emanate from a point source or in the form of parallel rays, but divergent beams are also operable as a source of radiation.

Various light sources may be used to obtain sufficient U.V. radiation to practice the method of this invention. Such sources include carbon arcs, mercury arcs, fluorescent lamps with special ultraviolet light emitting phosphors, xenon arcs, sunlight, tungsten halide lamps, argon glow lamps, photographic flood lamps, lasers and the like.

When U.V. radiation is used for curing, a photoinitiator is added to the composition to increase the curing rate.

Various photoinitiators, i.e. photocuring rate accelerators, are operable and well known to those skilled in the art. Examples of photoinitiators include, but are not limited to, benzophenone, o-methoxybenzophenone, acetophenone, omethoxyacetophenone, acenaphthalene-quinone, methyl ethyl ketone, valerophenone, hexanephenone, y-phenylbutyrophenone, p-morpholinopropiophenone, dibenzosuberone, 4-morpholinobenzophenone, benzoin, benzoin methyl ether, 4'-morpholinodeoxybenzoin, p - diacetlbenzene, 4,- aminobenzophenone, 4' - methoxyacetophenone, benzadehyde, b - methoxybenzaldehyde, y - tetralone, 9 - acetylphenanthrene, 2 - acetylphenanthrene, 10thioxanthenone, 3-acetylphenanthrene, 3-acetylindole, 9-fluorenone, I-indanone, 1,3,5-triacetylbenzene, thioxanthen-9-one, xanthene-9-one, 7-Hbenz[de] anthracen-7-one, I-naphthaldehyde, benzoin tetrahydropyranyl ether, 4,4'-bis(dimethylamino)benzophenone, fluorene-9-one, 1 '-acetonaphthone, 2'acetonaphthone, triphenylphosphine, tri-o-tolylphosphine, acetonaphthone and 2,3-butanedione, benz[ajanthracene, 7,12 dione, 2,2-dimethoxy-2-phenylacetone, diethoxyacetophenone, dibutoxyacetophenone, which serve to give greatly reduced exposure times and thereby. when used in conjunction with various forms of energetic radiation, yield very rapid, commercially practical time cycles by the practice of the present invention.

These photocuring rate accelerators may range from about 0.005 to 50 percent by weight of the photocurable polyene-polythiol composition, preferably 0.05 to 25 percent.

The mole ratio of the ene/thiol groups for preparing the curable composition is usually 0.2/1.0 to 8/1.0, and preferably from 0.5/1.0 to about 2/1.0 group ratio.

The radiation-curable compositions of the present invention can also be cured by high energy ionizing irradiation. A preferred feature of the ionizing irradiation operation of the present invention is treatment with high energy particle irradiation or by gamma-rays or X-rays. Irradiation employing particles in the present invention includes the use of positive ions (e.g. protons, alpha particles and deuterons), electrons or neutrons. The charged particles may be accelerated to high speeds by means of various voltage gradient mechanisms such as a Van de Graaff generator, a cyclotron, a Cockroft Walton accelerator, a resonant cavity accelerator, a betatron, a G. E. resonant transformer, a synchroton or the like.

Furthermore, particle irradiation may also be supplied from radioactive isotopes or an atomic pile. Gamma rays or X-rays may be obtained from radio-isotopes (e.g. cobalt 60) or by particle bombardment of suitable target material (e.g. high energy electrons on a gold metal target).

The dose rate for the irradiation operable to cure the coating in the present invention is in the range 0.00001 to 1,000 megarads/second.

The amount of ionizing radiation which is employed in curing the radiation curable material in the present invention can vary between broad limits. Radiation dosages of less than a megarad up to 10 megarads or more for electrons are operable, preferably 0.02 to 5 megarads energy absorbed are employed. For gamma-rays or X-rays, radiation dosages in the range 0.0001 to 5.0 megarads energy absorbed are operable. the irradiation step is ordinarily performed under ambient temperature conditions but can be performed at temperatures ranging from below room temperature up to temperatures of 90"C.

When using ionizing radiation, the depth of penetration is dependent upon the density of the material to be penetrated. If such penetration is not sufficient to cure the coating to the entire depth desired when beaming the radiation from one direction only, one may use multiple radiation sources beaming simultaneously or intermittently from diametrically opposite sides of the coating. Furthermore, shielding can also be employed to increase penetration of the coating on the opposite side away from the radiation source.

The curable amide-acid polyene or imide polyene and polythiol compositions can be used in preparing solid, cured crosslinked insoluble polythioether polymeric products having many and varied uses, examples of which include, but are not limited to, coatings; adhesives; films; molded articles; imaged surfaces, e.g. photoresists; printing plates; e.g. offset, lithographic, letterpress, gravure, silverless photographic materials and the like.

Since the cured materials formed from the polyene-polythiol composition possess various desirable properties such as resistance to severe chemical and physical environments and have good high temperature properties on imidization, they are particularly useful for preparing coatings.

A general method for preparing coatings comprises coating the curable composition on a solid surface of a substrate such as plastic, rubber, glass, ceramic, metal, paper and the like; exposing directly to radiation, e.g., U.V. light until the curable composition cures and crosslinks in the exposed areas. The resulting products are cured coatings on suitable substrates or supports.

In forming the composition comprised of the polythiol and the polyene, it is desirable that the photocurable composition contain a photocuring rate accelerator from about 0.005 to 50 parts by weight based on 100 parts by weight of the aforementioned polyene and polythiol.

It is to be understood, however, that when energy sources, e.g. ionizing radiation, other than visible or ultraviolet light, are used to initiate the curing reaction, photocuring rate accelerators (i.e., photosensitizers, are not required in the formulation.

When U.V. radiation is used, an intensity of 0.0004 to 60.0 watts/cm2 in the 240400 nanometer region is usually employed.

The following Examples will aid in explaining, but should not be deemed limiting, the present invention. In all cases unless otherwise noted, all parts and percentages are by weight.

The thermal shock and thermoplastic flow (cut through) test were carried out in accordance with the procedure set out in the U.S. National Electric Manufacturers Association (NEMA) Standards Publication/No. MW 1000-1973.

In all Examples herein, unless otherwise noted, the U.V. radiation from the Addalux lamp had a surface intensity of 13,400 microwatts/cm2 and from the pulsed xenon lamp a surface intensity of 22,000 microwatts/cm2. "Addalux" is a Registered Trade Mark.

EXAMPLE 1.

To a 3-necked, 300 ml round bottom flask equipped with stirrer, addition funnel and reflux condenser was charged under a nitrogen blanket 40.62 g of pyromellitic dianhydride (PMAn) and 75 ml of freshly distilled N-methyl-2pyrrolidone (NMP). To the addition funnel was added 22.11 g of N,N'-bis-(3aminopropyl)dimethylhydantoin and 25 ml of NMP. The PMAn was first dissolved in the NMP and then, while the temperature was kept between 40 60 C, the diamine was added slowly, dropwise, during a period of 1.5 hours. When the addition was completed, the temperature of the reaction mixture was raised to and kept at between 70--80"C while adding 38.71 g of trimethylolpropane diallyl ether during a period of about 20 minutes. Some more NMP was added to the reaction mixture after addition of each reagent. Once the alcohol was added, the mixture was kept between 7(r--80"C for one hour, after which time it was cooled and worked up as follows: The very viscous reaction mixture was dropped into a large quantity of water and shaken vigorously. After discarding the water layer, vigorous agitation with water was repeated three more times. The viscous gum was then dissolved in methanol, and the solution was transferred into a round bottom flask, provided with stirring, Dean-Stark trap and a reflux condenser. 130 ml of benzene was then added and the solution was then boiled vigorously while distilling out most of the methanol along with most of the water. The remaining water, methanol and benzene were then distilled off under reduced pressure at a maximum temperature of 80"C. The brown very viscous product weighed 95 g. The IR spectra indicated that at least 75% of this product was of the formula:

will hereinafter be referred to as Polyene A.

EXAMPLE 2.

To a 3-necked, 300 ml round bottom flask equipped with stirrer and reflux condenser, was added under a nitrogen blanket 25.67 g. of 1,3-bis(aminomethyl)cyclohexane and 100 ml of dimethylformamide. The mixture was heated to approximately 1250C and while maintaining the temperature constant, 69.97 g. of trimellitic anhydride (TMAn) was added in three equal portions. The reaction was allowed to proceed for 1.5 hours and then was cooled to room temperature. The product was worked up by dropping the reaction mixture into a large volume of vigorously stirred water. The water layer was then discarded and the vigorous agitation of the gummy product with water was repeated. After discarding the water again, 25 ml of acetone was used to break up the gum while it started solidifying. To this slurry was added 500 ml of chloroform. The solid product was then filtered and reslurried in benzene. This slurry was then dried by azeotropic distillation, the white solid amide-acid was filtered and then kept in a vacuum dessicator containing P2O5. To a 3-necked, 300 ml round bottom flask equipped with stirrer, reflux condenser and Dean-Stark trap, was added 5.0 g of the white solid amide-acid supra 50 ml of allyl alcohol and 0.1 g of concentrated H2SO4. The mixture was boiled and while allyl alcohol was distilled out of the flask in increments of about 10 ml, fresh allyl alcohol was added to the flask to replace the removed alcohol. This procedure was continued for several hours until sufficient esterification had occurred. Solids in the reaction mixture were then filtered off and the allyl alcohol in the filtrate was stripped under vacuum. The product was a light brown, very viscous liquid of the formula:

which will be referred to hereinafter as Polyene B.

EXAMPLE 3.

To a 3-necked, 300 ml round bottom flask equipped with stirrer, reflux condenser and a modified Dean-Stark trap, was added under a nitrogen blanket 10.31 g. of trimellitic anhydride (TMAn) and 6.37 g. of N,N'-bis(3-aminopropyl)dimethylhydantoin. While the mixture was purged through with nitrogen, it was heated to about 160--180"C. Soon after the fairly fast reaction occurred, the reaction product was cooled to about 80"C. 50 ml of allyl alcohol, 0.009 g of hydroquinone and 0.224 g of concentrated H2SO4 was then added to the pot and the Dean-Stark trap was filled with alumina so that the alcohol could be recirculated to the reaction flask while being dried by the alumina. The reaction mixture was refluxed for about one hour. Upon completion of the reaction, the excess allyl alcohol was stripped off under vacuum. The final product of the formula:

was a yellow-brown viscous material and will be referred to hereinafter as Polyene C.

EXAMPLE 4.

Example 3 was repeated except that the 50 ml of allyl alcohol was replaced by 43.0 g of allyl alcohol and 5.56 g of trimethylolpropane diallyl ether. The final product of the formula:

was a yellow-brown viscous material and will be referred to hereinafter as Polyene D.

EXAMPLE 5.

To a 3-neck, 5-liter, round bottomed flask equipped with stirrer, addition funnel, thermometer, reflux condenser and a nitrogen sparge tube (gas disperse system) was added under nitrogen 322.4 g of trimellitic anhydride acid chloride (TMAn. Cl) and 791 g benzene. The mixture was heated until all the TMAn. Cl dissolved in the benzene. To this solution was added very slowly (via a dropping funnel) a 43% solution of trimethylolpropane diallyl ether in benzene (311.70 g. in 413 g. benzene) while the temperature of the contents in the reaction flask was kept just below 80"C with continuous N2-sparging into the reaction solution. Once all the trimethylolpropane diallyl ether was added, the N2-sparge was continued to remove all the HCI in the reaction mixture. 650 g. of benzene was then distilled out of the reaction vessel. The temperature of the reaction mixture was then lowered to about 60"C at which time a 49% solution of N,N'-bis(aminopropyl)dimethyl- hydantoin, in benzene (176.23 g. in 185 g. benzene) was added at a rate sufficient to sustain a temperature of about 55--70"C. Once all the N,N'-bis(aminopropyl)dimethylhydantoin was added, the reaction mixture was kept at 600C until the IR absorption bands of the anhydride carbonyl groups disappeared. Analysis for unreacted amine groups showed that the amine content was less than 0.2 meq/g.

The resultant product was obtained by distilling off the benzene under vacuum.

The product (741 g) contained 24% by weight imide and an amido-acid polyene of the formula:

which will be referred to hereinafter as Polyene E.

EXAMPLE 6.

Example 1 was repeated with the following variations. 43.44 g of pyromellitic dianhydride were used. The N,N'-bis43-aminopropyl)dimethylhydantoin was replaced by 16.50 g of isophorone diamine, i.e. 3-aminomethyl-3,5,5-trimethylcyclohexylamine. The dropwise addition of this diamine in 25 ml NMP took 2.0 hours. To the reaction mixture at between 7O-800C were added 41.41 g of trimethylolpropane diallyl ether mixed with 9 ml of NMP during a period of about S minutes. The brown very viscous product (about 95 g) of the formula:

will hereinafter be referred to as Polyene F.

EXAMPLE 7.

(comparative) To a 4-necked, 1 1. round bottom flask equipped with stirrer, addition funnel, thermometer, Dean-Stark trap, and reflux condenser was charged under a nitrogen blanket 16.0 g of N,N'-bis(2-carbo yethyl)-dimethylhydantoin, 1.30 g of p-toluene sulfonic acid as catalyst and 100 ml of benzene. The mixture was refluxed until the Dean-Stark trap was full of benzene, and then 3.50 g of allyl alcohol and 12.91 g of trimethylolpropane diallyl ether in 50 ml of benzene was added during a period of 35 minutes. When no more water was azeotroping into the Dean-Stark trap, the heat was turned off and the product was worked up by washing it twice with 150 ml of water, then twice with 100 ml of 5% aq. NaHCO3, and then again twice with 100 ml of water. The benzene layer containing the product was then dried with anhydrous MgSO4, treated with decolorizing carbon, and then distilled under vacuum until all the benzene was taken off. The product, i.e.,

had a C=C content of 5.80 mmoles/g and will be referred to hereinafter as Polyene G.

The polyenes of the instant invention can be imidized per se as is shown in the following examples.

EXAMPLE 8.

A thin film of Polyene A from Example 1 was placed on a sodium chloride IR window and heated for 5 minutes at 2100C. The IR spectrum after heating said polyene showed the disappearance of the amide band and a significant increase of the imide band, evidencing imidization. The imidized polyene of the formula:

will hereinafter be referred to as imidized Polyene H.

EXAMPLE 9.

Example 8 was repeated except that Polyene E from Example 5 was substituted for Polyene A. The results were the same. The imidized polyene of the formula:

will hereinafter be referred to as imidized Polyene J.

Example 8 was repeated using Polyenes B, C, D and F from Examples 2, 3, 4 and 6. The IR spectrum after heating said polyenes in each case showed the disappearance of the amide band and a significant increase of the imide band.

EXAMPLE 10.

To a four-neck, one-liter, round-bottomed flask equipped with stirrer, additional funnel, thermometer, heated (approx. 100-1 100C) Vigreux column, and a nitrogen sparge tube was added under nitrogen 226.32 grams of trimellitic anhydride 248.22 grams of trimethylolpropanediallyl ether and 2.5 grams of 1,6hexamethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate). While the reaction vessel was slowly purged with nitrogen, the reaction mixture was suddenly heated in an oil bath to 2400C. This temperature was maintained for about 4.5 hrs. while the slow nitrogen purge removed the water generated by the reaction. Every 40 minutes, the top layer of the distillate was returned to the pot while the lower layer was discarded. The last two returns of the top layer were timed such that they were done about every 15 minutes before the reaction was considered as finished. The reaction mixture was then rapidly cooled to 1700C.

The Vigreux column was removed from the round bottomed flask. In its place was placed a short inverted U-shaped tube.

To the product made above was added first 0.2 g of hydroquinone and 0.1 g of pyrogallol, and then drop-wise over a 45 minute period 64.32 grams of molten Mphenylenediamine while slowly purging the reaction vessel with nitrogen.

The reaction mixture was then kept for one hour at 1750 C, and the nitrogen flow was increased to achieve a rapid removal of the water arising from the imidization of the amide-acid.

The resultant imidized product of the formula:

will hereinafter be referred to as Polyene T.

The following examples show various curable compositions of either the amide-acid polyene or imide polyene in combination with a polythiol and methods of curing to obtain a cured polythioether product.

EXAMPLE 11.

5.0 g of Polyene E from Example 5 was admixed with 1.57 g of the bis(3mercaptopropionate) of l,3-bis(2-hydroxyethyl)-5,5-dimethylhydantoin), 0.20 g of pentaerythritol tetrakis( -mercaptopropionate), 0.10 g of trimethylolpropane tris(*mercaptopropionate) and 0.137 g of 2,2-dimethoxy-2-phenylacetophenone until homogeneous. The admixture was exposed to U.V. radiation for 15 seconds from Addalux lamp to form a cured polythioether and, thereafter, heated for 5 minutes at about 210"C to imidize the polyene portion. The IR spectrum of the resultant cured solid product showed disappearance of the thiol and amide absorption bands and appearance of the imide absorption bands.

EXAMPLE 12.

9.857 g of Polyene E from Example 5 was heated at 210"C for 5 minutes to imidize the polyene. The thus imidized polyene was admixed with 4.14 g of the bis(3-mercaptopropionate) of 1 ,3-bis(2-hydroxyethyl)-5,5-dimethylhydantoin, 0.40 g of pentaerythritol tetrakis(p-mercaptopropionate), 0.20 g of trimethylolpropane tris(p-mercaptopropionate) and 0.147 g of benzoin isopropyl ether. The admixture was exposed to U.V. radiation from an Addalux lamp for 15 seconds. A cured polythioether product resulted.

EXAMPLE 13.

Using the formulation of Example 11, the procedure was reversed and the formulation was heated for 5 minutes at 2100C followed by U.V. curing for 15 seconds under an Addalux lamp. A cured imidized polythioether product resulted.

EXAMPLE 14.

10 g. of Polyene E from Example 5 was admixed with 4.6 g. of di(2hydroxyethyl)dimethylhydantoin bis(3 -mercaptopropionate), 2.5 g. of pentaerythritol tetrakis( -mercaptopropionate) and 0.166 g. of benzopinacol until homogeneous. The admixture was heated at 1800C for 5 minutes. A cured solid imidized polythioether product resulted.

The following examples show the utility of the polyene of the instant invention with a polythiol in forming an imidized cured polythioether coating when subjected to U.V. radiation and heat. When U.V. radiation is used, a photosensitizer or photocuring rate accelerator is usually added to the system along with various conventional stabilizers to extend shelf life.

The amide-acid polyenes combined with a polythiol will be compared with polyene/polythiol systems in which the polyene is not imidizable or is not imidized and thus does not have the improved higher temperature properties such as are desired in wire coating.

EXAMPLE 15.

The following formulations were made up from accurately weighed ingredients and admixed until homogeneous: Formulation A 5.00 g. Polyene A from Example 1 3.26 g. tris(hydroxyethyl)isocyanurate tris(3-mercaptopropionate) 0.083 g. benzoin isopropyl ether (photosensitizer) 0.826 g. trimethylolpropane diallyl ether 0.826 g. dimercaptopropionate of N,N'-bis(2-hydroxyethyl)dimethylhydantoin 0.083 g. benzopinacol 0.005 g. stabilizer package Formulation B 3.78 g. Polyene A from Example 1 1.22 g. tris(hydroxyethyl)isocyanurate tris(3-mercaptopropion ate) 0.50 g. dimercaptopropionate of N,N'-bis(2-hydroxyethyl)dimethylhydantoin 0.25 g. trimethylolpropane diallyl ether 0.10 g. benzoin isopropyl ether 0.005 g. stabilizer package Formulation C 5.00 g. Polyene D from Example 4 4.28 g. tris(hydroxyethyl)isocyanurate tris(3-mercaptopropionate) 1.41 g. dimercaptopropionate of N,N'-bis(2-hydroxyethyl)dimethylhydantoin 0.36 g. trimethylolpropane diallyl ether 0.186 g. benzoin isopropyl ether 0.010 g. stabilizer package Formulation D 10.0 g. Polyene A from Example 1 3.25 g. tris(hydroxyethyl)isocyanurate tris(3-mercaptopropio Formulation E 10.0 g. Polyene F from Example 6 3.02 g. dimethylolpropionic acid bis(3-mercaptopropionate) 0.33 g. benzoin isopropyl ether 0.018 g. stabilizer package Formulation F 5.0 g. Polyene E from Example 5 2.07 g. dimercaptopropionate of N,N'-bis(2-hydroxyethyl)dimethylhydantoin 0.20 g. commercially available pentaerythritol tetrakis(p-mercaptopropionate) 0.10 g. trimethylolpropane tris(p-mercaptopropionate) 0.137 g. 2,2-dimethoxy-2-phenylacetophenone 0.009 g. stabilizer package Formulation G (Comparative) 45.0 g. diallyl maleate 82.7 g. tris(hydroxyethyl)isocyanurate tris(3-mercaptopropionate) 3.83 g. benzoin isopropyl ether 1.99 g. stabilizer package Formulation H (Comparative) 20.00 g. Polyene G from Example 7 2.38 g. commercially available diallyl-isophthalate 23.66 g. tris(hydroxyethyl)isocyanurate tris(3-mercaptopropionate) 1.38 g. benzoin isopropyl ether 1.41 g. stabilizer package Formulation I 20.00 g. Polyene T of Example 10 3.01 g. triallyl isocyanurate 15.25 g. pentaerythritol tetrakis(3-mercaptopropionate) 1.34 g. dimercaptopropionate of N,N'-bis(2-hydroxyethyl)dimethylhydantoin 0.792 g. 2,2-dimethoxy-2-phenylacetophenone 0.008 g. stabilizer package EXAMPLE 16.

A 24 AWG copper wire was passed through a degreasing bath of methylene chloride followed by drying. The wire was cut into 10 sections and each wire section was coated with one of the Formulations A-I from Example 15 with the extra wire section also being coated with Formulation F, all at ambient conditions.

Each section of the thus coated wire was then passed through a die to insure a homogeneous thickness of 1 mil and through a surrounding bank of U.V. pulsed xenon lamps whose major spectral lines were all above 300 Angstroms at a speed of 20 feet per second for an exposure period of 2 seconds. The sunlamps were so positioned that the surface intensity on the radiation curable composition was 22,000 microwatts/cm2. All the resulting wire sections had a smooth, cured coating of I mil thickness and showed good flexibility and adhesion on bending. The thus cured coated wire sections coated with Formulations A, B, C, D and one section coated with Formulation F were then heated at 2l0-2200C for 5 minutes to affect imidization. All the wire sections with their cured coating were then subjected to standard NEMA heat shock and thermoplastic flow test. The results are shown in TABLE I.

TABLE I.

Formulations Properties of Wire-Coated Formulations Average Cut-Through Heat Shock (20 ó Stretched Temperature ("C) Wire at 1750C for 30 Minutes A 220 passed 1 x mandrel B 260"C passed 3 x mandrel C passed 2 x mandrel D 210 passed 2 x mandrel E 200 passed 1 x mandrel F (imidized) 225 passed 3 x mandrel F (not imidized) 1250 passed 2 x mandrel G 255 failed 5 x mandrel H 100" failed 5 x mandrel I 350" passed 2 x mandrel Note: "3 x Mandrel" means that diameter of mandrel was three times the diameter of the wire etc.

Thus, as can be seen from the data in TABLE I, the radiation curable formulations containing an imidized polyene (Formulations A-F and I) have improved high temperatures properties over conventional radiation curable polyene/polythiol formulations (Formulations G and H) wherein the polyene is not imidizable and over Formulation F which was not imidized.

The amide-acid polyenes of the instant invention can also be synthesized in polymeric form as shown by the following example: EXAMPLE 17.

To a 3-necked, 300 ml round bottom flask equipped with stirrer, addition funnel, thermometer and nitrogen sparge tube was charged under a nitrogen blanket 24.37 g. of pyromellitic dianhydride (PMAn) and 44 ml of freshly distilled N-methyl-2-pyrrolidone (NMP). The flask was heated to about 90"C to dissolve the PMAn, 13.4 g. of N,N'-bis(3-aminopropyl)dimethlhydantoin and 15 ml NMP were charged to the addition funnel. The flask was cooled to 750C and the contents of the addition funnel were added to the flask over a one minute period. The contents of the flask was stirred at 700C for 30 minutes after which 6.29 g. of allyl alcohol were added to the flask. The contents of the flask was then charged into chloroform and filtered. A light brown polymeric polyene product (molecular weight 6600 indicating 6--7 repeating units) resulted. The IR spectrum showed little or no imide present in the product and a substantial amide band present.

This polymeric polyene will be referred to hereinafter as Polyene K.

5 g of Polyene K were heated for 10 minutes at 2200C. The resultant product was dark brown, indicative of imidization.

5 g of Polyene K were admixed with 1.96 g of dimethylolprqpionic acid bis(3mercaptopropionate) and 0.139 g. of 2,2-dimethoxy-2-phenylacetophenone. The admixture was exposed to U.V. radiation for 3 1/2 minutes from an Addalux lamp.

A cured, solid polythioether resulted.

EXAMPLE 18.

The formulation of Example 11 was coated to 1 mil thickness on each of the following substrates: paper, cardboard, aluminium foil, steel plate stock, "Mylar" (Registered Trade Mark), polyester film, plywood, ceramic and a concrete block of the type used in building construction. The thus coated substrates were exposed to U.V. radiation for 30 seconds from an Addalux lamp to form a cured polythioether coating and, thereafter, heated for 5 minutes at 2100C to imidize the polyene portion.

EXAMPLE 19.

To a 3-necked, 300 ml round bottom flask equipped with stirrer, addition funnel and an air sparge tube (gas disperse system) was added 50 g of glacial acetic acid, 68.20 g of trimellitic anhydride acid chloride, 0.585 g of 2,6-di-t-butyl-4methylphenol and 0.0585 g of methyl hydroquinone. After dissolution of the solids, the flask was immersed into an ice/water bath. A mixture of 32.10 g of triethyl amine (TEA) and 45.30 g of hydroxybutyl acrylate (HBA) was then added dropwise to the cold solution while continuously purging the reaction mixture with air. Once the HBA/TEA mixture was added (addition took 70 minutes), the cloudy reaction mixture was left standing for 10 minutes. 17.32 g of solid m-phenylene diamine was then added slowly while keeping the reaction mixture at about 35"C. The disappearance of the anhydride group was followed by infrared spectroscopy. Once all the anhydride reacted with the amine, the reaction mixture was dropped into a large excess of vigorously agitated water. The viscous gummy product was then dissolved in acetone and the solution was dried with anhydrous magnesium sulfate and treated with decolorizing carbon. To the clear slightly yellow solution was added 0.585 g of 2,6-di-t-butyl4-methylphenol and 0.0585 g of methyl hydroquinone. The bulk of the acetone was then evaporated off slowly at nearroom temperature. Residual acetone was evaporated off at 80OC for 0.5 hours.

Interpretation of the IR spectrum of the final cloudy brick-red waxy material showed that the material contained primarily the compound of the formula:

hereinafter referred to as Polyene L, and small amounts of the cyclized imide of the compound above.

EXAMPLE 20.

A portion of hour the compound made and described under Example 19 was heated to l500C for 0.5 hours to effect imidization of Polyene L.

Interpretation of the IR spectrum of the final light yellow beige glassy solid showed that the material contained primarily the compound of the formula:

referred to hereinafter as Polyene M, and small amounts of the uncyclized amideacid.

EXAMPLE 21.

To a 3-neck, 2 liter, round bottomed flask equipped with stirrer, addition funnel, thermometer, reflux condenser and a nitrogen sparge tube was added under nitrogen 309.30 g of trimellitic anhydride acid chloride (TMAn.CI) and 425 g toluene. The mixture was heated until all the TMAn.C1 dissolved in the toluene (15-20 minutes). To this solution was added via a dropping funnel, slowly over a 2 hour period, 296.40 g of trimethylolpropane diallyl ether (E) while the temperature of the contents in the reaction flask was kept at about 80"C with continuous N2purging into the reaction solution.

The N2-effluent, carrying much HCI and some toluene, was bubbled through a trap, to condense the toluene, and an aqueous NaOH scrubber, to neutralize the HCI.

Once all the E was added, the reaction mixture was kept at 800C for another 30 minutes. It was then heated to its boiling point (1 180C), and one half of the toluene was distilled out of the reaction vessel while slowly purging with nitrogen. The removal of the toluene took about 20 minutes. The volume of toluene which was distilled out was then replaced with fresh toluene, and the E-ester of the trimellitic anhydride (TMAn.E)/toluene solution was then subjected to an intermittent stream of steam while keeping the reaction mixture at a mild reflux. The water that was distilled out of the vessel was collected and analyzed for HCl. The total time to remove the HCI was about 4.75 hours. The total amount of water used was about 260 ml.

Once the HCl was removed, the TMAn-E/toluene solution was azeotropically dried and then filtered.

To the dry TMAn-E/toluene solution was added batchwise, while keeping the temperature down to room temperature, a total of 77.03 g of m-phenylene diamine (PDA). The PDA was added "tricklewise" in 10% increments and, after each addition, time was allowed for the PDA to completely dissolve before the next addition was made. The time between incremental additions (up to 70 /O of the total 'addition was about 10 minutes. This time increased to about 20 minutes for each remaining incremental addition. Once all the PDA was added and dissolved, the reaction solution was kept at 550C for one hour.

The reaction solution was then refluxed for about 4 1/2 hours while removing azeotropically the water that is generated during the imidization of the amide-acid.

Once complete imidization was achieved, the toluene was distilled out at a reduced pressure. When most of the toluene was removed, the temperature of the kettle was increased to 130--1400C to reduce the viscosity of the brown product and thus increase the rate of removal of residual toluene. The resultant imidized polyene of the formula:

will hereinafter be referred to as Polyene N.

EXAMPLE 22.

Example 21 was repeated except that the procedure for removing HCI was varied, as follows. Instead of adding steam intermittently to the hot solution of Eester of trimellitic anhydride (TMAn.E) in toluene a total of 100 ml of water was added in 10 ml increments and after each addition the water was azeotroped off again. Each water increment was added at slightly below 100"C, and it carried over a large amount of the residual HCI left in the TMAn.E/toluene solution. The water increments which were distilled off were titrated for HC1. The total time to remove the HCI was about 4.5 hours.

After the bulk of the last water-increment was removed (for HC1-content determination), the TMAn.E/toluene solution was azeotroped further (approximately 3-4 hours) to achieve complete dryness of the system. The solution was then filtered.

The introduction of the 77.03 g of m-phenylene diamine and all subsequent operations were performed as in Example 20, yielding a similar imidized polyene.

EXAMPLE 23.

The following formulations were made up from accurately weighed ingredients and admixing until homogeneous: Formulation J 10.0 g Polyene P (an imidized polyene formed from stoichiometric amounts of trimellitic anhydride acid chloride, N,N'-bis(3-aminopropyl)dimethyl hydantoin and hydroxybutyl acrylate by the procedure of Example 19) 0.2 g 2,2-dimethoxy-2-phenylacetophenone 0.06 g stabilizer package Formulation K 10.0 g Polyene Q (an amide-acid polyene formed from stoichiometric amounts of trimellitic anhydride acid chloride, N,N'-bis(3-aminopropyl)di methylhydantoin and hydroxybutyl acrylate by the procedure of Example 19) 1.5 g trimethylolpropane tris(fi-mercaptopropionate) 0.23 g 2,2-dimethoxy-2-phenylacetophenone 0.06 g stabilizer package Formulation L 10.0 g Polyene O (an amide-acid)polyene formed from stoichiometric amounts of trimellitic anhydride acid chloride, hexamethylene diamme and hydroxybutyl acrylate by the procedure of Example 19) 0.44 g dimercaptopropionate of N,N'-bis(2-hydroxyethyl)dimethylhydantoin 0.029 g 2,2-dimethoxy-2-phenylacetophenone 0.006 g stabilizer package EXAMPLE 24.

The formulations of Example 23 were coated to a thickness of 2-5 mils onto various substrates and exposed under atmospheric conditions, unless otherwise stated, to an Addalux U.V. lamp whose major spectral lines were all above 2400 Angstroms whereby the surface intensity of the radiation on the coating was 20 milliwatts/cm2. In some cases the U.V. cure was followed by a heating step. The results are shown in Table II.

TABLE II.

U.V. CURE HEAT CURE Exposure. Temp. Time RESULTS FORMULATION SUBSTRATE Time (min.) Medium ( C) (min.) Adhesion Coating L glass 1.0 air none good soft L glass 1.0 N2 none good tough, hard J glass 1.0 air none good hard K copper foil 1.5 air 175 2.0 excellent hard copper clad K circuit board 1.5 air 175 2.0 excellent hard K aluminum foil 1.5 air 175 2.0 good hard K paper 1.5 air 175 2.0 good hard K enameled sheet 1.5 air 175 2.0 good hard metal K asbestos tile 1.5 air 175 2.0 good hard K glass 1.5 air 175 2.0 good hard EXAMPLE 25.

To a 3-necked, 300 ml round bottomed flask equipped as in Example 19 were added 59 g of glacial acetic acid, 71.72 g of trimellitic anhydride acid chloride, 0.596 g of 2,6-di-t-butyl-4-methylphenol and 0.060 g of methyl hydroquinone. After dissolution of the solids, the flask was immersed in an ice/water bath. A mixture of 37.00 g of triethyl amine (TEA) and 43.27 g of hydroxyethyl methacrylate (HEMA) was then added dropwise to the cold solution while continuously purging the reaction mixture with air. The procedure of Example 18 was then repeated, except for the minor variations that 18.15 g of m-phenylene diamine were added to the HEMA/TEA reaction mixture and the amounts of 2,6-di-t-butyl-4-methylphenol added to the clear slightly brown solution were 0.596 and 0.060 g respectively.

Interpretation of the IR spectrum of the final cloudy tan waxy material showed that the material contained primarily the compound of the formula:

hereinafter referred to as Polyene R, and small amounts of the cyclized imide of the compound above.

EXAMPLE 26.

A portion of the compound made and described under Example 25 was heated to 1500C for 0.5 hours to effect imidization of Polyene R.

Interpretation of the IR spectrum of the final tan glassy solid showed that the material contained primarily the compound of the formula:

referred to hereinafter as Polyene S, and small amounts of the uncyclized amideacid.

EXAMPLE 27.

A 24 AWG copper wire was coated with bullet dies (two passes, 1.8 mil total build) using Formulation L. After each pass the coating was cured, for 4 seconds, with a medium pressure mercury lamp. The resulting coating was hard, flexible and well adhered to the copper wire. The coated wire when subjected to standard NEMA tests had a heat shock of 2 x pass (20% stretched) and a cut through of 3500C.

Claims (48)

WHAT WE CLAIM IS:

1. Amide-acid and imide polyenes having the general formula:

wherein R represents a divalent organic group having at least 2 carbon atoms which is a residue of a diamine of formula NH2-R-NH2 and the nitrogen atoms shown are attached to different carbon atoms of the R group; R' represents an aromatic ring-comprising group, and at least the pairs of carbonyl groups (a,a) and (b,b) are bonded to pairs of adjacent aromatic ring carbon atoms of the R' group; Z and Z' represent a hydrogen atom and a hydroxyl group respectively, or Z and Z' together represent a single bond between the nitrogen atom and carbon atom to which they are respectively attached, thereby completing a cyclic imide group; A represents an alkylene group having from 1 to 10 carbon atoms; Y represents a group of formula -CR"=CH2, -O-(CH2)d-CR"=CH2,

in which R" represents a hydrogen atom or a methyl group; k and h are 0 or 1; m and d are 1 to 10 and p is 0 to 10 but can only be a positive number when h and k are each 1; and the arrowed bonds indicated "X" denote positional isomerism between substituents bonded by pairs of adjacent arrows.

2. Amide-acid polyenes having the general formula:

wherein all symbols are as defined in claim 1.

3. Imide polyenes having the general formula:

wherein all symbols are as defined in claim 1.

4. Polyenes according to claim 1, 2 or 3 having the general formula

wherein the symbols are as defined in claim 1, R' thus representing a tetravalent aromatic ring-comprising group having two pairs of adjacent ring carbon atoms thereof bonded to the four carbonyl groups shown in the formula.

5. Polyenes according to claim 4 wherein R' represents a group of formula:

6. Polyenes according to claim 1, 2 or 3, wherein k, h and p are 0.

7. Polyenes according to claim 1 or 6, wherein R' represents a group of formula:

in which the left-hand bond is present in the 4- or 5-position in each individual R' group, and k and h are 0.

8. Polyenes according to any preceding claim wherein R represents a hydantoin ring-containing group of formula:

a m-phenylene group, an m-xylylene group or a 4,4'-diaminodiphenylmethane group.

9. Polyenes according to any preceding claim wherein Y represents a group of formula CRH=CH2, -O-(CH2)d-CR"=CH2 or

as defined in claim 1.

10. Polyenes according to claim 9 wherein -(-A-)(Y)m represents a group of formula:

or -CH2-CH=CH2

11. Polyenes according to claim 1 substantially as described in any one of Examples 1 to 6, 8 and 9.

12. Polyenes according to any one of claims I to 8 wherein Y represents a group of formula:

as defined in claim 1.

13. Polyenes according to claim 1 substantially as described in any one of Examples 19 to 26.

14. A process of preparing an amide-acid polyene or a mixture of amide-acid and imide polyenes which comprises reacting in an inert atmosphere, under substantially anhydrous conditions, in substantially stoichiometric amounts, (1) at least one primary diamine having the general formula: H2N-R-NH2 wherein R is a divalent group containing at least 2 carbon atoms, the two amino groups of said diamine being attached to separate carbon atoms of the R group, with (2) at least one aromatic acid anhydride of the formula:

wherein R' and the carbonyl groups bonded thereto are as defined in claim 1, 4, 5 or 7 and X represents a halogen atom and (3) at least one ethylenically unsaturated alcohol of the formula: lICA+(Y) wherein A, Y and m are as defined in claim 1, in an organic solvent for the amide-acid polyene product, at a temperature of from 20 to 1000 C, but kept low enough to prevent complete conversion to imide by a cyclic imide-forming reaction of the -NH- and neighbouring acid group of the amide-acid polyene.

15. A process according to claim 14 wherein the starting aromatic acid anhydride contains an acid halide group, it is first reacted with the ethylenically unsaturated alcohol, to form a product comprising a monoester, the hydrogen halide thereby liberated is removed, and the product is then reacted with the diamine.

16. An amide-acid polyene or mixture thereof with an imide polyene when obtained by a process claimed in claim 14 or 15.

17. A process according to claim 14 or 15 wherein Y or A+(Y)m, respectively represents a group defined in claim 9 or 10.

18. An amide-acid polyene or mixture thereof with an imide polyene when obtained by a process claimed in claim 17.

19. A process of preparing an imide polyene according to claim 3, which comprises heating an amide-acid polyene according to claim 2 or any one of claims 4 to 13 when appendant to claim 2 or to a product according to claim 16, at a temperature of from 50--250"C, but high enough to cause a cyclic imide-forming reaction of the -NH- and neighbouring acid groups of the amide-acid polyene.

20. A process according to claim 19, wherein the amide-acid polyene is heated in an inert solvent for the amide-acid polyene at a temperature of 50-1500C, but kept high enough to cause a cyclic imide-forming reaction of the -NH- and neighbouring acid groups of the amide-acid polyene.

21. An imide polyene when obtained by a process claimed in claim 19 or 20.

22. A process according to claim 19 or 20 wherein the amide-acid polyene is as defined in claim 9, 10, 11 or 18.

23. An imide polyene when obtained by a process claimed in claim 22.

24. A photo curable composition comprising (A) a polyene according to any one of claims 1 to 13, 16 and 21, (B) a polythiol having a molecular weight of from 94 to 20,000, of the general formula: Rg < SH)n where n is at least 2 and Ra is a polyvalent organic group, the sum of all the symbols m and n being greater than 4, the polyene/polythiol mole ratio being in the range 0.2 to 8.0:1 respectively, and (C) a photocuring rate accelerator.

25. A composition according to claim 24 which further comprises a pinacol or derivative thereof of formula:

wherein each of R1 and R3 independently represents an aromatic group, each of R2 and R4 independently represents a substituted or unsubstituted aliphatic group or an aromatic group and each of X and Y independently represents a hydroxyl, alkoxy or aryloxy group.

26. A composition according to claim 24 or 25, wherein the polyene is as defined in claim 9, 10, 11, 18 or 23.

27. A substrate coated with a composition according to claim 24 or 25 in cured or uncured form.

28. A coated electrical conductor according to claim 27.

29. Coated wire according to claim 27 or 28.

30. A substrate coated with a composition defined in claim 26.

31. A process of forming a solid cured polythioether, which comprises exposing to the action of a free radical generator a composition claimed in claim 24 or 25.

32. A process according to claim 31 wherein the free radical generator is actinic radiation or high energy ionising radiation.

33. A process of forming a solid cured imide containing polythioether, from a composition according to claim 24 wherein the polyene comprises an amide-acid polyene as defined in claim 2, which process comprises in either order or simultaneously exposing the composition to a free radical generator and heating the composition at a temperature in the range 50-2500C and to cause a cyclic imide-forming reaction of the -NH- and neighbouring acid groups.

34. A process according to claim 33, wherein the starting composition is simultaneously exposed to a free' radical generator and heated, by heating a pinacol-containing composition claimed in claim 25.

35. A process according to any one of claims 31 to 34 wherein a coating of the polythioether is formed in situ on a substrate by a process comprising coating the starting composition on the substrate and carrying out the process defined in said claim on the composition coated on the substrate.

36. A process according to claim 31 or 32 wherein the starting composition contains a polyene comprising an imide polyene defined in claim 3, and a coating is formed on the substrate by a process comprising coating the starting composition on the substrate and exposing the coated composition to the action of the free radical generator.

37. A process according to claim 36 wherein the substrate is an electrical conductor.

38. A process according to claim 36 or 37 wherein the substrate is wire, it is coated with the composition and the thickness of the coating of uncured composition is adjusted by passing the wire through a die.

39. A process according to any one of claims 31 to 38 wherein the starting composition is as claimed in claim 26.

40. A photopolymerizable composition comprising (A) a polyene according to claim 12, and (B) a photopolymerizing rate accelerator.

41. A substrate coated with a composition according to claim 40 in polymerized or unpolymerized form.

42. A coated electrical conductor according to claim 41.

43. A process of coating a substrate which comprises applying to a substrate a polymerizable composition according tq claim 40 and exposing said composition to a free radical generator to form a solidified coating on said substrate.

44. A process according to claim 43 wherein the free radical generator is actinic radiation, or high energy ionizing radiation.

45. A process according to claim 43 or 44, which comprises applying to a substrate a polymerizable composition according to claim 40 wherein the polyene comprises an amide-acid polyene according to claim 12 when appendant to claim 2, and in either order or simultaneously exposing the composition to a free radical generator and heating the composition at a temperature in the range 50-2500C to cause a cyclic imide-forming reaction of the -NH- and neighbouring acid groups.

46. A process according to claim 43, 44 or 45 wherein the substrate is an electrical conductor.

47. A process according to claim 43, 44, 45 or 46, wherein the substrate is wire, it is coated with the composition and the thickness of the coating of unpolymerized composition is adjusted by passing the wire through a die.

48. Polyenes according to claim 1, substantially as described in Example 10.