WO1997003142A1

WO1997003142A1 - Formulations containing poly-(nitrile oxide) reagents

Info

Publication number: WO1997003142A1
Application number: PCT/US1996/011498
Authority: WO
Inventors: Zenon Lysenko; Ritchie A. Wessling; Gene D. Rose
Original assignee: The Dow Chemical Company
Priority date: 1995-07-10
Filing date: 1996-07-10
Publication date: 1997-01-30
Also published as: AU6487596A

Abstract

Curable compositions contain: (a) at least one nitrile oxide monomer which contains on average more than one stable nitrile oxide group per molecule; and (b) at least one polyunsaturated monomer which: (1) has a weight average molecular weight of no more than 5000; and (2) contains on average more than one insaturated moiety which contains a sterically-unhindered carbon-carbon or carbon-nitrogen double bond or triple bond. The monomers are selected such that either the nitrile oxide monomers or the polyunsaturated monomers or both contain on average more than two reactive groups per molecule, and such that the equivalent ratio of nitrile oxide to unsaturated moieties is more than 0.5:1 and less than 2:1. The compositions can be used in coatings, composites, laminates and injection moldings.

Description

FORMULATIONS CONTAINING POLY-(NITRILE OXIDE) REAGENTS

The present invention relates to monomer formulations which polymerize by addition reactions to form linear thermoplastic or cured/cross-linked thermoset polymers. Nitrile oxide compounds contain the characteristic structure shown in Formula I.

-C≡ N-0 (I)

The nitrile oxide group reacts with carbon-carbon and carbon-nitrogen double and triple bonds to form heterocyclic rings. See, for example, C. Grundmann & P. Grϋnanger, The Nitrile Oxides at 85-132 (Springer-Verlag 1971). In rare cases, these addition reactions of nitrile oxide compounds have been used to cross-link unsaturated polymers. See Breslow et al.,

U.S. Patent 3,390,204 (June 25, 1968); Breslow et al., U.S. Patent 3,717,560 (February 20, 1973); Breslow et al., U.S. Patent 3,71 1 ,449 (January 16, 1973); and Breslow et al., "One-Component Sealant Based on 1,3-Dipoles," Vol. 32 J. App. Poly. Sci. at 4657 (1986).

The nitrile oxide compounds used in the past were difficult to handle in a practical sense because they tend to dimerize. Two nitrile oxide groups react with each other at room tem perature to form a stable 1,2,5-oxadiazole-2-oxide (furoxan) moiety. The cross¬ linkers of the Breslow et al., references were usually generated in situ to prevent them from polymerizing before they could be used.

However, recent work by Professor Krayushkin of the Zelinsky Institute of Organic Chemistry in Moscow, Russia, has shown that bis-(nitrile oxide) compounds can be stable at room temperature if the compound contains steric hindering groups adjacent to the nitrile oxide groups to inhibit them from reacting with each other. Professor Krayushkin has offered two sterically-hindered bis-(nitrile oxide) compounds for sale: 4,6-diethyl-1,3-bis- (nitrile oxide)benzene (TON-1) and 2,4,6-triethyl-1,3-bis-(nitrile oxide)benzene (TON-2), which are illustrated in Formula II:

Formula II

TON-1 TON-2 Likewise, C. Grundmann & P. Grϋnanqer, The Nitrile Oxides at 19 (Springer-Verlag 1971), reports that the following bis-(nitrile oxides) are indefinitely stable: 2,4,6-trimethyl-isophthaio- bis-(nitrile oxide); 4-dimethylamino-2,6-dimethyl-isophthalo-bis-(nitrile oxide); and 2,3,5,6- tetramethyl-terephthalo-bis-(nitrile oxide). The previous work with stabilized nitrile oxide compounds has focused on narrow applications. TON-2 has been shown to be useful for the vulcanization of natural rubber. Grundmann & Grϋnanger showed that 2,3,5,6-tetramethyl-terephthalo-bis-(nitrile oxide) can react with p-bis-ethynylbenzene in the presence of solvent to make a linear polymer. (They report that without solvent the mixture is explosive.) What is needed are formulations which can apply the nitrile oxide chemistry to a broader range of potential uses.

One aspect of the present invention is a composition which comprises:

(a) at least one nitrile oxide monomer which contains on average more than one stable nitrile oxide group per molecule; and

(b) at least one polyunsaturated monomer which: (1) has a weight average molecular weight of no more than 5000; and

(2) contains on average more than one unsaturated moiety which contains a carbon-carbon or carbon-nitrogen double bond or triple bond capable of reacting with the stable nitrile oxide groups, wherein the equivalent ratio of nitrile oxide groups to unsaturated moieties is more than 0.5: 1 and less than 2: 1, characterized in that either the nitrile oxide monomers or the polyunsaturated monomers or both contain on average more than 2 reactive groups per molecule.

A second aspect of the present invention is a method to use the composition comprising the steps of: (1) applying a composition of the present invention in a thickness of no more than

2 mm to a substrate; and (2) curing the formulation to provide a cured coating.

A third aspect of the present invention is a method to use the composition comprising the steps of: (1) impregnating a fibrous substrate with a composition of the present invention;

(2) optionally, pressing two or more impregnated substrates together to form a laminate; and

(3) curing the composition to form a matrix composite.

A fourth aspect of the present invention is a method to use the composition comprising the steps of:

(1) injecting the composition into a mold; and

(2) curing the composition to form a molded article. A fifth aspect of the present invention is a process to make an advanced bisJnitrile oxide) resin by reacting an approximately-difunctional, stable nitrile oxide monomer with an approximately-difunctional polyunsaturated monomer, characterized in that the reaction mixture contains from 1.2 to 10 equivalents of nitrile oxide monomer per equivalent of unsaturated monomer.

A sixth aspect of the present invention is an advanced nitrile oxide resin which:

(1) contains on average more than 1 stable nitrile oxide group per molecule;

(2) contains a plurality of divalent organic groups linked by isoxazoline, isoxazole, oxadiazoline, oxadiazole and/or oxadiazolinone groups; and (3) has a weight per equivalent of nitrile oxide group of 100 to 5000.

A seventh aspect of the present invention is a nitrile oxide cross-linking compound which:

(1) contains on average more than 2 stable nitrile oxide groups per molecule; and

(2) is made by reacting a polyunsaturated monomer, which contains on average more than 2 unsaturated moieties per molecule, with at least 1 mole of approximately-difunctional nitrile oxide monomer per equivalent of unsaturated moiety.

Compositions of the present invention have relatively low viscosity and cure at about ambient temperature without the release of volatile by-products. They can be used to make a variety of thermoset structures containing repeating units linked by nitrogen-oxygen heterocyclic rings. Advanced resins of the present invention are useful in compositions of the present invention. Nitrile Oxide Monomers

The present invention uses nitrile oxide monomers, which contain on average more than 1 stable nitrile oxide group bonded to a central moiety (Q). They are preferably represented by Formula III: Q(CNO)_x (III) wherein Q is a central moiety and x is a number of nitrile oxide substituents greater than 1. The central moiety (Q) is preferably organic. It preferably contains an aromatic moiety, an aliphatic moiety or both. It more preferably contains aromatic, or both an aromatic moiety and an aliphatic moiety. It most preferably contains both an aromatic moiety and an aliphatic moiety. For example, the central moiety (Q) may be a substituted phenylene moiety, a substituted naphthylene moiety, a substituted biphenylene moiety, a substituted alkylene-bisphenylene moiety, or an oligomer, an ether, an ester, or a ketone containing such moieties. The preferred substituents and their positioning are further described hereinafter. The central moiety (Q) is preferably a substituted phenylene ring or a substituted bis-phenylene moiety.

The "stable nitrile oxide group" should be sufficiently stable against dimerization so that the nitrile oxide monomer can be made separately from the composition and formulated later with other components to make the composition. The stable nitrile oxide group is preferably storage-stable for at least 30 days at about room temperature, more preferably for at least 60 days and most preferably for at least 90 days. By "storage-stable" we mean that preferably no more than 10 percent of the nitrile oxide groups dimerize, more preferably no more than 5 percent, and most preferably no more than 1 percent. However, the stable nitrile oxide group must still be capable of reacting with an available unsaturated moiety as described hereinafter.

The stabilization of nitrile oxides is discussed in C. Grundmann & P. Grϋnanger, The Nitrile Oxides at 13-14 (Springer-Verlag 1971). The nitrile oxide is preferably stabilized by o having steric hindering groups adjacent to each nitrile oxide group in order to inhibit two nitrile oxide groups from reacting with each other. When the nitrile oxide group is bonded to an aromatic ring, then the central moiety preferably contains at least one hindering moiety ortho to the nitrile oxide group, and more preferably contains 2 hindering moieties ortho to the nitrile oxide group. 5 The hindering moiety or moieties must be large enough to inhibit the nitrile oxide groups from reacting with each other, but small enough to permit the nitrile oxide groups to react with unsaturated moieties on other monomers. The formula weight of each hindering moiety is preferably 15 to 100, and more preferably 15 to 60. Examples of suitable hindering moieties include: alkyl, alkoxy, aryl, aryloxy, ester, sulfonyl ester, and halogen 0 moieties. Each hindering moiety preferably contains a chlorine atom, a bromine atom, a Iower (C, ) alkyl group, a Iower alkoxy group or a phenoxy group. It more preferably is a Iower alkyl group, a chlorine atom or a bromine atom, and most preferably is a methyl, ethyl or t-butyl group.

The nitrile oxide monomer is preferably represented by any of Formulae IV(a)-(b): 5

Formula IV

( a ) (b) wherein: 5 "A" is a polyvalent moiety. "A" is preferably a Iower alkylene group, an oxygen atom, a carbonyl group, an arylene group, a moiety containing two or more such preferred groups, or an oligomer. "x" represents a number of substituents greater than 1. x is preferably on average 2 to 12.

"y" is a number of R1 groups which is 1 to 5, and is preferably 3 to 4, on average.

"z" represents a number of nitrile oxide groups greater than 1. z is preferably on average 2 to 4, and more preferably 2 to 3.

Each R¹ is a hydrogen atom or a steric hindering moiety selected such that at least one R¹ adjacent to each nitrile oxide group is a steric hindering moiety. The preferred embodiments of R1 have already been described.

Of course, the nitrile oxide monomer may be TON-1 or TON-2. Other specific examples of suitable nitrile oxide monomers are illustrated in Formulae IV(e)-(q):

Formula IV

Rl

)_U

5

wherein R1 is as previously described, each Y is -0-, -S-, -NR'-, a carbonyl group, or a Iower (C,-

C₆) alkyl group, and the sum of m and n averages greater than 1. Preferably, each R1 is a hindering moiety and m and n each average 1.

The nitrile oxide monomer is preferably either approximately-difunctional or multi-functional:

Approximately-difunctional monomers contain on average more than one nitrile oxide group per molecule. They preferably contain on average at least 1.5 nitrile oxide groups per molecule, more preferably at least 1.8 nitrile oxide groups per molecule, and most preferably at least 2 nitrile oxide groups per molecule. They contain on average no more than 2.1 nitrile oxide groups per molecule, and preferably contain on average no more than 2 nitrile oxide groups per molecule. Multi-functional monomers contain on average more than 2J nitrile oxide groups per molecule. They preferably contain on average at least 2.2 nitrile oxide groups per molecule, more preferably at least 2.4, and most preferably at least

2.8. The maximum number of nitrile oxide groups is limited by practical considerations, such as the structure of the central moiety and the intended use of the monomer. When the central moiety is a small simple structure (such as the structures illustrated in Formula IV(a) and (b), then the monomer preferably contains on average no more than 5 nitrile oxide groups per molecule, more preferably no more than 4, and most preferably no more than 3. When the central moiety is a larger structure (such as an oligomer), then the nitrile oxide monomer preferably contains on average no more than 12 nitrile oxide groups per molecule, more preferably no more than 8, and most preferably no more than about 5.

The weight average molecular weight of each nitrile oxide monomer is preferably less than 5000, more preferably no more than 2500, more highly preferably no more than 1,000, and most preferably no more than 500. The minimum molecular weight is not critical as long as the monomers contain the requisite number of reactive sites and will stay in a Iiquid composition. In most cases, the weight average molecular weight of the monomers is preferably at least 125 and more preferably at least 190.

Several known reactions can be used to synthesize nitrile oxide groups on the monomers:

(1) A primary alkyl nitrate group reacts with phenyl isocyanate in the presence of triethylamine to form a nitrile oxide group. See C. Grundmann & P. Grϋnanger,

The Nitrile Oxides at 52-53 (Springer-Verlag 1971).

(2) Dehydrogenation of aldoximes yields nitrile oxide groups. Dehydrogenation may be carried out by treating the aldoxime with potassium ferric cyanide, a hypohalite, N-bromosuccinimide and alkali alkoxide or tertiary amine, or lead tetraacetate. See C. Grundmann & P. Grϋnanger, The Nitrile Oxides at 44-47

(Springer-Verlag 1971); and

(3) Treatment of hydroximic acid chlorides with base yields nitrile oxides. See

C. Grundmann & P. Grϋnanqer, The Nitrile Oxides at 47-51 (Springer-Verlag 1971). The hydroximic acid halide may be made by several different reaction sequences. For instance:

(a) react an aldehyde with hydroxylamine to form an aldoxime group and then chlorinate the aldoxime with chlorine or chloride ion in the presence of acid or base. See Breslow, U.S. Patent 3,717,560 (February 20, 1973). The aldehyde is preferably a benzylic aldehyde, (b) Add 2-chloroacetyl chloride to an aromatic ring by Friedel-Crafts addition in the presence of a Lewis acid, and react the pendant acetyl chloride group with nitric acid to form a hydroxymic acid chloride. See Breslow et al.,

"One-Component Sealant Based on 1,3-Dipoles," Vol. 32 J. App. Poly. Sci. at 4657 (1986). The previous reactions can be used to make nitrile oxide monomers from compounds which contain on average more than one sterically-hindered primary alkyl nitrate group, sterically-hindered aldehyde group, or sterically-hindered Freidel-Crafts addition site. Alternatively, the reactions can be used to make monomer precursors from a compound which contains at least one site forforming the nitrile oxide moiety, plus an additional reactive group (such as a hydroxyl group or a carboxylic acid group) which can react to form dimers or oligomers. An example of a suitable monomer precursor is 3,5-diethyl-4-(nitrile oxide)phenol, which can be made from 2,6-diethyl-4-hydroxybenzaldehyde. Unsaturated Monomers

The present invention also uses polyunsaturated monomers, which contain on average more than one unsaturated moiety per molecule. The unsaturated moieties each independently contain a carbon-carbon or carbon-nitrogen double or triple bond. The unsaturated moiety preferably contains a carbon-carbon double or triple bond. It more preferably contains a carbon-carbon double bond. It most preferably is a vinyl, allyl or acryloyl moiety.

The unsaturated moieties are preferably linked by one or more linking moieties (L), which are inert with respect to the nitrile oxide under reaction conditions. For example, the linking moiety (L) may optionally contain alkyl or cycloalkyl groups, heterocyclic aliphatic groups, heterocyclic or carbocyclic aromatic groups, ether oxygen or thioether sulfur moieties, carbonyl or sulfonyl moieties, ester moieties and combinations thereof. The linking moiety (L) may optionally be a simple, one-unit structure or an oligomer or co-oligomer which contains several repeating units. The unsaturated monomer is preferably represented by Formula V(a) or (b):

Formula V

(a) L-fl)_a

(b) R2-T-{L-T_7b-L-T-R2 wherein: Each L is a linking moiety as previously described.

Each J is any of {CR²=CR2₂), {C^≡CR2), {CR2 = NR2), {N =C = 0), {N = CR2₂), {X{CO)CR² = CR2₂) or {C≡N), wherein X is any of O, NR or S. Each J is pref erably {CR² = CR2₂) or {Xi CO}CR² = CR2₂). Each T is any of {CR2 = CR2₇, ^≡C₇ or R = N₇. Each T is preferably {CR² = CR2₇.

Each R2 is independently a hydrogen atom or a moiety which does not interfere with the reaction, such as a halogen, a Iower alkyl group, or an alkoxy group.

Each R2 is preferably hydrogen. "a" is a number of unsaturated moieties which averages greater than 1.

"b" is a number of repeating units which preferably averages from 0 to 25.

The unsaturated moiety must be available for reaction with the nitrile oxide group. When the nitrile oxide moiety is sterically-hindered, bulky substituents adjacent to unsaturated moiety may inhibit the nitrile oxide groups from reaching it to react. Preferably, the linking moiety (L) does not contain any hindering substituents bonded to the α-carbon, and more preferably does not contain any hindering substituents bonded to the α- or β-carbon (if the molecule contains a β-carbon atom), as illustrated in Formula VI:

Formula VI

In addition, when two unsaturated moieties are located very close together on a molecule, the reaction of a first unsaturated moiety with a nitrile oxide group may form substituents which hinder the reaction of the second unsaturated moiety. Preferably, the linking moiety (L) has an average formula weight of at least 12, more preferably at least 28, and most preferably at least 100.

The polyunsaturated monomer is preferably either approximately-difunctional or multi-functional:

Approximately-difunctional monomers contain on average more than one unsaturated moiety per molecule. They preferably contain on average at least .5 unsaturated moieties per molecule, more preferably at least 1.8 unsaturated moieties per molecule, and most preferably contain on average at least 2 unsaturated moieties per molecule. They contain on average no more than 2J unsaturated moieties per molecule and preferably contain on average no more than 2 unsaturated moieties per molecule. Multi-functional monomers contain on average more than 2.1 unsaturated moieties per molecule. They preferably contain on average at least 2.2 unsaturated moieties per molecule, more preferably at least 2.4 unsaturated moieties per molecule, and most preferably at least 2.8 unsaturated moieties per molecule. The maximum number of unsaturated moieties is limited by practical considerations, such as the structure of the linking group (L) and the intended use of the monomer. The multi-functional monomer preferably contains on average no more than 12 unsaturated moieties per molecule more preferably no more than 8 unsaturated moieties per molecule and most preferably no more than

5 unsaturated moieties per molecule.

The weight average molecular weight of each nitrile oxide monomer is less than 5000, preferably no more than 2500, more preferably no more than 1000, and most preferably no more than 500. The minimum molecular weight is not critical as long as the monomers contain the requisite number of reactive sites and will stay in a Iiquid composition. In most cases, the weight average molecular weight of the monomers is preferably at least 54 and more preferably at least 100.

Examples of lower-molecular-weight unsaturated monomers include: divinylbenzene, divinyl ether, diallyl adipate, diallyl amine, diallyl phthalate, diallyl isophthalate, triallyl amine, dicyclopentadiene, polyunsaturated fats and oils, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate. Examples of higher- molecular-weight unsaturated monomers include: acrylate esters of diols, triols and oligomeric polyols; poly(vinyl esters) and vinyl ester resins; acetylene oligomers; unsaturated polyester oligomers; allyl ethers of biphenols, bisphenols, novolac resins and other polyphenols; and polybutadiene oligomers. These examples are merely representative, and persons of ordinary skill can identify many other examples which will serve with equal efficiency.

Many unsaturated monomers are commercially available. The processes to make most others, such as polyacrylate esters and vinyl esters, are common knowledge within the chemical industries. A particularly useful process to make allyl ethers of polyphenols is described in Au et al., U.S. Ser. No. 08/363,129 (filed December 23, 1994). Compositions

Compositions of the present invention contain nitrile oxide monomers and polyunsaturated monomers. Nitrile oxide groups and unsaturated moieties within the reaction mixture undergo an addition reaction to form heterocyclic rings as illustrated in FormulaeVII(a)-(e): Formula VII

ketimine oxadiazoline

olefin isoxazoline

acetylene isoxazole

isocyanate R oxadiazolidinone

nitrile oxadiazole

wherein Q is a central moiety which is bonded to a second reactive group; and one of R², R³ or R⁴ is a linking group (L), which is bonded to a second reactive group. The heterocyclic rings link the monomers together to form a cross-linked thermoset polymer which contains Q; R², R³ and/or R⁴; and the heterocyclic ring.

In order to form the cross-linked thermoset system, either the nitrile oxide monomers or the polyunsaturated monomers or both should be multifunctional monomers, as previously described. For instance, the composition may contain multifunctional nitrile oxide monomers and approximately-difunctional polyunsaturated monomers; or approximately- difunctional nitrile oxide monomers and multifunctional polyunsaturated monomers; or multifunctional nitrile oxide monomers and multifunctional polyunsaturated monomers. The reaction mixture should contain more than a 0.5:1 ratio and less than a 2: 1 ratio of equivalents of nitrile oxide per equivalent of unsaturated site. The equivalent ratio of nitrile oxide per equivalent of unsaturated site is preferably at least 0.7: 1, highly preferably at least 0.8: 1 , more preferably at least 0.9: 1 , and most preferably at least 0.95: 1. The equivalent ratio of nitrile oxide per equivalent of unsaturated site is preferably no more than 1.3: 1 , highly preferably no more than 1.2: 1, more preferably no more than 1.1 : 1 , and most preferably at least 1.05: 1.

In many monomer systems, the reaction proceeds to completion within from 1 minute to 48 hours at room temperature. Therefore, the monomers containing nitrile oxide and monomers containing unsaturated moieties are preferably not mixed until shortly before the reaction mixture is to be used. Otherwise, it may be necessary to cool the reaction mixture or otherwise inhibit the reaction in order to prevent the composition from curing prematurely. Some reactions are highly exothermic, and solvent may be necessary to slow the reaction and moderate the temperature rise. The monomers are preferably chosen to minimize the need for solvent. The concentration of organic solvent is preferably minimized. It is preferably no more than 70 weight percent, more preferably no more than 50 weight percent and most preferably no more than 25 weight percent. Optimally, essentially no organic solvent is used.

Many variations may be practiced with the present compositions. For instance: (a) The composition may optionally contain mixtures of different nitrile oxide monomers and/or mixtures of different polyunsaturated monomers. (b) The composition may optionally further contain AB-monomers, which comprise both a stable nitrile oxide group and an unsaturated moiety. For instance, the composition may optionally contain 1-(nitrile oxide)-4-cyanobenzene. The composition preferably contains 0 to 50 weight percent of AB-monomers, more preferably 0 to 25 weight percent, and most preferably 0 to 10 weight percent. (c) The composition may optionally contain compounds which have either a single nitrile oxide group or a single unsaturated moiety. These monofunctional compounds act as chain terminators and end caps. The concentration of monofunctional compounds is preferably no more than 10 equivalent percent, more preferably no more than 5 equivalent percent, and most preferably no more than 2 equivalent percent, (d) Approximately-difunctional nitrile oxide monomers and approximately- difunctional polyunsaturated monomer may be reacted in non-stoichiometric quantities to make advanced, functionally-terminated resins or oligomer. The advanced resins are preferably made with a stoichiometric excess of nitrile oxide monomer, and are preferably terminated by nitrile oxide groups. The mixture preferably contains at least 1.2 equivalents of nitrile oxide per equivalent of unsaturated moiety and more preferably at least 1.5 equivalents. The maximum stoichiometry is not critical, although formulations containing more than

10 equivalents of nitrile oxide per equivalent of unsaturated moiety are not preferred.

The resulting advanced resin contains repeating units, which are divalent organic groups. The divalent organic groups have a description and preferred embodiments similar to the central moiety (Q) and linking group (L), as previously described. The advanced resin is terminated by two nitrile oxide groups on average. The weight average molecular weight of such advanced resins is preferably between 125 and 10,000, more preferably between 500 and 5000, and most preferably between 600 and 3000. The equivalent weight is preferably at least 60, highly preferably at least 100, more preferably at least 250 and most preferably at least 300. The equivalent weight is preferably no more than 5000, more preferably no more than 2500 and most preferably no more than 1500. The advanced resin may be used in formulations of the present invention as a nitrile oxide monomer. (e) A stoichiometric excess of approximately- difunctional nitrile oxide monomers may be prereacted with polyunsaturated monomers which contain on average more than two reactive unsaturated sites per molecule to make a cross-linking oligomer which contains on average more than two nitrile oxide groups. The cross-linking oligomer is preferably made using a reaction mixture which contains at least 1 mole of approximately-difunctional monomer per equivalent of unsaturated sites, more preferably at least 1.25 moles, and most preferably at least 1.5. The maximum ratio of approximately-difunctional monomer per equivalent of unsaturated sites is not critical, but in most cases is preferably no more than 20. (A formulation may tolerate slightly less than 1 mole of approximately-difunctional monomer per equivalent of unsaturated sites, but the molecular weight rapidly grows to a highly cross-linked polymer as the stoichiometry becomes more balanced.) The number average molecular weight of the cross-linking oligomer is preferably at least 500, more preferably at least 750; and most preferably at least 900. It is preferably no more than 10,000; more preferably no more than 5000; and most preferably no more than 2500. The weight per equivalent of nitrile oxide is preferably at least 180, more preferably at least 250 and most preferably at least

310. It is preferably no more than 2000, and more preferably no more than 1000. The average nitrile oxide functionality of the cross-linking oligomer preferably meets the limits previously defined for multifunctional monomers. Examples of a preferred cross-linking oligomers include the reaction product of at least 3 moles of TON-2 with trimethyolpropane triacrylate and the reaction product of at least 4 moles of TON-2 with pentaerythritol tetraacrylate. The cross¬ linking oligomer may be used as a nitrile oxide monomer in formulations of the present invention. (f) Either monomer may contain a mixture of approximately-difunctional monomers and multi-functional monomers, as long as at least one mixture of monomers averages multifunctional.

Useful formulations for a variety of applications may consist essentially of the monomers. However, for many applications the compositions of the present invention will preferably be formulated with known additives. For instance, depending upon the intended use, a formulation may optionally further contain:

(1) 0 to 70 weight percent fillers, chopped or unchopped fibers, and/or pigments;

(2) 0 to 5 weight percent each of stabilizers, flow modifiers, wetting agents, emulsifiers, suspension agents, and/or catalysts; and/or

(3) organic or inorganic solvents. The concentration of organic solvent is preferably minimized. It is preferably no more than 70 weight percent, more preferably no more than 50 weight percent, and most preferably no more than 25 weight percent. Optimally, essentially no organic solvent is used.

Formulations of the present invention may be used in common thermosetting applications. For instance, formulations of the present invention may be used to apply a protective coating to a substrate. Examples of suitable substrates include metal, wood, plastic, concrete or brick. The coating thickness is not critical, but is preferably between 1 micron and

1 mm. The coated substrate is subjected to temperatures sufficient to cure the formulation. The curing temperature is preferably 0°C to 150°C, more preferably 15°C to 100°C, and most preferably 20°C to 70°C. Another use for the formulations is in composite manufacturing. In the process:

(a) a fibrous substrate is impregnated with the curable matrix resin formulation; (b) optionally,

2 or more layers of prepreg are pressed together to laminate them; and (c) the entire structure is contacted and/or pressed together and optionally heated to cure. Substrates are well known and commercially available. They are preferably woven or unwoven cloth containing, for instance, glass fiber, aramid fiber, carbon fiber, or metal fiber. The prepreg substrate and the resulting laminate preferably contain 40 to 70 volume percent fiber and 30 to 60 volume percent matrix resin. The pressure for laminating and curing is usually at least 1 psi (6.8 kPa), more preferably at least 10 psi (68 kPa) and most preferably at least 100 psi (680 kPa). The maximum pressure is not critical, but the pressure is usually preferably no more than 1000 psi (6.8 MPa). The curing temperature is preferably at least 0°C, more preferably at least 15°C, and most preferably at least 20°C. The curing temperature is preferably no more than 150°C, and more preferably no more than 100°C. Another use for the formulations is in injection molding. In injection molding, a curable formulation is injected into a mold and then cured to form a shaped part. The mold may optionally contain a f iberous preform to support the molded part. (Such processes are also known as "resin transfer molding.") The monomers may optionally be mixed in a mix head immediately before they are injected into the mold, according to known procedures for reactive injection molding (RIM). The curing temperature is preferably at least 0°C, more preferably at least 15°C, and most preferably at least 20^GC. The curing temperature is preferably no more than 150°C, and more preferably no more than 100°C.

Other common uses for thermoplastic and thermosetting polymers and formulations of the present invention will be apparent to persons of ordinary skill in the art. The present invention is further illustrated in the following Examples.

Examples

The following examples are for illustrative purposes only. They should not be taken as limiting the scope of either the specification or the claims. Unless otherwise stated all parts and percentages are by weight. Example A - Preparation of Trifunctional Nitrile Oxide Monomer

A mixture containing 50 mL of dioxane, 2.82 g (0.0115 mols) of trimethylol propane triacrylate, and 8.54 g (0.035 mols) of TON-2 monomer was stirred ovemight at room temperature. The solvent was removed under reduced pressure to yield 11.3 g of the material in Formula VIII which was designated TMPT-NO. TMPT-NO is a viscous oil.

Formula VIII

Example B - Preparation of Difunctional Nitrile Oxide Monomer

The compound in Formula IX (MDNO) was obtained from

Professor M.M. Krayushkin, of the N.D. Zelinskii Institute of Organic Chemistry.

Formula IX

It was made bythe process of:

(1) reacting bis-(mesityl)methane with dichloromethyl methyl ether in the presence of a condensing agent, such as AICI3 or TiCI ₍ and a solvent - as described in

Yakubov et al., Vol. 7 Izvestiya Akademii Nauk SSSR at 1700-03 (July 1991) -to make the corresponding methylene-bis-(2,4,6-trimethyl-3-benzaldehyde) compound;

(2) reacting the product of Step (1) with hydroxylamine to form an aldoxime group; and

(3) reacting the aldoxime with chlorine or chloride ion in the presence of acid or base, as described in Breslow, U.S. Patent 3,717,560 (February 20, 1973).

Example 1 - Thermoset Curing of TMPT-NO

A 3.1 g (0.01 mol) quantity of bisallyl ether of bisphenol A was vigorously mixed into a mixture containing 1.77 g (0.005 mols) of TMPT-NO and 0.67 g (0.0025 mols) of TON-2. After 24 hours at room temperature, the product cured to yield an insoluble solid resin. Example 2 - Synthesis and Curing of an Advanced TON-2 Resin

A mixture containing 2.4 g (0.01 mol.) of TON-2, 1.6 g (0.0065 mol.) of diallyl phthalate, and 3 g of dioxane stood at room temperature for 70 hours. The reaction created a viscous Iiquid, which infrared analysis showed to contain significant nitrile oxide. Evaporation of solvent yielded a waxy solid, which was a chain extended TON-2.

A 0.33 g quantity of trimethylolpropane triacrylate was added to 3.5 g of the chain-extended TON-2/dioxane solution. The solution was stirred for 1 minute, and its viscosity began to rise. The mixture was poured and spread onto a glass plate and left overnight in a hood. The plate was heated in a vacuum oven at 100°C for 20 hours, and then left in the hood at room temperature for 1 week. Example 3 - Curing of MDNO Solution

A solution containing 0.5 g of MDNO, 0.33 g of triallyl ester of 1,2,4- benzenetricarboxylic acid, and 0.5 g of chloroform was mixed for 1 minute. At intervals over one hour, samples were cast upon a glass plate and the solvent was evaporated. In the initial samples, MDNO crystallized out, but after an hour it did not. After standing 25 hours, the remaining solution gelled.

Example 4 - Curing of MDNO Solution

A solution containing 0.33 g of MDNO, 0.7 g of trimethylolpropane triacrylate, and 4 g of chloroform was mixed for 30 seconds and cast on a glass plate. After 5 to 10 minutes, the cast film was pliable and leathery. The film was placed under vacuum for 2.5 days to remove solvent. The film was stiff, but bent 90° without breaking.

Example 5 - Curing MDNO with Flexibilized Unsaturated Compounds

A quantity of ethylene oxide or propylene oxide was reacted with trimethylolpropane under ordinary conditions to form alkoxylated triols. The triols were reacted with acrylic acid to make unsaturated resins. The ratio of alkylene oxide to equivalents of hydroxyl in the trimethylolpropane and the weight average molecular weight of the resulting unsaturated resin are shown in Table I.

The unsaturated resins were mixed with MDNO at room temperature in the proportions shown in Table I. After 35 minutes, all three mixtures were cast on glass plates. After 15 hours, all three samples were completely gelled. Samples B and C were removed from the glass. They formed flexible, elastic films which adhered strongly to themselves. After heating at 100°C under vacuum for 3 hours, Sample B was neither elastic nor self-adhesive, and

Sample C was elastic but not self-adhesive.

Table I

Reagent/Sample A B

Ethylene Oxide (mol./eq. OH) 0 2 . 33 4 . 66 Proplyene Oxide (mol./eq. OH) 2 0 0 Mw of unsaturated resin 644 604 912

MDNO (g) 0 . 501 0 . 501 0 . 501

Unsaturated resin (g) 0 . 644 0 . 627 0 . 912

Example 6 - Making a Composite

A 7.38 g quantity of diallyl phthalate was mixed into a solution containing 14.6 g of TON-2 and 20 g of methylene chloride. After a minute of mixing, an exotherm caused the solvent to boil. After 5 minutes, viscosity began to increase, and the mixture was put into an ice bath to cool. A 5 g quantity of solvent and 12.88 g of unsaturated resin from Example V(B) dissolved in 15 g of methylene chloride were added to the reaction mixture and stirred for 15 seconds. The mixture was pressed between 2 layers of woven fiberglass, which were between two MYLAR sheets. After 2 hours, the top MYLAR™ (Trademark of du Pont De Nemours & Company) sheet was removed. The composite was dried overnight in a hood, and then for 3 days at 85°C in a forced air oven. The resulting composite had a mean tensile strength of 25,000 psi and a mean tensile modulus of 2J 53,000 psi, as measured on an INSTRON tensile testing apparatus.

Example 7 - Making a Coating

A 5 g solution containing 20 weight percent polybutadiene (85 percent 1,2-vinyl having a weight average molecular weight of 3000) dissolved in toluene was mixed with 5 g of a solution which contained 20 weight percent TON-2 in toluene. The mixtures were cast on glass, and the toluene was permitted to evaporate. At 15 minutes at room temperature, a hard coating with high gloss was obtained. The coating did not dissolve or swell after 20 minutes in water or methyl ethyl ketone (MEK). It withstood 20 MEK double rubs without visible damage. Annealing at 50°C for 5 minutes gave a higher coating which still had high gloss.

Claims

CLAIMS:

1. A composition which comprises:

(b) at least one polyunsaturated monomer which:

(1) has a weight average molecular weight of no more than 5000; and

(2) contains on average more than one unsaturated moiety which contains a sterically-unhindered carbon-carbon or carbon-nitrogen double bond or triple bond, wherein the equivalent ratio of nitrile oxide to unsaturated moieties is more than 0.5: 1 and less than 2: 1, characterized in that the nitrile oxide monomers or the polyunsaturated monomers or both contain on average more than 2 reactive groups per molecule.

2. A composition as described in Claim 1 wherein the stable nitrile oxide groups in the nitrile oxide monomer are sterically-hindered.

3. A composition as described in Claim 2 wherein the nitrile oxide monomer contains at least one steric hindering moiety, which is an alkyl, alkoxy, aryl, aryloxy, ester, sulfonyl ester, or halogen moiety having a formula weight of 15 to 100, in a position suitable to provide steric hindrance to each nitrile oxide group.

4. A composition as described in Claim 3 wherein the nitrile oxide monomer contains a moiety represented by any of the following Formulae:

Formula IV

(a) (b) wherein A is a polyvalent moiety, x represents a number of substituents greater than 1, z represents a number of nitrile oxide groups greater than 1 , y is a number of Rⁱ groups which is 1 to 5, and each R¹ is a hydrogen atom or a steric hindering moiety selected such that at least one R¹ adjacent to each nitrile oxide group is a steric hindering moiety.

5. The composition as described in any of Claims 1 to 4 wherein the unsaturated moieties in the unsaturated monomer are any of: vinyl moieties, allyl moieties, acrylate moieties or methacrylate moieties.

6. The composition as described in any of the preceding Claims wherein the weight average molecular weight of the unsaturated monomer is from 54 to 1000.

7. A composition as described in any of Claims 1 to 6 wherein the nitrile oxide monomer contains on average 1.8 to 2J nitrile oxide groups per molecule, and the

5 polyunsaturated monomer contains on average at least 2J unsaturated moieties per molecule.

8. A composition as described in any of Claims 1 to 6 wherein the nitrile oxide monomer contains on average at least 2J nitrile oxide groups per molecule, and the polyunsaturated monomer contains on average 1.8 to 2.1 unsaturated moieties per molecule.

9. A composition as described in any of Claims 1 to 6 wherein the nitrile oxide 10 monomer contains on average at least 2J nitrile oxide groups per molecule, and the polyunsaturated monomer contains on average at least 2J unsaturated moieties per molecule.

10. A process to make an advanced bis-(nitrile oxide) resin by reacting an approximately-difunctional, stable nitrile oxide monomer with an approximately-difunctional polyunsaturated monomer, characterized in that the reaction mixture contains from 1.2 to 5 10 equivalents of nitrile oxide monomer per equivalent of unsaturated monomer.

11. An advanced nitrile oxide monomer which:

(1) contains on average more than 1 stable nitrile oxide group per molecule;

(2) contains a plurality of divalent organic groups linked by isoxazoline, isoxazole, oxadiazoiine, oxadiazole and/or oxadiazolinone groups; and

20 (3) has a weight per equivalent of nitrile oxide group of 100 to 5000.

12. A nitrile oxide cross-linking compound which:

(1) contains on average more than 2 stable nitrile oxide groups per molecule;

(2) is made by reacting a polyunsaturated monomer, which contains on average more than 2 unsaturated moieties per molecule, with at least 1 mole of

25 approximately-difunctional nitrile oxide monomer per equivalent of unsaturated moiety.

13. Use of a composition as described in any of Claims 1 to 9 or a composition containing nitrile oxide monomer as described in any of Claims 11 to 12 by:

(1) applying the composition in a thickness of no more than 2 mm to a substrate; and

30 (2) curing the composition to provide a cured coating.

14. Use of a composition as described in any of Claims 1 to 9 or a composition containing nitrile oxide monomer as described in any of Claims 11 to 12 by:

(1) impregnating a fibrous substrate with the composition;

(2) optionally, pressing two or more impregnated substrates together to form a 35 laminate; and

(3) curing the composition to form a matrix composite.

15. Use of a composition as described in any of Claims 1 to 9 or a composition containing nitrile oxide monomer as described in any of Claims 11 to 12 by:

(1) injecting the composition into a mold; and

(2) curing the composition to form a molded article.