Crosslinking imidophenylamines

Abstract: Solvent resistance in polyimide, polyamide, and other resins can be improved by capping these resins with mono- or difunctional crosslinking end caps. Imidophenylamines of the general formula: R₁ = lower alkyl, lower alkoxy, aryl, aryloxy, substituted aryl, substituted alkyl, halogen, or mixtures thereof; Me = methyl; T = allyl or methallyl; i = 1 or 2; j = 0, 1, or 2; and G = -CH₂ , -O-, -S-, or -SO₂-, comprise a new family of end cap monomers that are reactants in the synthesis of crosslinking, solvent resistant oligomers.

Description: Technical Field The present invention relates to imidophenylamines of the general formula: wherein Y = wherein R₁ = lower alkyl, lower alkoxy, aryl, aryloxy, substituted aryl, substituted alkyl (either including hydroxyl or halo-substituents), halogen, or mixtures thereof; Me = methyl; T = allyl or methallyl; i = 2; j = 0, 1, or 2; and G = -CH₂-, -O-, -S-, or -SO₂-. These imidophenylamines are useful in the preparation of solvent resintant advanced composites, such as polyamides or polyimides, when they are condensed into the oligomer to form crosslinking end caps. Background of the Invention Recently, chemists have sought to synthesize oligomers for high performance advanced composites suitable for aerospace applications. These composites should exhibit solvent resistance, toughness, impact resistance, processibility, and strength, and should be thermoplastic. Oligomers and composites that have thermo-oxidative stability and, accordingly, can be used at elevated temperatures are particularly desirable. While epoxy-based composites are suitable for many applications, their brittle nature and susceptibility to degradation make them inadequate for many aerospace applications, especially those applications which require thermally stable, tough composites. Accordingly, research has recently focused on polyimide composites to achieve an acceptable balance between thermal stability, solvent resistance, and toughness. Still the maximum temperatures for use of the polyimide composites, such as PMR-15, are about 600-625°F (316°C-329°C), since they have glass transition temperatures of about 690°F (366°C). There has been a progression of polyimide sulfone compounds synthesized to provide unique properties or combinations of properties. For example, Kwiatkowski and Brode synthesized maleic capped linear polyarylimides as disclosed in U.S. Patent 3,839,287. Holub and Evans synthesized maleic or nadic capped imido-substituted polyester compositions as disclosed in U.S. Patent 3,729,446. We synthesized thermally stable polysulfone oligomers as disclosed in U.S. Patent 4,476,184 or U.S. 4,536,559, and have continued to make advances with polyetherimidesulfones, polybenzoxazolesulfones, polybutadienesulfones, and "star" or "star-burst" multidimensional oligomers. We have shown surprisingly high glass transition temperatures yet reasonable processibility and desirable physical properties in many of these oligomers and their composites. Polybenzoxazoles may be used at temperatures up to about 750-775°F (399°C-413°C), since these composites have glass transition temperatures of about 840°F (449°C). Some aerospace applications need composites which have even higher use temperatures while maintaining toughness, solvent resistance, processibility, formability, strength, and impact resistance. Multidimensional oligomers have superior processibility over some advanced composite oligomers since they can be handled at lower temperatures. Upon curing, however, the phenylimide end caps crosslink so that the thermal resistance of the resulting composite is markedly increased with.only a minor loss of stiffness, matrix stress transfer (impact resistance), toughness, elasticity, and other mechanical properties. Glass transition temperatures above 950°F(510°C) are achievable. Commercial polyesters, when combined with well-known diluents, such as styrene, do not exhibit satisfactory thermal and oxidative resistance to be useful for aircraft or aerospace applications. Polyarylesters are often unsatisfactory, also, since the resins often are semicrystalline which may make them insoluble in laminating solvents, intractable in fusion, and subject to shrinking or warping during composite fabrication. Those polyarlyesters that are soluble in conventional laminating solvents remain so in composite form, thereby limiting their usefulness in structural composites. The high concentration of ester groups contributes to resin strength and tenacity, but also makes the resin susceptible to the damaging effects of water absorption. High moisture absorption by commercial polyesters can lead to distortion of the composite when it is loaded at elevated temperature. High performance, aerospace, polyester advanced composites, however, can be prepared using crosslinkable, end capped polyester imide ether sulfone oligomers that have an acceptable combination of solvent resistance, toughness, impact resistance, strength, processibility, formability, and thermal resistance. By including Schiff base (-CH=N-), imidazole, thiazole, or oxazole linkages in the oligomer chain, the linear, advanced composites formed with polyester oligomers can have semiconductive or conductive properties when appropriately doped. Conductive and semiconductive plastics have been extensively studied ( see. e.g. , U.S. Patents 4,375,427; 4,338,222; 3,966,987; 4,344,869; and 4,344,870), but these polymers do not possess the blend of properties which are essential for aerospace applications. That is, the conductive polymers do not possess the blend of (1) toughness, (2) stiffness, (3) elasticity, (4) processibility, (5) impact resistance (and other matrix stress transfer capabilities), (6) retention of properties over a broad range of temperatures, and (7) high temperature resistance that is desirable on aerospace advanced composites. The prior art composites are often too brittle. DE-A 26 26795 relates to imidyl compounds having a specific formula and suitable for manufacture of polymers which can be crosslinked by a light. According to the invention, polymers of this type are suited for carrying our photochemical processes and are photochemically more sensitive-compared to known polymers. The linear arms of thermally stable multidimensional oligomers having semiconductive or conductive properties when doped with suitable dopants contain conductive linkages, such as Schiff base (-N=CH-) linkages, between aromatic groups. Sulfone and ether linkages are interspersed in the arms. Each arm is terminated with a mono- or difunctional end cap to allow controlled crosslinking upon heat-induced or chemically-induced curing. Summary of the Invention According to one aspect of the invention, there are provided crosslinking imidophenylamines of the general formula: wherein Y = wherein R₁ = lower alkyl, lower alkoxy, aryl, aryloxy, substituted aryl, substituted alkyl, halogen, or mixtures thereof, wherein the substituents for alkyl or aryl are selected from the group consisting of hydroxyl or halogeno; i = 2; Me = methyl; T = allyl or methallyl; j = 0, 1, or 2; and G = -CH₂-, -O-, -S-, or -SO₂-. Preferably, j = 1 and G = -CH₂-. The highest thermal stability for an oligomer or composite that contains the end cap can be attained if the cap is: This family can be prepared from the corresponding imidophenyl acid halide of the formula: by reacting the acid halide with ammonia to form an acid amide followed by rearrangement of the acid amide to the amine. The imidophenyl acid halide can be prepared, in accordance with the process described in United States Patent 4,604,437, by reacting the corresponding anhydride of the formula: with a corresponding amine of the formula: This family of imidophenylamines can be used in condensation reactions to form crosslinking, linear or multidimensional oligomers, particularly polyamides or polyimides. For example, the imidophenylamines can be condensed with diacide halides and diamines to form (among others) polyamides of the general formula: Ar[CONH-P-NHCO-Q-CONH-E] n; Ar[CONH-E] n ; or Ar[NHCO-Q-CONH-E] According to another aspect of the invention, there is provided a method for making an wherein Y = imidophenylamine of the general formula: R₁ = lower alkyl, lower alkoxy, aryl, aryloxy, substituted aryl, substitued alkyl, halogen, or mixtures thereof, wherein the substituents for alkyl or aryl are selected from the group consisting of hydroxyl or halogeno; Me = methyl; T = allyl or methallyl; i = 2; j = 0, 1, or 2; and G = -CH₂-, -O-, -S-, or SO₂-. comprising the steps of: (a) reacting an acid halide of the formula: wherein X = halogen, with ammonia to form an acid amide; and (b) rearranging the acid amide to the amine. Best Mode Contemplated for Carrying Out the Invention Crosslinking imidophenylamines useful in advanced composites have the general formula: wherein Y = wherein R₁ = lower alkyl, lower alkoxy, aryl, aryloxy, substituted aryl, substituted alkyl, halogen, or mixtures thereof; Me = methyl; T = allyl or methallyl; i = 2; j = 0, 1, or 2; and G = -CH₂-, -O-, -S-, or -SO₂-. The unsaturation of this family of amines can be thermally or chemically activated after condensing the amine into an oligomer to form crosslinking stability on the cured composite, significantly increasing the solvent resistance of the composites. Imidophenol analogs of these amines are described and claimed in our United States Patent Number 4,661,604. These imidophenylamines can be prepared by reacting the corresponding imidophenyl acid halide of the general formula: with ammonia to form an acid amide. Rearrangement of the acid amide yields the desired amine. The amine halide can be prepared from the corresponding acid on the presence of SOCl₂. As described in United States" Patent 4,604,437, the acid is readily prepared by reacting the corresponding anhydride with either aminobenzoic acid or diaminobenzoic acid. Those skilled in the art will be able to prepare the necessary anhydrides by conventional syntheses. Preferably j = 1, G = -CH₂, and The substituents on the alkyl or aryl radical are halo- or hydroxyl-radicals. In accordance with the preferred embodiments, then, the imidophenylamines are: or The monomers present a wide range of activation temperatures and, accordingly, provide the desirable end caps for a wide range of curable oligomers. If the end cap is activated near the flow temperature of the polymeric backbone, the best results are obtained.

Claims: A crosslinking end cap monomer selected from the group consisting of wherein Y = R₁ = lower alkyl, lower alkoxy, aryl, aryloxy, substituted alkyl, substituted aryl, halogen, or mixtures thereof, wherein the substituents for alkyl or aryl are selected from the group consisting of hydroxyl or halogeno; Me = methyl; T = allyl or methallyl; i = 2; j = 0, 1, or 2; and G = -CH₂-, -O-, -S-, or SO₂-. The monomer of claim 1 wherein R₁ = phenyl and j = 1. The monomer of claim 1 wherein Y = The monomer of claim 1 wherein Y = The monomer of claim 1 wherein Y = The monomer of claim 1 wherein Y = The monomer of claim 1 wherein Y = The monomer of claim 1 wherein Y = The monomer of claim 4 wherein G = -CH₂-, R₁ = Phenyl, and j = 1. The monomer of claim 7 and wherein R₁ = phenyl, j = 1, and Y has the formula: The monomer of claim 4 wherein R₁ = phenyl and j = 1. A crosslinking end cap monomer as claimed in claim 1 having the formula: A method for making an imidophenylamine of the general formula: wherein Y = R₁ = lower alkyl, lower alkoxy, aryl, aryloxy, substituted alkyl, substituted aryl, halogen, or mixtures thereof, wherein the substituents for alkyl or aryl are selected from the group consisting of hydroxyl or halogeno; Me = methyl; T = allyl or methallyl; i = 2; j = 0, 1, or 2; and G = -CH₂-, -O-, -S-, or SO₂-. comprising the steps of: (a) reacting an acid halide of the formula: wherein X = halogen, with ammonia to form an acid amide; and (b) rearranging the acid amide to the amine.

Inventors: LUBOWITZ HYMAN R, SHEPPARD CLYDE H, LUBOWITZ, HYMAN R., SHEPPARD, CLYDE H.
Applicants: BOEING CO, THE BOEING COMPANY
Application year: 1988
Main classification: C07D209
IPC codes: C08G69, C07D491, C07D209, C07D495, C08G73, C07D207, C08K5