# US 5,705,574 A · Method for making a polyimide blend

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- Number: US 5,705,574 A
- Document ID: US5705574A
- Status: Granted
- Kind: A
- Application number: 08/462,483
- Filed: 1995-06-05
- Granted: 1998-01-06
- Earliest claimed: 1983-09-27
- Assignees: The Boeing Company
- Inventors: Hyman R. Lubowitz; Clyde H. Sheppard
- Web page: https://patentgrep.com/patent/US5705574A

## CPC

- C08G 73/1014: {in the form of (mono)anhydrid}
- C08G 73/1064: {containing sulfur}
- C08G 73/1067: {Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound}
- C08G 73/1071: {Wholly aromatic polyimides containing oxygen in the form of ether bonds in the main chain}
- C08G 73/14: Polyamide-imides
- C08L 79/08: Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)

## Abstract

Polyimide oligomers include (1) linear, mono-functional crosslinking oligomers prepared by condensing a monoanhydride end cap with a diamine that includes alternating ether and "sulfone" (--SO.sub.2 --, --S--, --CO--, --(CF.sub.3).sub.2 C--, or --(CH.sub.3).sub.2 C--) linkages connecting alternating aromatic radicals and with a dianhydride (or dianhydride mixture), particularly the unsaturated, aliphatic dianhydride commonly known as MCTC; (2) linear, mono- or difunctional crosslinking oligomers prepared by condensing an amine end cap with a diamine and a dianhydride; and (3) multidimensional, crosslinking oligomers having an aromatic hub and at least three radiating arms connected to the hub, each arm including a crosslinking end cap at its distal end and at least one imide linkage. Blends, prepregs, and composites can be prepared from the oligomers. The blends are prepared by mixing miscile solutions of the oligomer and a noncrosslinking polyimide polymer to forma lacquer which is then swept out into a fabric to form a polyimide blend prepreg. Multidimensional oligomers can be prepared using etheranhydride intermediates or etheramine intermediates formed by reacting a suitable hub with nitrophthalic anhydride or aminophenol.

## Claims

### Claim 1

A method of making prepreg with a blend of polyimides, the blend having a polyimide oligomer and a polyimide polymer, the oligomer having crosslinking terminal end caps, the polymer not having crosslinking terminal end caps, comprising the steps of:
(a) forming a first solution of the oligomer in a first solvent;
(b) forming a polymer solution of the polymer in a solvent that is the same as the first solvent or miscible with the first solvent and in which the oligomer also is soluble;
(c) mixing the first solution and polymer solution to form a lacquer; and
(d) applying the lacquer to a fabric to sweep out the blend into the fabric and to make a prepreg.

### Claim 2 (depends on 1)

The prepreg obtained by the process of claim 1.

### Claim 3 (depends on 2)

The method of claim 2 wherein the oligomer includes an end cap selected from the group consisting of: ##STR36## wherein R.sub.1 =lower alkyl, lower alkoxy, aryl, substituted alkyl, aryloxy, or halogen;
j=0,1 or 2 ;
Me=methyl;
G=--SO.sub.2 --, --CH.sub.2 --, --S--, or --O--; and
E=methallyl or allyl.

### Claim 4 (depends on 1)

The method of claim 1, wherein the first solvent is the same solvent as the second solvent.

### Claim 5 (depends on 1)

The method of claim 1 wherein the oligomer is linear.

### Claim 6 (depends on 1)

The method of claim 1 wherein the oligomer has multidimensional morphology.

### Claim 7 (depends on 3)

The method of claim 3 wherein the oligomer is linear and wherein the oligomer has two end caps at each end of its backbone.

### Claim 8 (depends on 3)

The method of claim 3 wherein the oligomer is multidimensional and wherein the oligomer has two end caps at the end of each arm.

### Claim 9 (depends on 1)

The method of claim 1 wherein the fabric includes carbon fiber.

### Claim 10 (depends on 1)

The method of claim 1 wherein the laquer contains substantially an equimolar mixture of the oligomer and polymer.

### Claim 11 (depends on 1)

The method of claim 1 wherein the oligomer and polymer have the same repeating diamine and dianhydride residues in their backbones.

### Claim 12 (depends on 10)

The product of the method of claim 10.

### Claim 13 (depends on 2)

A composite made by curing the product of claim 2.

### Claim 14 (depends on 9)

A composite made by curing the product of claim 9.

### Claim 15

A method of making a prepreg with a blend of polyimides, the blend having a polyimide oligomer and a polyimide polymer, the oligomer having crosslinking terminal end caps, the polymer not having crosslinking terminal end caps, comprising the steps of:
(a) forming a first solution of the oligomer in a first solvent;
(b) forming a polymer solution of the polymer in a solvent that is the same as the first solvent or miscible with the first solvent and in which the oligomer also is soluble;
(c) mixing the first solution and the polymer solution to form a lacquer; and
(d) applying the lacquer to a fiber reinforcement to form a prepreg.

### Claim 16 (depends on 15)

A prepreg obtained by the method of claim 15.