Thermosetting solution composition and prepreg

1. A process for preparing a thermosetting solution composition comprising a biphenyltetracarboxylic acid compound containing at least 15 mol % of a partial lower aliphatic alkyl ester of 2,3,3′,4′-biphenyltetracarboxylic acid and/or a partial lower aliphatic alkyl ester of 2,2′,3,3′-biphenyltetracarboxylic acid, an aromatic diamine compound in a molar amount larger than a molar amount of the biphenyltetracarboxylic acid compound, said aromatic diamine compound being selected from the group consisting of p-phenylenediamine, m-phenylenediamine, 1,3-bis(4-aminophenoxy)benzene and a mixture thereof, and a partial lower aliphatic alkyl ester of 4-(2-phenylethynyl)phthalic acid compound in a molar amount as much as 1.8-2.2 times a molar amount corresponding to a difference between the molar amount of the aromatic diamine compound and the molar amount of the biphenyltetracarboxylic acid compound dissolved in an organic solvent comprising a lower aliphatic alcohol, in which a total amount of the biphenyltetracarboxylic acid compound, 4-(2-phenylethynyl)phthalic acid compound and aromatic diamine compound is in the range of 30 to 80 wt. % based on an amount of the thermosetting solution composition, which comprises the steps of:

placing a biphenyltetracarboxylic acid compound containing at least 15 molar % of 2,3,3′,4′-biphenyltetracarboxylic dianhydride and/or 2,2′,3,3′-biphenyltetracarboxylic dianhydride, and 4-(2-phenylethynyl)phthalic anhydride in the organic solvent, to give a suspension;

heating the suspension to give a solution in which the partial lower aliphatic alkyl ester of the biphenyltetracarboxylic acid compound and the partial lower aliphatic alkyl ester of 4-(2-phenylethynyl)phthalic acid are dissolved; and

mixing the aromatic diamine compound with the solution obtained above.

2. The process of claim 1 , in which each of the partial lower aliphatic alkyl esters is methyl ester and the lower aliphatic alcohol is methanol.

3. The process of claim 1 , in which each of the partial lower aliphatic alkyl ester is ethyl esters and the lower aliphatic alcohol is ethanol.

4. The process of claim 1 , in which the aromatic diamine compound is p-phenylenediamine, 1,3-bis(4-aminophenoxy)-benzene or a mixture thereof.

5. The process of claim 1 , in which the aromatic diamine compound comprises a mixture of p-phenylenediamine and 1,3-bis(4-aminophenoxy)benzene wherein p-phenylenediamine is present in an amount of 50 to 70 molar %.

6. The process of claim 1 , in which a total amount of the biphenyltetracarboxylic acid compound, the aromatic diamine compound, and 2-(2-phenylethynyl)phthalic acid compound is in the range of 30 to 80 wt. %, per the amount of the solution composition.

7. A process for preparing a thermosetting solution composition comprising a biphenyltetracarboxylic acid compound containing at least 15 mol % of a partial methyl ester of 2,3,3′,4′-biphenyltetracarboxylic acid and/or a partial methyl ester of 2,2′,3,3′-biphenyltetracarboxylic acid, an aromatic diamine compound in a molar amount larger than a molar amount of the biphenyltetracarboxylic acid compound, said aromatic diamine compound being selected from the group consisting of p-phenylenediamine, m-phenylenediamine, 1,3-bis(4-aminophenoxy)benzene and a mixture thereof, and a partial methyl ester of 4-(2-phenylethynyl)phthalic acid compound in a molar amount as much as 1.8-2.2 times a molar amount corresponding to a difference between the molar amount of the aromatic diamine compound and the molar amount of the biphenyltetracarboxylic acid compound dissolved in ethanol, in which a total amount of the biphenyltetracarboxylic acid compound, 4-(2-phenylethynyl)phthalic acid compound and aromatic diamine compound is in the range of 30 to 80 wt. % based on an amount of the thermosetting solution composition, which comprises the steps of:

placing a biphenyltetracarboxylic acid compound containing at least 15 molar % of 2,3,3′,4′-biphenyltetracarboxylic dianhydride and/or 2,2′,3,3′-biphenyltetracarboxylic dianhydride, and 4-(2-phenylethynyl)phthalic anhydride in methanol, to give a suspension;

heating the suspension to give a methanol solution in which the partial methyl ester of the biphenyltetracarboxylic acid compound and the partial methyl ester of 4-(2-phenylethynyl)phthalic acid are dissolved;

mixing the aromatic diamine compound with the solution obtained above, whereby giving a thermosetting methanol solution in which the partial methyl ester of the biphenyltetracarboxylic acid compound, the partial methyl ester of 4-(2-phenylethynyl)phthalic acid and the aromatic diamine compound are dissolved;

drying the thermosetting methanol solution, whereby giving a thermosetting powdery composition; and

dissolving the thermosetting powdery composition in ethanol, whereby giving a thermosetting solution composition.

8. The process of claim 7 , in which the aromatic diamine compound is p-phenylenediamine, 1,3-bis(4-aminophenoxy)benzene or a mixture thereof.

9. The process of claim 7 , in which the aromatic diamine compound comprises a mixture of p-phenylenediamine and 1,3-bis(4-aminophenoxy)benzene wherein p-phenylenediamine is present in an amount of 50 to 70 molar %.