Process for producing a tetracarboxylic acid anhydride having disiloxane linkage

Claim 2

1-(2,3-Dicarboxyphenyl)-3-(3,4-dicarboxy­phenyl)-1,1,3,3-tetramethyldisiloxane dianhydride.

Claim 3

A process for producing 1-(2,3-dicarboxy­phenyl)-3-(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyl­disiloxane dianhydride which comprises dispersing a mixture of 1,3-bis(dicarboxy­phenyl)-1,1,3,3-tetramethyldisiloxane dianhydrides represented by the formula: wherein each acid anhydride group is indepedently bonded at the 2,3-positions or the 3,4-position, in an ether, removing deposited crystals of 1,3-bis(3,4-­dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride from the ether dispersion, and adding a liquid alkane to the ether dispersion to deposit crystals of the desired 1-(2,3-dicarboxy­phenyl)-3-(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyl­disiloxane dianhydride.

Claim 4

A process for producing 1-(2,3-dicarboxy­phenyl)-3-(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyl­disiloxane dianhydride which comprises dispersing a mixture of 1,3-bis(dicarboxy­phenyl)-1,1,3,3-tetramethyldisiloxane dianhydrides represented by the formula: wherein each acid anhydride group is indepedently bonded at the 2,3-positions or the 3,4-position, in an ether, removing deposited crystals of 1,3-bis(3,4-­dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride from the ether dispersion, and adding a liquid alkane to the ether dispersion to deposit crystals of the desired 1-(2,3-dicarboxy­phenyl)-3-(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyl­disiloxane dianhydride.

Claim 5

A process according to Claim 2, wherein the ether is diethyl ether, diisopropyl ether or di-n-propyl

Claim 6

A process according to claim 2 or claim 3 wherein the ether is used in an amount of 100 to 500% by weight based on the weight of compounds of formula (II).

Claim 7

A process according to any claims 2 to 4 wherein the liquid alkane has from 5 to 15 carbon atoms.

Claim 8

A process according to claim 5 wherein the liquid alkane is n-hexane, cyclohexane, n-pentane, n-heptane, or 2,2,4-trimethylpentane.

Claim 9

A process according to any one of claims 2 to 6 wherein the liquid alkane is used in an amount of 10 to 100% by weight based on the ether dispersion after removal of crystals of 1,3-bis(3,4-dicarboxyphenyl)-­1,1,3,3-tetramethyldisiloxane dianhydride.

Claim 10

Use of 1-(2,3-dicarboxyphenyl)-3,4-­dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride as an epoxy resin curing agent.

Claim 11

Use of 1-(2,3-dicarboxyphenyl)-3,4-­dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride as an epoxy resin curing agent.

Claim 12

Use of 1-(2,3-dicarboxyphenyl)-3-(3,4-­dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride as an epoxy resin curing agent together with 1,3-bis(3,4-­dicarboxyphenyl)-1,1,3,3-tetramethyl-disiloxane dianhydride.

Claim 13

Use of 1-(2,3-dicarboxyphenyl)-3-(3,4-­dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride as an epoxy resin curing agent together with 1,3-bis(3,4-­dicarboxyphenyl)-1,1,3,3-tetramethyl-disiloxane dianhydride.

Claim 14

A curable composition comprising an epoxy resin and 1-(2,3-dicarboxyphenyl)-3-(3,4-dicarboxyphenyl-­1,1,3,3-tetramethyldisiloxane dianhydride and optionally further comprising 1,3,-bis(3,4-dicarboxyphenyl)-1,1,3,3-­tetramethyl-disiloxane dianhydride.

Claim 15

A curable composition comprising an epoxy resin and 1-(2,3-dicarboxyphenyl)-3-(3,4-dicarboxyphenyl-­1,1,3,3-tetramethyldisiloxane dianhydride and optionally further comprising 1,3,-bis(3,4-dicarboxyphenyl)-1,1,3,3-­tetramethyl-disiloxane dianhydride.