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Polyimide nonwoven fabric and process for production thereof

  • US 9,394,638 B2
  • Filed: 06/19/2007
  • Issued: 07/19/2016
  • Est. Priority Date: 06/22/2006
  • Status: Expired due to Fees
First Claim
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1. A process for producing a non-woven fabric, comprising the steps of:

  • preparing a polyamic acid by polycondensation of reactants consisting of an aromatic tetracarboxylic acid anhydride and an aromatic diamine having a benzoxazole structure in one or more organic solvents, and electro-spinning the polyamic acid to form a polyimide precursor fiber bundle; and

    imidizing the polyimide precursor fiber bundle to obtain the non-woven fabric having a fiber diameter in the range of 0.001 μ

    m to 100 nm and having a coefficient of linear expansion in the range of −

    6 ppm/°

    C. to 14 ppm/°

    C.;

    wherein the aromatic tetracarboxylic acid anhydride is selected from the group consisting ofpyromellitic anhydride,3,3′

    ,4,4′

    -biphenyltetracarboxylic anhydride,4,4′

    -oxydiphthalic anhydride,3,3′

    ,4,4′

    -benzophenonetetracarboxylic anhydride,3,3′

    ,4,4′

    -diphenylsulfonetetracarboxylic anhydride, and2,2′

    -bis[4-(3,4-dicarboxyphenoxy)phenyl]propanoic anhydride,the aromatic diamine is selected from the group consisting of;

    5-amino-2-(p-aminophenyl)benzoxazole,6-amino-2-(p-aminophenyl)benzoxazole,5-amino-2-(m-aminophenyl)benzoxazole,6-amino-2-(m-aminophenyl)benzoxazole,2,2′

    -p-phenylenebis(5-aminobenzoxazole),2,2′

    -p-phenylenebis(6-aminobenzoxazole),1-(5-aminobenzoxazolo)-4-(6-aminobenzoxazole)benzene,2,6-(4,4′

    -diaminodiphenyl)benzo[1,2-d;

    5,4-d′

    ]bisoxazole,2,6-(4,4′

    -diaminodiphenyl)benzo[1,2-d;

    4,5-d′

    ]bisoxazole,2,6-(3,4′

    -diaminodiphenyl)benzo[1,2-d;

    5,4-d′

    ]bisoxazole,2,6-(3,4′

    -diaminodiphenyl)benzo[1,2-d;

    4,5-d′

    ]bisoxazole,2,6-(3,3′

    -diaminodiphenyl)benzo[1,2-d;

    5,4-d′

    ]bisoxazole, and2,6-(3,3′

    -diaminodiphenyl)benzo[1,2-d;

    4,5-d′

    ]bisoxazole,the polyamic acid has a reduced viscosity of 3.0 dl/g or more, andthe electro-spinning is carried out under the following conditions;

    the spinning nozzle has an inside diameter in the range of from 0.1 mm to 3 mm,the applied voltage is in the range of 10 kV to 15 kV, andthe distance between the electrodes is in the range of 5 cm to 20 cm.

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