Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1995-04-14
1997-01-21
Dodson, Shelley A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528 48, 528 53, 528125, 528128, 528171, 528172, 528173, 528174, 528185, 528188, 528220, 528229, 528310, 528342, 528350, 525422, C08G 7310, C08G 6908
Patent
active
055960731
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polyimide-based solutions which can be directly spun and shaped.
It also relates to a process for producing these solutions and to a process for the spinning thereof.
2. Background Discussion
The preparation of polyimides from diisocyanates and acids or anhydrides has been known for a long time.
Thus, FR 2,107,998 describes the preparation of polyimides resulting from 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and diisocyanates. However, such a reaction requires an extremely long reaction time which makes this process expensive for industrial application.
To reduce the reaction time between diisocyanates and dianhydrides, while producing polymers with a sufficient molecular weight to make possible their conversion, and soluble in the usual solvents according to U.S. Pat. No. 4,001,186, the polycondensation has been carried out in the presence of catalysts such as alkali metal methoxides.
EP 0,235,388 also recommends the use of a catalyst, alkali metal fluoride, optionally in combination with a quaternary onium salt, to produce gel-free polyimides.
However, the presence of catalysts is not a favourable component in the production of polyimides, because, in order to produce shaped articles, in particular yarns having good characteristics, the catalyst must be removed before conversion or spinning and this removal is difficult to carry out straightforwardly. Furthermore, for costs reasons, recycling of the catalyst is necessary industrially.
SUMMARY OF THE INVENTION
It has now been found that it was possible to produce soluble polyimides having a high molecular weight, in the form of solutions which can be directly shaped and spun, without requiring either a catalyst or a long reaction time. More particularly, the present invention relates to clear solutions which can be directly spun and shaped, containing: from 5 to 35% by weight of a polyimide comprising repeating units of formula: ##STR1## in which Ar represents a tetravalent group of formula ##STR2## with X: monovalent radical, identical or different, such as H, --CH.sub.3, --CF.sub.3, ##STR3## or none Y=CO, O, SO.sub.2, S, C(CH.sub.3).sub.2, CH.sub.2 or C(CF.sub.3).sub.2 divalent radical or none, dimethylalkyleneurea (DMAU), with a pH.ltoreq.7.
The group Ar preferably represents a group of formula: ##STR4##
Ar1 preferably comprises at least 50% of tolylene groups.
Such polymers furthermore have a low polydispersity index, which corresponds to a narrowing of the molecular mass distribution. The polydispersity index (I) of the polyimides according to the invention is generally approximately 2 or even less.
The present invention also relates to a process for producing clear, polyimide-based solutions which can be directly spun or shaped by a polycondensation reaction in anhydrous dimethylalkyleneurea (DMAU), with a pH.ltoreq.7, in the absence of catalyst, at a temperature between 150.degree. C. and the boiling point of the solvent, the duration of the reaction being less than or equal to 6 hours, preferably less than or equal to 5 hours, and then dilution of the polymer in anhydrous dimethylalkyleneurea, with a pH.ltoreq.7. The polymer concentration before dilution is generally between 10 and 40%, preferably 15 and 35%, by weight and the final concentration in the solvent is between 5 and 30%.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The solutions according to the present invention are prepared by reaction in anhydrous DMAU, with a pH.ltoreq.7, in substantially stoichiometric proportions, between: aromatic group, preferably a group consisting of at least 50% of tolylene groups, ##STR5## in which Ar represents a tetravalent radical of formula such as: ##STR6## X representing an identical or different monovalent radical such as: ##STR7## with A and Y identical or different divalents of formula: O, S, or CO, SO.sub.2, C(CH.sub.3).sub.2, CH.sub.2, C(CF.sub.3).sub.2 or none, it not being possible for A not to exist, at a temperature between 150.deg
REFERENCES:
patent: 4795795 (1989-01-01), Kouno et al.
Chemical Abstracts, vol. 111, No. 18, 30 Oct. 1989, Columbus, Ohio, US; Abstract No. 154646n, "Preparation of heat-resistant polyamides or polyimides" see Abstract & JP, A. 01054019 (Mitsui) 1 Mar. 1989.
Michaud Philippe
Russo Jean
Cole Watson
Dodson Shelley A.
Hampton-Hightower P.
S.N.C. Kermel
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