Tris-(cyanoto)-s-triazines and anisotropic duroplastic networks

Details Tris-(cyanoto)-s-triazines and anisotropic duroplastic networks Tris-(cyanoto)-s-triazines and anisotropic duroplastic networks

1996-05-01

1998-03-03

Nagumo, Mark

Compositions

Liquid crystal compositions

544219, 528423, 528422, 528149, C08G 7308, C07D25104

Patent

active

057230676

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention is directed to a process for the production of anisotropic duroplastic networks by polycyclotrimerization of polycyanates in the melt and to the products obtained by this process. Where appropriate, the polycyclotrimerization of the invention takes place in the presence of catalysts, comonomers and other conventional additives.


BACKGROUND OF THE INVENTION

The relevant prior art is given, e.g., by EP-A-0 409 069 (Hefner, et al.), in which Mesogenic bifunctional cyanic acid esters are described. The majority of the process products described therein are isotropic, with only one example concerning the production of an anisotropic network (op. cit., page 66, lines 41ff)). According to that example, monomers of a dicyanate of 4,4'-dihydroxybenzanilide are used, which melt at a comparatively high temperature of 184.degree. C.


OBJECTS OF THE INVENTION

The object of the present invention is to provide monomers and additional comonomers by which an anisotropic network can always be obtained. Another object of the invention is to lower the melting point of the starting monomers, or mixture of monomers and comonomers, so that conversion to the desired products occurs at the lowest possible temperatures. Yet another object is to use nonmesogenic starting materials.


BRIEF DESCRIPTION OF THE DRAWING

The figure shows a comparison of the variation in storage modulus as a function of temperature for the inventive composition and a prior art composition.


DETAILED DESCRIPTION OF THE INVENTION

According to the invention, this object is met by tris(cyanato)-s-triazines having the following formula (I): ##STR2## where
R.sub.1 and R.sub.2, independently of one another, represent a halogen, in particular chlorine, bromine and fluorine, hydrogen or a methyl or ethyl group.
It is surprising for one skilled in the art that this product has liquid-crystalline properties, since similar products have been described in the literature as nonliquid-crystalline (Barclay, G. G., Ober, C. K., Papathomas, K. I., Wang, D. W., Macromolecules 1992, 25, 2974-2954).
The object of the invention is further met by a process in which polycyanates in the form of liquid-crystalline tris(cyanato)-s-triazines having the above formula (I) are polycyclotrimerized.
In carrying out the process according to the invention, the polycyclotrimerization is effected in the melt. With respect to the compounds in the above formula (I), the polycyclotrimerization is preferably carried out between approximately 90.degree. and 300.degree. C., most preferably between approximately 120.degree. and 220.degree. C. The temperature advisably does not fall below approximately 90.degree. C., as it would then be impossible to rule out the presence of crystalline components which are poorly accessible to a further reaction. This would result in a deterioration of the mechanical properties of the process product. If the maximum temperature of approximately 300.degree. C. is exceeded, the clarification point of the mixture would be exceeded. Therefore, it is advantageous to keep to the range of approximately 90.degree. to 300.degree. C. and especially to the range of approximately 120.degree. to 220.degree. C.
The process according to the invention can easily be carried out exclusively thermally and does not absolutely require the use of catalysts. The use of catalysts accelerates the polycyclotrimerization in a desirable manner and is therefore preferred. Suitable catalysts include, for example, acids, bases, salts, nitrogen compounds and phosphorous compounds. Specific examples include Lewis acids such as AlCl.sub.3, BF.sub.3, FeCl.sub.3, TiCl.sub.4, ZnCl.sub.2, and SnCl.sub.2, Bronsted acids such as HCl and H.sub.3 PO.sub.4 ; aromatic hydroxy compounds such as phenol, p-nitrophenol, catechol, and dihydroxynaphthalene; sodium hydroxide; sodium methanolate; sodium phenolate; trimethylamine; isochinoline; tetrahydroisochinoline; tetraethylammonium chloride; pyridine-N-oxide; tributylphosphine; and metal octanoates; naphthenates, and

REFERENCES:
patent: 5136011 (1992-08-01), Barclay et al.
G.G. Barclay et al. (1992) Macromol. 25, 2947-2954.
D. Janietz et al. (1993) Liquid Crystals 13, 499-505.

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