Wholly aromatic mesomorphic polyester amides and the preparation thereof

Wholly aromatic mesomorphic polyester amides which form a liquid-crystalline fiber-forming melt below 320.degree. C. and are composed of PA1 (a) from 5 to 35 mol % of repeat units of the formula I ##STR1## (b) from 5 to 15 mol % of repeat units of the formula II ##STR2## (c) a molar amount corresponding to the total amount of components (a) and (b), and, when (e) signifies repeat units of the formula VI or VII, (e) of repeat units of the formula III ##STR3## (d) not less than 10 mol % of repeat units of the formula IV ##STR4## (e) from 2 to 15 mol % of repeat units of the formula V ##STR5## or of the formula VI ##STR6## the repeat units of the formula VI being replaceable in part by repeat units of the formula VII ##STR7## with the proviso that the molar proportions of components (a), (b), (c), (d) and (e) add up to 100 mol % in each case, the preparation thereof and fibers, films, molding and surface coating materials prepared therefrom.

The present invention relates to wholly aromatic mesomorphic polyester 
amides which form a liquid-crystalline fiber-forming melt below 
320.degree. C. 
Liquid-crystalline polyester amides are known. However, these polymers are 
in need of improvement in respect of heat distortion resistance, 
processability and especially abrasion resistance. U.S. Pat. No. 4,330,457 
describes polyester amides based on hydroxynaphthalenecarboxylic acid, 
terephthalic acid, hydroquinone and p-aminophenol. However, these 
polyester amides have a glass transition temperature of about 110.degree. 
C., and consequently a low heat distortion resistance. The same is true of 
the polyester amides disclosed in U.S. Pat. No. 4,351,917, which are based 
on p-aminophenol, p-hydroxybenzoic acid and hydroxynaphthalenecarboxylic 
acid. Finally, EP Application No. 81,900 discloses polyester amides which 
are at least 40% coaxial units such as aromatic dicarboxylic acids, 
hydroxyaromatic carboxylic acids, bisphenols and aminophenols and contain 
a sufficient amount of nonlinear radicals which are derived from aromatic 
m-amino compounds or binuclear aromatic sulfones. However, no indication 
is given as to which composition is necessary to obtain the desired 
combination of properties. 
It is an object of the present invention to provide wholly aromatic 
mesomorphic polyester amides which form a liquid-crystalline fiber-forming 
melt below 320.degree. C. and thus are easy to process and which, 
moreover, have a heat distortion resistance, a high abrasion resistance 
and high resilience. 
We have found that this object is achieved with wholly aromatic mesomorphic 
polyester amides which form a liquid-crystalline fiber-forming melt below 
320.degree. C. and are composed of 
(a) from 5 to 35 mol % of repeat units of the formula I 
##STR8## 
(b) from 5 to 15 mol % of repeat units of the formula II 
##STR9## 
(c) a molar amount corresponding to the total amount of components (a) and 
(b), and, when (e) signifies repeat units of the formulae VI and VII, (e) 
of repeat units of the formula III 
##STR10## 
(d) not less than 10 mol % of repeat units of the formula IV 
##STR11## 
(e) from 2 to 15 mol % of repeat units of the formula V 
##STR12## 
or of the formula VI 
##STR13## 
the repeat units of the formula VI being replaceable in part by repeat 
units of the formula VII 
##STR14## 
with the proviso that the molar proportions of components (a), (b), (c), 
(d) and (e) add up to 100 mol % in each case. 
The novel polyester amides have the advantage of having a smooth 
abrasion-resistant surface and a high heat distortion resistance. The 
novel polyester amides further have good mechanical properties, in 
particular high resilience. In addition, the novel polyester amides are 
substantially resistant to chemicals and flameretardant. The novel 
polyester amides finally have the advantage of forming a 
liquid-crystalline fiber-forming melt, and of being easily processable, at 
below 320.degree. C. 
The liquid-crystalline state of the polyester amides can be detected with a 
polarization microscope by a method described in German Published 
Application DAS No. 2,520,819. Applied in a thickness of 10 .mu.m between 
glass plates and viewed between crossed polarizers, the polymer melts have 
textures which can be ascribed to a mesomorphic phase. 
The polyester amides according to the invention are composed of 
(a) from 5 to 35 mol % of repeat units of the formula I. A suitable 
starting compound is, for example, tertbutylhydroquinone. 
(b) From 5 to 15 mol % of repeat units of the formula II. An advantageous 
starting compound is, for example, 4,4'-dihydroxybiphenyl. 
(c) A molar amount corresponding to the total amount of components (a), (b) 
and, when (e) signifies repeat units of the formulae VI and VII, (e) of 
repeat units of the formula III. A suitable starting compound is, for 
example, terephthalic acid. 
(d) Not less than 10 mol %, in particular not less than 20 mol %, of repeat 
units of the formula IV. An advantageous starting compound is 
p-hydroxybenzoic acid. 
(e) From 2 to 25 mol % of repeat units of the formula V or VI. An 
advantageous starting compound for units of the formula V is 
p-aminobenzoic acid and for units of the formula VI 4-aminophenol. It is 
also possible to replace some of the units of formula VI by those of the 
formula VII, the amount being advantageously from 2 to 5 mol %. A suitable 
starting compound for units of the formula VII is, for example, 
p-phenylenediamine. 
It will be readily understood that the molar proportions of components (a), 
(b), (c), (d) and (e) add up to 100 mol % in each case. 
In suitable wholly aromatic mesomorphic polyester amides, some of component 
(b) is replaced by units of the formula VIII or IX 
##STR15## 
An advantageous starting compound for units of the formula VIII is 
hydroquinone and for those of the formula IX resorcinol. Preferably units 
of the formula VIII and/or IX are present in an amount of from 3 to 12 mol 
%. 
It is also possible to replace some of component (a) by repeat units of the 
formula X 
##STR16## 
where R is halogen, C.sub.1 -C.sub.4 -alkyl (except t-butyl) or phenyl and 
n is 1, 2 or 3. Advantageously, units of the formula X are present in an 
amount of from 5 to 15 mol %. Suitable starting compounds for units of the 
formula X are, for example, chlorohydroquinone, methylhydroquinone, 
trimethylhydroquinone and phenylhydroquinone. 
The repeat units of the formula X are advantageously present in the 
polyester amides according to the invention in an amount of from 5 to 15 
mol %. 
Preferred wholly aromatic polyester amides have a glass transition 
temperature Tg of .gtoreq.150.degree. C., in particular of 
.gtoreq.170.degree. C. This glass transition temperature is measured by 
the DSC method described by K. H. Illers in Makromol. Chem. 127 (1969), 1. 
The wholly aromatic liquid-crystalline polyester amides form a 
liquid-crystalline fiber-forming melt at &lt;320.degree. C., in particular 
&lt;300.degree. C. Preference is also given to liquid-crystalline aromatic 
polyester amides which have partial crystallinity at &gt;200.degree. C. and 
&lt;300.degree. C. 
The liquid-crystalline polyester amides according to the invention are 
obtainable in a manner similar to that described, for example, in U.S. 
Pat. Nos. 4,375,530 and 4,118,372. 
In an advantageous embodiment, the polyester amides according to the 
invention are obtained in a single-stage process by converting the 
underivatized starting materials using anhydrides of lower fatty acids, 
for example fatty acids of 2 to 4 carbon atoms, in particular acetic 
anhydride, with or without catalysts. Suitable catalysts are described, 
for example, in EP-A-131,846 (page 9). They are advantageously used in an 
amount of from 0.001 to 1% by weight, based on the starting materials. In 
the conversion, the starting materials are heated together with the fatty 
acid anhydride, which is advantageously present in a molar excess of not 
less than 5%, based on the amino and hydroxyl groups present, with 
stirring in an inert gas atmosphere to a temperature at which reflux 
occurs. Advantageously the temperature is raised in stages, for example to 
130.degree.-200.degree. C. in not more than 5 hours, preferably up to 2 
hours, and is subsequently raised to 250.degree.-350.degree. C., for 
example in the course of 2-21/2 hours, while excess fatty acid anhydride 
and fatty acid are distilled off. To complete the reaction, it has been 
found to be advantageous to employ reduced pressure, for example 200 to 
0.1 mbar, toward the end. 
It is a remarkable and unforeseeable feature of this single-stage process 
that the desired polymer is obtained in a relatively short time in a 
troublefree and complete reaction without catalysts. This is all the more 
astonishing as the large number of chemically different amino and hydroxyl 
groups would be expected to lead to differences in reactivity and hence to 
inadequate polymer synthesis. 
The wholly aromatic liquid-crystalline polyester amides thus obtained are 
advantageously further condensed in the solid state, for example at 
150.degree.-250.degree. C., until the desired viscosity is obtained. This 
postcondensation in solid phase can take place not only before but also 
after thermoplastic processing. Advantageously the solid phase 
condensation is carried out in the presence of inert gases such as 
nitrogen. 
The polyester amides according to the invention can be modified by means of 
conventional additives such as stabilizers, oxidation inhibitors, agents 
against thermal decomposition and decomposition by ultraviolet light, 
lubricants, mold release agents, colorants such as dyes and pigments, 
fibrous or pulverulent fillers and reinforcing agents, nucleating agents 
or plasticizers. Such agents are employed in conventional active amounts. 
The stabilizers can be added to the polyester amides at any stage of the 
preparation or when completed. Preferably the stabilizers are added early 
on to prevent the onset of decomposition before the polymers are 
protected. 
The oxidation inhibitors and heat stabilizers which can be added to the 
polyester amides according to the invention include those which are 
generally employed for polymers, such as halides of metals of group I of 
the periodic table, for example halides of sodium, potassium or lithium 
together with copper(I) halides, for example chlorides, bromides or 
iodides. Other suitable stabilizers are sterically hindered phenols, 
hydroquinones and different substituted representatives of these groups 
and combinations thereof. These stabilizers are generally employed in 
concentrations of up to 1% by weight, based on the weight of the mixture. 
Suitable UV stabilizers also include those which are generally added to 
polymers, for example in amounts of up to 2% by weight, based on the 
polymeric material. Examples of UV stabilizers are different substituted 
resorcinols, salicylates, benzotriazoles, benzophenones and the like. 
Further suitable assistants are organic dyes such as nigrosine, and 
pigments such as titanium dioxide, cadmium sulfide, cadmium sulfide 
selenide, phthalocyanines, ultramarine blue or carbon black. Examples of 
suitable fibrous and pulverulent fillers and reinforcing agents are carbon 
fibers, glass fibers, amorphous silica, asbestos, calcium silicate, 
aluminum silicate, magnesium carbonate, kaolin, chalk, quartz powder, mica 
or feldspar. These reinforcing agents are advantageously used in amounts 
of up to 70% by weight of the polymer. 
Other possible assistants are nucleating agents, such as talcum, calcium 
fluoride, sodium phenyl phosphinate, aluminum oxide and finely divided 
polytetrafluoroethylene. 
Suitable plasticizers which can be employed in amounts of up to, for 
example, 20% by weight of the polymer are dioctyl phthalate, dibenzyl 
phthalate, butyl benzyl phthalate, hydrocarbon oils, 
N-n-butylbenzenesulfonamide, and o- and p-tolueneethylsulfonamide. 
Colorants such as dyes or pigments can be employed in amounts of up to 5% 
by weight. 
The wholly aromatic liquid-crystalline polyester amides according to the 
invention are suitable for preparing filaments, fibers, films, foams and 
industrial moldings by injection molding, pressing or extruding. The 
moldings prepared from the polyester amides according to the invention 
have excellent mechanical properties such as stiffness, strength and 
resilience. They are remarkably resistant to chemicals and 
flame-retardant. They also have a high heat distortion resistance and a 
smooth abrasion-resistant surface. The polyester amides according to the 
invention are therefore highly suitable for preparing moldings for 
electrical engineering, data processing, automotive construction and other 
industrial sectors. But they can also be used as surface coating 
materials, in pulverulent dispersion or as film.

The invention is illustrated by the following Examples. 
EXAMPLE 1 
0.2 mol of terephthalic acid, 0.26 mol of 4-hydroxybenzoic acid, 0.06 mol 
of 4-aminobenzoic acid, 0.16 mol of tert-butylhydroquione, 0.04 mol of 
4,4'-dihydroxydiphenyl and 0.86 mol of acetic anhydride are weighed into a 
flask equipped with a stirrer, nitrogen inlet and distillation attachment. 
Under nitrogen the contents are heated in a metal bath to 100.degree. C. 
The temperature is then raised to 150.degree. C. in 30', to 200.degree. C. 
in a further 100' and finally to 340.degree. C. in 120'. The pressure is 
then reduced to 560 mbar and subsequently halved every 10'. The final 
vacuum is 50 mbar. In this way a very viscous fiber-forming melt is 
obtained. DSC measurements indicate a glass transition temperature of 
182.degree. C. The intrinsic viscosity is 2.2 dl/g, measured at 60.degree. 
C. in an 0.1% strength by weight solution in pentafluorophenol. 
EXAMPLE 2 
0.2 mol of terephthalic acid, 0.23 mol of 4-hydroxybenzoic acid, 0.03 mol 
of 4-aminobenzoic acid, 0.16 mol of tert-butylhydroquinone, 0.04 mol of 
4,4'-dihydroxybiphenyl and 0.86 mol of acetic anhydride are polycondensed 
as in Example 1. The final vacuum is 100 mbar. The liquid-crystalline 
polyester amide has a glass transition temperature of 185.degree. C. and 
an intrinsic viscosity of 1.75 dl/g. 
EXAMPLE 3 
0.2 mol of terephthalic acid, 0.26 mol of 4-hydroxybenzoic acid, 0.02 mol 
of 4-aminophenol, 0.04 mol of 4,4'-dihydroxydiphenyl, 0.14 mol of 
tert-butylhydroquinone and 0.86 mol of acetic anhydride are reacted as in 
Example 1. The temperature is raised to 150.degree. C. in 30', to 
200.degree. C. in a further 100' and to 340.degree. C. in 120'. The final 
vacuum is 90 mbar. The liquid-crystalline polyester amide has a glass 
transition temperature of 175.degree. C. and an intrinsic viscosity of 1.0 
dl/g.