Poly(ester-imides) containing t-butylhydroquinone and trimellitic anhydride as part of the repeat units, as well as other monomers, are useful as molding resins. The polymers have a high glass transition temperature and are particularly useful in applications requiring good wear resistance.

BACKGROUND OF THE INVENTION 
Thermotropic liquid crystalline polymers are useful for many purposes, 
particularly as molding resins for making electronic connectors and 
mechanical parts, such as for automobiles. While there are many known 
compositions of such polymers, new compositions with desirable property 
combinations and low costs are constantly being sought. 
U.S. Pat. Nos. 4,727,129 and 4,728,714 and Japanese Patent 4-66259 describe 
thermotropic liquid crystalline polymers which contain only aromatic 
repeat units, some of these units being derived from trimellitic anhydride 
and t-butylhydroquinone. 
The present invention relates to novel thermotropic liquid crystalline 
poly(ester-imides) which contain repeat units derived from 
t-butylhydroquinone and trimellitic anhydride, and other monomers. These 
polymers are useful as molding resins and, when blended with 
polytetrafluoroethylene, for wear resistant applications. 
SUMMARY OF THE INVENTION 
The present invention relates to a liquid crystalline polymer consisting 
essentially of repeat units of the formulae: one or both of 
##STR1## 
and optionally one or more of 
##STR2## 
wherein the mount of (I)+(II) constitutes about 10 to about 30 mole 
percent of said repeat units; the mount of (III)+(IV)+(V) constitutes from 
0 to about 70 mole percent of said repeat units; Y is p-phenylene or 
##STR3## 
and Z is 
EQU --O--, --C(O)--, --S--, --C(CH.sub.3).sub.2 -- or --SO.sub.2 --

DETAILED DESCRIPTION 
The liquid crystalline polymers disclosed herein are poly(ester-imides) 
derived from t-butylhydroquinone (TBHQ), trimellitic anhydride (TMA), and 
other monomers. Units (I) and (II) include TMA as part (formally) of a 
dicarboxylic acid monomer containing an imide group which has reacted with 
TBHQ. Skilled artisans will understand that in all of the units shown 
above the t-butyl group of the TBHQ may be in either position on the 
benzene ting (relative to the other parts of the repeat units) to which it 
is attached. The dicarboxylic acid of (I) can be made by the reaction of 
TMA with p-aminobenzoic acid, while the dicarboxylic acid of (II) can be 
made by the reaction of 2 moles of TMA with an appropriate diamine, such 
as 4,4'-oxydianiline and p-phenylene diamine for example. With the 
exception of repeat unit (V), which is derived from p-hydroxybenzoic acid 
(PHBA), all of the other repeat units contain an ester linkage combining 
the appropriate dicarboxylic acid with TBHQ. In repeat units (III) and 
(IV) the dicarboxylic acid is terephthalic acid and 2,6-naphthalene 
dicarboxylic acid, respectively. 
In some preferred polymers, repeat units (I) or (II) are 100% of the repeat 
units. In other preferred polymers only one of units (III), (IV) or (V) is 
present, and the amount of (I), (II), or (I)+(II), as the case may be, is 
about 50 to 100 mole percent of the polymer. In preferred polymers, Y is 
##STR4## 
and preferably Z is 
EQU --O-- 
In other preferred polymers, repeat units (I) and (II) constitute 100% of 
the repeat units. 
The poly(ester-imides) of the present invention can be made by methods well 
known in the art. For example, the appropriate dicarboxylic acids, TBHQ 
and PHBA, if present, are combined to form a polymerization mixture. The 
hydroxy groups of the TBHQ and PHBA when added to the polymerization 
mixture can be in the form of lower alkyl esters, such as acetates, or the 
lower alkyl esters can be formed in situ by reaction with a stoichiometric 
amount of a lower alkyl carboxylic acid anhydride, such as acetic 
anhydride. After the acetate has formed, the temperature is raised to 
condense the monomers to a polymer and to distill off lower carboxylic 
acid byproduct, such as acetic acid. Usually, towards the end of the 
polymerization, a vacuum is applied to bring the final polymer to the 
desired molecular Weight or viscosity. Final finishing temperatures are 
typically about 300.degree. C. to about 360.degree. C. A catalyst, such as 
potassium acetate, may be added to accelerate the polymerization. 
The polymers of the present invention may be mixed with conventional 
materials for polymer compounding, such as pigments, colorants, 
antioxidants, flame retardants, lubricants, tougheners, and fillers, 
including glass, minerals (e.g., clay and talc), carbon black, and carbon 
fibers. Additionally, the polymers of the present invention may be mixed 
with other polymers. Persons skilled in the art will understand that the 
brief list of conventional additives above is merely illustrative and does 
not specifically name every material which may be mixed with the polymers 
of the present invention. 
The polymers of the present invention are useful as molding resins for 
electrical connectors, automotive parts, and other uses. They generally 
have high glass transition temperatures and are especially useful as 
blends with a tetrafluoroethylene polymer for parts which require good 
wear properties, such as frictional bearings. 
When the polymers of the present invention are blended with a 
tetrafluoroethylene polymer, the tetrafluoroethylene polymer is a polymer 
wherein about 90% or more of the repeat units therein are derived from 
tetrafluoroethylene, i.e. has the structure 
EQU --CF.sub.2 CF.sub.2 -- 
It is preferred that any other comonomer in the tetrafluoroethylene polymer 
be perfluorinated. An especially preferred tetrafluoroethylene polymer is 
the homopolymer of tetrafluoroethylene (i.e., polytetrafluoroethylene 
(PTFE)). 
Tetrafluoroethylene polymer is commercially available in various grades. 
The tetrafluoroethylene polymer can be in the form of micropowder, 
granules, or fibers. If used in the form of fibers, it is preferred that 
the fiber length be small, preferably 0.4 mm or less, and the fiber is 
less than 10 denier/filament. If the tetrafluoroethylene polymer is PTFE, 
various grades, such as granular and powder, may be used. Powder is 
preferred. Manufacturers of PTFE have particular grades that are 
recommended for use in blends where wear resistance is important and those 
grades are suitable for blending with liquid crystalline polymers of the 
present invention. 
It is preferred that blends with a tetrafluoroethylene polymer contain 
about 3 to about 50 weight percent, more preferably about 10 to about 40 
weight percent, and most preferably about 20 to about 35 weight percent of 
the tetrafluoroethylene polymer, based on the total weight of the 
poly(ester-imide) and the tetrafluoroethylene polymer. 
EXAMPLES 
In the Examples, the following abbreviations are used: 
"AA"--acetic anhydride 
"DSC"--differential scanning calorimetry 
"HM"--heat of melting, in J/g 
"2,6-N"--2,6-naphthalene dicarboxylic acid 
"T"--terephthalic acid 
"T.sub.g "--glass transition temperature 
"T.sub.m "--melting point 
"TMB"--a dicarboxylic acid having the structure 
##STR5## 
"TMO"--a dicarboxylic acid having the structure 
##STR6## 
EXPERIMENT 1 
Preparation of TMB 
Two hundred grams of trimellitic anhydride and 145 g of p-aminobenzoic acid 
and 1 liter of N,N-dimethylformamide ("DMF") were added to a 2 liter, 
four-neck, round bottom flask. A condenser, mechanical stirrer, and 
thermometer were attached to the flask and the flask contents were stirred 
and heated by an electric heating mantle. The contents were stirred and 
heated for 4.5 hours, and then the solution was allowed to cool to room 
temperature. One liter of methanol was then added with stirring, which was 
continued for 5 minutes. The resulting precipitate, which was a mixture of 
solid and liquid, was then filtered using a Buchner funnel, and the solid 
was washed with 1 liter of methanol. Two liters of distilled water were 
then heated to boiling in a 4 liter beaker and the washed solid was added 
with stirring, which was continued for 5 min. The resulting mixture was 
then filtered using a Buchner funnel, and again the solid was washed with 
1 liter of methanol. The solid product was dried in a vacuum oven with a 
nitrogen bleed at about 170.degree. C. for about 18 hrs. 
EXPERIMENT 2 
Preparation of TMO 
Two hundred ninety-nine grams of trimellitic anhydride were dissolved in 
500 ml of DMF in a four-neck, round bottom flask equipped with a calcium 
sulfate drying tower, mechanical stirrer, thermometer, reflux condenser, 
and a graduated addition funnel. The anhydride solution was heated to 
50.degree. C. A solution of 4-aminophenylether (150 g) in 350 ml of DMF 
was added dropwise for about 1 hr to the anhydride solution via an 
addition funnel. Afterwards, the resulting solution was heated to reflux 
for 3 hrs, then allowed to cool to room temperature. One liter of methanol 
was added to the reaction contents and the product was recovered by 
filtration under reduced pressure. The recovered yellow solid was stirred 
in 2 liters of boiling water for several minutes, filtered under reduced 
pressure, and washed again with 1 liter of methanol. The solid product was 
dried in a vacuum oven with a nitrogen purge at about 100.degree. C. for 
about 24 hrs. The product had a DSC T.sub.m of 380.degree. C., and no 
unreacted anhydride or partially reacted amide-acids were detected. 
EXAMPLES 1-7 
All the polymers for Examples 1-7 were made by the same basic procedure. 
The polymerization ingredients, listed in Table 1, were added to a resin 
kettle which was equipped with a stirrer and was heated by a liquid metal 
bath under nitrogen,. The bath was heated to reflux at about 170.degree. 
C. The reflux was done for one hour, after which acetic acid was distilled 
off as the temperature of the metal bath was gradually raised to about 
310.degree. C. over a period of approximately 2.5 hrs. The temperature was 
slowly raised to about 350.degree. C. to 360.degree. C. and the pressure 
was then slowly lowered over a period of 1 to 2 hrs until it reached about 
133-1330 Pa. While the pressure was lowered the metal bath was held at 
350.degree. C. to 360.degree. C. The temperature was maintained at low 
pressure until the desired viscosity (measured by the current draw of the 
stirrer motor) was reached. This took up to 4 hrs. Afterwards, stirring 
was stopped and the polymer was removed from the resin kettle. A DSC 
analysis was done after the polymer cooled. 
Ingredients used to make the polymer for each Example, together with 
polymer properties, are found in Table 1. 
In the examples, T.sub.g and T.sub.m were measured by DSC at a heating rate 
of 25.degree. C./min. The T.sub.g and T.sub.m reported were those of the 
first heat of the polymer. The T.sub.g was taken as the midpoint of the 
transition, and the T.sub.m was taken as the maximum of the melting 
endotherm. 
EXAMPLES 8 AND 9 
In Examples 8 and 9, blends of poly(ester-imides) and 
polytetrafluoroethylene were made and tested for wear resistance. In 
Example 8 the poly(ester-imide) of Example 1 was used, and in Example 9 
the poly(ester-imides) of Examples 4 and 5, which were identical, were 
combined and used. 
The polytetrafluoroethylene used in Examples 8 and 9 was Teflon.RTM. 
micropowder MP1500 PTFE (available from E. I. du Pont de Nemours and 
Company) having an average particle size of 20 microns and recommended for 
lubrication and wear resistance purposes. It is hereinafter referred to as 
MP1500. 
The procedure below was followed in preparing the LCP-PTFE blends of 
Examples 8 and 9. 
Dried pelletized LCP was blended with MP1500 to obtain a blend containing 
70 weight percent LCP and 30 weight percent MP 1500. The blend was melt 
mixed in a Werner-Pfleiderer 28 mm twin screw extruder equipped with 
standard mixing screws, a vacuum adapter attached to the mixing zone, and 
a 4.8 mm diameter circular die. The barrel and die temperatures were set 
at an appropriate temperature (i.e. above the T.sub.g and T.sub.m of the 
LCP in the blend), the screws at 150 rpm, and the blend was extruded at a 
rate of 5.8 kg/hr. The blend was pelletized, dried, and then injection 
molded on a 170 g injection molding machine using a barrel temperature 
setting above the T.sub.g and T.sub.m of the LCP used in the blend and a 
mold temperature setting of 100.degree. C. The blends were molded into 
flex bars, 3.2 mm thick, per ASTM D790. 
For wear testing, "pins", 6.35 mm square Coy 3.2 mm thick), were cut from 
the center edge of a flex bar. Three pins were mounted, on a 3.18 cm outer 
diameter circular holder, spaced 120.degree. apart, with the original 
longitudinal axis of the flex bar oriented tangentially to the 2.38 cm 
mean diameter mounting circle. The pins were loaded axially at pressure P 
against a 3.18 cm outer diameter and 1.59 cm inner diameter steel washer 
made of American Iron and Steel Institute 1018 carbon steel and finished 
to a 0.40 mm (AA) roughness. The washer was rotated at velocity V, 
measured at the mean diameter (2.38 cm) of the washer. The temperature of 
the washer could be measured and this temperature was considered to be the 
temperature of the surface of the LCP-PTFE blend. 
Wear data is summarized in Table 2, below. The higher the pressure (P) 
and/or velocity (V), the more severe the test and the wear are likely to 
be. K is volumetric wear rate divided by PV and is reported herein in 
units of (cm.sup.2 /kg).times.10.sup.8. The lower the value of K, the 
better is the wearing of the blend. Also shown in Table 2 is the washer 
temperature (W. Temp.) in .degree.C. Both of the blends of Examples 8 and 
9 exhibited excellent wear resistance. 
TABLE 1 
__________________________________________________________________________ 
Ingredients 
TMB TMO T 2,6N PHBA Properties 
AA TBHQ mole mole mole mole mole 
T.sub.g 
T.sub.m 
Ex. No. 
gm gm gm % gm % gm % gm % gm % .degree.C. 
.degree.C. 
HM 
__________________________________________________________________________ 
1.sup. 
238.3 
188.4 
352.7 
100 
-- -- -- -- -- -- -- -- 226 
328 
2.4 
2.sup.a 
342.1 
270.4 
253.1 
50 -- -- 135.1 
50 -- -- -- -- 217 
336 
4.1 
3.sup.a 
366.9 
290.0 
-- -- 478.0 
50 144.9 
50 -- -- -- -- 189 
230 
1.0 
4.sup.b 
263.6 
208.3 
-- -- 686.8 
100 
-- -- -- -- -- -- 201 
315.sup.d 
2.0 
5.sup.a 
263.6 
208.3 
-- -- 686.6 
100 
-- -- -- -- -- -- 203 
316.sup.e 
2.8 
6.sup.c 
348.9 
275.8 
-- -- 454.6 
50 -- -- 179.4 
50 -- -- 187 
232 
1.2 
7.sup. 
477.5 
251.6 
471.1 
50 -- -- -- -- -- -- 209.1 
50 211 
364 
4.6 
__________________________________________________________________________ 
.sup.a 100 ppm potassium acetate used as a catalyst in Ex. 2, 3, and 5. 
.sup.b The run started solidifying at 282.degree. C. bath temp. and melte 
at 330.degree. C. 
.sup.c The run started solidifying at 254.degree. C. bath temp. and melte 
at 289.degree. C. 
.sup.d Endotherm peak at 401.degree. C. believed to be a clearing 
temperature. 
.sup.e Endotherm peak at 397.degree. C. believed to be a clearing 
temperature. 
TABLE 2 
______________________________________ 
P V W. Temp. 
Example (MPa) (M/Min) K (.degree.C.) 
______________________________________ 
8 2.76 53.3 16.4 167 
2.76 61.0 1276 196 
9 2.76 53.3 27.6 166 
2.76 61.0 18.9 146 
______________________________________