Melt processable blend of a low molecular weight liquid crystalline compound and a polyolefin or polyester

An improved melt processable blend is provided comprised of a polymer selected from the group consisting of a polyolefin and a polyester and a low molecular weight liquid crystalline compound which is capable of forming an anisotropic melt phase at the melt processing temperature of the blend.

BACKGROUND OF THE INVENTION 
The present invention relates to a blend of a polyolefin or polyester and a 
melt processable low molecular weight liquid crystalline compound. 
U.K. Published Patent Application 2,008,598 discloses a polymer composition 
comprising 20 percent or less, based upon the total weight of polymeric 
material, of a first rigid polymeric material with the balance being a 
second polymeric material composed substantially of flexible molecular 
chains. The first polymeric material is dispersed in the second polymeric 
material in a microscope region of one um. or less. Foreign counterparts 
of this application include Japanese application No. 54065747, French 
application No. 2407956, West German application No. 2847782, and U.S. 
Pat. No. 4,228,218. 
European Patent Application No. 0030417 discloses the addition of a liquid 
crystalline polymer to at least one other melt processable polymer (e.g., 
a polyester) to improve the melt processability thereof. British Patent 
Application No. 8017685 discloses the addition of a liquid crystalline 
polymer to polytetrafluoroethylene. British Patent Application No. 8035800 
describes the addition of a liquid crystalline polymer to a nonliquid 
crystalline polymer. 
It is, however, desirable, to provide a method by which the viscosity of 
melt processable polymers such as polyolefins and polyesters can be 
modified while minimizing the effect upon the mechanical properties of the 
polymer by addition of nonpolymeric compounds thereto. Such viscosity 
modification will desirably result in processing and/or productivity 
advantages such as lower processing temperatures and pressures, faster 
extrusion rates, etc. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is thus provided a melt 
processable blend which possesses the ability to form shaped articles 
having satisfactory mechanical properties comprising: 
(a) a major amount of a melt processable polymer which is not capable of 
forming an anisotropic melt phase apart from the blend selected from the 
group consisting of a polyolefin and a polyester, and 
(b) a minor amount of a liquid crystalline compound having a molecular 
weight below about 1000 and which is capable of forming an anisotropic 
melt phase apart from the blend at the melt processing temperature of the 
blend. 
In accordance with the present invention, there is also provided an 
improved method of melt extruding a melt processable polymer which is not 
capable of forming an anisotropic melt phase apart from the blend selected 
from the group consisting of a polyolefin and a polyester by which the 
melt viscosity of said polyolefin or polyester is reduced comprising 
providing a blend comprised of a major amount of said polyolefin or 
polyester and a minor amount of a low molecular weight liquid crystalline 
compound having a molecular weight below about 1000 and which is capable 
of forming an anisotropic melt phase apart from the blend at the melt 
processing temperature of the blend and extruding said blend. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention is directed to a melt processable blend of a 
polyolefin or polyester and a low molecular weight liquid crystalline 
compound. As used herein, the term "blend" includes any physical blend, 
mixture, or alloy of the above components. 
The major component of the blend of the present invention is a melt 
processable polymer selected from the group consisting of a polyolefin and 
a polyester. These polymers are available commercially or can be prepared 
by known techniques. The polyolefin comprises alkylene units of two to 
five carbon atoms and may comprise straigth or branched chains. The 
alkylene units preferably contain two to four carbon atoms, and most 
preferably contain two carbon atoms. Thus, polyethylene is the preferred 
polyolefin for use in the blends of the present invention. Other suitable 
polyolefins include but are not limited to polybutene-1, polybutene-2, 
polyisobutylene, polypropylene, polypentene-1, etc. 
The term "polyester" as used herein is intended to include but not be 
limited to high molecular weight linear polyesters obtained from at least 
one aliphatic, cycloaliphatic or aromatic diol and at least one aliphatic, 
cycloaliphatic or aromatic dicarboxylic acid. The preferred polyester is 
poly(ethylene terephthalate) which is obtained from ethylene glycol and 
terephthalic acid. Another suitable material is polybutylene terephthalate 
as well as those polyesters derived from 
polymethylene-.alpha.,.omega.-diols and terephthalic acid. Other suitable 
polyesters include but are not limited to wholly aromatic polyesters such 
as the copolymers of iso and/or terephthalic acid and bisphenol A. 
The minor component of the blend of the present invention is a low 
molecular weight (non-polymeric) liquid crystalline compound. Liquid 
crystalline compounds are compounds which are liquid crystalline (i.e., 
anisotropic) in the melt phase. These compounds have been described by 
various terms, including "liquid crystalline," "liquid crystal" and 
"anisotropic." Briefly, the compounds of this class are thought to involve 
a parallel ordering of the molecular chains. The state wherein the 
molecules are so ordered is often referred to either as the liquid 
crystalline state or the nematic phase of the liquid crystalline material. 
Such properties may be confirmed by conventional polarized light 
techniques whereby crossed polarizers are utilized. More specifically, the 
anisotropic melt phase may be confirmed by the use of a Leitz polarizing 
microscope at a magnification of 40X with the sample on a Leitz hot stage 
and under nitrogen atmosphere. The compound is optically anisotropic, 
i.e., it transmits light when examined between crossed polarizers. 
Polarized light is transmitted when the sample is optically anisotropic 
even in the static state. 
The molecular weight of the compound is preferably below about 1000, and 
may be below about 500. The compound must be capable of forming an 
anisotropic melt at the melt processing temperature of the blend. The 
compounds should also not chemically react with the polyolefin or 
polyester component in the melt blend. In contrast to the compound, the 
polyolefin and polyester component are not capable of forming an 
anisotropic melt phase. 
Exemplary low molecular weight liquid crystalline compounds include but are 
not limited to N,N'-bis(p-methoxybenzylidene)-alpha, alpha'-bi-p-toluidine 
(which is nematic at 190.degree. C.); p-methoxycinnamic acid (which is 
nematic at 190.degree. C.); 
N,N'-bis(4-octyloxybenzylidene)-p-phenylenediamine (which is in one of its 
smectic phases at 170.degree. C.) and lithium stearate (which is smectic 
at 170.degree. C.). Mixtures of the above compounds may also be employed. 
The blends of the present invention comprise a major amount (i.e., greater 
than about 50 percent by weight) of the polyolefin or polyester component 
and a minor amount (i.e., less than about 50 percent by weight) of the low 
molecular weight liquid crystalline compound. The blend comprises 
approximately 50 to 99.5 percent by weight of the polyolefin or polyester 
component and approximately 50 to 0.5 percent by weight of the liquid 
crystalline compound. The above weight percentages are based upon the 
total weight of the two components in the blend. Preferably, the liquid 
crystalline compound is present in an amount of from about 0.5 to 10 and 
more preferably from about 0.5 to 5 percent by weight. 
In preparing the blends of the present invention, the individual components 
are commonly provided in the form of chips or pellets. Each of the 
components is weighed separately, and then physically mixed together in 
any appropriate apparatus, e.g., a ball mill. The physical mixture is then 
dried at approximately 100.degree. C. overnight or for a period of time of 
approximately 24 hours. The mixture is conveniently dried in a vacuum oven 
or in a circulating air oven, although any suitable apparatus may be used. 
The purpose of the drying step is to remove water from the physical 
mixture so as to prevent degradation of the blend. After the mixture of 
solid particles has been dried, the blend can then be prepared. A 
convenient method of forming the blend is melt extrusion. The extrusion 
apparatus thoroughly mixes the components in the melt and then extrudes 
the blend in the form of a strand which, upon solidification, can be 
broken up into chips or pellets. 
The blend of the present invention is capable of undergoing melt processing 
at a temperature within the range of approximately 150.degree. C. to 
370.degree. C. Preferably, the blend is capable of undergoing melt 
processing at a temperature within the range of approximately 200.degree. 
C. to 320.degree. C. 
The blend of the present invention is useful as a molding resin, and 
especially for injection molding. The blend can also be used in the 
formation of fibers and films. It is to be understood that the term "film" 
as used herein includes any of the various thin, flat structures which may 
be known in the art as a sheet or film, etc. Articles molded from the 
blends of the present invention exhibit good mechanical properties, such 
as tensile strength, tensile modulus, flexural strength, flexural modulus, 
notched Izod impact strength, and heat deflection temperature. 
A major benefit obtainable from the blends of the present invention is that 
the melt viscosity of the blends are considerably reduced relative to that 
of the polyolefin or polyester polymer alone thereby permitting lower 
processing temperatures and pressures to be used. Blends according to the 
invention may be produced which enable very substantial reductions in 
minimum processing temperatures, for example, 30.degree. C. or more, to be 
achieved. Reduction in extrusion pressure results in more stable 
processing and longer filter pack life. In addition, greater productivity 
can be achieved as a result of increased extrusion speeds. 
The extrusion apparatus used in connection with the present invention is 
not critical and may comprise any conventional extrusion apparatus. 
Examples of suitable extrusion apparatus are found, for example, in 
Plastics Engineering Handbook of the Society of the Plastics Industry, 
Inc., fourth edition, edited by Joel Frados, Van Nostrand Reinhold Company 
(1976), pages 156-203. 
Articles may also be molded from a molding compound which includes, as one 
component, the blend of the present invention. Such a molding compound 
incorporates into the blend of the present invention approximately 1 to 50 
percent, and preferably approximately 10 to 30 percent by weight, based 
upon the total weight of the molding compound, of a solid filler and/or 
reinforcing agent. Representative fibers which may serve as reinforcing 
agents include glass fibers, asbestos, graphitic carbon fibers, amorphous 
carbon fibers, synthetic polymeric fibers, aluminum fibers, aluminum 
silicate fibers, aluminum oxide fibers, titanium fibers, magnesium fibers, 
rock wool fibers, steel fibers, tungsten fibers, cotton, wool, and wood 
cellulose fibers, etc. Representative filler materials include calcium 
silicate, silica, clays, talc, mica, polytetrafluoroethylene, graphite, 
alumina trihydrate, sodium aluminum carbonate, barium ferrite, etc. 
In order to form an article by injection molding from the present blend, or 
from a molding compound comprised of the present blend, the blend or 
molding compound is brought to the melt temperature of the blend, e.g., 
approximately 200.degree. to 320.degree. C., and is then injected into a 
mold cavity. The mold cavity is commonly maintained at a temperature less 
than approximately 100.degree. C., e.g., approximately 90.degree. C. to 
100.degree. C. The blend in the melt phase is injected into the mold 
cavity at a pressure of approximately 10,000 p.s.i. The cycle time (i.e., 
the time between injections) for the present blend commonly is about 10 to 
40 seconds. 
The invention is additionally illustrated in connection with the following 
Examples which are to be considered as illustrative of the present 
invention. It should be understood, however, that the invention is not 
limited to the specific details of the Examples.

EXAMPLE 1 
A blend comprised of 90 percent by weight of high density polyethylene and 
10 percent by weight of N,N'-bis(p-methoxybenzylidene)-alpha, 
alpha'-bi-p-toluidine was prepared by admixing the respective components 
in solid form in a Banber mixer wherein the components were heated to a 
temperature above their melting temperature and a blend formed. 
The melt viscosity of both the blend and unmodified polyethylene were 
determined by capillary rheometry. The melt viscosity of the blend was 
reduced by about 25 percent over the shear rate range investigated. 
EXAMPLE 2 
The procedure of Example 1 was repeated with the exception that 
p-methoxycinnamic acid was employed as the liquid crystalline compound. A 
viscosity reduction of about 70 percent was achieved. 
EXAMPLE 3 
The procedure of Example 1 was repeated with the exception that 
N,N'-bis(4-octyloxybenzylidene)-p-phenylenediamine was employed as the 
liquid crystalline compound. A viscosity reduction of about 35 percent was 
achieved. 
EXAMPLE 4 
The procedure of Example 1 was repeated with the exception that lithium 
stearate was employed as the liquid crystalline compound. A viscosity 
reduction of about 25 percent was achieved. 
EXAMPLE 5 
A blend comprised of 90 percent by weight of polyethylene terephthalate and 
10 percent by weight of N,N'-bis(p-methoxybenzylidene)-alpha, 
alpha'-bi-p-toluidine is prepared as in Example 1. The melt viscosity of 
the polyethylene terephthalate is similarly reduced. 
The principles, preferred embodiments and modes of operation of the present 
invention have been described in the foregoing specification. The 
invention which is intended to be protected herein, however, is not to be 
construed as limited to the particular forms disclosed, since these are to 
be regarded as illustrative rather than restrictive. Variations and 
changes may be made by those skilled in the art without departing from the 
spirit of the invention.