Compositions – Liquid crystal compositions
Reexamination Certificate
1998-12-16
2002-02-19
Wu, Shean C. (Department: 2871)
Compositions
Liquid crystal compositions
C252S299620, C252S299670, C524S492000, C528S190000, C528S193000, C528S194000, C528S195000
Reexamination Certificate
active
06348163
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to compositions containing a particular class of liquid crystalline polyesters and one or more aromatic phosphonites. This invention also pertains to a process for preparing liquid crystalline polyesters in the presence of one or more aromatic phosphonites.
BACKGROUND OF THE INVENTION
Liquid crystalline polyesters (LCPs) are unique among polymers because they have very high tensile, flexural, and temperature resistance properties which are very desirable properties for high performance applications, such as in structural applications and in electronic applications. U.S. Pat. No. 4,169,933 discloses a group of liquid crystalline polyesters which consist essentially of residues of terephthalic acid, 2,6-naphthalenedicarboxylic acid, hydroquinone, and p-hydroxybenzoic acid. It is highly desirable that these types of LCPs have the very best thermal stability so that their molecular weight is maintained, i.e., during their preparation and injection molding, extrusion, etc., into the many end uses that have been identified where they show superior performance. Unless measures are taken during the preparation of such liquid crystalline polyesters, the polymerization rate may be so rapid that an appreciable amount of the starting materials may be lost due to co-distillation, sublimation, or other means. Loss of starting materials may lead to (a) loss of stoichiometry, (b) reduced yield of polymer, and (c) plugging or partial plugging of the reactor condensing system due to the solids being co-distilled or sublimed. Also, when the polymerization rate is very fast, it is more difficult to control the process and produce a predetermined molecular weight or inherent viscosity (I.V.).
It is an object of this invention to provide novel compositions containing one or more liquid crystalline polyesters. It is also an object of this invention to provide liquid crystalline polyesters comprising certain levels of terephthalic acid, cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, hydroquinone, biphenol and/or p-hydroxybenzoic acid where the rate of polymerization of LCPs is slowed when prepared to high molecular weight/IV in the melt so that stoichiometry is better maintained, high yields of polymer are maintained, plugging of the reactor condensing system is minimized or eliminated, and the preparation of LCPs having predetermined molecular weights/IV's is facilitated.
It is also an object of this invention to provide a process for preparing compositions containing certain LCPs in the presence of certain levels of one or more aromatic phosphonites. The new process of the invention enables the preparation of LCPs in a more controllable manner and produces products having improved thermalloxidative stability.
SUMMARY OF THE INVENTION
This invention relates to a composition comprising:
A. a liquid crystalline polyester derived from:
(I) diacid residues selected from terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, biphenyl dicarboxylic acid and naphthalenedicarboxylic acid;
(II) diol residues selected from hydroquinone, resorcinol, and biphenol, and
(III) optionally, diacid residues selected from p-hydroxybenzoic acid, m-hydroxybenzoic acid, and 6-hydroxy-2-naphthoic acid,
wherein the moles of the diol residues are equal to the moles of the diacid residues and the total of the I and II or the I, II and III mole percentages are based on the total residues which make up the liquid crystalline polyester; and
B. one or more aromatic phosphonites.
This invention further relates to the process of preparing certain liquid crystalline polyesters in the presence of one or more aromatic phosphonites wherein said one or more phosphonites are added to the monomer charge and/or to derived prepolymers prior to polycondensation.
DESCRIPTION OF THE INVENTION
The invention relates to compositions comprising certain liquid crystalline polyesters and one or more aromatic phosphonites as well as a process for preparing the compositions. More specifically, the invention relates to a composition comprising:
A. a liquid crystalline polyester derived from:
(I) diacid residues selected from terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, biphenyl dicarboxylic acid and naphthalenedicarboxylic acid;
(II) diol residues selected from hydroquinone, resorcinol, and biphenol, and
(III) optionally, diacid residues selected from p-hydroxybenzoic acid, m-hydroxybenzoic acid, and 6-hydroxy-2-naphthoic acid;
wherein the moles of the diol residues are equal to the moles of the diacid residues and the total of the I and II or the I, II and III mole percentages are based on the total residues which make up the liquid crystalline polyester; and
B. one or more aromatic phosphonites.
Preferred examples of monomers from which component (I) may be derived are terephthalic acid; naphthalenedicarboxylic acid, preferably, 2,6-naphthalenedicarboxylic acid; and cyclohexanedicarboxylic acid, preferably, 1,4-cyclohexanedicarboxylic acid. More preferred dicarboxylic acids are terephthalic acid and naphthalenedicarboxylic acid.
Preferred examples of monomers from which component (II) may derived are hydroquinone, and biphenol, preferably 4,4′-biphenol.
A preferred example of a monomer from which component (III) may derived is p-hydroxybenzoic acid.
It is preferred that the LCP compositions of the invention comprise about 1.5 to about 25, preferably, about 5 to about 15 mole percent terephthalic acid (T) residues; about 6.5 to about 37, preferably, about 15 to about 25 mole percent 2,6-naphthalenedicarboxylic acid (N) residues; about 16 to 42, preferably, about 20 to about 30 mole percent hydroquinone (HQ) residues; about 17 to 67, preferably, about 30 to about 50 mole percent p-hydroxybenzoic acid (PHB) residues; where the total mole percent of T, N, HQ and PHB is equal to 100.
Particularly, the LCP compositions of the invention comprise about 0.01 to 5.0 weight % of one or more aromatic phosphonites, preferably 0.5 to 3.0 weight %, more preferably, 0.1 to 2.0 weight % based on the total polymer weight.
The LCP compositions of the invention preferably have the following characteristics: the T:N molar ratio is about 10:90 to about 60:40, preferably about 20:80 to about 40:60, where the moles of HQ are equal to the total moles of T and N, the liquid crystalline polyesters have melting points determined by differential scanning calorimetry (DSC) equal to or less than 375° C.
The aromatic phosphonites of the present invention generally have the following structure:
wherein A
2
is independently selected from the group consisting of oxygen or a chemical bond; R
6
is an aromatic radical and R
7
is independently selected from the group consisting of aliphatic or aromatic radicals. It is preferred that A
2
is a chemical bond. It is also preferred that R
6
is 4,4-biphenylene. It is further preferred that R
7
is substituted aryl. It is even further preferred that A
2
is a chemical bond, R
6
is 4,4biphenylene, and R
7
is substituted aryl.
Preferably, the aromatic phosphonites useful in the invention have the following structure:
wherein A
2
is independently selected from the group consisting of oxygen or a chemical bond; A
3
is a chemical bond, S, SO
2
, O, CO, alkylene or alkylidene containing from 1 to about 8 carbon atoms; and R
7
is independently selected from the group consisting of aliphatic radicals containing from about 1 to 25 carbon atoms, or substituted or unsubstituted aromatic radicals of from about 6 to30 carbon atoms. The R
7
groups in all of the structures are preferably independently selected from the group consisting of the following: methyl; ethyl; isopropyl; butyl; isobutyl; t-butyl; phenyl; linear or branched alkyl from about 1 to about 25 carbon atoms; aryl substituted phenyl containing about 6 to 30 carbon atoms; halogen substituted phenyl; hydroxy substituted C
6
to C
30
aryl; naphthyl; C
1
to C
25
alkyl or C
6
to C
30
aryl; substituted naphthyl; and halogen substituted naphthyl.
It is preferred that R
7
is
Bradley James Rodney
Darnell William Ronald
Long Timothy Edward
Seo Kab Sik
Eastman Chemical Company
Graves, Jr. Bernard J.
Tubach Cheryl J.
Wu Shean C.
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