Title: Process for fractionation/concentration to reduce the polydispersivity of polymers
Abstract: Methods of reducing the amount of undesirable by-products in the production of polymers are disclosed. The resulting polyetherimides have lower polydispersivity and enhanced thermomechanical properties. In some embodiments, cyclic and low molecular weight linear oligomers are also obtained.
Patent Number: 6,906,168 Issued on 06/14/2005 to Khouri, et al.
| Inventors:
|
Khouri; Farid Fouad (Clifton Park, NY);
Howson; Paul Edward (Latham, NY)
|
| Assignee:
|
General Electric Company (Schenectady, NY)
|
| Appl. No.:
|
647678 |
| Filed:
|
August 25, 2003 |
| Current U.S. Class: |
528/480; 528/491; 528/493; 528/494; 528/497; 528/503 |
| Intern'l Class: |
C08F 006/00; C08F006/06 |
| Field of Search: |
528/480,491,493,494,497,502.R,503
|
References Cited [Referenced By]
U.S. Patent Documents
| 4217438 | Aug., 1980 | Brunelle et al.
| |
| 4879419 | Nov., 1989 | Johannessen.
| |
| 5229482 | Jul., 1993 | Brunelle.
| |
| 5264536 | Nov., 1993 | Radosz.
| |
| 5830974 | Nov., 1998 | Schmidhauser et al.
| |
| 5910559 | Jun., 1999 | Rahman et al.
| |
| 6166137 | Dec., 2000 | Brown et al.
| |
| 6235866 | May., 2001 | Khouri et al.
| |
| 6417255 | Jul., 2002 | Penning et al.
| |
| 6630568 | Oct., 2003 | Johnson et al.
| |
Other References
PCT Search Report-Dec. 27, 2004.
|
Primary Examiner: Seidleck; James J.
Assistant Examiner: Zemel; Irina S.
Attorney, Agent or Firm: Carter, DeLuca Farrell & Schmidt LLP
Claims
1. A method for reducing the polydispersivity of a high molecular weight polyetherimide
resin comprising:
forming a polyetherimide solution using a solvent selected from the group consisting
of o-dichlorobenzene and anisole;
contacting the polyetherimide solution with an anti-solvent selected from the
group consisting of toluene, ketones, acetone, tetrahydrofuran, xylenes, and dioxane
wherein the anti-solvent is capable of dissolving low molecular weight species
but not the high molecular weight polyetherimide;
allowing phase separation to occur to obtain a light phase and a heavy phase;
and
recovering the desired polyetherimide from the heavy phase, wherein the resulting
polyetherimide possessed a polydispersivity ranging from about 1.5 to about 2.5.
2. The method of claim 1 wherein the step of forming a polyetherimide resin further
comprises forming a polyetherimide by reacting a bis-halophthalimide with at least
one alkali metal salt of a dihydroxy-substituted aromatic compound in the presence
of a phase transfer catalyst.
3. The method of claim 2 wherein the step of forming the polyetherimide comprises
reacting a bis-halophthalimide produced by reacting a diamino compound with an
anhydride having the following formula
##STR4##
wherein X is selected from the group consisting of nitro, nitroso, tosyloxy,
halogen and mixtures thereof, with at least one alkali metal salt of a dihydroxy-substituted
aromatic compound in the presence of a phase transfer catalyst.
4. The method of claim 2 wherein the step of forming the polyetherimide comprises
reacting a bis-halophthalimide produced by reacting a diamino compound with an
anhydride selected from the group consisting of 3-chlorophthalic anhydride, 4-chlorophthalic
anhydride, dichloro phthalic anhydride, phthalic anhydride and mixtures thereof,
with at least one alkali metal salt of a dihydroxy-substituted aromatic compound
in the presence of a phase transfer catalyst.
5. The method of claim 4 wherein the step of forming the polyetherimide comprises
reacting the anhydride with a diamino compound selected from the group consisting
of ethylenediamine, propylenediamine, trimethylenediamine, diethylenetriamine,
triethylenetetramine, heptamethylenediamine, octamethylenediamine, 1,12-dodecanediamine,
1,18-octadecanediamine, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine,
4-methylnonamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,2-dimethylpropylenediamine,
N-methyl-bis(3-aminopropyl)amine, 3-methoxyhexamethylenediamine, 1,2-bis(3-aminopropoxy)ethane,
bis(3-aminopropyl)sulfide, 1,4-cyclohexanediamine, bis-(4-aminocyclohexyl)methane,
m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene,
m-xylylenediamine, p-xylylenediamine, 2-methyl-4,6-diethyl-1,3-phenylenediamine,
5-methyl-4,6-diethyl-1,3-phenylene-diamine, benzidine, 3,3′-dimethylbenzidine,
3,3′-dimethoxybenzidine, 1,5-diaminonaphthalene, bis(4-aminophenyl)methane,
bis(2-chloro-4-amino-3,5-diethylphenyl)methane, bis(4-aminophenyl)propane, 2,4-bis(β-amino-t-butyl)toluene,
bis(p-α-methyl-o-aminopentyl)benzene, 1,3-diamino-4-isopropylbenzene, bis(4-aminophenyl)sulfone,
bis(4-aminophenyl)ether, 1,3-bis(3-aminopropyl)tetramethyldisiloxane and mixtures thereof.
6. The method of claim 3 wherein the step of forming the polyetherimide comprises
reacting a bis-halophthalimide produced by reacting an anhydride with a diamino
compound selected from the group consisting of m-phenylenediamine and p-phenylenediamine,
with at least one alkali metal salt of a dihydroxy-substituted aromatic compound
in the presence of a phase transfer catalyst.
7. The method of claim 2 wherein the step of forming the polyetherimide resin
further comprises forming a polyetherimide by reacting a halophthalimide with bisphenol
A disodium salt.
8. The method of claim 2 wherein the step of forming the polyetherimide resin
further comprises reacting a halophthalimide with at least one alkali metal salt
of a dihydroxy-substituted aromatic compound in the presence of a phase transfer
catalyst selected from the group consisting of hexaalkylguanidinium alkane salts
and α,ω-bis(pentaalkylguanidinium)alkane salts.
9. The method of claim 1 wherein the step of forming the polyetherimide solution
further comprises heating the polyetherimide solution to a temperature ranging
from about 50° C. to about 180° C.
10. The method of claim 1 wherein the step of forming the polyetherimide solution
further comprises heating the polyetherimide solution to a temperature ranging
from about 80° C. to about 110°.
11. The method of claim 1 wherein the step of contacting the polyetherimide solution
with the anti-solvent comprises adding anti-solvent in an amount ranging from about
{fraction (1/10)} to about ½ by weight of the solvent in the polyetherimide solution.
12. The method of claim 1 wherein the step of contacting the polyetherimide solution
with the anti-solvent comprises adding anti-solvent in an amount of about ⅓
by weight of the solvent in the polyetherimide solution.
13. The method of claim 1 wherein the step of contacting the polyetherimide solution
with the anti-solvent further comprises heating to a temperature ranging from about
100° C. to about 180° C.
14. The method of claim 1 wherein the step of contacting the polyetherimide solution
with the anti-solvent further comprises heating to a temperature ranging from about
135° C. to about 150° C.
15. A polyetherimide resin produced in accordance with the method of claim 1.
16. A for reducing the polydispersivity of a high molecular weight polyetherimide
resin comprising:
forming a polyetherimide solution using a solvent selected from the group consisting
of o-dichlorobenzene and anisole and by reacting a diamino compound selected from
the group consisting of m-phenylenediamine and p-phenylenediamine with an anhydride
selected from the group consisting of 3-chlorophthalic anhydride, 4-chlorophthalic
anhydride, dichloro phthalic anhydride, phthalic anhydride and mixtures thereof
to produce a halophthalimide, and then reacting the halophthalimide with bisphenol
A disodium salt in the presence of a phase transfer catalyst selected from the
group consisting of hexaalkylguanidinium alkane salts or a α,ω-bis(pentaalkylguanidinium)alkane
salts:
contacting the polyetherimide solution with an anti-solvent capable of dissolving
low molecular weight species but not the high molecular weight polyetherimide selected
from the group consisting of toluene, ketones, acetone, tetrahydrofuran, xylenes,
and dioxane:
allowing phase separation to occur to obtain a light phase and a heavy phase;
and
recovering the desired polyetherimide from the heavy phase,
wherein the resulting polyetherimide possessed a polydispersivity ranging from
about 1.5 to about 2.5.
17. The method of claim 16 wherein the step of forming the polyetherimide solution
further comprises heating the polyetherimide solution to a temperature ranging
from about 50° C. to about 180° C.
18. The method of claim 16 wherein the step of forming the polyetherimide solution
further comprises heating the polyetherimide solution to a temperature ranging
from about 80° C. to about 110°.
19. The method of claim 16 wherein the step of contacting the polyetherimide
solution with the anti-solvent comprises adding anti-solvent in an amount ranging
from about {fraction (1/10)} to about ½ by weight of the solvent in the polyetherimide solution.
20. The method of claim 16 wherein the step of contacting the polyetherimide
solution with the anti-solvent comprises adding anti-solvent in an amount of about
⅓ by weight of the solvent in the polyetherimide solution.
21. The method of claim 16 wherein the step of contacting the polyetherimide
solution with the anti-solvent further comprises heating to a temperature ranging
from about 100° C. to about 180° C.
22. The method of claim 16 wherein the step of contacting the polyetherimide
solution with the anti-solvent further comprises heating to a temperature ranging
from about 135° C. to about 150° C.
23. A polyetherimide resin produced in accordance with the method of claim 16.
Description
BACKGROUND OF THE INVENTION
The present disclosure is directed to methods for reducing the levels of cyclic
oligomers produced during the formation of polyetherimide resins. More particularly,
a fast and efficient fractionation method is disclosed to reduce the polydispersivity
of the polyetherimide resins without having to precipitate the desired polyetherimide
in solid form. Another aspect of this invention is to concentrate cyclic oligomers
for further use in other applications.
Polymerization reactions typically lead to products of varying polydispersivity
or polydispersity, i.e., having a range of components from low to high molecular
weight. The quality of a final polymeric product depends to a large extent on how
broad its molecular weight distribution is (in most cases, the broader the distribution,
the lower the quality). Polydispersivity is expressed as the polydispersivity index
(PDI), which is the ratio of the weight average molecular weight (Mw) to the number
average molecular weight (Mn).
In many polymerization reactions, undesirable low molecular weight by-products
and unreacted monomers remain in the final product. Such by-products and unreacted
monomers can have adverse effects on the properties of the desired polymers and
thus must be separated.
For example, aromatic polyethers, particularly polyetherimides, are important
engineering resins because of their excellent properties. These polymers may be
produced by various methods including the condensation polymerization of a diamine
and a dianhydride as in the reaction of m-phenylene diamine (mPD) and bisphenol-A
dianhydride (BPADA). The resulting polyetherimides have a polydispersivity of about 2.2.
Alternatively, polyetherimides may be prepared by a displacement polymerization
process which reacts salts of dihydroxyaromatic compounds, such as bisphenol A
disodium salt (BPA.Na
2), with dihaloaromatic molecules. For example,
polyetherimides are conveniently prepared by the reaction of salts of dihydroxyaromatic
compounds with bis(halophthalimides) as illustrated by 1,3-bis[N-(4-chlorophthalimido)]benzene
(hereinafter sometimes "CIPAMI"), which has the structure
##STR1##
The bis(halophthalimides), in turn, are produced by reacting at least one diamino
compound, preferably an aromatic diamine such as mPD or p-phenylenediamine (pPD),
and at least one halophthalic anhydride.
According to U.S. Pat. Nos. 5,229,482 and 5,830,974, the preparation of
aromatic polyethers may be conducted in solution in relatively non-polar solvents,
using a phase transfer catalyst which is substantially stable under the temperature
conditions employed. Solvents disclosed in U.S. Pat. No. 5,229,482 include o-dichlorobenzene,
dichlorotoluene, 1,2,4-trichlorobenzene and diphenyl sulfone. In U.S. Pat. No.
5,830,974, monoalkoxybenzenes such as anisole, diphenylether, or phenetole are
employed. Solvents of the same types may be used for the preparation of the bis(halophthalimide) intermediates.
The general scheme for the production of bis(halophthalimide) and the subsequent
production of polyetherimide is set forth in FIG.
1. The polyetherimides
produced by these displacement polymerizations have a relatively high polydispersivity,
ranging from about 3.6 to about 2.6, depending upon the amount of 3-CIPA and 4-CIPA
used in preparing the CIPAMI monomer. Polymers made by these methods can have between
about 10% and about 15% of a cyclic monomer by-product.
When bisphenol A, mPD and 4-CIPA are used to produce polyetherimides, it has
been found that the level of cyclic oligomers in the final product is about 3%.
However, it has been found that the amount of cyclics increases as the level of
3-CIPA is increased as a starting material in CIPAMI synthesis. Where 100% 3-CIPA
and mPD are used as the starting material, the amount of cyclic oligomers can range
from about 15% to about 20%. Interestingly, it has been found that about two thirds
of the cyclic oligomers are a single 1:1 adduct. The reaction scheme demonstrating
the use of 3-CIPAMI to produce a polyetherimide with the cyclic oligomer by-product
is set forth in FIG.
2.
Other undesirable by-products include short polymer chains and linear oligomers.
These by-products, in addition to unreacted monomers, being off specification,
must be discarded after separation, increasing the cost and size of the waste stream
and reducing the efficiency of the process.
High levels of these low molecular weight species can also have adverse effects
on the properties of the resulting polymer. Such negative effects include a lower
glass transition temperature (Tg), reduced ductility, and problems with processing
including surface appearance, as demonstrated by reduced glossiness.
However, it has also been found that the use of 3-CIPA in combination with
other bisphenols and diamines can produce polyetherimides possessing higher Tg
(about 15° to about 20° C. higher), and improved flow at high shear.
It is therefore desirable to use 3-CIPA as a starting material, at least in part,
in the production of polyetherimides.
Means for recovering products from polymerization reactions are known. For
example, polymer fractionation processes recover a desired polymer in solid form
from a solution by precipitation into an anti-solvent. The process is referred
to as total precipitation if the anti-solvent does not dissolve the polymer or
low molecular weight species in the polymer such as linear oligomers, cyclic oligomers
and monomers. Heptane and other alkanes are examples of anti-solvents which may
be used for total precipitation of polymers, especially polyetherimide polymers.
However, where such anti-solvents are used, the presence of low molecular weight
species in the polymer such as linear oligomers, cyclic oligomers and monomers
will result in a product having a higher polydispersivity.
Other methods for recovering polyetherimide polymers include the precipitation
of highly polydispersive polymers in toluene, acetone, or tetrahydrofuran, which
dissolve low molecular weight species and unreacted monomers from the polymer.
Thus, polymers obtained by these methods have reduced polydispersivity.
It is desirable, therefore, to develop a method for preparing polymers which
is
adapted to the close control of molecular weight and removing unreacted monomers
and undesirable by-products by relatively simple means. In the case of polyetherimide
polymers, polymers with lower polydispersivity will have improved thermomechanical
performance characteristics.
BRIEF DESCRIPTION OF THE INVENTION
The present disclosure is directed to methods for reducing the polydispersivity
of a polymer by:
- forming a polymer solution;
- contacting the polymer solution with an anti-solvent capable of dissolving
low molecular weight species but not the desired high molecular weight polymer;
- allowing phase separation to occur to obtain a light phase and a heavy
phase; and
- recovering the desired polymer from the heavy phase;
- wherein the resulting polymer has reduced polydispersivity.
In one embodiment, the method of the present disclosure includes concentrating
and recovering the cyclic and low molecular weight linear oligomers in the light phase.
In another of its aspects, the present disclosure includes methods for reducing
the polydispersivity of a polyetherimide resin that include:
- forming a polyetherimide solution;
- contacting the polyetherimide solution with an anti-solvent capable
of dissolving low molecular weight species but not the high molecular weight polyetherimide;
- allowing phase separation to occur to obtain a light phase and a heavy
phase; and
- recovering the desired polyetherimide from the heavy phase;
- wherein the resulting polyetherimide has reduced polydispersivity.
Another aspect of the present disclosure is to polyetherimide resins with
lower polydispersivity produced in accordance with the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overview of the CIPAMI and polyetherimide synthesis process.
FIG. 2 is a depiction of CIPAMI synthesis demonstrating undesirable cyclic formation.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present disclosure, methods have been developed which
lower
the polydispersivity of polymers by removing undesirable by-products and unreacted
monomers from a polymer solution. The methods of the present disclosure utilize
fractionation of a polymer solution with an anti-solvent to remove low molecular
weight by-products and unreacted monomers. The anti-solvent, which is preferably
admixed with a certain fraction of the polymer solvent, dissolves low molecular
weight by-products and unreacted monomers, which enter a light phase, but does
not dissolve the polymer, which remains in the heavy phase. Thus, once the two
phases are obtained, simple phase separation techniques may be utilized to obtain
a heavy phase containing the desired polymer, without the need for precipitation,
filtration, washing, etc. that is otherwise required to separate the desired polymer
from the undesirable by-products and monomers. The resulting polymer, having had
the undesirable low molecular weight by-products and unreacted monomers removed,
has a lower polydispersivity.
In one embodiment, the methods of the present disclosure can be used in the synthesis
of polyetherimides produced from bisimide monomers which, in turn, are prepared
from phthalic anhydrides and diamines. The lower polydispersivity can be achieved
by removing low molecular weight species such as short polymer chains, linear oligomers
and cyclic oligomers from the desired polymer. While the following disclosure utilizes
the preparation of polyetherimides as an example, the methods of the present disclosure
may be utilized to reduce the polydispersivity of any polymer placed in solution
with an appropriate polymer solvent and anti-solvent pair.
Anhydrides suitable for use in preparing the bishalophthalimides of the
present invention have formula (II)
##STR2##
wherein X is a moiety which may be any organic group that does not interfere
with the imidization reaction. In one embodiment X is a displaceable group which
participates in a subsequent polymerization reaction. Preferably, X is nitro, nitroso,
tosyloxy (—OTs) or halogen; most preferably X is chlorine. Especially preferred
anhydrides include 3-chlorophthalic anhydride, 4-chlorophthalic anhydride, and
dichlorophthalic anhydride. In a most preferred embodiment, the bis-halophthalimide
monomer is made from either substantially pure 3-CIPA or a mixture of 3-CIPA combined
with other phthalic anhydride monomers selected from the group consisting of 4-chlorophthalic
anhydride, dichlorophthalic anhydride, and substituted analogs thereof where the
other positions on the aromatic ring of the anhydride are either hydrogen atoms
or substituted with nonreactive groups such as alkyl or aryl groups, and mixtures thereof.
In addition, in one embodiment of the present disclosure, phthalic anhydride
(i.e.,
a compound having the structure of formula (II) wherein X is hydrogen) may be separately
added to the reaction mixture. In such a case, the addition of phthalic anhydride
to the reaction mixture will provide a mixture comprising both polymerizable monomer
and end-capping monomer, i.e., a halophthalimide having only one reactive site
which is thus capable of end-capping a growing polymer chain in a polymerization
reaction. In such a case, the use of phthalic anhydride to form end-capping monomers
may be used to control the molecular weight of the polyetherimide produced in the
subsequent polymerization reaction. In addition, as known to those skilled in the
art, other anhydrides may be utilized to form end-capping monomers.
Any diamino compound may be employed in the method of this invention. Examples
of suitable compounds are ethylenediamine, propylenediamine, trimethylenediamine,
diethylenetriamine, triethylenetetramine, heptamethylenediamine, octamethylenediamine,
1,12-dodecanediamine, 1,18-octadecanediamine, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine,
4-methylnonamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,2-dimethylpropylenediamine,
N-methyl-bis(3-aminopropyl)amine, 3-methoxyhexamethylenediamine, 1,2-bis(3-aminopropoxy)ethane,
bis(3-aminopropyl)sulfide, 1,4-cyclohexanediamine, bis-(4-aminocyclohexyl)methane,
m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene,
m-xylylenediamine, p-xylylenediamine, 2-methyl-4,6-diethyl-1,3-phenylenediamine,
5-methyl-4,6-diethyl-1,3-phenylenediamine, benzidine, 3,3′-dimethylbenzidine,
3,3′-dimethoxybenzidine, 1,5-diaminonaphthalene, bis(4-aminophenyl)methane,
bis(2-chloro-4-amino-3,5-diethylphenyl)methane, bis(4-aminophenyl)propane, 2,4-bis(β-amino-t-butyl)toluene,
bis(p-β-meth yl-o-aminopentyl)benzene, 1,3-diamino-4-isopropylbenzene, bis(4-aminophenyl)sulfone,
bis(4-aminophenyl)ether and 1,3-bis(3-aminopropyl)tetramethyldisiloxane. Mixtures
of these compounds may also be present. The preferred diamino compounds are aromatic
diamines, especially m- and p-phenylenediamine and mixtures thereof.
The production of the bis(halophthalimide) preferably occurs in the presence
of a non-polar organic liquid, usually having a substantially lower polarity than
that of the dipolar aprotic solvents such as dimethylformamide, dimethylacetamide
and N-methylpyrrolidinone. Said non-polar solvent preferably has a boiling point
above about 100° C. and most preferably above about 150° C., in order
to facilitate the reaction which requires temperatures above that temperature.
Suitable liquids of this type include o-dichlorobenzene, dichlorotoluene, 1,2,4-trichlorobenzene,
diphenyl sulfone and alkoxybenzenes such as anisole and veratrole, and more generically
liquids whose polarity is no higher than those of the aforementioned liquids. Liquids
of similar polarity but lower boiling points, such as chlorobenzene, may be employed
at super-atmospheric pressures. Anisole and o-dichlorobenzene are usually preferred.
The bis(halophthalimide) preparation method of the invention typically employs
temperatures of at least 110° C., preferably in the range from 150° to
about 275° C., preferably about 175-225° C. At temperatures below 110°
C., reaction rates are for the most part too slow for economical operation. It
is within the scope of the invention to employ super-atmospheric pressures, typically
up to about 5 atm, to facilitate the use of high temperatures without causing liquid
to be lost by evaporation through boiling.
A further feature, for the same reason, is a solids content in the reaction mixture
of at least about 5%, preferably at least about 12% and most preferably about 15-25%,
by weight. By "solids content" is meant the proportion of bishalophthalimide product
as a percentage of the total weight of the bishalophthalimide and solvent. It is
further within the scope of the invention to change the solids content during the
reaction, for such reasons as to effectuate transfer of the reaction mixture from
one vessel to another.
Other constituent proportions in the reaction mixture preferably include, a
molar ratio of anhydride to diamine in the range of from about 1.98:1 to about
2.04:1, with a ratio of about 2:1 being most preferred. While other ratios may
be employed, a slight excess of anhydride or diamine may be desirable. Catalyst,
if used, is present in an amount effective to accelerate the reaction, usually
about 0.1-0.3% by weight based on the weight of diamine. Suitable imidization catalysts
include, but are not limited to, sodium phenyl phosphinate, acetic acid, benzoic
acid, phthalic acid, or substituted derivatives thereof. In one embodiment, sodium
phenyl phosphinate is utilized as the imidization catalyst.
The reaction between at least one amine reactant and at least one anhydride reactant
by the methods of the present invention results in products generally comprising
phthalimides of formula (I). Bis(halophthalimides) which may be produced include
1,3- and 1,4-bis[N-(4-fluorophthalimido)]benzene and 1,3- and 1,4-bis[N-(3-fluorophthalimido)]-benzene;
and 4,4′-bis[N-(4-fluorophthalimido)]phenyl ether and 4,4′-bis[N-(3-fluorophthalimido)]phenyl
ether; and the corresponding chloro, bromo and nitro compounds. Mixtures of such
compounds may also be employed. Especially preferred substituted aromatic compounds
of formula I include at least one of 1,3-bis[N-(4-chlorophthalimido)]benzene, 1,4-bis[N-(4-chlorophthalimido)]benzene,
1,3-bis[N-(3-chlorophthalimido)]benzene, 1,4-bis[N-(3-chlorophthalimido)]benzene,
1-[N-(4-chlorophthalimido)]-3[N-(3-chlorophthalimido)benzene, or 1-[N-(4-chlorophthalimido)]4[N-(3-chlorophthalimido)benzene.
Where the starting phthalic anhydride is pure 3-CIPA, a 3-3′-CIPAMI as depicted
in reaction scheme (II) is produced and then subsequently reacted with additional
components to produce the desired polyetherimide. However, as noted above, in other
embodiments a mixture of 3-CIPA with other phthalic anhydrides, including 4-CIPA,
dichlorophthalic anhydride, and phthalic anhydride, may be utilized to produce
the desired halophthalimide which, in turn, is then utilized to produce the desired polyetherimide.
At least one dihydroxy-substituted aromatic hydrocarbon is then reacted with
the
CIPAMI to produce the desired polyetherimide. Suitable dihydroxy-substituted aromatic
hydrocarbons include those having the formula
wherein A
2 is a divalent aromatic hydrocarbon radical. Suitable
A
2 radicals include m-phenylene, p-phenylene, 4,4′-biphenylene,
4,4′-bi(3,5-dimethyl)phenylene, 2,2-bis(4-phenylene)propane and similar
radicals such as those which correspond to the dihydroxy-substituted aromatic hydrocarbons
disclosed by name or formula (generic or specific) in U.S. Pat. No. 4,217,438.
The A
2 radical preferably has the formula
wherein each of A
3 and A
4 is a monocyclic divalent
aromatic hydrocarbon radical and Y is a bridging hydrocarbon radical in which one
or two atoms separate A
3 from A
4. The free valence bonds
in formula IV are usually in the meta or para positions of A
3 and A
4
in relation to Y. Compounds in which A
2 has formula IV are bisphenols,
and for the sake of brevity the term "bisphenol" is sometimes used herein to designate
the dihydroxy-substituted aromatic hydrocarbons; it should be understood, however,
that non-bisphenol compounds of this type may also be employed as appropriate.
In formula IV, the A
3 and A
4 values may be unsubstituted
phenylene or halo or hydrocarbon-substituted derivatives thereof, illustrative
substituents (one or more) being alkyl, alkenyl, bromo, chloro. Unsubstituted phenylene
radicals are preferred. Both A
3 and A
4 are preferably p-phenylene,
although both may be o- or m-phenylene or one o- or m-phenylene and the other p-phenylene.
The bridging radical, Y, is one in which one or two atoms, preferably one, separate
A
3 from A
4. Illustrative radicals of this type are methylene,
cyclohexylmethylene, 2-[2.2.1]-bicycloheptylmethylene, ethylene, isopropylidene,
neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene and adamantylidene;
gem-alkylene (alkylidene) radicals are preferred. Also included, however, are unsaturated radicals.
Some preferred examples of dihydric phenols which may be utilized include 6-hydroxy-1-(4′-hydroxyphenyl)-1,3,3-trimethylindane,
4,4′-(3,3,5-trimethylcyclohexylidene)diphenol; 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane;
2,2-bis(4-hydroxyphenyl)propane (commonly known as bisphenol-A); 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane;
2,2-bis(4-hydroxy-3-methylphenyl)propane; 2,2-bis(4-hydroxy-3-ethylphenyl)propane;
2,2-bis(4-hydroxy-3-isopropylphenyl)propane; 2,4′-dihyroxydiphenylmethane;
bis(2-hydroxyphenyl)methane; bis(4-hydroxyphenyl)methane; bis(4-hydroxy-5-nitrophenyl)methane;
bis(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)methane; 1,1-bis(4-hydroxyphenyl)ethane;
1,1-bis(4-hydroxy-2-chlorophenyl)ethane; 2,2-bis(3-phenyl-4-hydroxyphenyl)-propane;
bis(4-hydroxyphenyl)cyclohexylmethane; 2,2-bis(4-hydroxyphenyl)-1-phenylpropane;
resorcinol; C
1-3 alkyl-substituted resorcinols. For reasons of availability
and particular suitability for the purposes of this invention, in one embodiment
the preferred dihydric phenol is bisphenol A in which the radical of formula IV
is the 2,2-bis(4-phenylene)propane radical and in which Y is isopropylidene and
A
3 and A
4 are each p-phenylene.
Preferably, the reaction of salts of dihydroxyaromatic compounds are
utilized in the methods of the present disclosure. More preferably, alkali metal
salts of dihydroxy-substituted aromatic hydrocarbons are employed. These alkali
metal salts are typically sodium or potassium salts, with sodium salts frequently
preferred by reason of their availability and relatively low cost. Most preferably,
bisphenol A disodium salt (BPA.NA
2) is utilized.
In a preferred embodiment, bisphenol A disodium salt is added to the organic
solvent
and the mixture azeotroped to a dry condition. Then, a second co-monomer, for example
a bis[N-(chlorophthalimido)]benzene, may be added and the mixture azeotroped to
a dry condition. Then a catalyst may be added as a pre-dried solution in organic
solvent. The process is expedited when predried solvent and co-monomers are used.
One class of preferred solvents utilized in producing the polyetherimide includes
those of low polarity. Suitable solvents of this type include halogenated aromatic
compounds such as o-dichlorobenzene, dichlorotoluene and 1,2,4-trichlorobenzene;
and diphenyl sulfone. Solvents of similar polarity but lower boiling points, such
as chlorobenzene, may be employed at superatmospheric pressures. Another class
of preferred solvents includes aromatic ethers such as diphenyl ether, phenetole
(ethoxybenzene), and anisole (methoxybenzene). O-dichlorobenzene and alkoxybenzenes,
most preferably anisole, are particularly preferred. In many instances, halogenated
aromatic solvents are preferred over alkoxybenzenes since the former have less
tendency than the latter to interact with and inactivate the phase transfer catalyst
described below. Another class of solvents suitable for the present invention is
polar aprotic solvents, illustrative examples of which include dimethylformamide
(DMF), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), and N-methylpyrrolidinone (NMP).
The preferred phase transfer catalysts, by reason of their exceptional stability
at high temperatures and their effectiveness to produce high molecular weight aromatic
polyether polymers in high yield are the hexaalkylguanidinium and α,ω-bis(pentaalkylguanidinium)alkane
salts. For the sake of brevity, both types of salts are hereinafter sometimes designated
"guanidinium salt".
Suitable guanidinium salts are illustrated by those of the formula
##STR3##
wherein:
each of R
2, R
3, R
4, R
5 and R
6
is a primary alkyl radical and R
7 is a primary alkyl or bis(primary
alkylene) radical, or at least one of the R
2—R
3, R
4—R
5
and R
6—R
7 combinations with the connecting nitrogen
atom forms a heterocyclic radical;
X2 is an anion; and
n is 1 or 2.
The alkyl radicals suitable as R
2-6 include primary alkyl radicals,
generally containing about 1-12 carbon atoms. R
7 is usually an alkyl
radical of the same structure as R
2-6 or a C
2-12 alkylene
radical in which the terminal carbons are primary; most preferably, it is C
2-6
alkyl or C
4-8 straight chain alkylene. Alternatively, any combination
of R
2-7 and the corresponding nitrogen atom(s) may form a heterocyclic
radical such as piperidino, pyrrolo or morpholino.
The X
2 value may be any anion and is preferably an anion of a strong
acid; examples are chloride, bromide and methanesulfonate. Chloride and bromide
ions are usually preferred. The value of n will be 1 or 2 depending on whether
R
7 is alkyl or alkylene.
As can be seen in formula V, the positive charge in the guanidinium salt is delocalized
over one carbon and three nitrogen atoms. This is believed to contribute to the
salts' stability under the relatively high temperature conditions encountered in
embodiments of the invention.
Additionally, the reaction is typically sensitive to water and it is
preferable to dry the solvent-comprising reaction mixture by known methods, for
example by boiling or azeotroping water from the mixture, typically prior to delivering
the catalyst. In one embodiment, water removal from the system can be accomplished
in either batch, semi-continuous or continuous processes using means well-known
in the art such as a distillation column in conjunction with one or more reactors.
In one embodiment, a mixture of water and non-polar organic liquid distilling from
a reactor is sent to a distillation column where water is taken off overhead and
solvent is recycled back into the reactor at a rate to maintain or increase the
desired solids concentration. Other methods for water removal include, but are
not limited to, passing the condensed distillate through a drying bed for chemical
or physical adsorption of water.
Once the formation of the desired resin has occurred, the polymer solution,
e.g., polyetherimide in o-DCB, is placed in contact with an anti-solvent which
is capable of dissolving low molecular weight species such as unreacted monomers,
and undesirable products such as cyclic oligomers and/or linear oligomers. The
anti-solvent does not, however, dissolve the polymer, e.g., the polyetherimide.
Suitable anti-solvents for use in accordance with the present disclosure include
toluene, ketones, preferably acetone, tetrahydrofuran, xylenes, dioxane, etc.
In those cases where the polymer is not already in solution, a suitable solvent
may be added to the polymer to produce a polymer solution for fractionation. Such
solvents include, but are not limited to, o-DCB, trichlorobenzene, anisole, and
veratrole. Once the polymer solution has been formed, the anti-solvent is added
as described above.
In one embodiment, the polyetherimide solution is heated to a temperature ranging
from about 50° C. to about 180° C., preferably from about 80° C.
to about 110° C., with a temperature of from about 90° C. to about 100°
C. being most preferred.
While stirring, an anti-solvent such as toluene is added. It is desirable to
add the maximum amount of anti-solvent without precipitation of the solid polymer.
Preferably, the anti-solvent is added in an amount ranging from about {fraction
(1/10)} to about ½ by weight of the solvent in the polymer solution, more
preferably in an amount equal to about ⅓ by weight of the solvent in the
polymer solution.
Once the anti-solvent has been added, the solution is preferably heated to a
temperature ranging from about 100° C. to about 180° C., preferably from
about 135° ° C. to about 150° C., with a range of from about 140°
C. to about 145° C. being most preferred. Stirring is stopped and the polymer
solution is allowed to cool. Phase separation starts to occur and is complete in
about 1 to about 2 hours.
The phases may then be separated by methods known to those skilled in the art
including, but not limited to, settling. For polyetherimides, two phases are obtained
after separation: the light phase of o-DCB and toluene is rich in cyclic and linear
oligomers; the heavy phase contains about 20-25% solids, including the desired polymer.
The level of reduction in the polydispersivity of the resulting polymers is directly
related to the amount of anti-solvent used. In this manner, the polydispersivity
of the polymer may be reduced. For example, in the case of polyetherimides, the
resulting polyetherimide preferably has a reduced polydispersivity. In one embodiment,
the polydispersivity ranges from about 1.5 to about 2.5, more preferably from about
2.0 to about 2.3.
Polyetherimide resins produced in accordance with the methods of the
present disclosure have improved thermomechanical performance characteristics such
as glass transition temperature (Tg) or heat deflection temperature (HDT).
In one embodiment, the method of the present disclosure includes concentrating
and recovering the cyclic and low molecular weight linear oligomers from the light
phase for use in other applications such as re-equilibration to high molecular
weight polymer or in processes where improved flow is needed.
The present disclosure is illustrated by the following non-limiting examples.
EXAMPLE 1
Four samples of a polyetherimide solution produced by reacting bisphenol-A salt
with a CIPAMI produced by reacting mPD and 3-CIPA were prepared. 70:30 compositions
were prepared by dissolving the polyetherimide in o-DCB and heating it to 180°
C. with stirring to obtain a solution having a concentration of 10% solids. 5 grams
of a 10% polymer solution (0.5 g polymer in 4.5 g o-DCB) were prepared with varying
amounts (0.3, 0.5, 1.0 and 1.5 g) of toluene as an anti-solvent. The samples and
the amounts of toluene used are set forth below in Table 1.
| TABLE 1 |
| Sample designation for toluene induced |
| fractionation of a o-DCB CIPAMI polymer solution |
| |
|
|
Wt. Toluene (g)/5 g. 10% |
| |
Material |
Sample |
polymer solution |
| |
| |
Light Phase |
1 |
0.3 |
| |
|
2 |
0.5 |
| |
|
3 |
1.0 |
| |
|
4 |
1.5 |
| |
The polyetherimide solution was heated to a temperature ranging from 90°
C. to 100° C. While stirring, toluene was added to each sample in the amounts
noted above. The solution was then heated to a temperature from 140° C. to
145° C. to clear any turbidity. Stirring was stopped and the polymer solution
was allowed to cool. Phase separation started to occur and was complete in about
1 to about 2 hours. In each case the solution fractionated into two phases—one
light and one heavy.
The light and heavy phases obtained from each sample were then subjected to gel
permeation chromatography (GPC) analysis. GPC analysis for high polymer was performed
by using chloroform as eluent (elution rate of 0.8 ml-min-1) on a HP 1100 Series
apparatus equipped with a PL gel 5 um Mixed-C column and a UV detector utilizing
the manufacturer's software. The % cyclics analyses were determined on a Polymer
Labs HT-120 GPC system equipped with a PL gel Mixed-C column and UV detector, using
chloroform as an eluent at 0.7 mL/min and utilizing Perkin Elmer Turbochrom software.
Table 2 summarizes the GPC results.
| TABLE 2 |
| Detailed GPC analysis of light and |
| heavy samples of fractionated CIPAMI polymer |
| Material |
Sample |
(K) |
PDI |
Mono |
Di- |
Tri- |
Tetra- |
Penta- |
Total |
| Original |
10% |
54.1 |
2.79 |
0.72 |
1.25 |
0.44 |
0.21 |
0.17 |
2.79 |
| |
soln. |
| Light |
1 |
20.7 |
2.74 |
0.22 |
0.44 |
0.17 |
0.09 |
0.09 |
0.99 |
| Phase |
|
7 |
| |
2 |
16.5 |
2.66 |
0.32 |
0.8 |
0.35 |
0.19 |
0.15 |
1.81 |
| |
|
7 |
| |
3 |
11.0 |
2.4 |
3.76 |
5.78 |
2.09 |
0.93 |
0.79 |
13.35 |
| |
|
4 |
| |
4 |
8.43 |
2.25 |
3.2 |
5.4 |
2.04 |
0.95 |
0.82 |
12.41 |
| Heavy |
1 |
58.9 |
2.46 |
0.66 |
1.05 |
0.45 |
0.21 |
0.16 |
2.53 |
| Phase |
|
9 |
| |
2 |
58.2 |
2.37 |
0.33 |
0.6 |
0.22 |
0.11 |
0.09 |
1.35 |
| |
|
5 |
| |
3 |
56.3 |
2.43 |
0.28 |
0.56 |
0.21 |
0.11 |
0.08 |
1.24 |
| |
4 |
57.4 |
2.23 |
0.38 |
0.67 |
0.26 |
0.13 |
0.1 |
1.54 |
As can be seen from Table 2, the polydispersivity narrowed as the amount of toluene
increased. There was a slight increase in the weight average molecular weight of
the polymer as the polydispersivity was reduced. Moreover, as the amount of toluene
increased, the Mw of the extracted polymer in the light phase was reduced. The
total amount of cyclics in the heavy phase was reduced as additional cyclics were
found in the light phase. As is apparent from Table 2, the volume of the light
phase increased with the amount of toluene used. Therefore, heavy phase from sample
4 had the most concentrated polymer sample.
EXAMPLE 2
Three different polyetherimide resins were produced by reacting a bisphenol-A
salt with a CIPAMI monomer prepared from 70:30 4/3-CIPA and mPD (designated as
samples 5, 6 and 7 in Table 3). Another sample was prepared by reacting a bisphenol-A
salt with a CIPAMI monomer produced from 3-CIPA and mPD (designated as sample 8
in Table 4). Samples were fractionated by the addition of toluene and polydispersivity
determined following the methods of Example 1.
| TABLE 3 |
| Large Scale PDF fractionation |
| of mixed CIPAMI based polymers |
| |
CIPAMI % |
Polymer Before |
|
| |
Composition |
Fractionation |
Polymer After Fractionation |
| Sample |
4/3-CIPA |
Mw (K) |
PDI |
Mw (K) |
PDI |
| 5 |
70:30 |
49.9 |
2.73 |
55.9 |
2.19 |
| 6 |
70:30 |
54.6 |
2.75 |
58.4 |
2.27 |
| 7 |
70:30 |
46.5 |
2.8 |
50.9 |
2.07 |
| TABLE 4 |
| Fractionation results of all 3-CIPAMI based polymer |
| |
|
|
% Cyclic |
|
| Sample 8 |
Mw (K) |
PDI |
Monomer |
% Total Cyclics |
| Polymer as |
53.7 |
3.71 |
10.4 |
13.2 |
| made |
| Heavy Phase |
58.5 |
2.42 |
3.0 |
3.9 |
| Light Phase |
5.1 |
— |
65 |
83 |
Table 3 demonstrates the results of the fractionation and the ability of the
present methods to lower the polydispersivity of the samples. As is apparent from
Table 4, the 3-CIPA based polyetherimide possessed a large amount of cyclics, which
were successfully separated by the methods of the present invention.
As is also apparent from the above, the level of reduction in the polydispersivity
of the resulting polymers was directly related to the amount of toluene used.
While the disclosure has been illustrated and described in typical embodiments,
it is not intended to be limited to the details shown, since various modifications
and substitutions can be made without departing in any way from the spirit of the
present disclosure. For example, while much of the specification describes the
fractionation of a polymer solution containing a polyetherimide and its undesirable
side products and unreacted monomers, the methods of the present disclosure can
be utilized to fractionate any polymer solution and thereby lower the polydispersivity
of the desired polymer. As such, further modifications and equivalents of the disclosure
herein disclosed may occur to persons skilled in the art using no more than routine
experimentation, and all such modifications and equivalents are believed to be
within the spirit and scope of the disclosure as defined by the following claims.
*
