U.S. patent application number 09/943575 was filed with the patent office on 2002-05-09 for process for the manufacture of low molecular weight polyphenylene ether resins.
Invention is credited to Braat, Adrianus J.F.M., Ingelbrecht, Hugo, Trion, Ruud.
Application Number | 20020055608 09/943575 |
Document ID | / |
Family ID | 22925930 |
Filed Date | 2002-05-09 |
United States Patent
Application |
20020055608 |
Kind Code |
A1 |
Braat, Adrianus J.F.M. ; et
al. |
May 9, 2002 |
Process for the manufacture of low molecular weight polyphenylene
ether resins
Abstract
The invention relates to a novel process for the manufacture of
very low molecular weight polyphenylene ether resin, typically
within the intrinsic viscosity range of about 0.08 dl/g to about
0.16 dl/g as measured in chloroform at 25.degree. C. The method
preferably comprises 2,6-dimethylphenol as a monovalent phenol
species. The invention also relates to the polyphenylene ether
resin made by the process as well as blends and articles containing
the polyphenylene ether resin made by the process.
Inventors: |
Braat, Adrianus J.F.M.;
(Roosendaal, NL) ; Ingelbrecht, Hugo; (Essen,
BE) ; Trion, Ruud; (Bergen op Zoom, NL) |
Correspondence
Address: |
John B. Yates
General Electric Company
One Plastics Avenue
Pittsfield
MA
01201
US
|
Family ID: |
22925930 |
Appl. No.: |
09/943575 |
Filed: |
August 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09943575 |
Aug 30, 2001 |
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09735990 |
Dec 13, 2000 |
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6303748 |
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09735990 |
Dec 13, 2000 |
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09245252 |
Feb 5, 1999 |
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6211327 |
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Current U.S.
Class: |
528/217 ;
264/45.9; 264/50; 528/212; 528/214; 528/501 |
Current CPC
Class: |
C08G 65/46 20130101;
C08G 65/44 20130101 |
Class at
Publication: |
528/217 ;
528/212; 528/214; 528/501; 264/50; 264/45.9 |
International
Class: |
C08G 065/38; C08G
065/44 |
Claims
What is claimed:
1. A process to produce a polyphenylene ether resin wherein said
process comprising oxidative coupling in a reaction solution at
least one monovalent phenol species using an oxygen containing gas
and a complex metal catalyst to produce a polyphenylene ether resin
which has less than a 10% decrease in intrinsic viscosity after an
equilibration step following the oxidative coupling, recovering the
complex metal catalyst with an aqueous containing solution and
isolating the polyphenylene ether resin through devolatilization of
the reaction solvent, wherein the devolatilization is accomplished
at least in part with a spray drier, a wiped film evaporator, a
flake evaporator, a flash vessel with melt pumps, or a
devolatilizing extruder.
2. The process of claim 1, wherein the process further comprises an
equilibration of a metal chelating agent with the complex metal
catalyst.
3. The process according to claim 2, wherein polyphenylene ether
after the equilibration step has a number average molecular weight
between 1250 and 7000.
4. The process of claim 1, wherein the devolatilization is
accomplished at least in part with a devolatilization extruder.
5. The process of claim 4, wherein the devolatilization extruder is
at least partly operated at between about 185-220.degree. C.
6. The process of claim 4, wherein the devolatilization extruder
has a vacuum vent with pressures less than 1 bar.
7. The process of claim 1, wherein the polyphenylene ether resin
has less than a 5% decrease in intrinsic viscosity after the
equilibration step.
8. The process of claim 4, wherein the reaction solvent has a
solids level of at least about 55% before feeding into the
devolatilization extruder.
9. The process of claim 1, wherein polyphenylene ether after the
equilibration step has a weight average molecular weight between
2500 and 15,000.
10. The process of claim 1, wherein the polyphenylene ether resin
has less than about a 10% change in intrinsic viscosity after a
thermal treatment at 200.degree. C. from about 0.2 minutes to about
20 minutes.
11. The process of claim 1 wherein the monovalent phenol species
comprises 2,6-dimethylphenol, 2,3,6-trimethylphenol, or mixtures of
the foregoing.
12. The process of claim 1 wherein the polyphenylene ether resin
has an incorporated amine content of less than about 0.3% by weight
based on the weight of the polyphenylene ether resin.
13. The process of claim 1 further comprising at least one of
underwater pelletization, die-face pelletization, flaking,
declining angle pelletization using water spraying, and vibration
drop pelletization.
14. The polyphenylene ether resin of claim 1 having an intrinsic
viscosity between about 0.08 dl/g and 0.16 dl/g.
15. The polyphenylene ether resin of claim 1 having a residual
solvent level of less than 1200 ppm after isolation.
16. A method to prepare a polyphenylene ether resin, said method
comprising oxidative coupling in a reaction solution at least one
monovalent phenol species using an oxygen containing gas and a
complex metal catalyst to produce a polyphenylene ether resin
wherein the polyphenylene ether resin has less than a 10% decrease
in intrinsic viscosity after an equilibration step following the
oxidative coupling; equilibrating a metal chelating agent with the
complex metal catalyst to prepare a chelated complex metal
catalyst; recovering the chelated complex metal catalyst with an
aqueous containing solution; and isolating the polyphenylene ether
resin through devolatilization of the reaction solvent.
17. The method of claim 16 wherein the polyphenylene ether resin
has less than about a 5% drop in intrinsic viscosity after the
equilibration step.
18. The method of claim 16 wherein the monovalent phenol species
comprises 2,6-dimethylphenol, 2,3,6-trimethylphenol, or mixtures of
the foregoing.
19. A method to reduce the yellowness index of polyphenylene ether
resin, wherein the method comprises oxidative coupling in a
reaction solution at least one monovalent phenol species using an
oxygen containing gas and a complex metal catalyst to produce a
polyphenylene ether resin; wherein the polyphenylene ether resin
has less than a 10% decrease in intrinsic viscosity after an
equilibration step following the oxidative coupling, recovering the
complex metal catalyst with an aqueous containing solution and
isolating the polyphenylene ether resin through devolatilization of
the reaction solvent, wherein the devolatilization is accomplished
at least in part with a devolatilization extruder maintained at a
temperature less than about 275.degree. C.
20. The method of claim 19 further comprising underwater
pelletization of the polyphenylene ether resin.
21. The method of claim 19 wherein the yellowness index of the
polyphenylene ether resin is less than about 30.
22. The process of claim 19 wherein the monovalent phenol species
comprises 2,6-dimethylphenol, 2,3,6-trimethylphenol, or mixtures of
the foregoing.
23. The polyphenylene ether resin of claim 19.
24. A process to produce a polyphenylene ether resin having a glass
transition temperature in the range of about 150.degree. C. to
about 160.degree. C., said process comprising oxidative coupling in
a reaction solution at least one monovalent phenol species using an
oxygen containing gas and a complex metal catalyst to produce a
polyphenylene ether resin; wherein the polyphenylene ether resin
has less than a 10% decrease in intrinsic viscosity after an
equilibration step following the oxidative coupling, recovering the
complex metal catalyst with an aqueous containing solution and
isolating the polyphenylene ether resin through devolatilization of
the reaction solvent.
25. The process of claim 24 wherein the polyphenylene ether resin
has an incorporated amine content of less than about 0.3% by weight
based on the weight of the polyphenylene ether resin
26. The process of claim 24 wherein the isolated polyphenylene
ether resin has a residual volatiles level of less than about 600
ppm based on the weight of the polyphenylene ether resin.
27. The polyphenylene ether resin of claim 24.
28. A process to produce a polyphenylene ether resin, said process
comprising oxidative coupling in a reaction solution at least one
monovalent phenol species using an oxygen containing gas and a
complex metal catalyst to produce a polyphenylene ether resin;
wherein the polyphenylene ether resin has less than a 10% decrease
in intrinsic viscosity after an equilibration step following the
oxidative coupling, recovering the complex metal catalyst with an
aqueous containing solution and isolating the polyphenylene ether
resin through devolatilization of the reaction solvent, wherein the
yield of isolated polyphenylene ether resin is over 90% based upon
the amount of monovalent phenol utilized.
29. The process of claim 28 wherein the yield is over 95%.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of the filing date of
U.S. Ser. No. 09/735,990 which claims the benefit of the filing
date of U.S. Ser. No. 09/245,252, now U.S. Pat. No. 6,211,327, the
entire contents of each application are hereby incorporated by
reference.
FEDERALLY SPONSORED RESEARCH
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The invention relates to a novel process for the manufacture
of very low molecular weight polyphenylene ether resin, typically
within the intrinsic viscosity range of about 0.08 dl/g to about
0.16 dl/g as measured in chloroform at 25.degree. C.
[0005] The invention also relates to the polyphenylene ether resin
made by the process as well as blends and articles containing the
polyphenylene ether resin made by the process.
[0006] 2. Brief Description of the Related Art
[0007] Polyphenylene ether resins (hereinafter "PPE") are
commercially attractive materials because of their unique
combination of physical, chemical, and electrical properties.
Furthermore, the combination of PPE with other resins provides
blends which result in additional overall properties such as
chemical resistance, high strength, and high flow.
[0008] The processes most generally used to produce PPE involve the
self-condensation of at least one monovalent phenol in the presence
of an oxygen containing gas and a catalyst comprising a metal amine
complex to produce resins typically within the intrinsic viscosity
range of about 0.35 dl/g to about 0.65 dl/g as measured in
chloroform at 25.degree. C.
[0009] These processes are typically carried out in the presence of
an organic solvent and the reaction is usually terminated by
removal of the catalyst from the reaction mixture. The catalyst
metal, after being converted into a soluble metal complex with the
aid of a chelating agent, is removed from the polymer solution with
standard extraction techniques, such as liquid-liquid extraction.
The PPE polymer can be isolated in a variety of methods although
generally by anti-solvent precipitation.
[0010] As new commercial applications are sought for PPE, a wider
range of intrinsic viscosity resins, especially lower intrinsic
viscosity resins, have been desired. As intrinsic viscosity
decreases in PPE resins, the level of hydroxyl groups increases and
the rheological properties change dramatically (lower viscosity as
intrinsic viscosity decreases) as compared to current commercially
available high molecular weight PPE produced by the methods
previously described. The physical properties of PPE remain highly
desirable and sought after in applications such as, for example,
adhesives, sealants and gels based on SBC, SBR, or epoxies for
automotive, housing, cabeling, membranes and electrical
applications. Also, epoxy based composites for aerospace,
automotive structural members and sporting equipment are desirable
applications as are electrical laminates, and IC encapsulation
materials based on epoxies and unsaturated polyesters. Friction
materials and abrasives compounds based on phenolic are also sought
after. PPE is also useful as an additive in various thermoplastic
and thermoset materials including, e.g., polypropylene,
polystyrene, ABS, polycarbonate, polyetherimide, polyamides,
polyesters, and the like and also thermosetting resins such as, for
example, epoxies, unsaturated polyesters, polyurethanes, allylic
thermosets, bismaleimides, phenolic resins, and the like. Varying
enhanced properties may be improved in different systems such as,
for example, improved heat performance, flame retardancy
improvement, decrease of electrical properties like D.sub.k and
D.sub.f, decrease in moisture absorption, increased creep
resistance, thermal expansion reduction, chemical resistance to
acids and bases, for various applications such as, for example,
automotive and house hold and electrical goods.
[0011] It is therefore apparent that a need exists for the
development of processes for the manufacture of very low molecular
weight polyphenylene ether resin, typically within the intrinsic
viscosity range of about 0.08 dl/g to about 0.16 dl/g as measured
in chloroform at 25.degree. C.
SUMMARY OF THE INVENTION
[0012] The needs discussed above have been generally satisfied by
the discovery of a process for preparing PPE having an intrinsic
viscosity within the range of about 0.08 dl/g to about 0.16 dl/g as
measured in chloroform at 25.degree. C. comprising oxidative
coupling in a reaction solution at least one monovalent phenol
species using an oxygen containing gas and a complex metal catalyst
to produce a PPE having an intrinsic viscosity within the range of
about 0.08 dl/g to about 0.16 dl/g as measured in chloroform at
25.degree. C.; removing at least a portion of the complex metal
catalyst with an aqueous containing solution; and isolating the PPE
through devolatilization of the reaction solvent.
[0013] The description that follows provides further details
regarding various embodiments of the invention.
DESCRIPTION OF THE DRAWINGS
[0014] Not applicable
DETAILED DESCRIPTION OF THE INVENTION
[0015] This invention provides for a process for the preparation of
low molecular weight PPE, preferably having an intrinsic viscosity
between about 0.08 dl/g and 0.16 dl/g, by oxidative coupling at
least one monovalent phenol species, preferably at least a portion
of which have substitution in at least the two ortho positions and
hydrogen or halogen in the para position, using an oxygen
containing gas and a complex metal-amine catalyst, preferably a
copper (I)-amine catalyst, as the oxidizing agent and extracting at
least a portion of the metal catalyst as a metal-organic acid salt
with an aqueous containing solution, and isolating the PPE through
devolatilization of the reaction solvent. In one embodiment, the
process affords a PPE that has less than a 10% increase, preferably
less than 5% increase in intrinsic viscosity after heating into the
melt phase. In another embodiment, the process affords a PPE that
has less than a 10% decrease, preferably less than 5% decrease,
most preferably less than 3% decrease in intrinsic viscosity after
an equilibration step following the oxidative coupling
reaction.
[0016] The PPE employed in the present invention are known polymers
comprising a plurality of structural units of the formula 1
[0017] wherein each structural unit may be the same or different,
and in each structural unit, each Q.sup.1 is independently halogen,
primary or secondary lower alkyl (i.e., alkyl containing up to 7
carbon atoms), phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, or
halohydrocarbonoxy wherein at least two carbon atoms separate the
halogen and oxygen atoms; and each Q.sup.2 is independently
hydrogen, halogen, primary or secondary lower alkyl, phenyl,
haloalkyl, hydrocarbonoxy or halohydrocarbonoxy as defined for
Q.sup.1. Most often, each Q.sup.1 is alkyl or phenyl, especially
C.sub.1-4 alkyl, and each Q.sup.2 is hydrogen.
[0018] Both homopolymer and copolymer PPE are included. The
preferred homopolymers are those containing
2,6-dimethyl-1,4-phenylene ether units. Suitable copolymers include
random copolymers containing such units in combination with (for
example) 2,3,6-trimethyl-1,4-phenylene ether units. Also included
are PPE containing moieties prepared by grafting vinyl monomers or
polymers such as polystyrenes and elastomers, as well as coupled
PPE in which coupling agents such as low molecular weight
polycarbonates, quinones, heterocycles and formals undergo reaction
in known manner with the hydroxy groups of two poly(phenylene
ether) chains to produce a higher molecular weight polymer,
provided a substantial proportion of free OH groups remains. Also
included are PPE's containing a functional endgroup, obtained from
reaction with a reactive compound having the functional
endgroup.
[0019] The low molecular weight PPE generally have a number average
molecular weight within the range of about 1250 to about 7000 and a
weight average molecular weight within the range of about 2500 to
about 15,000, as determined by gel permeation chromatography, with
a preferred number average molecular weight within the range of
about 1750 to about 4000 and a weight average molecular weight
within the range of about 3500 to about 9,000, as determined by gel
permeation chromatography. Alternatively, the intrinsic viscosity
(hereinafter "I.V.") of the low molecular weight PPE is most often
in the range of about 0.08-0.16 dl./g., preferably in the range of
about 0.10-0.14 dl./g., as measured in chloroform at 25.degree.
C.
[0020] The PPE are typically prepared by the oxidative coupling of
at least one monohydroxyaromatic compound such as 2,6-xylenol,
2,3,6-trimethylphenol, or mixtures of the foregoing. Catalyst
systems are generally employed for such coupling and they typically
contain at least one heavy metal compound such as a copper,
manganese, or cobalt compound, usually in combination with various
other materials.
[0021] It will be apparent to those skilled in the art from the
foregoing that the PPE contemplated in the present invention
include all those presently known, irrespective of variations in
structural units or ancillary chemical features.
[0022] The polymerization of the phenolic monomer may be carried
out by adding the phenolic monomer or monomers to a suitable
reaction solvent and preferably, a copper-amine catalyst. It is
preferred to carry out the polymerization in the presence of a
cupric or cuprous salt-secondary amine catalyst such as, for
example, cupric chloride and di-n-butylamine. The polymerizations
are advantageously carried out in the presence of an inorganic
alkali metal bromide or an alkaline earth metal bromide. The
inorganic bromides may be used at a level of from about 0.1 mole to
about 150 moles per 100 moles of phenolic monomer. These catalyst
materials are described in U.S. Pat. No. 3,733,299 (Cooper et al.).
Tetraalkylammonium salts may also be employed as promoters if
desired. These promoters are disclosed in U.S. Pat. No. 3,988,297
(Bennett et al.).
[0023] The primary, secondary or tertiary amine component of the
catalyst complex generally correspond to those disclosed in U.S.
Pat. Nos. 3,306,874 and 3,306,875 (Hay). Illustrative members
include aliphatic amines, including aliphatic mono- and di-amines,
where the aliphatic group can be straight or branched chain
hydrocarbon or cycloaliphatic. Preferred are aliphatic primary,
secondary and tertiary monoamines and tertiary diamines. Especially
preferred are mono-, di- and tri(lower) alkyl amines, the alkyl
groups having from 1 to 6 carbon atoms. Typically, there can be
used mono-, di- and tri-methyl, ethyl, n-propyl i-propyl, n-butyl
substituted amines, mono- and di-cyclohexylamine, ethylmethyl
amine, morpholine, N-(lower) alkyl cycloaliphatic amines, such as
N-methylcyclohexylamine, N,N'-dialkylethylenediamines, the
N,N'-dialkylpropanediamines, the N,N,N,'-trialkylpentanediamines,
and the like. In addition, cyclic tertiary amines, such as
pyridine, alpha-collidine, gamma picoline, and the like, can be
used. Especially useful are N,N,N',N'-tetraalkylethylenediamines,
butane-diamines, and the like.
[0024] Mixtures of such primary, secondary and tertiary amines may
be used. A preferred mono alkyl amine is n-butyl amine; a preferred
dialkyl amine is di-n-butyl amine; and a preferred trialkyl amine
is triethylamine. A preferred cyclic tertiary amine is pyridine.
The concentration of primary and secondary amine in the reaction
mixture may vary within wide limits, but is desirably added in low
concentrations. A preferred range of non-tertiary amines comprises
from about 2.0 to about 25.0 moles per 100 moles of monovalent
phenol. In the case of a tertiary amine, the preferred range is
considerably broader, and comprises from about 0.2 to about 1500
moles per 100 moles of monovalent phenol. With tertiary amines, if
water is not removed from the reaction mixture, it is preferred to
use from about 500 to about 1500 moles of amine per 100 moles of
phenol. If water is removed from the reaction, then only about 10
moles of tertiary amine, e.g., triethylamine or triethylamine, per
100 moles of phenol need be used as a lower limit. Even smaller
amounts of tertiary diamines, such as
N,N,N'N'-tetramethylbutanediamine can be used, down to as low as
about 0.2 mole per 100 moles of phenol.
[0025] Typical examples of cuprous salts and cupric salts suitable
for the process are shown in the Hay patents. These salts include,
for example, cuprous chloride, cuprous bromide, cuprous sulfate,
cuprous azide, cuprous tetramine sulfate, cuprous acetate, cuprous
butyrate, cuprous toluate, cupric chloride, cupric bromide, cupric
sulfate, cupric azide, cupric tetramine sulfate, cupric acetate,
cupric butyrate, cupric toluate, and the like. Preferred cuprous
and cupric salts include the halides, alkanoates or sulfates, e.g.,
cuprous bromide and cuprous chloride, cupric bromide and cupric
chloride, cupric sulfate, cupric fluoride, cuprous acetate and
cupric acetate. With primary and secondary amines, the
concentration of the copper salts is desirable maintained low and
preferably varies from about 0.2 to 2.5 moles per 100 moles of
monovalent phenol. With tertiary amines, the copper salt is
preferable used in an amount providing from about 0.2 to about 15
moles per 100 moles of the monovalent phenol.
[0026] Cupric halides are generally preferred over cuprous halides
for the preparation of the copper amine catalyst because of their
lower cost. The use of the copper (I) species also greatly
increases the rate of oxygen utilization in the early stages of the
polymerization reaction and the lower oxygen concentration in the
head space of the reactor helps in reducing the risk of fire or
explosion in the reactor. A process for the preparation and use of
suitable copper-amine catalysts is in U.S. Pat. No. 3,900,445
(Cooper et al.).
[0027] A faster initial reaction rate with the copper (I) based
catalyst also results in less accumulation of unreacted monomer and
a reduction in the amount of undesirable tetramethyldiphenylquinone
produced. The tetramethyldiphenylquinone, a backward dimer, is
believed to incorporate into the PPE through equilibration
reactions. The equilibration reactions lead to a drop in the
intrinsic viscosity of the PPE due to the decrease in molecular
weight of the PPE from the incorporation of the dimer. Minimization
of the tetramethyldiphenylquinone during the oxidation coupling is
desirable so as to avoid the drop in molecular weight and the
accompanying difficulties in having to build to a higher than
desired molecular weight to offset the loss during equilibration of
the backward dimer. It was unexpectedly found that the present
invention affords a process in which the PPE in the reaction
mixture shows less than a 10% drop, preferably less than a 5% drop,
most preferably less than a 3% drop in I.V. during an equilibration
step after the oxidative polymerization of the phenolic
monomers.
[0028] The polymerization reaction is preferably performed in a
solvent. Suitable solvents are disclosed in the above-noted Hay
patents. Aromatic solvents such as benzene, toluene, ethylbezene,
xylene, and o-dichlorobenzene are especially preferred, although
tetrachloromethane, trichloromethane, dichloromethane,
1,2-dichloroethane and trichloroethylene may also be used. The
weight ratio between solvent and monomer is normally in the range
from 1:1 to 20:1, ie. up to a maximum 20-fold excess of solvent.
The ratio between solvent and monomer is preferably in the range
from 1:1 to 10:1 by weight.
[0029] One unexpected advantage of the present process to make low
intrinsic viscosity PPE is that a higher solids loading is possible
as compared to processes that make higher (i.e. >0.28 I.V.) PPE.
Without the increased solution viscosity build that concomitantly
accompanies high molecular weight polymer, the final solids
concentration can be increased by at least 20%, with increases of
30% or more possible. Thus, the present process affords a method
for increased reactor utilization and productivity without
increasing the size or number of the reactor vessels.
[0030] The process and reaction conditions for the polymerization,
such as reaction time, temperature, oxygen flow rate and the like
are modified based on the exact target molecular weight desired.
The endpoint of the polymerization is conveniently determined with
an in-line viscosity meter. Although other methods such as making
molecular weight measurements, running to a predetermined reaction
time, controlling to a specified endgroup concentration, or the
oxygen concentration in solution may also be utilized.
[0031] The temperature to carry out the polymerization stage of the
invention generally ranges from about 0.degree. C. to about
95.degree. C. More preferably, the temperature range is from about
35.degree. C. to about 45.degree. C. with the higher reaction
temperature near the end of reaction. At substantially higher
temperatures, side reactions can occur leading to reaction
by-products and at temperatures substantially lower, ice crystals
form in the solution.
[0032] Many diverse extractants or chelating agents may be used in
the practice of the invention to complex with the catalyst after
the end of the polymerization reaction. For example, sulfuric acid,
acetic acid, ammonium salts, bisulfate salts and various chelating
agents may be used. When these materials are added to a PPE
reaction solution, the copper-amine catalyst becomes poisoned and
further oxidation does not take place. Many different materials may
be used but it is preferred to employ those chelating agents that
are disclosed in U.S. Pat. No. 3,838,102 (Bennett et al.).
[0033] The useful chelating agents include polyfunctional
carboxylic acid containing compounds such as, for example, sodium
potassium tartrate, nitrilotriacetic acid (NTA), citric acid,
glycine and especially preferably they will be selected from
polyalkylenepolyamine polycarboxylic acids, aminopolycarboxylic
acids, aminocarboxylic acids, aminopolycarboxylic acids,
aminocarboxylic acids, polycarboxylic acids and their alkali metal,
alkaline earth metal or mixed alkali metal-alkaline earth metal
salts. The preferred agents include ethylenediaminetetraacetic acid
(EDTA), hydroxyethylenediaminetriacetic acid,
diethylenetriaminepentaacetic acid and their salts. Especially
preferred are ethylenediaminotetraacetic acid or a mono-, di-, tri-
and tetrasodium salt thereof and the resulting copper complex can
be referred to as a copper carboxylate complex.
[0034] The chelated metallic catalyst component can be extracted
with the water produced in the polymerization reaction by through
the use of a liquid/liquid centrifuge. The preferred extraction
liquid for use in the process of the invention is an aqueous
solution of lower alkanol, i.e., a mixture of water and an alkanol
having from 1 to about 4 carbon atoms. Generally from about 1% to
about 80% by volume of an alkanol or glycol may be employed. These
ratios may vary from about 0.01:1 to about 10:1 parts by volume of
aqueous liquid extractant to discrete organic phase.
[0035] The reaction media generally comprises an aqueous
environment. Anti-solvents can also be utilized in combination with
the aqueous media to help drive the precipitation of the copper (I)
species. The selection of an appropriate anti-solvent is based
partially on the solubility co-efficient of the copper (I) species
that is being precipitated. The halides are highly insoluble in
water, log K.sub.[sp] values at 25.degree. C. are -4.49, -8.23 and
-11.96 for CuCl, CuBr and Cul, respectively. Solubility in water is
increased by the presence of excess of halide ions due to the
formation of, e.g., CuCl.sub.2, CUCl.sub.3, and CuCl.sub.4 and by
other complexing species. Non-limiting examples of anti-solvents
would comprise low molecular weight alkyl and aromatic
hydrocarbons, ketones, alcohols and the like which in themselves
would have some solubility in the aqueous solution. One skilled in
the art would be able to select an appropriate type and amount of
anti-solvent, if any was utilized.
[0036] One unexpected advantage of the present invention to make
low molecular weight PPE (i.e. PPE having an I.V. in the range of
about 0.08-0.16 dl./g.) is the reduction in I.V. variation and
molecular weight of the PPE after the end of reaction. In the
processes of the prior art to make higher intrinsic viscosity
resin, i.e. I.V.>0.28 dl/g., after the end of reaction the PPE
is held at elevated temperature, typically between about 45.degree.
C. to about 70.degree. C. for between about 45 to 90 minutes, while
the catalyst chelating species as described above is added and
allowed to react. During this equilibration process, the previously
described backward dimer phenols that are reaction by-products of
the oxidation process incorporate into the polymer backbone
resulting in a decrease in the molecular weight and I.V. of the
PPE. To illustrate this decrease, a PPE targeted to have an I.V, of
0.48 dl/g at the end of reaction will drop to an I.V. of about 0.38
dl/g after equilibration. Conversely, in the present invention, a
PPE having a target end of run I.V. of about 0.113 dl/g, after
equilibration will have an I.V. of about 0.115 dl/g. It should be
apparent that the present invention affords a method to prepare a
PPE that has less than about a 10% drop, preferably less than about
a 5% drop, and most preferably less than about a 3% drop in I.V.
during equilibration after the end of reaction.
[0037] After removal of the catalyst, the PPE containing solution
is concentrated to a higher solids level as part of the isolation
of the PPE. Precipitation using standard non-solvent techniques
typical for PPE having I.V.'s greater than 0.28 dl/g are not
generally useful for isolation of low molecular weight PPE due to
the small PPE particle size and friability of the particles. Very
low yields are obtained with undesirable fractionation of
oligomeric species. A total isolation process is preferred for
isolating the PPE. As part of the total isolation, a portion of the
solvent is preferably removed in order to reduce the solvent load
on the total isolation equipment.
[0038] Concentration of the PPE containing solution is accomplished
by reducing the pressure in a solvent flash vessel while preferably
increasing the temperature of the PPE containing solution.
Pressures of about 35 to 50 bar are desirable with solution
temperatures increased to at least 200.degree. C., preferably of at
least 230.degree. C. A solids level of PPE of at least 55%,
preferably of at least 65% or higher is desirable.
[0039] The isolation of the PPE is typically carried out in a
devolatilizing extruder although other methods involving spray
drying, wiped film evaporators, flake evaporators, and flash
vessels with melt pumps, including various combinations involving
these methods are also useful and in some instances preferred. As
previously described, total isolation is preferably from the
viewpoint that oligomeric species are not removed to the same
degree as with precipitation. Likewise, isolation yields are
extremely high and are near quantitative. These techniques require
however that the catalyst removal be completed in the prior process
steps as any catalyst remaining in solution will necessarily be
isolated in the PPE.
[0040] Devolatilizing extruders and processes are known in the art
and typically involve a twin-screw extruder equipped with multiple
venting sections for solvent removal. In the practice of the
present invention, the preheated concentrated solution containing
the PPE is fed into the devolatilizing extruder and maintained at a
temperature less than about 275.degree. C., and preferably less
than about 250.degree. C., and most preferably between about
185-220.degree. C. with pressures in the vacuum vent of less than
about 1 bar. The resultant solvent level is reduced to less than
about 1200 ppm, preferably less than about 600 ppm, and most
preferably less than about 400 ppm. Furthermore, it was unexpected
that temperatures as low as less than 250.degree. C. and preferably
between about 185-220.degree. C. would be useful and preferred as
current PPE having an I.V. of >0.28 dl/g generally require a
temperature of 300.degree. C. or higher in similar total isolation
processes.
[0041] Another unexpected result obtained through the use of a
devolatilizing extruder was the extremely high yield of PPE
achieved in the process. For example, a PPE yield of over 99% was
obtained even for PPE having a low I.V. whereas in the
precipitation process known in the art, the yield of similar low
I.V. PPE was less than 90%. Thus, the present process comprising a
devolatilizing extruder affords a method to prepare low molecular
weight polyphenylene ether resin, typically within the intrinsic
viscosity range of about 0.08 dl/g to about 0.16 dl/g, in a yield
of over 90%, preferably over 95%, more preferably over 98% and most
preferably over 99%, based upon the amount of monovalent phenol
utilized in the oxidative coupling.
[0042] When using a devolatilization extruder for the total
isolation of the PPE, it was found that traditional underwater or
water spray cooling of strands of extrudate followed by chopping
the extrudate into pellets gave unacceptable results presumably due
to the low melt strength and inherent brittle nature of low
molecular weight PPE. It was found that special pelletization
techniques can overcome these difficulties. Useful techniques
include die-face pelletization, including underwater pelletization
and flaking, declining angle strand pelletization using water
spraying, and vibration drop pelletization with underwater
pelletization especially suitable.
[0043] It was unexpectedly found that underwater pelletization
resulted in a significantly lower color in the PPE as compared to
the standard stranding with water/air cooling followed by
pelletization techniques. Yellowness index (YI) numbers of less
than 30, and even less than 25 are achievable as compared to
YI>50 achieved with the standard stranding technique. It should
be apparent that the present process affords a method of preparing
a PPE with a YI of less than about 30, preferably less than about
25.
[0044] Another unexpected benefit of underwater pelletization of
PPE, especially low I.V. PPE, is that very low (less than about 3%
by weight) fines, defined as pellets (i.e. particles) of less than
850 microns in size, could be obtained. It should be clear that the
present invention includes a method to reduce the number of fines
having a particle size less than about 850 micron in polyphenylene
ether wherein the method comprises underwater pelletization of the
polyphenylene ether resin. A preferred embodiment includes a method
to reduce the number of fines having a particle size less than
about 850 micron to less than about 3%, preferably less than about
1.5% by weight based on the total weight of the pellets.
[0045] The collected PPE pellets can be dried using techniques
standard in the art including centrifugal dryers, batch or
continuous oven dryers, fluid beds, and the like. Determination of
an appropriate set of conditions can be readily determined by one
of skill in the art without undue experimentation.
[0046] All patents cited by reference are incorporated herein by
reference.
[0047] In order that those skilled in the art will be better able
to practice the invention, the following examples are given by way
of illustration and not by way of limitation.
EXAMPLES
[0048] Polymerization Reaction
[0049] A typical laboratory reaction recipe and reaction conditions
are indicated below:
[0050] The catalyst solution can be prepared by stirring 0.41 g of
cuprous bromide and 10.9 g of di-n-butyl amine in 100 ml of
toluene. The catalyst is transferred to a one liter stirred glass
reactor equipped with an internal cooling coil and inlet tubes for
oxygen and monomer. A rapid stream of oxygen is introduced near the
bottom of the reactor and a solution of 70 g of 2,6-xylenol in 100
ml of toluene is added through a metering pump, over a in period of
fifteen minutes, to the rapidly stirred solution. The temperature
is maintained initially at about 40.degree. C. to about 45.degree.
C./48.degree. C. towards the end of the run by circulating water
from a constant temperature bath through the cooling coil.
Molecular weight build is continuously monitored with a typical
reaction time to target I.V. of about 100-107 minutes.
[0051] Although the conditions are for a laboratory scale reaction
they in general scaleable to commercial processes carried out in
commercial equipment without undue burden by one of skill in the
art.
[0052] Equilibration
[0053] In the glass reactor vessel, the copper catalyst was
complexed by the addition of a complexant like nitrilotriacetic
acid (NTA) or other copper complexing agent in order to solubilize
it in the aqueous liquid phase.
1 Mixing time: ca. 70 min. Temperature: ca. 55.degree. C.
[0054] Removal of Complexed Catalyst
[0055] Typical conditions for a liquid/liquid centrifuge on a
commercial scale are as indicated below.
2 PPE solution feed rate to the 1.sup.st L/L centrifuge: 10
m.sup.3/hr water feed rate to the 1.sup.st L/L centrifuge: 100-200
l/hr PPE solution feed rate to the 2.sup.nd L/L centrifuge: 0.5-0.8
m.sup.3/hr water feed rate to the 2.sup.nd L/L centrifuge 100
l/hr
[0056] Typical residual water and copper contents achieved after
the 1.sup.st centrifuge are water as low as 1500 ppm and copper as
low as 0.2 ppm. Surprisingly it was found that the feed can be
recirculated constantly over the centrifuge, without negative
effect on the ease of separation or emulsion formation tendency,
hence achieving multiple extraction steps. In the feed to the
2.sup.nd nd centrifuge only water, without additional NTA is
added.
[0057] Preconcentration
[0058] Typical conditions for a commercial scale are as follows.
The PPE containing solution is preheated to a temperature of at
least 240.degree. C. a pressure of ca. 40 bar. The solution is
flashed to low pressure in a flash vessel a PPE solids content of
at least about 65%. The high solids level is desirable to reduce
the solvent load to the total isolation equipment that would have
been present without preconcentration. Typical conditions are
tabulated below:
3 P before the flash vessel: 40 bar T before the flash vessel:
245-260.degree. C. Feedrate to the flash tank: 0.7-.87 ton/hr T
after the flash vessel 114-126.degree. C.
[0059] Total Isolation
[0060] The isolation is preferably carried out in a devolatilizing
extruder. The preferred devolatilizing extruder is a co-rotating
twin screw extruder with a backfeed capability. Multiple
devolatilizing venting sections are preferred to achieve low
volatiles content.
[0061] Typical settings are indicated in the table below.
4 T zone 1 ca. 200.degree. C. T zone 2 ca. 200.degree. C. T zone 3
ca. 200.degree. C. T zone 4 ca. 195-200.degree. C. T zone 5 ca.
195-200.degree. C. T zone 6 ca. 200.degree. C. T zone 7 ca.
200.degree. C. T zone 8 ca. 200.degree. C. T zone 9 ca. 200.degree.
C. P back vent ca. 0.8 bar P 1.sup.st vacuum vent ca. 0.8 bar P
2.sup.nd vacuum vent ca. 0.7 bar p 3.sup.rd vacuum vent ca.
0.72-0.75 bar Screw rpm ca. 294 Extruder Torque ca. 30-38% Extruder
motor Amp ca. 85-106
[0062] It was unexpected that such very low temperatures could be
used while still maintaining excellent low residual solvent levels
in the end product. PPE grades known in the art and having I.V.'s
of at least 0.28 dl/g are isolated at 300.degree. C. or above under
similar conditions.
[0063] Other configurations and modifications can be used as well,
like different size and number of venting ports, other screw
design, sequence of feed and venting sections. Also the preheated
feed solution can be added in any solvent concentration with
flashing either partly or totally in the devolatizing extruder.
[0064] Pelletization
[0065] The low melt strength of the low molecular weight PPE's
requires special pelletization techniques compared to normal IV
grade PPE materials. The table below shows typical settings for the
underwater pelletizer:
5 Product throughput: ca. 240 kg/hr Melt pump feed ca. 6 bar
pressure: Melt pump product ca. 95-100 bar pressure: Die
temperature: ca. 300.degree. C. Water addition rate: ca. 10
m.sup.3/hr Rotating knife rpm: ca. 3600 Water temperature: ca.
90.degree. C. Centrifugal dryer rpm: ca. 450
[0066] The pelletized low molecular weight PPE, which is inherently
very brittle, unexpectedly had a low content of fines. Fines levels
of less than 3% by weight below 850 micron, preferably less than 2%
by weight, and most preferably less than about 1.1% by weight can
be achieved by the process. Modifications are achievable without
undue experimentation of the die design, rotating knife speed,
temperature and throughput, the particle size can be readily
controlled to desired values.
[0067] In order to further highlight some of the unexpected results
obtained in the present process, the following tables compare
various properties and characteristics obtained for low molecular
weight PPE as compared to a PPE having an I.V. of 0.48 dl/g
prepared as described by methods known in the art.
[0068] The table below compares two batches of low molecular weight
with an end of reaction I.V. of about 0.11 dl/g to a batch of high
molecular weight PPE having an end of reaction I.V. of about 0.48
dl/g. After equilibration, the I.V. of the high molecular weight
has dropped by approximately 20% whereas the low molecular weight
PPE batches have remained constant within experimental error of the
test method. After the PPE samples had been treated to thermal
processing in the melt, the low molecular weight PPE samples again
remain fairly stable in I.V. with less than 5% increase in I.V.
Conversely, the high molecular weight PPE has an increase in I.V.
from about 0.38 after equilibration to about 0.485 after melt
processing, an increase of about 25%. It was unexpected that the
low molecular weight PPE prepared in the present process would have
an I.V. that varied less than about 5% throughout equilibration and
thermal processing (heating into the melt for about 0.2 minutes to
about 20 minutes, ca. 200.degree. C. for low molecular weight and
ca. 300.degree. C. for high molecular weight).
6 I.V. at end I.V. after I.V. after thermal of reaction
equilibration processing PPE Grade (dl/g) (dl/g) (dl/g) Low
molecular weight 0.113 0.115 0.116-0.122 PPE batch 1 Low molecular
weight 0.114 0.116 0.116-0.122 PPE batch 2 High molecular 0.48 0.38
0.485 weight PPE
[0069] It should be clear from the data in the above table that the
present invention include a method to prepare a low molecular
weight PPE that has less than about 3% change in I.V. through
equilibration. It should also be clear that the present invention
also includes a method to prepare a low molecular weight PPE that
has less than about 5% change in I.V. after equilibration and
through thermal processing. Furthermore, it should also be clear
that the present invention includes a PPE that has less than about
3% change in I.V. through equilibration. Also it should be clear
that the present process also includes a polyphenylene ether resin
having less than about a 10% change in intrinsic viscosity after an
equilibration step following the oxidative coupling and after a
thermal treatment at 200.degree. C. for about 0.2 minutes to about
20 minutes.
[0070] The table below compares the level of copper remaining after
the catalyst extraction steps. As can be seen from these data, the
low molecular weight PPE has less than half the amount of residual
copper remaining in the final isolated product. It was unexpected
that the I.V. of the PPE would have an effect for improving the
catalyst removal.
7 ppm Cu PPO solution after 1.sup.st PPE Grade centrifuge ppm Cu
final product Low molecular weight 0.2-2 1-3 PPE (0.11 dl/g) High
molecular ca. 5 ca. 8 weight PPE (0.48 dl/g)
[0071] The table below compares the devolatilization extruder
temperature range and residual toluene level remaining in the final
isolated PPE. It was unexpected that the extruder could be operated
at a lower temperature range and obtain residual solvent levels
that are as good or better than obtained with higher temperatures
for a higher (0.48 I.V.) molecular weight PPE. It should be noted
that the extruder cannot be operated at the lower temperature range
with 0.48 I.V. PPE without exceeding the torque rating of the
machine.
8 Extruder zone ppm toluene in final PPE Grade Temperature range
product Low molecular weight 195-200.degree. C. 260-450 PPE (0.11
dl/g) High molecular 245-300.degree. C. ca. 300-500 weight PPE
(0.48 dl/g)
[0072] The following table compares the level of dibutylamine (DBA)
incorporated in the low molecular weight PPE of the present
invention as compared to the level incorporated into high molecular
weight (0.48 I.V.) PPE. It was unexpected that such low levels
would remain in the low molecular weight PPE. It should be clear
from these data that the present process affords a more cost
effective and environmentally friendly PPE process as a larger
proportion of the dibutylamine remains with the solvent stream and
can be recovered and recycled.
9 DBA content of final PPE Grade product Low molecular weight
0.15-0.28% PPE (0.11 dl/g) High molecular 0.9-1.0% weight PPE (0.48
dl/g)
[0073] Thus, the present invention includes a process to make low
I.V. PPE having an incorporated amine level of less than about 0.3%
by weight based on the weight of the PPE.
[0074] These and other embodiments should be apparent from the
disclosure contained herein.
* * * * *