U.S. patent application number 11/446368 was filed with the patent office on 2007-01-04 for process for the preparation of high-purity bisphenol a.
Invention is credited to Raymond Audenaert, Ulrich Blaschke, Arne Braun, Stefan Westernacher, Jesko Zank.
Application Number | 20070004941 11/446368 |
Document ID | / |
Family ID | 36753956 |
Filed Date | 2007-01-04 |
United States Patent
Application |
20070004941 |
Kind Code |
A1 |
Blaschke; Ulrich ; et
al. |
January 4, 2007 |
Process for the preparation of high-purity bisphenol A
Abstract
A process for the preparation of high purity bisphenol A is
disclosed. The multi-step process entails a process whereby
bisphenol A of a purity of preferably at least 99.8% can be
obtained.
Inventors: |
Blaschke; Ulrich; (Krefeld,
DE) ; Westernacher; Stefan; (Kempen, DE) ;
Braun; Arne; (Leverkusen, DE) ; Audenaert;
Raymond; (Hamme, BE) ; Zank; Jesko; (Koln,
DE) |
Correspondence
Address: |
BAKER DONELSON BEARMAN CALDWELL & BERKOWITZ, PC
555 11TH STREET, NW
6TH FLOOR
WASHINGTON
DC
20004
US
|
Family ID: |
36753956 |
Appl. No.: |
11/446368 |
Filed: |
June 5, 2006 |
Current U.S.
Class: |
568/728 |
Current CPC
Class: |
C07C 37/20 20130101;
C07C 37/20 20130101; C07C 37/84 20130101; C07C 37/84 20130101; C07C
39/16 20130101; C07C 39/16 20130101; C07C 39/16 20130101 |
Class at
Publication: |
568/728 |
International
Class: |
C07C 39/16 20060101
C07C039/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2005 |
DE |
102005025788.7 |
Claims
1. A process for the preparation of bisphenol A comprising: a)
reacting phenol with acetone in the presence of an acidic ion
exchanger and a sulfur-containing co-catalyst to produce a product
mixture comprising bisphenol A, phenol, BPA isomers, un-reacted
acetone, and water; b) continuously obtaining from the product
mixture crystals of bisphenol A-phenol adduct by suspension
crystallization in at least one crystallizer provided with at least
one heat exchanger, said product mixture containing 0.1 to 6% by
weight of water, c) separating the adduct obtained in (b) by a
first solid-liquid separation to obtain a first solid phase and a
first liquid phase, d) washing the first solid phase with a
solution comprising phenol to obtain a washed solid phase and a
second liquid phase, e) distilling the first liquid phase and said
second liquid phase to obtain a dewatered solution comprising 5 to
15 wt.-% p,p-BPA, 3 to 12 wt.-% isomers of BPA and less than 0.3
wt.-% water, the percentages based on the weight of the dewatered
solution, f) optionally introducing at least 90 wt.-% by weight of
the dewatered solution into (a), g) adding phenol to the washed
solid phase obtained in (d) to obtain a homogeneous material system
comprising 15 to 35 wt.-% p,p'-BPA, 0.05 to 2 wt.-% isomers of BPA
and 0.1 to 10 wt.-% water, h) continuously obtaining from the
homogeneous material system crystals of bisphenol A-phenol adduct
by suspension crystallization in at least one crystallizer provided
with at least one heat exchanger, i) separating the crystals
obtained in (h) by a second solid-liquid separation to obtain a
second solid phase, j) washing the second solid phase with a
solution comprising phenol to obtain a washed adduct, and k)
optionally heating the washed adduct to at least 120.degree. C. to
at least potentially remove phenol.
2. A process according to claim 1, wherein 50 to 90 wt.-%, of a
liquid phase obtained in (i) and (j) is used in (g).
3. A process according to claim 1, wherein 10 to 50 wt.-%, of a
liquid phase obtained in (i) and (j) is recycled into (d) for
washing.
4. A process according to claim 1, wherein the solution comprising
phenol in (j) comprises not more than 1.0% by weight of
isopropenylphenol BPA and isomers thereof, and any secondary
components.
5. A process according to claim 1, wherein the washed solid phase
obtained in (d) is first melted before phenol is added in (g).
6. A process according to claim 1, wherein at least one of said
first and/or second solid-liquid separation is carried out in a
vacuum rotary filter.
7. A process according to claim 1, wherein the solution comprising
phenol of (d) comprises 84 to 99.45 wt.-% phenol, 0.5 to 15 wt.-%
BPA and 0.05 to 1.0 wt.-% BPA isomers, the percentages based on the
weight of all components of the solution except water.
8. A process according to claim 1, wherein the solution comprising
phenol of (d) comprises 0.05 to 12 wt.-% water, the percentage
based on the total weight of said solution.
9. A process according to claim 1, wherein 5 to 100 wt.-% of the
solution comprising phenol of (d) originates from (i) and (j).
10. A process according to claim 1, wherein the crystallization of
(b), is carried out in two steps in series at temperatures that
differ one from the other, and wherein the crystallization of (h)
is carried out in one step in at least two crystallizers operating
in parallel.
11. A process according to claim 1, wherein the material system of
(g) comprises at most 5 wt.-% acetone, the percentage based on the
weight of the system.
12. A process according to claim 1, wherein at least part of a
liquid phase from the solid-liquid separation of (i) and at least
part of a liquid phase from washing in (j) are collected
separately, at least part of the liquid phase from the solid-liquid
separation of (i) is recycled into (d) and/or at least part of the
liquid phase from the washing is recycled into (g).
13. A process according to claim 1, wherein 0 to 35 wt.-%, of
liquid phases obtained in (i) and/or (O) is evaporated, such that a
top product is passed to (d) and/or (f) and a bottom product is
recycled upstream of (b).
14. A bisphenol-A product produced in a single production facility
having a purity of at least 99.8% p,p' bisphenol A, a color index
at most 20 Hazen units and a temperature stability of not more than
40 Hazen units; said percentage based on the weight of the product
except phenol.
15. A bisphenol-A product of claim 14, that has been produced by at
least two crystallization steps.
16. A process for producing BPA with two categories of purity, said
process comprising conducting a one stage and a two stage
crystallization and a product work-up to produce BPA having a
purity of 99.5-99.75%, and conducting a one stage and a two stage
crystallization and a product work-up to produce BPA with a purity
of at least 99.8%.
17. A process of claim 16 wherein said crystallizations are all
conducted in the same production facility.
18. A process for the preparation of bisphenol A comprising: a)
reacting phenol with acetone in the presence of an acidic ion
exchanger and a sulfur-containing co-catalyst to produce a product
mixture comprising bisphenol A, phenol, BPA isomers, un-reacted
acetone, and water; b) continuously obtaining from the product
mixture crystals of bisphenol A-phenol adduct by suspension
crystallization in at least one crystallizer provided with at least
one heat exchanger, said product mixture containing 0.1 to 6% by
weight of water, c) separating the adduct obtained in (b) by a
first solid-liquid separation to obtain a first solid phase and a
first liquid phase, d) washing the first solid phase with a
solution comprising phenol to obtain a washed solid phase and a
second liquid phase, e) distilling the first liquid phase and said
second liquid phase to obtain a dewatered solution comprising less
than 0.3 wt.-% water, the percentages based on the weight of the
dewatered solution, f) optionally introducing at least a portion of
the dewatered solution into (a), g) adding phenol to the washed
solid phase obtained in (d) to obtain a homogeneous material system
comprising 15 to 35 wt.-% p,p'-BPA, 0.05 to 2 wt.-% isomers of BPA
and 0.1 to 10 wt.-% water, h) continuously obtaining from the
homogeneous material system crystals of bisphenol A-phenol adduct
by suspension crystallization in at least one crystallizer provided
with at least one heat exchanger, i) separating the crystals
obtained in (h) by a second solid-liquid separation to obtain a
second solid phase, j) washing the second solid phase with a
solution comprising phenol to obtain a washed adduct, and k)
optionally heating the washed adduct to at least 120.degree. C. to
at least partially remove phenol.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to German Application No.
1020050257887 filed Jun. 4, 2005, the content of which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a process and in particular to a
process for preparing bisphenol A.
[0004] 2. Description of Related Art
[0005] 2,2-Bis(4-hydroxyphenyl)propane (bisphenol A, BPA), which is
the condensation product of phenol and acetone, is a starting
material or intermediate for the preparation of a large number of
commercial products. Thus it is used as a starting material for the
preparation of various types of polymeric materials, for example
polyarylates, polyetherimides, polysulfones and modified
phenol-formaldehyde resins. Preferred fields of application are in
the preparation of epoxy resins and polycarbonates.
[0006] Technically relevant methods of preparing BPA are known,
e.g. WO 00/35847 and U.S. Pat. No. 2,775,620.
[0007] After the acid-catalyzed reaction of phenol with acetone,
BPA is separated from the product mixture in the form of a
crystalline adduct of BPA and phenol. Phenol is completely or
partially removed from these crystals of BPA-phenol adduct by
distillative, desorptive or extractive methods. Before the
separation from phenol, the crystals of BPA-phenol adduct may also
be subjected to additional purification steps to reduce the
concentration of secondary components.
[0008] The crystals of BPA-phenol adduct may be recrystallized e.g.
from phenol, organic solvents or mixtures of these solvents. The
phenol present in the adduct crystals may also be completely or
partially separated off using an appropriate solvent.
[0009] PL 159620 describes a laborious process for the purification
of bisphenol A wherein the crystals of BPA-phenol adduct isolated
in a first stage are dissolved in phenol and the resulting solution
is cooled in a batch crystallizer in a system similar to a static
multilayer crystallization process, wherein crystals of BPA-phenol
adduct growing on the tubes. When the mother liquor has been
drained off, the crystals of BPA-phenol adduct recrystallized in
this way are washed with phenol and water in order to remove any
mother liquor still adhering to crystals. Alternatively, or in
addition, the crystals can be purified further by heating to a
temperature of 75 to 85.degree. C., i.e. by exudation. However, as
the process has to be carried out batchwise, equipment costs are
typically high. Moreover, the production outputs based on the
heat-transfer area are an order of magnitude lower in a process
according to PL '620 than in a continuous suspension
crystallization process used to produce crystals of BPA-phenol
adduct. Furthermore, an acceptable space-time yield requires high
cooling rates, so a multilayer crystallization of this type has to
take place at substantially higher crystal growth rates than a
continuous suspension crystallization. The resultant increased
incorporation of impurities into the crystals has to be compensated
by time-intensive exudation and/or washing operations. If a high
purity is required, it may be necessary to use a multistage
process.
[0010] EP 718 268 A describes a process for the preparation of a
crystalline adduct of bisphenol A and phenol wherein BPA dissolved
in phenol is first crystallized out as an adduct and filtered off.
It is then redissolved in phenol, crystallized out again and
filtered off, and the step of recrystallization being repeated
several times. In the last step of the multistage
recrystallization, the adduct is washed with specially purified
phenol. The washing liquids and filtrates for washing and
dissolving the adducts are at least partially recycled.
[0011] WO 02/40435 describes a process wherein high-purity
bisphenol A is obtained by multiple recrystallization from phenol
and washing of the adducts in individual stages with high-purity
phenol in a cross-flow washing plant. The phenol used as washing
phenol contains virtually no bisphenol A or isomers thereof. A
multiple recrystallization is preferred. Washing with high-purity
phenol at each of the individual stages requires a very large
amount of high-purity phenol. Furthermore, a large amount of
bisphenol A is dissolved in the phenol at each individual stage,
resulting in losses of yield.
[0012] WO 03/82785 describes a process for the preparation of
bisphenol A wherein in the first step a suspension of crystals of
BPA-phenol adduct is filtered under vacuum and washed, and the
resulting filter cake is dissolved in a liquid containing phenol
and crystallized again. The crystals obtained are separated off by
centrifugation. However, the continuous (filter) centrifuges that
are more economical for larger plant capacities demand a minimum
crystal size, which requires special crystallization
procedures.
[0013] EP 1 367 043 A describes a process for the purification of
bisphenol A wherein the crystals of BPA-phenol adduct are dissolved
in phenol and the resulting solution is filtered at least once
before the crystals of BPA-phenol adduct are crystallized out
again.
SUMMARY OF THE INVENTION
[0014] A process for the preparation of high purity bisphenol A is
disclosed. The multi-step process entails a) reacting phenol with
acetone in the presence of an acidic ion exchanger and a
sulfur-containing co-catalyst to give a product mixture that
includes bisphenol A and phenol; b) continuously obtaining from the
product mixture crystals of bisphenol A-phenol adduct by suspension
crystallization, c) separating the adduct obtained in step (b) by
solid-liquid separation to obtain a solid phase and a liquid phase
d) washing of the solid phase with a solution containing phenol to
obtain washed solid phase and a second liquid phase, e) distilling
the liquid phase and said second liquid phase to obtain dewatered
solution containing 5 to 15% p,p-BPA, 3 to 12% isomers of BPA and
less than 0.3% water, f) introducing of at least 90% by weight of
the dewatered solution into step (a), g) adding phenol to the
washed solid phase obtained in step d) to obtain a homogeneous
material system that contains p,p'-BPA, isomers of BPA and water h)
continuously obtaining from the homogeneous material system
crystals of bisphenol A-phenol adduct by suspension
crystallization; i) separating the crystals obtained in step (h) by
solid-liquid separation to obtain a second solid phase, j) washing
the second solid phase with a solution that contains phenol to
obtain a washed adduct; and k) heating the washed adduct to remove
phenol.
[0015] Additional objects, features and advantages of the invention
will be set forth in the description which follows, and in part,
will be obvious from the description, or may be learned by practice
of the invention. The objects, features and advantages of the
invention may be realized and obtained by means of the
instrumentalities and combination particularly pointed out in the
appended claims.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0016] An object of the present invention was to provide a simple
process for the preparation of high-purity bisphenol, especially
bisphenol A, with a purity of preferably at least 99.8%, to give a
low color index and a high temperature stability in the melt.
[0017] A low color index is understood as meaning a color index of
at most 20 Hazen units. To determine the color index, 10 g of
bisphenol A are melted under air in an oil bath at a temperature of
175.degree. C. over 20 minutes, after which the color index is
determined immediately according to ASTM D 1209. To determine the
temperature stability, this material is then heated for 4.5 h at a
bath temperature of 175.degree. C., after which the color index is
measured again. A high temperature stability is understood as
meaning that the color index increases by at most 40 Hazen
units.
[0018] The invention provides a process for the preparation of
bisphenol A advantageously comprising the following steps: [0019]
a) reacting phenol with acetone in the presence of an acidic ion
exchanger and a sulfur-containing co-catalyst to give a product
mixture that includes bisphenol A, phenol, BPA isomers, un-reacted
acetone, and water, [0020] b) continuously obtaining from the
product mixture crystals of bisphenol A-phenol adduct by suspension
crystallization in at least one crystallizer equipped with at least
one heat exchanger, said product mixture containing 0.1 to 6% by
weight of water, [0021] c) separating the adduct obtained in step
(b) by solid-liquid separation to obtain a first solid phase and a
first liquid phase, [0022] d) washing of the first solid phase with
a solution containing phenol to obtain a washed solid phase and a
second liquid phase, [0023] e) distilling the first liquid phase
and said second liquid phase to obtain dewatered solution
comprising 5 to 15 wt.-% p,p-BPA, 3 to 12 wt.-% isomers of BPA and
less than 0.3 wt.-% water, the percentages based on the weight of
the dewatered solution, [0024] f) optionally introducing of at
least 90 wt.-% by weight of the dewatered solution into step (a),
[0025] g) adding phenol to the washed solid phase obtained in step
d) to obtain a homogeneous material system comprising 15 to 35
wt.-% p,p'-BPA, 0.05 to 2 wt.-% isomers of BPA and 0.1 to 10 wt.-%
water, [0026] h) continuously obtaining from the homogeneous
material system crystals of bisphenol A-phenol adduct by suspension
crystallization in at least one crystallizer equipped with at least
one heat exchanger, [0027] i) separating the crystals obtained in
step (h) by solid-liquid separation to obtain a second solid phase,
[0028] j) washing the second solid phase with a solution that
contains phenol to obtain a washed adduct, and [0029] k) heating
the washed adduct to at least 120.degree. C. to remove phenol.
[0030] According to a further embodiment, there is provided a
process for the preparation of bisphenol A comprising: [0031] a)
reacting phenol with acetone in the presence of an acidic ion
exchanger and a sulfur-containing co-catalyst to produce a product
mixture comprising bisphenol A, phenol, BPA isomers, un-reacted
acetone, and water; [0032] b) continuously obtaining from the
product mixture crystals of bisphenol A-phenol adduct by suspension
crystallization in at least one crystallizer provided with at least
one heat exchanger, said product mixture containing 0.1 to 6% by
weight of water, [0033] c) separating the adduct obtained in (b) by
a first solid-liquid separation to obtain a first solid phase and a
first liquid phase, [0034] d) washing the first solid phase with a
solution comprising phenol to obtain a washed solid phase and a
second liquid phase, [0035] e) distilling the first liquid phase
and said second liquid phase to obtain a dewatered solution of BPA
and isomers thereof, preferably 5 to 15 wt.-% p,p-BPA, 3 to 12 wt.
% isomers of BPA and less than about 0.3 wt.-% water, the
percentages based on the weight of the dewatered solution, [0036]
f) optionally introducing at least a portion of, or at least 90
wt.-% by weight of the dewatered solution into (a), [0037] g)
adding phenol to the washed solid phase obtained in (d) to obtain a
homogeneous material system comprising 15 to 35 wt.-% p,p'-BPA,
0.05 to 2 wt.-% isomers of BPA and 0.1 to 10 wt.-% water, [0038] h)
continuously obtaining from the homogeneous material system
crystals of bisphenol A-phenol adduct by suspension crystallization
in at least one crystallizer provided with at least one heat
exchanger, [0039] i) separating the crystals obtained in (h) by a
second solid-liquid separation to obtain a second solid phase,
[0040] j) washing the second solid phase with a solution comprising
phenol to obtain a washed adduct, and [0041] k) optionally heating
the washed adduct to at least 120.degree. C. to at least
potentially or partially remove phenol.
[0042] A process according to the present invention affords a
bisphenol A with a purity of preferably at least 99.8 wt-% of
p,p-BPA, based on all the components contained in the product,
except phenol.
[0043] In step (a) of a process according to the invention, the
reaction of phenol and acetone advantageously takes place in the
presence of an acidic ion exchanger and a sulfur-containing
co-catalyst to give a product mixture containing bisphenol A. Step
(a) is based on the acid-catalyzed reaction of phenol with acetone,
and the phenol/acetone ratio in the reaction is preferably adjusted
to at least 5:1. The reaction is conventionally carried out
continuously and generally at temperatures from 45 to 110.degree.
C., preferably from 50 to 80.degree. C. Acidic catalysts used are
suitably gel-like (microporous) or macroporous sulfonated
crosslinked polystyrene resins (acidic ion exchangers), which may
be either monodisperse or heterodisperse as desired. Divinylbenzene
is normally used as the crosslinking agent, but other crosslinking
agents, such as divinylbiphenyl, may also be used if desired for
any reason. The catalyst is advantageously used together with a
co-catalyst, which conventionally is a thiol carrying at least one
SH group and having a positive influence on both the selectivity
and the reactivity of the reaction. The co-catalyst may be in any
form, such as homogeneously dissolved in the reaction solution or
fixed to the catalyst itself. Examples of suitable homogeneous
co-catalysts include mercaptopropionic acid, hydrogen sulfide,
alkyl sulfides or alkylsilylthiols, such as ethyl sulfide or
silylmethanethiol and similar compounds. Fixed co-catalysts include
aminoalkylthiols and pyridylalkylthiols ionically bonded to the
catalyst, it being possible for the SH group to be protected and to
be freed only during or after fixation to the catalyst, e.g. as in
the case of dimethylthiazolidine and alkylcarbamoylalkylthio
esters. The co-catalyst may also be covalently bonded to the
catalyst as an alkylthiol or arylthiol, or be a constituent of the
catalyst. It is also possible for two or more co-catalysts to be
used together.
[0044] Apart from unreacted phenol and optionally acetone, the
product mixture formed in the reaction of phenol with acetone in
the presence of acidic catalysts preferably contains essentially
BPA and water. These are accompanied by small amounts of isomers as
typical by-products of the condensation reaction, examples being
2-(4-hydroxyphenyl)-2-(2-hydroxyphenyl)propane (o,p-BPA),
substituted indanes, hydroxyphenylindanols, hydroxyphenylchromans,
spiro-bis-indanes, substituted indenols, substituted xanthenes and
more highly condensed compounds having three or more phenyl rings
in the molecular skeleton. Other secondary components, such as
anisole, mesityl oxide, mesitylene and diacetone alcohol, may also
form due to autocondensation of the acetone and reaction with
impurities in the raw materials.
[0045] The reaction in step (a) may advantageously be carried out
in such a way that the acetone is completely converted. For
economic and technical reasons, however, it is usually carried out
so that, rather than 100% of the acetone being converted, up to 1.0
wt-% of acetone still remains in the reactor outflow.
[0046] If desired, the reaction may also take place in several
reactors connected in series. The total amount of acetone is
preferably distributed so that acetone is metered in before the
reaction mixture enters each reactor.
[0047] By-products, as well as the unreacted starting materials
such as phenol and acetone, can detract from the suitability of BPA
in some cases for the preparation of polymers and have to be
separated off by suitable processes because high purity demands are
made on the BPA, especially for the preparation of
polycarbonate.
[0048] From the product mixture obtained in step (a), which
contains 0.1 to 6 wt-% and preferably 0.5 to 2 wt-% of water,
crystals of bisphenol A-phenol adduct are crystallized out in step
(b) by continuous suspension crystallization. The product mixture
obtained in step (a) is not subjected to distillation upstream of
step (b) or (c) to remove readily volatile constituents (including
water).
[0049] The crystallization may take place in one or more
crystallizers connected in series. Any crystallizer known to those
of skill in the art can advantageously be used as well as any
devise that can achieve the desired crystallization to produce
bisphenol A. The mean total residence time of the crystals in this
crystallization stage is preferably 30 minutes to ten hours. With a
correspondingly slow crystallization, the inclusion of mother
liquor and the incorporation of impurities into the crystals of
BPA-phenol adduct may be avoided to a large extent. Cooling can be
effected indirectly if desired such as by using at least one heat
exchanger. In the crystallization, the product mixture can be
cooled to 40 to 50.degree. C. in one crystallization step.
Preferably, however, the crystallization takes place in two steps,
the product mixture being cooled to a temperature of 50 to
65.degree. C. in a first step and then to a temperature of 40 to
50.degree. C. in a second step. In both embodiments, the cooling
can be effected by using one or more heat exchangers per
crystallizer.
[0050] In one preferred embodiment, the temperature of the product
mixture can be adjusted upstream of step (b) to a temperature that
is preferably at most 5.degree. C. above the crystallization point
of the mixture.
[0051] Any subsequent solid-liquid separation, especially
filtration in step (c), and washing in step (d) may be carried out
e.g. in or on one of the following representative types of
apparatus: continuous filter centrifuges such as screen-conveyor
centrifuges or pusher centrifuges, batch filter centrifuges such as
skimmer centrifuges, and continuous filters such as rotary or drum
filters, belt filters and disk filters. It may be preferable in
some cases to use rotary filters, and particularly vacuum rotary
filters.
[0052] In the case of filtration using a vacuum rotary filter,
filtration is preferably carried out as described in DE 199 61 521
A, the content of which is incorporated herein by reference.
[0053] The washing of the solid phase, especially the filter cake,
can be effected by employing a phenolic solution, which extensively
displaces the mother liquor remaining in the filter cake and frees
the crystals of BPA-phenol adduct from impurities adhering to the
surface thereof. The filter cake may be washed with a single
phenolic solution or several phenolic solutions of different
compositions, which can suitably be applied successively or as a
mixture, e.g. via spray nozzles. Averaged over the total amount
used, the phenolic solution preferably contains 84 to 99.45 wt-% of
phenol, 0.5 to 15 wt-% of BPA and 0.05 to 1.1 wt-% of isomers.
These concentrations are based on the total weight of the phenolic
solution without water. The phenolic solution used preferably
contains 0.05 to 12 wt-% water, preferably 0.2 to 3 wt-% of water,
based on the total amount (of phenolic solution), and 5 to 100 wt-%
thereof preferably originates from step (i) and/or (O). The
temperature of the washing liquid is preferably from 40 to
85.degree. C., and particularly preferably from 45 to 70.degree. C.
In the case of a rotary filter, part of the phenolic solution from
step (i) and/or (j) may be used for rinsing the rotary filter in
step (c) and (d), or any part thereof such as a cloth.
[0054] The adduct crystals obtained in step (d) can be present in
the form of a filter cake moistened with phenol, and in this case
preferably have a BPA purity of at least 99 wt-%, based on the sum
of BPA and all other components. The residual moisture in the
filter cake as a proportion by weight of the liquid adhering to the
crystals of BPA-phenol adduct, based on the total weight of moist
filter cake, is preferably below 40 wt-% and more preferably 15 to
30 wt-%. Preferably, the amount of phenolic solution for washing
the filtered crystals of bisphenol A-phenol adduct is chosen so
that the amount of washing liquid advantageously corresponds to 20
to 120 wt-% of the amount of filtered crystals of BPA-phenol
adduct. The amount used is preferably 50 to 90 wt-%.
[0055] Preferably, water can be completely or partially removed by
distillation from the liquid phase obtained in step (c) and (d)
from the solid-liquid separation and/or the washing, especially
down to a content of 0 to 0.3 wt-%, after which optionally at least
90 wt-% thereof is advantageously recycled into step (a),
optionally after the addition of acetone, phenol and/or a
homogeneous co-catalyst. The recycled solution contains preferably
5 to 15 wt-% and particularly preferably 6.5 to 10 wt-% p,p'-BPA
and 3 to 12 wt-% isomers, obtained in step (e).
[0056] In the next step, (g), a, homogeneous solution containing,
inter alia, preferably 15 to 35 wt-% and particularly preferably 20
to 30 wt-% BPA and preferably 0.05 to 2 wt-% and particularly
preferably 0.1 to 1.1 wt-% isomers, is prepared by adding a
phenolic solution to crystals of BPA-phenol adduct obtained in step
(d). This can be done by mixing the crystals of BPA-phenol adduct
with a phenolic solution, the temperature of the resulting solution
preferably being 70 to 100.degree. C., and advantageously being
adjusted so that the homogeneous solution is subsaturated.
[0057] In one preferred embodiment, the crystals of BPA-phenol
adduct moistened with phenol from step (d) are first melted to give
a homogeneous melt typically having a temperature of 90 to
140.degree. C., and preferably of 95 to 130.degree. C. A phenolic
solution is then admixed. This procedure assures a thorough mixing
and a rapid preparation of the BPA-phenol solution. It likewise
avoids a situation where individual contaminated crystals from the
first crystallization step do not dissolve, causing contamination
of the end product.
[0058] The amount of phenolic solution used in step (g) can
advantageously be adjusted so that the resulting homogeneous
solution preferably has a p,p'-BPA content of 15 to 35 wt-% and
more preferably of 20 to 30 wt-%. The concentration of isomers is
preferably 0.05 to 2 wt-%, more preferably 0.1 to 0.8 wt-%, and
particularly preferably 0.2 to 0.5 wt-%. These concentrations are
based on the solution without taking the water into account.
[0059] The homogeneous solution of BPA in phenol prepared in step
(g) preferably contains 0.1 to 10 wt-% of water and particularly
preferably 0.2 to 3 wt-% of water. If the homogeneous solution were
to contain no water, an increasing amount of acicular crystals
would potentially be obtained in the next step(s) of
crystallization, with the low concentrations of isomers in the
mother liquor, and acicular crystals may lead to various problems
in the production facility, namely, inter alia, accelerated fouling
on cooling surfaces during crystallization, and deterioration of
washing performance in the solid-liquid separation. This may
detract from the product quality. The presence of water produces
sturdy crystals, i.e. shorter and thicker crystals. Moreover, the
presence of water in these concentrations during the
crystallization has the effect of reducing the incorporation of
impurities into the crystals, thereby allowing a further increase
in product purity.
[0060] In another embodiment according to the present invention,
independently of the operating temperatures in the crystallizers,
it is possible to add acetone in concentrations of 0 or 0.1- to 5
wt-%, based on the resulting mixture, as a further degree of
freedom other than the addition of water. This measure makes it
possible, inter alia, to optimize the crystal morphology, the
solid-liquid separation behavior, the fouling tendency and the
behavior of impurities with respect to incorporation into the
adduct crystals, and/or to adjust the concentration of the mother
liquor. A continuous suspension crystallization of a BPA-phenol
adduct from the homogeneous solution obtained in step (g) is then
carried out in step (h). Crystals of bisphenol A-phenol adduct are
obtained in step (h) by continuous suspension crystallization from
the homogeneous solution obtained in step (g), and these crystals
are separated from the liquid phase by solid-liquid separation
(step i), especially filtration, and then washed with a phenolic
solution (step (j)). The cooling in step (h) can be effected
indirectly by means of heat exchangers.
[0061] The crystallization may take place in one or more
crystallizers connected in series if desired. The mean total
residence time of the crystals in this crystallization stage should
preferably be between half an hour and ten hours. With a
correspondingly slow crystallization, the inclusion of mother
liquor and the incorporation of impurities into the crystals of
BPA-phenol adduct may be prevented to the greatest possible extent.
During crystallization, the product mixture may be cooled to 35 to
55.degree. C. in one crystallization step, for example, it being
possible for one or more crystallizers to be operated in parallel.
Alternatively, the crystallization may take place in two or more
steps, the product mixture being cooled to a temperature of 45 to
70.degree. C. in a first step and then to a temperature of 35 to
55.degree. C. in a second step. In both embodiments, the cooling
can be effected using one or more heat exchangers per
crystallizer.
[0062] The details of an alternative embodiment of the two
crystallization stages (b) and (h) are as follows: In the first
crystallization stage (step (b)) the crystallization takes place in
two steps in series, and in the second stage (step (h)) it takes
place in one step in one or more crystallizers operated in
parallel. A step within a crystallization stage is understood as
meaning a crystallization in a specific temperature range. A
crystallization stage carried out in two steps in series is thus
carried out in two different temperature ranges in succession.
Using stepwise crystallization in the first stage achieves a
greater purity. Because of the lower isomer contents present and
the increased fouling tendency associated therewith, a longer
working life of the heat exchangers is achieved by conducting
crystallization in one step for the second stage. In one preferred
embodiment, the temperature of the product mixture is adjusted
upstream of step (h) to a temperature that is at most 5.degree. C.
above the crystallization point.
[0063] The subsequent solid-liquid separation step (i), especially
filtration, and washing in step 0) are carried out e.g. in or on
one of the following types of apparatus: continuous filter
centrifuges such as screen-conveyor centrifuges or pusher
centrifuges, batch filter centrifuges such as skimmer centrifuges,
and/or continuous filters such as rotary or drum filters, belt
filters and disk filters. It is preferable to use rotary filters
and particularly vacuum rotary filters. It is particularly
preferable to use a type of apparatus that can also be employed in
step (c) and (d).
[0064] In the case of filtration by means of a vacuum rotary
filter, the filtration is preferably carried out as described in DE
199 61 521 A, the content of which is incorporated herein by
reference.
[0065] The washing of the solid phase, especially the filter cake,
can be effected with a phenolic solution, which extensively
displaces the mother liquor remaining in the filter cake and frees
the adduct crystals from impurities adhering to the surface. The
solid phase, especially the filter cake, may be washed with a
single phenolic solution or several phenolic solutions, which are
applied successively or as a mixture, e.g. via spray nozzles.
[0066] The phenolic solution used for washing the recrystallized
crystals of BPA-phenol adduct in step (j) may be either fresh
phenol, i.e. commercially available phenol, or recycled phenols
obtained for the production facility, or mixtures of the two. A
recycled phenol is understood as meaning a phenol that is obtained
in the course of the process and recycled into the process. It is
also possible to use phenols obtained in the preparation of
polycarbonate by the melt process. The washing phenol used here
preferably contains in total, a maximum of 1.0 wt-% of other
phenolic components, e.g. isopropenylphenol, BPA and its isomers
and secondary components. Recycled phenols, e.g. from the removal
of phenols from the crystals of BPA-phenol adduct, are purified
here only by distillation, if at all. The temperature of the
washing phenol is advantageously 41 to 75.degree. C. and preferably
45 to 60.degree. C. The washing phenol may contain up to 10 wt-% of
water.
[0067] The adduct crystals obtained in step (j) in the form of a
solid phase moistened with phenol, especially a filter cake
moistened with phenol, preferably have a BPA purity of at least
99.8 wt-%, based on the sum of BPA and secondary components. The
residual moisture in the filter cake as a proportion by weight of
the liquid adhering to the crystals of BPA-phenol adduct, based on
the total weight of moist filter cake, is advantageously below 40
wt-% and preferably from 15 to 30 wt-%. Preferably, the amount of
phenolic solution for washing the filtered crystals of bisphenol
A-phenol adduct is chosen so that the amount of washing liquid
corresponds to 20 to 120 wt-% of the amount of filtered crystals of
BPA-phenol adduct. The amount used is particularly preferably 50 to
90 wt-%.
[0068] The liquid phase from (i) and (j), especially the filtrate,
from the solid-liquid separation of the second crystallization
stage, (i), can be used in step (g) for mixing with the molten
filter cake from (d), and in step (c) for washing the filter cake
and/or for rinsing purposes (e.g. washing the cloth), optionally
after the addition of water and/or acetone. Preferably 10 to 50
wt-% and particularly preferably 20 to 40 wt-% of the liquid phase
obtained in step (i) and/or (O) is recycled into step (d) for
washing purposes. Also, preferably 50 to 90 wt-% and particularly
preferably 60 to 80 wt-% of the filtrates obtained in step (i)
and/or 0) are used in step (g).
[0069] In one preferred embodiment, all or part of the mother
liquor obtained in step (i) and of the washing and dehumidifying
filtrates (j) may be collected separately. The filtrates from
washing and dehumidifying, which are less contaminated with
isomers, are preferably passed to step (g), while part of the
mother liquor is preferably passed to step (d). Due to increased
discharge of isomers, the filtrate a concentration level drops in
the second crystallization stage, thereby improving the product
purity. Dehumidifying filtrates are understood to be those
filtrates which are removed from the filter cake as residual
washing liquids on applying a vacuum of 5 to 500 mbar.
[0070] Another possible way of lowering the isomer concentration in
the second crystallization stage, (h), and thereby increasing the
resulting product purity involves evaporating 0 or 0.1 to 35 wt-%,
preferably 0 or 0.1 to 10 wt-%, of the filtrates obtained in step
(i) and/or (j), passing the bisphenol A and isomer-free top
product, consisting essentially of phenol, water and optionally
acetone, to step (g) and/or step (j), optionally after further
purification, and recycling the bottom product, enriched in
bisphenol A and isomers, upstream of step (b). This measure affords
better control over the phenol balance of the production facility
and hence improves operability.
[0071] An alternative embodiment of the process comprises the
preparation of BPA in two categories of purity, namely a BPA with a
purity of 99.5 to 99.75 wt-% and a high-purity BPA with a purity of
at least 99.8 wt-%, in the same production facility. In this case,
both a one-stage and a two-stage crystallization, as well as the
subsequent product work-up (solid-liquid separation, washing,
dissolution, and removal of phenol), are carried out separately for
the different BPA purities. However, the mother liquors from the
first crystallization stage and first solid-liquid separation stage
may be processed together and recycled into the reaction. In this
case, the product mixture formed in the reaction is subjected to
separate crystallization and product work-up for the different BPA
purities.
[0072] In step (k) phenol from the solid phase obtained in step
(j), especially the filter cake, is removed from BPA-phenol adducts
by thermal separation at temperatures of at least 120.degree. C.
Preferably, the phenol is completely or partially removed by
distillative and/or desorptive methods such as those described e.g.
in DE 198 48 026 A, DE 198 60 144 A and DE 199 61 566 A, the
contents of which are incorporated herein by reference.
[0073] The process according to the invention makes it possible to
prepare bisphenol A with a purity of at least 99.8 wt-% of p,p-BPA,
a low color index and a high temperature stability.
[0074] After the phenol has been separated off to levels preferably
of max. 600 ppm and particularly preferably of max. 100 ppm in step
(k), a bisphenol A melt is obtained which may be used, optionally
without prior solidification, for the preparation of polycarbonate
by the transesterification process (melt polycarbonate). However,
the bisphenol A melt may also be solidified by known processes such
as the prilling process, and/or by exfoliation, for sale or further
utilization. Furthermore, the melt may be dissolved in a sodium
hydroxide solution and used for the preparation of polycarbonate by
a phase boundary method or other method.
[0075] This gives a polycarbonate with a low yellowness index (YI)
of max. 1.5 as a measure of the color.
[0076] In another embodiment of the present invention, the melt is
evaporated in step (k) to residual phenol contents of 2 to 20 wt-%,
as described in DE 199 54 787 A incorporated herein by reference,
and this melt, without prior solidification, is reacted with
diphenyl carbonate by the melt process to give polycarbonate. This
again yields a polycarbonate with a low YI (max 1.5).
[0077] The liquid phase obtained from the solid-liquid separation
in step (c) and (d) (mother and washing liquor) contains phenol,
BPA, water and optionally acetone and co-catalyst, and is enriched
in the secondary components typically obtained in the preparation
of BPA. The water is preferably separated from the liquid phase
obtained in step (c) and (d) (mother and washing liquor) to
residual contents of max. 0.3 wt-%, preferably of 0.25 wt-%, and at
least 90 wt-% of the resulting solution is advantageously recycled
into the reaction in step (a), with the optional addition of
acetone, phenol and co-catalyst.
[0078] With an increasing concentration level of water and/or
optionally acetone in the second crystallization stage, (h), it may
be advantageous to carry out a thermal separation of water and/or
acetone from the phenolic solution transferred from step (i) and
(j) to step (d), and optionally to recycle the resulting distillate
into the second crystallization step (in or upstream of step (h)),
especially if the concentration of these compounds in the second
crystallization stage becomes so high that a separate evaporation
or distillation of the solutions transferred from step (i) and 0)
to step (d), as a rough separation, offers economic advantages
compared with the separation of water in the main circuit. After
work-up of the material stream between step (c) and (d) and step
(a) in order to remove water, a partial stream of preferably 0.5 to
10 wt-%, or so-called discharge, is taken off. This partial stream
is withdrawn from the process chain as so-called BPA resin,
optionally after the recovery of phenol, isopropenylphenol,
bisphenol A or other components and optionally after prior
treatment with acid(s) and/or base(s).
[0079] By way of example, the discharge may advantageously be
subjected first to rearrangement on an acidic ion exchanger, then
to concentration by partial distillation of the phenol, and then to
crystallization and filtration. The distillate obtained may be used
to wash the filter cake and rinse the cloth. The crop of crystals
containing BPA may be recycled into the first crystallization
stage, (b), and the isomer-enriched mother liquor may be worked up
further, preferably by distillation, to recover more phenol.
EXAMPLES
Example 1 a)
Embodiment
[0080] A product mixture obtained in step (a), containing 70.1 wt-%
of phenol, 22.0 wt-% of BPA, 6.6 wt-% of isomers, 1.1 wt-% of water
and 0.2 wt-% of acetone, was introduced continuously into a
crystallizer for the purpose of suspension crystallization in step
(b) (1st crystallization stage). The mean residence time in the
crystallizer was 1 h and the mixture was circulated through an
external heat exchanger. The temperature of the crystallizer was
thus adjusted to 41.degree. C. The crop of crystals found under
steady-state conditions had the phenol-free composition shown in
Table 1, row 1. A sturdily acicular crystal habit was found.
[0081] The crystals of BPA-phenol adduct filtered off step (c) and
washed in step (d) were melted and mixed with a phenolic solution
in step (g) to form a homogeneous solution containing 77 wt-% of
phenol, 22 wt-% of BPA and 1 wt-% of isomers, as shown in Table 1,
row 2.
[0082] This homogeneous solution shown in Table 1, row 2 was mixed
with water in a ratio of 99:1 and crystallized under the conditions
described (residence time 1 h, external heat exchanger, temperature
41.degree. C.) (2nd crystallization stage, step (h)). The crystals
of BPA-phenol adduct found under steady-state conditions after
filtration (i) and washing in step (j) had the phenol-free
composition shown in Table 1, row 4. A sturdy, slightly acicular
crystal habit was found.
Example 1 b)
Comparative Example
[0083] A product mixture obtained analogously to step (a),
containing 70.1 wt-% of phenol, 22.0 wt-% of BPA, 6.6 wt-% of
isomers, 1.1 wt-% of water and 0.2 wt-% of acetone, was introduced
continuously into a crystallizer for the purpose of suspension
crystallization (1st crystallization stage). The mean residence
time in the crystallizer was 1 h and the mixture was circulated
through an external heat exchanger. The temperature of the
crystallizer was thus adjusted to 41.degree. C. The crop of
crystals found under steady-stage conditions had the phenol-free
composition shown in Table 1, row 1. A clear acicular crystal habit
was found.
[0084] The filtered and washed crystals of BPA-phenol adduct were
melted and mixed with a phenolic solution to form a homogeneous
solution containing 77 wt-% of phenol, 22 wt-% of BPA and 1 wt-% of
isomers, as shown in Table 1, row 2.
[0085] This homogeneous solution was crystallized under the
conditions described above (residence time 1 h, external heat
exchanger, temperature 41.degree. C.) in a suspension
crystallization without the presence of water (2nd crystallization
stage). The crystals of BPA-phenol adduct found under steady-state
conditions after filtration and washing had the phenol-free
composition shown in Table 1, row 3. A distinctly acicular crystal
habit was found. The product purity was lower than in Example 1 a)
according to the invention. TABLE-US-00001 TABLE 1 Purity of the
crystals of BPA-phenol adduct without taking the phenol into
account, and composition of the recrystallization feed p,p-BPA
Isomers Phenol [wt-%] [wt-%] [wt-%] 1. crystallized once 99.29 0.71
2. recrystallization feed 77 22 1 3. recrystallized 99.84 0.16
(Comparative Example 1 b)) 4. recrystallized, addition of 99.88
0.12 water (Embodiment 1 a))
Example 2
[0086] A phenolic solution containing 4 wt-% of acetone, max. 0.1
wt-% of water, 9 wt-% of p,p'-BPA and isomers was reacted in step
(a) at a rate of 50 t/h in the presence of an ion exchange resin in
sulfonic acid form and mercaptopropionic acid as co-catalyst. The
reaction product contained about 24 wt-% of p,p'-B PA.
[0087] After the addition of a partial stream enriched in p,p'-BPA
from steps (c) and (d) and (i) and (j), BPA-phenol adduct was
crystallized continuously from the resulting mixture in a first
crystallization stage, (b), in two steps at 54.degree. C. and
41.degree. C. with a total residence time of 8 h, the suspension
being cooled and the heat of crystallization dissipated by means of
heat exchangers.
[0088] The solid-liquid separation of the suspension in step (c)
was carried out on a vacuum rotary filter, the resulting filter
cake as well being washed with a phenolic solution at about
55.degree. C. in step (d).
[0089] The filter cake was first melted and then mixed with a
phenolic solution to give a homogeneous solution in step (g). The
solution prepared in this way contained 25 wt-% of p,p'-BPA and 0.3
wt-% of isomers. Water was added before crystallization to give a
water content of 1 wt-% in the homogeneous solution. The
temperature of the solution was adjusted to 79.degree. C.
[0090] The repeat crystallization in step (h) was carried out
continuously in two steps at 54.degree. C. and 41.degree. C., the
suspension being cooled and the heat of crystallization dissipated
by means of heat exchangers in each case. The residence time in
this crystallization stage (h) was 4 h.
[0091] In step (i) the suspension was filtered on a vacuum rotary
filter and washed (j) at about 55.degree. C. with a phenolic
solution containing max. 0.1 wt-% of isomers.
[0092] The resulting crystals of BPA-phenol adduct moistened with
phenol, having a residual moisture content of about 25 wt-%, were
then melted and the phenol was removed by thermal separation in
step (k) to a content of 90 ppm. After prilling of the BPA melt,
the BPA obtained had a purity of at least 99.9% and a color index
of less than 20 Hazen units.
[0093] The mother liquor from steps (c) and (d) and (i) and (j) was
extensively dewatered. A partial stream was taken from the
dewatered mother liquor and subjected to distillation of the part
of the phenol. The distillate was used to wash the filter cake and
rinse the cloth. After further separation by means of
crystallization and filtration, a BPA-containing stream from the
BPA-enriched bottom product was recycled into the first
crystallization stage, (b), and the isomer-enriched mother liquor
was worked up further to recover phenol.
Example 3
Simulation of a Two-Stage Crystallization Process
[0094] A simulation study of a two-stage crystallization process
for the preparation of high-purity bisphenol A is described below.
The simulations were performed using the commercial software
package Aspen Custom Modeler.RTM.. The software is based on a
process model with special models for the reaction (detailed
reaction kinetics), for the kinetics of the incorporation of
impurities in the crystallization, and for other basic
operations.
[0095] Step (a): Reaction of acetone and phenol to give p,p'-BPA
and isomers, with the formation of water, in adiabatic fixed bed
reactors in the presence of a co-catalyst under the following
inflow conditions: [0096] 4 wt-% of acetone, 0.07 wt-% of water, 9
wt-% of p,p'-BPA; temperature: 52.degree. C. [0097] Step (b): The
reaction products, containing 22.5 wt-% of p,p'-BPA, were passed to
the first crystallization stage, where BPA-phenol adduct was
crystallized in two steps at 54.degree. C. and 41.degree. C. with a
total residence time of 5 h. The calculated purity of the crystals
was 99.68 wt-%, based on bisphenol A. [0098] Step (c): The
suspension was filtered through a vacuum rotary filter, [0099] Step
(d): washed and dehumidified on the same vacuum rotary filter. The
filter cake was washed using a partial stream of 27% of the
filtrates from step (i) and (j), corresponding to a ratio of amount
of washing liquid to amount of resulting solid of 0.9.
[0100] The phenolic mother liquor discharged from the
recrystallization stage contained 9 wt-% of p,p'-BPA, 0.3 wt-% of
isomers and 1.3 wt-% of water. Some of this partial stream was used
together with recycled phenols from the plant to clean the filter
cloth.
[0101] The dehumidified filter cake had a residual moisture content
of 25 wt-%. With the impurities from the mother liquor still
adhering to the crystals, and from the isomer-laden washing liquid,
the purity of the filter cake after leaving the rotary filter was
99.4 wt-%, based on p,p'-BPA. [0102] Step (g): The filter cake from
(d) was melted and mixed with the residual filtrates from (i) and
(j) so that the concentration of p,p'-BPA in the inflow of the
second crystallization stage, (h), was 23 wt-%. The solution formed
also contained 0.3 wt-% of isomers and 1 wt-% of water. [0103] Step
(h): Crystallization in two steps at 54.degree. C./41.degree. C.
with a total residence time of 5.5 h. The calculated purity of the
adduct crystals was 99.93 wt-%, based on p,p'-BPA. [0104] Step (i):
The suspension obtained was filtered [0105] Step (j): washed with
fresh phenol and recycled phenol streams from the plant, and then
dehumidified. Part of these phenol streams used in step 0) for
washing was also used to clean the filter cloth. The amount of
washing liquid used to wash the filter (j) cake was 71 wt-%, based
on the solid obtained. The filtrates obtained from filtration and
washing in step (i) and (j) were combined and recycled into steps
(d) and (g) together with the filter cloth clearing liquor. [0106]
Step (k): The filter cake, with a residual moisture content of 25
wt-%, was melted. The phenol content was reduced by means of
thermal separation to a residual value of 150 ppm in the BPA melt.
The resulting phenol was passed to step (j) The BPA melt obtained
had a purity of 99.92 wt-%, based on p,p'-BPA.
[0107] The mother and washing liquor from step (c) and (d) was
dewatered to a water content of 0.075 wt-%. A partial stream
thereof, corresponding to 4% of the total amount, was taken off in
order to discharge the isomers as BPA resin after downstream
recovery of the phenol. The remaining part of the dewatered mother
liquor was recycled into the reaction in step (a), with the
addition of acetone, phenol and a co-catalyst.
[0108] According to the simulation study, the impurity content of
the product decreased by 12% if the filtrates from filtration and
washing in step (i) and 0) were not combined but separated in such
a way that the mother liquor more heavily laden with isomers
(filtrate from the filtration (i)) was preferably passed to step
(d) and the washing filtrates from (j) were preferably passed to
step (g).
[0109] Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations may
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
[0110] Additional advantages, features and modifications will
readily occur to those skilled in the art. Therefore, the invention
in its broader aspects is not limited to the specific details, and
representative devices, shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
[0111] All documents referred to herein are specifically
incorporated herein by reference in their entireties.
[0112] As used herein and in the following claims, articles such as
"the", "a" and "an" can connote the singular or plural.
* * * * *