Note: Descriptions are shown in the official language in which they were submitted.
y
CA 02254110 2005-06-29
PURIFICATION OF GLYCIDYL ESTERS
BY THIN FILM EVAPORATION
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a process for the distillation of glycidyl
esters to provide products having reduced color and improved color stability,
and to the products so produced.
Description of Related Art
Glycidyl esters of monocarboxylic acids are well known materials
which are useful as chemical intermediates in the preparation of acrylic,
polyester, and alkyd resins, or as reactive diluents in the preparation of
thermoset epoxy, polyester and urethane paints and coatings.
Of particular interest are glycidyl esters of aliphatic monocarboxylic
acids represented by the empirical formula
R~ ~ . R~t ~5 R8
R3._~_..~0-.,.~~C~~~ R8
~1) R2 R7 ~~
-1-
CA 02254110 2004-10-05
wherein RI, R2 and R3 each represent the same or different alkyl radicals of
normal
or branched structure containing 1-20 carbon atoms, and R4 through R8 each
represent hydrogen or a hydrocarbyl group containing 1-3 carbon atoms. A more
preferred product is one where Rl through R3 are alkyl radicals containing a
sum '
total of 3-20 carbon atoms and where R4 through R8 are each hydrogen, e.g.,
the
reaction product of neodecanoic acid (RI + R2 + R3 = Cg) and epichlorohydrin.
Glycidyl esters of this general type and their method of preparation are
disclosed in US-A-3075999, 3178454, 3275583 and 3397176.
Such glycidyl esters can be made by reacting an alkali salt of the carboxylic
acid with a halo-substituted monoepoxide such as an epihalohydrin, e.g.,
epichlorohydrin (I-20 molar excess). The mixture is heated (50°-
150°C) in the
presence of a catalyst forming glycidyl ester plus alkali salt and water. The
water
and excess epihalohydrin are removed by azeotropic distillation, and the salt
by-
product, e.g., NaCI, is removed by filtration andlor washing. The glycidyl
esters can
also be made by reacting the carboxylic acid directly with epichlorohydrin
under
similar process conditions. The chlorohydrin ester intermediate formed during
this
reaction is subsequently treated with an alkaline material, e.g., sodium or
potassium
hydroxide, which yields the desired glycidyl ester. By-product salt is removed
by
washing and/or filtration, and water is removed by drying.
Investigations of these reactions reveal that several heavier by-products are
produced during the reactions to varying degrees, and species which add color
to the
main product are contained within the heavier by-products. The heavier by-
products
include the reaction products of.the glycidyl ester product and/or the
chlorohydrin
ester intermediate with either unreacted epichlorohydrin, unreacted
monocarboxylic
acid or salt and/or water at various stages of the synthesis process in
accordance with
the following overall reaction schemes:
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YdtlNl.~
CA 02254110 1998-11-03
0 DH O
/\
(A.) RCOCH + CH= Ct~CHzC1 ~-~-RCOOCt~CI~iCH2C! -~-RCQQCI-i~ CHCH2
(8)
co~ott~'~ds ~ B andlor C with tht g~ycidyl ester product gad other spades
pre~t.
y & one ar a combi~oa of i3~r or other cd heerviGS are
preset in the g~yeidyl ester readian graduct at levels is vc~s of about 3
wP/e, e.g.,
about 4-I2 wt~3'o.
Bcxa»se giycidyl eaters ,ya try aad che~caity rmaiecuies,
separauan of ttsesse by-prodzz~ from. gtycidyi estea is not ~ ~~p~~
Standard a~wspheric d~la~u techniques bsve bees found to iacreaae tire amvuni
of
~Y-Pas meB .aa the deg~ec of color of the esters It is believed that this
iruxt~e
in coEoc is causa~d by the rat elevaoed tes~er.~es, as eaca~.~i~ag
disrilLatiar~ of the giyadyl ~acdcaality prrsent in the desired product with
hm.~ana~ia gr~ in the by groducrs, they ~a~g arid by products.
IS Surpraiagly, star~ard vacuum disaIlazian has also been fnzu~d to be
ineffe~ve in
-3-
__ ~,,~E~DED SKEET
r it~.~;i.~_~;bf:~. ~,s~ r,~t,~ _ . ...__~.~.iL..L~~'~a:.rcia~_._~~~._~
52~:~~~ '.J.~~'~~~-9f _.~~._._._._. .~~.>~~.~fIJN:I.'1W-4~1'.-3~'vc)1._~y
~tC ~VIIS' ~-g ~ g~p ~Q,n ~7G~ilCIS C~
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WO 97/44335 PCT/US97/08927
reducing the initial or aged color of the glycidyl esters, and tends to worsen
the color
problem.
Japanese Patent 46 (1971) 37326 discloses a process for manufacturing an
S unsaturated organic acid glycidyl ester by reacting a salt of the
unsaturated acid
(acrylic or methacrylic acid) with a molar excess of epichlorohydrin. The
residual
unreacted epichlorohydrin is then distilled out of the reaction product using
thin film
distillation techniques. The resulting product is further distilled using thin
film
evaporation techniques to provide a purer product having improved color
stability
after periods of storage. The reference teaches that the process avoids the
polymerization of the acrylic monomers observed during conventional
distillation
and thereby eliminates the need to include a polymerization inhibitor in the
reaction
product which inhibitor retards polymerization of the unsaturated monomers but
which also reacts with the epoxy compounds to give products of less purity.
SUMMARY OF THR INVENTION
The present invention provides a process for the distillation of the glycidyl
ester reaction product composition of one or more straight or branched chain
saturated monocarboxylic acids or salts thereof and a halo-substituted
monoepoxide
comprising subjecting said reaction product composition to conditions of
temperature and vacuum in a thin film, short pass distillation apparatus, and
recovering a light fraction having a Pt-Co color value of less than about 100
after 20
days storage in contact with air at about 125°C, as measured by ASTM
D1209.
Products produced according to the invention are of significantly reduced
initial color and exhibit improved color stability after periods of storage,
thereby
minimizing any color contribution by these products in systems where they are
used,
e.g., in the preparation of alkyd, polyester or acrylic resins and especially
in coating
and paint formulations containing these products.
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DETAILED DESCRIPTION OF THE INVENTION
Glycidyl ester products which are distilled in accordance with this invention
are of
the general structure set forth in formula 1 in the Background section of this
disclosure, and which are the reaction product of one or. a mixture of
saturated
monocarboxylic acids, preferably the alkali or tertiary ammonium salts
thereof, and
a halo-substituted monoepoxide.
Suitable saturated monocarboxylic acids which may be used to prepare the
glycidyl esters are tertiary alkyl acids wherein R1, R2, and R3 in formula 1
above
each contain 1-20 carbon atoms, more preferably 1-12 carbon atoms. More
preferably, the sum total of R', R2, and R3 is 3 to 20, more preferably 3 to
15
carbon atoms and most preferably about 8 carbon atoms. Suitable such acids
include neodecanoic, neotridecanoic, and pivalic acids. A particularly
preferred
acid is a neodecanoic acid prepared by the reaction of mono olefins averaging
8
to 10 carbon atoms in the molecule with carbon monoxide and water.
Suitable halo-substituted monoepoxides which may be used to prepare the
glycidyl esters include epichlorohydrin, 1-chloro-2,3-epoxyhexane, I-chloro-2,
3-
epoxy-4-butyloctane, 1-chloro-2,3-epoxy heptane, 3-chloro-4,5-epoxydodecane, 3-
chloro-4,5 epoxynonane,1-chloro-2,3-epoxy-4-cyclohexyloctane and like
materials.
Glycidyl esters of this type and their method of synthesis are well known in
the art and are particularly described in the aforementioned US-A-3178454 and
3075999.
A thin film, short pass distillation evaporator is used to separate the main
glycidyl ester reaction product from by-products of the A, B and/or C type as
described in the Background section of this disclosure, as well as other
"heavies"
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WO 97/44335 PCT/US97/08927
which may be present as impurities in the glycidyl ester reaction product. The
term
"heavies" as used herein means compounds or mixtures of compounds having a
molecular weight higher than the target glycidyl esters. The use of such
evaporators
allows for rapid vacuum stripping of the glycidyl ester from the mixed
reaction
product without subjecting the product to excessively high temperatures or for
periods of time sufficient to cause thermal degradation of the product and the
further
development of one or more of the heavier by-products which tend to cause
coloration of the product. Typical such evaporators include shell and tube
evaporators, falling or rising film evaporators and wiped film evaporators. A
preferred evaporator for use in the present invention is a wiped film
evaporator.
The wiped film evaporators (also referred to as agitated thin-film
evaporators) preferred for use in the distillation process of the present
invention are
known in the art and are available commercially. A general discussion of the
principle of operation of these evaporators may be found in the publication:
"Agitated Thin-Film Evaporators: A Three Part Report", Parts 1 to 3; A.B.
Mutzenburg, N. Parker and R. Fischer; Chemical Engineering, Sep. 13, 1965.
Typically, wiped film evaporators comprise a cylindrical evaporating vessel.
The vessel may be either vertical or horizontal, with vertically arranged
vessels
being preferred. 'The evaporator further comprises a rotor mounted within the
cylindrical evaporating vessel and provided with a number of wiper blades, and
a
motor is provided to drive the rotor. The rotor is arranged within the
cylindrical
evaporating vessel so that, upon rotation by the motor, the wiper blades are
caused
to move over the inner surface of the cylindrical vessel. The wiper blades may
contact the inner surface of the cylindrical vessel or, alternatively, a small
gap or
clearance may be left between the tips of the wiper blades and the inner
surface of
the cylindrical vessel.
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WO 97/44335 PCT/US97/08927
In operation, the mixture to be separated is fed, supplied or subjected to the
evaporator and forms a thin film over the inner surface of the cylindrical
vessel. The
film is heated, typically by means of indirect heat exchange with a heating
medium
through the wall of the cylindrical vessel, such as steam. The action of the
wiper
blades in passing over the surface is to agitate the film of the glycidyl
ester
composition which forms on the inner cylinder surface, resulting in turbulence
in the
film, which in turn improves heat and mass transfer. In addition, the wiper
blades
insure an even distribution of the composition over the inner surface of the
vessel
and prevent channeling of the liquid as it passes across the surface. Under
the action
of the wiper blades and the heating, the lighter components of the mixture are
caused
to evaporate.
The light product is removed from the evaporator as a vapor and is
subsequently condensed. Condensing is conveniently effected by indirect heat
exchange with a cooling medium such as water. The condenser may be separate
from the evaporator vessel or may be located within the vessel. In the latter
case, the
vessel will comprise a first evaporating section in which the rotor and wiper
blades
are arranged and a second condensing section in which the condenser is housed.
If
desired, a separating section may be disposed between the evaporating section
and
the condensing section to allow removal of any liquid droplets entrained in
the vapor
prior to condensing.
The heavy product is removed from the evaporator as a liquid flowing from
the inner surface of the cylindrical vessel. The wiped film evaporator is
operated
under a vacuum. Suitable pumps for the generation and maintenance of the
vacuum
are well known in the art. Typical examples of suitable pumps include steam
ejector
pumps and diffusion vacuum pumps.
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According to the process of the present invention, the mixture to be
separated is first heated to a temperature sufficient to reduce the viscosity
of the
mixture, thereby allowing it to more readily flow. The mixture is then
introduced
into the evaporator to form a thin film on the inner surface of the heat
exchanger
surface of the evaporator vessel, e.g., a cylindrical drum or a series of
tubes. The
operating pressures for the thin film evaporator will vary according to the
precise
nature of the ester feedstock. Typical operating pressures are in the range of
about
0.05 to about 50 mm Hg, more preferably from about 0.5 to about S mm Hg.
Typical operating temperatures in the evaporator will be in the range of from
about
100°C to about 200°C, more preferably from about 115°C to
175°C. The average
residence time of the glycidyl ester reaction product composition in the
evaporator is
relatively low as compared with that of a conventional batch distillation
apparatus,
and this is believed to be a key factor in the avoidance of discoloration of
the
distillate. Typical average residence time is in the range of from about 0.2
to about
10 minutes, more preferably less than about 2 minutes, depending upon the
nature of
the feedstock and the design of evaporator being employed. It is important,
however, that the operating temperature is not so high as to lead to a
substantial
degree of thermal degradation of the mixture being processed at the particular
residence time and that the operating conditions of temperature and pressure
are
selected to ensure that such high temperatures are not required.
Suitable wiped film evaporators which may be used in accordance with this
invention include apparati of the type disclosed in US-A-3878029, 4160692 or
4173246.
Preferred glycidyl esters purified in accordance with this invention will
generally exhibit boiling points in the range of from about 110-125°C
at 8mm Hg
and a content of by-products such as A, B and/or C described in the Background
section of this disclosure of less than 4 wt%, more preferably less than 2 wt%
and
most preferably less than 0.5 wt%. Coloration of the distilled product is in
many
_g_
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WO 97/44335 PCT/US97/08927
cases reduced at least 50%, more preferably at least 60%, compared with the
product
coloration prior to distillation, as measured using the Pt-Co scale in
accordance with
ASTM test method D 1209. Glycidyl esters purified in accordance with this
invention generally exhibit initial Pt-Co color values of less than 40 units
prior to
S heat storage, more preferably in the range of S-30 Pt-Co units, and values
of less
than about 100 Pt-Co units after 20 days storage in air at about 125°C,
or values of
less than about 50 Pt-Co units after 20 days storage under an inert gas such
as
nitrogen at about 125°C. These products also exhibit an at least about
3% reduction
in epoxy equivalent weight (EEW) as compared with the non-purified starting
material, more preferably a 4 to 8% reduction in EEW.
The following examples are illustrative of the invention.
A commercially available glycidyl ester of neodecanoic acid and
epichlorohydrin marketed by Exxon Chemical Corporation under the tradename
GLYDEXX~ND-101 was provided. This material has an atmospheric boiling point
in the range of about 250°C to 280°C and a content of by-
products "heavies" of
about 10 wt%. Five hundred grams of the starting glycidyl ester was fed
through a
Pope Scientific Model 40450 two inch molecular still (cylinder) equipped with
carbon wiper blades. The still temperature was maintained at 115°C and
the
pressure was 3mm Hg. Flow rate of the ester was maintained at 80-100 g/hr. The
overhead distillate was condensed and collected, yielding a total of 466.1
grams of
overhead and 30.7 grams of non-distilled bottoms. The distillate and starting
material were analyzed by gas chromatography using a Hewlett Packard 5890
instrument equipped with a 1 micrometer DB-1 column. Analysis of the
distillate
showed about a 50% reduction of the heavier ends (heavies) as compared with
the
glycidyl ester prior to distillation as shown in Table 1 and a reduction of
the epoxy
equivalent weight (EEW) from 254 to 241. The latter was measured in accordance
with a modification of ASTM method D 1652B.
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CA 02254110 1998-11-03
- Gva s~~an3a.3 PCTNS97~a8gz7
Z'~hle ~ -C~'e Ch:~m~~.t~llY rialy~i~ I Rtes
P a 4et~mtit,~ ~~~r,- 3teri3lt; ' Z
1 P .
S.a ~ 3-~.~ ~ Zoa z.a~
CiyciuylFster34.T-~4.~ ~ 8829 934
p~ (1)
Heavies f2) 44.U - 56.3 9,6i 4.~
_ .~ ~_~ .._. . . _
.
(1) Includes glycidy-1 neononanoate, giycidyl nc~odecanaace, glycidvi
nndecartoate, Compound C and chlorohydrin ester intermediates peaks
(2) Includes Compounds A and B peaks.
One of the particular advantages afforded by the puri.ficati.on process of
this
Y J invention is a reduction in the ELW of the purified glycidy l ester
product as compared
with the starting product. For exan-~pie, the product of Example i shows about
a 5 a
EEZ'V reduction (from 254 to 241; which is indicatfve of a more highly
purified product.
The theoretically pure product would hare an EEW of about Z~. A lower EE'N~'
means
2 C a higher epoxy concentration in the product wroth leads to greater
efficiency wl~,en
these glycidyl esters are used as resin modifiers or reactive diluents in
other poly-T:~er
systems.
Example 2
Color comparisozts o~ the pre~iistilled and post distilled giycidyl ester
camposition were performed zn accordance with A,STM-D2103. Also, the
resistance to
further discoloration of the giycidyl esters was evaluated in a heat stability
test. Fer this
test, approximately 125 ml samples of gljTcidyl esters were placed in ti.24mL
(8 ounce)
jars. The jars were covered with fail-lined phenolu. caps which were further
secured
with electrical tape. The sealed jars were about one-half full of glyc:dyl
ester and one-
half full of air. ~"nev were placed into a 125~C oven which ~rva~s
continuously purged
with nitrogen. After a few days, the jars were removed from the oven and
allowed to
3 ~ cool about 1 to 2 hours. Colors of the samples were
1~ n;,i~t~DCD SHEET
..,..u,.,_.~ -....,~.o._~.,i..i.__. .~lt...Lc~c~c'~"~~W='~
,~~~~~~~~....~~,'..5'.c. ....~-~3 ~f :'~" dill"~i'~fj~~~,.aW.-
dc~.~~'~,()~\,_~; ....
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WO 97/44335 PCT/US97/0$927
then measured via procedures described in ASTM D1209. This procedure was
repeated with the heat aged samples up to a total heating period of 20 days.
Results
of color comparisons between the non-distilled product and the product
distilled in
accordance with Example 1 are shown in Table 2.
TA~~
DAYS NON- EXAMPLE
HEATED DISTILLED I
color (Pt-Co
Scale)
Initial Samples50 10-15
2 SO-60 1 S
4 50 15-20
50-60 15-20
8 45-50 20
45-50 20
>250 80-90
The results in Table 2 show that the initial color of the GLYDEXX~ product
(50 Pt-Co units) was reduced to 10-I S Pt-Co units after the product was
distilled in
accordance with Example 1. The distilled product also demonstrated remarkable
I 0 color stability after aging in air up to 20 days as compared with the
starting product.
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