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Description  |
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FIELD OF THE INVENTION
This invention relates to anionic polymerization of monomers and to
functionalized polymers used as components in adhesives, sealants and
coatings.
BACKGROUND OF THE INVENTION
Anionic polymerization of conjugated dienes with lithium initiators, such
as sec-butyllithium, and hydrogenation of residual unsaturation has been
described in many references including U.S. Pat. No. Re. 27,145. The
capping of living anionic polymers to form functional end groups is
described in U.S. Pat. Nos. 4,417,029, 4,518,753, and 4,753,991. Of
particular interest for the present invention are anionic polymers that
are capped on one or more ends with hydroxyl, carboxyl, phenol, epoxy, and
amine groups.
Anionic polymerization using protected functional initiators having the
structure R.sup.1 R.sup.2 R.sup.3 Si--O--A'--Li is described in WO
91/12277 wherein R.sup.1, R.sup.2, and R.sup.3 are preferably alkyl,
alkoxy, aryl, or alkaryl groups having from 1 to 10 carbon atoms, and A'
is preferably a branched or straight chain bridging group having at least
2 carbon atoms. The bridging group is most preferably straight chain alkyl
having from 3 to 10 carbon atoms and is exemplified by the following
compound:
##STR1##
which is readily prepared by lithiation of the reaction product of
1-chloro-6-hydroxy-n-hexane and t-butyldimethylchlorosilane.
Monofunctional and telechelic polymers produced by anionic polymerization
of dienes and vinyl aromatic monomers typically have narrow molecular
weight distributions in comparison to the broad molecular weight
distributions usually achieved by polymerization of these monomers by
non-anionic mechanisms such as free radical, cationic, Ziegler-Natta, etc.
Number average molecular weights are preferred for the comparison of most
functionally terminated polymers because they are reacted in
stoichiometric amounts with crosslinking and chain extension agents such
as poly- and di-functional isocyanates. The absence of very high molecular
weight components in polymers produced by anionic polymerization results
in low viscosities for a given number average molecular weight. Low
viscosities are desirable in functionally terminated polymers for
applications such as paints and coatings because they allow formulation
with a minimum amount of solvent and/or elevated temperature to reach
application viscosities.
Amorphous, low glass transition temperature polymers such as polydienes are
advantageous for coatings applications because of their low viscosities.
Hydrogenated dienes are particularly advantaged for applications that
require good weatherability and hydrolytic stability. Hydrogenated
isoprene is advantaged over hydrogenated polybutadiene because it does not
crystallize and is, therefore, transparent. Hydrogenated isoprene polymers
have lower viscosities than high 1,4-addition hydrogenated polybutadiene
diols such as POLYTAIL H made by Mitsubishi which is a solid at room
temperature. Although low 1,4-addition polybutadienes such as G-2000 made
by Nisso or Polytail-HA made by Mitsubishi are transparent, they have high
glass transition temperatures and high viscosities.
It is also desirable to avoid the presence of molecules with more than two
functional groups to avoid crosslinking in applications such as
thermoplastic polyurethanes and modification of polycarbonates and
polyesters. Anionic polymerization using a protected functional initiator
followed by end capping assures that no molecules have functionality
greater than two, unlike radical polymerizations which have broad
distributions of functionality.
Telechelic hydrogenated isoprene polymers having number average molecular
weights from 2,500 to 5,500 are commercially available from Atochem under
the name EPOL and Kuraray, TH-21 and TH-1, but all known commercial
products have polydispersities (M.sub.w /M.sub.n or Q) greater than 2,
viscosities higher than 500 poise at 25.degree. C., and average
functionalities greater than 2.0. It is an object of the present invention
to provide improved monofunctional and telechelic unsaturated and
hydrogenated isoprene polymers having low viscosity.
SUMMARY OF THE INVENTION
The present invention includes the discovery that monofunctional and
telechelic unsaturated and hydrogenated isoprene polymers having number
average molecular weights from 1,000 to 15,000 have surprisingly lower
viscosities than previously available monofunctional and telechelic
isoprene polymers when the polymers have greater than 80% 1,4-addition and
a polydispersity less than 2.
DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates the surprising reduction in viscosity for unsaturated
isoprene diols of the present invention in comparison to similar polymers
having different microstructure.
FIG. 2 illustrates the surprising reduction in viscosity for hydrogenated
isoprene diols of the present invention in comparison to previously
available hydrogenated isoprene diols.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises linear unsaturated or hydrogenated isoprene
polymers having number average molecular weights from 1,000 to 20,000,
greater than 80% 1,4-addition of the isoprene, a polydispersity less than
2, and from about one to two terminal functional groups per molecule.
Preferably, the isoprene polymers have number average molecular weights
from 1,000 to 9,000, greater than 90% 1,4-addition of the isoprene, a
polydispersity less than 1.5, and hydrogenation of at least 90% of the
polymerized isoprene. The polymers are prepared by anionic polymerization
in the absence of microstructure modifiers that increase 3,4-addition of
the isoprene.
The anionic polymerization of unsaturated monomers with initiators such as
s-butyllithium is well known. The use of functionalized initiators having
the structure
R.sup.1 R.sup.2 R.sup.3 Si--O--A'--Li
is described in WO 91/12277 wherein R.sup.1, R.sup.2, and R.sup.3 are
preferably alkyl, alkoxy, aryl, or alkaryl groups having from 1 to 10
carbon atoms, and A' is preferably a branched or straight chain bridging
group having at least 2 carbon atoms, preferably linear alkyls having from
3 to 10 carbon atoms. The use of such an initiator to polymerize the
desired monomer(s), followed by capping to produce the second terminal
functional group, has several advantages over difunctional initiators such
as 1,4 dilithiobutane and lithium naphthalide. In addition to providing
the option of polymerizing in non-polar solvents, this route avoids the
formation of ionic gels, which are known to occur when diinitiated
polymers are capped with reagents such as ethylene oxide, generating the
polymeric di-alkoxide. These gels form even in relatively polar solvent
mixtures and greatly complicate subsequent processing steps. By capping to
produce the alkoxide on only one polymer terminus, these gels are avoided.
The isoprene polymers of the present invention have surprisingly lower
viscosities than previously available linear isoprene polymers having from
about one to two terminal functional groups per molecule as shown in FIGS.
1 and 2 which are described in more detail below.
Functionalized lithium initiators having the structure:
##STR2##
wherein each R is methyl ethyl, n-propyl, or n-butyl and A" is an
alkyl-substituted or non-substituted propyl bridging group, including
--CH.sub.2 --CH.sub.2 --CH.sub.2 -- (1,3-propyl), --CH.sub.2
--CH(CH.sub.3)--CH.sub.2 -- (2-methyl-1,3-propyl) and --CH.sub.2
--C(CH.sub.3).sub.2 --CH.sub.2 -- (2,2-dimethyl-1,3-propyl), or an
alkyl-substituted or non-substituted octyl bridging group such as
--CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2
--CH.sub.2 --CH.sub.2 -- (1,8-octyl) initiate polymerization of
unsaturated monomers at surprisingly higher polymerization temperatures
with surprisingly lower amounts of dead initiator (higher efficiency) than
similar initiators wherein A" is replaced by alkyl-substituted or
non-substituted butyl, pentyl, or hexyl bridging groups, such as
--CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 -- (1,4-butyl), --CH.sub.2
--CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 -- (1,5-pentyl), or --CH.sub.2
--CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 -- (1,6-hexyl). For
the purpose of this description, the number of carbon atoms in the
bridging group refers to the carbons spanning the oxygen and lithium; i.e.
alkyl branches on the bridging alkyl carbons, such as the methyl groups on
the 2,2-dimethyl-1,3-propylene segment, are not counted.
In Structure (2), each R is preferably methyl and any alkyl branching on A"
is preferably methyl. Substituents other than alkyl groups may be useful
for R and as branching on A", however the effect on initiation efficiency
and polymerization temperature would have to be determined by experiments.
The preferred initiators of Structure (2) are similar to s-butyllithium
with regard to operating temperature although initiation of isoprene with
Structure (2) results in higher amounts of dead initiator than initiation
with s-butyllithium. However the initiators of the invention have the
advantage of placing a silyl ether group at the start of the polymer chain
which serves as a "masked" or "protected" alcohol, capable of conversion
to a primary alcohol group after polymerization is completed, as described
in WO 91/12277. The polymer chains may be terminated, endcapped, or
coupled by conventional means to end the polymerization and provide one or
more terminal functional groups on linear isoprene polymers having high
1,4-addition of the isoprene.
The living polymers can be terminated by reaction with methanol, reacted
with a capping agent such as ethylene oxide, or dimerized by treatment
with a coupling agent such as dibromomethane. In the present invention,
the linear polymers have an initial terminal silyl ether group prior to
termination, capping, or coupling of the polymer. Cleavage of the silyl
ether leaves a primary alcohol group in this position.
The preferred initiators of Structure (2) are very active at room
temperature and polymerization is preferably initiated at a temperature
from 20.degree. C. to 60.degree. C., most preferably from 20.degree. C. to
40.degree. C. It is generally advisable to keep the polymerization
temperature below about 100.degree. C.; above this temperature, side
reactions that change microstructure and limit capping efficiency may
become important. Polymerizations can be carried out over a range of
solids, from about 5% to about 40%. For high solids polymerizations, it is
preferable to add the monomer in increments to avoid exceeding the desired
polymerization temperature. If the initiator is to be added to the full
monomer charge, it is preferable to run the polymerization between 10% and
20% solids.
Anionic polymerization is often terminated by addition of water to remove
the lithium as lithium hydroxide (LiOH) or by addition of an alcohol (ROH)
to remove the lithium as a lithium alkoxide (LiOR). Polymers prepared from
initiators of the present invention and terminated in this way will be
mono-hydroxy functional (mono-ols) after removal of the silyl protecting
group. To prepare polymers having an additional terminal functional
groups, the living polymer chains are preferably terminated with hydroxyl,
carboxyl, phenol, epoxy, or amine groups by reaction with ethylene oxide,
oxetane, 2,2-dimethyloxetane, carbon dioxide, a protected hydroxystyrene
monomer, ethylene oxide plus epichlorohydrin, or the amine compounds
listed in U.S Pat. No. 4,791,174, respectively. For the preparation of
telechelic diols, the preferred process is to terminate with 1-10
equivalents, most preferably 1-2 equivalents, of ethylene oxide at
30.degree. C.-50.degree. C. This reaction is quite rapid; reaction times
from 5 to 30 minutes yield acceptable results.
The termination step can result in release of fine particles of lithium
bases as described in U.S. Pat. No. 5,166,277 which is incorporated by
reference herein. The lithium bases may interfere with hydrogenation of
the polymer and preferably are removed, especially if the hydrogenation is
to be carried out at high solids.
Termination with carbon dioxide results in carboxylate salt groups that
reduce hydrogenation catalyst activity as described in U.S. Pat. No.
4,970,254 which disclosure is incorporated by reference herein. Improved
hydrogenation is obtained by converting the carboxylate salt groups to
ester groups prior to hydrogenation and then reconverting to carboxylate
salt or carboxylic acid groups after hydrogenation.
Hydrogenation of at least 90%, most preferably at least 95%, of the
unsaturation in low molecular weight isoprene polymers is achieved with
nickel catalysts as described in U.S. Pat. No. Re. 27,145 and U.S. Pat.
No. 4,970,254 and U.S. patent application Ser. No. 07/785,715, now U.S.
Pat. No. 5,166,277, which are incorporated by reference herein. The
preferred nickel catalyst is a mixture of nickel 2-ethylhexanoate and
triethylaluminum described in more detail in the examples. Large amounts
of catalyst are needed to hydrogenate polyisoprene having low 3,4 addition
and it is preferable to extract the nickel catalyst after hydrogenation by
stirring the polymer solution with aqueous phosphoric acid (20-30 percent
by weight), at a volume ratio of 0.5 parts aqueous acid to 1 part polymer
solution, at about 50.degree. C. for 30-60 minutes while sparging with a
mixture of oxygen in nitrogen. This step is also described in more detail
in the examples.
Saturated or unsaturated conjugated diene polymers having from about one to
two terminal functional group selected from hydroxyl, carboxyl, phenol,
epoxy, and amine groups can be used without solvents when the viscosity of
the polymer is less than about 500 poise at mixing and application
temperature. Linear unsaturated isoprene polymers having two terminal
hydroxyl groups per molecule and lower viscosity than 500 poise at mixing
and application temperatures are produced by limiting the number average
molecular weight to a range from about 1,000 to 20,000 and by limiting the
3,4-addition of hydrogenated isoprene to an amount below 20%, preferably
below 10%. Linear hydrogenated isoprene polymers having two terminal
hydroxyl groups per molecule and lower viscosity than 500 poise at mixing
and application temperatures are produced by limiting the number average
molecular weight to a range from about 1,000 to 9,000 and by limiting the
3,4-addition of hydrogenated isoprene to an amount below 20%, preferably
below 10%.
After polymerization and, optionally, hydrogenation and washing of the
polymer, any silyl group at the front of the polymer chain may be retained
to provide a monofunctional polymer with a protected hydroxyl group that
may be reactive during final application. Optionally, the silyl group at
the front of the chain can be removed to generate the desired primary
hydroxyl functional group. This step is often referred to as deprotection.
A variety of processes for removal of the silyl protecting group are
known; for a review, see T. W. Greene, "Protective Groups in Organic
Synthesis", J. Wiley and Sons, New York, 1981, incorporated herein by
reference. A preferable process would involve easily handled, relatively
low toxicity, and inexpensive reagents. In a preferred process, the silyl
group is removed by reaction of the polymer solution with 1-5 equivalents
(basis silyl end groups) of a strong organic acid, preferably
methanesulfonic acid (MSA), in the presence of 0.1% to 2% by weight of
water and 5% to 20% by volume of isopropanol (IPA) at about 50.degree. C.
Essentially complete conversion to the alcohol was observed for polymers
produced using initiators that lacked .beta. branching, such as Structure
(2) having a 1,3-propylene bridging group, in 30 minutes to 3 hours.
Polymers produced from Structure (2) having a 2,2-dimethyl-1,3-propylene
bridging group (possesses two methyl groups .beta. to the silanol)
required reaction times on the order of 24 hours to achieve comparable
conversion under these conditions. Polymers prepared from an initiator of
Structure (2) with a 2-methyl-1,3-propylene bridging group (possesses one
methyl group .beta. to the silanol) would should be intermediate in with
respect to ease of deprotection.
Sufficient IPA must be present during deprotection to prevent the formation
of a discrete aqueous phase. Excess acid is then removed by washing with
dilute aqueous base, preferably 0.1N-0.5N sodium hydroxide or potassium
carbonate, followed by water.
For some applications, such as coatings prepared by baked cures of the
polymer with amino resins in the presence of a strong organic acid
catalyst, it may be preferable to use the polymer in its "protected" form.
The viscosity of the protected polymer is lower and conditions such as
those described above should accomplish the deprotection (generate the
alcohol) during the cure.
The conjugated diene polymers produced as described above have the
conventional utilities for terminally functionalized polymers of such as
forming adhesives, coatings, and sealants and in polymer modification.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The most preferred products are linear isoprene homopolymers having number
average molecular weights from 1,500 to 4,500, greater than 90%
1,4-addition of the isoprene, hydrogenation of at least 95% of the
polymerized isoprene, and from 1.6 to 2.0 terminal hydroxyl groups per
molecule.
The dihydroxylated polymers are preferably produced by initiation with a
lithium initiator having Structure (2) wherein A" is a non-substituted
alkyl bridging group having 3 or 8 alkyl carbons. Most preferably the
lithium initiator has the structure
##STR3##
which is produced by silylation of 3-chloro-1-propanol, followed by
reaction with lithium metal. After polymerization of the desired amount of
isoprene, the living polymer is capped with ethylene oxide and reacted
with methanol to give a terminal primary alcohol group. The silyl group is
then converted to a hydroxyl group by reaction with MSA in the presence of
water and IPA.
The preferred polymers of the present invention are useful in adhesives
(including pressure sensitive adhesives, contact adhesives, laminating
adhesives and assembly adhesives), sealants (such as urethane
architectural sealants, etc.), coatings (such as topcoats for automotive,
epoxy primers for metal, polyester coil coatings, alkyd maintenance
coatings, etc.), films (such as those requiring heat and solvent
resistance), molded and extruded thermoplastic and thermoset parts (for
example thermoplastic injection molded polyurethane rollers or reaction
injection molded thermoset auto bumper, facie, etc.), fibers (such as
thermoplastic urethanes and polyamides) and polymer modification (for
polyesters and polycarbonates).
A composition of the instant invention may contain plasticizers, such as
rubber extending plasticizers, or compounding oils or organic or inorganic
pigments and dyes. Rubber compounding oils are well-known in the art and
include both high saturates content oils and high aromatics content oils.
Preferred plasticizers are highly saturated oils, e.g. Tufflo.RTM. 6056
and 6204 oil made by Arco and process oils, e.g. Shellflex.RTM. 371 oil
made by Shell. The amounts of rubber compounding oil employed in the
invention composition can vary from 0 to about 500 phr, preferably between
about 0 to about 100 phr, and most preferably between about 0 and about 60
phr.
Optional components of the present invention are stabilizers which inhibit
or retard heat degradation, oxidation, skin formation and color formation.
Stabilizers are typically added to the commercially available compounds in
order to protect the polymers against heat degradation and oxidation
during the preparation, use and high temperature storage of the
composition.
Various types of fillers and pigments can be included in the coating or
sealant formulation. This is especially true for exterior coatings or
sealants in which fillers are added not only to create the desired appeal
but also to improve the performance of the coatings or sealant such as its
weatherability. A wide variety of fillers can be used. Suitable fillers
include calcium carbonate, clays, talcs, silica, zinc oxide, titanium
dioxide and the like. The amount of filler usually is in the range of 0 to
about 65% w based on the solvent free portion of the formulation depending
on the type of filler used and the application for which the coating or
sealant is intended. An especially preferred filler is titanium dioxide.
The dihydroxylated conjugated diene polymers of the present invention may
also be blended with other polymers to improve their impact strength
and/or flexibility. Such polymers are generally condensation polymers
including polyamides, polyurethanes, vinyl alcohol polymers, vinyl ester
polymers, polysulfones, polycarbonates and polyesters, including those,
like polylactones, which have a recurring ester linkage in the molecule,
and those, like polyalkylene arylates, including polyalkylene
terephthalates, having a structure formed by polycondensation of a
dicarboxylic acid with a glycol. The blends may be made in the reactor or
in a post compounding step.
The present invention is further described by the following examples which
include the best mode for making a dihydroxylated, saturated isoprene
homopolymer (EP Diol). The examples are not intended to limit the present
invention to specific embodiments although each example may support the
patentability of a specific claim.
INITIATOR SYNTHESIS
A functionalized initiator was prepared in dry cyclohexane by reaction of
3-chloro-1-propanol with t-butyldimethylsilyl chloride (TBDMS-C1) in the
presence of imidazole, followed by reaction with lithium metal, as
described in WO 91 112277. The concentration of active lithium alkyl was
determined by titration with diphenylacetic acid, as described by W. G.
Korfron and L. M. Baclawski (J. Org. Chem, 41(10), 1879 (1976)) .
EXAMPLE 1
A linear isoprene polymer and its hydrogenated analogue having about two
terminal hydroxyl groups per molecule, a number average molecular weight
of 4,350, a 1,4-addition of isoprene of 95.8%, and a residual unsaturation
of 0.47 meq/g (96% hydrogenated) is prepared as described below: 450 g.
(6.6 moles) of isoprene and 4050 g. of cyclohexane were charged into a 2
gal. stainless steel autoclave. The reactor was heated to 30.degree. C.
and 172 g. of a 11.7% wt. solution of protected functional initiator
described above in cyclohexane (0.112 moles) was added. After about 9
minutes, the reaction temperature was increase to about 60.degree. C. and
polymerization was allowed to continue for about 40 minutes. After 40
minutes, the reactor was cooled to about 40.degree. C. and 20 g. (4
equivalents) of ethylene oxide was added. After 30 minutes, 16 g. (1.1
equivalents) of 2-ethylhexanol was added. GPC analysis indicated a number
average molecular weight of 4,350 amu. and a polydispersity (Q, the ratio
of weight to number average molecular weights) of 1.14. The number average
molecular weights were measured using gel permeation chromatography (GPC)
calibrated with polyisoprene standards having known peak molecular
weights. The solvent for the GPC analyses was tetrahydrofuran.
An aliquot of the solution was vacuum dried to remove the solvent. 80 g. of
the resulting polymer were added to a two liter extraction flask
containing 720 ml of cyclohexane. A solution containing 1.0 g. of water
and 6.5 g. of anhydrous methanesulfonic acid in 138 g. of isopropanol was
then added. The resulting slightly hazy solution was stirred for 2 hours
at about 50.degree. C. The sample was washed with one aliquot of 1N
aqueous potassium carbonate and two aliquots of DI water (about 750 ml
each). 200 g. of isopropanol was added to aid in separation of the organic
and aqueous phases. The pH of the aqueous phase after the fourth water
wash was about 7. The polymer solvent was removed in a rotary evaporator,
leaving a slightly yellow, clear liquid.
A 780 g. aliquot of the above polymer cement (15% solids in cyclohexane)
was charged into a 4 liter high-pressure stainless steel autoclave,
diluted to 7.5% solids by the addition of 780 g. of cyclohexane. The
solution was heated to 40.degree. C. and sparged with hydrogen for 30
minutes. The catalyst is prepared in advance by reacting nickel
2-ethylhexanoate with triethylaluminum in cyclohexane in amounts
sufficient to give a ratio of 2.5 moles of aluminum to 1 mole of nickel.
After sparging the reactor is then filled with hydrogen to a pressure of
700 psig. An initial aliquot of the Ni/Al catalyst solution, sufficient to
bring the nickel concentration in solution to 400 ppm., is then pressured
into the reactor. The reaction temperature is ramped to 75.degree. C. over
30 minutes and held at this temperature for 2.5 hours with constant
agitation. Total reaction time is 3 hours. Ozone titration indicated 96%
hydrogenation of the butadiene unsaturation (final R.U.=0.47 meq/g).
The catalyst residues were extracted by contacting the resulting solution
with 1.5% phosphoric acid in water at a volume ratio of 2 parts aqueous
acid to one part polymer solution in a 3 l. resin kettle. After sparging
the kettle with a mixture of oxygen and nitrogen, the solution was stirred
for 20 minutes then allowed to settle. An emulsion formed after the first
wash; isopropanol was added (25% by weight of the polymer solution) to
break the emulsion. The aqueous acid layer was removed and the wash was
repeated this time without the formation of an emulsion. The aqueous layer
was removed.
A solution containing 1.0 g. of water and 4.45 g. of anhydrous
methanesulfonic acid in 100 g. of isopropanol was then added to the washed
polymer cement (523 g. at 7% solids). An additional 393 ml of cyclohexane
and 162 gms of isopropanol were added. The resulting slightly hazy
solution was stirred for 3 hours at about 60.degree. C. The solution was
washed without heating with 2 liters of 1N aqueous sodium hydroxide and
two aliquots of DI water (about 2 liters each); the pH of the aqueous
phase after the third water wash was about 7. The polymer solvent was
removed in a rotary evaporator, leaving a colorless, slightly hazy liquid.
The 1,4-addition of polyisoprenes was measured by .sup.13 C NMR in
chloroform solution. The functionality of the polymers was analyzed by
High Performance Liquid Chromatography (HPLC) to determine the relative
amounts of the desired dihydroxy material (diol), mono-hydroxy material
(either capped with EO but not deprotected or deprotected but terminated
by protic impurities) and non-functional material (protected--no EO
incorporated). The HPLC separation was accomplished with a 250
mm.times.4.6 mm 5 micron DIOL phase column using a stepped
heptane/tetrahydrofuran gradient. An evaporative light scattering detector
is used to quantify the sample.
EXAMPLES 2 AND 3
The procedure of Example 1 was repeated twice using different ratios of
initiator to monomer as follows:
______________________________________
% % OH/ Viscosity
Example
Mn Q 1,4 RU Molecule
Poise at 25.degree. C.
______________________________________
1 4,350 1.14 95.8 0.47 1.99 812
2 3,110 1.14 95.5 0.43 1.96 414
3 1,780 1.11 94.6 0.056
1.99 159
______________________________________
EXAMPLES 4, 5, 6 AND 7
Linear isoprene mono-ols having about one hydroxyl group per molecule were
synthesized using s-butyllithium as the initiator in the absence of
microstructure modifiers followed by capping with ethylene oxide.
Neutralization of the polymeric alkoxide afforded the desired isoprene
mono-ol.
In a dry box, under an inert nitrogen atmosphere, the initiator, s-BuLi
(15.7 g of a 9.1% (wt/wt) solution of s-BuLi in cyclohexane, 0.025 mol)
was dissolved in 400 g of polymerization grade cyclohexane. Isoprene
monomer (98.8 g) was added to the initiator solution; the monomer addition
was in aliquots of 20-30 g with sufficient time allowed between increments
to keep the temperature of the polymerizing mixture below 50.degree. C.
When the polymerization of isoprene was complete, the living
monolithiopolymer was capped by reaction with an excess of ethylene oxide
(EO); EO was bubbled through the mixture until the yellow color of the
living polymer dissipated. The alkoxide end groups were neutralized by
addition on an excess of methanol (2 g). The polymer product was isolated
from this solution by washing the lithium methoxide from the polymer with
distilled water and the polymer was concentrated under vacuum with a
rotary evaporator apparatus.
Analysis of the polymer product by GPC found the number average molecular
weight to be 3,110; and a Q of 1.15. An NMR analysis technique found the
1,4-addition of isoprene to be 88% for this polymer and the functionality
to be 0.81.
EXAMPLES 5, 6, AND 7
Using the procedure of Example 4 described above and the amounts of
reagents noted below, three additional isoprene mono-ols were prepared
having different molecular weight values as follows:
______________________________________
Example .sub.- s-BuLi
Cyclohexane Isoprene
MeOH
Number (mol) (g) (g) (g)
______________________________________
4 0.025 400 98.8 2
5 0.05 405 99.7 1
6 0.01 400 99.8 1
7 0.003 800 50 0.1
______________________________________
The analysis of these samples by GPC and NMR afforded the following data:
______________________________________
Viscosity
Sample 1,4- Content
Functionality
poise,
Number Mn Q by NMR by NMR 25.degree. C.
______________________________________
4 3,110 1.15 88% 0.81 34
5 1,340 1.55 83% 0.85 12
6 8,830 1.04 92% 0.88 150
7 9,670 1.02 94% 0.90 190
______________________________________
The low polydispersity, high 1,4-addition polyisoprene mono-ols of Examples
4-7 have much lower viscosities than either radical or other anionic
isoprene mono-ols prepared by addition of microstructure modifiers.
COMPARATIVE EXAMPLE 1
For comparison with standard anionic polymerization techniques, linear
isoprene diols were synthesized using a diinitiator followed by capping
both ends with ethylene oxide. Neutralization of the polymeric dialkoxide
afforded the desired isoprene diol. The diinitiator had been prepared by
reaction of s-BuLi with diisopropenylbenzene (DIPB).
In a dry box, under an inert nitrogen atmosphere, DIPB (15.8 g, 0.1 mol)
was dissolved in a diethyl ether (248 g)/cyclohexane (423 g) solvent
mixture. Two equivalents of s-BuLi (141 g of a 9.1% (wt/wt) solution of
s-BuLi in cyclohexane, 0.2 mol) were added per equivalent of DIPB in the
original mixture to afford a deep red colored solution of the desired
diinitiator. About 15 minutes after the addition of the s-BuLi reagent,
isoprene monomer (151 g) was added to the diinitiator solution; the
monomer addition was in aliquots of 30-40 g with sufficient time allowed
between increments to keep the temperature of the polymerizing mixture
below 50.degree. C. When the polymerization of isoprene was complete, the
living dilithiopolymer was capped by reaction with an excess of ethylene
oxide (EO); EO was bubbled through the mixture until the yellow color of
the living polymer dissipated. Addition of EO caused the solution to gel
as the polymeric dialkoxide was formed. The alkoxide end groups were
neutralized by addition on an excess of methanol (6.4 g). As the polymer
alkoxide end groups were neutralized, the gel broke up affording a free
flowing solution of the desired isoprene diol. The polymer product was
isolated from this solution by removal of the lithium methoxide
precipitate by filtration and concentration of the polymer under vacuum
with a rotary evaporator apparatus.
Analysis of the polymer product by GPC found the number average molecular
weight to be 1,300; and a Q of 1.62. An NMR analysis technique found the
1,4-addition of isoprene to be 38% for this polymer and the functionality
to be 1.58.
COMPARATIVE EXAMPLES 2, 3, AND 4
Using the procedure of Comparative Example 1 described above and the
amounts of reagents noted below, three additional isoprene diols were
prepared having different molecular weight values as follows:
______________________________________
Cyclo- Isopr-
Sample DIPB .sub.- s-BuLi
hexane
Diethyl
ene MeOH
Number (mol) (mol) (g) Ether (g)
(g) (g)
______________________________________
C2 0.076 0.15 580 45 304 4.8
C3 0.04 0.08 576 64 300 2.6
C4 0.025 0.05 360 40 100 4.0
______________________________________
The analysis of these samples by GPC and NMR afforded the following data:
______________________________________
Sample 1,4- Content
Functionality
Number Mn Q by NMR by NMR
______________________________________
C2 2,410 1.77 60% 1.94
C3 5,470 1.43 57% 1.98
C4 3,800 1.36 54% 1.86
______________________________________
The low polydispersity, high 1,4-addition hydrogenated polyisoprene diols
of Examples 1-3 have much lower viscosities than either radical or other
anionic (e.g. initiated by DiLi or Li naphthalene in THF) hydrogenated
isoprene diols as shown in FIG. 2. The corresponding unsaturated isoprenes
follow the same trend as shown in FIG. 1. The data in FIGS. 1 and 2 show
that the mono-ol that contains the silyl protected hydroxyl is
surprisingly lower in viscosity than the diol after deprotection.
The hydrogenated polyisoprene diols of the present invention are
significantly and surprisingly lower in viscosity than Nisso's
hydrogenated polybutadiene diol (Polytail HA) as shown in FIG. 2.
For comparison, the data shown in FIGS. 1 and 2 is included in the
following Table:
______________________________________
Vis-
cosity
Func-
Poise,
tion-
# Polymer Type MW 25.degree. C.
ality
______________________________________
1 EP PFI Diol 4,350
812 1.99
2 EP " 3,110
414 1.96
3 EP " 1,780
159 1.99
ATOCHEM EPOL Radical 2.25
EP Diol 2,500
1,200
KURARAY TH-21 EP Diol 2,600
1,430 2.6
(KENSEIKA)
TH-11 EP Diol 5,500
9,000 2.2
NISSO POLYTAIL Anionic 1,900
1,650 >1.6
HA EB Diol
NISSO
Mitsubishi
GI-2000 1,900
1,605 >1.6
1 Isoprene PFI Diol 4,350
65.3 1.96
2 3,110
49.4 1.95
3 1,780
28.7 1.91
C1 Isoprene Di-init. 1,300
178 1.58
C2 Anionic 2,410
376 1.94
C3 Diol 5,470
1680 1.98
C4 3,800
887 1.86
______________________________________
The hydrogenated isoprene diol made by the present invention has
significantly lower viscosity than commercial hydrogenated isoprene diols
and is advantaged over hydrogenated butadiene diols both in viscosity for
high 1,2 addition butadiene polymers and in viscosity and clarity for low
1,2 addition butadiene polymers. The polyisoprene diol of the present
invention has lower viscosity than the corresponding diol made by
diinitiation.
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