Note: Descriptions are shown in the official language in which they were submitted.
4~L
This invention relates to synthetic hydrocarbon-
derived resins and to their preparation. This
invention especially relates to tacki.fying resins
suitable for use in admixture with 1,3 butadiene/styrene
copolymers derived .~rom a manipulative combination of
diolefins~ olefins and a-methyl styrene.
Valuable reslns can be preparecL by polymerizing a
diolefin/olefin mixture characterized by a principal
backbbne of piperylene and 2-methyl-2-butene. Such
resins, when polymerized with aluminum chloride, can be
especially valuable for use in adding tack to various
rubbers for adhesive purposes.
However, such resins are substantially i-nadequate
for effectively enhancing the tack of 1,3-butadiene/styrene
aqueous emulsion copolymerized elastomers for many
purposes. Although the mechanism is not thoroughly
understood, such backboned resins, apparently require a
balance of compatability with the butadiene/styrene
copol~mers to achieve ma~imum tack enhancement Simply
increasing the 2-methyl-2-butene, or decreasing the
piperylene~ content of the backbone has been found to be
insufficiently effective.
Therefore, it is an object of this invention-
to provide an improved hydrocarbon-derived resin having
a primary diolefin/olefin backbone for tack enhancement
of 1,3-butadiene/styrene emulsion copol~mer elastomers~
In accordance with this invention, a hydrocarbon-
derived tackifying resin is prepared by the method
which comprises reacting in the presence of an aliphatic
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hydrocarbon solvent and a catalyst selected from
aluminum chloride and ethyl aluminum dichloride~ a
monomer mixture comprised of 60 to about 75 weight
percent of a diolefin/olefin mixture of a weight ratio
in the range of about 0.6/1 to about :L.4/1 and,
correspondingly, about 40 to about 25 weight percent
a-methyl styrene, where said diolefin comprises at least
about 95 weight percent piperylene and up to about 5 weight
percent isoprene based on the diolefin, and where said
olefin comprises at least one olefin selected from
2-methyl-2-butene~ 2-methyl-1-butene, 2-methyl-2-pentene,
and 2-methyl-1-pentene~ preferably at least about 90 weight
percent 2-methyl-2-butene or 2-methyl-2-pentene based on
the olefin. A 650C to 800C softening point is typical.
In the practice of this invention~ it is preferred
that the diolefin is essentially piperylene and that the
olefin is essentially 2-methyl-2-butene.
In further practice of thls invention, in order
to provide effective enhancement of the ta¢k by the
a-methyl styrene, it is required in the resin that, as
the amount of a-methyl styrene increases~ the diolefin/
olefin ratio increases. Thus, for example, as a-methyl
styrene increases from 25 to 40 percent, the diolefin/
olefin ratio should correspondingly increase about 0.6/1
to about 1.~/1. In this regard, it is preferred that
the amount of a-methyl styrene ranges from about 30 to
about 37 weight percent and the diolefin/olefin ratio
correspondingly ranges from about 1.1/1 to about 1.3/1.
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The resins of this invention are prepared b~
reacting the manipulated monomers in the presence of an
aliphatic solvent, and aluminum chloride or ethyl
aluminum dichloride~ at a temperature in the range of
about 0C to about 100C~ pre~erably in the range o~
about 10C to about 50oC. The reaction can be conducted
batch-wise or as a continuous process. The reaction can
be conducted at atm~spheric pressure or above or below
atmospheric pressure. Generally, the autogen~us
pressure developed by the reaction can be used.
Representative of various aliphatic solvents are
saturated hydrocarbons containing 3 to 8 carbon
atoms, representative of which are n-butane, isobutane,
n-pentane, isopentane, n-hexane, isohexane, n-heptane,
and isoheptane Hexane and heptane are preferred. It
; is understood that unreacte~ hydrocarbons in the
polymerization mixture can also act as a solvent.
Generally sufficient solvent is used to provide a
solution containing 70 weight percent monomers or resin,
although higher or lower concentrations can usually be
used.
Generally the reaction can be conducted over a
period o~ time in the range of about 30 to about 120
minutes, although shorter or longer times can be used.
The resin is generally recovered by deactivating
the catalyst with a material selected fro~ water, alcohol
such as methanol, isopropanol and butanol and/or lime,
filtering the product and steam stripping the filtrate
to remove volatiles. Then the resin can be mixed with
~o~
various rubbers, particularly 1,3-butadiene/styrene
aqueous emulsion copolymerized elastomers, as tackifying
enhancers.
The resin of this invention has been found to be
particularly useful for mixing with and enhancing the
tack of elastomers prepared by free radical, a~ueous
emulsion copolymerizing a mixture of 1,3-butadiene and
styrene. Particularly representative of such copolymers
are those containing about 60 to about 95 weight percent
units derived from 1,3-butadiene, and, correspondingly
about 40 to about 5 weight percent units derived from
styrene.
The elastomers can conveniently be prepared by
conventional emulsion copolymerization, followed by
coagulation and drying.
Generally the tackifying resin is mixed with the
elastomer in an amount of about 30 to about 250 weight
percent taokifying resin, based on the mixture of
resin and elastomer. If desired, the mixture can
conveniently be formed by dry mixing the tackifying
resin and elastomer on a mixing mill or banbury or
by mixing ln the presence of a volatile organic
hydroca~bon solvent such as toluene ? benzene, hexane,
heptane and octane.
The practice of this invention is more fully
illustrated by reference to the following example which
is intended to be representative rather than limiting
of the scope of the invention. Unless otherwise indicated~
all parts and percentages are by weight.
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EXAMPLE I
A series o~ experiments were conducted, identi~ied
herein as Experiments A to H and HH. In these
experiments, various amounts of piperylene ~PIP) and
2-methyl-2-butene t2MB2), along with heptane, were
charged to reactors. Additionally, various amounts of
-methyl styrene along with aluminum trichloride were
also charged to the reactors. The polymerization reactions
were conducted at temperatures in the range of about 25C
to about 30C for about 120 minutes. After this time,
the catalyst was neutralized, or deactivated, wlth
methanol and lime. The resin was simply recovered by
filtering the product and steam distilling the filtrate
to remove volatiles.
The results of Experiments A to H7 including tack
analysis with butadiene/styrene rubber using 50parts per
resin per 50 parts free radical, aqueous emulsion-co-
polymerized butadiene/styrene elastomer are more clearly
shown in the following Table 1. Note that the resin
made with similar pip/2MB2 ratios with no a-methyl
styrene impart no effective tack to SBR~ as is more
clearly demonstrated in Experiment HH.
~O~
TABLE l
Resin
Monomer ~o alpha- Softening Tack
Ratio methyl Point 2 (Rolling
~ styrenel (C) Ball)
A 0.8 28 74 1.9
~3 1.2 ~8 79 ~ 25
c o.6 33 69 1.2
D ~l.0 35 . 70 2.1
E l.0 35 72.5 1.4
F l.~ 3~ 78 6.5
G 0.8 ~ 72 1.8
H 1~2 40 76 2.2
HH 1.O 0 99 No tack
1 - Based on the total of piperylene, 2-methyl-2-butene
and a-methyl styrene
2 - Sof~ening point of resin according to ASTM E 28-58 T.
It should be pointed out that the polymerization
mixture did contaln some few additional hydrocarbons,
in addition to the basic piperylene/2-methyl-2-butene/
a-methy~ styrene, as is more clearly shown in Table 2.
TABLE 2
(Piperylene/2-methyl-2-butene ratio = 1.3)
~ Percent (bY wei~ht)
t-2-pentene 9.78
c-2-pentene 12.00
2-methyl-2-butene 20~16
isoprene .8
cyclopentene 3.~6
1-t-3-pentadiene 20.51
l-c-3-pentadiene 5.82
a-methyl styrene 26.00
other Cs's and C6's 1.~3
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Experiments I-P are presented in Table 3 to
more clearly show the effect of varying the amount o~
a-methyl styrene for specific piperylene/2-methyl-
2-butene ratios. The resin/rubber mi~tures were
prepared as for Table 1. These experiments generally
indicate that~ as the amount of a-methyl styrene is
increased, the enhancement of tack for butadiene/styrene
type, free radical, aqueous emulsion copolymerized~ rubber
is substantially enhanced.
TA~LE 3
Tack
Monomer % (Rollin~
Ratio a-methyl Ball)
PIP/2MB2 sty~ene inches
I 1.~ 33 ~ 13
J 1.~ 26 8.73
K l.L~ 38 6.28
L 1.4 ~0 ~.08
M 1.3 31 ~13
N 1.3 33 8.63
0 1.3 36 5.68
P 1.3 38 3.75
It is a particular advantage of this invention
that the resin is required to be prepared in the presence
of an aliphatic solvent, preferably selected from
hexane or heptane, to the substantial or essential
exclusion of aromati~ hydrocarbons. Not only is such
a solvent required for the preparation of the advantageous
resin of this invention~ but this requirement uniquely
obviates the requirement of aromatic hydrocarbon recovery
systems in commercial applications. Indeed, this
.a
particular polymerization diluent or solvent advantage
is of sufficient magnitude that ik should be considered
as an enhancing feature of the invention.
So long as the basic piperylene/said ole~in
backbone is maintained, the polymerization monomer
mixture can be modified by containing up to about 15
weight percent, preferabiy only up to about 10 weight
percent, piperylene dimers, piperylene trimers or
other unsaturated hydrocarbons containing 5 to 6 carbon
atoms. Representatlvè of such hydrocarbons, which may
take place in the polymerlzatlon reaction, include
those, in addition to the 2-methyl-2-butene, selected
from 2-methyl-1-butene, 2~3-dimethyl l-butene~
2~3-dimethyl-2-butene~ 2-methyl-1-pentene~ 2-methyl-2-
pentene, cyclopentene and 1,3-cyclopentadiene. It is
understood that o~her hydrocarbons containing 4 to 6,
more generally 5 to 6, carbon atoms can be present
which act more as diluents than reactants. Representative
of typical hydrocarbons which have been found to be
present are 3,3-dimethyl-1-butene~ l-pentene, 2-pentene,
3-methyl-2-pentene, 4-meth~l-1-pentene, 2-hexene and
cyclohexene.
While certain representative embodiments and
details have been shown for the purpose of illustrating
the invention, it will be apparent to those having
skill in this art that various changes and modifications
may be made therein without departing from the spirit
or scope of the invention.
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