Note: Descriptions are shown in the official language in which they were submitted.
132~7
CATALYSTS FOR THE PREPARATION OF
AMORPHOUS COPOLYMERS OF PROPYLENE AND OLEFINS
;~ .
~ield of Invention
This invention relates to ~ novel tit~nium-b~sed
c~t~lyst mixture for the synthesis of pressure-
sensitive adhesiYes that are amorphous copolymers of
propylene ~nd l-olefins in a high temperature
solution process.
Back~round of the Invention ~
Commeric~l cstalysts based on TiC13 or TiCl4 :-
produce either amorphous polyolefins with good
strength and poor t~ck or produce amorphous
l; polyolefins with good tack and poor strength.
Amorphous polyolefins, particularly propylene/hexene
copolymers, sre generally useful ~s
pressure-sensitive adhesives. Pressure-sensitive ~-
adhesives for medic~l tape applic~tions require ~ :
bal~nce of high viscosity, 800d strength and good
tack.
U.S. Patent 3,954,697 discloses sin~le -~
componentl hot-melt, pressure-sensitive adhesives
that ~re propylene copolymers cont~inlng 40 to
60 mole percent hexene and having ~ 130C to 148C
softening point. While the copolymers of this patent
are useful, they are limited in their u~ility to
substrates with ~ higher meltin~ point th~n the `~
copolymer. Applic~tion of ~morphous propylene-hexene
30 copolymers disclosed in this patent to substrates ~ ;
- such ~s polyethylene is difficult without meltin~ the
substrate which results in undesirable holes and
puckers in the substrflte. -
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~32~4~
The am~rphous propylene/hexene copolymers
disclosed in the prior art are made by use of single
catalysts with an aluminum-alkyl cocatalyst. It has
been discovered that a mixture of certain catalysts :~
hereinafter described provide amorphous
propylene-hexene copolymers with an unexpected
balance of properties ideally suited for use RS
pressure-sensitive adhesives for medical tape
applications.
Summarv of the Invention
The present invention is directed to a cat~lyst
mixture comprising: . .
(a) About 5 to a~out 50 weight percen~ (based
on the weight of (a) plus ~b)) of a
supported catalyst comprising TlC14
supported on an inorganic halide sslt,
(b) About 95 to about 50 weight percent (based ~ .
on the weight of (a) plus (b)~ of a ::
preactivated catalyst comprising :
preactivated TiC13, ~nd
(c) An aluminum-alkyl cocstalyst ~t a mol~r ~:
ratio of aluminum-alkyl:Ti-chloride at :~
about 0.25:1 to about 2:1. ;;
~' '" "' -
The present invention is also directed to ~ ..
process for preparing an amorphous propylene/higher
l-olefin copolymer comprising contacting propylene
and a higher 1-olefin with ehe ~bove-described : :
catalyst ~ixture for a sufficient reaction period hnd
under condit~ons such that the desired copolymer is
formed.
~ '.
t 32~7 :-
The present invention is further directed to
copolymer thst is prepsred from the process of the
invention. The copolymer of the present invention is ~ -
a hot-melt, pressure-sensitive adhesive comprlsing an
amorphous propylene~hexene copolymer containing about
40 to about 75 weight percent l-hexene, ssid
copolymer having a melt viscosity of about 5,000 to
about 50,000 centipoises (cp) at l90~C, a softening
point of about 90C to about 125C, a probe tack of -;~
at least about 500 grams, a quick stick of at least
1 5 pounds per inch, and B static shear of at least
~bout 10 hours.
DetAiled Description of the Inven~ion
The teachings of U.S. Patent 3,954,697 link
copolymer composition with its softening point. It ~ ;~
is taught that as the weight percent polymerized ~:
hexene in the copolymer increases, the softening ;;
point decreases. Thus, ~s in most prior art i;~
copolymer systems, the softening point varies with
comonomer concentration in the copolymer in e regular
manner from the value of the ~oftening point of the
homopolymer o$ one monomer to the value of the
homopolymer of the second monomer. In this case the
softenin~ point of the amorphous propylene-hexene
copolymer ranges from the value for polyhexene (80C)
to the vslue for polypropylene (151C).
However, it has been surpr~singly discovered in
the present invention that at a given hexene ~
30 incorporation level in the copolymer it ls possible ; :
to vary the softening point by ~aking an ~ppropriate
choice of catalyst mixture and cocatalyst.
In the catalyst mixture of the present invention
it is preferred that the weight percent o$ supported
catalyst (a) is about 15 to about 45 (based on the
weight of (a) plus (b)), more preferably about 25;
", .,
- 4 - ~32~7
that the weight percent of preactivated catalyst (b)
is about 85 to about 55 (based on the weight of (a)
plus (b)), more preferably about 75; and that the
molar ratio of aluminum-alkyl:Ti-chloride is about
~ 5 1:1 to about 1.5:1, more preferably about 1.25:1.
! The supported catalyst useful in the present
invention preferably comprises TiCl4 supported on
MgCl2. The amount of TiCl4 on the support is
preferably about 1 to about 15 weight percent; more
I 10 preferably about 1 to about 10 weight percent; and
I most preferably about 10 weight percent. The
supported catalyst can optionally contain up to about
25 weight percent organic esters and ethers. Such
organic esters and ethers are typically present in
commercial supported catalyst preparations and can
include, for example, anisole, ethyl benzoate, methyl -
benzoate, and the like. A commercially available
supported catalyst suitable for use in the present
invention is Lynx (trade-mark) 705, available from
Catalyst Resources, Inc., Houston, Texas.
The preactivated catalyst useful in the present ~ -~
invention is preactivated TiCl3. The TiCl3 used to
prepare the preactivated TiCl3 can be any o~ the
commonly available forms of TiCl3 such as aluminum
reduced and activated TiCl3 (AA-TiCl3), hydrogen -
reduced and activated TiCl3, or chemically reduced ;~
TiCl3. In the case of AA-TiCl3 , the TiCl3 is
complexed with AlCl3. The TiCl3 can be preactivated
by any suitable means known in the catalyst art. It
is preferred to preactivate TiCl3 by prepolymerizing
propylene to about the 10 to 50 percent polypropylene
level to obtain a preactivated catalyst comprising
about 10 to 50 weight percent polypropylene and about
90 to 50 weight percent TiCl3. A preferred weight
ratio of TiCl3 to polypropylene is about 50 to 50. The
,. ._ j :
~ 32~7
_ 5 _
r
preactivated cstalyst prepsred from chemically
reduced TiC13 may also contain traces of other
inorganic substances such as AlC13. A commercislly
available preactivated cstalyst for use in the
present invention is Lynx 900 (prepsred from
chemically reduced TiC13), fivailable from Catslyst
Resources, Inc., Houston, Texas.
The aluminum-alkyl cocatalyst useful in the
present invention complexes with the T~-chloride
10 (i.e., both TiC13 and TiC14). As used herein ~`
"alkyl" refers to C2 to C6 alkyls. Preferred ;~
I aluminum-alkyls are triethyl sluminum, tributyl ;~
¦ aluminum, and triisobutyl ~luminum. The most
¦ preferred catalyst is triethyl aluminum.
¦ 15 Although the preferred process of the present ~-
I invention produces a copolymer of propylenethexene-l, ;
the process is not so limited and is &pplicable for -
production of copolymers of propylene and other
higher l-olefins. H~gher l-olefins suitable for use
20 in the present invention include, for ex~mple, ^ ::
heptene-l, octene-l, nonene-l, decene-l, dodecene-l, ;~
octadecene-l, snd the like. ~
The process of the present invention can be ;
charscterized as a high temperature solution
polymerization process.
Preferred conditlons for the process of the
present invention include ~ temperature at sbout
140C to sbout 200C, and A pressure of about 400 to ;~
about 2000 pounds per square inch ~auge (psig)1 more
preferred is a temperature of from ~bout 150C to
about 180C and a pressure of about 1000 to ~bout
1500 psig. The process preferably takes place under
an inert Htmosphere, such as nitrogen or argon, for a
time sufficient to form the desired product, for
exsmple, sbout 1/2 to about 10 hours, with about 2 to
~32~4~7
about 4 hours being preferred. The process generally
is prefer~bly carried out with agitation, e g.,
stirring.
It is also preferred that a solvent or diluent
is used for the process of the present invention,
particularly as a diluent ~or the catalyst mixture.
Organic solvents which can be used for the addition
of catalyst mixtures and diluent include, for
exsmple, aliphatic alkanes or cycloalkanes such ~s
propsne, pentane, hexane, heptane, cyclohexane, ~nd
the like, or hydrogenated aromatic compounds such as
decahydronaphthalene, or aromatic hydrocarbons such
as ben~ene, toluene, xylene, and ~he liXe. The
nature of the solvent is subject to considerable
1~ variation but should be a liquid form at the reaction
conditions and essentially inert to the react~nts and
reaction products. A petroleum fraction of suitable
boiling range such as mineral spirits (a sulfuric
acid washed paraffinic hydrocsrbon boiling at 180C
to 220C) is a particularly good ~nd preferred
solvent or diluent.
The process of the present invention can be
performed either continuously or batchwise; preferred
is continuously. In a continuous process, Renerally
the catalyst mixture in solvent ~nd monomer mixture
~re fed into a suitable reflctor and polymerizstion is
allowed to occur under polymerization conditions.
Preferably, the catalyst mixture is charged into the
reactor first. After polymerization it is typlc~lly
desired to remove unreacted monomer, deactivate the
catalyst and further purify the copolymer, for
example, by passing through an alumina bed and/or
filtration and subsequent solvent removal.
The propylene/hexene-l copolymer produced by the
process of the present invention has A unique balance
of adhesive properties. The copolymer contains about
. ,: , . . .
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`. 132~4~7
.` -- 7 -
.
' 40 to 75 weight percent hexene-1, preferably 55 to 65 -~
weight percent hexene-1. Hexene content can be
'!.' determined by either C13 nuclear magnetic resonance or
~; by Fourier transfer infrared spectroscopy. The
,j 5copolymer has a melt viscosity of about 5,000 to
"
;, about 50,000 cp at 190C, preferably about 15,000 to
about 25,000 cp at 190C.
The melt viscosity of the polymer can be ;
determined by using a Brookfield Thermosel Viscometer
10 according to the methodology described in American
Society for Testing and Materials (ASTM) Method
D-1824-66.
The softening point of the copolymer of the
present invention is between about 90C and about
15 125C, preferably between about 95C and about 120C.
The softening point can be determined using the Ring
and Ball method described in ASTM Method E-28.
The copolymer of the present invention has a `
probe tack of at least about 500 grams, preferably ~-
between about 500 grams and about 650 grams. Probe
tack can be measured on a Polyken (trade-mark) Probe -~
Tack tester at a dwell time of 2 seconds and a
carrier speed of 2 centimeters (cm)/second (sec).
The copolymer of the present invention has a
quick stick of at least about 1.5 pounds per inch,
preferably about 1.7. Quick stick can be determined
by Pressure-Sensitive Tape Council (PSTC) Procedure
PSTC-5.
The copolymer of the present invention has a
180 peel adhesion of at least about 2.5 pounds per
inch; preferably about 3Ø Peel adhesion can be
determined using Procedure PSTC-1.
The copolymer of the present invention has a -
static shear of at least about 10 hours, preferably
about 15 hours. Static shear can be determined using
: ":
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. ~323~7
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- 8 -
Procedure PSTC-7 with 1 kilogram (kg) weight. The
time taken for coated tape to completely ~ep~rate
from the test panel is reported as the st~tic shear
': vslue.
~: 5 The following exsmples are to illustrate the ~;
invention but should not be interpreted ~s 8 .
limitetion thereon. All percentages ~re by we~ght
unless specified otherwise. For the following
examples, the following general conditions were used:
A 6.7-gallon stirred loop reactor w~s fed
continuously with the monomer mixture and a cstalyst
slurry using mineral spirits 2S diluent. The
polymerization was controlled at a pressure of
1,000 psi and a temperature o~ 150C to 180C
depending on the amorphous propylenelhexene ~APH)
viscosity target. The APH product contsining
unreacted monomers, catalyst, and some solvent was
transferred continuously to a letdown tenk where the
monomers were flashed overhead. The product was then
subjected to a steam/air catalyst deactivRtion
process in the solvent stripper ~nd finally pumped
through ~n alumina bed. The finished product W85 .
characterized by viscosity, ring and b~ll softening
point (RBSP), weight percent hexene by lnfrared, and
~dhesive property determination.
In general the following reaction conditions
were maintained.
Reactor Temp, C 162 ;
Reactor Clycol Jacket Temp, ~C 154
React~r Pressure, ps~g lOOD
Stirrer Speed, 750
Revolutions per Minute (RPM)
Propylene Ch~rge, 3.07
pound (lb)/hour (hr) -~
Hexene Charge, lblhr 6.17
,;.,~;
;.;.,,
. .. ..
,~ _ g _ .
.............................................. ...................... ,
~'! Cat~lyst Charge, grams (g)/hr 1.2
~ Residence Time, hr 3.3
p Polymer Produced, lb/hr 7.5
Table I shows how th~ changes in catalyst,
5 catalyst mole ratio, and reaction conditions affect
the polymer yield, monomer conversions, and the
viscosity, RBSP, and hexene con~ent of the APH
product. Table II shows the effect of ca~alyst and
!~ catalyst mole ratio on the ~dhesive properties of the
10 APH products.
t Examples 1 throu~h 8 (Comparative) ~;
In Examples 1 through 8 the triethyl aluminum
(AlEt3)/Lynx 900 catalyst was evaluated for
15 production of pressure-sensitive APH. The catalyst
mole ratio, temperature, and propylene snd hexene -;
feeds were varied in an effort to produce a 20,000 cp
viscosity APH with a good bal~nce of adhesive
properties. This catalyst at a AlEt3/Ti-halide
20 mole r~tio of 0.5/1 gave the best resul~s considering
polymer yield and APH adhesive properties. Raising
! the catalyst mole ratio from 0.5/1 to 1/1 increases
the polymer yield somewhat but also increases the APH
visocity considersbly at a reactor temperature of
162C. Increasing the re~ctor temperature from 162C
to 171C decreased the viscosity from 42,000 cp to
the desired 20,000 cp but hsd a very detrimental
effect on polymer yield, decreasing it from 5,758 to
1,400 pounds APH per pound of catalyst. APH produced
with AlEt3/ Lynx 900 catalyst at a mole r~tio o~
111 had also very poor quick stick, 0.7 to 0.8 pounds
per inch. Decreasing the AlEt3/Si-halide mole
ratio from 0.5~1 to 0.2511 decreased the APH yield
from about 4,000 to 2,000 pounds per pound and
35 decreased he viscosity frGm 20,000 cp to 8,500 cp. .. ,.
To bring the viscosity up into speci~ication range
` ~32~4~7
...
, ,
'' -- 10 --
,
the reactor temperature had to be lowered from 161C
to 156C and the propylene feed had to be rflii~ed from
3.1 to 3.4 pounds per hour. These changes resulted
i in APH having a viscosity of 15,500 cp and a hexene
,~ 5 content of 59~. The adhesive properties of ~his
product are inferior ~o those of the best APH
produced with the AlEt3/Lynx 900 catalyst at a mole
r~tio of 0.5/l, especially in probe tack and static
shear. Compare Example 4 with Example 8 in Tables I
~nd II.
To meet the specifications of pressurc-sensitive
adhesives for medical tape applications, products
should exhibit a viscosity of about 20,000 cp, a
~ proble t~ck of 650 to 700 grams, a quick stick of l.5
;; 15 to 2.0 pounds per inch, a 180 peel adhesion of 2.5
to 3.0 pounds per inch, snd a static shear ~dhesion
of 15 to 20 hours. In an effort to produce such
product propylene and hexene was copolymerized using
the AlEt31Lynx 900 c~talyst system. The ef~ect of
20 catalyst mole ratio, reactor temper~ture, and product ;
composition on the polymer yield and APH adhesive
propertles was ~tudied. The best APH product for the
medical tflpe application contained 62~ hexene and was
produced at 163C using the AlEt3/Lynx 900 catalyst
¦ 25 at 8 AlEt3/TiC13 mole ratio of 0.5/l. See
1 Example 4.
.: -
Example 9 (Comparative)
APH was produced in a batch polymeriz~ition
30 process using a 2-liter stainless steel stirred ; -
autoclave. The catalyst (0.7 gram) AlEt31Lyn~ 705 ~
ae a AlEt3/TiCl4 mole ratio of 4/l was charged to ;-
a preheated autoclave containing lO0 mL mineral
ispirits, 800 mL hexene, and 500 psi C3H6. The
polymerization was conducted at 140C, a pressure of
400 psi and a reaction time of 180 minutes. The
~ 3 ~ 7
: . ~
,, ,.:,
dischsrged polymer was recovered by vacuum stripping
at 230C for 3 hours. The final product (200 grsms) -~
contflined 51~ hexene, ~nd had a viscosity of 8.125 cp :
and a RBSP of 98C. Its adhesive properties showed
good probe tack (780 grams), good 180 peel adhesion
(3.0 pounds per inch), fair quick stick (1.3 pounds .
per inch) snd-very poor sta~ic shear ~dhesion
(1.1 hours).
10 ExamPles 10 throu~h 18 .
In Examples 10 through 18 ~ mixed catalyst
consisting of Lynx 900 and Lynx 705 was evflluated for
the production of pressure-sensitive APH. The :
catalyst composition, c~talyst mole rstio,
15 temperature, and propylene and hexene feeds were :
varied in an effort to optimize the balance of
~dhesive properties of APH. Best results were
obt~ined with a catalyst consisting of 75~ Lynx 900 ~:
and 25% Lynx 705 cocatalyzed wi~h AlEt3 at ~ :
AlEt3 to Ti-halide mole ratio of 1/1 to 1.2511. ~
APH containing 59~ to 60~ hexane ~nd having the : :
desired viscosity of about 20,000 cp and a RBSP of
118C to 119C showed 8 very good balance of edhesive
properties. See Examples 12 and 15. The APH
products combined good probe t~ck (659 to 693 grams~,
good quick stick (1.5 to 1.7 pounds per lnch), and : ~
good 180 peel sdhesion (2.5 to 2.8 pounds per inch) - :
with good static shear ~dhesion 19 to 22 hours). :~;
They ~lso proved to be nonirritants to the human ...
skin. This combinfltion of properties mRkes them
particul~rly well-suited for medic~l tape
application.
:
k 1 3 2 ~ 4 ~ 7
..... .
- 12 -
ExamPles 19 and 20 (Comparative)
.i In Examples 19 and 20 the AlEt3/M -TiC13
catalyst was evaluated for the production of
pressure-sensi~iv~ APH. This cstalyst system was
tsught for APH synthesis in U.S. Pa~ent 3,954,697.
As can be seen in Table ~I APH varying from 59~ to
64% in hexene content exhibits ~dhesive proper~ies
very much inferior to APH produced with the catalyst ~:
of this invention.
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