CA1328447C

CA1328447C - Catalysts for the preparation of amorphous copolymers of propylene and olefins

Info

Publication number: CA1328447C
Application number: CA000579979A
Authority: CA
Inventors: Horst Kurt Seeger; Richard Kingsley Stuart, Jr.; William Albert Ames
Original assignee: Eastman Kodak Co
Current assignee: Eastman Chemical Co
Priority date: 1987-10-28
Filing date: 1988-10-13
Publication date: 1994-04-12
Anticipated expiration: 2011-04-12
Also published as: WO1989003847A1; KR890701649A

Abstract

ABSTRACT OF THE DISCLOSURE
Disclosed is a catalyst mixture comprising TiCl3, TiCl4, and an aluminum-alkyl cocatalyst.
The catalyst mixture is particularly advantageous for the synthesis of pressure-sensitive amorphous adhesives that are copolymers of propylene and 1-olefin, such as 1-hexene, in a high temperature solution process.

Description

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. -,',',.....
.. ~ .

~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 . ,: , . . .

. .

`. 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 : ":
' ,;~
,, ': ::.

. ~323~7 :,.

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 ..... .

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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Claims

1. A catalyst mixture comprising:

(a) about 5 to about 50 weight percent (based on the weight of (a) plus (b)) of a supported catalyst comprising TiCl4 supported on an inorganic halide salt, (b) about 95 to about 50 weight percent (based on the weight of (a) plus (b)) of a preactivated catalyst comprising preactivated TiCl3, and (c) an aluminum-alkyl cocatalyst at a molar ratio of aluminum-alkyl:
Ti-chloride of about 0.25:1 to about

2:1.

2. The catalyst of Claim 1 wherein said supported catalyst comprises about 1 to about 15 weight percent TiCl4 supported on MgCl2.

3. The catalyst of Claim 1 wherein said preactivated catalyst comprises TiCl3 plus about 10 to 50 weight percent polypropylene.

4. The catalyst of Claim 1 wherein said aluminum-alkyl cocatalyst is selected from the group consisting of triethyl aluminum, tributyl aluminum, and triisobutyl aluminum.

5. The catalyst of Claim 1 wherein said aluminum-alkyl cocatalyst is triethyl aluminum.

6. The catalyst of Claim 1 wherein the amount of supported catalyst is about 15 to about 45 weight percent, the amount of preactivated catalyst is about 85 weight percent to about 55 weight percent, and the molar ratio of aluminum-alkyl:Ti-chloride is about 1:1 to about 1.5:1.

7. The catalyst of Claim 1 wherein the amount of supported catalyst is about 25 weight percent, the amount of preactivated catalyst is about 75 weight percent And the molar ratio of aluminum-alkyl:Ti-chloride is about 1.25:1.

8. The catalyst of Claim 1 wherein the supported catalyst additionally contains up to about 25 weight percent organic esters and ethers.

9. The catalyst of Claim 8 wherein said organic esters and ethers are selected from the group consisting of anisole, ethyl benzoate and methyl benzoate.

10. A process for preparing an amorphous propylene higher 1-olefin copolymer comprising contacting propylene and a higher 1-olefin with a catalyst mixture comprising:

(a) About 5 to about 50 weight percent based on the weight of (a) plus (b)) of a supported catalyst comprising TiCl4 supported on an inorganic halide salt), (b) about 95 to about 50 weight percent (based on the weight of (a) plus (b)) of a preactivated catalyst comprising preactivated TiCl3, and (c) an aluminum-alkyl cocatalyst at a molar ratio of aluminum-alkyl:
Ti-chloride of about 0.25:1 to about 2:1;

said process occurring for a sufficient reaction period and under conditions such that the desired copolymer is formed.

11. The process of Claim 10 wherein said higher 1-olefin is 1-hexene.

12. The process of Claim 10 carried out in an inert atmosphere at a temperature of about 140°C to about 200°C, a pressure of about 400 to about 2000 psig, in the presence of a suitable solvent and for a reaction period of about 1/2 to about 10 hours.

13. The process of Claim 10 curried out in an inert atmosphere at a temperature of about 150°C to about 180°C, a pressure of about 1000 to about 1500 psig in the presence of a suitable solvent, and for a reaction period of about 2 to about 4 hours.

14. The process of Claim 10 wherein said supported catalyst comprises about 1 to about 15 weight percent TiCl4 supported on MgCl2.

15. The process of Claim 10 wherein said preactivated catalyst comprises TiCl3 plus about 50 weight percent polypropylene.

16. The process of Claim 10 wherein said aluminum-alkyl cocatalyst is selected from the group consisting of triethyl aluminum, tributyl aluminum, and triisobutyl aluminum.

17. The process of Claim 10 wherein said aluminum-alkyl cocatalyst is triethyl aluminum.

18. The process of Claim 10 wherein, in the catalyst mixture, the amount of supported catalyst is about 15 to about 45 weight percent, the amount of preactivated catalyst is about 85 to about 55 weight percent, and the molar ratio of aluminum-alkyl:Ti-chloride is about 1:1 to about 1.5:1.

19. The process of Claim 10 wherein, in the catalyst mixture, the amount of supported catalyst is about 25 weight percent, the amount of preactivated catalyst is about 75 weight percent, and the molar ratio of aluminum-alkyl:Ti-chloride is about 1.25:1.

20. The process of Claim 10 wherein the supported catalyst of said catalyst mixture additionally contains up to about 25 weight percent organic esters and ethers.

21. The process of Claim 20 wherein said organic esters and ethers are selected from the group consisting of anisole, ethyl benzoate, and methyl benzoate.

22. A hot-melt, pressure-sensitive adhesive comprising an amorphous propylene-hexene copolymer containing about 40 to about 75 weight percent 1-hexene, having a melt viscosity of about 5,000 to about 50,000 cp at 190°C, a softening point of about 90°C
to about 125°C, a probe tack of at least about 500 grams, a quick stick of at least about 1.5 pounds per inch, a 180° peel adhesion of at least about 2.5 pounds per inch, and a static shear adhesion of at least about 10 hours.

23. The adhesive of Claim 22 containing about 55 to about 65 weight percent 1-hexene and wherein the melt viscosity is about 15,000 to about 25,000 cp at 190°C, and the softening point is about 95°C to about 120°C.