CA1050192A - Process for preparing polypropylene compositions having high impact strength at low temperatures - Google Patents
Process for preparing polypropylene compositions having high impact strength at low temperaturesInfo
- Publication number
- CA1050192A CA1050192A CA239,318A CA239318A CA1050192A CA 1050192 A CA1050192 A CA 1050192A CA 239318 A CA239318 A CA 239318A CA 1050192 A CA1050192 A CA 1050192A
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- Canada
- Prior art keywords
- propylene
- ethylene
- slurry
- fed
- polymerization
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-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
- C08F297/06—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the coordination type
- C08F297/08—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the coordination type polymerising mono-olefins
- C08F297/083—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the coordination type polymerising mono-olefins the monomers being ethylene or propylene
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- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Graft Or Block Polymers (AREA)
- Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Polymerisation Methods In General (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
There is disclosed a new and improved process for preparing compositions consisting for at least 50% by weight of isotactic polypropylene and having high impact strength at low temperatures. A specific improvement of the process consists in avoiding difficulties caused by the formation of considerable amounts of rubbery polymer in the polymerization product. The process comprises two steps. In step (1) propylene is polymerized in an inert liquid hydrocarbon medium and in contact with a stereospecific catalyst prepared by mixing a titanium trihalide with a dialkyl aluminum monohalide to obtain a slurry. In step (2) ethylene, or an ethylene/propylene mixture, is fed to the polymerization slurry of step (1) and the poly-merization is continued until the amount of ethylene polymerized is, at most, 20% by weight of the total, final polymeric composition obtained.
There is disclosed a new and improved process for preparing compositions consisting for at least 50% by weight of isotactic polypropylene and having high impact strength at low temperatures. A specific improvement of the process consists in avoiding difficulties caused by the formation of considerable amounts of rubbery polymer in the polymerization product. The process comprises two steps. In step (1) propylene is polymerized in an inert liquid hydrocarbon medium and in contact with a stereospecific catalyst prepared by mixing a titanium trihalide with a dialkyl aluminum monohalide to obtain a slurry. In step (2) ethylene, or an ethylene/propylene mixture, is fed to the polymerization slurry of step (1) and the poly-merization is continued until the amount of ethylene polymerized is, at most, 20% by weight of the total, final polymeric composition obtained.
Description
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~j BACKGROU~D OF THE I~VE~TIO~
Isotactic polypropylene, as defined in ~atta et al SP 3,112,300, is a polypropylene which consists essentially of isotactic macromolecules, i.e., macromolecules having substantiall the isotactic structure and being insoluble in (non-extractable i with) boiling n-heptane.
While said polypropylene is adapted to use in many commercially important applications, its impact strengih at .
Il .
` ' temperatures of 0C or less is rather low, particularly for so-called commercial grade polypropylene.
Different ways of improving the impact strength of the l polypropylene at low temperatures without unacceptable adverse 1 affect on its other properties, including its flexural rigidity and thermal resistance have been proposed.
The technique which is most widely used for achieving that objective consists in polymeriæing propylene in contact with ¦ a Ziegler/Natta stereospecific catalyst until most of the propy-1 lene is polymerized and then, during the final stage of the propylene polymerization feeding a different olefin, in particular ethylene, to the polymerization zone and continuing '1 the polymerization until the amount of the added olefin, e.g., ¦¦ ethylene, polymerized is from 1% to 20% of the total (final) 1I polymeric composition obtained.
USP 3,624,184 discloses a typical method which is widely followed. According to that method, propylene is first polymerized in an inert hydrocarbon solvent such as n-heptane and in the presence of a stereospecific polymerization catalyst ~0 prepared by mixing a Ti trihalide with a dialkyl Al monohalide to obtain a poly~erization slurry, i.e., a slurry of polypropylene in the n-heptane. After "flash-off" of unreacted propylene until the slurry comprises a controlled amount of unreacted propylene, the slurry is preferably transferred to a second reactor, a mixture of ethylene and propylene in a molar ratio ranging, in general, from 1 to 6 is introduced into the second reactor, and the polymerization is continued until the amount of polymerized 'I 1050192 ethylene reaches a prefixed value which, generally, i9 rom 5%
to 2~/o by weight.
The main disadvantage of that process - which in practice prevents conducting the polymerization continuously and involves many difficulties in batch polymerization - is that during the polymerization of ethylene in the presence of propylene Ij dissolved in the reaction medium, or in the presence of propylene I¦ fed in with the ethylene, considerable amounts of rubbery ¦¦ ethylene/propylene copolymers soluble in the reaction medium are j formed, which give rise to considerable difficulties in the heat ¦ exchange and in transfer of the polymerization slurry.
I
THE PRESE~T INVENTION
One object of this invention is to provide a new method for improving the low~temperature characteristics of the composi-¦¦ tions based on isotactic polypropylene which avoids or minimizes ¦¦ the problems encountered in the widely used prior art process ¦I discussed supra.
~¦ That and other objects are achieved by the method of the invention which is a two-step method with critical modifica-tions which make it possible to avoid, or to substantially minimize, the disadvantages of the known two-step method.
The present method for making compositions which, while containing at least 50~/O by weight of isotactic polypropylene, have a high resistance to impact at temperatures of 0C and below, comprises the step of (1) polymerizing propylene in an inert liquid hydrocarbon medium or diluent and in the presence of a _3_ stereospecific catalyst obtained by mixing a Ti trihalide, such as crystalline TiCl3, with a dialkyl Al monohalide, such as die-thyl Al Chloride, and the step (2) of feeding ethylene or a mix-ture of ethylene and propylene to the polymerization slurry obtai-ned in step ~1) and continuing the polymerization until the amount of polymerized ethylene is, at most, 20% of the total polymeric composition.
~owever, in the present method, the second step comprises one or more ethylene/propylene copolymerization steps in which the ethylene/propylene molar ratio is at least one of the following:
(A) the ratio of ethylene fed to propylene present in the system ranges from 1/99 to 40/60, preferably from 5/95 to 30/70, and the amount of copolymer formed is comprised between 3% and 8% by weight of the total (final) polymeric composition;
and/or (B) the ethylene/propylene molar ratio in the ethylene/ .
propylene mixture fed to the polymerization slurry ranges from 60/40 to 85/15, and the amount of copo-lymer formed is comprised between 3% and 18% of the total (final) polymeric composition obtained.
Said copolymerizations carried-out in accordance wlth (A) or (B) are the essence of the present invention and process in that they make possible composition which, although consist- .
ing for at least 50% by weight of isotactic polypropylene, ne-vertheless have high impact resistance at low temperatures, ~ithout any appreciable deterioration of the other valuable 1050:~9Z
properties of compositions the essential constituent of which is isotactic polypropylene while, at the same time, avoiding the problems encountered with respect to heat exchange and transfer of the polymerization slurry, even when the final polymerization product has a content of combined ethylene as high as 2~/o~
In the practice of this invention the inert liquid hydrocarbon polymerization medium or diluent is an aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic hydro-carbon, such as, for example, hexane, cyclohexane, heptane, xylene or the like; the stereospecific catalyst is of the Ziegler/, Natta type and obtained by mixing a titanium trihalide (for example TiC13 obtained by reduction of TiC14 with Al or with organometallic compounds of Al preferably complexed with electron-donor compounds) with dialkyl Al monohalides (for example (C2H5)2 AlCl).
Step (1) of the process is generally carried out in the presence of hydrogen as molecular weight regulator.
A presently preferred embodiment of the process comprises the following operations:
~a) producing isotactic polypropylene by polymerizin~
propylene in a hydrocarbon solvent (e.g., heptane) at a temperature of from 50C to 80-C and at a pressure between 3 and 10 kg~cm gauge, in the presence of hydrogen as molecular weight modifier, and of a catalyst obtained by mixing TiC13 (or TiC13 complexed with electron-donors) with (C2H5)2 AlCl; a suspension of substantially isotactic polypropylene in the hydrocarbon solvent is thus obtained (and referred to herein as the polymerization slurry of the first step);
l :I~SO~g2 (b) regulation of the propylene concentration in th~
slurry, generally by reducing the pressure to even lower than 0.2 Xg/cm gauge (flashing) and, prefe-rably but not necessarily, raising the temperature of the system;
(c) introduc-tion of ethylene into the propylene contai-ning slurry, in an amount such as to obtain a mo-lar ratio of the fed ethylene to propylene existing in the system of from 1/99 to 40/60, allowing the mixture of the two monomers to polymerize at a :
temperature of from 60C to 80C and at a pressure generally lower than 10 kg/cm gauge and usually comprised between 0.2 and 2.0 kg/cm gauge, until the resulting ethylene/propylene copolymer consti-tutes 3% to 8~, preferably 4% to 6% by weight of the total polymeric composition and finally, preferably but not necessarily (d) introducing into the polymerization slurry of (c) ethylene or an ethylene/propylene mixture very rich in ethylene and preferably containing more than 80~ by moles of ethylene, allowing such mixtures to polymerize at a temperature of from 60C to 80C .
. and at a pressure generally lower than 10 kgjcm2 gauge, usually comprised between 0.2 and 2.0 kg/cm2 gauge.
, .
. In an.equally advantageous alternative procedure, ~c) and/or (d) are replaced by . (c') which consists in feeding into the slurry of ~b) andjor that of ~c) ethylene continously and pro-pylene discontinously to obtain, during the pXopy-lene feeding, a molar ratio of ethylene to propylene comprised between 60/40 and 85/15, and in the fed as a whole a molar ratio of at least 80~20 between .
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the total amount of ethylene fed and the total amount of propylene fed; both monomers are poly-merized at a temperature of from 60C to 80C and l at a pressure generally lower than 10 kg/cm gauge, usually between 0.2 and 2.0 kg/cm2 gauge, until the resulting copolymer makes up 3% to l~/o~
preferably 4% to ~/0 by weight of the total composition.
After such operations [(a) to (d)] or [~a), (b) and (c')], the catalyst is deactivated, if necessary, by the addition~
of lower aliphatic alcohols and washed. Thereafter, t.e poly- ¦
meric material is separated from the hydrocarbon solvent and the resulting polypropylene composition is dried.
Operations (a) to (d) and (c') may be carried out in one reactor or in more than one reactor. In the latter case, the production of isotactic polypropylene ~operation (a)] occurs in a reactor (primary reactor) and operations (b), the propylene concentration regulation, and (c), ethylene feeding, occur in a flashing apparatus. Finally, operation (d) or (c') is conducted in another reactor (secondary reactor).
Transfer of the polymerizatlon slurry from one reactor to another can be effected without difficulty by using the systems known to those skilled in the art. Furthermore, it is particularly easy to secure effective thermal control of ~he 2S polymerization reactions during all operations of the process.
In practice, the present process can be carried out continuously without having to use very complicated and expensive devices for the transfer of the slurries or having to stop the reactor~ for assuring thermal control of the polymerization reactions.
_ . n The polypropylene compositions obtained by the process of this invention exhibit melt index values (g/10') comprised between 0.1 and 10 and have a number of excellent characteristics, in particular:
¦ ~ modulus of ela~ticity to flexure comprised between 750~ and 13,000 kg/cm;
~ emhrittlement temperature comprised between -15 and -60C;
o resilience at 0C comprised between 5 and 20 kg/cm/cm; and ~ transition temperature D/F comprised between 0C and -50C.
l The following,examples are given to illustrate the ¦ essential features of the invention, and are not intended to be limiting.
~ This example illustrates the preparation of polypropy- ¦
lene compositions according to a continuous process comprlsing, in the order given, operatibns (a), (b), (c)-and (d) as defined hereinabove. The operating conditions for each single step are described hereinafter.
I OPeratiOn la) , A 4 m (primary) reactor was continuously fed with:
~ hydrocarbon solvent (technical heptane) - 250 l/hour o polymerization catalyst 3 TiC13.AlC13 ~obtained from TiC14 by reduction with aluminum and successive activation by 25' dry-grinding, complexed with methyl benzoate (MB); TiC13/MB molar ratio =
0.1) in the form of heptane solution containing 7 g/l of TiC13 ' - 40 l/hour ,. ~ , lOSOl9Z
molecular weight regulator: hydrogen - 120 l/hour ~ propylene - 150 kg/hour The reaction conditions were:
o temperature - 60C
o manometric pressure - 5-6 kg/cm gauge o residence time - 4 hours.
By operating as descri~ed hereinabove, it was possible to obtain 136 kg/hour of substantially isotactic polypropylene, suspended in the hydrocarb~n solvent, that contained still active 10- I catalyst and unreacted propyiene. This suspension is referred~to, for simplicity, as polymerization slurry.
OPeration (b) The polymerization slurry was transferred to another reactor (flashing apparatus) of 1.8 m , by pressure difference lS (from 5-6 kg/cm g. in the primary reactor to 0.2 kg~/cm2 g. in the flashing apparatus), bringing the temperature to 70C and allowing the unreacted propylene in excess to flash; a propylene-saturated slurry (at the pressure and temperature indicated hereinabove~ was thus obtained.
Operation tc) The flashing apparatus was fed with 150 l/h of technical heptane and with 1 kg/h of ethylene so as to obtain an ethylene/
propylene molar ratio equal to 25/75, whereupon the monomeric mixture was polymerized at a temperature of 70C, at a pressure of 0.2 kg/cm g and with a residence time in the flashing apparatus of 1 hour.
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A rubbery copolymer in an amount of 6.8 kg/h corres-ponding to 4. ~/o of the total composition, was thus produced.
OPeration (d) The polymeri~ation slurry of (c) was transferred by means of pumps to another reactor (secondary) of 1.5 m , into which an ethylene/propylene mixture in a molar ratio of 97/3, ¦ -corresponding to a feeding of 30 kg/h of ethylene and of 1,86 kg/h of propylene, was introduced; the whole was allowed to polymerize at a temperature of 70C, at a pressure of 0.7 kg/cm g., with a residence time of 2 hours. By this procedure, a crystalline copolymer containing a high percentage of ethylene was produced in an amount of 29.9 kg/h corresponding to 18.4% by weight of the total composition. Still operating continuously the polymeriza-tion slurry of the secondary reactor was transferred at first into a reactor wherein it was treated at 85C with n-butanol, in order i to deactivate the catalyst, then subjected to washing with water, centrifuged at 50C and dried at a maximum temperature of 125C.
The resulting polypropylene composition having a final content of combined ethylene equal to 12% by weight, exhibited the following physical-chemical and technical characteristics:
o melt index ~g/10') 0.5 e melting point C 172 ,1 o elasticity modulus kg/cm 8,000 o resilience Xg/cm/cm 11.8 D embrittlement temp. C -55 . j .
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Tensile test: ¦
~ max. tensile strength kg/cm 260 e elongation % 570 o yield strength kg!cm 234 o transition temp. DF C -25.5 0 viscosity dl/g 3.4 This test for preparing polypropylene compositions was conducted continuously for 44 days without meeting with any difficulties regarding the heat exchange and the transfer of the slurry from one reactor to another.
By way of comparison, the test was repeated, but t without operation (c), i.e., without the feeding of ethylene into the flashing apparatus. In this case, a polymeric product exhibiting characteristics similar to those of the product according to this invention was obtained, but, due to troubles with respect to the heat exchange and slurry transfer, the reactor run had to be stopped after about 24 hours.
This example illustrates the preparation of polypropy-lene compositions according to a continuous process comprising in the order given, operations ~a), ~b), (c) and Ic') as described hereinabove. Thc operating conditions in the primary reactor and in the flashing apparatus - operations (a), (b) and (c) were the same as in Example 1. Operation (d) was rcplaced by (c'), during which ethylene was fed in continuously and propylene was fed i~
, discontinuously.
The polymerization slurry of (c) was transferred by means of pumps into another 1.5 m reactor (secondary), to which ethylene and propylene were fed continuously and discontinuously respectively, operating at a temperature of 70C and at a pressure of 0.7 - 1 kg/cm g., with a residence time of 2 hours.
More particularly in a first test, A, an ethylene/propylene mixture having a molar ratio = 80/20 was fed in first for 10 minutes, then ethylene alone was fed in for 20 minutes, after which an ethylene/propylene mixture (80/20) was fed in for another 10 minutes and finally ethylene alone for 20 minutes, repeating this type of feeding for all the time required for test !
A.
In a second test, B, the type of hourly feeding was similar to that of test A, the only difference consisting in that, during the propylene feeding, the ethylene/propylene molar ratio . was 70/30 instead of 80.~20.
In test A, the ethylene/propylene total molar ratio was 92.5/7.5, while in test B it was 88/12.
Unlike the preceding example, in operation (c') of this Example a predominantly rubbery copolymer was formed during the feeding of propylene, and a predominantly crystalline copolymer . was formed during the feeding of ethylene only.
~y operating successively according to example 1, poly-propylene compositions were obtained having contents of combined total ethylene, of isotac~ic polypropylene, of rubbery and , crystalline copolymer as specified below:
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1~5019Z
Test A Test B
Content of substantially isotactic polypropylene, % by weight 80.8 79.8 total content of combined ethylene, % by weight 12.0 9.9 rubbery copolymer operation (c) % by weight 4.3 4.3 rubbery copolymer operation (c') % by weight 6.1 7.2 crystalline copolymer operation (c') % by weight 8.8 8.7 The physical-mechanical and thermal characteristics of the two polypropylene compositions are listed below: ¦
Test A Test B
melt index g/10' 0.93 1.8 melting point C 169 168 elasticity modulus kg/cm - 8100 9500 resilience (at 0C) kg/cm/cm 10.9 7.9 embrittlement temp. C -40.5 -21.5 Tensile test:
¦ o max. tensile strength Xg/cm2 260 266 ¦ ~ elongation % 650 766 e yield strength kg/cm transition temp. DF C -12.5 -7 I viscosity 3 2.7 Tests A and B were conducted continuously for a tim~
period of 44 days without encountering any difficulty.
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ll 105019Z
By way of comparison, tests A and B were repeated, but replacing (c') with (d), during which ethylene and propylene were fed continously in molar ratios equal to those found on the whole in (c') of tests A and B according to this invention.
In both comparison tests, polymeric products were ob-tained exhibiting properties analogous with those of the pro-ducts of tests A and B, but, owing to troubles with the heat exchange and slurry transfer, the reactors run had to be stopped after about 30 hours.
This example illustrates the preparation of polypropy-lene compositions employing operations, (a), (b), (c) and (d) as defined herein, all conducted in the same reactor. To such pur-pose, a 20 l reactor was charged with:
3 TiCl3.AlCl3 8.0 g Al~C2H5)2Cl 16.0 g technical heptane 10 l propylene up to 4 kg/cm2 g.
The reactor was maintained at 65 C and in a time of 1.5 hours 2.5 kg of substantially isotactic polypropylene were-obtained Coperation ~a)~. The isotacticity index of tha polypropylene was between 90 and 93.5, depending on the tests.
The pressure in the reactor was successively reduced to 1 kg/~m2 g., thus obtaining a propylene-saturated (130 g) polymeriza-tion slurry[ operation (b)~; then ethylene was fed in until the slurry had absorbed it up to a pressure of 0.5 kg/cm g; subsequently, by feeding in additional ethylene, ~05019Z
the pressure was brought again to 1 kg/cm g., allowing the ethylene/propylene mixture to polymerize [operation tc)]; finally ethylene/propylene mixtures very rich in ethylene (at least 9~/0 by moles) were continuously fed in and allowedto polymerize in ¦ the reaction slurry. At the conclusion of the polymerization the ¦ catalyst was deactivated and the polypropylene composition thus I obtained was separated and purified as described in Example 1.
¦ The following Table I gives the characteristics of the polypropylene compositions obtained as a function of the operating conditions in (c) and (d) and of the polypropylene type ~isotacticity index) produced in operation (a).
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~ g TABLE I
Test 1 Test 2 Test 3 Test 4 Test 5 ¦
OPeration ta) Isotacticity index: % 93.5 93.5 90.5 92 90 Operation (c) Residual propylene: g 130 130130 130 130 Ethylene fed: g 10 10 30 10 10 Ethylene/propylene molar ratio: 10/90 10/90 25/75 10/90 10/90 !
Op,eration (d) Etilylene fed: g 450 450 4S0450 450 Propylene fed: g 50 20 70 50 20 Ethylene/propylene molar ratio: 94/6 97/3 90/10 94/6 97/3 Ethylene final content: % by weight 14.9 17.5 11 10.4 12~5 Melt flow index: g/10' 0.57 0.45 3.5 2.4 1.9 Embrittlement temperature: C -43 -41 -44 -34 -28 . Flexural rigidity kg/m 11,100 11,050 10,400 ~1,050 11,750 Resilience at OC
. kg/cm/~m 9.2 8.2 8.8 8.2 8.0 Tensile tests Max. tensile strength: 2 kg/cm 302 304 257 280 268 Elongation at break: % 240 161 660 690 490 Yield stress: kg/cm 302 304 257 280 268 . .~
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This example illustrates the preparation of the poly-propylene compositions by a continuous process that comprises, in the order given, operations (a), (b) and (c') as defined herein.
The operating conditions for (a) and (b) were the same as in Example 1: in (c') the temperature was 70C, the pressure was 0.7 - 1 kg/cm gauge and the residence time in the reactor (secondary) was 2 hours. The feeding modali-ties of ethylene and propylene during (c') and the characteristics of the polypropylene compositions thus obtained are reported in Tables II and III.
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Tests l,to 10 were conducted 'continuously,for a 44-day period without meeting with any difficulty. Test 10 was repeated ¦ ,, for comparative purposes, but replacing tc') with a (d) in which ethylene and propylene were fed continuously in molar ratios equal to those generally used in (c') of test 10 according to the present invention.
In the comparative test, a polymeric material was obtained exhibiting characteristics rather similar to those of the product of test 10 but, due to troubles with heat exchange and slurry transfer, the run of the reactors had to be stopped ~ after abo 30 hours.
ll ; , -20- ~ !
~j BACKGROU~D OF THE I~VE~TIO~
Isotactic polypropylene, as defined in ~atta et al SP 3,112,300, is a polypropylene which consists essentially of isotactic macromolecules, i.e., macromolecules having substantiall the isotactic structure and being insoluble in (non-extractable i with) boiling n-heptane.
While said polypropylene is adapted to use in many commercially important applications, its impact strengih at .
Il .
` ' temperatures of 0C or less is rather low, particularly for so-called commercial grade polypropylene.
Different ways of improving the impact strength of the l polypropylene at low temperatures without unacceptable adverse 1 affect on its other properties, including its flexural rigidity and thermal resistance have been proposed.
The technique which is most widely used for achieving that objective consists in polymeriæing propylene in contact with ¦ a Ziegler/Natta stereospecific catalyst until most of the propy-1 lene is polymerized and then, during the final stage of the propylene polymerization feeding a different olefin, in particular ethylene, to the polymerization zone and continuing '1 the polymerization until the amount of the added olefin, e.g., ¦¦ ethylene, polymerized is from 1% to 20% of the total (final) 1I polymeric composition obtained.
USP 3,624,184 discloses a typical method which is widely followed. According to that method, propylene is first polymerized in an inert hydrocarbon solvent such as n-heptane and in the presence of a stereospecific polymerization catalyst ~0 prepared by mixing a Ti trihalide with a dialkyl Al monohalide to obtain a poly~erization slurry, i.e., a slurry of polypropylene in the n-heptane. After "flash-off" of unreacted propylene until the slurry comprises a controlled amount of unreacted propylene, the slurry is preferably transferred to a second reactor, a mixture of ethylene and propylene in a molar ratio ranging, in general, from 1 to 6 is introduced into the second reactor, and the polymerization is continued until the amount of polymerized 'I 1050192 ethylene reaches a prefixed value which, generally, i9 rom 5%
to 2~/o by weight.
The main disadvantage of that process - which in practice prevents conducting the polymerization continuously and involves many difficulties in batch polymerization - is that during the polymerization of ethylene in the presence of propylene Ij dissolved in the reaction medium, or in the presence of propylene I¦ fed in with the ethylene, considerable amounts of rubbery ¦¦ ethylene/propylene copolymers soluble in the reaction medium are j formed, which give rise to considerable difficulties in the heat ¦ exchange and in transfer of the polymerization slurry.
I
THE PRESE~T INVENTION
One object of this invention is to provide a new method for improving the low~temperature characteristics of the composi-¦¦ tions based on isotactic polypropylene which avoids or minimizes ¦¦ the problems encountered in the widely used prior art process ¦I discussed supra.
~¦ That and other objects are achieved by the method of the invention which is a two-step method with critical modifica-tions which make it possible to avoid, or to substantially minimize, the disadvantages of the known two-step method.
The present method for making compositions which, while containing at least 50~/O by weight of isotactic polypropylene, have a high resistance to impact at temperatures of 0C and below, comprises the step of (1) polymerizing propylene in an inert liquid hydrocarbon medium or diluent and in the presence of a _3_ stereospecific catalyst obtained by mixing a Ti trihalide, such as crystalline TiCl3, with a dialkyl Al monohalide, such as die-thyl Al Chloride, and the step (2) of feeding ethylene or a mix-ture of ethylene and propylene to the polymerization slurry obtai-ned in step ~1) and continuing the polymerization until the amount of polymerized ethylene is, at most, 20% of the total polymeric composition.
~owever, in the present method, the second step comprises one or more ethylene/propylene copolymerization steps in which the ethylene/propylene molar ratio is at least one of the following:
(A) the ratio of ethylene fed to propylene present in the system ranges from 1/99 to 40/60, preferably from 5/95 to 30/70, and the amount of copolymer formed is comprised between 3% and 8% by weight of the total (final) polymeric composition;
and/or (B) the ethylene/propylene molar ratio in the ethylene/ .
propylene mixture fed to the polymerization slurry ranges from 60/40 to 85/15, and the amount of copo-lymer formed is comprised between 3% and 18% of the total (final) polymeric composition obtained.
Said copolymerizations carried-out in accordance wlth (A) or (B) are the essence of the present invention and process in that they make possible composition which, although consist- .
ing for at least 50% by weight of isotactic polypropylene, ne-vertheless have high impact resistance at low temperatures, ~ithout any appreciable deterioration of the other valuable 1050:~9Z
properties of compositions the essential constituent of which is isotactic polypropylene while, at the same time, avoiding the problems encountered with respect to heat exchange and transfer of the polymerization slurry, even when the final polymerization product has a content of combined ethylene as high as 2~/o~
In the practice of this invention the inert liquid hydrocarbon polymerization medium or diluent is an aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic hydro-carbon, such as, for example, hexane, cyclohexane, heptane, xylene or the like; the stereospecific catalyst is of the Ziegler/, Natta type and obtained by mixing a titanium trihalide (for example TiC13 obtained by reduction of TiC14 with Al or with organometallic compounds of Al preferably complexed with electron-donor compounds) with dialkyl Al monohalides (for example (C2H5)2 AlCl).
Step (1) of the process is generally carried out in the presence of hydrogen as molecular weight regulator.
A presently preferred embodiment of the process comprises the following operations:
~a) producing isotactic polypropylene by polymerizin~
propylene in a hydrocarbon solvent (e.g., heptane) at a temperature of from 50C to 80-C and at a pressure between 3 and 10 kg~cm gauge, in the presence of hydrogen as molecular weight modifier, and of a catalyst obtained by mixing TiC13 (or TiC13 complexed with electron-donors) with (C2H5)2 AlCl; a suspension of substantially isotactic polypropylene in the hydrocarbon solvent is thus obtained (and referred to herein as the polymerization slurry of the first step);
l :I~SO~g2 (b) regulation of the propylene concentration in th~
slurry, generally by reducing the pressure to even lower than 0.2 Xg/cm gauge (flashing) and, prefe-rably but not necessarily, raising the temperature of the system;
(c) introduc-tion of ethylene into the propylene contai-ning slurry, in an amount such as to obtain a mo-lar ratio of the fed ethylene to propylene existing in the system of from 1/99 to 40/60, allowing the mixture of the two monomers to polymerize at a :
temperature of from 60C to 80C and at a pressure generally lower than 10 kg/cm gauge and usually comprised between 0.2 and 2.0 kg/cm gauge, until the resulting ethylene/propylene copolymer consti-tutes 3% to 8~, preferably 4% to 6% by weight of the total polymeric composition and finally, preferably but not necessarily (d) introducing into the polymerization slurry of (c) ethylene or an ethylene/propylene mixture very rich in ethylene and preferably containing more than 80~ by moles of ethylene, allowing such mixtures to polymerize at a temperature of from 60C to 80C .
. and at a pressure generally lower than 10 kgjcm2 gauge, usually comprised between 0.2 and 2.0 kg/cm2 gauge.
, .
. In an.equally advantageous alternative procedure, ~c) and/or (d) are replaced by . (c') which consists in feeding into the slurry of ~b) andjor that of ~c) ethylene continously and pro-pylene discontinously to obtain, during the pXopy-lene feeding, a molar ratio of ethylene to propylene comprised between 60/40 and 85/15, and in the fed as a whole a molar ratio of at least 80~20 between .
, - 6 -111~5~L9Z
the total amount of ethylene fed and the total amount of propylene fed; both monomers are poly-merized at a temperature of from 60C to 80C and l at a pressure generally lower than 10 kg/cm gauge, usually between 0.2 and 2.0 kg/cm2 gauge, until the resulting copolymer makes up 3% to l~/o~
preferably 4% to ~/0 by weight of the total composition.
After such operations [(a) to (d)] or [~a), (b) and (c')], the catalyst is deactivated, if necessary, by the addition~
of lower aliphatic alcohols and washed. Thereafter, t.e poly- ¦
meric material is separated from the hydrocarbon solvent and the resulting polypropylene composition is dried.
Operations (a) to (d) and (c') may be carried out in one reactor or in more than one reactor. In the latter case, the production of isotactic polypropylene ~operation (a)] occurs in a reactor (primary reactor) and operations (b), the propylene concentration regulation, and (c), ethylene feeding, occur in a flashing apparatus. Finally, operation (d) or (c') is conducted in another reactor (secondary reactor).
Transfer of the polymerizatlon slurry from one reactor to another can be effected without difficulty by using the systems known to those skilled in the art. Furthermore, it is particularly easy to secure effective thermal control of ~he 2S polymerization reactions during all operations of the process.
In practice, the present process can be carried out continuously without having to use very complicated and expensive devices for the transfer of the slurries or having to stop the reactor~ for assuring thermal control of the polymerization reactions.
_ . n The polypropylene compositions obtained by the process of this invention exhibit melt index values (g/10') comprised between 0.1 and 10 and have a number of excellent characteristics, in particular:
¦ ~ modulus of ela~ticity to flexure comprised between 750~ and 13,000 kg/cm;
~ emhrittlement temperature comprised between -15 and -60C;
o resilience at 0C comprised between 5 and 20 kg/cm/cm; and ~ transition temperature D/F comprised between 0C and -50C.
l The following,examples are given to illustrate the ¦ essential features of the invention, and are not intended to be limiting.
~ This example illustrates the preparation of polypropy- ¦
lene compositions according to a continuous process comprlsing, in the order given, operatibns (a), (b), (c)-and (d) as defined hereinabove. The operating conditions for each single step are described hereinafter.
I OPeratiOn la) , A 4 m (primary) reactor was continuously fed with:
~ hydrocarbon solvent (technical heptane) - 250 l/hour o polymerization catalyst 3 TiC13.AlC13 ~obtained from TiC14 by reduction with aluminum and successive activation by 25' dry-grinding, complexed with methyl benzoate (MB); TiC13/MB molar ratio =
0.1) in the form of heptane solution containing 7 g/l of TiC13 ' - 40 l/hour ,. ~ , lOSOl9Z
molecular weight regulator: hydrogen - 120 l/hour ~ propylene - 150 kg/hour The reaction conditions were:
o temperature - 60C
o manometric pressure - 5-6 kg/cm gauge o residence time - 4 hours.
By operating as descri~ed hereinabove, it was possible to obtain 136 kg/hour of substantially isotactic polypropylene, suspended in the hydrocarb~n solvent, that contained still active 10- I catalyst and unreacted propyiene. This suspension is referred~to, for simplicity, as polymerization slurry.
OPeration (b) The polymerization slurry was transferred to another reactor (flashing apparatus) of 1.8 m , by pressure difference lS (from 5-6 kg/cm g. in the primary reactor to 0.2 kg~/cm2 g. in the flashing apparatus), bringing the temperature to 70C and allowing the unreacted propylene in excess to flash; a propylene-saturated slurry (at the pressure and temperature indicated hereinabove~ was thus obtained.
Operation tc) The flashing apparatus was fed with 150 l/h of technical heptane and with 1 kg/h of ethylene so as to obtain an ethylene/
propylene molar ratio equal to 25/75, whereupon the monomeric mixture was polymerized at a temperature of 70C, at a pressure of 0.2 kg/cm g and with a residence time in the flashing apparatus of 1 hour.
_9_ ' .
10501~Z
A rubbery copolymer in an amount of 6.8 kg/h corres-ponding to 4. ~/o of the total composition, was thus produced.
OPeration (d) The polymeri~ation slurry of (c) was transferred by means of pumps to another reactor (secondary) of 1.5 m , into which an ethylene/propylene mixture in a molar ratio of 97/3, ¦ -corresponding to a feeding of 30 kg/h of ethylene and of 1,86 kg/h of propylene, was introduced; the whole was allowed to polymerize at a temperature of 70C, at a pressure of 0.7 kg/cm g., with a residence time of 2 hours. By this procedure, a crystalline copolymer containing a high percentage of ethylene was produced in an amount of 29.9 kg/h corresponding to 18.4% by weight of the total composition. Still operating continuously the polymeriza-tion slurry of the secondary reactor was transferred at first into a reactor wherein it was treated at 85C with n-butanol, in order i to deactivate the catalyst, then subjected to washing with water, centrifuged at 50C and dried at a maximum temperature of 125C.
The resulting polypropylene composition having a final content of combined ethylene equal to 12% by weight, exhibited the following physical-chemical and technical characteristics:
o melt index ~g/10') 0.5 e melting point C 172 ,1 o elasticity modulus kg/cm 8,000 o resilience Xg/cm/cm 11.8 D embrittlement temp. C -55 . j .
. . , I .
-10- , I
. . . ~ , . .
~LE)51D19Z
Tensile test: ¦
~ max. tensile strength kg/cm 260 e elongation % 570 o yield strength kg!cm 234 o transition temp. DF C -25.5 0 viscosity dl/g 3.4 This test for preparing polypropylene compositions was conducted continuously for 44 days without meeting with any difficulties regarding the heat exchange and the transfer of the slurry from one reactor to another.
By way of comparison, the test was repeated, but t without operation (c), i.e., without the feeding of ethylene into the flashing apparatus. In this case, a polymeric product exhibiting characteristics similar to those of the product according to this invention was obtained, but, due to troubles with respect to the heat exchange and slurry transfer, the reactor run had to be stopped after about 24 hours.
This example illustrates the preparation of polypropy-lene compositions according to a continuous process comprising in the order given, operations ~a), ~b), (c) and Ic') as described hereinabove. Thc operating conditions in the primary reactor and in the flashing apparatus - operations (a), (b) and (c) were the same as in Example 1. Operation (d) was rcplaced by (c'), during which ethylene was fed in continuously and propylene was fed i~
, discontinuously.
The polymerization slurry of (c) was transferred by means of pumps into another 1.5 m reactor (secondary), to which ethylene and propylene were fed continuously and discontinuously respectively, operating at a temperature of 70C and at a pressure of 0.7 - 1 kg/cm g., with a residence time of 2 hours.
More particularly in a first test, A, an ethylene/propylene mixture having a molar ratio = 80/20 was fed in first for 10 minutes, then ethylene alone was fed in for 20 minutes, after which an ethylene/propylene mixture (80/20) was fed in for another 10 minutes and finally ethylene alone for 20 minutes, repeating this type of feeding for all the time required for test !
A.
In a second test, B, the type of hourly feeding was similar to that of test A, the only difference consisting in that, during the propylene feeding, the ethylene/propylene molar ratio . was 70/30 instead of 80.~20.
In test A, the ethylene/propylene total molar ratio was 92.5/7.5, while in test B it was 88/12.
Unlike the preceding example, in operation (c') of this Example a predominantly rubbery copolymer was formed during the feeding of propylene, and a predominantly crystalline copolymer . was formed during the feeding of ethylene only.
~y operating successively according to example 1, poly-propylene compositions were obtained having contents of combined total ethylene, of isotac~ic polypropylene, of rubbery and , crystalline copolymer as specified below:
. ' , 'i'' . -12-I'' ;' .
1~5019Z
Test A Test B
Content of substantially isotactic polypropylene, % by weight 80.8 79.8 total content of combined ethylene, % by weight 12.0 9.9 rubbery copolymer operation (c) % by weight 4.3 4.3 rubbery copolymer operation (c') % by weight 6.1 7.2 crystalline copolymer operation (c') % by weight 8.8 8.7 The physical-mechanical and thermal characteristics of the two polypropylene compositions are listed below: ¦
Test A Test B
melt index g/10' 0.93 1.8 melting point C 169 168 elasticity modulus kg/cm - 8100 9500 resilience (at 0C) kg/cm/cm 10.9 7.9 embrittlement temp. C -40.5 -21.5 Tensile test:
¦ o max. tensile strength Xg/cm2 260 266 ¦ ~ elongation % 650 766 e yield strength kg/cm transition temp. DF C -12.5 -7 I viscosity 3 2.7 Tests A and B were conducted continuously for a tim~
period of 44 days without encountering any difficulty.
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ll 105019Z
By way of comparison, tests A and B were repeated, but replacing (c') with (d), during which ethylene and propylene were fed continously in molar ratios equal to those found on the whole in (c') of tests A and B according to this invention.
In both comparison tests, polymeric products were ob-tained exhibiting properties analogous with those of the pro-ducts of tests A and B, but, owing to troubles with the heat exchange and slurry transfer, the reactors run had to be stopped after about 30 hours.
This example illustrates the preparation of polypropy-lene compositions employing operations, (a), (b), (c) and (d) as defined herein, all conducted in the same reactor. To such pur-pose, a 20 l reactor was charged with:
3 TiCl3.AlCl3 8.0 g Al~C2H5)2Cl 16.0 g technical heptane 10 l propylene up to 4 kg/cm2 g.
The reactor was maintained at 65 C and in a time of 1.5 hours 2.5 kg of substantially isotactic polypropylene were-obtained Coperation ~a)~. The isotacticity index of tha polypropylene was between 90 and 93.5, depending on the tests.
The pressure in the reactor was successively reduced to 1 kg/~m2 g., thus obtaining a propylene-saturated (130 g) polymeriza-tion slurry[ operation (b)~; then ethylene was fed in until the slurry had absorbed it up to a pressure of 0.5 kg/cm g; subsequently, by feeding in additional ethylene, ~05019Z
the pressure was brought again to 1 kg/cm g., allowing the ethylene/propylene mixture to polymerize [operation tc)]; finally ethylene/propylene mixtures very rich in ethylene (at least 9~/0 by moles) were continuously fed in and allowedto polymerize in ¦ the reaction slurry. At the conclusion of the polymerization the ¦ catalyst was deactivated and the polypropylene composition thus I obtained was separated and purified as described in Example 1.
¦ The following Table I gives the characteristics of the polypropylene compositions obtained as a function of the operating conditions in (c) and (d) and of the polypropylene type ~isotacticity index) produced in operation (a).
. -15-~. . ~ ~.
~ g TABLE I
Test 1 Test 2 Test 3 Test 4 Test 5 ¦
OPeration ta) Isotacticity index: % 93.5 93.5 90.5 92 90 Operation (c) Residual propylene: g 130 130130 130 130 Ethylene fed: g 10 10 30 10 10 Ethylene/propylene molar ratio: 10/90 10/90 25/75 10/90 10/90 !
Op,eration (d) Etilylene fed: g 450 450 4S0450 450 Propylene fed: g 50 20 70 50 20 Ethylene/propylene molar ratio: 94/6 97/3 90/10 94/6 97/3 Ethylene final content: % by weight 14.9 17.5 11 10.4 12~5 Melt flow index: g/10' 0.57 0.45 3.5 2.4 1.9 Embrittlement temperature: C -43 -41 -44 -34 -28 . Flexural rigidity kg/m 11,100 11,050 10,400 ~1,050 11,750 Resilience at OC
. kg/cm/~m 9.2 8.2 8.8 8.2 8.0 Tensile tests Max. tensile strength: 2 kg/cm 302 304 257 280 268 Elongation at break: % 240 161 660 690 490 Yield stress: kg/cm 302 304 257 280 268 . .~
., , I .
.. . .
~_. ..
~05a~9Z
This example illustrates the preparation of the poly-propylene compositions by a continuous process that comprises, in the order given, operations (a), (b) and (c') as defined herein.
The operating conditions for (a) and (b) were the same as in Example 1: in (c') the temperature was 70C, the pressure was 0.7 - 1 kg/cm gauge and the residence time in the reactor (secondary) was 2 hours. The feeding modali-ties of ethylene and propylene during (c') and the characteristics of the polypropylene compositions thus obtained are reported in Tables II and III.
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1 ~ ~,n 'O r~+WW~WWWW;3r~ V'DO
Ul ~1'~ O N $~ W 1-1 = W W ~ W W W W = ~n t~
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_ ~ v ~n ~ W ~ W ~ w ~ + ~ w w ~ W = = ~ . . ; .
~ a ~ ~C~ c ~ ~c~
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Tests l,to 10 were conducted 'continuously,for a 44-day period without meeting with any difficulty. Test 10 was repeated ¦ ,, for comparative purposes, but replacing tc') with a (d) in which ethylene and propylene were fed continuously in molar ratios equal to those generally used in (c') of test 10 according to the present invention.
In the comparative test, a polymeric material was obtained exhibiting characteristics rather similar to those of the product of test 10 but, due to troubles with heat exchange and slurry transfer, the run of the reactors had to be stopped ~ after abo 30 hours.
ll ; , -20- ~ !
Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Process for preparing polymeric compositions containing at least 50% by weight of isotactic polypropylene, comprising a first step in which propylene is polymerized in an inert liquid hydrocarbon medium at a temperature of from 50°C
to 80°C and at a pressure between 3 and 10 Kg/cm2 gauge, in the presence of hydrogen as molecular weight modifier and of a stereospecific catalyst comprising the product obtained by mixing a titanium trihalide with a dialkyl aluminum monohalide to obtain a polymerization slurry, and a second step in which ethylene, or an ethylene/propylene mixture is fed into the polymerization slurry and the amount of ethylene which is polymerized in the slurry is such that the maximum amount of polymerized ethylene in the slurry is 20% by weight of the total polymeric composition, said process being characterized in that in the second step one or more copolymerizations of ethylene and propylene occur in which the ethylene/propylene molar ratio is at least one of the following:
(A) the ratio between the ethylene fed and propylene present in the polymerization slurry is between 1/99 and 60/40, and the amount of ethylene/propylene copolymer formed in the slurry is from 3% to 8% by weight of the total polymeric composition;
(B) the ratio between ethylene and propylene in the mixture of those monomers which is fed to the polymerization slurry is from 60/40 to 85/15, and the amount of ethylene/propylene copolymer formed in the slurry is from 3% to 18% by weight of the total polymeric composition.
to 80°C and at a pressure between 3 and 10 Kg/cm2 gauge, in the presence of hydrogen as molecular weight modifier and of a stereospecific catalyst comprising the product obtained by mixing a titanium trihalide with a dialkyl aluminum monohalide to obtain a polymerization slurry, and a second step in which ethylene, or an ethylene/propylene mixture is fed into the polymerization slurry and the amount of ethylene which is polymerized in the slurry is such that the maximum amount of polymerized ethylene in the slurry is 20% by weight of the total polymeric composition, said process being characterized in that in the second step one or more copolymerizations of ethylene and propylene occur in which the ethylene/propylene molar ratio is at least one of the following:
(A) the ratio between the ethylene fed and propylene present in the polymerization slurry is between 1/99 and 60/40, and the amount of ethylene/propylene copolymer formed in the slurry is from 3% to 8% by weight of the total polymeric composition;
(B) the ratio between ethylene and propylene in the mixture of those monomers which is fed to the polymerization slurry is from 60/40 to 85/15, and the amount of ethylene/propylene copolymer formed in the slurry is from 3% to 18% by weight of the total polymeric composition.
2. The process of claim 1, in which ethylene only is fed to the polymerization slurry and the ratio (A) between the ethylene fed to the propylene present in the slurry is between 5/95 and 30/70.
3. The process of claim 1, in which a mixture of ethylene and propylene is fed to the polymerization slurry and the ratio (B) of ethylene to propylene in the fed mixture is betweer 65/35 and 80/20.
4. The process of claim 1, in which the copolymerization of ethylene and propylene in the polymerization slurry, is effec-ted by feeding ethylene to the slurry controlling the concentra-tion of propylene in the slurry so that the molar ratio (A) bet-ween the ethylene fed to the slurry and the propylene present therein is from 1/99 to 40/60, and copolymerizing the ethylene and propylene in the slurry at a temperature of from 60°C to 80°C and at a pressure lower than 10 kg/cm2 gauge until the amount of ethylene/propylene copolymer formed amounts to from 3% to 8% of the total polymeric composition.
5. The process of claim 4, in which the molar ratio (A) between the ethylene fed to the polymerization slurry and the propylene present therein is from 5/95 to 30/70.
6. The process of claim 4, in which the amount of ethy-lene/propylene copolymer formed in the slurry is from 4% to 6 of the total polymeric composition.
7. The process of claim 1, in which the copolymerization of ethylene and propylene in polymerization slurry is effected by continously feeding ethylene to the slurry and discontinously feeding propylene thereto to obtain, during the propylene feeding, an ethylene/propylene molar ratio (B) of from 60/40 to 85/15 and in the mixture fed on the whole a molar ratio of at least 80/20 between the total amount of ethylene and propylene fed, copolymeri-zing the ethylene and propylene in the slurry at a temperature of from 60°C to 80°C and at a pressure below 10 kg/cm2, until the amount of copolymer produced is from 3% to 18% by weight of the total polymeric composition.
8. The process of claim 7, in which the ethylene and propylene are copolymerized in the polymerization slurry at a pressure of from 0.2 to 2.0 kg/cm2 gauge.
9. The process of claim 7, in which the amount of ethylene/propylene copolymer formed in the polymerization slurry is from 4% to 8% by weight of the total polymeric composition.
10. The process of claim 1, in which the concentration of unreacted propylene in the polymerization slurry resulting from the polymerization of propylene in the inert hydrocarbon solvent and in the presence of the stereospecific catalyst is regulated and controlled by reducing the pressure in the system.
11. The process of claim 1, in which the concentration of unreacted propylene in the slurry is regulated and controlled by reducing the pressure and varying the temperature in the system.
12. The process of claim 11, in which regulation and control of the concentration of unreacted propylene in the poly-merization slurry is obtained by reducing the pressure in the system to about 0.2 kg/cm2 and adjusting the temperature therein to about 70°C.
13. The process of claim 1 which comprises the following operations:
a) producing isotactic polypropylene by polymerizing propylene in a hydrocarbon solvent at a tempera-ture of from 50°C to 80°C and at a pressure bet-ween 3 and 10 kg/cm2 gauge; a suspension (slurry) of substantially isotactic polypropylene in the hydrocarbon solvent is thus obtained b) regulation of the propylene concentration in the slurry, by reducing the pressure to even lower than 0.2 kg/cm2 gauge (flashing) c) introduction of ethylene into the propylene-containing slurry, in an amount such as to obtain a molar ratio of the fed ethylene to propylene existing in the system of from 1/99 to 40/60, allowing the mixture of the two monomers to polymerize at a temperature of from 60°C to 80°C and at a pressure lower than 10 kg/cm2 gauge until the resulting ethylene/propylene copolymer constitutes 3% to 8%, preferably 4% to 6% by weight of the total polymeric composition and, finally, d) introducing into the polymerization slurry of c) ethylene or an ethylene/propylene mixture containing more than 80% by moles of ethylene, allowing such mixtures to polymerize at a temperature of from 60°C to 80°C and at a pressure lower than 10 kg/cm2 gauge.
a) producing isotactic polypropylene by polymerizing propylene in a hydrocarbon solvent at a tempera-ture of from 50°C to 80°C and at a pressure bet-ween 3 and 10 kg/cm2 gauge; a suspension (slurry) of substantially isotactic polypropylene in the hydrocarbon solvent is thus obtained b) regulation of the propylene concentration in the slurry, by reducing the pressure to even lower than 0.2 kg/cm2 gauge (flashing) c) introduction of ethylene into the propylene-containing slurry, in an amount such as to obtain a molar ratio of the fed ethylene to propylene existing in the system of from 1/99 to 40/60, allowing the mixture of the two monomers to polymerize at a temperature of from 60°C to 80°C and at a pressure lower than 10 kg/cm2 gauge until the resulting ethylene/propylene copolymer constitutes 3% to 8%, preferably 4% to 6% by weight of the total polymeric composition and, finally, d) introducing into the polymerization slurry of c) ethylene or an ethylene/propylene mixture containing more than 80% by moles of ethylene, allowing such mixtures to polymerize at a temperature of from 60°C to 80°C and at a pressure lower than 10 kg/cm2 gauge.
14. The process of claim 13, wherein at least one of c) and d) are replaced by c' which consists in feeding into at least one of slurry of b) and c) ethylene continuously and propylene discontinuously to obtain during the propylene feeding a molar ratio of ethylene to propylene comprised between 60/40 and 85/15, and in the fed as a whole a molar ratio of at least 80/20 between the total amount of ethylene fed and the total amount of propylene fed; both monomers being polymerized at a temperature of from 60°C to 80°C and a pressure lower than 10 kg/cm2 gauge, until the resulting copolymer makes up 3% to 18%
by weight of the total composition.
by weight of the total composition.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT29436/74A IT1025699B (en) | 1974-11-14 | 1974-11-14 | PROCEDURE FOR PREPARATION OF POLYPROPYLENE COMPOSITIONS OF IMPACT RESISTANCE AT LOW TEMPERATURE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1050192A true CA1050192A (en) | 1979-03-06 |
Family
ID=11226992
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA239,318A Expired CA1050192A (en) | 1974-11-14 | 1975-11-10 | Process for preparing polypropylene compositions having high impact strength at low temperatures |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPS5171390A (en) |
| AT (1) | AT346578B (en) |
| BE (1) | BE835527A (en) |
| CA (1) | CA1050192A (en) |
| DE (1) | DE2550549A1 (en) |
| ES (1) | ES442577A1 (en) |
| FR (1) | FR2291220A1 (en) |
| GB (1) | GB1528136A (en) |
| IT (1) | IT1025699B (en) |
| NL (1) | NL7513084A (en) |
| NO (1) | NO753725L (en) |
| SE (1) | SE7512537L (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5247091A (en) * | 1975-10-13 | 1977-04-14 | Sumitomo Chem Co Ltd | Process for preparing block copolymers |
| JPS54139693A (en) * | 1978-04-21 | 1979-10-30 | Sumitomo Chem Co Ltd | Preparation of propylene-ethylene block copolymer |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5810415B2 (en) * | 1974-02-27 | 1983-02-25 | 三菱油化株式会社 | Fragile polypropylene |
-
1974
- 1974-11-14 IT IT29436/74A patent/IT1025699B/en active
-
1975
- 1975-11-07 NO NO753725A patent/NO753725L/no unknown
- 1975-11-07 SE SE7512537A patent/SE7512537L/en not_active Application Discontinuation
- 1975-11-07 NL NL7513084A patent/NL7513084A/en not_active Application Discontinuation
- 1975-11-10 CA CA239,318A patent/CA1050192A/en not_active Expired
- 1975-11-10 FR FR7534322A patent/FR2291220A1/en active Granted
- 1975-11-10 GB GB46367/75A patent/GB1528136A/en not_active Expired
- 1975-11-11 DE DE19752550549 patent/DE2550549A1/en not_active Withdrawn
- 1975-11-11 JP JP50134758A patent/JPS5171390A/en active Pending
- 1975-11-11 AT AT857375A patent/AT346578B/en active
- 1975-11-13 BE BE161828A patent/BE835527A/en unknown
- 1975-11-13 ES ES442577A patent/ES442577A1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| AT346578B (en) | 1978-11-10 |
| JPS5171390A (en) | 1976-06-21 |
| DE2550549A1 (en) | 1976-05-20 |
| IT1025699B (en) | 1978-08-30 |
| NL7513084A (en) | 1976-05-18 |
| ES442577A1 (en) | 1977-05-01 |
| GB1528136A (en) | 1978-10-11 |
| FR2291220B1 (en) | 1977-12-16 |
| ATA857375A (en) | 1978-03-15 |
| FR2291220A1 (en) | 1976-06-11 |
| NO753725L (en) | 1976-05-18 |
| SE7512537L (en) | 1976-05-17 |
| BE835527A (en) | 1976-05-13 |
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