DE2338888A1 - Polyethylene of controlled mol. wt. distribution - obtd using transitional metal catalysts activated by aluminium hydrocarbon cpds - Google Patents

Abstract

Prodn. of polyethylene with controlled mol. wt. distribution is carried out by polymerisation of ethylene, opt. in admixt. with propylene and/or butylene-(1), as well as in the presence of H2, and a catalyst comprising a mixt. of two transitional metal components A and B activated by an aluminium hydrocarbon cpd., the mol. ratio of A : B being 1 : 20 to 1 : 0.1, where A consists of chromium (III) acetylacetonate absorbed on silicic acid, and B consists of either (a) TiCl3 obtd. by organometallic reduction of TiCl4, or (b) liquid hydrocarbon-soluble mixts. of V and/or Ti cpds. reduced by an organometallic cpd. The mol. wt. distribution is wider, the larger the propn. of component A. The polymerisation is effected under the usual conditions for low pressure Ziegler polymerisation, e.g. pressures of 1-100 atm., pref. 10-50 atm., and temps. of 20-100 pref. 60-90 degrees C. The process yields polyethylene and copolymers with propylene and/or butylene which can be processed in high performance extruders to yield hollow articles, tubes, etc. having good stress-cract resistance, impact strength and stiffness.

Description

Dl α invention relates to a process for producing polyethylene sov; ie ylene and / or butylene (l) with ger.ielt within wide Gren-2-ene adjusted molecular weight distribution of a copolymer of predominantly ethylene and Pro2).

It is known that ethylene can be treated with catalysts made from transition metal compounds of IV. To VI. Subgroup of the periodic table and organometallic compounds from I. to III. Main group is polymerized at pressures below 100 atmospheres and temperatures between 20 and 120 ⁰ C in the gas phase or in a liquid hydrocarbon as a diluent, where appropriate molecular hydrogen is used to regulate the molecular weight. Mixtures of different transition metal compounds can also advantageously be used as the transition metal component of the catalysts of the Ziegler type. For example, different modifications of titanium trichloride are mixed with one another or compounds of trivalent titanium with reaction products of compounds of tetravalent titanium with solid compounds containing divalent metal are used. It is also known that mixtures of compounds of titanium and vanadium, for example titanium tetrachloride and vanadium oxychloride, can also be used for the production of catalysts

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use. As a particular advantage of this compared to the state of the art associated process is a high catalyst activity and / or a particular suitability of the polymers for the production of shaped bodies in the extrusion process. It is also known to use ethylene polymers with broad molecular weight distributions, as they are necessary for the melt fracture-free extrusion processing, thereby producing, that the polymerization is carried out in two or more process stages under different conditions in each case.

However, the processes belonging to the prior art are either technically very complex and therefore not very economical, or else only have little effect with regard to the desired properties of the polymers. According to a process that does not yet belong to the state of the art, a catalyst is used for the production of polyethylene with an extremely broad molecular weight distribution, which has been produced in the absence of moisture and molecular oxygen from chromium (III) acetylacetonate, silicic acid and triisobutylaluminum, 0.5 to 5 wt .- $ & Chrom- (HI) -acetylacetonEt applied to the silica or a silica-containing material and then reacted with triisobutylaluminum in molar ratios of aluminum to chromium compounds of 10: 1 to 100: 1. This process can be used to produce ethylene polymers with molecular _{non-uniformities, determined by the gel permeation chromatographic method, from U Gpc} about 35 to 100 and proportions <Mw / 5 of about 50 to 60% by weight. Such polymers do indeed have an unusual combination of excellent performance properties, such as melt fracture-free processability on extruders, practically complete sensitivity to stress corrosion cracking and at the same time excellent rigidity and hardness. On the other hand, however, the extremely high molecular uniformity has a disadvantageous effect on the shock resistance or tensile impact strength of the products. It happened

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therefore the task of finding a polymerization process that regulates the molecular inhomogeneity of the Poli'inerisate according to the respective application technology Requirements for the product properties made possible.

There has now been a process for the polymerization of ethylene, optionally in a mixture with propylene and / or butylene- (I), to form polymers with an arbitrarily adjusted molecular weight distribution found which does not have the disadvantages of the prior art methods. With a given Weight average molecular weight and the given density of the polymers are thus important in terms of application technology Properties such as melt fracture-free processability or surface smoothness, Stress cracking resistance and drop resistance of molded bodies largely depend on the molecular non-uniformity certainly. The progress of the new method according to the invention is that the property profile of the Polymers within the natural legal relationships and limits can be varied arbitrarily and continuously. So it is possible, for example, by setting a very high molecular inhomogeneity an excellent stress crack resistance, i.e. insensitivity to the action of wetting agents, but with only moderate tensile impact strength, i.e. low drop height of Hollow bodies, and vice versa, with extremely high tensile impact strength, only a product with moderate stress cracking resistance can be used getting produced. The new method according to the invention now enables, for example, those mentioned above Graduating product properties according to their context in any way. Furthermore, other product properties such as melt fracture-free processability, surface properties can be arbitrarily graded. When changing a Property in a desired manner, other properties inevitably change in an undesirable manner. The inventive Procedure now allows the setting of an optimal

B09807 / 0971 ~ ⁴ "

Compromise that meets the respective technical requirements the polymer best suits.

The invention therefore relates to a method for production of polyethylene with a specifically adjusted broad molecular weight distribution by polymerization of ethylene, optionally also as a mixture with propylene and / or butylene- (l) as well in the presence of molecular hydrogen, with catalysts of the Ziegler type, which is characterized in that as Catalyst is a mixture of two transition metal components A activated with an aluminum hydrocarbon compound and B is used in molar ratios of about 1:20 to about 1: 0.1, with component A being adsorbed on silica Chromium (III) acetylacetonate and component B from either by organometallic reduction of titanium tetrachloride produced titanium trichloride or from common organometallic Reduction of soluble in liquid hydrocarbons Mixtures of vanadium and / or titanium compounds obtained and optionally isolated insoluble reaction products and the molecular weight distribution all the same The larger the proportion of the transition metal component, the wider it is A is.

The inventive method enables the production of Polyethylene or copolymers of ethylene and propylene and / or butylene (l), which on extruders with high output to hollow bodies, pipes and the like with excellent finished part properties such as stress crack resistance, Tensile impact strength and rigidity, melt fracture-free processing, can be processed continuously or discontinuously carried out polymerization in one process stage or reactor.

The polymerization is carried out among those for the low-pressure polymerization according to Ziegler usual conditions such as

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Pressures from 1 atmosphere to 100 atmospheres, preferably 10 atmospheres to 50 atmospheres and temperatures between 20 ° and 100 ⁰ C, preferably between 60 ° and 90 ⁰ C. Depending on the selected molar ratio of the catalyst components A and B can be gelperineationschromatigraphisch certain inconsistencies of the polymers from about Vnpn − 1 ° to about U _G p _C = 100, the proportions <Mw / 5 being about 35 wt. -4> to about 60 wt.

The molecular non-uniformities are the wider, the more the proportion of component A in the catalyst mixture is greater. The production of component A takes place according to the German Patent application P 22 34 231.0. The production of the titanium trichloride used as component B is part of the status quo of the technique. The same applies to the production of the titanium-vanadium catalyst which can be used as component B.

Examples 1 and 2

The catalyst component A used for the polymerization became manufactured as follows:

To a warmed at 50 ⁰ C suspension of 1.2 kg of dried silica Ketjensilica (manufactured by Koninklijke Zwavelzuurfabrieken v / h Ketjen NV) F-5 in 30 1 of hexane was added with stirring within a 15.Minuten 50 ⁰ C warm solution of 24 , 7 g of chromium (IIl) acetylacetonate and 30 l of hexane are allowed to run in.

_{The catalyst component B 1} used for the polymerization was prepared as follows:

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To 3 liters of 4 m diethylaluminum chloride solution in hexane were added under stirring at 30 ⁰ C within 230 minutes, 3 liters of 2 m of titanium tetrachloride solution in hexane added. The filter residue was washed seven times with 250 ml of fresh hexane each time and then diluted to a concentration of 82 mg of atom titanium per liter.

The ethylene polymerization was carried out in a 2 liter steel autoclave as a 1 liter batch. 21.6 ml of the catalyst component A, containing 0.025 mg of atom of chromium, were diluted to a volume of 250 ml with hexane, to which 300 mg of triisobutylaluminum had been added. This suspension was ^{stirred at 25 °} C. for 20 minutes. At the same time, 750 ml of hexane, 250 mg of triisobutylaluminum diluted with 2 ml of hexane and the amount of catalyst _{component B 1} given in Table 1, calculated as mg of atom of titanium, were introduced into the autoclave under nitrogen. To the heated to 60 ⁰ C autoclave, the above-mentioned containing the chromium component suspension was added. Then the nitrogen was displaced by ethylene, hydrogen up to a pressure of 6.4 kp / cm

and ethylene up to a total pressure of 33.6 kp / cm. The contents of the autoclave were then ^{heated to 75 °} C. with stirring and were kept at for the duration of this experiment

kept this temperature. The pressure of 33.6 kp / cm was also kept constant by forcing in more ethylene. After one hour - calculated from the beginning of the ethylene supply, the polymerization was terminated by letting down the unreacted ethylene egg. The solid was filtered off and ^{dried in vacuo at 80 °} C. for 3 hours. Yield J 427 g. Further information on the polymer properties can be found in Table 1.

509807/0971

Correlation experiment A and B

Information on the comparative tests A and B are compiled in Table 1 above. The polymerization took place as in example 1.

Examples 3 to 6

The preparation of component A is described under Example 1. Component B ₂ was obtained in the following way:

1 mol of n-propyl titanate and 3 mol of vanadium oxytrichloride were diluted with 3.5 liters of hexane and then refluxed for 2 hours. After cooling, the solution was 8 moles of diethylaluminum chloride in 5 liters of hexane at 30 ⁰ C in the course of

Dosed for 2 hours. The precipitate formed after the reduction was filtered off, washed with hexane, resuspended and reduced to a concentration of 11.5 mgAtom Ti and V pro Liter diluted.

The polymerization was carried out as in Example 1. The amounts of catalyst used for components A and B ₂ are listed in Table 2.

Comparison experiment C and D

Comparative experiments C and D were carried out as in Example 3. Details can be found in Table 2.

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Table 1

at
game Cr / Ti (Mol
relationship Catal
torkompo
nent A
mgAtom
Cr Catal
torkompo
nent B ₁
mgAtom
Ti water
material
partial
printp
kp / cm Ethylene
partial
pressure
p
kp / cm yield
G MFI
(190/5)
g / 10min RSV
dl / g ^U GPC <Mw / 5 1 1: 5 0.025 0.125 6.4 26th 427 0.19 4.4 48 50 CVl 1: 10 0.025 0.25 6.4 26th 400 0.24 4.0 22nd 46 A ⁺ 1 ι 0 0.025 - 6.4 26th 165 <0, l 8.4 102 57 B ⁺ 0: 1 - 0.25 6.4 26th 372 <o.i 5.1 13th 43

cn σ co co ο • «4

O CD

2J MFI (190/5)
RSV

^U GPC

Mw

Melt index according to DIN 53 735

reduced specific viscosity

Molecular non-uniformity determined by gel chromatography

Weight average molecular weight

⁺ Comparison tests

vo

GO GO CO OO OO CO

Table 2

ο co —J

at Cr / Ti (Mol . 1 catalyst catalyst yield RSV U GPC O-ν / 5 Vinvlfrrupr> en *) i game relationship ) 1 component A
mgAtom Cr component B ₂ ,
mgAtom (Ti-tV) G dl / g IC ^ y O \ ^ ^>"1
I. 3 1 ; ί 1 0.013 0.013 363 6.5 17th 36 0.16 4th 2: ; 1
: O 0.013 0.0064 305 7.0 41 0.16 5 4 i ί 1 0.013 0.0032 ISl t ? ο ICO 40 0.59 60S 6th
C ⁺ 8th .
1 0.026 ² ^ 0.0032 399
295 6.9
l 7.6 ⁵ / * ■ "·
56 1. "I.
1.8 OO
O D ⁺ O - 0.013 244 I 6.8 34 0.03

2)

Vinyl groups per 1000 carbon atoms: values were determined by infrared analysis

In comparison to Example 5, the mixture of the chromium component, triisobutylaluminum and solvent made up outside the reactor was doubled. The suspension volume initially placed in the reactor was reduced so that, after the components had combined , as in Example 5, a total volume of 1 liter was obtained.

Comparative experiments

ro co

co co co OO

example J

Total duration of the experiment: 74 h
Evaluation period: 12 h

In a mante Ige-cooled agitator was operated at a total pressure of 36 kp / cra and a temperature of 85 ⁰ C continuously polymerized ethylene. To regulate the molecular weight, a hydrogen content of approx. 22 V0I .- / 0 was set in the gas space of the reaction vessel. At a liquid level in the reaction vessel of 300 l, 150 l of the catalyst suspended in was metered in every hour. The liquid level in the reaction vessel was regulated with a Co radiation barrier. The polymer suspension regulated from the reaction vessel was let down into a downstream stirrer vessel. The pulverulent polymer was then separated off on a centrifuge and then ^{dried at about 00 °} C. in a vacuum.

A mixture of two catalysts was used as the polymerization catalyst: 20% by weight of the above-described catalyst A and 80% by weight of the catalyst B ₁ described in Example 1. The two catalysts were diluted in separate templates and conveyed from there with 2 pumps via a common inlet tube into the reaction vessel.

Receipt 1: 112.5 1 catalyst suspension / h, containing

1.6 g of catalyst B ₁ and 11.25 g of triisobutyl aluminum

Template 2; 37.5 1 catalyst suspension / h, containing 0.4 g of chromium (III) acetylacetonate to 21.38 g

SiO ₂ and
9.25 grams of triisobutyl aluminum

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In an experiment carried out in this way, the total of one Had a running time of 74 h, were during an evaluation period after 12 h the following results are achieved:

Hourly yield: 19.5 kg PE catalyst consumption: Chromium (III) acetyl

acetonate: 20.5 mg / kg PE = 4.5 ppm Cr ₂ O ₅ in the polymer

TiCl ₃ : 82 mg / kg PE * 42 ppm TiO ₂ in the polymer

Triisobutylaluminium: 1,050 mg / kg PE

A test product mixed from individual batches had the following properties:

mean molecular weight M ₇ . - 209,000 density 0.955 g / cm ⁵ molecular nonuniformity = 22.2 Share <Mw / 5 53.4 f Tensile impact strength =
(according to DIH 53 448) 800 cmkp / cm critical height of fall * at 20 ⁰ C = 2.34 m Tension crack resistance
at 70 ⁰ C
(according to ASTM D 1693 - 70) 63 h

The catalyst consumption was so low that the polymers were processed further without any catalyst leaching can be.

^Ä The critical drop height specified is the height at which 50 $ s of the tested 10 l filter filled with water break when it hits a solid surface.

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BelST) IcI 8

Total duration of the experiment; 38 II

Period of evaluation: 12 II

In the same apparatus v / iο in Example 7 was at almost an ethene-propene copolyinerizate continuously under identical conditions manufactured.

Compared to Example 7, the ratio of the catalysts was changed to 70% by weight of catalyst A and 50% by weight of catalyst B ₁ . In addition, the hydrogen content in the gas space of the reaction vessel was reduced to approx. 15% by volume.

The Gev i chtsverhältnis the hourly metered amounts of olefins was 2: 100 (= 2 propene, ethene = 100).

The following amounts of catalyst were diluted in the two receivers.

Receipt 1 : 112.5 1 catalyst suspension / h, containing

1,1 g of catalyst B ₁ and 11.25 g of triisobutyl aluminum

Template 2: 37.5 1 Katalj ßatorsuspension ^r / h, containing 0.47 g of chromium (III) acetylacetonate in 22.8 g

SiO ₂ and
10.75 grams of triisobutyl aluminum

The average hourly yield was over one Period of 12 h 18.7 kg PE. The following catalyst consumption can be calculated from this:

Chromium (III) acetylacetonate = 25.2 rag / kg PE = 5.5 ppm Cr ₂ O ₃ jm

Polymers

TiCl ₅₅ = 58.9 mg / kg PE ^ 31 ppm TiO ₂ im

Polymers

Triisobutylaluminum = 1,180 mg / kg PE

A mixture of the polymer compositions had the following Property picture:

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233R088

ui Micros Holekulargov / icht M Üichti '

in: j UifcuLore- Une.inpoliteness An to LL <l: v // f3

in.Il I <-i ;, -Uf.ZJhif'ko i t ()

critical *. Case:; j ir / at PO ° C

. ";! ' i iu; be. ^f ; bund ι ^ Uο ί Ι (nach /.Viii D 169 '; - Yi))

L93 UOO 4th "L 0, 20, c " 1. o! io " 1: 1 2, ti 34

Hoi;: pi ol 9

Ue;.; HüLlaiier des Vürsuche.s: 863 h Evaluation period: 12 h

In the apparatus from Example 7, ethylene was polymerized continuously. The total pressure was 36 kgf / cm, the Reaktlonsteuiperatur hours 85 ⁰ C and the average residence time in the reaction vessel. 4 To regulate the molecular weight, a hydrogen content of approx. 21% by volume was set in the gas space of the reactor. The weight ratio of the two catalyst components A: B ₂ was 60:40. The catalysts were diluted in separate receivers.

Receipt 1: 3Y, 5 1 catalyst suspension / h, containing 0.332 g of catalyst B ₂ and 3.75 g of triisobutylaluminum

Receipt 2: 37.5 1 catalyst suspension / h, containing

0.5 g chromium (III) acetylacetonate on 24.2 g SiO ₂ 11.75 g trilsobutyl aluminum

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BATH

509807/0971

The above catalyst mon & s was used for 12 hours Durclissolinitblichen yield of IB, 7 kg PE / h reached. the The catalyst consumption was:

Chrow (tEl) acelylacotmiat - 26.8 mg / kg PPJ '= 5.0 ppm Cr ₂ C) _; . "ir:

Catalyst Ii ₂ = 17.0 mg / kg PE = 6 ppm V _{? £} 0) im

Polyn-.Ίοη

TriiiiobutylaLuininiurn - 770 mg / kg PB

A test product manufactured in this way had the following properties:

mean molecular weight M _y = 193,000

Density s = 0.953 g / cm ⁵

molecular non-uniformity = 21.3

Proportion <Mw / 5 = $ 48.3

Tensile impact strength = 1,130 cmkp / cm "

(according to DlN 53 448)

critical height of fall * at 20 ⁰ C = 2.66 m resistance to stress cracking

at 70 ⁰ C = 71 h

(according to ASTM D 1693 - 70)

Example 10

Total duration of the experiment: 108 h. Period of evaluation: 12 h

An ethene-propene copolymer was produced under the same test conditions as in Example 9. The weight ratio the amount of olefin metered in per hour was 1: 100 (propene = 1, ethene = 100).

The following amounts of catalyst were in two separate templates diluted.

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r / a-

JiJL 37.5 1 catalyst suspension / h containing

0.268 g of catalyst B ₂ and 3.75 g of triisobutyl aluminum

2: 37.5 containing 1 catalysis board / h

0.4 g chromium (III) acetylacetonate on 19.4 [beta] SiO ₂ and 9.0 g triisobutylaluminum

With the quantities of catalyst, an hour- " yield of 17.9 kg of PE obtained. This resulted in the following catalyst consumption:

Chromium (III) acetylacetonate = 22.3 mg / kg PE = 4.8 ppm Cr ₂ O ₃ im

Polymers

Catalyst B ₂ = 14.9 mg / kg PE £ 5.1 ppm V ₂ 0 _e im

Polymers

Triisobutyl aluminum = 710 mg / kg PE

A product manufactured in this way showed the following properties:

mean molecular weight M ^ = density

molecular nonuniformity =

ShareMw / 5

Tensile impact strength - (according to DIN 53 448).

critical height of fall * at 20 ⁰ C =

Tension crack resistance

at 70 ° C

(according to ASTM D 1693 - 70)

162 000 g / cnr 0.950 14.2 41.4 pounds cmkp / cm 1 .200 m 3.14 H 41

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Claims (1)

Process for the production of polyethylene with a specifically adjusted broad Holekulargevrichts distribution by polymerization of ethylene, optionally also in a mixture with propylene and / or butylene- (l) and in the presence of molecular hydrogen, with catalysts of the Ziegler type, because d \ ir ch in that as a catalyst a mixture of two activated with an aluminum hydrocarbon compound transition metal components a and B in mole ratios of etv, ^r a 1: 20 to about 1: is used 0.1, wherein component a consists of silica adsorbed chromium (III) acetylacetonate and component B consists of titanium trichloride produced either by organometallic reduction of titanium tetrachloride or of insoluble reaction products obtained and optionally isolated by joint organometallic reduction of mixtures of vanadium and / or titanium compounds which are soluble in liquid hydrocarbons, and the molecular weight distribution is so b The greater the proportion of the transition metal component A, the greater it is. 5 0 3 P 0 "' 9 7