FR2464966A1 - PROCESS FOR PRODUCING POLYETHYLENE - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR THE PRODUCTION OF POLYETHYLENE. THIS PROCESS CONSISTS OF CONDUCTING THE POLYMERIZATION IN THE PRESENCE OF AN ALCOHOL AND IN THE PRESENCE OF A POLYMERIZATION CATALYST PREPARED FROM: A. A SOLID CATALYTIC COMPONENT CONTAINING AT LEAST TITANIUM, MAGNESIUM AND CHLORINE; B. A TRIALKYLALUMINUM OF FORMULA RAL, IN WHICH R IS AN ALKYL OR CYCLOALKYL GROUP; AND C. AN ALUMINUM COMPOUND CONTAINING CHLORINE OF THE RALCL FORMULA, IN WHICH R IS AN ALKYL OR CYCLOALKYL GROUP, AND N HAS A VALUE OF 1 TO 2.

Description

The present invention relates to a production process

  polyethylene, and more particularly an efficient method of producing polyethylene having a broad molecular weight distribution, wherein a particular catalyst is used and the polymerization will be carried out

  in the presence of an alcohol in the reaction system.

  In general, polyethylene used in the production of molded articles such as bottles, cable sheaths and

  ultra-thin films, must be able to withstand

  plastic moldings and must be easily molded into a predetermined shape. Therefore, it is necessary to use a polyethylene having a

  broad molecular weight distribution.

  The process described in the Japanese patent application

  48584/1973 or 7488/1979 is a method by which. we pro-

  polyethylene with a broad molecular weight distribution

  and having excellent moldability, etc.

  In the process of Patent Application No. 48584, a first component of the catalyst is prepared by reacting a mineral magnesium compound with a mineral compound of a metal selected from groups II to VIII of the Periodic Table and a titanium halide thereof. presence of an electron donor. However, since the preparation of this catalyst is difficult and requires a lot of effort, the process using such a catalyst lacks reproducibility. In addition, the method has the drawback of not having a weight distribution

  Molecular polyethylene produced sufficiently broad.

  The method of patent application 7488 is complex and inefficient and requires a very expensive installation because

  the polymerization reaction is carried out in two stages.

  Therefore, the invention proposes to provide a process that overcomes the aforementioned drawbacks of conventional techniques and to develop an efficient method of producing polyethylene having a broad molecular weight distribution. The Applicant has discovered that if the polymerization reaction is conducted in the presence of a particular catalyst and in the presence of an alcohol, a polyethylene having a broad

molecular weight distribution.

  The present invention provides a method of

  polyethylene production, characterized in that the reaction

  The polymerization process is conducted in the presence of an alcohol and in the presence of a catalyst prepared from (A) a solid catalyst component containing at least titanium, magnesium and chlorine; (B) a trialkylaluminum having the following general formula: wherein R represents an alkyl or cycloalkyl group having from 1 to 12 carbon atoms; and (C) a chlorine-containing aluminum compound of the following general formula: R AlCl n 3-n wherein R 2 is alkyl or cycloalkyl having 1 to 12 carbon atoms, and n is a number of

1 to 2.

  The catalyst used in the present invention is

  prepared from the above components (A), (B) and (C).

  Component (A), namely the solid catalyst component containing at least titanium, magnesium and chlorine,

  encompasses various types of compounds without particular limitations

  -border. For example, component (A) may be obtained by reaction of a magnesium compound such as a magnesium dialcoholate having the following general formula Mg (OR4) 2 wherein R4 is alkyl, alkenyl, aryl, cycloalkyl, straight or branched chain arylalkyl or alkylaryl having from 1 to 20, preferably from 1 to 8 carbon atoms, with a chlorine-containing titanium compound having the following general formula: wherein R5 represents a alkyl or aryl group having

  from 1 to 10 carbon atoms, and m is a number from 1 to 4.

  Preferred examples of the magnesium dialcoholate of the general formula Mg (OR) 2 include dimethylate, diethylate, dipropylate, dibutylate, dicyclohexylate, dibenzylate, etc., magnesium. Examples of the chlorine-containing titanium compounds of the general formula ClmTi (OR5) 4m include, for example, titanium tetrachloride (TiCl4), trichloromethoxytitanium (CH3OTiCl3), trichloroethoxytitanium (C2H5OTiCl3), trichloropropoxytitanium (C3H7OTlCl3), dichlorodiethoxytitanium ((C2H50) 2 TiCl2), monochlorotriethoxytitanium ((C2H50) 3TiCl), etc. Among these compounds, compounds having a high content are preferred.

  in chlorine, and in particular titanium tetrachloride.

  Although the solid catalyst component (A) can be prepared by reacting the magnesium dialcoholate with the chlorine-containing titanium compound as described above, it is preferably prepared by reacting the chlorine-containing titanium compound, described above. above, with a magnesium compound which has been obtained previously by reaction of the magnesium alkoxide described above

  with silicon tetrachloride (SiC14), etc.

  The composition of the component (A) (catalytic component

  lytic solid) obtained by one of the processes described above.

  can vary over a wide range and is limited only by the fact that it contains at least titanium, magnesium and chlorine. Preferably, the titanium atom content of the polymerization reaction system in

  suspension is from 0.001 to 10 millimoles per liter, in par-

  especially from 0.005 to 1 millimole per liter.

  Representative examples of component (B) are

  that is, trialkylaluminum of the general formula R13A1, include trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum,

trioctylaluminium, etc ...

  Representative examples of the component (C), i.e., the chlorine-containing aluminum compound of the general formula R 2nAlCl 3, include diethylaluminum monochloride, diisopropylaluminum monochloride, diisobutylaluminum monochloride, sodium monochloride and the like. dioctylaluminum, ethylaluminum dichloride,

  isopropylaluminum dichloride, etc.

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  In the preparation of the catalyst, components (B) and (C) described above may be added separately or in admixture to component (A). The total amount of components (B) and (C) is preferably from 5 to 200 (molar ratio) and more preferably from 20 to 100 (molar ratio), relative to the titanium atoms of component (A). The mixing ratio of components (B) and (C) is not very limited, but the ratio of component (B) to component (C) should generally be in the range of 20 to 1/20,

  preferably from 5 to 1/5 (molar ratio).

  It is necessary, in the process of this

  invention, that the catalyst prepared from the

  (A), (B) and (C) above is used and that an alcohol

  is present in the polymerization reaction system.

  If there is no alcohol in the reaction system, the molecular weight distribution of the polyethylene can not be widened and the purpose of the present invention

can not be reached.

  The amount of the alcohol that must be present in the reaction system is determined according to the

  desired molecular weight distribution of the polyethylene.

  It can be determined empirically, and it should generally be from 0.05 to 10 (molar ratio), preferably from 0.1 to 5 (molar ratio), based on the total amount of components (B) and (C) . When the molar ratio is less than the above range, there is no increase in the melt flow rate (T.E.), whereas when the molar ratio is above

  this range, the activity of the catalyst is greatly diminished.

  The alcohol may be previously added to component (A) above or mixed with component (B) and / or

  component (C). Alternatively, the alcohol can be added directly

  reaction system during the polymerisation of

  instead of being ethylene in the preparation of

lyst.

  The alcohol that is possibly present in the

  The reaction system has no particular limitations.

  It is an alcohol of the general formula R 3 OH wherein R 3 represents an alkyl, cycloalkyl or aralkyl group having from 1 to 20 carbon atoms. As alcohols, mention may be made, for example, of an aliphatic alcohol such as ethanol,

  n-propanol, isopropanol, n-butanol, isobutanol, sec.-

  butanol, tert-butanol, 2-ethylhexanol, 1-dodecanol, etc.,

  a cycloaliphatic alcohol such as cyclohexanol, etc.

  or an aralkyl alcohol such as benzyl alcohol, etc. When ethylene is polymerized according to the process of the present invention, the catalyst prepared from components (A), (B) and (C) above and the alcohol are added to the reaction system and then the ethylene is

  introduced into the system. The procedure and the conditions

  polymerization conditions are not limited. It is possible to use a polymerization in solution, in suspension,

  or in the vapor phase and carry it out continuously or in

  continued. As medium for the reaction system, an inert solvent such as butane, pentane, n-hexane, cyclohexane, heptane, benzene, toluene, etc. is preferred. Polyethylene can be obtained by reacting ethylene at an ethylene pressure of between 2 and 50 bar, preferably between 5 and 20 bar, at reaction temperatures ranging between 20 and 2000C, preferably between 50 and 1500C for 10 minutes to 5 hours, preferably 30 minutes to 3 hours. The molecular weight adjustment during the polymerization can be carried out

  by a conventional method, for example by adding hy-

drogen, etc ...

  The method of the present invention provides

  polyethylene which is a homopolymer of ethylene and also

  a copolymer of ethylene and an alpha-olefin such as

  that propylene, butene-1, 4-methyl-pentene, etc.

  Through the use of the catalyst described above and the use of the alcohol, the activity of the catalyst is very intense and a small amount of the catalyst is sufficiently effective to eliminate the catalyst removal step. . The polyethylene produced has a high apparent density, a suitable particle size and

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  a very low content of fine powder, as well as a wide range of molecular weight distribution. Consequently,

  the polyethylene product has a very good

  molding study and excellent physical properties.

  Since the molecular weight distribution of the obtained polyethylene is adjusted to the desired range by a judicious choice of catalyst mixing ratio,

  the amount of added alcohol, polymeric conditions,

  tion, etc., the process of the present invention is

very effective.

  Representative examples of the present invention

  The following are given in which all the processes are conducted under an argon atmosphere. The molecular weight distribution is estimated by the melt flow rate (MT), which is the ratio of melt index at 21.6 Kg to melt index.

under a load of 2.16 kg.

Example 1

  Preparation of a solid catalyst component In a 500 ml capacity four-neck flask, 150 ml of anhydrous hexane, 10 g (88 g)

  millimoles) of magnesium diethylate and 3.7 g (22 milligrams

  moles) of silicon tetrachloride. After adding 2.0 g (33 millimoles) of isopropyl alcohol dropwise at 20C over a period of 1 hour, the temperature of the mixture is raised and the reaction is carried out at 680C for 2 hours. 42 g (220 mmol) of titanium tetrachloride are then added dropwise and the reaction is carried out under reflux for 3 hours. At the end of the reaction, the reaction mixture is cooled to room temperature and allowed to stand. The supernatant liquid is separated and added to 250 ml of anhydrous hexane and the mixture is allowed to stand after stirring. The supernatant liquid is separated. This cycle of operations is repeated five times, so as to obtain a suspension of the catalyst. The amount of titanium in the solid catalyst is 62 mg of Ti per gram of magnesium diethylate,

  as determined by colorimetry.

  In a 1 liter stainless steel autoclave, 400 millimoles of anhydrous hexane, 1.5 millimoles of triethylaluminum (TEA) and 1.5 millimoles of diethylaluminum chloride (DEAC) were introduced into a 1 liter stainless steel autoclave. 0.0025 milligrams (calculated as Ti) of the solid catalyst component and 1.0 millimole of ethanol are then added as alcohol and heated.

  the mixture at 800C. After introduction of 1 bar of hydro-

  gene and 7 bars of ethylene, ethylene is polymerized

  1 hour while maintaining the above pressure by continuous addition of additional ethylene. 128.8 g of polyethylene are thus obtained. The activity of the catalyst is 1076 kg of polyethylene per gram of titanium atom per hour. The product polyethylene has a high bulk density of 0.33, a melt index (IF2.16) of 0.075, a T.E. of 44 and a lower fine powder content.

at 105> 5.3% by weight.

  Comparative Example 1 Ethylene was polymerized under the same conditions as in Example 1 except that ethanol was not added. There is thus obtained 117.3 g of polyethylene. The activity of the catalyst is 980 kg of polyethylene per gram of titanium atom per hour. The resulting polyethylene has a bulk density of 0.29, a melt index (IF2.16) of 0.079 and a T.E. of 33. These characteristics have lower values than those for the product.

  of Example 1 in which ethanol is added.

  Examples 2 to 13 and Comparative Example 2 Ethylene was polymerized using the

  solid catalyst component of Example 1 and in

  polymerization conditions shown in Table 1.

  The results obtained are also shown in Table 1.

  polymerization is conducted at 800C for 1 hour.

he

BOARD!

TEA

No.

mole) t!

At DEAC

(milli-

mole) Alcohol Name "'Quantity

Nm (milli-

mole) ethanol 015

vI "t iso ..

propanol "t" t-butanol

i, 2-ethyl-

hexanol

. cyclohexane

hexanol

", 1-dodec

canol 1.5 1.0 Ti

(milli-

mole) l, If 0f005 Pressure (bar)

Ethy- Hydro-

  Gene Gene It Tl Yield Poly-Activated Ethylene * (g)

1 15010

108t4

6) 5,115

It fi

010025 7 1

10 01010 615 115 121.4

Physical properties

polyethylene

Density 'F T.2.

pparen-.2,16 e 0,082 0,018 0,020

323 0.29 0.10

717 0132 0.088

0131 0.018 76

240 0/28 0O20 34

"9"

"10 0, (

"11" 2

t he there he

"12"

"13"

  Example om-t! For example, the amount of ethanol is 1.0

2-elthyl-

  hexanol 110 cyclo- 110 hexanol t-butanol 110

0) 0025

0. 010

0.010 -

- - 0.010

6.7

"18015

113 6414

3 14118

2 190r6 2 57i6

6 2

  *: Activity: Quantity of polyethylene produced per gram of titanium atom per hour (unit: kilogram)

Example 2

i 4 i 5

"6

He 7

"8

  o 0.29 0.25 0.31 0.36 0.037 0.53 r ', 0%

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Example 14

  Preparation of a solid catalytic component

  A small amount of about 40 milliliters is mixed

  liters) of ethanol with a mixture of 33.7 g (91 millimoles) of MgCl 2. 6C2H5H prepared from anhydrous magnesium chloride (dried at 1500C under reduced pressure for hours) and ethanol with 10.4 g (91 millimoles) of Mg (OC2H5) 2 and heated at 160 ° C under reduced pressure for 4 hours. hours. The solid thus obtained is milled to give a starting support. A suspension of 5 g of the support obtained in 100 ml of hexane is mixed with

  2.9 g of isopropanol and reacted at 700 ° C. for 1 hour.

  After adding dropwise 23 g of TiCl4 at 700 ° C. over a period of one hour, the reaction is carried out at 700 ° C.

  during 3 hours. After cooling the reaction mixture

  at room temperature, remove the excess liquid

  swimming and washed with 150 ml of hexane. The washing is repeated until no more Cl ions are detected in hexane, and finally 300 ml of hexane are added to obtain a suspension of the catalyst. The amount of titanium is

285 mg of Ti per gram of support.

  Polymerization of ethylene 400 ml of anhydrous hexane, 1.5 millimoles of TEA, 1.5 millimoles of DEAC and 0.005 millimoles of the solid catalyst (calculated as Ti) are introduced into a one-liter autoclave. . Then 1.0 millimole of ethanol is added and the mixture is heated to 80C. After introducing

  1 bar of hydrogen and 1 bar of ethylene, the poly-

  merit for 1 hour while maintaining pressure

  ethylene. 139.5 g of polyethylene are thus obtained.

  The catalyst activity is 581 kg of polyethylene

  produced per gram of titanium atom per hour. The poly-

  produced ethylene has a melt index (IF2,16) of 0.18,

  a T.E. of 41 and a bulk density of 0.33.

  When the polymerization is carried out under the same conditions as those described in the preceding paragraph, except the addition of ethanol, 147.3 g of polyethylene having a melt index (IF 2, 16) are obtained

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0.16 and a T.E. of 31.

Example 15

  Ethylene is polymerized under the same conditions.

  than those described in Example 14, except that 1.5 millimole of ethyl aluminum dichloride was used instead of DEAC. 35.3 g of polyethylene are thus obtained. The activity of the catalyst is 147 kg of polyethylene obtained per gram of titanium atom per hour. The product has a melt index (IF2,16) of 0.077, a T.E. of 49

and a bulk density of 0.27.

  When the polymerization is carried out under the same conditions as those described in the preceding paragraph, except that no ethanol is added, 51.0 g of polyethylene having a melt index (IF'16) of

0.090 and a T.E. of 33.

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Claims (14)

R E V E N D I C AT IO N S CLAIMS____   A process for producing polyethylene comprising polymerizing ethylene in the presence of an ethylene polymerization catalyst, the process being characterized in that it comprises: (a) conducting the polymerization in the presence of a alcohol; and   (b) using a polymerization catalyst comprising   (A) a solid catalyst component containing at least titanium, magnesium and chlorine; (B) a trialkylaluminum of formula R 1Al 1 3 wherein R is an alkyl or cycloalkyl group having 1 to 12 carbon atoms; and (C) a chlorine-containing aluminum compound of the formula R AlCl n 3-n wherein R2 is an alkyl or cycloalkyl group having   from 1 to 12 carbon atoms, and n is a number from 1 to 2.   2. Method according to claim 1, characterized in that the alcohol is present at a ratio of 0.05 to 10 with respect to the total amount of the components (B) and (C) present.   3. Method according to claim 1 or 2, characterized in that the amount of titanium in the polymerization catalyst is between 0.001 and 10 millimoles   per liter of the content of the polymer reaction mixture   authorization. 4. Method according to claim 3, characterized in that the total amount of components (B) and (C) is   between 5 and 200 moles per titanium atom of component (A).   5. Process according to claim 1 or 4, characterized in that the alcohol has the formula R OH, in which R is an alkyl, cycloalkyl or aralkyl group having from 1 to 20 carbon atoms.   6. Method according to claim 4, characterized in that the ratio of component (B) to component (C) is between 20: 1 and 1:20.   7. Method according to claim 5, characterized in that the alcohol is present at a molar ratio of between 0.1 and 5 relative to the total amount of the components (B) and (C), the ratio of said components between 5: 1 and 1: 5.   8. Process according to Claim 7, characterized in that the ethylene is polymerized at an ethylene pressure of between 2 and 50 bar and at a reaction temperature of between 20 and 2000 ° C. for approximately 10 minutes to approximately one hour. 9. Process according to claim 8, characterized in that the amount of titanium contained in the polymerization catalyst is between 0.005 and 1 millimole per liter of the content of the polymerization reaction system, the total amount of the components (B) and ( C) being between 20 and 100 moles per atom of titanium contained in the component (A).   10. Process according to claim 4 or 9,   in that SiCI4 is included in the components comprising the component (A).   11. Process according to Claim 1, characterized in that the ethylene is polymerized at an ethylene pressure of between 2 and 50 bar and at a reaction temperature of between 20 and 2000 ° C. for approximately minutes and 5 hours.   12. Process according to claim 2, characterized in that the amount of titanium in the polymerization catalyst is between 0.005 and 1 millimole per liter of the content of the polymerization reaction system, the total amount of the components (B) and ( C) being between 20 and moles per atom of titanium contained in the component (A).   13. Process according to claim 1, characterized in that the solid catalyst component containing at least   less titanium, magnesium and chlorine in the catalytic   The polymerization group is obtained by reacting a magnesium dialcoholate of formula Mg (OR) 2 in which R is an alkyl, alkenyl, aryl, cycloalkyl, arylalkyl or alkylaryl group having from 1 to 20 carbon atoms, with a titanium compound. containing chlorine of formula: ClmTi (OR) m 4-m wherein R is an alkyl or aryl group of 1 to 10   carbon atoms, and m is a number of 1 to 4.   14. The method of claim 13, characterized in that the magnesium dialcoholate is magnesium diethylate. nce15. Process according to claim 13, characterized in that the titanium compound containing chlorine is the titanium tetrachloride.