Method for the production of low density copolymers of ethylene

In producing a low density polyethylene by a slurry copolymerization of ethylene and an .alpha.-olefin with use of a catalyst consisting of a magnesium compound-supported titanium and/or vanadium compound and an organoaluminum compound, a certain amount of ethylene is subject to a pre-polymerization in the presence of said catalyst prior to the copolymerization. Successively, the slurry copolymerization of ethylene and an .alpha.-olefin is effected in a low-boiling diluent to obtain a low density polyethylene of 0.925-0.950 in density, covering various grades in a wide range.

BACKGROUND OF THE INVENTION 
This invention relates to a method for the production of a low density 
polyethylene by a slurry copolymerization of ethylene and an 
.alpha.-olefin. 
It is well-known in the art that polyethylene is produced by effecting a 
slurry polymerization in the presence of such hydrocarbons as hexane and 
heptane at temperatures of not more than 100.degree. C., at which the 
resulting polymer is not dissolved, or by effecting a solution 
polymerization at temperatures of more than 100.degree. C., usually 
130.degree. C. or more, at which the resulting polymer is dissolved. 
Hereinafter, the former is referred to as a slurry process and the latter 
as a solution process. 
Various grades of polyethylene have been produced in a commercial scale by 
controlling the molecular weight and density of a polymer in accordance 
with its uses. It has, however, been impossible to provide polyethylene 
covering various grades in a wide range by the slurry process alone or the 
solution process alone. 
As reported in, for example, Chemical Economy & Engineering Review, 7, 
24-40 (1975), the above two processes are used properly depending on the 
desired grades. 
The relation between grades which are defined by the density and melt index 
of polyethylene and the production process therefor is summarized from the 
abovementioned literature as shown in Table 1. 
Table 1 
______________________________________ 
Melt Index 
More than Less than 
Density, g/ml 
1.0 1.0-0.1 0.1 
______________________________________ 
Slurry Slurry 
process process Slurry 
0.945- 0.970 process 
Solution Solution 
process process 
Less than Solution Solution Impossible 
0.945 process process to produce 
______________________________________ 
It is well-known that melt index of polyethylene can be controlled 
depending on polymerization conditions and amount of a molecular weight 
modifier (for example, hydrogen) used in the polymerization, and that 
density of polyethylene can be controlled by copolymerizing ethylene with 
an .alpha.-olefin. 
In the production of a high density polyethylene (higher than 0.945 g/ml) 
by the slurry process, the resulting polymer is insoluble in a 
polymerization solvent and therefore, the viscosity of a polymerization 
system is not directly affected by the molecular weight of a polymer. 
Accordingly, polymers of from higher molecular weight (lower melt index) 
to lower molecular weight (higher melt index) can be obtained. However, in 
the event of producing a low density polyethylene by the slurry process 
through a copolymerization of ethylene with an .alpha.-olefin, there are 
many troubles that the viscosity of a polymerization system increases due 
to the formation of polymers soluble in the polymerization solvent and the 
swelling of the resulting polymer results in the lowering of bulk density 
and the stickiness of filter cakes. 
Under such troubles, it is very difficult to conduct the production in 
commercial scale conveniently. Therefore, the grades of polyethylene which 
can be produced by the conventional slurry process are limited to those 
having a density of 0.945-0.970 g/ml and a melt index of 0.01-40. In 
effect, the so-called, Ziegler method's polyethylene which is mainly 
produced by the slurry process is named a high density polyethylene. 
In the refining of a polymer containing slurry obtained in the slurry 
process with use of the known catalyst consisting of titanium trichloride 
and an organoaluminum compound, the after-treatment of decomposing the 
catalyst and then removing it by washing requires a long time, and during 
the time the viscosity of the polymer slurry increases and the bulk 
density of the polymer lowers. Thus, the use of supported catalysts has 
been proposed to obtain the polymer slurry of a good property, having no 
need of the complicated after-treatment. For example, US Pat. No. 
3,888,835 discloses a process for the polymerization of ethylene, in which 
a high activity catalyst having a titanium compound supported with a 
magnesium compound is used and such a low-boiling hydrocarbon as butane is 
used as a diluent for polymerization. 
However, when this process applies to the production of the low density 
polyethylene having a density of 0.935 g/ml or less through 
copolymerization of ethylene with an .alpha.-olefin, the resulting polymer 
is lowered in bulk density and it is difficult to obtain the polymer 
slurry of a good property. The lowering of bulk density brings about 
troubles in handling of the slurry, such as stirring, transferring, 
filtrating, drying and storing. For example, if the resulting polymer is 
reduced in bulk density in the polymerization step, the formation of bulky 
polymers results in insufficient agitation and accordingly, in lowering of 
the diffusion velocity of ethylene so that the apparent polymerization 
velocity is extremely reduced in spite of the catalytic activity being 
still sustained. Also, since the bulky polymers adsorb the solvent used, 
the pump conveyance and filtration of the slurry can not efficiently be 
conducted. For avoiding such troubles, the polymer slurry must be diluted 
with a large amount of solvent and as a result, contains such as a 
polymerization vessel and a storing vessel and installations for the 
recovery step of the solvent used and for the refining step are run on an 
extensive scale which is extremely disadvantageous economically. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide a method for the production of a 
low density polyethylene of 0.925-0.950 g/ml in density, covering a melt 
index in a wide range by the slurry process. 
Another object of this invention is to provide a method for the production 
of the low density polyethylene by copolymerization of ethylene with an 
.alpha.-olefin, having substantially the same order in bulk density as one 
of an ethylene homopolymer obtained by the slurry process. 
A further object of this invention is to provide a low density polyethylene 
slurry having a good property and having no need of the complicated 
after-treatment. 
A still further object of this invention is to provide the low density 
polyethylene of 0.925-0.950 g/ml in density and of less than 0.1 in melt 
index. 
In accordance with this invention, there is provided a method for the 
production of the low density polyethylene of 0.925-0.950 g/ml in density 
by copolymerizing ethylene and an .alpha.-olefin in the slurry process, 
which comprises: 
(1) using a catalyst consisting of (A) titanium and/or vanadium compounds 
supported with a magnesium compound and (B) an organoaluminum compound, 
(2) subjecting ethylene to a pre-polymerization in a liquid diluent in the 
presence of said catalyst prior to the copolymerization, the amount of 
ethylene to be pre-polymerized being more than 50 g per 1.0 g of said 
catalyst component (A) and not more than 20% by weight of the entire 
amount of the ethylene and .alpha.-olefin monomers to be polymerized, and 
(3) successively, conducting the copolymerization of ethylene and an 
.alpha.-olefin at temperatures of not higher than 100.degree. C. in the 
presence of a low-boiling hydrocarbon diluent having a boiling point of 
not higher than 40.degree. C. 
DETAILED DESCRIPTION OF THE INVENTION 
It has been found that a low density polyethylene covering various grades 
in a wide range can be obtained without the lowering of bulk density by 
subjecting a certain amount of ethylene to a pre-polymerization prior to 
the slurry copolymerization of ethylene and an .alpha.-olefin. 
According to this invention, a polymer in slurry of good property having a 
bulk density of more than 0.35 g/ml is obtained and the bulk density is 
substantially the same as that of ethylene homopolymers obtained by the 
slurry process. 
This invention has, therefore, the great advantages that there are no 
troubles in handling of the slurry, such as stirring, transferring, 
filtrating, drying, and storing, which are usually conducted in the 
production method of polyethylene by the slurry process. 
Further, this invention is epoch-making in that various grades in a very 
wide range, including the low density polyethylene of less than 0.1 in 
melt index, the production of which has been hitherto impossible in either 
the slurry process or the solution process as mentioned above can be 
covered by an one single process, i.e. the slurry process alone. 
The catalyst component (A) which may be used in the method of this 
invention is titanium and/or vanadium compounds supported with a magnesium 
compound. 
The magnesium compound which may be used as a support includes, for 
example, magnesium oxide, magnesium carbonate, basic magnesium carbonate, 
magnesium sulphate, magnesium hydroxide, magnesium hydroxychloride, 
magnesium chloride, magnesium bromide, dialkoxymagnesium and magnesium 
carboxylic acid salts, and their double salts with other metal compounds 
such as alumimum oxide and boron oxide, and mixtures of these magnesium 
compounds with metal compounds such as iron hydroxide, aluminum chloride 
and aluminum hydroxide or with organic compounds such as alcohols, 
ketones, amines and esters. 
The titanium and/or vanadium compounds which may be used for the 
preparation of the catalyst component (A) are those used as the transition 
metal component of the Ziegler catalyst and the typical examples include 
titanium tetrachloride, titanium trichloride, titanium haloalkoxide, 
vanadium tetrachloride and vanadyl trichloride. 
The catalyst component (A) may be prepared by supporting the titanium 
and/or vanadium compound with the support in accordance with the known 
process for the preparation of supported catalysts used in the Ziegler 
catalyst. There are, for example, used the process for supporting by 
reacting the support with liquid titanium and/or vanadium compound while 
heating, or co-pulverizing the support with the titanium and/or vanadium 
compounds. A third component other than the magnesium component may be 
added in the co-pulverizing of the magnesium component and the titanium 
and/or vanadium component. For such an additive, siloxane polymers and an 
aluminum halide-ether complex are particularly preferred. 
The organoaluminum compounds which may be used for the catalyst component 
(B) are represented by the formula, 
EQU A1 R.sub.n X.sub.3-n 
wherein R is a hydrocarbon residue, X is hydrogen, halogen or an alkoxy 
group and n is 1 to 3. The typical examples include trimethylaluminum, 
triethylaluminum, triisobutyl-aluminum, diethylaluminum monochloride, 
diethylaluminum monohydride, diethylaluminum monoethoxide and 
ethylaluminum monoethoxymonochloride. 
The component (B) is used within the range of 1 to 1000 mols, preferably 2 
to 500 mols based on 1 mol of the component (A). 
In the copolymerization according to this invention, a low-boiler 
hyrocarbon diluent having a boiling point of not higher than 40.degree. C. 
is used. Examples of the diluent include propane, n-butane, iso-butane, 
n-pentane, iso-pentane, cyclopropane, cyclobutane and mixtures thereof and 
particularly, propane, n-butane and iso-butane are preferred. 
.alpha.-Olefins which may be used in the copolymerization with ethylene are 
represented by the formula, 
EQU R'--CH.dbd.CH.sub.2 
wherein R' is a hydrocarbon resiude of 1 to 10 carbon atoms. Examples of 
.alpha.-olefins are propylene, butene-1, pentene-1, hexen-1, 
4-methyl-pentene-1 and styrene. The amount of .alpha.-olefin to be 
copolymerized with ethylene is within such a range that the density of the 
resulting copolymer is controlled to the extent of 0.925 to 0.950 g/ml. 
Although the amount varies depending on the type of .alpha.-olefins, it is 
usually within the range of about 0.5 to 12% by weight of the final 
copolymer. 
The pre-polymerization according to this invention is conducted by 
polymerizing ethylene in the amount of more than 50 g per 1 g of the 
component (A) and not more than 20% by weight of the entire amount of the 
monomers to be polymerized (i.e. the total of the monomer amount to be 
pre-polymerized and the amount of the monomers to be co-polymerized) in 
the presence of the catalyst consisting of the components (A) and (B). 
Although the upper limit of the ethylene amount to be pre-polymerized 
varies depending on the type of .alpha.-olefins, the type of catalyst 
components and the desired grade of copolymers, 3000 g per 1 g of 
component (A) is preferred. If the prepolymerization amount of ethylene is 
50 g or less, the resulting polymer is reduced in bulk density and 
deteriorated in the slurry property so that the industrial production gets 
into troubles. 
On the other hand, if the pre-polymerization amount is over 20% by weight 
of the entire amount of polymerization, the obtained polymer is 
deteriorated in a low-melting property, flexibility and transparency, all 
of which are the distinctive qualities of the low density polyethylene. 
The liquid diluent for pre-polymerization is not particularly limited, and 
the liquid diluents which are usually used in the polymerization of 
olefins may be used. The low-boiling hydrocarbons which are used in the 
copolymerization of this invention as mentioned above may be also used as 
the diluent for pre-polymerization. When the high-boiling liquid 
hydrocarbon such as hexane and heptane is used in the pre-polymerization, 
it should be at an amount of less than 10 weight % of the low-boiling 
hydrocarbon which is used as the diluent for copolymerization. 
The pre-polymerization temperature, pressure and time are not particularly 
limited. The pre-polymerization is usually conducted at temperature of 
20.degree. C. to 100.degree. C. under pressure of reduced pressures to 40 
atm. The polymerization time normally is between several minutes and 
several hours. 
After the completion of pre-polymerization, the copolymerization may be 
conducted using the usual manner known in the art except the specifically 
defined conditions as mentioned above. The polymerization temperature may 
range from 20.degree. C. to 100.degree. C., preferably from 40.degree. C. 
to 95.degree. C., while the pressure may range from normal pressure to 100 
atms and usually is between normal pressure and 70 atms. 
If the copolymerization after the pre-polymerization is conducted using the 
high-boiling hydrocarbon diluent such as hexane and heptane instead of the 
low-boiling hydrocarbon (for example, propane and n-butane) as defined 
hereinbefore, the resulting polymer is dissolved in or swelled with the 
diluent and thus, the slurry property deteriorates so that such procedures 
as filtration get into trouble (see Comparative Example 2 mentioned 
hereinafter). Thus, the purpose of effectively producing the low density 
polyethylene on a commercial scale can not be attained. 
It is necessary for attainment of the purposes of this invention to 
fullfill the three requirements as defined hereinbefore: 
(1) using the supported catalyst component (A) of a high activity, 
(2) conducting the pre-polymerization of ethylene prior to the 
copolymerization and 
(3) using the low-boiling hydrocarbon having a boiling point of not higher 
than 40.degree. C. as the diluent for copolymerization. 
In the practice of this invention, the molecular weight of the polymer 
varies depending on the mode of polymerization, type of catalysts and 
other polymerization conditions, but it may be controlled by the addition 
of, for example, hydrogen or dialkyl zinc, if necessary. 
As mentioned above, the low density polyethylene as desired can be obtained 
by pre-polymerizing a certain amount of ethylene in the presence of 
catalyst components (A) and (B) and successively copolymerizing ethylene 
and an .alpha.-olefin. It should be, however, pointed out that the 
catalyst component (A) is not to be newly added in the copolymerization 
step. If the component (A) is added in the copolymerization step, the 
resulting polymer becomes viscous and is reduced in bulk density so that 
the desired effects can be obtained. On the other hand, the catalyst 
component (B) may be newly added in the copolymerization step, if 
necessary. 
The low density polyethylene slurry obtained by this invention does not 
need the complicated after-treatment which is normally practised for the 
polyethylene slurry obtained with use of the conventional catalyst 
consisting of titanium trichloride and an organoaluminum compound. By only 
vapourizing the low-boiling hydrocarbon diluent, the polymer product can 
be obtained in form of powders and therefore, the production process is 
simplified. Polymers dissolved in part in the diluent, if any, can be also 
used for products in that condition and accordingly, this invention is 
exceedingly useful in that all of the polymers obtained can be utilized.

This invention will be illustrated by the following non-limitative 
examples. 
EXAMPLE 1 
23.1 g of magnesium chloride, 2.4 g of titanium tetrachloride and 4.5 g of 
aluminum chloride-diphenyl ether complex were charged into a 600 ml 
capacity vibration mill containing about 80 steel balls of 12 mm in 
diameter under nitrogen atmosphere and pulverized at room temperature for 
14 hours. The resulting powders were separated from the steel balls under 
nitrogen atmosphere to obtain an activated titanium composition with a Ti 
content of 2.0 weight % (catalyst component (A)). 0.04 g of the component 
(A) and 1 ml of triethylaluminum as catalyst component (B) were charged 
together with 50 ml of n-heptane into a glass reactor under nitrogen 
atmosphere, in which 2.5 g of ethylene were then subjected to a 
pre-polymerization at room temperature while stirring. The product mixture 
thus obtained is, hereinafter, referred to as a pre-polymer slurry. 
Amount of ethylene pre-polymerized: 62.5 g/g.component (A). 
Next, the entire amount of the pre-polymer slurry above obtained was 
charged into a 6 l capacity stainless steel autoclave under nitrogen 
atmosphere and then the nitrogen atmosphere was replaced with a 3:7 
mixture of n-butane and iso-butane (hereinafter, referred to as mere 
butane), and thereafter, 1.3 kg of butane were charged. 
Then, 300 g of butene-1 were charged into the autoclave and hydrogen was 
charged until the partial pressure of hydrogen reached 3 kg/cm.sup.2 G. 
Ethylene was then fed and polymerized under a pressure of 25 kg/cm.sup.2 G 
(partial pressure of ethylene, about 10 kg/cm.sup.2 Abs.) at 80.degree. C. 
for 2 hours. After the purging of the butane and unreacted ethylene and 
butene-1, 1008 g of an ethylene-butene-1 copolymer (butene-1 content, 9.6 
weight % ) were obtained. 
Intrinsic viscosity (tetralin, 135.degree. C.): 1.20 dl/g 
Bulk density: 0.40 g/ml 
Number of ethyl groups: 24.3/1000 carbon atoms 
Density at 23.degree. C: 0.926 g/ml 
MI (Melt Index), measured according to ASTMD-1238-65T (Test Condition E): 
6.6 
The polymerization activity of the catalyst in this polymerization reaction 
was 12.6 kg/g.(A).hr wherein the symbol "(A)" means the catalyst component 
(A) or 630 kg/g.Ti.hr and the yield of polymer was 25.2 kg/g.(A) or 1260 
kg/g.Ti. 
Since the amount of pre-polymerization was 2.5 g and the entire amount of 
polymerization was 1008 g, the ratio of the pre-polymerization amount to 
the entire polymerization amount was 0.25 wt.%. 
EXAMPLE 2 
Copolymerization of ethylene and propylene was conducted using the equal 
amount of the pre-polymer slurry prepared in Example 1. 
In the same procedure as Example 1, the equal amount of the pre-polymer 
slurry, 1.3 kg of butane and hydrogen (pressure, 3 kg/cm.sup.2) were fed 
into the 6 l autoclave and then, a gaseous mixture of ethylene and 
propylene was charged into the autoclave in which the mol ratio of 
propylene to ethylene in gas phase was adjusted to 0.15. Polymerization 
was conducted at the same temperature and pressure as in Example 1. 
After 2.3 hours for polymerization, 1,075 g of a polyethylene copolymer 
(propylene content, 9.9 weight %) were obtained. 
Intrinsic viscosity: 1.32 dl/g 
Bulk density: 0.42 g/ml 
Number of methyl groups: 30.3/1000 carbon atoms 
Density: 0.927 g/ml 
MI: 5.3 
Polymerization activity of catalyst: 
11.7 kg/g.(A).hr or 584 kg/g.Ti.hr 
Yield of polymer: 
26.9 kg/g.(A) or 1342 kg/g.Ti 
The ratio of the pre-polymerization amount to the entire polymerization 
amount was 0.25 weight %. 
EXAMPLE 3 
The pre-polymerization and oopolymerization were conducted in the same 
procedure as Example 1 except that the component (A) was prepared from 2.4 
g of AA type titanium trichloride (manufactured by Stauffer Co., USA), 
23.1 g of magnesium chloride and 4.5 g of aluminum chloridediphenylether 
complex. 
After 2.6 hours for copolymerization, 1,012 g of a polyethylene copolymer 
(butene-1 content, 6.5 wt.%) were obtained. 
Intrinsic viscosity: 1.10 dl/g 
Bulk density: 0.40 g/ml 
Number of ethyl groups: 19.7/1000 carbon atoms 
Density: 0.927 g/ml 
MI: 13.5 
Polymerization activity of catalyst: 9.7 kg/g.(A).hr or 504 kg/g.Ti.hr 
Yield of polymer: 25.2 kg/g.(A) or 1310 kg/g.Ti 
The ratio of the pre-polymerization amount to the entire polymerization 
amount was 0.25 weight %. 
EXAMPLE 4 
The pre-polymerization and copolymerization were conducted in the same 
procedure as Example 1 except that 2 ml of triisobutyl aluminum were used 
instead of triethyl aluminum as component (B). 
After 2 hours for copolymerization, 1088 g of a polyethylene copolymer 
(butene-1 content 7.9 wt.%) were obtained. 
Intrinsic viscosity: 1.12 dl/g 
Bulk density: 0.40 g/ml 
Number of ethyl groups: 20.3/1000 carbon atoms 
Density: 0.926 g/ml 
MI: 13.0 
Catalytic activity: 13.6 kg./g.(A).hr or 680 kg/g.Ti.hr 
Yield: 27.2 kg/g.(A) or 1360 kg/g.Ti 
The amount of pre-polymerization was 62.5 g/g.(A) and the ratio of the 
pre-polymerization amount to the entire polymerization amount was 0.23 
weight %. 
Comparative Example 1 
For comparison the copolymerization of ethylene and butene-1 was conducted 
in the same procedure as Example 1 except that the components (A) and (B) 
were direct charged into the autoclave without conducting the 
prepolymerization. 
After one hour for polymerization, the polymerization velocity dropped 
extensively. 
After two hours, 502 g of a polyethylene copolymer (butene-1 content 7.9 
wt.%) were obtained. 
Intrinsic viscosity: 1.28 dl/g 
Number of ethyl groups: 20.3/1000 carbon atoms 
Density: 0.928 g/ml 
MI: 5.7 
Catalytic activity: 6.3 kg/g.(A).hr or 313 kg/g.Ti.hr 
Yield: 12.6 kg/g.(A) or 626 kg/g.Ti 
Though the resulting polymer particles were too sticky to exactly measure a 
bulk density, it gave about 0.23 g/ml. 
As is apparent from Comparative Example 1, The omission of 
pre-polymerization results in the formation of sticky polymer particles 
and in the lowering of bulk density so that the industrial production 
encounters a difficulty. Also, the slurry property becomes worse and a 
diffusion rate of ethylene to butane is lowered so that the polymerization 
velocity and polymer yield are reduced extensively. 
Comparative Example 2 
For comparison copolymerization was conducted using n-heptane instead of 
butane as the diluent. 
2 l of n-heptane, the equal amount of the pre-polymer slurry used in 
Example 1 and 300 g of butene-1 were charged into a 5 l capacity autoclave 
and hydrogen was fed up to a partial pressure of 3 kg/cm.sup.2, and then, 
ethylene was fed until a polymerization pressure reached 15 kg/cm.sup.2 G 
(partial pressure of ethylene, about 10 kg/cm.sup.2 Abs). Polymerization 
was conducted at 75.degree. C. After an hour, the absorption of ethylene 
finished practically and then the polymerization was discontinued. 
The reaction product was a remarkably viscous polymer slurry so that it was 
difficult to advance such treatments as filtration. 
By vapourizing n-heptane from this polymer slurry, 410 g of a block polymer 
(butene-1 content, 7.7 wt.%) were obtained. 
Number of ethyl groups: 19.8/1000 carbon atoms 
Density: 0.926 g/ml 
Bulk density: impossible to measure. 
The ratio of the pre-polymerization amount to the entire polymerization 
amount was 0.61 wt.% 
The Comparative Examples 1 and 2 show that the effects of this invention 
can not be attained in the absence of the two requirements i.e. using the 
specifically defined diluents and conducting the pre-polymerization. 
EXAMPLE 5 
0.04 g of the activated titanium composition used in Example 1, 1 ml of 
triethyl aluminum and 1.3 kg of butane were charged into a 6 l capacity 
autoclave, hydrogen was fed up to a partial pressure of 2 kg/cm.sup.2, and 
then 5 g of ethylene were fed. Reaction was conducted at 40.degree. C. for 
one hour and thus a pre-polymer slurry was prepared. The amount of 
ethylene pre-polymerized was 3.7 g (the prepolymerization amount, 92.5 
g/g.(A)). 
Next, 350 g of butene-1 were fed into the autoclave, then ethylene was fed 
and polymerized at 80.degree. C. under the polymerization pressure of 25 
kg/cm.sup.2 G for 2 hours. 1,102 g of a polyethylene copolymer (butene-1 
content 7.9 wt.%) were obtained. 
Intrinsic viscosity: 1.57 dl/g 
Bulk density: 0.41 g/ml 
Density: 0.927 g/ml 
Number of ethyl groups: 20.3/1000 carbon atoms 
MI: 1.85 
Catalytic activity: 13.8 kg/g.(A).hr or 689 kg/g.Ti.hr 
Yield: 27.6 kg/g.(A) or 1378 kg/g.Ti. 
The ratio of the pre-polymerization amount to the entire polymerization 
amount was 0.34 wt.%. 
EXAMPLE 6 
In accordance with the manner of Example 1, an activated titanium 
composition with a 2.0 wt.% Ti content (component (A)) was prepared from 
23.1 g of magnesium chloride, 2.4 g of titanium tetrachloride and 4.5 g of 
dimethylpolysiloxane having a viscosity of 100 centistokes. 
Using 0.04 g. of the component (A), a pre-polymer slurry was prepared in 
the same manner as Example 1. The amount of pre-polymerization: 62.5 
g/g.(A). Next, copolymerization of ethylene and butene-1 was conducted in 
the same manner as Example 1. 
After 2 hours, 806 g of a polyethylene copolymer (butene-1 content, 8.0 
wt.%) were obtained. 
Intrinsic viscosity: 1.21 dl/g 
Bulk density: 0.40 g/ml 
Number of ethyl groups: 20.4/1000 carbon atoms 
Density: 0.926 g/ml 
MI: 5.0 
Catalytic activity: 10.1 kg/g.(A).hr or 504 kg/g.Ti.hr 
Yield: 20.2 kg/g.(A) or 1008 kg/g.Ti 
Ratio of pre-polymerization amount: 0.28 wt.% 
EXAMPLE 7 
The pre-polymerization and copolymerization were conducted in the same 
procedure as Example 1 except that the component (A) prepared in Example 6 
and 2 ml of triisobutyl aluminum as component (B) were used. After 2 hours 
for polymerization, 870 g of a polyethylene copolymer (butene-1 content, 
8.3 wt.%) were obtained. 
Intrinsic viscosity: 1.12 dl/g 
Bulk density: 0.40 g/ml 
Number of ethyl groups: 21.2/1000 carbon atoms 
Density: 0.927 g/ml 
MI: 13.0 
Catalytic activity: 10.9 kg/g.(A).hr or 545 kg/g.Ti.hr 
Yield: 21.8 kg/g.(A) or 1090 kg/g.Ti. 
The amount of pre-polymerization was 62.5 g/g.(A) and the ratio of the 
pre-polymerization amount to the entire polymerization amount was 0.29 
wt.%. 
Comparative Example 3 
For comparison, copolymerization of ethylene and butene-1 was conducted in 
the same manner as Example 6 except that the pre-polymerization was 
omitted and the components (A) and (B) were direct charged into the 
autoclave. After one hour, the polymerization velocity dropped 
drastically. 
After 2 hours for polymerization, 402 g of a polyethylene copolymer 
(butene-1 content 8.0 wt.%) were obtained. 
Intrinsic viscosity: 1.26 dl/g 
Number of ethyl groups: 20.5/1000 carbon atoms 
Density: 0.927 g/ml 
MI: 5.5 
Though the resulting polymer particles were too sticky to measure a bulk 
density exactly, it gave about 0.23 g/ml. 
Catalytic activity: 5.1 kg/g.(A).hr or 255 kg/g.Ti.hr 
Yield: 10.1 kg/g,(A) or 505 kg/g.Ti 
Ratio of pre-polymerization amount: 0.62 wt.%. 
Comparative Example 4 
The pre-polymer slurry prepared in Example 6 was used and copolymerization 
was conducted using n-heptane as a diluent. 
2 l of n-heptane, the equal amount of the prepolymer slurry prepared in 
Example 6 and 300 g of butene-1 were charged into a 6 l capacity 
autoclave, hydrogen was fed up to a partial pressure of 3 kg/cm.sup.2 and 
then, ethylene was fed until a polymerization pressure reached 15 
kg/cm.sup.2 G (ethylene partial pressure, about 10 kg/cm.sup.2 Abs), and 
polymerized at 75.degree. C. After one hour for polymerization, the 
absorption of ethylene finished practically and then the polymerization 
was discontinued. 
The reaction product was a very viscous polymer solution so that it was 
impossible to advance such procedures as filtration. 
By vapourizing n-heptane from this polymer solution, 330 g of a polymer 
(butene-1 content 8.0 wt.%) were obtained. 
Number of ethyl groups: 20.5/1000 carbon atoms 
Density: 0,928 g/ml 
Bulk density: impossible to measure 
Ratio of pre-polymerization amount: 0.76 wt.%. 
EXAMPLES 8-11 
In accordance with Example 1, an activated titanium composition (component 
(A)) was prepared using TiCl.sub.4, MgCl.sub.2 and dimethylpolysiloxane (a 
linear polysiloxane) having a viscosity of 100 centistokes in amounts as 
indicated in Table 2. 
The pre-polymerization and copolymerization of ethylene and butene-1 were 
conducted in the same manner as Example 5 except using the above activated 
titanium component and triisobutyl aluminum. The polymerization results 
are indicated in Table 2. 
TABLE 2 
__________________________________________________________________________ 
Activated Titanium Composition 
[Catalyst Component (A)] 
Composition, wt. % 
Dimethylpoly- 
Ti Content 
Amount 
Amount of Al (iso-butyl).sub.3 
Example No. 
TiCl.sub.4 
MgCl.sub.2 
siloxane 
% g ml 
__________________________________________________________________________ 
8 4.0 81.0 
15.0 1.01 0.047 
2.0 
9 4.0 85.8 
10.2 1.01 0.046 
2.0 
10 7.8 82.1 
10.1 1.97 0.037 
2.0 
11 12.0 
78.0 
10.0 3.03 0.035 
2.0 
__________________________________________________________________________ 
Yield of Yield of Polymer 
Bulk Amount of Pre- 
Polymer per g of Den- 
Intrinsic 
Den- 
Ethyl polymerization 
Example 
*(1) Catalytic Activity 
Catalyst sity 
Viscosity 
sity 
Groups *(3) 
No. g Kg/g .multidot. (A) .multidot. hr 
Kg/g .multidot. Ti .multidot. hr 
Kg/g .multidot. (A) 
Kg/g .multidot. Ti 
g/ml 
dl/g g/ml 
*(2) 
MI g/g .multidot. 
__________________________________________________________________________ 
(A) 
8 533 5.65 565 11.3 1130 0.40 
1.28 0.926 
20.5 
5.0 
78.7 
(8.0) (0.69) 
9 565 6.15 615 12.3 1230 0.41 
1.24 0.926 
20.0 
5.4 
80.4 
(7.8) (0.65) 
10 820 11.1 563 22.2 1126 0.40 
1.27 0.927 
19.0 
5.0 
100.0 
(7.4) (0.45) 
11 862 12.3 410 24.6 820 0.41 
1.21 0.926 
20.5 
5.6 
105.7 
(8.0) (0.43) 
__________________________________________________________________________ 
Notes: 
*(1) The parentheses mean a butene1 content (wt. %) of polymer. 
*(2) The number per 1000 carbon atoms. 
*(3) The parentheses mean the ratio of the prepolymerization amount to th 
entire polymerization amount 
The foregoing will also apply to Tables 2 and 3. 
EXAMPLES 12-13 
An activated titanium composition (component (A)) was prepared in the same 
manner as in Example 1 except that dimethylpolysiloxane in the type and 
amount as set forth in Table 3 was used instead of aluminum 
chloride-diphenylether complex. 
The pre-polymerization and copolymerization of ethylene and butene-1 were 
conducted in the same manner as Example 5 except using the above activated 
titanium component and triisobutyl aluminum. 
The polymerization results are indicated in Table 3. 
TABLE 3 
__________________________________________________________________________ 
Activated Titanium Composition 
[Catalyst Component (A)] 
Composition, wt. % 
Dimethylpoly- 
Ti Content 
Amount 
Amount of Al (iso-butyl).sub.3 
Example No. 
TiCl.sub.4 
MgCl.sub.2 
siloxane 
% g ml 
__________________________________________________________________________ 
*(4) 
12 8.0 82.0 
10.0 2.00 0.035 
2.0 
*(5) 
13 8.2 81.5 
10.3 2.07 0.036 
2.0 
__________________________________________________________________________ 
Notes: 
*(4) A cyclic dimethylpolysiloxane mixture having a viscosity of 13 
centistokes (degree of polymerization 7-9). 
*(5) A linear polysiloxane having a viscosity of 300 centistokes. 
- Yield of Yield of Polymer 
Bulk Amount of Pre- 
Polymer per g of Den- 
Intrinsic 
Den- 
Ethyl polymerization 
Example 
*(1) Catalytic Activity 
Catalyst sity 
Viscosity 
sity 
Groups *(3) 
Na- g Kg/g .multidot. (A) .multidot. hr 
Kg/g .multidot. Ti .multidot. hr 
Kg/g .multidot. (A) 
Kg/g .multidot. Ti 
g/ml 
dl/g g/ml 
*(2) 
MI g/g .multidot. 
__________________________________________________________________________ 
(A) 
12 827 11.8 590 23.6 1180 0.41 
1.26 0.926 
20.6 
5.0 
105.7 
(8.0) (0.45) 
13 831 11.6 560 23.1 1116 0.40 
1.25 0.926 
21.6 
5.0 
102.8 
(8.5) (0.45) 
__________________________________________________________________________ 
EXAMPLE 14 
In this example, 100 g of ethylene were prepolymerized using 70.degree. C. 
instead of 40.degree. C. in the prepolymerization process of Example 5. 
Pre-polymerization amount: 2500 g/g. (A). 
In the same manner as Example 5, then, polymerization was conducted using 
350 g of butene-1. After 1.75 hours, 913 g of a polyethylene copolymer 
(butene-1 content 7.9 wt.%) were obtained. 
Intrinsic viscosity: 1.11 dl/g 
Number of ethyl groups: 20.3/1000 carbon atoms 
Density: 0.925 g/ml 
Bulk density: 0.37 g/ml 
MI: 13.3 
Catalytic activity: 13.0 kg/g.(A).hr or 650 kg/g.Ti.hr 
Yield: 22.8 kg/g.(A) or 1138 kg/g.Ti 
Ratio of pre-polymerization amount: 10.95 wt.%. 
EXAMPLE 15 
Polymerization was conducted in the same procedure as Example 1 except that 
hydrogen was charged into the copolymerization system until the hydrogen 
partial pressure reached 0.1 kg/cm.sup.2 G. 
After 1.75 hours for polymerization, 983 g of an ethylene copolymer 
(butene-1 content 7.5 wt.%) were obtained. 
Intrinsic viscosity: 3.0 dl/g 
Number of ethylene groups: 19.3/1000 carbon atoms 
Density: 0.925 g/ml 
Bulk density: 0.40 g/ml 
MI: 0.07 
Catalytic activity: 14.0 kg/g.(A).hr or 702 kg/g.Ti.hr 
Yield: 24.5 kg/g.(A) or 1229 kg/g.Ti 
Ratio of pre-polymerization amount: 0.25 wt.% 
The low density, low melt index polyethylene having the grade as indicated 
above (density 0.925 g/ml, MI 0.07) is one belonging to the field of 
polyethylene, which has been regarded as being impossible to be produced 
by the conventional solution process and slurry process. 
EXAMPLE 16 
An activated titanium component was prepared using magnesium 
hydroxychloride as a support and polymerization was conducted. 
10 g of magnesium hydroxychloride were charged into a Kumagawa type 
extractor, extracted with titanium tetrachloride at its boiling 
temperature for 20 hours, then washed with n-hexane at its boiling 
temperature for 10 hours, dried under reduced pressure at 50.degree. C. 
and thus, an activated titanium with a 0.5 wt.% Ti content (component (A)) 
was obtained. 
The pre-polymerization and copolymerization were conducted using 0.20 g of 
the above component (A) in the same procedure as Example 1. 12.5 g of 
ethylene were pre-polymerized (in the amount of pre-polymerization, 62.5 
g/g.(A)). 
After 2.0 hours for polymerization, 973 g of an ethylene-butene-1 copolymer 
(butene-1 content 8.2 wt.%) were obtained. 
Intrinsic viscosity: 1.23 dl/g 
Number of ethyl groups: 21.0/1000 carbon atoms 
Density: 0.925 g/ml 
Bulk density: 0.37 g/ml 
MI: 5.4 
Catalytic activity: 2.43 kg/g.(A).hr or 487 kg/g.Ti.hr 
Yield: 4.86 kg/g.(A) or 975 kg/g.Ti 
Ratio of pre-polymerization amount: 1.28 wt.%. 
EXAMPLE 17 
The pre-polymerization and copolymerization were conducted in the same 
procedure as Example 1 except using propane as the copolymerization 
diluent. 
After 2 hours for polymerization, 853 g of an ethylene-butene-1 copolymer 
(butene-1 content 7.8 wt.%) were obtained. 
Intrinsic viscosity: 1.53 dl/g 
Bulk density: 0.42 g/ml 
Number of ethyl groups: 20.1/1000 carbon atoms 
Density: 0.925 g/ml 
MI: 1.80 
Catalytic activity: 10.7 kg/g.(A).hr or 533 kg/g.Ti.hr 
Yield: 21.4 kg/g.(A) or 1066 kg/g.Ti 
Ratio of pre-polymerization amount: 0.29 wt.%. 
Comparative Examples 5-6 
For showing that the limitation of the prepolymerization amount as defined 
in this invention has a critical nature, a comparison was made with 
Example 1. The pre-polymerization and copolymerization of ethylene and 
butene-1 were conducted in the same manner as Example 1 except using the 
pre-polymerization amounts as set forth in Table 4. 
The polymerization results show that owing to the deterioration of the 
slurry property, the diffusion of ethylene becomes worse in the course of 
copolymerization and thus the polymerization activity is reduced. Though 
the resulting polymer particles were too sticky to exactly measure a bulk 
density, it gave a lower value at an approximate estimate as set forth in 
Table 4. 
TABLE 4 
__________________________________________________________________________ 
Yield 
Com- 
Amount of 
of Bulk 
In- 
para- 
Pre-poly- 
Poly- Yield of Den- 
trinsic 
tive 
meri- mer Polymer per 
sity 
Vis- 
Den- 
Ethyl 
Ex. 
zation *(1) 
Catalytic Activity 
g of Catalyst 
g/ml 
cosity 
sity 
Groups 
No. 
g g/g .multidot. (A) 
g Kg/g .multidot. (A) .multidot. hr 
Kg/g .multidot. Ti .multidot. hr 
Kg/g .multidot. (A) 
Kg/g .multidot. Ti 
*(6) 
dl/g 
g/ml 
*(2) 
MI Remark 
__________________________________________________________________________ 
5 0.2 
5 520 6.5 325 13.0 650 (0.23) 
1.30 
0.927 
20.8 
5.3 
Sticky 
(8.1) polymer 
particles 
6 1.2 
30 603 7.5 377 15.1 754 (0.25) 
1.31 
0.926 
23.1 
5.3 
" 
(9.1) 
Ex. 1 
2.5 
62.5 1008 
12.6 630 25.2 1260 0.40 
1.20 
0.926 
24.3 
6.6 
Non-sticky 
(9.6) polymer 
particles 
__________________________________________________________________________ 
Note: 
*(6) The parentheses mean an approximate value.