Ethylene-.alpha.-olefin copolymer and process for producing the same

An ethylene-.alpha.-olefin copolymer is disclosed, which comprises ethylene and an .alpha.-olefin having from 3 to 10 carbon atoms, has an ethylene/.alpha.-olefin molar ratio of from 88/12 to 98/2, and which has a number average molecular weight of from 35,000 to 80,000 and a weight average molecular weight/number average molecular weight ratio of from 1.8/1 to 3.0/1 as determined by gel permeation chromatography. A process for producing the ethylene-.alpha.-olefin copolymer is also disclosed. The ethylene-.alpha.-olefin copolymer exhibits excellent transparency and excellent low-temperature heat-sealing properties. The process is advantageous from the standpoint of equipment, energy and cost.

FIELD OF THE INVENTION 
This invention relates to an ethylene-.alpha.-olefin copolymer and a 
process for producing the same. More particularly, it relates to an 
ethylene-.alpha.-olefin copolymer excellent in transparency and 
low-temperature heat-sealing properties and to a process for producing 
such an ethylene-.alpha.-olefin copolymer. 
BACKGROUND OF THE INVENTION 
Ethylene-.alpha.-olefin copolymers exhibit excellent characteristics such 
as heat resistance, weather resistance and ozone resistance and have 
therefore found broad applications as automobile materials, construction 
materials, industrial materials and resin modifiers. In particular, 
ethylene-.alpha.-olefin copolymers having a high ethylene content are soft 
resins having properties midway between rubbers and crystalline plastics 
and are now in growing demand as packaging film, etc. Inter alia, 
copolymers obtained by copolymerizing ethylene and an .alpha.-olefin in 
the presence of a titanium-based polymerization catalyst are known as 
linear low-density polyethylene (hereinafter abbreviated as LLDPE) and are 
widely employed. However, films produced from LLDPE do not always satisfy 
requirements of low-temperature heat-sealing properties and transparency. 
The insufficient transparency or heat-sealing properties of the LLDPE are 
considered attributed to non-uniform composition of ethylene and 
.alpha.-olefin in the copolymer and broad molecular weight distribution. 
On the other hand, several processes for producing ethylene-.alpha.-olefin 
copolymers using a vanadium-based catalyst have been proposed. For 
example, JP-B-46-21212 (the term "JP-B" as used herein means an "examined 
published Japanese patent application") discloses a process of solution 
polymerization of ethylene and an .alpha.-olefin using a catalyst system 
comprised of a vanadium compound and an organoaluminum compound. According 
to this process, a copolymer is obtained in the form of a uniform 
solution, i.e., as dissolved in a polymerization solvent. However, the 
vanadium compound used greatly declines in catalytic activity as the 
polymerization temperature increases. For example, as shown in the working 
examples of this patent publication, the polymerization activity becomes 
too low to be suited for practical use in a high temperature range, e.g., 
at 100.degree. C, only to produce a copolymer having broad molecular 
weight distribution and having a high solvent extractable content. 
JP-B-47-26185 discloses a process for producing an 
ethylene-.alpha.-olefin copolymer by using a halogenated lower aliphatic 
hydrocarbon or a hydrocarbon having from 3 to 5 carbon atoms as a 
polymerization solvent and a combination of a VOX3 compound and an 
organoaluminum compound as a catalyst system. Polymerization in a 
halogenated hydrocarbon produces a polymer as a precipitate insoluble in 
the polymerization solvent, forming a slurry having a low viscosity as a 
whole. This is economically advantageous in stirring or transporting the 
system but, in turn, there are problems arising from decomposition of the 
halogenated hydrocarbon, such as corrosion of apparatus and storage 
stability of the polymer. In the case of slurry polymerization in a 
hydrocarbon solvent having 3 to 5 carbon atoms, closeness of the boiling 
point of this solvent to that of the ethylene-copolymerizable 
.alpha.-olefin, particularly propylene or 1-butene, gives rise to a great 
problem in separating the unreacted monomer and the polymerization solvent 
in the purification step. Further, from an economical viewpoint, this 
process is not always recognized advantageous since hydrocarbons having 3 
to 5 carbon atoms have low boiling points and therefore require a freezing 
apparatus for liquefication and a pressure-resistant apparatus as well as 
a cooling medium. Furthermore, the process requires large-sized equipment 
for an ashing step for removing the catalyst components incorporated into 
the produced polymer particles. 
JP-B-55-24447 discloses a process for producing an ethylene-1-butene 
copolymer having an ethylene content of from 85 to 95 mol %, in which 
copolymerization is effected at a temperature of from -20.degree. to 
30.degree. C. in an aliphatic hydrocarbon having from 6 to 15 carbon atoms 
as a polymerization solvent in the presence of a catalyst system composed 
of a soluble vanadium compound and an organoaluminum halide. Similarly, 
JP-A-63-17912 (the term "JP-A" as used herein means an "unexamined 
published Japanese patent application") describes a process for 
copolymerizing ethylene and an .alpha.-olefin at from -20.degree. to 
30.degree. C. using a catalyst system composed of a soluble vanadium 
compound and a chlorinated organoaluminum compound. Both of these 
processes relate to slurry polymerization with a difference lying in that 
the Al/V atomic molar ratio is from 2/1 to 50/1 in the former process and 
from 55/1 to 170/1 in the latter process. According to either process, 
since polymerization is carried out at a relatively low temperature (from 
-20.degree. to 30.degree. C.), a large quantity of a cooling medium and an 
energy for driving a freezing device are necessary. In addition, the 
reaction rate attained is so low that the retention time in the reaction 
vessel becomes long, increasing the overall volume of the reaction vessel, 
which results in large consumption of stirring power in the reaction 
vessel. 
In short, when ethylene-.alpha.-olefin copolymers having a high ethylene 
content are produced by slurry polymerization, that is, in a system in 
which a part of the copolymer produced is insoluble in a polymerization 
solvent so that the reaction proceeds while the insoluble copolymer being 
in a precipitated state, by the conventional processes, it is necessary to 
make a proper choice of a solvent, and the reaction should be conducted at 
low temperatures, which is disadvantageous from the standpoint of 
equipment and energy. On the other hand, in the case of solution 
polymerization in a system in which copolymerization proceeds while the 
whole copolymer being dissolved in the solvent, the conventional processes 
require relatively high temperatures and suffer from reduction of catalyst 
efficiency, resulting in economical disadvantage. 
From all these considerations, it has been keenly demanded to develop a 
slurry polymerization technique which can be effected at a moderate 
temperature, more specifically at around 40 to 65.degree. C. at which a 
vanadium-based catalyst exerts the possible highest activity, which wold 
be of advantage from the standpoint of equipment, energy, and cost. The 
most relevant process so far proposed in this connection is found, e.g., 
in JP-B-46-11028. According to the disclosed technique, however, the 
resulting copolymer has a largely non-uniform composition and a broad 
molecular weight distribution, thereby possessing poor strength and poor 
transparency. 
SUMMARY OF THE INVENTION 
One object of this inveniton is to eliminate the disadvantages associated 
with the conventinal processes and to provide a process for producing an 
ethylene-.alpha.-olefin copolymer having a narrow molecular weight 
distriubtioon and a uniform composition by slurry polymerization with 
industrial advantages from the standpoint of equipment, energy, and cost. 
Another object of this invention is to provide an ethylene-.alpha.-olefin 
copolymer having a narrow molecular weight distribution, a uniform 
composition, and a low solvent extractable content, thereby exhibiting 
satisfactory transparency and excellent low-temperature heat-sealing 
properties. 
The inventors have conducted extensive investigations on a process for 
producing an ethyelene-.alpha.-olefin copolymer having a narrow molecular 
weight distribution and a uniform composition. As a result, it has now 
been found that slurry polymerization can be carried out at a low 
viscosity by using a threecomponent catalyst system comprising a specific 
vanadium compound, a specific organoaluminum compound and a specific 
halogenated ester compound at a specific mixing ratio and by properly 
selecting a copolymerization temperature, a molar ratio of ethylene and an 
.alpha.-olefin, and a copolymerization solvent to be used. It has also 
been found that an ethylene-.alpha.-olefin copolymer having the 
above-described properties can be obtained by slightly elevating the 
temperature of the system after completion of the copolymerization thereby 
making it possible to handle the reaction system as a uniform solution and 
facilitating ashing of the copolymer. The present invention has been 
completed based on these findings. 
That is, in one embodiment the present invention provides an 
ethylene-.alpha.-olefin copolymer which comprises ethylene and an 
.alpha.-olefin having from 3 to 10 carbon atoms, has an 
ethylene/.alpha.-olefin molar ratio of from 88/12 to 98/2, and which has a 
number average molecular weight of from 35,000 to 80,000 and a weight 
average molecular weight/number average molecular weight ratio of from 
1.8/1 to 3.0/1 as determined by gel permeation chromatography (GPC). 
Further, in another embodiment the present invention provides a process for 
producing an ethylene-.alpha.-olefin copolymer having an 
ethylene/.alpha.-olefin molar ratio of from 88/12 to 98/2 and having a 
number average molecular weight of from 35,000 to 80,000 and a weight 
average molecular weight/number average molecular weight ratio of from 
1.8/1 to 3.0/1 as determined by GPC, which comprises copolymerizing 
ethylene and an .alpha.-olefin having from 3 to 10 carbon atoms at an 
ethylene/.alpha.-olefin molar ratio of from 35/65 to 60/40 and at a 
temperature of from 40 to 80.degree. C. using a catalyst system composed 
of a vanadium compound represented by formula: 
EQU VO(OR).sub.n X.sub.3-n 
Wherein R represents a hydrocarbon group; X represents a halogen atom; and 
n is a number of from 0 to 3, an organoaluminum compound represented by 
formula: 
EQU R'.sub.m AlX.sub.3-m 
wherein R' represents a hydrocarbon group; X represents a halogen atom; and 
m represents a number of from 1 to 3, and a halogenated ester compound 
represented by formula: 
##STR1## 
wherein R" represents an organic group derived from a hydrocarbon group 
having from 1 to 20 carbon atoms by substituting a part or all of the 
hydrogen atoms thereof with a halogen atom; and R"' represents a 
hydrocarbon group having from 1 to 20 carbon atoms, at an organoaluminum 
compound/vanadium compound molar ratio of 2.5/1 or more and at a 
halogenated ester compound/vanadium compound molar ratio of 1.5/1 or more, 
in a system in which a polymer insoluble in a hydrocarbon solvent and a 
polymer soluble in a hydrocarbon solvent coexist. 
The process of the present invention is characterized in that the 
copolymerization is carried out in a system where a hydrocarbon 
solvent-soluble polymer and a hydrocarbon solvent-insoluble polymer 
coexist, more specifically, in a mixed system comprising a dissolved state 
polymer and insoluble fine polymer particles having a particle size of not 
more than 0.5 mm. Such a mixed polymerization system, when set at 
40.degree. C, contains 95% by weight or more of the hydrocarbon 
solvent-insoluble polymer based on the total polymer. In this case, the 
system has a low viscosity characteristic of a slurry polymerization 
system. When the system is set at 70.degree. C or higher, the system 
becomes a uniform solution.

DETAILED DESCRIPTION OF THE INVENTION 
Important in the present invention are choices of a combination of catalyst 
components, a copolymerization solvent, and a copolymerization 
temperature. 
Specific examples of the vanadium compound represented by formula 
VO(OR).sub.n X.sub.3-n, wherein R, X, and n are as defined above, include 
VOCl.sub.3, VO(OCH.sub.3)Cl.sub.2, VO(OCH.sub.3).sub.2 Cl, 
VO(OCH.sub.3).sub.3, VO(OC.sub.2 H.sub.5)Cl.sub.2, VO(OC.sub.2 
H.sub.5).sub.2 Cl, VO(OC.sub.2 H.sub.5).sub.3, VO(OC.sub.3 
H.sub.7)Cl.sub.2, VO(OC.sub.3 H.sub.7).sub.2 Cl, VO(OC.sub.3 
H.sub.7).sub.3, VO(O-iso-C.sub.3 H.sub.7)Cl.sub.2, VO(O-iso-C.sub.3 
H.sub.7).sub.2 Cl, VO(O-iso-C.sub.3 H.sub.7).sub.3, and mixtures thereof. 
These vanadium compounds except for VOCl.sub.3 can easily be prepared by 
reacting VOCl.sub.3 with an alcohol or by reacting VOCl.sub.3 with 
VO(OR).sub.3. Preferred of them are those wherein 0.ltoreq.n.ltoreq.1, 
i.e., VOCl.sub.3, VO(OCH.sub.3)Cl.sub.2, VO(OC.sub.2 H.sub.5)Cl.sub.2, 
VO(OC.sub.3 H.sub.7)Cl.sub.2, and VO(O-iso-C.sub.3 H.sub.7)Cl.sub.2, from 
the viewpoint of obtaining copolymers having a narrow molecular weight 
distribution and a uniform composition. In particular, VOCl.sub.3 (n=0) is 
the most preferred. 
The copolymerization system in the co-presence of a hydrocarbon 
solvent-insoluble polymer and a hydrocarbon solvent-soluble polymer may 
also be achieved by the use of the vanadium compounds wherein 
1.ltoreq.n.ltoreq.3, e.g., VO(OCH.sub.3).sub.2 Cl, VO(OCH.sub.3).sub.3, 
VO(OC.sub.2 H.sub.5).sub.2 Cl, VO(OC.sub.2 H.sub.5).sub.3, VO(OC.sub.3 
H.sub.7).sub.2 Cl, VO(OC.sub.3 H.sub.7).sub.3, VO(O-iso-C.sub.3 
H.sub.7).sub.2 Cl, and VO(O-iso C.sub.3 H.sub.7).sub.3. However, the 
ethylene-.alpha.-olefin copolymers obtained from such a system have two 
endothermic peaks in differential thermal analysis (DTA) by means of a 
differential scanning calorimeter (DSC), one in the region -between 
80.degree. C and 105.degree. C and the other in the region exceeding 
105.degree. C. Some of such copolymers may suffer from reduction of 
heat-sealing properties or transparency. 
The organoaluminum compound represented by formula R'.sub.m AlX.sub.3-m, 
wherein R', X, and m are as defined above, which can be used in the 
catalyst system includes (C.sub.2 H.sub.5).sub.2 AlCl, (C.sub.4 
H.sub.9).sub.2 AlCl, (C.sub.6 Hl.sub.3).sub.2 AlCl, (C.sub.2 
H.sub.5).sub.1.5 AlCl.sub.1.5, (C.sub.4 H.sub.9).sub.1.5 AlCl.sub.1.5, 
(C.sub.6 Hl.sub.3).sub.1.5 AlCl.sub.1.5, C.sub.2 H.sub.5 AlCl.sub.2, 
C.sub.4 H.sub.9 AlCl.sub.2, and C.sub.6 Hl.sub.3 AlCl.sub.2. From the 
standpoint of reaction rate and yield, preferred of them are those wherein 
1.ltoreq.m.ltoreq.2, with (C.sub.2 H.sub.5).sub.1.5 AlCl.sub.1.5 being 
more preferred. 
The halogenated ester compound represented by formula 
##STR2## 
wherein R" and R"', are as defined above, which can be used as a catalyst 
component preferably includes those wherein R" is a group in which all the 
hydrogen atoms thereof are substituted with a halogen atom, more 
preferably perchlorocrotonic acid esters. Specific examples of the 
halogenated ester compound are ethyl dichloroacetate, methyl 
trichloroacetate, ethyl trichloroacetate, methyl dichlorophenylacetate, 
ethyl dichlorophenylacetate, methyl perchlorocrotonate, ethyl 
perchlorocrotonate, propyl perchlorocrotonate, isopropyl 
perchlorocrotonate, butyl perchlorocrotonate, cyclopropyl 
perchlorocrotonate, and phenyl perchlorocrotonate. 
In the copolymerization system, the vanadium compound concentration ranges 
from 0.00005 mmol/l to 5 mmols/l, preferably from 0.0001 mmol/l to 1 
mmol/l. The molar ratio of the organoaluminum compound to the vanadium 
compound should be 2.5/1 or more, preferably from 2.5/1 to 30/1, and the 
molar ratio of the halogenated ester compound to the vanadium compound 
should be 1.5/1 or more. If the organoaluminum compound/vanadium compound 
molar ratio is less than 2.5/1, the copolymerization reaction becomes 
extremely unstable, resulting in stopping or failing to obtain a desired 
copolymer having a narrow molecular weight distribution. If the 
halogenated ester compound/ vanadium compound molar ratio is less than 
1.5/1, the resulting copolymer has a broad molecular weight distribution. 
The copolymerization according to the present invention is carried out in a 
hydrocarbon solvent. The hydrocarbon solvent to be used includes aliphatic 
hydrocarbons, e.g., hexane, heptane, octane, decane, dodecane, and 
kerosine; alicyclic hydrocarbons, e.g., cyclohexane, methylcyclopentane, 
and methylcyclohexane; and aromatic- hydrocarbons, e.g., benzene, toluene, 
and xylene. Preferred of them are hexane, heptane, octane, and 
cyclohexane. The solvent may be partly or wholly replaced with an 
.alpha.-olefin, e.g., propylene, 1-butene, 1-pentene, and 1-hexene. 
The copolymerization temperature ranges from 40 to 80.degree. C, preferably 
from 40 to 65.degree. C. If it is lower than 40.degree. C, the reaction 
rate is seriously reduced and, in addition, specific cooling or freezing 
equipment would be necessary to remove the reaction heat. On the other 
hand, at temperatures higher than 80.degree. C, the whole copolymer 
produced becomes soluble in the solvent throughout the copolymerization 
system to increase the viscosity of the system, thus so much increasing 
the power required for stirring and mixing. At even higher temperatures, 
the polymerization activity of the catalyst is lost, failing to produce a 
copolymer. 
The copolymerization is carried out under atmospheric pressure or under an 
elevated pressure, preferably at a pressure of from 1 to 30 kg/cm.sup.2, 
more preferably from 1 to 20 kg/cm.sup.2. 
The retention time of the copolymerization reaction mixture in the 
copolymerization vessel ranges from 10 to 180 minutes, preferably from 20 
to 120 minutes, on average. In order to assure good reproducibility in 
obtaining an ethylene-.alpha.-olefin copolymer with satisfactory physical 
properties, the total polymer concentration in the copolymerization system 
is adjusted not to exceed 15% by weight, preferably not to exceed 12% by 
weight. 
The copolymerization is effected in system where a hydrocarbon 
solvent-insoluble polymer and a hydrocarbon solvent-soluble polymer 
coexist while stirring. It is preferable to control the molar ratio of 
ethylene and .alpha.-olefin to be charged in such a manner that the 
hydrocarbon solvent-insoluble polymer content may amount to 95% by weight 
or more at 40.degree. C or the total polymer may solely comprise the 
hydrocarbon solvent-soluble polymer at 70.degree. C. In such a 
copolymerization system, the copolymerization temperature is preferably 
set at from 40 to 65.degree. C, more preferably at from 40 to 55.degree. 
C. In this particular system, since the reaction proceeds with the 
hydrocarbon solvent-insoluble polymer being suspended in the form of fine 
particles of 0.5 mm or smaller in diameter, the viscosity of the system 
can be kept low, the stirring power energy can be minimized, and the 
reaction heat can easily be removed. Moreover, a satisfactory mixing state 
of the catalyst and the monomers can be obtained, as is advantageous for 
obtaining a polymer having a narrow molecular weight distribution and a 
uniform composition. The temperature in the downstream side of the 
reaction vessel, on the other hand, is controlled at 70.degree. C or 
higher, whereby the total polymer in this side becomes soluble in the 
solvent. Such temperature control can thus eliminate the problem due to 
precipitated polymer particles generally encountered in slurry 
polymerization systems effected on an industrial scale, i.e., 
sedimentation and deposition of the polymer particles in areas of 
insufficient flow in the plant or obstruction of piping. 
The weight ratio of the hydrocarbon solventinsoluble polymer and the 
hydrocarbon solvent-soluble polymer can be determined by filtering the 
reaction mixture sampled from the copolymerization system through a 
metallic net of 300 mesh to separate the hydrocarbon solvent-soluble 
matter and hydrocarbon solvent-insoluble matter, removing the hydrocarbon 
solvent from each matter by drying, and weighing each of the resulting 
solids. 
The ethylene-.alpha.-olefin copolymer according to the present invention 
has an ethylene/.alpha.-olefin molar ratio of from 88/12 to 98/2 and a 
ratio of weight average molecular weight (Mw) to number average molecular 
weight (Mn), Mw/Mn (hereinafter referred to as a Q value), of from 1.8/1 
to 3.0/1 as determined by GPC. The ethylene-.alpha.-olefin copolymer 
satisfying these conditions exhibits excellent performance properties in 
terms of strength at break, elongation, and surface hardness as measured 
according to JIS K-6301. Preferred ethylene-.alpha.-olefin copolymers 
which are particularly excellent in heat-sealing properties and 
transparency have an ethylene/.alpha.-olefin molar ratio of from 92/8 to 
96/4 and a Q value of from 1.8/1 to 2.6/1, and shows only one endothermic 
peak as determined with DSC, said peak being between 80.degree. C and 
105.degree. C. 
The ethylene-.alpha.-olefin copolymer according to the present invention 
has a number average molecular weight of from 35,000 to 80,000 as 
determined by GPC. If it is less than 35,000, the copolymer produced has 
an insufficient strength. On the other hand, if it exceeds 80,000, the 
molding processability is poor. 
GPC as used herein was conducted under the following measurement 
conditions: 
GP Chromatograph: 150 C Model, manufactured by Waters Corp. 
Column: Shodex.RTM. AC-80M, manufactured by Shoda Denko K.K. 
Sample Volume: 300 .mu.l (polymer conc.: 0.2% by weight) 
Flow Rate: 1 ml/min 
Temp.: 135.degree. C. 
Solvent: 1,2,4-trichlorobenzene 
A calibration curve was prepared in a usual manner by using a standard 
polystyrene produced by Tosoh Corporation. Data were processed by the use 
of Data Processor CP-8 Model III, manufactured by Tosoh Corporation. 
Molecular weight control of the ethylene/.alpha.-olefin copolymer can be 
done with H2, diethylamine, allyl chloride, pyridine-N-oxide, etc., with 
H.sub.2 being particularly preferred. 
The present invention is now illustrated in greater detail by way of the 
following Examples, Comparative Examples, Reference Examples, and 
Comparative Reference Examples, but it should be understood that the 
present invention is not deemed to be limited thereto. 
EXAMPLE 1 
Ethylene and 1-butene were continuously copolymerized by using a 5 l-volume 
SUS-made polymerization vessel equipped with a stirring blade. 
Hexane as a polymerization solvent was continuously fed into the lower part 
of the vessel at a rate of 5 l/hr., while a polymerization mixture was 
continuously withdrawn from the upper part of the vessel so as to maintain 
the volume of the polymerization mixture in the vessel at 5 l. As a 
catalyst system, vanadium oxytrichloride, ethylaluminum sesquichloride, 
and n-butyl perchlorocrotonate were continuously fed to the upper part of 
the vessel at a rate of 0.050 mmol/hr, 1.2 mmols/hr, and 0.12 mmol/hr, 
respectively. Ethylene and 1-butene as monomers were continuously fed to 
the lower part of the vessel at a feed rate of 230 g/hr and 360 g/hr, 
respectively. Molecular weight control was effected with hydrogen. The 
copolymerization temperature was controlled at 55.degree. C by circulating 
cooling water through a jacket provided around the vessel. 
The copolymerization reaction was carried out under the above-recited 
conditions to thereby produce an ethylene-1-butene copolymer in the form 
of a mixture of a polymerization solvent-insoluble matter and a 
polymerization solvent-soluble matter. A small amount of methanol was 
added to the polymerization mixture withdrawn from the reaction vessel to 
stop the reaction. Any unreacted monomers were removed from the mixture, 
the mixture was washed with water, and the solvent was removed by 
stripping with steam in a large quantity of water. The collected copolymer 
was dried at 80.degree. C under reduced pressure for one day. There was 
thus obtained an ethylene-1-butene copolymer at an output rate of 170 
g/hr. 
The ethylene content of the resulting copolymer was found to be 96.1 mol% 
by infrared absorption analysis. GPS analysis revealed that the copolymer 
had an Mw of 112,000 and an Mn of 55,000, giving a Q value of 2.2/1. The 
DTA curve of the copolymer obtained by the use of DSC had a single fusion 
peak, showing a melting point (Tm) at 99.degree. C and a heat of fusion 
(.DELTA.Hm) of 19 cal/g. 
The polymerization mixture withdrawn from the reaction vessel was filtered 
through a metallic net of 300 mesh to separate the solvent-insoluble 
matter and solvent-soluble matter, and each of them was weighed to give an 
insoluble matter/soluble matter weight ratio of 61/39. 
When the copolymer was press molded, the resulting molded article exhibited 
highly satisfactory transparency and had a strength at break of 330 
kgf/cm.sup.2, an elongation at break of 710%, and a surface hardness of 
93, each measured in accordance with JIS K-6301. 
EXAMPLES 2 TO 5 
Ethylene and 1-butene were copolymerized in the same manner as in Example 
1, except for altering the conditions as shown in Table 1. Each of the 
resulting copolymers was analyzed and evaluated in the same manner as in 
Example 1, and the results obtained are shown in Table 2. 
EXAMPLES 6 AND 7 
Copolymerization was carried out in the same manner as in Example 1, except 
for replacing 1-butene with propylene and altering the polymerization 
conditions as shown in Table 1. Each of the resulting 
ethylene-.alpha.-olefin copolymers was analyzed and evaluated in the same 
manner as in Example 1, and the results obtained are shown in Table 2. 
COMATIVE EXAMPLES 1 AND 2 
Copolymerization was carried out in the same manner as in Example 1, except 
for using, as catalyst components, vanadium oxytrichloride and 
ethylaluminum sesquichloride only but using no n-butyl perchlorocrotonate 
and altering the reaction conditions as shown in Table 1. Each of the 
resulting copolymers was analyzed and evaluated in the same manner as in 
Example 1, and the results obtained are shown in Table 2. 
TABLE 1 
__________________________________________________________________________ 
Feed Rate Solvent- 
of Catalyst Component Insoluble/ 
Feed Organo- 
Halogenated 
Feed Rate of Monomer 
Output 
Solvent- 
Rate of 
Vanadium 
aluminum 
Ester Ethy- 
.alpha.- 
Ethylene/ 
Polymn. 
Rate of 
Soluble 
Example 
Solvent 
Compound 
Compound 
Compound 
lene 
Olefin 
.alpha.-Olefin 
Temp. 
Copolymer 
Copolymer 
No. (l/hr) 
(mmol/hr) 
(mmol/hr) 
(mmol/hr) 
(g/hr) 
(g/hr) 
Molar Ratio 
(.degree.C.) 
(g/hr) 
Weight 
__________________________________________________________________________ 
Ratio 
Example 1 
5.0 0.050 1.2 0.12 230 360 56/44 55 170 61/39 
Example 2 
" 0.081 1.1 0.22 220 " 55/45 50 150 44/56 
Example 3 
" 0.12 1.7 0.33 200 395 50/50 " 155 13/87 
Example 4 
4.3 " " " 175 " 47/53 40 170 4/96 
Example 5 
" 0.14 1.9 0.38 165 " 46/54 " 165 2/98 
Compar- 
3.8 0.58 4.0 -- 180 " 48/52 " 180 8/92 
ative 
Example 1 
Example 6 
5.0 0.075 1.1 0.21 250 375 50/50 55 230 10/90 
Example 7 
" 0.092 1.3 0.25 " 425 47/53 50 220 2/98 
Compar- 
4.5 0.35 2.4 -- " 400 55/45 " 225 6/94 
ative 
Example 2 
__________________________________________________________________________ 
TABLE 2 
__________________________________________________________________________ 
Ethylene/ Mechanical Properties 
.alpha.-Olefin DSC Strength 
Elongation 
Example 
Molar Ratio 
GPC Peak 
Tm .DELTA.Hm 
Trans- 
at Break 
at Break 
Surface 
No. in Copolymer 
-- Mn 
-- Mw 
Q Shape 
(.degree.C.) 
(cal/g) 
parency 
(kgf/cm.sup.2) 
(%) Hardness 
__________________________________________________________________________ 
Example 1 
96.1/3.9 
55000 
112000 
2.0/1 
single 
99 19 good 330 710 93 
Example 2 
94.5/5.5 
59000 
118000 
" " 86 13 " 350 730 91 
Example 3 
92.2/7.8 
62000 
131000 
2.1/1 
" 75 7.6 " 330 670 86 
Example 4 
89.5/10.5 
40000 
88000 
2.2/1 
" 66 3.7 " 220 990 77 
Example 5 
88.6/11.4 
61000 
130000 
2.1/1 
" 57 2.1 " 200 760 71 
Comparative 
89.7/10.3 
33000 
106000 
3.2/1 
broad 
70 4.5 poor 180 600 75 
Example 1 
Example 6 
91.9/8.1 
45000 
99000 
2.2/1 
single 
79 8.5 good 250 690 90 
Example 7 
88.3/11.7 
36000 
85000 
2.4/1 
" 62 3.0 " 160 730 83 
Comparative 
90.5/9.5 
45000 
149000 
3.3/1 
broad 
73 5.1 poor 170 670 87 
Example 2 
__________________________________________________________________________ 
COMATIVE EXAMPLE 3 
Copolymerization was carried out in the same manner as in Example 1, except 
for changing the ethylene feed rate to 100 g/hr and the 1-butene feed rate 
to 500 g/hr. The copolymer produced was totally soluble in the hexane 
solvent, and the system became a viscous solution. The copolymer recovered 
was rubber-like and had a low strength at break as 140 kgf/cm.sup.2. 
COMATIVE EXAMPLE 4 
Copolymerization was carried out in the same manner as in Example 1, except 
for changing the ethylene feed rate to 300 g/hr, the 1-butene feed rate to 
300 g/hr, and the polymerization temperature to 25.degree. C. As a result, 
the copolymerization system became a slurry in which most of the copolymer 
produced was suspending in the hexane solvent as insoluble fine particles, 
a part of the copolymer particles being found deposited onto the inner 
wall of the piping in the downstream side of the outlet of the vessel. The 
recovered copolymer had a low elongation at break as 420%. 
EXAMPLE 8 
Ethylene and 1-butene were continuously copolymerized by using the same 
polymerization vessel as used in Example 1 to which was connected a 10 
l-volume SUS-made pressure-resistant stirring tank equipped with a 
stirring blade, a jacket, and an outlet for withdrawing gasified 
components at the top thereof (hereinafter referred to as degassing 
apparatus). 
Hexane as a polymerization solvent was continuously fed to the lower part 
of the vessel at a feed rate of 5 l/hr, while the polymerization mixture 
was continuously withdrawn from the upper part of the vessel so as to 
maintain the volume of the polymerization mixture in the vessel at 5 l and 
introduced into the degassing apparatus. The polymerization mixture was 
further continuously withdrawn from the side of the degassing apparatus so 
as to control the volume of the polymerization mixture in the apparatus at 
5 l. As a catalyst system, vanadium oxytrichloride, ethylaluminum 
sesquichloride, and ethyl dichlorophenylacetate were continuously fed to 
the lower part of the vessel at a rate of 0.020 mmol/hr, 0.55 mmol/hr, and 
0.060 mmol/hr, respectively. Ethylene and 1-butene were continuously fed 
to the lower part of the vessel at a rate of 155 g/hr and 175 g/hr, 
respectively. Molecular weight control was effected with hydrogen. The 
copolymerization temperature was controlled at 55.degree. C. by 
circulating cooling water through a jacket provided around the vessel. 
The copolymerization reaction was carried out under the above-recited 
conditions to thereby produce an ethylene-1-butene copolymer in the form 
of a mixture of polymerization solvent-insoluble matter and polymerization 
solvent-soluble matter. The polymerization mixture was continuously 
withdrawn from the vessel and introduced into the degassing apparatus. A 
small amount of methanol was added to the polymerization mixture in the 
degassing apparatus to stop the reaction. The inner temperature of the 
apparatus was controlled at 40.degree. C. while removing the unreacted 
monomers. The mixture withdrawn from the degassing apparatus assumed a 
slurry condition in which copolymer particles having a particle size of 
from about 0.01 to 0.1 mm were suspending in the hexane solvent. 
The polymerization mixture sampled from the degassing apparatus was 
filtered through a metallic net of 300 mesh to separate the polymerization 
solvent-insoluble matter and polymerization solvent-soluble matter, and 
each of them was weighed to give an insoluble matter/soluble matter weight 
ratio of 98/2. On the other hand, the polymerization mixture sampled from 
the polymerization vessel was found to have an insoluble matter/soluble 
matter weight ratio of 44/56. 
While continuing the polymerization, warm water was then circulated through 
the jacket of the degassing apparatus to control the inner temperature at 
70.degree. C. The polymerization mixture withdrawn from the apparatus 
contained no solid particles and, instead, the copolymer produced was 
found to be in a dissolved state in the hexane solvent. 
Polymerization was further continued, and the inner temperature of the 
degassing apparatus was cooled to 40.degree. C. Then, the polymerization 
mixture returned to the slurry state comprising suspending copolymer 
particles. 
The structural values of the copolymer sampled from the polymerization 
mixture kept at 70.degree. C were consistent with those of the copolymer 
sampled from the mixture cooled to 40.degree. C within measurement errors. 
The resulting copolymer was found to have an ethylene content of 94 mol% 
by infrared absorption analysis; an Mw of 98,000, an Mn of 49,000 by GPC 
analysis, giving a Q value of 2.0/1; a single fusion peak showing a Tm of 
95.degree. C and a .DELTA.Hm of 23 cal/g by DSC. Transparency and 
mechanical properties of the copolymer were evaluated in the same manner 
as in Example 1. The polymerization conditions used are shown in Table 3, 
and the results of analyses and evaluations are shown in Table 4. 
EXAMPLES 9 AND 10 AND COMATIVE EXAMPLES 5 AND 6 
Copolymerization was carried out in the same manner as in Example 8, except 
for changing the feed rates of the polymerization solvent, organoaluminum 
compound, halogenated ester compound, ethylene, and 1-butene or changing 
the kind or amount of the vanadium compound as shown in Table 3. 
Each of the resulting copolymers was analyzed and evaluated in the same 
manner as in Example 1, and the results obtained ar shown in Table 4. 
TABLE 3 
__________________________________________________________________________ 
Feed Rate 
of Catalyst Component 
Feed Organo- 
Halogenated 
Feed Rate 
Rate of 
Vanadium 
aluminum 
Ester of Monomer 
Example 
Solvent 
Compound*.sup.1 
Compound*.sup.2 
Compound 
Ethylene 
.alpha.-Olefin 
No. (l/hr) 
(mmol/hr) 
(mmol/hr) 
(mmol/hr) 
(g/hr) 
(g/hr) 
__________________________________________________________________________ 
Example 8 
5.0 0.020 0.55 0.060*.sup.3 
155 175 
Example 9 
" 0.020 0.50 0.080*.sup.3 
155 175 
Example 10 
" 0.018 0.50 0.100*.sup.4 
150 190 
Comparative 
3.8 0.40 3.5 -- 170 200 
Example 5 
Comparative 
3.8 .sup. 0.50*.sup.5 
4.0 -- 170 200 
Example 6 
__________________________________________________________________________ 
Solvent-Insoluble/Solvent- 
Output 
Soluble Polymer Weight Ratio 
Polymn. 
Rate of Degassing 
Example 
Temp. 
Copolymer 
Polymeri- 
Apparatus 
No. (.degree.C.) 
(g/hr) 
zation Vessel 
at 40.degree. C. 
at 70.degree. C. 
__________________________________________________________________________ 
Example 8 
55 100 44/56 98/2 0/100 
Example 9 
50 110 64/36 97/3 0/100 
Example 10 
45 105 87/13 96/4 0/100 
Comparative 
55 140 40/60 97/3 1/99 
Example 5 
Comparative 
55 80 43/57 95/5 4/96 
Example 6 
__________________________________________________________________________ 
Note: 
*.sup.1 Vanadium oxytrichloride 
*.sup.2 Ethylaluminum sesquichloride 
*.sup.3 Ethyl dichlorophenylacetate 
*.sup.4 nButyl perchlorocrotonate 
*.sup.5 Tri(isopropoxy)oxyvanadium 
TABLE 4 
__________________________________________________________________________ 
Ethylene/ Mechanical Properties 
.alpha.-Olefin DSC Strength 
Elongation 
Example 
Molar Ratio 
GPC Peak Tm .DELTA.Hm 
Trans- 
at Break 
at Break 
Surface 
No. in Copolymer 
-- Mn 
-- Mw 
Q Shape (.degree.C.) 
(cal/g) 
parency 
(kgf/cm.sup.2) 
(%) Hardness 
__________________________________________________________________________ 
Example 8 
94.0/6.0 
49000 
98000 
2.0/1 
single 95 23 good 320 720 93 
Example 9 
94.8/5.2 
55000 
110000 
" " 85 10 " 340 740 91 
Example 10 
92.7/7.3 
63000 
132000 
2.1/1 
" 76 8.1 " 310 650 86 
Comparative 
93.2/6.8 
34000 
106000 
3.1/1 
broad 77 14 poor 330 700 88 
Example 5 
Comparative 
93.6/6.4 
31000 
138000 
4.5/1 
broad, 78 
6.3 
extreme- 
300 610 83 
Example 6 2 peaks 110 
2.2 ly poor 
(small peak 
at 110.degree. C.) 
__________________________________________________________________________ 
REFERENCE EXAMPLES 1 TO 3 
Each of the copolymers obtained in Examples 8, 9, and 10 was mixed with 
0.1% by weight of calcium stearate, 0.2% by weight of 
octadecyl-3-(3',5'-di-t-butyl-4-hydroxyphenyl)propionate ("IRGANOX.RTM. 
1076" produced by Chiba-Geigy AG), and 0.05% by weight of trisnonylphenyl 
phosphite ("ANTIGENE.RTM. TNP" produced by Sumitomo Chemical Co., Ltd.). 
The resulting compound was pelletized and molded into a film having a 
thickness of 30 .mu.m. Physical properties of the film are shown in Table 
5. 
COMATIVE REFERENCE EXAMPLES 1 TO 3 
Each of the copolymers obtained in Comparative Examples 5 and 6 and an 
LLDPE was compounded with additives and molded into a film in the same 
manner as in Reference Examples 1 to 3. Physical properties of each of the 
resulting films are shown in Table 5. 
TABLE 5 
______________________________________ 
Reference Example No. 
Comp. Ref. Ex. No. 
1 2 3 1 2 3 
______________________________________ 
Copolymer 
Ex. 8 Ex. 9 Ex. 10 
Comp. Comp. LLDPE 
Ex. 5 Ex. 6 *5 
Density*.sup.1 
0.9064 0.9081 0.9012 
0.9018 
0.9020 
0.9120 
(g/cm.sup.3) 
Haze*.sup.2 (%) 
2.8 3.2 2.2 6.9 25.3 10.4 
CXS*.sup.3 (%) 
1.6 1.5 2.1 3.6 5.7 10.3 
Heat- 92 95 90 93 98 110 
Sealable 
Temp.*.sup.4 
(.degree.C.) 
______________________________________ 
Note: 
*.sup.1 Measured at 25.degree. C. 
*.sup.2 Measured according to ASTM D1003 
*.sup.3 A weight loss of a test specimen on immersion in xylene at 
30.degree. C. for 24 hours was determined. 
*.sup.4 Two sheets of a sample film (width: 1.5 cm) were fused together 
under a pressure of 2 kg/cm.sup.2 for a sealing time of 1 second by means 
of a heat sealer, and the sealed area was subjected to peel test. The 
minimum heat sealing temperature which provided such a sealing strength 
that the sealed area was divided into two layers through breaking without 
involving peeling at the sealed surface was taken as a heatsealable 
temperature. 
*.sup.5 A trial product of SUMIKATHENE .RTM. L produced by Sumitomo 
Chemical Co., Ltd., having a melt flow index (MFI) of 1.9 at 190.degree. 
C., which is confirmed to be an ethylene1-butene copolymer by infrared 
absorption analysis. 
As described above, the present invention provides an 
ethylene-.alpha.-olefin copolymer having a narrow molecular weight, a 
uniform composition, and a small solvent extractable content and thereby 
exhibiting excellent transparency and low-temperature heat-sealing 
properties. The process according to the present invention for producing 
such an ethylene-.alpha.-olefin copolymer, in which copolymerization is 
carried out in such a system that a hydrocarbon solvent-insoluble polymer 
and a hydrocarbon solvent-soluble polymer coexist, is advantageous from 
the standpoint of equipment, energy, and cost. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.