Note: Descriptions are shown in the official language in which they were submitted.
10~669~7
The present invention relates to a process for the
high yield polymerization of ethylene and 1,3-butadiene
to give copolymers characterized by:
i) high chain linearity
ii) narrow molecular weight range,
~ iii) substantially complete 1,4-trans configuration
of the butadiene units,
iv~ statistical inter- and intramolecular distribu-
tion of the monomer units,
v) low content of residual vanadium, even without
any purification stagè,
such copolymers being vulcanizable by means of usual sulphur
base recipes in order to produce cross-linked products
similar to high density polyethylenes which, however, have
improved mechanical, thermal and chemical properties.
Ethylene-butadiene copolymers are known from the art,
however no known product has contemporaneously the above-
said characteristics.
They all are to be deemed indispensable when a
product is desired having substantial advantages with respect
to polyethylenes.
- In fact the chain linearity, e~g. the substantial
absence of intermolecular cyclizations, cross-linkings and
transversal bonds, warrants a low flowing of the melted
polymer and enhances the workability and the extrudibility
thereof.
The narrow molecular weight range, combined with the
chain linearity, ensures the copolymer to have better mecha-
nical properties, such as the impact resistance, under the
same molecular weight, and other characteristics.
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104669,q
The low polydispersity polymers are the most suit-
able to be used in the transformation techniques based on
the centrifugal moulding, the injection moulding of large
manufactured articles, fiber spinning and~-others.
The 1,4-trans addition of butadiene units into a
polyethlene chain is the only one which does not disturb
notably the crystalline structure of this last polymer,
at least at not high contents of copolymerized butadiene.
As a consequence the physical properties (melting point
density, etc,) of the copolymers, which are indeed able
to vulcanize at high rates, are not sensitively different
from the ones of high density polyethylene.
The statistical distribution of the monomeric units
both inside the single macromolecule and between a macro-
molecule and the other one, is a necessary feature for
the whole polymer undergoing a homogeneous cross-linking.
One such copolymers may be high yield vulcanized to give
products having physical-mechanlcal, thermal and chemical
properties better than the ones of the best polyethylenes.
At last the low vanadium content is also an important
characteristic of ethylene-butadiene copolymers since,
because of the presence of double bonds, oxidation react-
ions have to be avoided in which vanadium acts as a cata-
lyst. Moreover vanadium salt rests, if present in
appreciable amounts, give the copolymers unwished colour-
ings. The use of catalysts producing high yields of
copolymerization, beside removing the cited drawbacks,
allows to run simple processes from which the washing
phase of the obtained polymer is lacking.
All abovesaid is necessary in order to let the
preparation of ehtylene-butadiene copolymers be interest-
ing from an :industriaIJ point of view.
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104~69'7
The different behaviour under polymerization of the
monomers, e.g. ethylene and butadiene, explains the difficulty of
obtaining, directly from the polymerization of mixtures thereof
copolymers having the abovesaid properties.
Characteristics and properties of the ethylene-butadiene
copolymers are strictly depending on the preparation process and,
therefore, on the particularly used catalyst. The known catalyst
systems, employing titanium, vanadium or chromium compounds as
the transition metal compound, besides not warranting the formation
of copolymers having all the abovesaid characteristics, do not give
sufficiently high polymerization yields.
In Canadian applications Nos. 094,055, 155,084 and
188,555, Applicant has described the preparation of ethylene-
butadiene copolymers which may be homogeneously cross-linked
by means of sulphur base recipes, however the catalysts therein
described are not very active when relatively low molecular weight
products are desired.
It has now been surprisingly found that it is possible
to obtain high polymerization yields of ethylene-butadiene
- 20 copolymers characterized by high chain linearity, narrow molecular
weight range, almost complete 1,4-trans configuration of the
butadiene units, inter- and intra-molecular statistical distri-
bution of the monomeric units, low vanadium content, the process
consisting in polymerizing, under the conditions hereinafter
reported, ethylene and butadiene mixtures in the presence of one or
more aromatic solvents and a catalyst system consisting of: ;
- ~ a) one or more vanadium compounds soluble in the
-~ abovesaid solvents;
b) one or more aluminium compounds having the general for-
--~ 4 -
lQ4~;697
mula RlR2AlX in which Rl and R2,the same or different,
are alkyl, cycloalkyl, alkylaryl or aryl radicals
containing from l to 18 carbon atoms or hydrogen and
X is chlorine or bromire;
c) one or more acid compounds according to Lewis or
Bronsted ;
d) thionyl chloride and/or hexachlorocyclopentadiene.
The vanadium compounds referred to in point (a)
include tetra- and pentavalent and complexed trivalent
vanadium halides, vanadium and vanadyl alcoholates~ che-
lates compounds and complexes.
The term "complexes" refers to all compounds con-
taining bonds between vanadium and mono- or bidentate
organic ligands, wherein "ligand" means an ion or a mole-
cule bound to metal or deemed to be bound to metal and
the terms "mono- and bidentate" mean a molecule having
one or~ respectively~ two positions therewith it can
form covalent or coordination bonds with the metal.
Examples of vanadium compounds which may be employed
are: vanadium tetrachloride (preferably stabilized in
SiC14 solution), vanadyl trichloride, vanadium tri-
chloride complexed with three molecules of tetrahydro-
furan, vanadium triacetylacebonate, vanadyl diacetyl-
acetonate, vanadyl triisopropylate, tetra(dimethylamide)
vanadium, etc.
The components (b) of the catalyst system are
aluminium dihydrocarbylhalides~ among which a prefer-
red use is made of diethylmonochloride and diisobutyl-
monochloride owing to cost and availability reasons.
Similar results are obtained by employing the
corresponding bromine derivatives. Also aluminium
hydrocarbyl halide hydrides may be advanta~eously
104669~
employed.
The components (c) of the inventive catalyst are
all acid compounds according to Lewis or Bronsted and
include both polyhalogenated compounds of metals belong-
ing to the III or IV group of the periodic system, and
the compounds able to free H+ ions, that is organic
acids, inorganic acids and water, provided that they
are sufficiently soluble in the hydro~arbon reaction
medium or are solubilized when reacting with the other
components of the catalyst system.
Examples of such compounds are boron trichloride,
aluminium trichloride, aluminium monoethylchloride~
aluminium monoisobutyldichloride, aliminium tribromi-
~ de, tin tetrachloride, acetic acid~ benzoic acid, water,
; 15 etc.
The components (d) of the catalyst system are,
as already said~ thionyl chloride or hexachlorocyclo-
~;~ pentadiene.
The molar ratio between the components (b) and
(a) is usually high since the vanadium compound is
used in very little amountsO Said ratio is high than
10 : 1 and usually ranging from 50 : 1 to 100 : 1.
However, when the vanadium concentration is lower than
` ~ 5 . 10 5 mole/litre~ the Al/V ratio is preferably
ranging from 100 : 1 to 500 : 1. The best amount of
the vanadium compound is comprised between 1. 10 4 and
1. 10-5 mole/litre, whereas the aluminium compound is
comprised between 1 and 8.10-3 mole/litre.
The molar ratio between the components (c) and
3 (b) is critic. It~ when (c) is a multihalogenated
inorganic or organometal compound, may be de~ined as
6.
1046697
the global ratio between the gramatoms of halogen and
the aluminium ones contained in the reagents (b) and
(c). The ratio X/Al must be comprised between l and
1 25 or, preferably, between 1.05 and 1.15~
When (c) is a protonic acid or water, the ratio
between (b) and (c) is selected between 10 : 1 to
1 : 1 or~ preferably~ between 4 : 1 and 2 : 1
The molar ratio between the components (d) and
(b~ of the catalyst may widely vary, also in func-
tion of the particular compound (d) and the reaction
formalities. It is generally lower than l and is
preferably selected from the range of from 1 : 4
to 1 : 1 .
All aforesaid reactions are carried out in the
presence of a hydrocarbon that~ accord1ng to a
peculiar feature of the present invention, is of the
~ aromatic type. However, use may be made also of ~ -
- mixtures constituted by aromatic hydrocarbons with
aliphatic and cycloaliphatic hydrocarbons~ halogenated
aromatic hydrocarbons or mixtures thereof with the
- above-said ones or with other hydrocarbons containing
,~ .
halogens. Thereforeg even if a preferred use is made
of benzene or toluene, it is possible to use chloro-
benzene or mixtures constituted by benzene-cyclohexane,
toluene-n-heptane, chlorobenzene-tetrachloroethylene,
;~: . - .
etc.
:
- - The polymerization temperature widely ranges.
- - The operations are generally carried out at tempera-
--~; tures higher than the room one in order to prevent from
using expensive freezing cycles.
Therefore the most suitable range is comprised
from 50 to 100C, also if a wider range must be employ-
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104~6g~
ed so that the range wou] d be from 0 to 120C
The polymerizations are carried out under high
ethylene pressures ( 2 - 20 kg/cm ).
If necessary, hydrogen too is added in order to
regulate the molecular weights.
Ethylene-butadiene copolymers, obtainable accorcl-
ing to the aforedescribed process, are free from gel,
branchings and internal cyclization as it is possible
to check from infrared and nuclear magne-tic resonance
spectra and L`rom the hot complete solubility theleof
in hyclrocarbon and chlorohydrocarbon solvents.
The narrow molecular weight range, together with
a high chain linearity, is emphasized by the flowing
measurements in the meltecl state~ according to ASTM
1236-65T rule. The ratio between the flow indexes mea-
sured by applying weights of 21.6 kg (MFI21 6) and 2.16
kg (MFI 2 16)~ respectively, is said "shear sensitivityl'
and is, on the abovesaid copolymers, comprised between
10 and 50.
Lower the average molecular weight~ lower th s ratio
and, at the same molecular weight value, that ratio is- lower
if the polymer is more monodispersed and free from branch-
ings (R. Martinovitch~ P.J. Boche~ R.A. McCord~ SPE J. 16
1335 (1971) ).
The molecular weight distribution of the inventive
copolymers, expressed as M /M and determined by a gel-per-
meation chromatography (Polymer Fractionation, M.J.R. Cantow,
Academic Press N.Y7, 1967 ) ranges from 2 to 3.
The butadiene unit amounts (butadiene moles per 100
moles of both monomers) widely range, e.g. from 0.1 to more
than 10, and is regulated in view of the foreseen use.
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10~669~
The products having a higher interest for the
following transformation in cross-linked manufactured
articles, contains 0.5 to 5 ~0 by mol0 copolymerized buta-
diene.
Copolymers having less than 0.5 ~ butadiene under-
go a "degradation" in the presence of vulcanizing agents:
copolymers having more than 5 % unities are interesting~ -
besides their low cost~ because of their compatibility
with other high unsaturation polymers.
The 1,4-trans-butadiene units constitute, as from ~ ~
the infrared spectrography, at least 98 % of all copoly- -
merized butadiene. In fact bands awardable to unities
of the cis or 1,2 type are not relevant. The quantita-
tive determination of butadiene contained in copolymer
is therefore performed based on the band at 965 cm
according to known techniques.
The inter- and intramolecular statistic distribu-
- 20 tion of the inventive copolymer monomer unities is con-
: firmed by the fact that the polymerization raw product
,:
- may cross-link, whatsoever fraction is considered~ when
subJected to curing by means of conventional sulphur or
sulphur donors or quinone compounds base recipes~ with
or without accelerators or inert charges. The cross-
- linking rate is measured by the value of the maximum
- couple achieved at Zwick curing device or by the insoluble
portion, after 24 hours, in boiling xilene, and is express-
ed~as gel percentage. It is a function of the average
30 ~ molecular weight, molecular weight distribution, unsatu-
:
ration content of copolymer~ besides the employed vulca-
nizing mix~ and generally ranges from 30 to 90 % with
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10466~'7
respect tlle final product.
According to the inventive process, ethylene-buta-
diene copolymer is obtained with such high yields that it
is possible to eliminate the washing phase of the polymeri-
zation raw product~ since the few catalytic residuals may
remain in the polymer itself. In fact residual vanadium
is gen_erally lower than 50 ppm.
Ethylene-butadiene copolymers are highly crystal-
line on X-ray analysis. Their crystallinity is in the
interesting range~ the typical one of high density poly-
ethyleneO The lack of the crystallinity typical of 1,4-
-trans-polybutadiene~ also for contents higher than 10 %
of these structural unities, is a further evidence of
the statistic distribution of ethylene and butadiene
unities.
At last the copolymers density is not very diffe-
rent from the linear polyethylene one and ranges from
0.950 to 0.960 g/m2 (rule ASTM D 1505-68).
The cross-linked products obtainable from the
inventive ethylene-butadiene copolymers are interesting
because of several practical applicationsO
Inter alia we emphasize the preparation of stiff
foamed materials (very good insulating) and sound proof- -ing materials burning without any black smoke emission),
stiff containers~ piper, pipe coating jackets, etc.
When practically used, the cross-linked copolymers
have~ with respect to polyethylenes, higher mechanical -
characteristics, such as ultimate tensile strength and
, - the impact resistance (rule ASTM D 256/56)~ improved
stress-cracking resistance ( rule ~STM D 1693), low
decreasing of the flexibility modulus (rule ASTM D 747)
and a substantial inertia towards oils and solvents.
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1046697
Ethylene-butadiene copolymers, which are not cross-
linked~ may be utilized as intermediates in the prepara-
tion of difunctional olefin monomers following a suitable
demolition of the unsat~rated chain,
Some data of the properties till now listed~ as
also vulcanizing recipes and conditions, are reported
in the ~xamples hereinbefore reported~ supplied for the
mere purpose of better illustrating the invention without
limiting the same. :
EXAMPLE
Use was made of a steel autoclave:~ whose internal
walls were enameled having 5 1 capacity and provided :
.: with a mechanical stirrer, a circulating liquid thermo-
stating jacket and valves, one of which plunging, to be ::
15 used for the reagent feeding ; therein, through a suction~ .-
: was introduced a solution obtained from : :
- anhydrous toluene ml 1800
( 2 5)2 ml 1 35
( 2 5) 2 g o.l5
- 20 - butadiene g 40
After the thermostatation of the mixture at 600C,
ethyIene was introduced up to a pressure of 14 kg/cm2 and~
then~ hydrogen was fed till to a total pressure of 20
kg/cm .
A toluene solution (100 cm3) containing 52 mg of
dissolved vanadium triacetylacetonate was introduced by
means of a pump~ in few minutes. Then~ through the same
pump~ was introduced~ slowly over 20'~ a solution of o.6S
ml of SOC12 in 100 ml of toluene.
3 During the polymerization ethylene was fed, thus
keeping constant ab 20 kg/cm2 the tobal pressure~ at 600C.
11.
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i~4~69~
The test was stopped after 40' by the addition of
200 ml of methyl alcohol. The formed polymer was filtered
washed on filter with other methyl alcohol ( 2 l)and dried
in an oven at 50C and under vacuum.
G 115 were weighed of dry product having (IR analysis)
1.6 % by mole of 1.4-trans-butadiene units, MFI2 16 1 3
g/10'~ and MFI 21 6 = 51,1 g/10' (shear sensitivity = 39),
The copolymer was mixed with the following compounds
(gram for 100 grams of copolymer) :
- Zinc oxides 5
- Stearic acid
- 2,2'methylene-bis (4-methyl-
- -ter-butylphenol) A,0.2246
- - N-oxydiethylbenzothiazole-
-2-sulphenamide (NOBS ~ -
special) 1.5
- Dibenzothiazyl disulphide
(Wulkacit DM; trademarK) 0.5
- Sulphur 3
The mix was then press treated at 180C for 30 mi-
nutes.
The resulting product sho~ed a gel content of 65
and an impact resistance of 56 kg/cm (versus 9-,4 kg/cm
of the copolymer as such),
EXAMPLE 2
.
A test similar to the one of Example l was carried
out, by using the same apparatus and reactants but the
vanadium triacetylacetonate amount that was reduced to
,
17.5 mg.
The test was protracted over 30~. 91 ~ of polymer
were obtained (36.400 g for gram of metallic vanadium),
having :
12.
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~046697
- butadiene units (% by mole) 1.5
- MFI2 16 1-7 g/10
21.6 59.2 g/10
(shear sensitivity = 34.5)
The ~roduct was cross-linked according to Example
l~ thus obtaining 63 ~ gel.
EXAMPLE 3
Use was made of autoclave described in Example l: ~
therein was introduced a solution obtained from : `
- anhydrous toluene ml 1800
( 2 5)2 ml 1.35
( 2 5) 2 o .15
- butadiene g 40
The autoclave was thermostated at 600C (internal
temperature) and ethylene, up to a pressure of 16 kg/cm ,
and then hydrogen, up to atotal pressure of 20 kg/cm ,
were added.
Over 30~ was introduced a solution containing 35 mg
of vanadium triacetylacetonate and o.86 ml of SOC12 in
200 ml of toluene.
During the polymerization, consumed ethylene was
replaced.
The test time was 40~ , and 78 g of polymer was
, .
obtained.
~5 At IR analysis resulted a content of 1.4-trans-
butadiene units equal to 15 ~. MFI2 16 Z 1. 1 g/10
MFI21 6 = 4-5 g/10' (shear sensitivity = 37.1).
EXAMPLE 4
Use was made of 1 l steel autoclavs~ equipped with
3 mechanical stirrer, electrical thermoregulation~ reactant
input valves; therein was introduced the following solu~
13-
10466~7
tion :
- anhydrous toluene cm500
2 mg22
- butadiene g 12
The mixture was thcrmostated at 60C~ then added
with 0.45 ml of Al(C2H5)2Cl diluted in 50 ml of anhydrou6
toluene. Then was introduced~ through a metering pump
over 25'~ a solution formed by 10.5 mg of vanadium tri-
acetylacetonate and 0.28 ml of hexachlorocyclopentadien~
in 50 ml of anhydrous toluene.
The test time was 100 minutes~ during which con-
sumed ethylene was reinstated. :
The polymer~ isolated as abovesaid ( see Example l~
weighed 19.5 g and had the following characteristics :
- butadiene units % 1.7 (mole)
- MFI2 16 1.23 g/10~ .
- MFI21 6 51.1
(shear sensitivity = 41.6)
The copolymer cross-linked in the pressure of
- 20 sulphur and accelerators (according to the recipe and
. conditions of Example 1).
EXAMPLE 5 -
In the autoclave described in Example 4 were reactedt
- anhydrous toluene ml 500
- butadiene g 12
- Al(C2H5~2C1 ml 0.4
- Al(C2H5)C12 g -4
- ethylene Kg/cm2 16 at 60
- hydrogen kg/cm 4 at 60C
By keeping the working pressu~e at 20 kg/cm2 at 60C~
was introduced~ through a piston pump, a toluene solution
14.
104669'7
of hexachl~rocyclopentadiene in toluene (ml 0.28 in
ml 50), and~ then over 25 minutes, a solution of vanadyl
~ diacetylacetonate in toluene (8 mg in 50 ml).
The test was ~opped after 60' from the addition
of the vanadyl compound. G 17 of polymer were obtained~
having :
- butadiene units ~c (mole) 2.28
0.04 g/10
21.6 2.0 g/10
(shear sensitivity = So)
The polymer cross-linked for 78 % by means of sul-
phur and accelerators (conditions and recipe according to
; Example 1),
EXAMPLE 6
lS In the autoclave of Example 4 were introduced the
following reactants :
- anhydrous toluene ml 500
.: .
butadiene g 12
- Al(C2H5)2Br g 0.53
_ Al(C2H5)Br2 g o.o8
- ethylene kg/cm2 16 at 600C
- hydrogen kg/cm2 4 at 60
~ By keeping the autoclave at 600C under stirring~ was
slowly added (over about 25') a solution g.10.5 mg of
vanadium triacetylacetonate and 0.28 ml of hexachlorocyclo-
~ pentadiene in 100 ml of toluene.
-~ The polymerization run over two hours, during which
absorbed ethylene was fed.
G 28 of copolymer were obtained having a butadiene
unit content (~ by mole) equal to 1.5.
EXAMPLE 7
15.
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:. ~ . : .
~0~6~7
A test was carried out in the same autoclave of
Example 4 by employing the following reactants :
- anydrous benzene ml 300
- anhydrous cyclohexane ml 250
- butadiene g 12
- Al~C2H5)2Cl ml 0,4
- A1(C2H5)C12 g 0.05
~ thylene was fed up to a pressure of 16 kg/cm and
then hydrogen till to a total pressure of 90 kg/cm2 at
tO 60C.
The polymerization started by gradually adding a
solution of 10.5 mg of vanadium triacetylacetonate in
50 ml of cyclohexane over 25~.
The test was stopped after 70' and the polymer was ~ :
15 isolated according to the usual procedure g 7.5 being
obtained, having the characteristics :
- Butadiene units % (mole) = 1.24~ MFI2 16~5.39 g/10l~ :
- UFI21 6= 98.18 g/10' (shear sensitivity = 18.2). ~:
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