Plastic copolymers of propylene with linear dienes having conjugated double-bonds and process for preparing same

Disclosed are plastic copolymers of propylene with linear dienes having conjugated double bonds, in particular with butadiene, characterized by a molar ratio between the dienic units in configuration 1,2 and those in configuration 1,4 higher than 0.2, preferably higher than 1. Such copolymers are prepared by copolymerization of propylene with linear dienes in the presence of stereospecific catalysts comprising a halogen Ti compound supported on a Mg halide. The copolymers can be reacted with radically polymerizable monomers, thus obtaining functionalized products suited to be transformed into films having good adhesion characteristics.

BACKGROUND OF THE INVENTION 
From the scientific and patent literature it is known that it is possible 
to copolymerize propylene with 1,3-butadiene, in the presence of 
Ziegler-Natta catalysts, to obtain alternated or random copolymers. 
It is known as well that the products so obtained contain butadiene units 
whose configuration is always prevailing of the 1,4-cis or trans type (see 
for example W. Cooper in "The Stereo Rubbers", Saltman ed., John Wiley & 
Sohns, New York 1977 and annexed quotations). These materials, because of 
their having the double bond inserted in the main chain, are easily 
subject to thermal degradation and even more to oxidative degradation. 
Therefore, from the viewpoint of the product stability it would be of great 
interest to obtain copolymers having the butadiene linked in configuration 
1,2 and, by consequence, the double bond in the side chain. 
In fact it is known that the vinyl-type unsaturations give rise to 
scission. 
Furthermore, according to the art, the copolymerization of propylene with 
butadiene must be accomplished at very low temperatures, generally below 
0.degree. C., and the catalytic activity is only corresponding to a few 
grams of polymer per gram of titanium. 
THE PRESENT INVENTION 
It has now surprisingly been found that the use of proper catalyst systems 
permits, in particular polymerization conditions, to obtain, with high 
catalytic yields, plastic copolymers of propylene with dienes having 
conjugated double bonds, in particular with 1,3-butadiene, in which at 
least 20% of the unsaturations is of the vinyl type. 
The copolymers of propylene with butadiene which form the object of the 
present invention are characterized by: 
an aggregate content of 1,3-butadiene ranging from 0.1 to 15% by weight, 
preferably from 1 to 10% by weight; 
a molar ratio between the butadiene units in 1,2 configuration and the ones 
in 1,4 configuration higher than 0.2, preferably higher than 1; 
an amount of product soluble in xylene at 25.degree. C. lower than 20%, 
preferably lower than 15%. 
Such copolymers are particularly suited to the preparation of films having 
excellent physical-mechanical properties and a low weldability 
temperature. 
The copolymers of the present invention may contain, besides units from 
propylene and from 1,3-butadiene, also little amounts of units deriving 
from another olefinic monomer. 
Particularly advantageous has proved the use of ethylene, in amounts 
ranging from 0.1 to 5% by weight, in the copolymer, because it permits to 
improve at the same time the activity of the catalyst and the weldability 
temperature of the product. 
The process for preparing the new copolymers consists in polymerizing the 
propylene, in admixture with suitable amounts of a linear diene having 
conjugated double bonds, in particular 1,3-butadiene, optionally in 
admixture with ethylene and/or another alpha-olefin, in the presence of 
coordination catalysts comprising a titanium halide, carried on a 
magnesium halide, which are capable of promoting the stereoregular 
polymerization of propylene. 
Catalysts capable of promoting the steroregular polymerization of propylene 
means the catalysts capable of producing, under optimum conditions, 
polypropylene with an isotacticity index higher than 80%. 
Examples of particularly suited catalysts, as they are endowed with a high 
sterospecificity in propylene polymerization, are the ones described in 
U.S. Pat. Nos. 3,107,413; 3,107,414; 4,226,741; 4,277,589; European pat. 
appl. Nos. 0045975; 0045976; 0045977. 
In these patents, the high stereospecificity of the catalyst is due to the 
presence of electron-donors as modifiers of the Al-alkyl compound and/or 
of the solid component containing the Ti compound. In the case of U.S. 
Pat. No. 3,107,413, the electron-donor is an ester of an organic or 
inorganic oxygenated acid. Esters of benzoic acid, of p.toluic acid, etc. 
are examples of representative compounds. In the case of European patent 
applications Nos. 0045975, 0045976, 0045977, the electron-donor compound 
is a Si compound containing at least a Si-OR bond (R=hydrocarbon radical). 
Examples of these compounds are methyltriethoxysilane, 
phenyltriethoxysilane, ethyltriethoxysilane. 
Polymerization can be conducted continuously or discontinuously in liquid 
propylene or in the presence of an inert diluent, such as hexane, heptane, 
toluene, or in the gas phase or in a mixed liquid-gas phase. 
Particularly advantageous is the copolymerization in liquid propylene in 
the presence of solid catalyst components having a narrow particle size 
distribution and a spheroidal form. 
With a view to obtaining copolymers having the desired configuration of the 
units deriving from the diene it is essential to operate under molar 
conditions between alkyl alluminium and Lewis base (in the catalyst 
systems supported on magnesium halide, the Lewis base is utilized to 
impart stereospecificity to the system) such that the catalyst system may 
operate in a stereospecific manner, i.e. it may be capable of polymerizing 
the propylene to a polymer consisting for the most part of isotactic 
polypropylene. 
Such ratio depends, as is known, on the catalyst system type. 
With systems like those described in European patent applications Nos. 
45,975, 45,976, 45,977, the ratio is generally lower than 40, preferably 
lower than 20, while in the case of systems like the ones described in 
U.S. Pat. Nos. 3,107,414, 4,226,741 and 4,277,589, said ratio is lower 
than 6, preferably lower than 4. 
Also the polymerization temperature critically influences the polymer 
microstructure. 
Such temperature generally ranges from 40.degree. C. to 100.degree. C., 
preferably it ranges from 60.degree. C. to 80.degree. C. 
The aluminium alkyl concentration is not critical; generally it is 
preferred to operate in the concentration range from 1 to 50 m.moles/l. 
The adjustment of the copolymer molecular weight occurs in the presence of 
chain transferors of the conventional type, such as for example hydrogen 
and ZnEt.sub.2 ; the inherent viscosity is generally adjusted in a range 
of from 0.1 to 6 dl/g, preferably from 1 to 4 dl/g. 
The concentration of the chain transferor has no appreciable effect on the 
copolymer microstructure. 
The copolymer formed in the polymerization reaction can be optionally 
purified from the catalyst residues according to known techniques, for 
example by treatment with alcohols, propylene oxide and the like. 
Furthermore, the copolymers can be cross-linked or modified by reactions 
typical of the unsaturated polymers, such as for example epoxidation, 
sulphonation, condensation with maleic anhydride, radicalic grafting of 
vinyl monomers, acrylic monomers, silanes, co-vulcanization with other 
unsaturated polymers etc. 
In German application OS No. 2,434,668 there is described the grafting 
reaction conducted in suspension, in the presence of a radicalic starter 
and of a polymerizable monomer, of propylene/1,3-butadiene copolymers 
prepared with catalytic system TiCl.sub.3 AA and AlEt.sub.2 Cl, having the 
butadiene units prevailingly in position 1,4. 
The reaction is conducted in the presence of specific solvents, such as 
ethylacetate, methylacetate; aromatic solvents such as benzene, toluene, 
xylene etc. and chlorinated solvents, such as chlorobenzene, 
chlorocyclohexane, etc. 
Conversely, the reaction does not occur in the presence of aliphatic 
solvents, such as hexane, heptane, kerosene, etc. Of course, this is a 
drawback, because just these solvents are the ones generally utilized in 
the commercial-scale processes for polymerizing propylene. 
In contrast with what is described in the cited patent, it has been found 
that the copolymers of the invention can be functionalized, either in 
solution or in suspension, also in the presence of aliphatic solvents and 
also in the dry state. 
Furthermore, it has been found that the grafting reaction takes place even 
in the absence of peroxides and of other radicalic starters. 
As examples of employable starters there may be cited all those which are 
polymerizable in radicalic manner, and in particular the vinyl monomers, 
such as acrylic acid, methacrylic acid and the esters thereof; 
glycidylacrylate and glycidylmethacrylate; vinylacetate; acrylamide; 
styrene; maleic anhydride and derivatives thereof; acrylonitrile; 
maleimide; silanes, such as vinyltriethoxy-silane and 
vinyltrimethoxy-silane, etc. 
As possible radicalic starters there may be cited the peroxides, such as 
dibenzoyl peroxide, di-tert. butyl-peroxide, di-cumyl-perioxide, etc. the 
hydroperoxides, such as tert.dibutyl-hydroperoxide, cumylhydroperoxide, 
etc.; the peroxyesters, peroxyethers, peroxyketones, etc.; the 
azonitriles, such as azo-bis-isobutyronitrile, etc. 
The amount of polymerizable monomer may range from 0.5 to 100% by weight 
with respect to the copolymer to be modified. 
The amount of starter is generally lower than 5% by weight with respect to 
the copolymer, preferably lower than 1% by weight. 
Starting product concentration and reaction temperature depend on whether 
the grafting reaction is to be carried out in suspension or in solution. 
In the former case it is preferable to operate with concentrations ranging 
from 100 g to 500 g of polymers per liter of diluent at temperatures 
ranging from 60.degree. C. to 90.degree. C. 
In the latter case it is preferably to work with polymer concentrations 
lower than 300 g of polymer per liter of solvent at temperatures ranging 
from 100.degree. C. to 200.degree. C. 
The reaction time may range from 30 minutes to 10 hours, preferably from 1 
hour to 5 hours. 
The resulting functionalized copolymers are particularly suitable for being 
transformed into films having a good adhesion to metals or other inorganic 
substrates and polar polymers, or for being utilized as compatibilizing 
agents between polypropylene and the materials cited herein before.

EXAMPLE 1 
A stainless steel 1.3-l autoclave, equipped with a magnetic stirrer and 
running at 400 rpm was used. 
66 g of 1,3-butadiene, 230 g of propylene and 500 Nml of hydrogen were 
introduced into the autoclave in succession. 
Into a separate cylinder there were introduced 5 ml of hexane, 0.114 g of 
solid catalytic component prepared according to example 20 of European 
patent application No. 0045977, 0.6 g of aluminium triethyl (TEA) 
dissolved in 4 ml of hexane and 0.171 g of diphenyl-dimethoxysilane 
(DPMS). The catalytic complex was then injected into the autoclave by 
means of propylene pressure. The temperature was then raised to 70.degree. 
C. and kept constant allthrough the reaction. During polymerization, a 
proper propylene amount was continuously fed so as to keep the pressure in 
the autoclave constant. 
4 hours after having added the catalyst complex, the reaction was stopped 
by addition of a few ml of an acetonic solution containing the stabilizer 
(Irganox 1010 and BRT). The unreacted monomers were removed by degassing, 
and the polymer was dried in an oven at 60.degree. C. in a nitrogen 
stream. 
The polymer properties and the polymerization conditions are indicated in 
Table I. 
EXAMPLES 2 TO 7 AND COMATIVE EXAMPLES 1 AND 2 
It was operated according to the modalities of example 1, with the 
exception that the molar ratio between TEA and DPMS was changed. 
From the results recorded on Table I, the critical effect of the ratio 
between aluminium alkyl and the electron-donor compound on the copolymer 
microstructure is clearly apparent. 
In particular, when such molar ratio was higher than 80, the butadiene 
amount present in configuration 1,4 and the percentage of xylene-soluble 
product drastically increase. 
COMATIVE EXAMPLE 3 
It was operated according to the general modalities of example 1. In this 
case, however, the monomers and the catalytic complex were introduced into 
the autoclave at 0.degree. C. and such temperature was maintained also 
during the polymerization. 
Results and reaction conditions are indicated on Table II. 
EXAMPLES 8 TO 12 AND COMATIVE EXAMPLES 4 AND 5 
In these examples, indicated in Table II, the general operative conditions 
of example 4 were employed, with the exception that the polymerization 
temperature was modified. 
The obtained results clearly show the critical effect of the reaction 
temperature on the copolymer microstructure. 
In particular, when such temperature was lower than 40.degree. C., products 
having a high percentage of butadiene in configuration 1,4 and a high 
amount of xylene-soluble material was obtained. 
EXAMPLES 13 TO 15 
The same operative modalities of example 4 were substantially adopted, with 
the exception that the butadiene concentration in the reaction mixture was 
changed. 
From the results indicated in Table III it can be noticed that the 
comonomer concentration is not critical for the copolymer microstructure. 
EXAMPLES 16-17 
The same operative modalities of example 4 were substantially adopted. In 
this case, however, the copolymerization of propylene with 1,3-butadiene 
was carried out in the presence of a proper ethylene amount. During the 
polymerization, a propylene/ethylene mixture, having a varying composition 
depending on the copolymer composition to be obtained, was fed, in order 
to mantain the pressure in the autoclave constant. 
Results and operative modalities are recorded on Table IV. 
On the basis of the results obtained it is inferable how the utilization of 
ethylene, in addition to propylene, permits to obtain copolymers having a 
melting temperature lower than the one of the copolymers obtained with 
propylene only, the amount of xylene-soluble material being equal. 
EXAMPLES 18-19 AND COMATIVE EXAMPLE 6 
The same autoclave and the same operative modalities of example 1 were 
employed. In this case, however, a catalytic system consisting of a solid 
component, prepared according to example 1 of U.S. Pat. No. 4,226,741, and 
of a co-catalyst consisting of a mixture of aluminium triisobutyl and 
trinormalbutyl (MAB) and methyl para-toluate (MPT), was used. 
The results reported in Table V show how in this case the molar ratio 
between aluminium alkyl and electron-donor compound must be lower than 6. 
EXAMPLE 20 
As a product to be functionalized there was used a propylene/1,3-butadiene 
copolymer in flakes having the following characteristics: butadiene in 1,2 
configuration=2.6% by weight, butadiene in 1,4 configuration=2.3% by 
weight, melt flow rate=5.6 g/10'. 
Into a four-neck flask having a 3-liter capacity, equipped with a stirrer, 
a cooler with nitrogen inlet pipe, there were introduced, in succession, 
1,000 ml of normalheptane and 150 g of copolymer. Nitrogen was made to 
bubble through the suspension for about 1 hour, whereafter the mass 
temperature was brought, always under a nitrogen atmosphere, to 80.degree. 
C. in about 30 minutes, by means of an oil thermoregulated bath. 
Subsequently, under stirring, there were fed 10 g of maleic anhydride in 
powder and, after 5 minutes, 0.45 g of benzoyl peroxide. The reaction was 
carried on during 4 hours at a constant temperature of 80.degree. C. 
The polymer was then filtered and hot washed 5 times with 1 l of acetone. 
There was obtained a product containing 0.6% by weight of maleic anhydride, 
determined by titration, and having a M.F.R. of 0.2 g/10'. 
One gram of the obtained copolymer was compression molded, at a temperature 
of 200.degree. C. during 10 minutes and at a pressure of 200 kg/cm.sup.2, 
between two aluminium sheets having respectively the following sizes: 
20.times.20 cm and 20.times.30 cm. From the resulting laminate there were 
obtained specimens having a width of 2.5 cm,--which, subjected to traction 
at 130.degree. C. at a speed of 10 cm/min., exhibited an adhesive strength 
equal to 3.3 kg/cm. 
EXAMPLE 21 
Example 20 was repeated, with the exception that no peroxide was fed during 
the reaction. 
A copolymer containing 0.65% by weight of maleic anhydride and having a 
M.F.R. of 4.18 g/10' was obtained. 
The adhesive strength to aluminium was equal to 3.2 kg/cm. 
EXAMPLE 22 
Example 20 was repeated with the exception that acrylic acid (10 g) instead 
of maleic anhydride was employed. 
The copolymer obtained, after having been washed 5 times with 1 l of hot 
methanol each time, exhibited a content of 2.1% by weight of acrylic acid 
(determined by titration). 
Such product, having a M.F.R. of 0.3 g/10', exhibited an adhesion to 
aluminium equal to 2.5 kg/cm. 
EXAMPLE 23 
Example 22 was repeated, with the exception that azo-bis-isobutyronitrile 
(0.45 g) as radicalic starter was employed instead of benzoyl peroxide. 
A copolymer containing 1.76% by weight of acrylic acid and having a M.F.R. 
of 0.02 g/10' was obtained. 
The adhesive strength of such product to aluminium was equal to 2.9 kg/cm. 
EXAMPLE 24 
Example 22 was repeated, with the exception that no radicalic starter was 
fed during the reaction. 
There was obtained a copolymer containing 0.1% of acrylic acid, having a 
M.F.R. of 4 g/10' and an adhesive strength to aluminium equal to 3.2 
kg/cm. 
EXAMPLE 25 
Example 20 was repeated, with the exception that glycidylacrylate (10 g) 
was employed as a modifier instead of maleic anhydride. 
There was obtained a copolymer containing 1.5% by weight of 
glycidylacrylate (determined by I.R.), having a M.F.R. of 0.01 g/10' and 
an adhesive strength to aluminium equal to 2.4 kg/cm. 
EXAMPLE 26 
A propylene/1,3-butadiene copolymer having the following characteristics: 
butadiene in 1,2 configuration=2.5% by weight, butadiene in 1,4 
configuration=1.4% by weight, M.F.R.=3.73 g/10' was employed as starting 
product. 
The grafting reaction was carried out by means of the same equipment 
described in example 20. In this case, however, the starting copolymer was 
dissolved in kerosene under the following conditions: concentration=200 g 
of polymer/l of solvent, temperature=190.degree. C. 
Subsequently, maleic anhydride was fed in an amount equal to 33% by weight 
with respect to the copolymer, and the reaction was carried on during 7 
hours in the absence of the radicalic starter. 
The reaction mass was cooled, the polymer was coagulated with acetone and 
hot washed 5 times with acetone. 
The resulting copolymer contained 1.62% by weight of maleic anhydride. 
Such product, having a M.F.R. of 9.5 g/10', exhibited in adhesion to 
aluminium equal to 3.4 kg/cm. 
TABLE I 
__________________________________________________________________________ 
EXAMPLE No. 1 2 3 4 5 6 7 1/Cfr 
2/Cfr 
__________________________________________________________________________ 
TEA/DPMS moles 0.5 
1 3 7.5 
20 40 60 80 .infin. 
H.sub.2 Nml 500 
500 
500 
300 
300 
300 
300 
200 
150 
Solid catalyst component g 
0.114 
0.094 
0.102 
0.125 
0.101 
0.094 
0.07 
0.082 
0.086 
Polymer g 110 
126 
178 
175 
168 
170 
128 
106 
45 
Yield kg Pol/g Ti 
43 60 77 62 74 80 81 57 28 
##STR1## 2.7 1.0 
2.4 0.9 
2.2 1.0 
2.3 1.9 
1.9 2.5 
1.3 4.0 
1.2 4.8 
0.95 7.5 
1.3 26 
Melting point .degree.C. 
143.5 
143 
144 
138.5 
140.5 
140.5 
140 
141 
120-134 
Crystallization point .degree.C. 
94 93 93 94 93 93 89.5 
87 93 
X-ray crystallinity % 
55 56 50 53 47 51 
Acetone solubility % b.w. 
3.6 
2.3 
1.2 
1.4 
2.3 
2.6 
2.3 
2.6 
9.9 
Xylene solubility % b.w. 
3.8 
6.4 
7.7 
10.4 
8.3 
14.7 
16.6 
33.9 
61.6 
[.eta.].sub.THN.sup.135.degree. C. dl/g 
1.8 
1.75 
1.7 
2.5 
2.4 
1.7 
1.6 
1.4 
1.3 
M.F.R. g/10' 4.4 
4.6 
4.7 
0.77 
1.02 
6 7 15.6 
-- 
__________________________________________________________________________ 
Polymerization conditions: 
1.3 liter autoclave TEA = 0.6 g. Propylene = 230 g Butadiene = 66 g 
Temperature = 70.degree. C. Time = 4 hours 
Pressure = 24.5 kg/cm.sup.2 gauge. 
TABLE II 
______________________________________ 
EXAMPLE 
No. 3 Cfr 4 Cfr 5 Cfr 
8 9 10 12 
______________________________________ 
Fed 223 190 202 209 218 230 249 
propylene g 
Fed buta- 
96 59 61 63 64 66 70 
diene g 
H.sub.2 Nml 
300 200 250 300 500 300 400 
Solid catalyst 
0.517 0.685 0.24 0.129 
0.114 
0.125 
0.053 
component g 
Polymeriza- 
0 20 40 50 60 70 80 
tion temper- 
ature .degree.C. 
Pressure 3.8 7.4 12.95 
15.9 20.05 
24.5 30.4 
kg/cm.sup.2 g. 
Polymer g 
17 90 106 98 176 175 120 
Yield kg 1.4 5.8 19.6 34 69 62 100 
Pol/g Ti 
##STR2## 
3.4 38.3 0.8 14.4 
1.5 8.4 
1.7 6 
1.97 1.96 
2.3 1.90 
1.4 0.7 
Melting point .degree.C. 
139/147/153 
153.5 151 147.5 
146 138.5 
144 
Acetone solu- 
4.9 3.2 3.0 2.7 1.5 1.4 1.4 
bility % b. w. 
Xylene solu- 
21 19 16.1 12.8 10.5 10.4 3.4 
bility % b. w. 
X-ray crystal- 
60 49 49 50 47 53 53 
linity % 
[.eta.].sub.THN.sup.135.degree. C. 
1.8 1.5 1.6 1.55 1.6 2.5 2.1 
dl/g 
M.F.R. g/10' 
5.1 11.4 7.9 9.2 7.2 0.77 2.1 
______________________________________ 
TABLE III 
______________________________________ 
EXAMPLE No. 13 14 15 
______________________________________ 
Fed propylene g 260 230 226 
Fed butadiene g 31 66 84 
H.sub.2 Nml 300 300 300 
Solid catalyst component 
0.0347 0.0743 0.104 
Pressure kg/cm.sup.2 g. 
27 25.5 23.5 
Polymer g 111 114 150.5 
Yield kg pol./ g Ti 
146 70 64 
##STR3## 1 0.9 2.05 1.4 2.6 2.3 
Melting point .degree.C. 
147 142 137 
X-ray crystallinity % 
60 47 52 
Acetone solubility % b.w. 
1.4 1.9 1.6 
Xylene solubility % b.w. 
3 5.1 9.5 
[.eta.].sub.THN.sup.135.degree. C. dl/g 
1.7 1.4 2.2 
M.F.R. g/10' 6.1 12.5 1.5 
______________________________________ 
Polymerization conditions: 
TEA = 0.6 g TEA/DPMS = 7.5 (moles) Temperature = 70.degree. C. Time = 
hours 
TABLE IV 
______________________________________ 
EXAMPLE No. 16 17 
______________________________________ 
Fed propylene g 230 230 
Fed butadiene g 66 66 
Fed ethylene g 0.5 1.8 
H.sub.2 Nml 500 500 
Solid catalyst component g 
0.074 0.042 
Ethylene in feeding % by weight 
1.4 4.9 
mixture (1) 
Pressure kg/cm.sup.2 g. 
24.75 24.8 
Polymer g 185 122 
##STR4## 1.8 1.2 1.7 1.2 
Melting point .degree.C. 
138.5 124 
Acetone solubility % by weight 
3.2 0.8 
Xylene solubility % by weight 
8.2 13.8 
[.eta.].sub.THN.sup.135.degree. C. dl/g 
1.7 1.5 
M.F.R. g/10' 5.1 4.7 
______________________________________ 
(1) During the reaction, a propylene/ethylene mixture is continuously fed 
in order to maintain the pressure constant 
TABLE V 
______________________________________ 
EXAMPLE No. 18 19 Cfr 6 
______________________________________ 
MAB/MPT (moles) 2.5 3 6 
H.sub.2 Nml 1500 1000 200 
Solid catalyst comp. g 
0.089 0.1 0.044 
Temperature .degree.C. 
70 70 70 
Pressure kg/cm.sup.2 g. 
25.65 25.2 24.5 
Polymer g 125 166 136 
Yield kg Pol/g Ti 81 96 179 
##STR5## 0.75 0.7 
0.66 1.0 
0.6 8.3 
Melting point .degree.C. 
143.5 143 130/139 
X-ray crystallinity % 52 
Acetone solubility % by weight 
2 2.7 6.5 
Xylene solubility % by weight 
6.1 6.0 46.1 
[.eta.].sub.THN.sup.135.degree. C. dl/g 
1.6 2.0 1.35 
M.F.R. g/10' 8.8 2.35 12 
______________________________________