Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-03-20
2004-10-12
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S240000
Reexamination Certificate
active
06803415
ABSTRACT:
The present invention relates to flexible compositions based on propylene polymers. More particularly, it concerns flexible compositions based on random copolymers of propylene and on plastomers having no elastomeric fractions.
Flexible polymeric compositions and polymers have many outlets in sectors as varied as films, sheeting, the covering of soils, cables, etc. Plasticized vinyl chloride polymers are often used for these applications. However, these can cause problems connected to migration of the plasticizers used to provide their flexibility, or else connected to the emission of chlorinated products when they are incinerated.
An alternative previously proposed is recourse to what are known as flexible propylene polymers, such as block copolymers of propylene containing semi-crystalline and/or crystalline fractions and elastomeric fractions (cf. for example EP-A-373660 and EP-A-416379). Another previous proposal is to prepare flexible compositions by mixing block copolymers of propylene containing elastomeric fractions with plastomers consisting of copolymers of ethylene with alpha-olefins prepared with participation of metallocene catalysts (WO 98/54260).
It is an object of the present invention to provide novel flexible compositions based on propylene polymers having no elastomeric fractions. The invention therefore relates to flexible compositions based on propylene polymers having no elastomeric fractions comprising:
A) from 10 to 90 parts by weight of random copolymer of propylene and at least one comonomer selected from ethylene and C
4
-C
8
alpha-olefins having a melting point of at least 100° C. and not exceeding 140° C. and a flow index measured at 230° C. under a weight of 2.16 kg (ASTM standard D1238, 1986) of from 0.5 to 15 g/10 min, and
B) from 90 to 10 parts by weight of plastomer prepared with participation of a metallocene catalyst and consisting of a random copolymer of ethylene and at least one C
3
-C
10
alpha-olefin having a density of from 0.860 to 0.920 g/cm
3
, a melt flow index measured at 190° C. under a weight of 2.16 kg (ASTM standard D1238, 1986) of from 0.5 to 30 g/10 min, and a molecular mass distribution M
w
/M
n
of at most 4.
The overall content of monomeric units derived from ethylene and/or from C
4
-C
8
alpha-olefins in the random propylene polymer A) is generally between 3 and 20% by weight. The comonomer(s) entering with propylene into the composition of the random copolymer A) is/are generally selected from ethylene and C
4
-C
6
alpha-olefins. Preference is given to ethylene, butene and hexene and in particular to ethylene and butene.
For the purposes of the present invention, the content of monomeric units derived from ethylene and/or from C
4
-C
8
alpha-olefins in the random copolymer A) is determined by FOURIER-transform IR spectrometry. In particular, the content of monomeric units derived from ethylene is determined using the absorption bands at 732 cm
−1
and 720 cm
−1
, and the content of butene is determined using the band at 767 cm
−1
.
The random copolymers of propylene A) used in the compositions according to the invention advantageously have a melting point of at least 105° C., mostly not exceeding 135° C.
One first family of random copolymers of propylene A) which are well suited to preparation of the flexible compositions according to the invention consists of copolymers of propylene and ethylene containing from 3 to 10% by weight, preferably from 3 to 6% by weight, and more particularly from 3.5 to 5.5% by weight, of monomeric units derived from ethylene. This family of random propylene copolymers provides flexible compositions having excellent heat resistance (retention of flexibility at high temperature).
Among this first family of random copolymers preference is given to copolymers whose melting point (Tf) complies with the following relationship
Tf
≦157.6° C.−
x
5° C. (1)
where x is the percentage by weight of ethylene, based on copolymer A)
A second family of random propylene copolymers A) which is well suited to preparation of the flexible compositions according to the invention consists of the copolymers of propylene and butene containing from 14 to 20% by weight of monomeric units derived from butene. This family of random propylene copolymers provides compositions with higher flexibility than the ethylene copolymers mentioned above, but their heat resistance is slightly lower.
Among this second family of random copolymers of propylene A) good results are given by the copolymers whose melting point (Tf) complies with the relationship (2) below:
Tf<
158° C.−
y
1.78° C. (2)
in which y is the percentage by weight of butene, based on the copolymer A).
A third family of random copolymers of propylene A) which are well suited to preparation of the flexible compositions according to the invention consists of terpolymers of propylene, ethylene and butene containing from 0.5 to 2.5% by weight of monomeric units derived from ethylene and from 5 to 19.5%, preferably from 5 to 15%, by weight of monomeric units derived from butene.
In the case of this third family, use is most often made of polymers complying with the relationship (3)
Tf<
159.3° C.−
x
7.87° C.
−y
1.98° C.−0.43
xy° C.
(3)
in which x and y are respectively the % figures by weight for ethylene and butene.
The random propylene copolymers A) which are very particularly preferred for the purposes of the present invention are random copolymers of propylene and ethylene.
The random copolymers of propylene A) generally have a flexural modulus (EMod) measured at 23° C. in accordance with the ASTM standard D790M of from about 400 to 800 MPa. They advantageously have a flow index measured at 230° C. under a weight of 2.16 kg (ASTM standard D1238, 1986) not exceeding 10 g/10 min. Preference is also given to random copolymers of propylene A) which have uniform distribution of the monomeric units derived from the (isotactic) comonomer(s).
The random copolymers of propylene A) entering into the flexible compositions according to the invention may be prepared by any known process for the copolymerization of propylene with ethylene and/or alpha-olefins, for example by a process in the gas phase, or else in dispersion in the liquid phase in liquid monomer, and making use of any known Ziegler-Natta catalytic system of sufficient activity and productivity capable of polymerizing propylene stereospecifically and allowing the required amounts of ethylene and/or alpha-olefin to be incorporated into the polymer.
Preferred random copolymers (A) are advantageously obtained by copolymerization of propylene and ethylene and using catalytic systems comprising a solid based on titanium trichloride, an alkylaluminium compound, and optionally an electron donor. These catalytic systems have in particular been described in the patent applications EP-A-0261727 and EP-A-0334411, and in the patents U.S. Pat. Nos. 5,204,305 and 4,210,729 (SOLVAY POLYOLEFINS EUROPE-BELGIUM). For a given overall content of ethylene, the random copolymers of propylene and ethylene prepared with participation of these catalytic systems, when compared with copolymers prepared with participation of what are known as supported catalysts, have a more random character, reduced oligomer content, and better powder morphology.
Very particularly preferred random copolymers of propylene and ethylene comply with the equation:
[
C
2×5
+]≦0.0094
[C
2×3
]
2
−0.0054
[C
2×3
]+0.0375
in which [C
2×5
+] and [C
2×3
], expressed in g/kg and evaluated by infrared absorption spectrometry are respectively:
[C
2×5
+]: the content of ethylenic units corresponding to the insertion of two, or more than two, ethylenic units between two propylenic units, measured at 720 cm
−1
, and
[C
2×3
]: the content of ethylenic units corresponding to the insertion of one ethylenic unit between two propylenic units, m
Costa Jean-Louis
Mikielski Raymond
BP Belgium
Galloway Norval B.
Nutter Nathan M.
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