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
2003-01-23
2004-09-28
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...
C525S192000, C525S194000, C525S232000, C525S240000, C525S241000
Reexamination Certificate
active
06797778
ABSTRACT:
The invention relates to the use of modified olefin polymers based on modified propylene polymers for producing polyolefin products with simultaneously high requirements for toughness and strength and heat resistance.
Polyolefin products based on propylene polymers with good toughness properties are known.
The toughness of products made of propylene polymers can be improved by using polypropylene blends which comprise elastomers, such as polyisobutylene (Martucelli, E., Polymer 24(1983), 1458), ethylene-vinyl acetate copolymers [Thomas, S., Kautschuk-Gummi-Kunststoffe (Rubbers and Plastics) 40(1987), 665-671 EPR [Greco, R., Polymer 28(1987), 1929-1936], EPDM [Karger-Kocsis, J., Polymer 23(1982), 699-705] or copolymers made of ethylene and of higher &agr;-olefins [Yu, T., SPE-ANTEC'94, 2439-2442]. The disadvantage of these melt blends is a loss of strength and heat resistance with increasing elastomer content.
It is known to improve the strength and heat resistance in PP/EPDM blends by irradiation with electrons [Gisbergen, J., Polymer 30(1989)12, 2153-2157] or in PP/EVA blends [Thomas, S., Kautschuk-Gummi-Kunststoffe 40(1987), 665-671] and, respectively, in blends made of polypropylene and ethylene-propylene rubber (U.S. Pat. No. 5,459,201) by kneading in the presence of peroxides.
It is also known to react ethylene polymers, propylene polymers, such as propylene homopolymers or elastomeric propylene-ethylene copolymers or mixtures of these, with bifunctionally ethylenically unsaturated compounds, such as isoprene, in the presence of peroxides in the melt (EP-A1-0 874 009).
Impact-modified blends made of polypropylene, of propylene copolymers with ethylene and/or of higher &agr;-olefins and of elastomeric copolymers made of ethylene and propylene and/or of higher &agr;-olefins, which are prepared by multistage polymerization, are also known (EP-A1-0 680 980; EP-A1-0 942 020).
Polyolefin products with simultaneously high requirements for toughness and strength and heat resistance have until now required the addition of large amounts of additives (e.g. 10% by weight of talc as filler or reinforcing material) to establish the required mechanical properties.
The object of the present invention is to provide polyolefin products which satisfy the requirement profile described above and do so using, in order to establish the required mechanical properties, an amount of additives reduced compared with that used in the prior art.
According to the invention, this object is then achieved by using modified olefin polymers based on modified propylene polymers which olefin polymers have melt indices of from 8 to 100 g/10 min at 230° C./2.16 kp and are obtainable by activating a polyolefin composition comprising
X % by weight of a semicrystalline propylene homopolymer and/or of a semicrystalline copolymer made of from 88 to 99.5% by weight of propylene and from 12 to 0.5% by weight of ethylene and/or an &agr;-olefin of the general formula CH
2
═CHR, where R is a linear or branched alkyl radical having from 2 to 8 carbon atoms, (100-X) % by weight of an elastic copolymer made of from 20 to 70% by weight of ethylene and from 80 to 30% by weight of propylene and/or an &agr;-olefin of the general formula CH
2
═CHR
1
, where R
1
is a linear or branched alkyl radical having from 2 to 8 carbon atoms,
at elevated temperature with peroxides and reacting the activated polyolefin composition with 0.1 to 10% by weight, based on the polyolefin composition, of volatile bifunctional monomers,
for the production of polyolefin products with simultaneously high requirements for toughness and strength and heat resistance and having the following combinations of properties
KM
1
, KR
1
, ZM
1
, WF
1
or
KM
2
, KR
2
, ZM
2
, WF
2
or
KM
3
, KR
3
, ZM
3
, WF
3
where
KM
1
≧50, KR
1
≧50, ZM
1
≧350, WF
1
≧120 and
KM
2
≧25, KR
2
≧40, ZM
2
≧700, WF
2
≧135 and
KM
3
≧10, KR
3
≧30, ZM
3
≧1000, WF
3
≧145 and where
KM is Charpy impact strength at −20° C. (kJ/m
2
) to DIN 53453
KR is Charpy impact strength at +23° C. (kJ/m
2
) to DIN 53453
ZM is tensile modulus at 23° C. (MPa) to DIN 53457/ISO 527
WF is Vicat A softening point (° C.) to ISO 306,
and where X takes the values
X
1
=from 60 to 70 for the combination of properties KM
1
, KR
1
, ZM
1
, WF
1
;
X
2
=from 70 to 78 for the combination of properties KM
2
, KR
2
, ZM
2
, WF
2
,
X
3
from 78 to 85 for the combination of properties KM
3
, KR
3
, ZM
3
, WF
3
.
Surprisingly, it has been found that mixtures made of semicrystalline propylene polymers and of elastomeric ethylene copolymers in defined mixing ratios, which have been modified by reacting with bifunctional monomers in the presence of free-radical generators, are suitable for the polyolefin products with high requirements for toughness, strength and heat resistance.
In this specification the terms “bifunctional monomers” and “bifunctionally unsaturated monomers” have the same meaning, i.e. monomers having (at least) two double bonds.
The novel polyolefin products are preferably produced using modified olefin polymers prepared by
a) mixing the polyolefin composition, which is in a particulate shape, with from 0.05 to 3% by weight, based on the polyolefin composition used, of acyl peroxides, alkyl peroxides, hydroperoxides, peresters and/or peroxycarbonates as free-radical generators capable of thermal decomposition, if desired diluted with inert solvents, with heating to 30-100° C.,
b) sorption of volatile bifunctional monomers by the particulate polyolefin composition from the gas phase at a temperature T(° C.) of from 20 to 120° C., where the amount of the bifunctionally unsaturated monomers is from 0.01 to 10% by weight, based on the polyolefin composition used, and then
c) heating and melting the particulate polyolefin composition in an atmosphere comprising inert gas and/or the volatile bifunctional monomers, and from 110 to 210° C., whereupon the free-radical generators capable of thermal decomposition are decomposed and then
d) heating the melt to 220-250° C. in order to remove unreacted monomers and decomposition products,
e) pelletizing the melt in a manner known per se.
In another advantageous embodiment, the novel polyolefin products are produced from mixtures made of from 85 to 99% by weight of a modified olefin polymer with a melt index of from 8 to 100 g/10 min at 230° C./2.16 kp and from 1 to 15% by weight of an unmodified propylene polymer with a melt index of from 0.5 to 100 g/10 min at 230° C./2.16 kp.
It is preferable here for the unmodified propylene polymers to be formed from propylene homopolymers, from copolymers made of propylene with &agr;-olefins having from 2 to 18 carbon atoms, preferably from random propylene copolymers, from propylene block copolymers, from random propylene block copolymers and/or from elastomeric polypropylenes, or from mixtures of the polypropylenes mentioned.
Particularly suitable propylene homopolymers which may, if desired, be present in the novel polyolefin products are propylene homopolymers with bimodal molar mass distribution, weight-average molar masses M
w
of from 500,000 to 1,500,000 g/mol, number-average molar masses M
n
of from 25,000 to 100,000 g/mol and M
w
/M
n
values of from 5 to 60, which were prepared in a reactor cascade using Ziegler-Natta catalysts or metallocene catalysts.
In the preparation of the modified olefin polymers present in the polyolefin products it has proven advantageous to modify polyolefin particles directly emerging from the polymerization plant.
It is preferable for the modified olefin polymers to comprise chemically bonded butadiene, isoprene, dimethylbutadiene, divinylbenzene or mixtures of these as bifunctionally unsaturated monomers.
The average sorption time &tgr;
s
[s] of the volatile bifunctional monomers on the particulate polyolefin composition is advantageously from 10 to 1000 seconds, preferably from 20 to 800 seconds, particularly preferably from 60 to 600 seconds.
It is a
Raetzsch Manfred
Reichelt Norbert
Rohaczek Gerald
Borealis GmbH
Jordan and Hamburg LLP
Nutter Nathan M.
LandOfFree
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