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
2000-03-22
2002-09-10
Mullis, Jeffrey (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...
C525S078000, C525S086000, C525S095000, C525S098000, C525S097000, C525S099000
Reexamination Certificate
active
06448335
ABSTRACT:
This invention concerns ionomeric polymer mixtures. In particular, it relates to partially cross-linked thermoplastic and elastomeric polyolefin mixtures having low hardness, and the process for their preparation.
The mixtures of this invention are adequate for the use in the sectors of plasticized PVC and vulcanized elastomers.
In particular, by virtue of their tactile properties said mixtures are especially useful for the production of synthetic leather. In fact, the mixtures of the present invention are not only characterized by their low hardness, but cause the leather to feel much smoother and more satiny than the leathers produced with olefin polymers up to now.
Thanks to the above mentioned tactile characteristics, particularly softness, smoothness, and satiny texture, in addition to satisfactory properties at medium-high temperatures, said mixtures can be used as substitutes for PVC.
An other possible application for said compositions is their use in the shoe soles sector because of their good abrasion resistance.
Some partially cross-linked polyolefin compositions of the soft type are already described in European patent application EP-A-633289. However, said compositions are obtained by way of cross-linking with peroxide and a cross-linking coagent.
One problem presented by said known compositions consists in the fact that their surface is somewhat tacky, and said tackiness reveals itself in time. Compared to said compositions, the aesthetic aspect of the product manufactured with the mixtures of this invention is considerably improved.
Also known is the not cross-linked form of some of the mixtures of the present invention, as described in European patent application 97200530.0.
Said mixtures also show a minimum degree of tackiness (soft touch), a slight tendency of the components of the mixtures to separate, and a good but not high elastomeric property.
Now it has been found that the undesired tackiness phenomena are reduced in elastomeric polyolefin mixtures which are partially cross-linked with metallic ions.
Moreover, the mixtures of the present invention present satisfactory properties at high temperatures, in particular they show good elastic recovery as shown by the low tension set values at 100° C.
In particular, it has been found that those mixtures of the present invention that correspond to the not cross-linked mixtures described in the above mentioned European patent application 97200530.0 not only show the disappearance, or diminishing, of the above mentioned problems, but also present improved elastomeric properties.
From the mixtures of this invention one can obtain products that are just as soft as the ones derived from the composition of the above mentioned patent application, and at times even more so. Said products have a Shore A hardness around 60-90 points. In spite of the increased softness, the compositions of the present invention display more resistance to abrasion than the ones of said patent application.
The problem of mixture separation is also overcome since the mixtures of this invention are very homogeneous and stable in time.
Therefore, object of the present invention is a ionomer polymer mixture comprising C
2
-C
10
olefin polymers grafted with monomers containing al least one functional group, such as carboxylic acids, and metallic ions. Said ionomer polyolefin mixture comprises (weight percentage):
I. 100 parts by weight of a heterophasic polyolefin composition comprising:
a. 5-50%, preferably 10-40%, of a crystalline propylene homopolymer with an isotactic index greater than 80%, preferably from 85 to 90%, or a crystalline copolymer of propylene, ethylene and/or a CH
2
═CHR &agr;-olefin, where R is a C
2
-C
8
alkyl radical, or mixtures thereof; said copolymers containing more than 85% of propylene, and having an isotactic index greater than 80%;
b. 0-20%, preferably 0-15%, of a crystalline fraction of a copolymer of ethylene/propylene, or ethylene/CH
2
═CHR &agr;-olefin, where R is a C
2
-C
8
alkyl radical, or ethylene/propylene/said &agr;-olefin; said fraction being insoluble in xylene at ambient temperature; and
c. 40-95%, preferably 50-75%, of an elastomeric fraction of a copolymer of ethylene/propylene, or ethylene/CH
2
═CHR &agr;-olefin, where R is a C
2
-C
8
alkyl radical, or ethylene/propylene/said &agr;-olefin, and optionally with minor quantities of a diene; said copolymer fraction containing less than 40% of ethylene, preferably from 20 to 38%, and being soluble in xylene at ambient temperature; and
II. 0-250 parts by weight, preferably 0-200, more preferably 0-150, of an elastomeric polymer selected from:
a. copolymers of ethylene with a C
3
-C
10
&agr;-olefin, and optionally a diene, containing at least 20% of said &agr;-olefin;
b. copolymers of ethylene with methyl acrylate containing from 15 to 30% of recurring units of methyl acrylate or vinyl acrylate, and having a MIE ranging from 1 to 10 g/10 min (ASTM D-1238);
c. polyisobutylenes having a molecular weight ranging from 100,000 to 300,000 ca. measured as average viscosity;
d. atactic propylene homopolymers, and amorphous copolymers of ethylene with C
3
-C
6
&agr;-olefins produced with a catalyst obtained by contacting (1) a component comprising a transition metal M and at least one M-&pgr; bond and a legand and (2) a cocatalyst; and
e. styrene block copolymers containing at least one comonomer selected from butadiene and isoprene.
Among the above mentioned polyolefin mixtures the ones that are preferred are those that present a Shore A hardness of about 60-80 points. Said hardness values can be more easily obtained by adding hydrocarbon extender oils to the mixture of the present invention. Otherwise, said hardness values are typical of partially cross-linked mixtures containing, in addition to the above mentioned heterophasic composition (I), also the above mentioned elastomeric olefin polymers (II). Therefore, the mixtures of the present invention that are particularly preferred are the ones comprising (weight percentage):
1. 30-80%, preferably 40-75%, of the above mentioned heterophasic composition (I); and
2. 20-70%, preferably 20-65%, more preferably 25-60%, of the above mentioned elastomeric polymer (II).
Examples of heterophasic polyolefin compositions (I) are described in published European patent application EP-A-O 472946 (Himont Inc.).
As a way of example the total quantity of ethylene in heterophasic compositions (I) ranges from 15 to 35% by weight. Moreover, the intrinsic viscosity of fraction (C) generally ranges from 1.5 to 4 dl/g.
Preferably the content of propylene in the copolymers of fraction (A) ranges from 90 to 99% by weight. The isotactic index is defined as fraction insoluble in xylene at ambient temperature (see note 1 below). For the purpose of this document by said temperature is intended a temperature around 25° C.
Preferably the content of ethylene in fraction (B) is at least 75% by weight, more preferably at least 80% by weight, with respect to the total weight of (B). Preferably the copolymer is an essentially linear ethylene/propylene copolymer, for example a linear low density polyethylene (LLDPE).
Examples of CH
2
═CHR &agr;-olefins, where R is a C
2
-C
8
alkyl radical, linear or branched, which can be present in heterophasic composition (I) are 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene.
When present, the diene in fraction (C) of (I) ranges from 1 to 10% by weight, preferably 2.5-7%, with respect to the total weight of (C). Examples of dienes are butadiene, 1,4-hexadiene, 1,5-hexadiene, and 5-ethylidene-2-norbornene.
The above mentioned heterophasic composition (I) can be prepared by mixing fractions (A), (B), and (C) in the fluid state, i.e., at temperatures greater than their softening or melting point, or by way of sequential polymerization in two or more stages in the presence of a highly stereospecific Ziegler-Natta catalyst. In particular, the catalyst system used comprises (i) a solid catalyst component containing a titanium compound and an electron-donor compound supported o
Bonari Roberto
Braga Vittorio
Basell Poliolefine Italia S.p.A.
Mullis Jeffrey
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