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
1998-12-14
2001-03-27
Berman, Susan W. (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...
C525S199000, C264S473000, C264S496000, C522S112000, C522S109000
Reexamination Certificate
active
06207758
ABSTRACT:
The present invention relates to fluorinated thermoplastic elastomers having improved processing, in particular in the fuel hoses extrusion for motor applications and in the injection molding of various manufactured articles, especially O-rings and shaft seals.
As it is known, the thermoplastic elastomers are block copolymers consisting of at least a soft segment having elastomeric properties and of at least a hard segment having plastomeric properties. Such products combine therefore the typical properties of conventional cured elastomers with those typical of plastomers.
Compared with the conventional elastomers, the thermoplastic elastomers do not require any curing process, wherefore they become easily processable and recyclable according to the techniques usually employed for the thermoplastic polymers, with both economic and ecological clear advantages.
Fluorinated thermoplastic elastomers are known in the art. For instance, in U.S. Pat. No. 4,158,678 block fluorinated polymers are described, formed by alternate hard and soft segments, at least one of which is fluorinated. Such products are obtained by radical polymerization of fluorinated monomers in the presence of an iodinated chain transfer agent of formula RI
n
, wherein R is a fluorinated radical, optionally containing chlorine, having from 1 to 8 carbon atoms, and n is 1 or 2, thus obtaining a first fluorinated segment, with elastomeric or plastomeric features depending on the monomeric composition, having an iodine atom on one or both the end terminals. On such segment other fluorinated or non fluorinated different segments are grafted, by utilizing the fact that the terminal iodine atoms are sensitive to the radical attack and can therefore give rise to a new polymeric chain. It is thus possible to obtain, for example, fluorinated thermoplastic elastomers of A-B-A type, wherein A is a plastomeric segment (for example an homopolymer or copolymer deriving from tetrafluoroethylene and/or vinylidene fluoride), while B is an elastomeric segment (for example a tetrafluoroethylene/vinylidene fluoride/hexafluoropropene copolymer). Other thermoplastic elstomers of this kind are described in EP 444,700.
The drawbacks of such products are mainly of two types. On one hand the mechanical and elastic properties become poor when the temperature rises. Already at 50° C. such characteristics become unsatisfactory. Another disadvantage is caused by the processing difficulty due to the high viscosity of the material. In order to improve the processing, generally the molecular weight of the thermoplstic elastomer is reduced, in particular the molecular weight of the elastomeric part is reduced. In this case, however, the mechanical and elastic properties further fall off without obtaining an acceptable behaviour in processing.
Fluorinated thermoplastic elastomers having improved mechanical and elastic properties by the introduction in the polymeric chain of small amounts of a bis-olefin, are known also from U.S. Pat. No. 5,612,419. The resulting products are specifically characterized by improved mechanical properties and by particularly low compression set values compared with the fluorinated thermoplastic elastomers of the previously described patents. New fluorinated thermoplastic elastomers having mechanical and elastomeric properties similar to the U.S. Pat. No. 5,612,419 products, but having in the chain instead of the bis-olefin, small amounts of a fluorinated olefin containing a terminal iodine atom, are also known from EP 683,186. In the European Patent Application 98111124.8 it is described the curing, after the processing phase by GAMMA or BETA rays and in the presence of a suitable crosslinking agent, of the thermoplastic elastomers previously described. In particular, the curing by radiations of the bis-olefin containing polymers, object of U.S. Pat. No. 5,612,419, allows to obtain a remarkable increase of the sealing properties also at high temperatures, in the range of 150° C. However the processing of all the thermoplastic elastomers described in the preceding Patents results poor, in particular the processing of the thermoplastic elastomers, wherein the plastomeric phase is formed by polyvinylidenfluoride (PVDF), results even poorer. Since these latter show the best compression set properties at high temperature (see European Patent Application 98111124.8), it is important to set up synthesis methods allowing to prepare polymers mainly based on PVDF as plastomeric phase, able to be processed by extrusion to prepare fuel hoses with high extrusion rates and good surface aspect of the extruded product, or by injection molding to prepare O-rings and shaft seals.
For the thermoplastic elastomers of the art it is possible to improve the processing for example by reducing the molecular weight of the elastomeric phase. However the polymer elastic/mechanical properties are thus compromised.
It has now been surprisingly and unexpectedly found that it is possible to obtain thermoplastic elastomers with improved processing and contemporaneously having good mechanical and elastic properties.
It is therefore an object of the present invention a composition containing fluorinated thermoplastic elastomers having different moelcular weight and with different plastomeric phase/elastomeric phase ratio, said composition having dynamic viscosity determined by rheogoniometer RMS® 800 (Frequency sweep, frequency of 10
−2
radiants/sec, parallel plates) lower than 10
7
poise and Melt Flow Index (MFI), determined according to the ASTM D 1238-52T method with a 5 Kg load, higher than 1 (g/10 minutes); said composition being essentially formed by:
(a) 30-80% by weight, preferably 50-80%, of a fluorinated thermoplastic elastomer, having a block structure of A-B-A type, wherein A is a plastomeric segment and B is an elastomeric segment, in which at least one block is constituted by a fluorinated elastomer and at least one block by a fluorinated plastomer; said elastomeric segment B having a mooney viscosity (1+10 at 121° C.), determined according to the ASTM D 1648-82 method, higher than 10, more preferably higher than 30;
the plastomeric phase A amount being in the range 5-40% by weight, preferably 10-30%, more preferably 15-25%; the MFI of the thermoplastic elastomer determined according to the ASTM D 1238-52T method with the load of 5 Kg being lower than 0.1;
(b) 10-50% by weight, preferably 20-40% of a fluorinated thermoplastic elstomer having a block structure of A-B-A type, wherein A is a plastomeric segment and B is an elastomeric segment, wherein there is at least one fluorinated elastomeric segment and at least one fluorinated plastomeric segment;
the elastomer B having a mooney viscosity (1+10 at 121° C.), determined according to the ASTM D 1648-82 method, lower than 5, preferably lower than 1;
the plastomeric phase A must be in the range 2-20% by weight, preferably 3-10%; preferably the plastomeric phase must have similar monomeric composition, more preferaby the same plastomeric phase A of the component (a);
the MFI of the thermoplastic elastomer (b), determined according to the ASTM D 1238-52T method with the load of 5 Kg, being higher than 100;
(c) 0-30% by weight, preferably 0-15%, of a fluorinated plastomer preferably of the same kind as that contained in the component (a) and/or (b);
the MFI value, determined according to the method above indicated being higher than 1, preferably higher than 50; the sum of (a)+(b)+(c) being 100% by weight.
The composition can optionally contain from 1 to 10 phr (parts for 100 parts of (a)+(b)+(c)) of a crosslinking agent. In this case the obtained manufactured article, for example after extrusion or molding, can be irradiated by GAMMA rays, in an amount comprised between 1 and 30 Mrad, or BETA radiations in an amount comprised between 10 and 300 KGY (Kilogrey).
Said irradiation can be carried out for example according to the Patent Application No. 09/098,306, filed Jun. 18, 1998, now U.S. Pat. No. 6,107,363, herein incorporated
Arcella Vincenzo
Brinati Giulio
Arent Fox Kintner Plotkin & Kahn
Ausimont S.p.A.
Berman Susan W.
LandOfFree
Fluorinated thermoplastic elastomers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fluorinated thermoplastic elastomers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluorinated thermoplastic elastomers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2501530