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
1998-06-15
2001-01-23
Seidleck, James J. (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...
C525S153000, C525S326200, C525S418000, C524S544000, C524S545000, C524S546000, C428S421000, C428S036900, C264S171270, C264S514000
Reexamination Certificate
active
06177518
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to blends of fluoroplastics and polyetherketoneketone having improved properties.
BACKGROUND OF THE INVENTION
Fluoroplastics which are fabricable by melt flow at temperatures above their melting points have a wide range of utilities because of their chemical inertness and high melting temperature. These utilities could be broadened if such properties as room temperature toughness, high temperature physical properties such as heat distortion temperature and/or permeability could be improved. The use of additives in the fluoroplastic in an attempt to achieve such improvement suffers from one or more problems of incompatibility with the fluoroplastic, resulting in deterioration of desired properties, and difficulty in uniformly incorporating the additive into the fluoroplastic.
SUMMARY OF THE INVENTION
It has been found that incorporation of varying amounts of polyetherketoneketone, commonly known as PEKK, into melt-flowable fluoroplastics imparts surprising improvements in properties to the fluoroplastic. Another aspect of the present invention is the incorporation of the fluoroplastic into the PEKK to cause surprising improvement in properties of the PEKK. In this aspect, the fluoroplastic is dispersed in PEKK as the matrix instead of the PEKK being dispersed in the fluoroplastic as in the first-mentioned embodiment. Thus, the present invention is a composition comprising 5 to 95 wt % melt-flowable fluoroplastic and complementally, to total 100 wt %, 95 to 5 wt % PEKK.
DETAILED DESCRIPTION OF THE INVENTION
In one embodiment of the present invention, the melt-flowability of the fluoroplastic enables it to be fabricated by melt extrusion, including injection molding. As such, the fluoroplastic can have a melt flow rate (MFR) in the range of 1 to 100 g/10 min determined in accordance with ASTM D-1238 at the temperature which is standard for the fluoroplastic. The fluoroplastic is non-elastomeric, i.e. the stress-strain curve for the fluoroplastic exhibits a yield point, and upon further stretching of the fluoroplastic, there is little recovery of strain (stretch), e.g. less than 20%, upon release of the stretching force. Examples of melt-fabricable fluoroplastics include the group of well known fluoropolymers comprising tetrafluoroethylene (TFE) copolymers, particularly the copolymers of TFE with one or more comonomers selected from perfluoroolefins having 3-8 carbon atoms, preferably hexafluoropropylene (HFP), and perfluoro(alkyl vinyl ether) (PAVE) with alkyl groups having 1-5 carbon atoms, preferably 1-3 carbon atoms, most preferably 2-3 carbon atoms. Such copolymers have sufficient concentration of comonomer to reduce the melting temperature of the copolymer significantly below that of TFE homopolymer. Preferred melt-fabricable fluoroplastics include TFE/HFP (typically referred to as FEP), TFE/PAVE (typically referred to as PFA), and TFE/HFP/PAVE. The aforesaid TFE copolymers can also contain minor amounts of units derived from other comonomers, including polar-functional monomers that introduce polar groups along the polymer chain, usually at the end of pendant side groups, when copolymerized into the polymer. Fluoroplastics other than the perfluorinated copolymers mentioned above can also be used, such as copolymers of TFE or chlorotrifluoroethylene (CTFE) with ethylene, and TFE/HFP/vinylidene fluoride copolymer (THV). The processing of the fluoroplastic at temperature above its melting point indicates that the fluoroplastic has crystallinity. The fluoroplastic used in the present invention may also be amorphous, however, in which case, the processing of the fluoroplastic is at a high temperature that the PEKK will be flowable as though molten during the processing.
In another embodiment of the present invention, a portion of the melt-fabricable fluoroplastic is replaced by polytetrafluoroethylene (PTFE) micropowder. PTFE micropowder is a tetrafluoroethylene homopolymer or modified homopolymer which has a considerably lower molecular weight than the normal high melt viscosity PTFE, which enables the micropowder by itself to be melt flowable, having a melt flow rate within the range described for the melt-fabricable fluoroplastics. The high molecular weight of the normal PTFE is characterized by a molecular weight (Mn) of at least 2,000,000 and a melt viscosity of at least 10
8
Pa.s at 380° C., this melt viscosity being so high that the PTFE does not flow in the molten state, requiring special non-melt-fabrication techniques, including paste extrusion for the fine powder type of PTFE and compression molding for the granular type of PTFE. In contrast, the molecular weight (Mn) of PTFE micropowder will usually be within the range of 50,000 to 700,000, and the melt viscosity of the micropowder will be 50 to 1×10
5
Pa•s as measured at 372° C. in accordance with the procedure of ASTM D-1239-52T, modified as disclosed in U.S. Pat. No. 4,380,618. Preferably the melt viscosity of the PTFE micropowder is 100 to 1×10
4
Pa•s at 372° C. PTFE micropowder is described further in Kirk-Othmer, The Encyclopedia of Chemical Technology, 4
th
Ed., pub. by John Wiley & Sons (1994) on pp 637-639 of Vol. 11, and in the article H. -J Hendriock, “PTFE Micropowders”, Kunstoffe German Plastics, 76, pp. 920-926 (1986). These publications describe the micropowder as being obtained by polymerization or by irradiation degradation of the high molecular weight (high melt viscosity) PTFE. Polymerization directly to the micropowder is disclosed for example in PCT WO 95/23829, wherein the micropowder is referred to as low melt viscosity PTFE. Although the PTFE micropowder is melt flowable, it is not melt fabricable by itself because the resultant product has no practical strength due to the low molecular weight of the PTFE micropowder. Thus, the beading obtained in the melt flow rate test from which the melt viscosity is determined is brittle such that it breaks upon the slightest flexure.
When a portion of the melt-fabricable fluoroplastic is replaced by PTFE micropwder, at least 10% by weight of the total fluoroplastic will be the melt-fabricable fluoroplastic, preferably at least 20 wt %, the remainder being the PTFE micropowder. Surprisingly, the PTFE micropowder imparts increased strength to articles molded from the fluoroplastic/PEKK blend, even though the PTFE micropowder has no strength by itself as described above.
The PEKK component is a copolymer of diphenyl ether and benzene dicarboxylic acid halides, preferably terephthalyl (T) or isophthaloyl (I) halides, usually chlorides, and mixtures thereof, such as disclosed in U.S. Pat. Nos. 3,062,205, 3,441,538, 3,442,857, 3,516,966, 4,704,448, and 4,816,556, preferably having an inherent viscosity of at least 0.4 measured on a 0.5 wt % solution in concentrated sulfuric acid at 30° C. The PEKK generally has a melting point of at least 300° C. Typically, the PEKK contains both T and I units in a ratio of 90:10 to 30:70, and more typically 80:20 to 60:40. As the proportion of T units decrease and I units increase, the crystallinity of the PEKK diminishes, until at 60:40, the PEKK crystallizes so slowly that it resembles an amorphous polymer, except that it will exhibit a melting point.
With respect to the combination of fluoroplastic and PEKK forming compositions of the present invention, in a general sense, the preferred composition has at least 25 wt % of the melt-flowable fluoroplastic. For specific results, the proportion of the fluoroplastic will vary. One of the improvements which a relatively small amount of PEKK imparts to the fluoroplastic is improved cut-through resistance which is especially valuable in the use of fluoroplastic for insulation coating or jacketing of insulated wire. In this embodiment, the PEKK content of the composition will be 5 to 25 wt %, preferably 10 to 20 wt %. While the PEKK is incompatible with the fluoroplastic as indicated by the PEKK being present as discrete particles (domains) dispersed in the fluoroplastic matrix forming the insulation or jacketi
Asinovsky Olga
E. I. Du Pont de Nemours and Company
Seidleck James J.
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