Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-06-27
2003-07-01
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S250000, C526S253000, C526S254000
Reexamination Certificate
active
06586547
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to compositions of matter classified in the art of chemistry as fluoropolymers, more specifically to copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) and still more specifically to such copolymers having very low or no crystallinity and to processes for their preparation and use. The copolymers at all levels of HFP content remain highly flexible, thermoplastic copolymers which show low surface tack even at high HFP levels.
Fluoropolymers and copolymers of VDF, collectively VDF-based polymers wherein the VDF portion is greater than the total molecular percent of comonomers, are well known and widely used. Among the variety of fluoropolymers based upon tetrafluoroethylene, chlorotrifluoroethylene, and other speciality fluorine-containing monomers, the VDF polymers are unique offering the widest possible range of processing options to obtain articles having the beneficial attributes associated with improved chemical resistance and surface properties associated with the high concentration of carbon fluorine bonds. Thus, among the wide spectrum of fluoropolymers, the VDF polymers may be melted in typical processing equipment for thermoplastic resin for extrusion or molding or combinations such as extrusion-blown film and molding into tanks.
This versatility in processing options is related to the linear polymer chain structure and the presence of the highly polar-CF
2
-groups alternating along the VDF polymer chain. The microstructure of the polymer chain and morphology of these polymers reflects these two factors in many interesting ways as described in Polymeric Materials Encyclopedia, 1996, Vol II, CRC Press; Vinylidene Fluoride-Based Thermoplastics (Overview and Commercial Aspects), J. S. Humphrey, pp. 8585 to 8588; Vinylidene Fluoride-Based Thermoplastics (applications), J. S. Humphrey and E. J. Bartoszek, pp. 8588-8591; Vinylidene Fluoride-Based Thermoplastics (Blends with Other Polymers), J. S. Humphrey and X. Drujon, pp. 8591-8593; Vinylidene Fluoride-Based Thermoplastics (Homopolymerization and Copolymerization), J. S. Humphrey and X. Drujon, pp. 8593-8596.
The balance between amorphous and crystalline regions, the nature and extent of the crystalline regions, and the interphase between these regions affects the mechanical properties significantly, and hence, the ultimate applications for a given resin composition.
At one end of the spectrum there are totally amorphous thermoplastic polymers and at the other S extreme the highly crystalline polymers. The microstructure of the polymer chain determines the flexibility (or alternately the stiffness) at a given temperature. This mechanical behavior is controlled by the type and amount of the crystalline phase (if any) and the dynamics of the molecular motion along the chain such that at some temperature the polymer undergoes a second order change in response to applied stresses, the so-called glass transition temperature (Tg). Above the Tg the polymer chain has molecular motions which are free to rotate, stretch, etc. and thereby absorb the energy input. Below the Tg the molecular motions are frozen and the stresses may lead to brittle fracture or glass-like behavior.
The immediate invention is concerned more with the morphology and crystalline/amorphous.ratio of the VDF polymers and the ultimate end uses. It is therefore important to understand the background of the present invention in the context of the teaching how crystalline and amorphous content fit into the range of polymers which are classed as thermoplastic, elastomer-modified thermoplastic, or elastomeric resins. In this particular invention, the key attribute is related to highly flexible resins related to the latter two categories. This invention produces a variety of VDF-HFP resins, which are differentiated quite clearly from prior art with respect to the low level of crystallinity compared to resins of the otherwise same nominal monomer ratio composition produced by standard teachings. Thus, the present invention relates to a novel fluoro-thermoplastic having a unique combination of properties including excellent flexibility, low temperature processability, high clarity,solution stability and room temperature film forming capability from aqueous dispersions.
PRIOR ART
U.S. Pat. No. 3,051,677 describes batch emulsion and continuous emulsion processes for copolymerization of vinylidene fluoride and hexafluoropropylene (HFP) in the range of 30 to 70 weight percent of hexafluoropropylene monomer and 70 to 30 weight percent vinylidene fluoride monomer. The copolymers described in this reference have relatively high crystallinity as is confirmed by the properties described in the document for the products exemplified. Analogous materials from a batch process are described by Moggi, et. al. in Polymer Bulletin, Vol. 7 pp. 115-122 (1982).
U.S. Pat. No. 3,178,399 describes both batch and semi-continuous emulsion processes for preparing HFP-VDF copolymers having between 85 and 99 mole percent VDF and 1 and 15 mole percent HFP (approximately 2 to 30 weight percent HFP and 70 to 98 weight percent VDF). Once again, the copolymers produced have relatively high internal crystallinity and this fact is evidenced by the physical data provided for those copolymers actually exemplified. This patent discloses that Tensile X Reversible Elongation was increased as the overall HFP proportion decreased in the copolymer. This implies that crystallinity increases as HFP content decreases.
U.S. Pat. No. 5,093,427 describes HFP-VDF copolymers, with the other extreme crystalline melting behavior, containing from about 1 to 20 weight percent HFP wherein, based on the synthetic method described, a polymer containing significant portions of homopolymer and other copolymer portions having a high proportion of HFP in the copolymer results. Thus, compositions of the copolymers described in this reference are significantly different from the copolymers contemplated by the present invention.
Indonesian Patent Application W-980105, published Nov. 26, 1998 as number 020.295A equivalent to WO 98/38242 and to U.S. patent application Ser. No. 09/031,014, the contents of which have been included in CIP Application 09/641,015 discloses an emulsion process for producing HFP-VDF copolymers having highly homogenous distribution of the comonomers in individual claims and from chain to chain thereby having reduced extractable content and improved solution clarity over HFP-VDF copolymers prepared according to the techniques of the preceding references. These materials differ from the copolymers of the present invention because the products of this patent application are limited to lower percentages of HFP content, the solubility and solution stability properties as well as the reduced melting points are attributed to the homogeneous distribution of the comonomers and no discussion of the crystallinity or lack thereof of the polymers described and whether or not it might be related to any of the properties observed for those polymers is provided.
In Polymer, Vol. 27, p. 905 (1986) and Vol. 28, p. 224 (1987), Moggi, et al. Report synthesis of HFP-VDF copolymers and studies of various physical properties and how these properties may be correlated to certain internal structural features such as crystallinity, monomer sequencing in individual molecules and the like. The limited synthesis information indicates that the polymers formed were analogous to those prepared according to the previous references except for U.S. patent application Ser. No. 09/031,014 and the limited physical data provided is consistent with this interpretation and that the polymers described had a high degree of crystallinity.
Although it is well established in the prior art to reduce crystallinity by means of adding higher amounts of HFP to the copolymer, there is no prior art suggesting how to produce as low crystallinity as is provided by the present invention at any given nominal proportion of HFP. Thus, the copolymers disclosed herein have measurably lower crystallini
Amin-Sanayei Ramin
Durali Mehdi
ATOFINA Chemicals, Inc.
Mitchell William D.
Zitomer Fred
LandOfFree
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