Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-11-13
2001-08-07
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S284000, C524S285000, C524S396000, C524S551000, C428S461000, C428S479600
Reexamination Certificate
active
06271303
ABSTRACT:
FIELD OF THE INVENTION
The invention is in the field of fluorinated polymers containing vinyl fluoride units, their preparation and use in making protective coatings and films with reduced haze.
BACKGROUND OF THE INVENTION
Polyvinyl fluoride (PVF) has been manufactured for many years and has found many uses as a protective film or coating over a variety of substrates providing durable and cleanable surfaces. These surfaces are often thin films with the desirable property of being transparent thereby revealing the substrates beneath the film. Alternately these films may be pigmented to provide brightly colored coverings. Current market offerings are hazy and the presence of haze in the films detracts from the aesthetic quality of these coverings and limits their utility.
The fluorine atoms in PVF are largely responsible for its properties of excellent weatherability, chemical resistance and mechanical properties. Enhancement of these properties may be achieved with polymers of higher fluorine content. One way to increase polymer fluorine content is to prepare copolymers in which tetrafluoroethylene (TFE) replaces some of the vinyl fluoride (VF). Such dipolymers have been described by Coffman and Ford, U.S. Pat. No. 2,419,009 (1947); Sianesi and Caporiccio, J. Polymer Sci., Part A-1, 6, (1968) 335, and U.S. Pat. No. 3,513,116 (1970). The above references describe processes for producing VF/TFE dipolymers. Coffman and Ford describe an aqueous polymerization process using benzoyl peroxide initiator in the presence of vinyl fluoride monomer, such a process requiring elevated pressures. Sianesi and Capriccio describe preparation of the dipolymers in nonaqueous media such as alcohols or alcohol/water mixtures by using organometallic compounds as initiators, which process can be carried out at substantially reduced pressures. polymers produced from these prior art methods have nonionic end groups on the polymer chains formed. These nonionic end groups are typically alkyl or aryl and, therefore, hydrophobic in nature.
Stilmar, U.S Pat. No. 3,531,441 (1970), reported preparation in nonaqueous media of tri- and tetra-polymers composed of VF, TFE and a neutral polymerizable vinylidene monomer free of aromatic groups and free of halogen groups attached to the vinylidene group. The interpolymers of Stilmar were also formed with nonionic end groups.
Heretofore, the prior art teachings have not addressed the need for a polymer with high fluorine content which produces films with the properties desirable for protective coverings and with minimal haze. Furthermore, there are no known solvents for PVF and VF/TFE resins at ambient temperatures. Protective surfaces using these resins were previously prepared by laminating a preformed film, requiring special equipment and expertise, or by coating using a dispersion containing a latent solvent that must be processed at excessively high temperatures. Such methods are not practical for field application of these coatings or for repair of their surfaces damaged in use.
SUMMARY OF THE INVENTION
The present invention overcomes the limitations of known polymers by providing an interpolymer of vinyl fluoride and other fluorinated monomers which has reduced crystallinity. The interpolymer is especially useful for protective surfaces by forming coatings and films from the interpolymers. Films from the interpolymers of the present invention have substantially reduced haze, low surface tension, and can be made to form solutions in common organic polar solvents that are stable at room temperature. The extremely low surface tensions obtained with these interpolymer films and coatings provide enhanced stain resistance and improved release properties compared to polyvinyl fluoride or previously prepared vinyl fluoride interpolymers.
More specifically, the present invention provides an interpolymer consisting essentially of units derived from vinyl fluoride and at least two highly fluorinated monomers, at least one of the highly fluorinated monomers introducing into the polymer a side chain of at least one carbon atom. A preferred composition is an interpolymer which consists essentially of units derived from 30-60 mol % vinyl fluoride, 10-60 mol % of at least one C
2
olefin selected from the group of vinylidene fluoride, tetrafluoroethylene, trifluoroethylene, and chlorotrifluoroethylene, and 0.1 to 30 mol % of at least one highly fluorinated monomer which introduces into the polymer a side chain of at least one carbon atom.
The present invention also provides blends of such interpolymers with polyvinyl fluoride, aqueous and nonaqueous dispersions and organic solutions of such interpolymers, and shaped articles, laminates and coatings formed from such interpolymers.
DETAILED DESCRIPTION
The present invention is directed to terpolymers and higher interpolymers, consisting essentially of units derived from vinyl fluoride and at least two highly fluorinated monomers, at least one of the highly fluorinated monomers introducing into the polymer a side chain of at least one carbon atom. For the purposes of the present invention, “consists essentially of” means that, while the interpolymer may contain other polymer units, the significant properties of the interpolymer are determined by the named monomer units. A preferred composition is an interpolymer which comprises 30-60 mol % vinyl fluoride; 10-60 mol % of at least one C
2
olefin selected from the group of vinylidene fluoride, tetrafluoroethylene, trifluoroethylene, and clorotrifluoroethylene; and 0.1 to 30 mol % of at least one highly fluorinated monomer which introduces into the polymer a side chain of at least one carbon atom. A more preferred interpolymer comprises 20-40 mol % vinyl fluoride, 40-60 mol % of the C
2
olefin and 1.5-25 mol % of the highly fluorinated monomer.
Preferred highly fluorinated monomers which introduce into the polymer a side chain of at least one carbon atom useful for this invention include perfluoroolefins having 3-10 carbon atoms, perfluoro C
1
-C
8
alkyl ethylenes, fluorinated dioxoles, and fluorinated vinyl ethers of the formula CY
2
═CYOR or CY
2
═CYOR′OR wherein Y is H or F, and —R and —R′ are independently completely-fluorinated or partially-fluorinated alkyl or alkylene group containing 1-8 carbon atoms and are preferably perfluorinated. Preferred —R groups contain 1-4 carbon atoms and are preferably perfluorinated. Preferred —R′— groups contain 2-4 carbon atoms and are preferably perfluorinated. Preferably, Y is F. For the purposes of the present invention, by highly fluorinated is meant that 50% or greater of the atoms bonded to carbon are fluorine excluding linking atoms such as O or S.
Especially preferred highly fluorinated monomers useful in this invention are perfluoroolefins, such as hexafluoropropylene; perfluoroC
1
-C
8
alkyl ethylenes, such as perfluorobutyl ethylene; or perfluoro(C
1
-C
8
alkyl vinyl ethers), such as perfluoro(ethyl vinyl ether). Preferred fluorinated dioxole monomers include perfluoro-2,2-dimethyl-1,3-dioxole (PDD) and perfluoro-2-methylene-4-methyl-1,3-dioxolane (PMD). Hexafluoroisobutylene is another highly fluorinated monomer useful in this invention.
Preferred interpolymers in accordance with the invention have a melt viscosity in the range of 100-1000 Pa·s as determined by the method described herein below. Preferred interpolymers are substantially random interpolymers. The substantially random character of the polymer is indicated by nuclear magnetic resonance spectroscopy.
By adding a termonomer having a side chain of at least one carbon atom, the polymer compositions of this invention exhibit lower melting points and heats of fusion than unmodified compositions. Bulky side groups on the terpolymer hinder formation of crystalline lattice structure. For example in comparing modified terpolymers to copolymers such as VF/TFE where the copolymer and the terpolymer have the same [VF]/[TFE] ratio, reduced crystallinity of the terpolymer is observed. As a consequence, films made from terpolymers of
E. I. Du Pont de Nemours and Company
Zitomer Fred
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