United States Patent (113,624,250 72 Inventor Dana Peter Carlson 56 References Cited Wilmington, Del. UNITED STATES PATENTS 21 Appl. No. 4,394 2,392,378 1/1946 Hanford....................... 26/80 22 Filed Jan. 20, 1970 2,468,664 4/1949 Hanford et al.. 260/87.5 45) Patented Nov.30, 1971 3,235,537 2/1966 Albinet al...... 260/80.76 73 Assignee E. I. du Pont de Nemours and Company 3,303,154 2/1967 Hirose et al..... 260/29.6 Wilmington, Del. 3,444,148 5/1969 Adelman..... 260/80.72 Continuation-in-part of application Ser. No. 3,445,434 5/1969 Stilmar..................... ... 260/807 777,166, Nov. 19, 1968, now abandoned, Continuation-in-part of application Ser. No. Primary Examiner-Joseph L. Schofer 853,923, Aug. 28, 1969, now abandoned. Assistant Examiner-Stanford M. Levin This application Jan. 20, 1970, Ser. No. Attorney-Edwin Tocker 4,394 ABSTRACT: High temperature tensile properties of 54) COPOLYMERS OF ethylene/tetrafluoroethylene copolymer are improved by in ETHYLENEITETRAFLUOROETHYLENE AND OF corporating therein a small amount of a third monomer com ETHYLENE/CHLOROTRIFLUOROETHYLENE ponent which is a copolymerizable vinyl monomer which is 21 Claims, No Drawings telogenically inactive and provides a side chain in the resultant copolymer, containing at least two carbon atoms. In one em (52) U.S.C........................................................ 260/80.75, bodiment, the elements in the side chain have only single 260/80.6, 260/80.76, 260/80.77, 117/128.4 bonds therebetween, and in another embodiment the side 51 int. Cli........................................................ C08f 15/40 chain is an aromatic ring. The same effect is obtained for 50 Field of Search............................................ 260/41 A, ethylene?chlorotrifluoroethylene copolymer. The resultant 80.75, 80.76, 80.77, 80.81, 80.6 copolymers are especially useful as insulation coating for wire to be exposed to high temperature service. 3,624,250 1. 2 COPOLYMERS OF that the manner in which poly(ethylene/tetrafluoroethylene) ETHYLENE/TETRAFLUOROETHYLENE AND OF and poly(ethylene/chlorotrifluoroethylene) crystallize from ETHYLENE/CHLOROTRIFLUOROETHYLENE the molten state leads to the deficiency in tensile properties at high temperatures. The bulky side chain provided by the vinyl This application is a continuation-in-part of application Ser. 5 No. 853,923, filed Aug. 28, 1969, which, in turn, is a con monomer interferes with this manner of crystallization as in tinuation-in-part of application Ser. No. 777,66, filed Nov. dicated by the improved clarity of film made from copolymer 19, 1968 by the same inventor, both applications now aban of the present invention. The side chain of the vinyl monomers doned. useful in the present invention can further be defined as hav This invention relates to ethylene/tetrafluoroethylene O ing single bonds only between elements in the said chain or as copolymer, and to ethylene/chlorotrifluoroethylene consisting essentially of an aromatic nucleus. Typically the copolymer, and more particularly to such copolymers having vinyl group of the vinyl monomer will be fluorocarbon or improved high temperature tensile properties. hydrocarbon. Ethylene/tetrafluoroethylene copolymer (mole ratio of With these criteria for selection of the vinyl monomer set about 1:1) is potentially useful at high temperatures because 5 forth, numerous such monomers will suggest themselves to of its high melting point of about 275 C. Unfortunately, how one skilled in the art, as being applicable in the present inven ever, the tensile properties of the copolymer deteriorate well tion. Examples of such vinyl monomers are the fluorinated below the melting point so as to prevent the copolymer from vinyl monomers represented by the formulas being useful at temperatures up to its high melting point in R-CF=CF, and ROCF=CF, many applications. For example, a wire coating of the 20 wherein R is an organic group which can be cyclic, acyclic copolymer becomes brittle at 200° C. and cracks at low stress. and/or contain an aromatic nucleus and which contains from 2 The ultimate elongation of the copolymer which is in excess of to 8 carbon atoms. Generally, the organic group will be highly 300 percent at room temperature is usually less than 20 per fluorinated, i.e., at least one fluorine atom substituted on each cent at 200 C. carbon atom. However, other atoms can be present such as Copolymers of ethylene/chlorotrifuoroethylene are dis 25 chlorine as monosubstituents on a carbon atom. Hydrogen can closed in U.S. Pat. No. 2,392,378 to Hanford, but such also be present in the groups in a position where it is essen copolymers melt at temperatures below 200 C. A procedure tially inert, such as the omega position as part of the group of for preparing higher melting copolymers of these monomers is -CFH or as part of the group -CH3. Similarly, other atoms disclosed in European Polymers Journal, Vol. 3, pages such as Sand N can be present in an inert moiety 129-144 (1967), but even these higher melting copolymers 30 Representative fluorinated vinyl monomers that can be used cannot be used at high temperature application since they include the fluorinated a-monoolefins such as perfluorobu suffer from the same disadvantage as the ethylene/tetraflu tene-1, perfluoropentene-l, perfluoroheptene-1, and omega rorethylene copolymers. For example, a 1:1 mole ratio hydroperfluoroocetene-1 and the fluorinated vinyl ethers copolymer of ethylene/chlorotrifluoroethylene melting at represented by the formula XCF,(CF).OCF=CF, wherein X 235 C. has an ultimate elongation of greater than 150 percent 35 is F., H or CL and n is an integer of 1 to 7. Examples of such at room temperature but has an ultimate elongation of less vinyl ethers include perfluoro(ethyl vinyl ether), per than 32 percent at 200 C., making such copolymers useless as fluoro(propyl vinyl ether), and 3-hydroperfluoro(propyl vinyl a wire coating intended for service at 200 C. ether). Another fluorinated vinyl ether that can be used is per The present invention provides fluoro(2-methylene-4-methyl-1,3-dioxolane) which is ethylene/tetrafluoroethylene copolymer compositions and 40 described in U.S. Pat. No. 3,308,107 to Selman and Squire. ethylene?chlorotrifluoroethylene copolymer compositions The organic (R) group need not be highly fluorinated where having improved high temperature mechanical, especially ten some sacrifice in thermal stability of the resulting copolymer sile, properties. The copolymers of this invention comprise can be tolerated. Examples of monomers not highly from 40 to 60 mole percent ethylene, 40 to 60 mole percent of fluorinated and useful in the present invention include the tetrafluoroethylene or chlorotrifluoroethylene and an adju 45 hydrofluorocarbon fluorinated vinyl monomers and hydrocar vant amount of a copolymerizable vinyl monomer which is bon fluorinated vinyl monomers, such as of the formulas free of telogenic activity and which incorporates into the CF(CF)m CHOCF=CF, where m is an integer of 0 to 6 copolymer a side chain containing at least two carbon atoms, and CH3(CH) BnOCF.CF, where n is an integer of to 7, with the side chain having only single bonds between elements respectively. These vinyl ethers are made by reacting the or consisting essentially of an aromatic ring. 50 respective sodium alcoholate with tetrafluoroethylene By "copolymerizable' is meant that the vinyl monomer under conditions disclosed in U.S. Pat. No. 3, 259,609. must be able to form an integral part of the main copolymer Examples of these vinyl ethers includes n-butyl trifluorovinyl chain through the vinyl group of the vinyl monomer. Thus, the ether and 2,2,3,3,3-pentafluoropropyl trifluorovinyl ether. vinyl monomer must also not act as an inhibitor to prevent the 55 Examples of vinyl monomers in which the side chain is aro copolymerization reaction from occurring. matic include perfluorostyrene, pentafluorostyrene, and a,6,6 By "free of telogenic activity" is meant that the vinyl '-trifluorostyrene. monomer does not act as a chain transfer agent to an extent Additional vinyl monomers in which the vinyl group is which undesirably limits the molecular weight of the hydrocarbon and which are useful in the present invention can copolymer. Generally, for the tetrafluoroethylene-containing 60 be represented by the formulae copolymers of this invention, a molecular weight correspond ing to a melt viscosity of at least 5X 103 poises at 300° C. mea X X sured at a shear stress of 0.455 kg/cm.2 is desirable in order RiCHC=CH and R2OCH2C=CH2 for the copolymer to have acceptable tensile properties. These copolymers should have a melt viscosity of less than 5X106 65 wherein R and R” are perfluorinated or chloro-fluoroalkyl poises measured under the same conditions in order to be groups of 1 to 7 carbon atoms and X is H or CH. The simplest melt-fabricable. The same melt viscosity parameters apply to of these vinyl monomers are prepared by reacting hex the chlorotrifluoroethylene copolymers of this invention ex afluoroacetone with propylene in the presence of AICIa and cept that the melt viscosity is determined at 260C. hexafluoroacetone with allyl bromide in the presence of Csf, The requirement that the vinyl monomer have a side chain 70 respectively. Further description of vinyl monomers of these having at least two carbon atoms is another way of describing formulae and process for making them is provided in Knu the minimum bulk of the side chain. When the side chain has nyants, Bull. Acad. Sci., USSR, Div. Chem. Sci, 355 (1962 ) this minimum bulk, improvement in high temperature tensile and Dutch Pat. No. 6,602,167. Typical R and R groups for properties is obtained, and when the side chain does not have these monomers include the perfluoroalkyls such as this minimum bulk, no improvement is realized.