Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1909-10-11
1993-11-30
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
524462, 5253262, 5253263, 526247, 526254, 526255, C08F 1422, C08F21422, C08K 502
Patent
active
052666506
DESCRIPTION:
BRIEF SUMMARY
This invention relates to fluorocarbon elastomers and their curing. In another aspect it relates to fluorinated ether compositions used in curing fluorocarbon elastomers. In another aspect it relates to fluorocarbon gum composition containing fluorinated ether compositions. In a further aspect it relates to a cured, shaped article of fluorocarbon elastomer, such as automotive fuel line hose and O-ring seals.
Fluorocarbon elastomers are synthetic elastomeric polymers with a high fluorine content--see, for example, West, A. C. and Holcomb, A. G., "Fluorinated Elastomers," Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 8, pp. 500.15 (#3rd ed., John Wiley & Sons, 1979). Fluorocarbon elastomers, particularly the copolymers of vinylidene fluoride with other ethylenically unsaturated halogenated monomers, such as C.sub.3 F.sub.6 (hexafluoropropene) have become the polymers of choice for high temperature applications, such as seals, gaskets, and linings, especially when shaped articles thereof are subject to exposure to aggressive or harsh environments, such as solvents, lubricants, and oxidizing or reducing conditions.
A major drawback to many applications of shaped articles made of such fluorocarbon elastomers has been their inability to satisfactorily function at low temperatures. At temperatures only slightly below 0.degree. C., the articles become stiff and fail to perform satisfactorily. Many fluoroelastomers also exhibit a tendency to become "scorchy", i.e., they cure prematurely or too rapidly when compounded. Fluoroelastomers may also adhere to dies upon curing making removal of the shaped fluoroelastomer article difficult.
Such fluorocarbon elastomers in general can be compounded and cured to have high tensile strength, good tear resistance, and low compression set. Such compounded polymers are typically fabricated into automotive engine oil seals, fuel system components, such as fuel line hoses and O-ring seals, and drive train seals. Smaller, hotter-running automotive engines, modern fuel blends, and aggressive oil additives and other chemical substances used in operating the engines have made fluorocarbon elastomers the polymers of choice for a host of elastomeric engine components where reliable sealing is required and of environmental concern--see Brullo, R. A., "Fluoroelastomer Rubber for Automotive Applications", Automotive Elastomer & Design. Jun. 1985, and "Fluoroelastomers Seal Up Automotive Future," Materials Engineering, Oct., 1988.
Most commercially available fluorocarbon elastomers, such as the illustrative polymers described above are sold, for example, under the trademarks "AFLAS", "FLUOREL" and "VITON". Some of these are crosslinked with aromatic polyhydroxy compounds, such as bisphenols, which are compounded with the elastomer gum along with a curing accelerator, such as a quaternary phosphonium salt, and acid acceptors, such as magnesium oxide and calcium hydroxide--see, for example, U.S. Pat. No. 4,287,320 (Kolb). Others are bromine-containing, peroxide-curable fluorocarbon elastomers--see U.S. Pat. Nos. 4,035,565 (Apotheker et al.) and 4,450,263 (West).
Several general types of fluorinated ethers have been described in the literature. One type is characterized by one of several homopolymeric segments or blocks of repeating units of the formula --CF(CF.sub.3)CF.sub.2 --O-- and made from hexafluoropropylene epoxide, see e.g., U.S. Pat. No. 3,250,807 (Fritz et al.). Another type is that characterized by blocks of repeating units of the formula --CF.sub.2 CF.sub.2 O-- and made from tetrafluoroethylene epoxide, see for example, U.S. Pat. No. 3,125,599 (Warnell). Others, made by reacting oxygen with tetrafluoroethylene or hexafluoropropylene, are characterized by a backbone made of repeating --CF.sub.2 O-- units, see e.g., U.S. Pat. No. 3,392,097 (Carraro et al.), or --CF(CF.sub.3)CF.sub.2 O-- units, see e.g., U.S. Pat. No. 3,442,942 (Sianesi et al.), or, in addition to either of these units, units of the formula --CF(CF.sub.3)O--, see e.g., U.S. Pat. No. 3,699,145 (Sianesi et al.)
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Guerra Miguel A.
Stivers David A.
Brink Robert H.
Griswold Gary L.
Kirn Walter N.
Michl Paul R.
Minnesota Mining and Manufacturing Company
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