Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1995-05-31
1997-07-15
Schofer, Joseph L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
570124, 526255, 526254, C07C 1702
Patent
active
056485662
DESCRIPTION:
BRIEF SUMMARY
This application is based on the priority of International application Ser. No. PCT/US94/09661 filed Aug. 25, 1994.
It is known that hexafluoroacetone (U.S. Pat. No. 3,894,097) or hexafluoroacetone hydrate (DE-A 3 425 907) react with diketene, acetic anhydride, acetic acid or acetone at temperatures of 340.degree. C. to 1000.degree. C. to form hexafluoroisobutylene (HFiB) via the intermediate compound bis(trifluoromethyl)-.beta.-propiolactone (I. L. Kumyats et al., Izvest. Akad. Nauk. SSR, 640 (1960) (in English)).
It was not to be expected from prior art, and it is surprising, that the reaction of ketene-producing compounds such as diketene, acetic anhydride, acetic acid or acetone at temperatures of 340.degree. C. to 1000.degree. C. with perfluorocycloketones to form methyleneperfluorocycloalkanes in satisfactory yields is possible, in spite of the steric requirements of the spirolactone (J. March, Advanced Organic Chemistry, McGraw-Hill 1977, Chapter 4, pages 144 ff.) of the formula III which is formed as an intermediate compound.
Compared with the "HFiB process", according to the invention the methyleneperfluorocycloalkanes are obtained isomerically pure. The starting components and the by-products can be easily separated off (particularly from n=2) by virtue of the boiling points.
Fluoropolymers are always used in technology when particular properties are desired, such as low surface tension, high resistance to chemicals, oil and solvents, or extreme requirements as to the (heat) ageing stability combined with a high heat deflection temperature.
As the most widely-produced synthetic in the field of fluoropolymers, polytetrafluoroethylene (PTFE) combines the above-mentioned properties the most comprehensively. However, as is generally known, PTFE cannot be processed thermoplastically. Heat deflection temperature and gas permeability rapidly decrease at temperatures of above 100.degree. C. An improvement in the thermoplastic processability is achieved through the introduction of comonomers, which reduce the viscosity of the polymer above the softening point (melting point in partly crystalline systems) and thereby improve the melt fusion. Examples of comonomers of this kind are hexafluoropropene and perfluorinated acyclic alkyl vinyl ethers. But in most cases the softening point of the copolymer is lowered by this measure, so that compromise solutions have to be accepted, depending on the intended application.
Other fluorine-containing homopolymers such as poly-vinylidene fluoride or polychlorotrifluoroethylene can be processed thermoplastically but, owing to their lower fluorine content, they do not achieve the above-mentioned properties to the level which is achieved by the most highly fluorinated (co)polymers. Here also definite improvements can be obtained through copolymerisation.
According to a previously unpublished proposal by the Applicant, copolymers of perfluoro(cycloalkyl vinyl ethers) with VDF or CTFE show improved heat stabilities compared with the homopolymers.
Using the copolymers of VDF and hexafluoroisobutylene (HFiB) described in U.S. Pat. No. 3,706,723, higher melting temperatures (>=300.degree. C.) are achieved than with pure PVDF (160.degree. to 170.degree. C.). Owing to the decomposition which is already beginning at 360.degree. C., copolymers of this kind offer however only a narrow scope for processing (TOMMASI, G.: Fluoropolymers Conference 1992, Manchester). Moreover, highly toxic intermediate compounds appear during the synthesis of HFiB. Copolymers of HFiB with vinyl acetate (Vac) or vinyl alcohol (VOH) (U.S. Pat. No. 5,053,470) are amorphous and show glass transitions at approximately 45.degree. to 90.degree. C. They are, however, unsuitable for many applications owing to their low glass transition temperatures, which are a measure of the thermoplastic softening.
The present invention provides new fluoromonomeric units of the formula (I) ##STR2## wherein n equals 3 to 5 wherefrom there can be produced a multiplicity of thermoplastically processable copolymers having diff
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FR 1557170, Gozzo et al; Feb. 14, 1969 Abstract.
I.L. Kumyats et al., Izvest. Alcad. Nauk. SSR, pp. 640-646 (1960).
J. March, "Advanced Organic Chemistry" 2nd ed., pp.. 144-147, McGraw-Hill, New York (1977).
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Kruger Ralf
Lui Norbert
Marhold Albrecht
Negele Michael
Bayer Aktiengesellschaft
Sarofim N.
Schofer Joseph L.
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