WO1990003357A1 - Perfluoroacetal and perfluoroketal compounds and use thereof in thermal shock testing - Google Patents

Abstract

Perfluorinated gem-alkylenedioxy compounds, viz., perfluoroacetal and ketal compounds, which can contain chlorine, useful, for example, as liquid heat transfer media such as thermal shock fluid and vapor phase soldering fluid, made by direct fluorination of their perfluorinateable precursors.

Description

PERFLUOROACETAL AND PERFLUOROKETAL COMPOUNDS AND USE THEREOF IN THERMAL SHOCK TESTING

This appli cation is a continuation-in-part of

U. S. Patent applications Serial No. 07/250,384, filed September 28, 1988, and Serial No. 07/278,958, filed December 2, 1988.

This invention relates to perfluoroacetals and perfluoroketals, their preparation, and to their use as liquid heat transfer media, e.g. in inducing a thermal shock to an article, such as an electronic component or device, for test purposes.

Thermal shock testing is used to determine the effect, if any, of rapid and extreme temperature changes on electronic components, for example those used in aircraft which in seconds must be able to ascend from desert heat into stratospheric sub-zero cold. This testing is a type of quality control screening or

evaluation used to select or eliminate those electronic components which would probably be susceptible to failure in actual use when subjected to high and/or low

temperature extremes. The electronic component to be tested is alternately heated far above ambient temperature and cooled far below ambient temperature to induce a thermal shock and then visually inspected and/or

performance-tested for defects that may result from the thermal shock, e.g. electrical conductivity anomalies due to cracks and other failures in the components.

One common method of heating and cooling an article for thermal shock testing involves the use of immersion fluids. Inert fluorochemical immersion fluids are

generally recognized as the most suitable liquids for thermal shock testing because of their excellent thermal stability and compatibility with electronic circuit and electronic circuit package materials.

Comme rcially available fluorochemi cal l iquids whi ch are useful as heat transfer testing liquids include those electronic liquids sold under the trademark FLUORINERT, which are described, for example, in trade bulletin

Y-IERTR(131)NP1 of the 3M Company. In the case where the thermal shock testing is carried out at two widely

different temperatures, e.g. 150°C and -65°C, two

different testing liquids generally have been required, one being a heating liquid with a boiling point in excess of the temperature of the heating bath and one being a cooling liquid with a low viscosity at the temperature of the cooling bath. According to U. S. Government Military Standard 883-1011.6, November 29, 1985, a perfluorinated liquid composition, FLUORINERT Electronic Liquid FC-40, having a boiling point at about 155°C, has approval as the heating liquid for thermal shock testing up to 150°C, and a perfluorinated liquid composition, FLUORINERT Electronic Liquid FC-77, having a boiling point of about 97°C and a low viscosity at -65°C, has approval as the cooling liquid. However, it has been found that after extended use, losses of portions of these liquids often occur when some of the low boiling cooling bath liquid is unavoidably carried over, on the surfaces of the electronic component, into the heating bath where the liquid that was carried over is volatilized. Furthermore, viscosity increases in the cooling bath, caused by carry-over of heating bath liquid into the cooling bath during extended use, often result in forming a cooling liquid mixture that is not as efficient as the original cooling liquid for rapid cooling of the electronic component under test. The cooling liquid mixture formed after extended use by carry-over may then have to be separated, e.g. by distillation, into two liquids for re-use.

A liquid mixture of perfluoropolyethers sold under the trademark GALDEN has been described as useful as a single thermal shock liquid, i.e. a liquid used for both the heating and cooling baths. The GALDEN^R fluids are described in a trade bulletin of Montedison S.p.A. on "GALDEN^R PERFLUORINATED FLUIDS" as a mixture of linear low molecular weight polymers said to have the structure

CF₃-[(O-CF(CF₃)-CF,) (O-CF₂)_m]O-CF₃. The GALDEN^R

perfluorinated fluid sold as DO2TS has been found to have a boiling point of 165°C and viscosities of 231

centistokes (cs) and 1075 cs at -70°C and -80°C,

respectively. However, the lower molecular weight

components of such fluids can boil off from the heating bath and the remaining higher molecular weight components can lead to increased viscosity in the cooling bath.

Measures can be taken to narrow the molecular weight distribution of th olyether mixture prior to use as a single thermal shock fluid, e.g. by control of the

polymerization conditions and/or distillation of the product, but these measures may be difficult and may not be wholly effective or economically practical.

Various other perfluoropolyethers, useful as thermal shock fluids in the testing of electronics, are the mixtures of random structures and molecular weight

distributions disclosed in European Patent Application No. 86105359.3 (Montedison S.p.A.) published April 24, 1985 as Publication No. 0203348. Although European Patent

Application No. 82303332.9 (the Green Cross Corp.), published April 4, 1983, as Publication No. 0077114, broadly discloses preparation of certain

perfluorochemicals by fluorination of partially

fluorinated ketals and acetals, there is no enabling disclosure of the latter. And U. S. Patent

No. 4,760,198 (Bierschenk et al.) discloses certain copolymers of difluoromethylene oxide and

tetrafluoroethylene oxide, inclusive of some

perfluoroacetals, those copolymers being mixtures of a plurality of molecular species of perfluoropolyethers with a broad range of molecular weights, some of the species having a random internal structure and all of the species having inert terminal groups, viz., random distribution of methyl or ethyl.

Briefly, in one aspect, this invention provides a perfluorinated gem-alkylenedioxy composition which can be normally liquid and which consist or consist essentially of one or a mixture of perfluorinated gem-alkylenedioxy compounds, viz., perfluoroacetal or perfluoroketal

compounds, having 6 to 100, and preferablyl at least 12, e.g. 12 to 50, carbon atoms, which are useful, for

example, as lubricants, hydraulic fluids, liquid heat transfer media such as thermal shock fluid and vapor phase soldering fluids, and in numerous other applications in which an inert, nonflammable, oxidatively stable fluid is required. The low molecular weight perfluoropolyethers of the present invention h ve many useful applications in the electronics industry. Fluorocarbon fluids are useful as coolants and insulators in high-voltage electronic

equipment, as immersion medium for leak testing, as heat transfer agents for vapor phase soldering, as fluids for direct cooling of electronic devices and as thermal shock fluids.

A broad class of perfluorinated gem-akylenedioxy compounds of this invention can be presented by the general formula:

wherein Y and Y' are the same or different and are

selected from the group consisting of perfluoroalkyl , perf luoroalkyleneoxyalkyl and

perfluoropoly(alkyleneoxy)alkyl wherein one or more but preferably not all of the fluorine atoms may be halogen atoms other than fluorine, e.g. chlorine; wherein R₁ and R₂ are the same or different and are selected from the group consisting of -F, -Cl, -CF₂ Cl, -CFCl₂, -CCl₃, and perfluoroalkyl of 1 to 10 carbon atoms wherein one or more of the fluorine atoms but preferably not all may be halogen atoms other than fluorine, e.g., chlorine an wherein the perfluoroalkyl group may contain one or more ether oxygen atoms. Where Y and Y' are perfluoro- poly(alkyleneoxy)alkyl, the polyether of formula I may be an atactic or isotactic polymer or a block copolymer each having up to 50 carbon atoms; examples of such polyethers are Y-O-CF₂-OY and Y-O-CF(CF₃)-O-Y wherein each Y is the same, i.e., the same perfluoropoly(alkyleneoxy)alkyl group.

Formula I can be considered as embracing two types of fluorinated ethers: (1) perfluoroacetals, when one of R₁ and R₂ is a halogen, e.g. fluorine (a subclass of

perfluoroacetals being perfluoroformals, when both R₁ and R₂ are halogen, e.g. fluorine); and (2) perfluoroketals, when both of R₁ and R₂ are o er than halogen, viz., perhaloalkyl, which can contain oxygen.

In another embodiment of formula I, when Y or Y' have 20 or fewer carbon atoms and R₁ is fluorine then R₂ is a group other than -CF₃ or -CF₂Cl.

In another aspect, this invention provides a normally liquid, perfluoroacetal composition which is useful, for example, as a thermal shock testing fluid. The

composition can consist or consist essentially of a saturated perfluoro-1,1-bis(alkyloxy)alkane compound as the single molecular species in the composition (and such composition is hereafter on occasion referred to for brevity as a "single molecular perfluoroacetal

composition" or "unimolecular" composition or fluid).

Said compound (hereafter referred to on occasion as a perfluoroacetal compound) thus has a

perfluoro-1,1-alkylenedioxy moiety, -O-CF-O-, but can have another perfluoro-1,1-alkylenedioxy moiety, provided it i s separated f rom the othe r by at least two catenary carbon atoms of a perfluoroalkylene moiety. In another aspect, this invention provides a normally liquid, perfluoroacetal composition which consists or consists essentially of a mixture of two or more such compounds (and such

composition is hereafter referred to on occasion for brevity as a "mixed perfluoroacetal composition") of discrete, non-random molecular weights, said compounds preferably being those having complementary properties, for example, boiling points and pour points each within respective narrow ranges, desired for a particular use of the composition, e.g. for use as a heat exchange medium. Unless otherwise stated or apparent, the term

"perfluoroacetal composition" as used herein means that consisting or consisting essentially of one or a mixture of said compounds, that is, the term is used in a generic sense to cover the single molecular and the mixed

perfluoroacetal compositions of this invention.

The perfluoroacetal compound can have one or a few, e.g. 2 or 3, chlorine atoms, each of which is bonded to carbon atoms other than those carbon atoms to which an ether oxygen atom is bonded; stated otherwise, the

compound can have 1, 2, or 3 carbon-bonded chlorine atoms in place of 1, 2 or 3 carbon-bonded fluorine atoms of the alkyloxy moieties if the carbon atoms to which the

chlorine atoms are bonded are other than those to which the ether oxygen atoms are bonded.

The perfluoroacetal composition, which is liquid at ambient conditions, e.g. 20°C at 740 Torr, generally has a boiling point greater than 20°C, preferably a boiling point of at least 40°C, and more preferably a boiling point greater than 125°C, e.g. 180°C, and can have a boiling point as high as 300°C. Generally the.

perfluoroacetal compound has at least 6 carbon atoms, and can have as many as 24 carbon atoms or even up to 30 carbon atoms, but preferably the compound has at least 12 carbon atoms, e.g. 12 to 17 carbon atoms. Where a

perfluoroacetal compound is a chlorine-containing

perfluoroacetal compound, its effect on the boiling point of the perfluoroacetal composition will be approximately the same as that of a perfluoroacetal compound which does not contain chlorine atoms and has a higher carbon

content. Generally, one chlorine atom will have about the same effect on boiling point as 1.5 to 2 carbon atoms.

A particularly useful property of the perfluoroacetal composition of this invention is its wide liquid range, meaning it is normally liquid over a wide temperature range; in fact, some of them can be considered as having exceptionally wide liquid ranges. A feature of the perfluoroacetal compositions of this invention is that the perfluoroacetal compound or compounds thereof are each of well-defined, definite, certain, and known structure of a non-random nature and with fixed carbon, fluorine, and oxygen ratios and of a definite (or particular or

distinct) molecular identity. In the mixed

perfluoroacetal compositions, specific molecular

structures and amounts of each compound in the mixture are features which can be completely predetermined and the mixture made by mixing or blending selected single

molecula r perfluoroacetal compositions or the mixture made as such as a reaction product of the corresponding

precursor mixture of acetals. These features are in contrast to those perfluoropolyether chemicals which are polymeric or oligomeric in nature and have a distribution of molecular weights, those which have a random structure, or those which are a random mixture of compounds. The control over the nature of the single molecular

perfluoroacetal compositions of this invention is a feature which means that their physical properties, particularly their low temperature viscosity and their discrete boiling point, are invariable under conditions of use, for example where in use as a thermal shock fluid some of such single molecular weight perfluoroacetal composition is lost through volatilization. Some of the mixed perfluoroacetal compositions can have these

advantages if the perfluoroacetal compounds in the mixture are judiciously selected, for example by empirically selecting those with the desired boiling points and low temperature viscosities.

The above-described features of the compositions of this invention advantageously contribute to their

usefulness as heat exchange liquids, such as thermal shock testing fluids. The perfluoroacetal compositions also have utility as hydraulic fluids, as pump fluids for corrosive environments, and as fluids for vapor-phase condensation heating for soldering and polymer-curing applications. Their low temperature viscosities are especially low compared with the viscosities of prior art perfluorinated polyether fluids which have a distribution of molecular weights and compositions. These low

viscosities render the perfluoroacetal compositions of this invention especially effective, particularly in comparison with the prior art fluids, as heat transfer media at low temperatures.

In another aspect of this invention, the

perfluoroacetal and perfluoroketal compositions are prepared by direct fluorination of their

perfluorinateable, saturated or unsaturated acetal or ketal precursors which can be fluorine-free or

partially-fluorinated and chlorine-free or partially chlorinated. ("Perfluorinateable" means the acetal or ketal precursor contains carbon-bonded hydrogen atoms which are replaceable with fluorine and any carbon-carbon unsaturation in the precursor can be saturated with fluorine.) The resulting perfluoroacetal or

perfluoroketal compounds can be made with the same number and spatial arrangement of carbon atoms as the precursors thereof. The fluorination can be carried out at a

temperature between -80°C and +150°C or at moderate or near ambient temperatures, e.g. -20°C to +50°C, preferably between -10°C and +40°C, with a stoichiometric excess of fluorine gas, which is preferably diluted with an inert gas, such as nitrogen, helium, argon, perfluoromethane, or sulfur hexafluoride, to minimize or avoid hazards and to control the amount of heat generated upon initial contact of the precursor with the fluorine. Due to the extreme exothermicity of the reaction, the fluorination must be carried out slowly unless provisions have been made for rapidly removing the heat of reaction. Submersion of the reactor in a cooled liquid bath is usually adequate for achieving commercially acceptable rates of reaction. It can be carried out in a reactor containing an ultraviolet radiation source or in the dark. Using the preferred temperature range, it is not necessary to have an

ultraviolet light source since the fluorine is

sufficiently reactive. If an ultraviolet light source is used, however, a wavelength between 250 and 350 nm is preferred. When the reactor is irradiated with an

exte rnal light source, a transparent window is needed which does not react with either fluorine or hydrogen fluoride. A quartz lens coated with a thin film of fluorinated ethylene-propylene copolymer works well. The fluorination is preferably carried out in an oxygen- and water-free environment and can be carried out in the presence of solid, particulate scavenger, such as sodium fluoride, for the hydrogen fluoride by-product generated. Alternatively, the fluorination can be carried out in an inert liquid, such as a fluorocarbon or chlorofluorocarbon liquid, as a reaction medium, or carried out with the use of both the scavenger and the inert liquid. The

fluorination is preferably carried out by using fluorine diluted with inert gas to directly perfluorinate precursor acetal in the inert liquid (and, for operational

advantages, in the absence of a hydrogen fluoride

scavenger and without requiring UV illumination) at a temperature and inert gas flow rate sufficient to

volatilize hydrogen fluoride by-product and enable its removal from the fluorination zone as it is generated, said flow rate preferably being, for example, at least 4 or 5 times as much as the flow rate of the fluorine gas per se. The yields of the perfluoroacetals by this preferred technique are surprisingly high in light of the belief heretofore that the precursor acetals were in a sense fragile and not susceptible to direct fluorination unless low temperatures and/or hydrogen fluoride

scavengers were used during fluorination to slow the reaction and minimize fragmentation and other

yield-reducing phenomena.

A class of perfluoroacetal compositions of this invention is that whose members consist or consist

essentially of one or of a mixture of perfluorinated acetal compounds which fall within the following

representational general formula:

wherein: and are each independently selected from

the group consisting of C₁ to C₈, preferably C₁ to C₆, linear or branched perfluoroalkyl, C₁ to C₈, preferably C₁ to C₆, linear or branched chloroperfluoroalkyl, and unsubstituted or lower alkyl-substituted

perfluorocycloalkyl or chloroperfluorocycloalkyl wherein the lower alkyl substituent has 1 to 4 carbon atoms and the numbe r of ring carbon atoms in the cycloalkyl is 4 to 6, preferably 5 or 6;

and

are each

independently selected from the group consisting of C₂ to C₄ linear or branched perfluoroalkylene and C₂ to C₄ linear or branched chloroperfluoroalkylene; each

_f is independently a fluorine atom or perfluoroalkyl with 1 to 4 carbon atoms, and is preferably perfluoromethyl or, more preferably a fluorine atom; x and w are each independently an integer of 0 to 4; y is an integer of 1 to 6,

preferably 1 to 3 ; z is an integer of 0 or 1; and the total number of carbon atoms in said compound can be 6 to 30, preferably at least 12, e.g. 12 to 17, and more preferably 13 to 14 because of the extremely low viscosity at low temperatures, e.g. less than about 300 centistokes at -70ºC, coupled with high boiling point, e.g. above about 175°C, that the compositions have when the total carbon atoms are 13 or 14. (The term "chloroperfluoro-" is used herein to describe a perfluoro moiety in which 1 or 2 fluorine atoms are replaced in a sense by chlorine atoms, e.g. as in the case of ClC₂F₄- or -CF₂ CF(CF₂ Cl)-.) The perfluoroacetal compositions preferably have a boiling point in the range of 160°C to 250°C, and more preferably in the range of 175°C to 200°C.

The perfluoroacetal compounds of this invention contain at least one perfluoro-1,1-alkylenedioxy unit, e.g. -OCF )O- in formula II, which can be located

approximately at the center of the perfluoroacetal

molecule, but a perfluoroacetal compound can contain two perfluoro-1,1-alkylenedioxy units separated by at least two catenary carbon atoms of a perfluoroalkylene moiety and each of the units located at approximately the center of a different molecular half of the compound. Here, "approximately at the center" means having about the same number, plus or minus about one, of perfluoroalkyleneoxy units on each side of the molecule (in the case of a single alkylenedioxy unit) or molecular half (in the case of two such units). The acetals having one

perfluoro-1,1-alkylenedioxy unit which is centrally

located are generally more easily prepared because their precursors are readily available materials.

A particularly useful subclass of the perfluoroacetal compositions of this invention is that whose members consist or consist essentially of one or a mixture of two or more perfluoroacetal compounds falling within the following representational general formula:

C_nF_2n+1(OC_mF_2m)_a-OCF[(CF₂)_pF]O-(C_m,F_2m,O)_bC_n,F_2n , ₊₁ Ill wherein: each n and n' is independently an integer of 1 to 6, each m and m' is independently an integer of 2 to 4, a and b are each independently an integer of 0 to 4, and p is 0 or 1 (if p is 0 then the central moiety is -OCF₂O- and if it is 1 then the central moiety is -OCF(CF₃)O-), each said compound preferably having 13 to 14 total carbon atoms, said composition having a viscosity at -70°C of less than about 300 centistokes, preferably less than about 200 centistokes.

In another aspect, this invention also provides a method of transferring heat from an article, such as an electronic component or device, to a cooling liquid, the method comprising directly contacting the article with an above-described perfluoroacetal composition of this

invention. This invention further provides a method of inducing a thermal shock to an article, such as an electronic

component or device, for example for purposes of testing the integrity or soundness of the article as described

earlier herein, the method comprising the following steps: a) heating a first bath of a heating liquid to a

temperature above ambient temperature;

b) cooling a second bath of a cooling liquid to a

temperature below ambient temperature; and

c) sequentially:

i) immersing the article in an initial bath which is one of said first and second baths and allowing said article to come to the temperature of said initial bath before removing said article from said initial bath, and

ii) then immersing said article in the other of said

first and second baths and allowing said article to come to the temperature of said other bath before its removal therefrom;

wherein said liquids are inert, thermally stable,

perfluorinated liquids, at least one of which is, but

preferably both are, a perfluoroacetal composition of this invention, more preferably the version which is a single molecular perfluoroacetal composition.

When a prior art fluorochemical made up of a mixture of molecular weights is used as a single thermal shock fluid, the lower molecular weight components of such fluid can boil off from the heating bath and the remaining higher molecular weight components can lead to increased viscosity through pollution or contamination of the cooling bath. The single molecular perfluoroacetal composition of this invention, which is essentially a single perfluoroacetal compound, does not have these disadvantages of prior art fluids (which have a distribution of molecular weights). The version of the perfluoroacetal composition of this invention which is a mixture of perfluoroacetal compounds also can overcome these disadvantages if each of the compounds in the mixture have the same or about the same boiling point, e.g. boiling points within a 10 to 15°C range, and viscosity, e.g. viscosities at -70°C of up to 300 cs, necessary to maintain the desired bath temperatures.

The perfluoroacetal compositions and perfluoroketal compositions of this invention may be prepared from their hydrogen-containing, saturated or unsaturated,

non-fluorinated or partially-fluorinated, non-chlorinated or partially-chlorinated hydrocarbon analog acetals and ketals which are perfluorinateable by direct fluorination. Although the perfluorinated products may contain small amounts of fluorinated materials having one or a f idual hydrogen atoms, the perfluoroacetal and perfluoroketal compositions of this invention are, except for any chlorine content,

essentially fully-fluorinated, i.e. perfluorinated, with a residual carbon-bonded hydrogen content of generally less than about 0.4 mg/g, usually less than 0.01 mg/g, and

preferably less than about 0.1 mg/g, e.g. 0.01 to 0.05 mg/g This residual hydrogen content can be lowered or essentially completely removed (as well as traces of undesired carboxyl ic acid derivatives such as terminal acyl fluoride groups resulting presumably from chain degradation reactions) upon treating at elevated temperature, e.g. at 150°C or higher, e.g. 175°C or even 260°C, the fluorinated product with fluorine, for example fluorine diluted with an inert gas such as nitrogen, such treatment being referred to hereinafter on occasion as the "polishing" finishing technique.

In one direct fluorination process (the "solids

fluorination technique") used to prepare the perfluoroacetal and perfluoroketal compositions of this invention, the precursor acetal or ketal starting material is contacted with fluorine diluted with an inert gas, such as helium or, preferably, nitrogen, at low initial concentrations of fluorine of about 5 to 25 volume %, preferably about 10 to 15 volume %, and at low initial temperature, which is preferably -20°C to 0°C. As the fluorination reaction proceeds, the fluorine concentration can be maintained constant or

gradually increased up to 50 volume % or even up to 100 volume %, and the reaction temperature is increased, e.g. to 40°C-60°C, and such conditions can be maintained until the precursor is perfluorinated. The precursor is fluorinated in the presence of a hydrogen fluoride scavenger, such as

potassium fluoride or, preferably, sodium fluoride. The scavenger may be in particulate form such as pellets or, preferably, powder. Such a perfluorination technique is described in U. S. Patent 4,755,567 (Bierschenk et al.), which description is incorporated herein by reference.

Generally, sufficient scavenger is utilized such that all of the hydrogen fluoride by-product generated in the

perfluorination process is scavenged. enger: precursor weight ratios of from about 1:1 to ab 1 have been found useful in fluorinating the precursor acetals or ketals.

Using this method, the precursor may be mixed with or coated on the scavenger and the mixture fluorinated in a

fluorination apparatus such as a stationary metal tube reactor, a rotating drum reactor, or a fluidized bed reactor, this technique generally giving yields of about 15 to 30 mol % of the desired perfluoroacetal or perfluoroketal

compound(s). Typical reaction times to obtain such yields vary from about 24 hours to about 48 hours, depending upon the reactor system utilized.

Another method of fluorination (the "liquids

fluorination technique") that can be used to make the

perfluoroacetal and perfluoroketal compositions of this invention involves making a very dilute dispersion, emulsion, or, preferably, solution of the precursor acetal(s) or ketal(s) in a liquid reaction medium, which is relatively inert to fluorine at the fluorination temperatures used, the concentration of the starting material thus being relatively low so as to more easily control the reaction temperature. The reaction mixture can also contain or have dispersed therein a sufficient quantity of hydrogen fluoride scavenger such as sodium fluoride or potassium fluoride to complex with all of the hydrogen fluoride formed. The scavenger :precursor weight ratio can be, for example, from about 0.5:1 to 7:1. The reaction mixture can be vigorously agitated while the fluorine gas is bubbled through it, the fluorine preferably being used in admixture with an inert gas, such as nitrogen, at a concentration of about 5 to 50 volume %, more preferably about 10 to 25 volume %, and being maintained in

stoichiometric excess throughout the fluorination, e.g. up to 15 to 40%, or higher, depending on the particular starting material and the efficiency of the equipment used, such as the stirrer. Yields generally in the range of about 30-77 mol %, and, with experience, as high as 65 to about 80 mol %, of the perfluoroacetal or perfluoroketal product may be achieved by this method. Suitable liquids useful as reaction media are chlorofluorocarbons such as Freon™ 113,

1,1,2-trichlorotrifluoroethane, and Freon™ 11,

fluorotrichloromethane, and chlorof luoroethe rs such as

2 , 5 , 5-t ri chlorope rfluoro-2-butyl tetrahydrofuran,

perfluoro-bis(chloroethyl)ether, and perfluorinated

polyepichlorohydrin liquids, which media generally will function as good solvents for non-fluorinated precursors, and Fluorinert™ electronic liquids FC-75, FC-72, and FC-40, perfluoroalkanes such as perfluoropentane and

perfluorodecalin, perfluoropolyethers such as Krytox™ and Fomblin™, perfluoroalkanesulfonyl fluorides such as

perfluoro-1,4-butanedisulfonyl fluoride and

perfluorobutanesulfonyl fluoride, and the perfluoroacetal compositions of this invention, and this latter group of media, i.e., perfluoroalkanes, etc., generally will function well as solvents for some precursors or as reaction media for forming dispersions of other precursors. Mixtures of such liquids can be used, e.g. to get good dispersion of precursor and intermediate reaction products. The reaction media are conveniently used at atmospheric pressure. Lower molecular weight members of the above classes of reaction media can also be used, but elevated pressures are then required to provide a liquid phase. The fluorination reaction is

generally carried out at a temperature between about -10°C to +50°C, preferably between about -10°C to 0°C if a hydrogen fluoride scavenger is used, and if such scavenger is not used, between about 0°C to 150°C, preferably about 0°C to 50°C, most preferably about 10°C to 30°C, the temperature being sufficient to volatilize the hydrogen fluoride

by-product and with the aid of the inert gas, flowing at a sufficient rate, cause the purging of the by-product from the fluorination reactor as it is generated. At these

temperatures, the liquids utilized as reaction media do not react appreciably with the diluted fluorine and are

essentially inert. The reaction medium and other organic substances may to some extent be present in the gaseous reactor effluent, and a condenser may be used to condense the gaseous reaction medium and such substances in the effluent and permit the condensate to return reactor. The condenser should be operated so as to minimize or prevent the return to the reactor of hydrogen fluoride by-product (which would have an adverse effect on yield of perfluorinated product if allowed to remain in the reactor during

fluorination). The return of the hydrogen fluoride can be minimized or prevented by selective condensation of the organic materials while allowing the hydrogen fluoride to pass through the condenser, or by total condensation into a separate vessel of both hydrogen fluoride and the organic materials followed, if desired, by separation of the hydrogen fluoride as the upper liquid phase and the return of the lower liquid phase. The reaction may be carried out in a batch mode, in which all of the precursor is added to the liquid prior to fluorination to provide a precursor

concentration of up to about 10% by weight, and the

fluorine-containing gas then bubbled through the

precursor-containing liquid. The reaction can also be carried out in a semi-continuous mode, in which the precursor is continuously pumped or otherwise fed neat, or as a diluted solution or dispersion or emulsion in a suitable liquid of the type used as a reaction medium, into the reactor, e.g. at a rate of about 1 to 3 g/hr into 400 mL of liquid reaction mixture, as fluorine is bubbled through, e.g. at a fluorine flow rate of about 40 to 120 mL/min and an inert gas flow rate of about 150 to 600 mL/min. The fluorination can also be carried out in a continuous manner: the precursor (either neat or dissolved or dispersed in a suitable liquid of the type used as a reaction medium to form a solution or

emulsion) being continuously pumped or otherwise fed into the reactor containing the reaction medium as the

fluorine-containing gas is introduced, as described above, and the stream of unreacted fluorine, hydrogen fluoride gas, and inert carrier gas being continuously removed from the reactor as is a stream of liquid comprising perfluorinated product, incompletely fluorinated precursor, and inert liquid reaction medium, and the necessary separations being made to recover the perfluoroacetal composition, and, if desired, with recycling of the unreacted fluorin d the incompletely fluorinated precursor.

In a liquids fluorination technique, an alternative method for fluorinating the precursors which are insoluble in the liquid fluorination medium involves adding a solvent to the precursor which allows limited solubility of precursor in the liquid fluorination medium. For clarity of illustration, 1,1,2-trichlorotrifluoroethane has been selected as the liquid fluorination medium; however, other highly fluorinated solvents can also be used. Typically, a mixture containing one part precursor, one part solvent and one part

1,1,2-trichlorotrifluoroethane will give a homogeneous solution. A solvent is selected which readily dissolves the precursor. Often it is possible to choose a solvent which will consume little, if any, of the fluorine gas.

Trifluoroacetic anhydride, trifluoroacetic acid, chloroform, 1,1,2-trichloroethylene and 1,1,2-trichloroethane work especially well.

The solution of precursor, solvent and 1,1,2-trichlorotrifluoroethane is metered into a vigorously stirred

fluorination reactor. As the precursor solution contacts the 1,1,2-trichlorotrifluoroethane in the reactor, an emulsion is formed. The resulting precursor droplets are in most cases sufficiently small that they react quickly with the fluorine gas with negligible side reactions. The amount of inert liquid medium in the reactor can be maintained at a constant level by addition of recycled or fresh liquid. The

perfluorinated product from the batch mode generally will have significant residual hydrogen, e.g. about 7 mg/g, whereas the perfluorinated product made by the continuous or semi-continuous mode will generally have less residual hydrogen, e.g. less than 0.1 mg/g. In general, the

continuous addition of precursor is preferred and provides a higher yield, better product quality, and more efficient use of fluorine, though the batch mode has similar advantages if the "polishing" finishing step is used.

Due to the extremely high exothermicity of the

fluorination reaction, a cooled liquid or ice bath is

generally employed in order that acce table rates of reaction may be achieved. When the reaction is complete, the reactor is purged of fluorine and the reactor contents are removed. In the solids fluorination technique, the reactor contents can be mixed with Freon 113 or Fluorinert FC-72 solvent, the resulting slurry filtered, and the solvent stripped, e.g. by vacuum distillation, to provide crude perfluorinated product. Where the fluorination is carried out by the liquids

fluorination technique in the presence of a hydrogen fluoride scavenger, the spent scavenger can be separated by filtration or decantation from the liquid reactor contents and the latter then distilled to separate the reaction medium from the crude perfluorinated product. Where the fluorination is carried out by the liquids fluorination technique without using the scavenger, the reaction product mixture can be distilled to recover the perfluorinated product.

The crude perfluorinated product can be treated with a base, e.g. sodium hydroxide, to remove acid and hydride impurities or treated, e.g. at a temperature above 150°C, by the polishing finishing technique to remove hydrogen and acid impurities and the so-treated product distilled. The order of these purification steps can be varied to obtain best results.

The precursor acetals used for preparation of the perfluoroacetal compositions of this invention can be

prepared in a variety of ways by reaction of alcohol(s) with appropriate co-reactants. Symmetrical acetals result upon heating two moles of a single alcohol with an aldehyde, e.g. formaldehyde, under acid catalysis, with removal of water during the reaction, as illustrated in Equation 1.

2ROH + R'CHO —> ROCHOR + H₂ O Eq . 1

Lower acetals can be converted to higher ones by heating with the higher alcohol under acid catalysis, as

illustrated in Equation 2.

2ROH + ROCHOR' —> ROCHOR + 2R'OH Eq. 2

A third route, to symmetrical acetals, as illustrated in Equation 3, involves basic conditions and is useful for hindered or acidic alcohols in which the above acid-catalyzed equilibria are unfavored. Under phase transfer catalysis, a mixture of NaOH, or preferably KOH, and the alcohol displacees chloride from methylene chloride.

2ROH + 2KOH + CH₂Cl₂ —> ROCH₂ OR + 2KCl +2H₂O Eq. 3

The preferred route to asymmetric acetals requires prior formation of the alpha-chloroalkyl derivative of one

alcohol and subsequent reaction with the second alcohol under basic conditions, as illustrated in Equations 4 and 5.

ROH + R'CHO + HCl —> ROCHCl + H₂O Eq. 4

ROCHCl + R"OH + KOH —> ROCHOR" + KCl +H₂O Eq. 5

This latter reaction is also the preferred method to

prepare precursors containing two alkylenedioxy units.

Another route to asymmetric acetal is the reaction of a vinyl alkyl ether with an alcohol under acid catalysis, as illustrated in Equation 6.

ROH + CH₂ =CHOR' —> ROCHOR' Eq. 6

This route of Equation 6 can also be used to prepare

precursors containing two alkylenedioxy units, as

illustrated in Equation 7.

2ROH + CH₂=CHO-R-OCH=CH₂ —> ROCHO-R-OCHOR Eq. 7

The other methods illustrated in Equations 1-3 can be used for preparing those precursors with two of such units, although yields are lower due to competing

oligomerization.

In the schemes illustrated in above Equations 1 to 7, mixtures of alcohols, aldehydes, and/or acetals can be used as reactants to prepare mixtures of precursors that are fluorinated to make perfluoroacetal compositions of this invention which are mixtures of perfluoroacetal

compounds. Thus, the process of Equation 1 can be modified by use of two different alcohols, as illustrated in

Equation 8.

4ROH + 4R'OH + 4R"CHO —> 2ROCHOR' + ROCHOR +

R'OCHOR' + 4H₂O Eq. 8

Examples of alcohols which can be used in the above illustrated schemes are monhydridic alcohols, such as methoxyethanol, ethoxyethanol, butoxyethanol, diethylene glycol methyl ether, diethylene glycol ethyl ether,

diethylene glycol butyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol butyl ether, tetraethylene glycol methyl ether. tetraethylene glycol ethyl ether, tetraethylene glycol butyl ether, pentaethylene glycol methyl ether,

pentaethylene glycol ethyl ether, pentaethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether,

dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol butyl ether, tripropylene glycol methyl ether, tripropylene glycol ethyl ether and

tripropylene glycol butyl ether.

Useful precursor acetals for conversion by direct fluorination to the perfluoroacetals of this invention include each of those in the following list of materials and mixtures of 2, 3, or more thereof:

CH₃ (CH₂ )₅OCH₂O(CH₂ )₅CH₃

CH₃ (CH₂ )₃OCH₂O(CH₂CH₂O)₂ (CH₂ )₃CH₃

CH₃ (CH₂ )₆OCH₂O(CH₂ 6CH₃

CH₃ (CH₂ )₂ (OCH₂CH₂ )₃OCH₂O(CH₂CH₂O)₃ (CH₂ )₂CH₃

CH₂=CHCH₂ (OCH₂CH₂ )₃OCH₂O(CH₂CH₂O) ₃CH₂CH=CH₂

CH₂=CHCH₂O(CH₂ )₃OCH₂O(CH₂ )₃OCH₂CH=CH₂ CF₃CHFCF₂O(CH₂ )₃OCH₂O(CH₂ )₃OCF₂CHFCF₃

CH₃ (CH₂ )₂ (OCH₂CH₂ )₄OCH₂O(CH₂CH₂O)₄ (CH₂ )₂CH₃

CF₃ CHFCF₂ OC₃ H₆ OCH₂ OC₃ H₆ OCF₂ CHFCF₃ and

CH₃[OC₃H₆]₂OCH₂O[C₃H₆O]₂CH₃ (where C₃H₆ can be either -CH₂CH- or -CHCH₂- or a mixture of both)

CH₃ CH₃ ClCH₂CH₂OCH₂CH₂OCH₂OCH₂CH₂OCH₂CH₂Cl

CH₃ (CH₂)₃OCH₂CH₂OCH₂OCH₂CH₂O(CH₂ )₃CH₃

CH₃ (CH₂ )₃ (OCH₂CH₂ )₂OCH₂O(CH₂CH₂O)₂(CH₂ )₃CH₃ CH₃ (CH₂ )₃OCH₂OCH₂C-CCH₂OCH₂O(CH₂ )₃CH₃

CH₃CH₂(OCH₂CH₂ )₂OCH₂O(CH₂CH₂O)₂CH₂CH₃

CH₃ (CH₂ )₂(OCH₂CH₂ )₂OCH₂O(CH₂CH₂O)₂(CH₂ )₂CH₃l CH₃OCH₂CH₂OCH₂(OCH₂CH₂)₃OCH₂OCH₂CH₂OCH₃

CH₃CH₂OCH₂CH₂OCH₂(OCH₂CH₂)₃OCH₂OCH₂CH₂OCH₂CH₃ CH₃CH₂OCH₂CH₂OCH₂(OCH₂CH₂ )₂OCH₂OCH₂CH₂OCH₂CH₃ CH₃OCH₂CH₂OCH₂O(CH₂CH₂O)₂(CH₂ )₃CH₃

CH₃CH₂ (OCH₂CH₂ )₂OCH₂O(CH₂)₅CH₃

CH₃CH₂OCH₂O(CH₂CH₂O)₃ (CH₂ )₃CH₃

CH₃ (CH₂ )₃OCH₂CH₂OCH(CH₃ )OCH₂CH₂O(CH₂)₃CH₃

CH₃ (CH₂)₃OCH₂CH₂OCH(CH₂CH₂CH₃ )OCH₂CH₂O(CH₂ )₃CH₃ (CH₃ )₃COCH₂CH₂OCH₂OCH₂CH₂OC(CH₃ )₃

C₃H₇OCH₂CH₂OCH(CH₂Cl)OCH₂CH₂OC₃H₇

CH₃OCH₂CH₂OCH₂CH(CH₃ )OCH₂OCH(CH₃ )CH₂OCH₃

CH₃CH₂OCH₂CH(CH₂Cl)OCH₂OCH(CH₂Cl)CH₂OCH₂CH₃

CH₃CH₂OCH₂CH₂OCH₂CH₂OCH₂OCH₂CH₂O(CH₂ )₃CH₃

C₇F₁₅CH₂OCH₂OCH₂C₇F₁₅

C₃F₇CH₂OCH₂CH₂OCH₂OCH₂CH₂OCH₂C₃F₇ Representative examples of the perfluoroacetal compounds of this invention include the perfluorinated counterparts of the precursor acetals listed above. Where the precursors have unsaturation, the corresponding perfluoroacetals thereof are saturated.

The perfluoroacetal compositions of this invention generally have surprisingly low viscosities at low

temperatures compared with the viscosities of commercial GALDEN^R perfluoropolyether immersion fluids of comparable molecular weight, which commercial fluids contain a distribution of molecular compositions. These low

viscosities render the perfluoroacetal compositions of this invention especially effective, particularly in comparison with the prior art fluids, as heat transfer media at low temperatures. A preferred utility for the perfluoroacetal compositions of this invention is in cooling an article to a temperature below ambient, e.g., a temperature far below ambient temperature, such as -65°C. Such cooling may take place as part of a thermal shock method which can be used to temper or test a material. An especially preferred utility is use in the thermal shock method of this invention, which is preferably carried out in accordance with Condition B or C of U.S. Military

Standard MIL-STD-883C, Notice 4, method 1011.6, incorporated herein by reference, with a perfluoroacetal composition of this invention substituted for both of the fluids specified in that procedure. The thermal shock method may also be carried out using two thermal shock liquids, one being a conventional electronic testing fluorochemical liquid which may be used in either of the two baths, and the other being a perfluoroacetal

composition of this invention which is used in the

remaining bath. Examples of suitable conventional liquids include the inert, perfluorinated organic compounds available from 3M as FLUORINERT^™ Electronic Liquids described in product bulletin No. 98-0211-2267-0 (161 )NPI issued February 1986.

The thermal shock method of this invention using a single thermal shock liquid can be carried out, for example, as follows in accordance with MIL-STD-883-1011.6, Condition C. The article, such as an electronic component or device to be tested, can be preconditioned by being immersed in a heated bath of a perfluoroacetal composition of this invention at an elevated temperature between 150°C and 160°C for a minimum of 5 minutes. Immediately upon conclusion of the preconditioning period, the article is transferred to a cooled bath of the perfluoroacetal composition at a temperature between about -65°C and

-75°C. The article is held at the low temperature for 5 minutes, at the end of which time it must itself reach -65°C, and it is then transferred back to the heated bath of the perfluoroacetal composition. The article remains at the high temperature for 5 minutes. Transfer time from the high temperature bath to the low temperature bath and from the low temperature bath to the high temperature bath is less than 10 seconds. The duration of the test is generally about 15 complete cycles, where one cycle consists of immersion in and removal from the heated bath of the perfluoroacetal composition and immersion in and removal of the article from the cooled bath of the

perfluoroacetal composition. After completion of the final cycle of a thermal shock test, an external visual examination of the article is generally performed without magnification or with a magnifying viewer. Typical effects of thermal shock on defective articles include cracking and delamination of substrates or wafers, opening of terminal seals and case seams, and changes in

electrical conductivity due to moisture or to mechanical displacement of conductors or insulating materials. The electronic performance of the electronic components can be determined and compared with the electronic performance of the article prior to thermal shock testing.

In an alternative thermal shock method of this invention using two thermal shock liquids, a

perfluoroacetal composition of this invention can be placed in the heating bath of a thermal shock apparatus and a different perfluorinated, inert liquid, such as a conventional, perfluorinated, inert thermal shock testing liquid, e.g., FLUORINERT FC-77, is placed in the cooling bath. In this alternative method, the manipulative steps and conditions used can be the same as those described above for the single thermal shock method. As the

alternative thermal shock method is practiced, the

perfluoroacetal composition, when carried over into the cooling bath, will generally not raise the viscosity of the cooling bath to the extent that a conventional thermal shock heating liquid, e.g., FLUORINERT FC-40, does over extended use.

In another alternative thermal shock method of this invention using two thermal shock liquids, a

perfluoroacetal composition of this invention can be placed in the cooling bath of a thermal shock apparatus and a different perfluorinated, inert liquid, such as a conventional, perfluorinated, inert, thermal shock testing liquid, e.g., FLUORINERT FC-40, is placed in the heating bath. In this alternative method, the manipulative steps and conditions used can be the same as those described above for the single thermal shock method. As the thermal shock method is practiced, the perfluoroacetal composition of this invention, when carried over into the heating bath, will generally not volatilize from the heating bath to the extent that a conventional thermal shock cooling liquid, e.g. FLUORINERT FC-77, does over extended use.

While the methods of this invention of inducing a thermal shock can be applied to almost any article which is immersible in the baths used in the method, the methods are preferably used to induce a thermal shock in an electronic device or component to evaluate the electronic component's response to the thermal shock. Examples of electronic components and devices include integrated circuits, integrated circuit assemblies, micro-electronic components and devices, ceramic and plastic carriers for electronic chips, and assemblies of micro-electronic components, e.g., integrated circuits, transistors, diodes, resistors, capacitors, and the like.

Apparatus suitable for performing a thermal shock test are available from many manufacturers, e.g., Blue M Engineering, Blue Island, IL; Cincinnati Sub-zero

Products, Inc., Cincinnati, OH; Maruberi, Santa Clara, CA; Ransco Industries, Oxnard, CA; Standard Environmental

Systems, Inc., Totowa, NJ; and Thermodynamic Engineering, Inc., Camarillo, CA. Each of these apparatus possesses particular features and makes different demands on the fluid, especially in the cold bath. While some baths in such apparatus can tolerate a higher cold bath viscosity than others (e.g., at a cold bath temperature of -65°C), others tolerate a maximum in viscosity of about 600 cs at -70°C. Preferred perfluoroacetal compositions used in this invention have cold bath viscosities below the above value and thus have general utility in such apparatus.

This variability in apparatus apparently relates to the observation that fluid in the vicinity of the cooling coils or panels of the apparatus tends to be somewhat cooler (e.g., -80°C or -85°C) than the set temperature of the cold bath and, as a result, problems in maintaining the set point can occur due to thickening of this fluid and/or due to the formation of an insulating coating on the coil. For prior art fluids and, by inference, many of the fluids of this invention which have low viscosity at -70°C, but not at -85°C, this can be overcome by increased mechanical agitation. However, in order for a fluid to be most useful in heat transfer applications, good fluidity, i.e., low viscosity, at temperatures as low as -85°C is especially desirable. Single molecular weight

perfluoroacetal compositions of this invention offer an advantage over fluids which contain higher molecular weight components which can selectively congeal on cooling coils and also have the advantage that thermal or

mechanical losses in use do not change the composition (and, therefore, properties) of that volume or residual amount remaining. The design characteristics and

specifications for a number of commercially available apparatus are described in a product bulletin of Ransco Industries, Oxnard, CA, entitled "Thermal Shock

Temperature Cycling, Product Bulletin 7000 Series".

Minor amounts of optional components may be added to the perfluoroacetal compositions, e.g., thermal

stabilizers, dyes, etc., to impart particular desired properties.

The perfluoroacetal compositions of this invention can also be as additives for other inert fluorochemical liquids, used, for example, as thermal shock fluids, hydraulic fluids, heat exchange media, and other working fluids, to modify or adjust their viscosities or pour points.

This invention is further illustrated by the

following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. The pour points given in the examples below were estimated by first immersing a

thermometer in a sample of distilled liquid product contained in a glass vial and then placing the vial in a liquid nitrogen or dry ice bath to cool the sample to a solid, glassy state. The vial was then allowed to warm slowly and the temperature at which complete fluidity was attained was noted and recorded as the pour point. The viscosity in these examples was measured by conventional means using a Wescan viscometer timer and Cannon-Fenske viscometer tubes, as described in ASTM D446-74 (reapproved in 1979). Stable low temperatures for the viscosity measurements were achieved using Fluorinert FC-75 as the bath medium; the temperature of the perfluoroacetal composition was measured with a resident thermocouple.

EXAMPLES

Example 1

A cylindrical brass reactor (about 7.5 cm in diameter and about 30 cm long, with a sealed bottom and a removable head) was fitted with a copper tube through the head reaching to within about 5 cm of the bottom as the gas inlet and a hole in the head was fitted as the exit. An intimate mixture of 30.0 g (0.139 mol)

bis(n-hexyloxy)methane (prepared by the procedure

described in Example 7 using methylene chloride as a source of the formal moiety) and 210 g (5.0 mol) NaF powder was placed in the reactor, which was then installed horizontally in a water-ethylene glycol bath and rotated at about 20-30 rpm. Fluorine and nitrogen were mixed prior to entry. The bath was cooled to -17°C and the gas mixture of 60 mL/min fluorine and 240 mL/min nitrogen was begun. An exotherm of abouat 2 to 5°C was registered by an internal thermocouple. After 22 hr, the exotherm was <1°C and the temperature was increased by 10-15°C

increments over the next 8 hrs to 55°C. At hour 25, the nitrogen was reduced to 120 mL/min and, at hour 29, to 60 mL/min. The fluorine was stopped at the 30th hr. The resulting white powder (364.2 g) was combined with 7.0 g of condensate from a cooled trap (containing dry ice) in line after the condenser and was washed three times with 500 mL Freon 113. The combined Freon 113 washings was stripped on a rotary evaporator at less than 25°C. The residue , 72 . 4 g , was distilled on a short path to 19 . 4 g (19%) of 88% pure perfluoro-bis (n-hexyloxy)methane

(structure confirmed by fluorine nuclear magnetic

resonance and gas chromatography-mass spectrometry), having a boiling range of 120-130° C/60 Torr, a pour point of -70°C, and a viscosity greater than 2000 cs at -85°C. 47.4 g of higher-boiling materials was also isolated.

Examples 2, 3, and 4

Using the fluorination technique of Example 1 and formals prepared by the methylene chloride route of

Example 7, three perfluoroacetal compositions were made: Ex. 2, perfluoro-bis ( cyclohexyloxy)methane, having a boiling range of 105-130°C/60 Torr and a pour point of -45°C, was prepared from bis(1,1-cyclohexyloxy)methane: Ex. 3, perfluoro-bis(2,4-dichlorocyclohexyloxy)methane, having a boiling point of 150° C/40 Torr and a pour point of -25°C, was prepared from bis(2,4-dichlorophenoxy)- methane: and Ex. 4, [n-C₄ F₉ (OC₂ F₄ )₂ O]₂ CF₂ , having a boiling point of 130-155°C/25 Torr, a pour point of -75°C, and a viscosity greater than 2000 cs at -85°C, was

prepared from the corresponding hydrocarbon acetal.

Example 5

A mixture of 130.2 g (1.0 mol) isooctyl alcohol, 92 ml (1.05 mol) CH₃ OCH₂ OCH₃, and 1 g p-toluenesulfonic acid was stirred at reflux for 18 hr. The internal temperature was now 60°C. Gas-liquid chromatography showed 30% unreacted isooctyl alcohol, 41% presumed

1-isooctyloxy-1-methoxy methane, and 13%

bis(isooctyloxy)methane, the latter as three distinct peaks on the SE-52 chromatographic column. The reflux condenser was removed and the mixture was heated for 3 hr. The temperature rose rapidly to 220°C. Gas-liquid

chromatography now showed 13% isooctyl alcohol, 2%

1-isooctyloxy-1-methoxy methane, and 84% bis(isooctyloxy)- methane. The p-toluene sulfonic acid was neutralized with Na₂ CO₃ and the filtered product was distilled to 102.3 g (75%) of pure bis (isooctyloxy)methane, bp 110-120° C/0.8 Torr.

Perfluoro-bis(isooctyloxy)methane, having a boiling range of 120-140°C/60 Torr and a pour point of -40°C, was prepared from the above-prepared bis(isooctyloxy)methane using the fluorination technique of Example 1.

Example 6

In a 250 ml glass flask, a solution of 20.3 g (0.025 mol) bis(1,1-dihydroperfluorooctyloxy)methane (prepared from the alcohol by the method of Example 7 using

methylene chloride) in 80 mL Fluorinert FC-75 was treated with 8.0 g (0.154 mol) NaF. The mixture was flushed with nitrogen and chilled in an ice bath to 10°C. A slow feed (approximately 50-100 mL/min) of 9% fluorine in nitrogen was maintained over about 40 hr, using approximately 18 g fluorine. Gas-liquid chromatography and mass spectrometry showed two products in a 5:1 ratio, the larger being perfluoro-bis(perfluoro-octyloxy)methane (920 mol wt) and the smaller being monohydrido de rivative ( s ) thereof .

Filtration and distillation gave a main cut of 10.2 g, bp 140-145°C/40 Torr, melting point -10°C. Gas-liquid chromatography showed two main isomers and a minor amount of the monohydrides. The total yield including other fractions was approximately 13g (56%).

Example 7

A mixture of 1645 g (13.9 mol) 2-butoxyethanol, 225 g (7.5 mol) paraformaldehyde, 2.0 g p-toluenesulfonic acid, and 1.5 liters toluene was stirred at reflux under a

Dean-Stark trap, with steady evolution of water. After 16 hr, 10 g more paraformaldehyde was added and, at 18 hr, 20 g of 37% formaldehyde was added, in attempts to force the reaction to completion. Conversion, as determined by gas-liquid chromatography was greater than 95% and the mixture was cooled, washed with water containing a few grams NaOH, and the toluene allowed to evaporate. The residue was distilled, yielding 1430 g (83%) of

bis(2-butoxyethoxy)methane, bp 100-110°C at 0.5 Torr.

Bis(2-butoxyethoxy)methane was also prepared from methylene chloride and 2-butoxyethanol as follows. A mixture of 590.9 g (5.0 mol) 2-butoxyethanol, 1120 g (20 mol) KOH, 3 g Adogen^™ 464 quaternary ammonium salt, and 1 liter tetrahydrofuran was stirred for 30 min. The

temperature rose to 45°C. Careful addition of 750 ml (11.5 mol) methylene chloride and continued stirring at 55°C for 18 hr gave complete conversion of the alcohol to bis (2-butoxyethoxy)methane. The mixture was filtered with additional methylene chloride and distilled, yielding 552 g (96%) bis(2-butoxyethoxy)methane, bp 106°C/0.25 Torr, which is a product equivalent to that prepared above using formaldehyde as the source of the formal moiety, -OCH₂O-.

A 600 mL Parr reactor of Monel metal was equipped with a 0.6 cm diameter Monel^™ metal gas feed line (for premixed fluorine and nitrogen) with its outlet being about 2.5 cm from the bottom of the reactor, a 0.15 cm diameter nickel organic feed line with its outlet being about 7.5 cm below the top of the reactor, and a condenser cooled by the same bath as the jacket. The condenser was a 50 cm long straight double-tube construction, the inner tube having a diameter of about 1.2 cm and the outer tube having a diameter of about 2.5 cm. Gases from the reactor are cooled as they flow through the inner tube by

ethylene-glycol-water flowing in the annulus between the tubes. This reactor was charged with 450 mL Freon 113 and 105 g (2.5 mol) NaF. The reactor was purged with nitrogen (175 mL/min) for 1 hr while stirring at 3°C. Fluorine was introduced into the nitrogen stream at 35 mL/min. After 15 min, a solution of 15.7 g (0.063 mol) of the above prepared bis(2-butoxyethoxy)methane diluted to 200 mL with Freon 113 was placed in a syringe pump and addition of the resulting solution was started at 9.2 mL/hr. The

additions were maintained over the next 22 hr and after the organic addition was complete the fluorine addition was continued for 15 min more. The NaF and NaHF₂ were filtered from the reaction product mixture, washed well with Freon 113, which was stripped at less than 25°C on a rotary evaporator, and the combined filtrate and washings were distilled, yielding 26.0 g (55%) of perfluoro-bis-(2- butoxyethoxy)methane, which was 95% pure as determined by gas-liquid chromatography. This perfluoroacetal product had a boiling range of 100-110°C/40 Torr, boiling point of 183°C, pour point of -95°C, and viscosities of 147 cs, 504 cs, and 858 cs at -70°C, -80°C, and -85°C, respectively. (In another run, the product had viscosities of 117 cs and 690 cs at -70°C and -85°C, respectively). Traces of acid fluoride and hydrides (0.02 mg/g) were present ( as found by infra-red and proton nuclear magnetic resonance

analyses). The perfluoroacetal product was purified by stirring it with hot, aqueous KOH (25%) for 18 hrs, then washing the separated product with water and drying the washed product over silica gel. In another run, the distilled residue was purified by bubbling into it for 5 hrs at 175°C a mixture of fluorine diluted with nitrogen. Both purification procedures gave colorless, odorless, thermally stable perfluoro-bis(2-butoxyethoxy)methane.

The thermal stability was determined by heating the purified product with aqueous sodium acetate for 22 hrs. at 180°C in a closed, stainless steel tube and

subsequently analyzing the aqueous layer for released fluoride ion, low fluoride ion content being indicative of thermal stability.

In a similar fluorination at -5°C (using a condenser temperature of about -5°C), bis (2-butoxyethoxy)methane precursor was fed into the reactor as an undiluted liquid to the mixture of NaF and Freon 113.

In another variation of the fluorination, the

precursor diluted in Freon 113 was fed to a mixture of 15.7g NaF in Freon 113 and the fluorination carried out at -3°C with the condenser at -3°C (resulting in 51% yield).

In another variation of the fluorination, the

precursor diluted in Freon 113 was fed to a mixture of NaF and Freon 113 at -10°C (resulting in 42% yield compared to essentially no yield in a run when no NaF was used). In these runs, the condenser temperature was set at -25°C.

In another variation of the fluorination, the precursor was fed (diluted in Freon 113) to a mixture of Freon 113 and NaF at 18°C with the condenser set at -25°C (resulting in 50% yield compared to a yield of 77% from a run where no NaF was used). Another run without NaF at 0°C gave a 65% yield.

In another variation, the precursor was fed undiluted into Fluorinert FC-72 at 18°C (58% yield), and in another, fed diluted in Freon 113 into a slurry of NaF and

Fluorinert FC-75 at 18°C and in another, fed diluted in Freon 113 into perfluoro-bis (2-butoxyethoxy)methane at 18°C. In these runs, the condenser was set at -25°C.

In another variation, the precursor was fed undiluted into Fluorinert FC-75 at 70°C (55% yield) and in another run, fed undiluted into Fluorinert FC-87 at 20°C (42% yield). In these runs, the condenser was set at about -25°C.

In another variation, the reactor was charged

initially with 15.7 g bis(2-butoxyethoxy)methane, 105 g NaF, and 400 mL Freon 113 and cooled to -8°C with the condenser set at -8°C. A flow of 30 mL/min F₂ and 120 mL/min N₂ was continued for 20.5 hours. The crude product was isolated as above. H-nmr analysis showed the product contained 7 . 1 mg H/g liquid, corresponding to an average composition of C₁₃ H₅ F₂₃ O₄. Gas-liquid chromatography showed little perfluoroacetal; instead the analysis revealed a series of many small peaks at retention times intermediate between those of the perfluoroacetal and the hydrocarbon acetal precursor. In a 200 mL vessel of Monel metal equipped with a water-cooled condenser, 25.0 g of the crude product was exposed to a gas flow of 20 mL/min F₂ and 80 mL/min N₂ for 0.5 hr at 50°C, then 2.6 hr at 100°C, 1.6 hr at 150°C, and 2.0 hr at 175°C. Distillation of the residue (16.4 g) yielded 12.7 g (41%) of

perfluoro-bis-(2-butoxyethoxy)methane. H-nmr indicated it contained 0.3 mg H/g liquid.

Perfluoro-bis(2-butoxyethoxy)methane was also

prepared by the solid fluorination technique of Example 1, the yield of the product being about 20%.

Example 8

A mixture of 150 g (1.5 mol) n-hexanol and 122 g (1.5 mol, 37%) formalin was treated with 140 g HCl gas over 3 hr. The resulting chloromethyl hexyl ether (172 g, 73%) was used directly. A mixture of 147.4 g (1.1 mol)

2-(2-ethoxyethoxy)ethanol, 130 g (1.3 mol), and 275 mL acetoni trile was heated to 65°C and the above chloromethyl hexyl ether was added slowly, followed by refluxing

overnight. Gas-liquid chromatography indicated 12%

unreacted ROCH₂Cl and another 14 g of the alcohol was added. After an additional hour, the mixture was cooled, washed with water, and the product was dried in methylene chloride over Mg₂ SO₄ and distilled to 205.6 g (75%)

3,6,9,11-tetraoxaheptadecane, bp 126°C/0.5 Torr.

The tetraoxaheptadecane, prepared as described above, was fluorinated by the liquids fluorination technique of Example 7 at about -5°C in the presence of NaF to produce C₆F₁₃OCF₂O(C₂F₄O)₂C₂F₅, which had a boiling range of

75-88°C/11 Torr, boiling point of 170°C, viscosities at -70 and -85°C of 237 cs and >2500 cs, respectively, and pour point of -80°C.

Examples 9-27

Using the liquids fluorination technique of Example 7 at about -5°C in the presence of NaF, different

perfluoroacetal compositions, each containing a single perfluoroacetal compound listed below (except as

indicated) together with properties of the composition, were prepared from corresponding precursor acetals (made by the routes illustrated by Equations 1, 2, or 3 or by Equations 4 and 5, supra) which were saturated except as noted.

9. CF₃(CF₂)₃OCF₂O(C₂F₄O)₂(CF₂)₃CF₃, boiling range of

100-120°C/46 Torr, boiling point of 173°C, pour point of -90°C, and viscosities at -70°C and -85°C of 148 cs and >2000 cs, respectively.

10. (cyclo-C₆F₁₁O)₂CF₂, boiling range of 100-120°C/20

Torr, pour point of -60°C, made from

diphenoxymethane. 11. (cyclo-C₆F₁₁CF₂O)₂CF₂ , boiling range of 95-115° C/10 Torr, pour point of -60°C, and viscosity at -70°C of >2000 cs, made from dibenzyloxymethane.

12. [CF₃ (CF₂ )₂(OC₂F₄ )₃O]₂CF₂ , boiling range of

110-125° C/8 Torr.

13. [CF₃(O-isoC₃F₆ )₂O]₂CF₂ , boiling at 120°C/35 Torr, pour point of -75°C, and viscosity of 1111 cs at -70°C.

14. (ClC₂F₄OC₂F₄O)₂CF₂ , boiling range of 155-170° C/740 Torr, and viscosities of 55 cs and 398 cs at -70°C and -85°C, respectively.

15. [C₂F₅(OC₂F₄ )₂O]₂CF₂ , boiling range of 100-110° C/60 Torr, boiling point of 176°C, pour point of -85°C, and viscosities of 106 cs, 469 cs, and 1531 cs at -70°C, -80°C, and -85°C, respectively.

16. [CF₃ (CF₂ )₂(OC₂F₄ )₂O]₂CF₂ , boiling at 120°C/35 Torr, pour point of -85°C, and viscosities of 429 cs and >2000 cs at -70°C and -85°C, respectively.

17. CF₃OC₂F₄OCF₂(OC₂F₄ )₃OCF₂OC₂F₄OCF₃ , boiling at

115° C/30 Torr, pour point of -95°C, and viscosities of 162 cs and 1500 cs at -70°C and -85°C,

respectively.

18. CF₃OC₂F₄OCF₂O(C₂F₄O)₂ (CF₂ )₃CF₃ , boiling at 90°C/40 Torr, pour point of -85°C.

19. C₂F₅OC₂F₄OCF₂(OC₂F₄ )₃OCF₂OC₂F₄OC₂F₅ , boiling at

120-140°C/40 Torr.

20. C₂F₅OC₂F₄OCF₂(OC₂F₄ )₂OCF₂OC₂F₄OC₂F₅ , boiling range of 90-110°C/15 Torr, boiling at 190° C/740 Torr, and viscosities of 274 cs and 2375 cs at -70°C and -85°C, respectively.

21. CF₃(CF₂)₃(OC₂F₄)₃OCF₂OC₂F₅, boiling range of

70-90°C/15 Torr, boiling point of 165°C, and

viscosities of 120 cs and 750 cs at -70°C and -85°C, respectively.

22. (n-C₇F₁₅O)₂CF₂, boiling range of 125-140° C/24 Torr, boiling point of 211°C, and melting point of -50°C. 23. [(CF₃)₂CFCF₂OC₂F₄O]₂CF₂, boiling range of 70-110° C/25 Torr, and viscosities of 240 cs and 1015 cs at -70°C and -80°C, respectively.

24. [(CF₃)₃COC₂F₄O]₂CF₂, boiling range of 80-88° C/17

Torr, boiling point of 183°C, and pour point of

-80°C, and viscosity of 2600 cs at -70°C.

25. [CF₃(CF₂)₃OC₂F₄O]₂CFCF₃, boiling range of 85-95° C/40 Torr, and viscosities of 180 cs and 2504 cs at -70°C and -80°C, respectively.

26. An approximately equimolar mixture of

(C₂F₅OC₂F₄OC₂F₄O)₂CF₂ and (C₄F₉OC₂F₄O)₂CF₂, made by fluorination of a mixture of 11.2g and 10. Og of the respective hydrocarbon precursors, boiling at 178°C and having a viscosity of 104 cs and 395 cs at -70°C and -80°C, respectively.

27. A ternary mixture of approximately one part

(C₂F₅OC₂F₄OC₂F₄O)₂CF₂, one part (C₄F₉OC₂F₄O)₂CF₂, and two parts C₄F₉OC₂F₄OCF₂OC₂F₄OC₂F₄OC₂F₅, made by fluorination of the reaction product of an equimolar mixture of C₂H₅OC₂H₄OC₂H₄ OH and C₄H₉OC₂H₄OH with formaldehyde, said fluorinated mixture boiling at 179°C and having viscosities of 87 cs and 340 cs at -70°C and -80°C, respectively.

Example 28

Four hundred g butoxyethoxyethanol (2.5 mol), 48 g paraformaldehyde (1.6 mol), 300 ml benzene and 5 g ion exchange resin (acid form) were placed in a 1 liter stirred flask. A water separator attached to a reflux condenser was used to collect the water produced as the alcohol and aldehyde reacted. After approximately 6 hr, the reaction was complete and the solution was filtered to remove the resin. Vacuum distillation of the solution to

120°C gave 414 g of a product (99% yield) which was essentially free of benzene and unreacted starting

materials.

The hydrocarbon product was fluorinated in a 22-liter stirred tank reactor which contained 6 liters of 1,1,2- trichlorotrifluoroethane and 1300 g sodium fluoride powder. A gas dispersion tube in the bottom of the reactor provided an inlet for the fluorine and nitrogen gases. The hydrocarbon reactant (275 g) was diluted with 1,1,2-trichlorotrifluoroethane, in a separate vessel, to give a total volume of 700 ml. This solution was metered into the fluorination reactor over a 20-hour period. The reactor temperature was maintained at 0°C with external cooling throughout the reaction while the fluorine flow was set at a leval 10% higher than that required to theoretically replace all of the hydrogens on the material entering the reactor. Upon completion of the reaction, the fluorine was turned off and the reactor was removed from the low temperature bath and purged for 30 min with nitrogen (2 liters/min) to remove the unreacted fluorine.

Filtration of the reaction product followed by distillation to remove the 1,1,2-trichlorotrifluoroethane gave 642 g of a highly fluorinated fluid (80% yield).

Treatment of the fluid at 260°C with 30% fluorine for several hours gave a perfluorinated fluid, b.p. 226.5°C, having an elemental analysis and F-nmr spectra consistent with the following structure: CF₃CF₂CF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂- CF₂CF₃

Example 29

A mixture of 400 g triethylene glycol monoethyl ether (2.2 mol), 48 g paraformaldehyde (1.6 mol), 150 ml

toluene, and 10 g of an acid ion exchange resin was refluxed for 6 hr in a 1 liter flask equipped with a water separator and reflux condenser. Filtration of the product followed by distillation gave a quantitative yield of the desired product.

Fluorination of 201 g of the material in a stirred liquid fluorination reactor containing 6 liters of

1,1,2-trichlorotrifluoroethane and 1055 g sodium fluoride gave 401 g fluid in an 18 hr reaction at 0°C.

Distillation of the crude product mixture gave 355 g of perfluorinated fluid, bp 217°C, the elemental analysis and F-nmr spectra of which was consistent with the followingstructure:

CF₃ CF₂ OCF₂ CF₂ OCF₂ CF ₂ OCF ₂ CF₂ OCF ₂ OCF ₂ CF₂ OCF₂ CF₂ OCF ₂ - CF₂ OCF₂ CF₃

Example 30

Into a 1 liter flask were placed 600 g triethylene glycol butyl ether (2.91 mol), 74 g paraformaldehyde (2.46 mol), 150 ml benzene and 10 g of an acidic ion exchange resin. The mixture was refluxed for 5 hr as water was removed as the water/benzene azeotrope. Filtration of the product and removal of the benzene by distillation gave a 90% yield of the ether product. The product (259 g) was diluted with 400 ml 1,1,2-trichlorotrifluoroethane and was slowly metered into a 10°C reactor containing 5.7 liters of 1,1,2-trichlorotrifluoroethane and 1200 g sodium fluoride powder. A fluorocarbon fluid (660 g, 88.7% yield) was obtained following filtration and removal of the 1,1,2-trichlorotrifluoroethane. Fluorination of the fluid at 220°C with 30% fluorine for 12 hr followed by distillation gave a 60% yield of a fluid, bp 262°C, whose F-nmr spectra was consistent with the following structure:

CF₃CF₂CF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂OCF₂CF₂OCF₂CF₂- OCF₂CF₂OCF₂CF₂CF₂CF₃

Example 31

Into a stirred 1 liter flask equipped with a water separator were charged 350 g tetraethylene glycol butyl ether (1.40 mol), 35 g paraformaldehyde (1.18 mol), 200 ml benzene, and 10 g ion exchange resin. The mixture was refluxed until the water production ceased. Filtration of the product followed by removal of the light fractions by vacuum distillation to 140°C gave 343 g of a light yellow fluid.

A 306 g sample of the fluid was diluted with 450 ml of 1,1,2-trichlorotrifluoroethane and slowly pumped into a -6°C reactor over a 23 hr period. The reactor contained 1450 g of sodium fluoride powder (to react with the hydrogen fluoride formed during the reaction) and 6 liters of 1,1,2-trichlorotrifluoroethane. Filtration of the product followed by distillation gave 736 g of fluid.

Treatment of the latter fluid at 250°C with 30% fluorine gave a clear, odorless fluid which upon distillation gave a 52% yield of a material having a bp of 296.7°C and a F-nmr spectra consistent with the following structure:

CF₃CF₂CF₂CF₂CF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂OCF₂CF₂- OCF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂CF₂CF₃

Example 32

A mixture of 300 g tripropylene glycol methyl ether (6.46 mol), 33.7 g paraformaldehyde (1.12 mol), 150 ml benzene, and 3 g ion exchange resin was refluxed for 6 hr in a 1 liter flask equipped with a water separator and reflux condenser. Filtration of the product followed by vacuum distillation of the light fractions gave 166 g of a product with a boiling point above 150°C at 0.05 mm Hg. Fluorination of 145 g of the distilled material, dissolved in 450 ml 1,1,2-triclιlorotrifluoroethane, in a stirred fluorination reactor containing 6 liters of 1,1,2- trichlorotrifluoroethane and 700 g of sodium fluoride gave 244 g of a fluorocarbon product in a 20 hr reaction at -3°C. Distillation of the product gave 180 g of the perfluorinated fluid:

CF₃O(iso-C₃F₆O),CF, (O-iso-C₃F₆)₃OCF₃ where the hexafluoropropylene oxide units are attached randomly in a head-to-head, head-to-tail and tail-to-tail fashion. The perfluorinated fluid had a bp of 260.0°C and its F-nmr spectra was consistent with the foregoing structure.

Example 33

A mixture of 600 g diethylene glycol and 30 g

potassium hydroxide was heated to 160°C in a 1 liter flask. Acetylene gas was bubbled through the solution as It was rapidly stirred. The raction was stopped after 48 hr and the product was extracted with water several times to remove any unreacted diethylene glycol. The product, a divinyl ether of diethylene glycol, was recovered by distillation (bp 196°C) in about an 80% yield.

A 1 liter flask cooled to -10°C was charged with 250 g triethylene glycol ethyl ether and a catalytic amount of methanesulfonic acid. To this solution was added slowly 100 g diethylene divinyl ether. Following the addition, the flask was slowly warmed to room temperature over a 3 hr period. The product was distilled to 150°C at 0.05 mm Hg to remove any unreacted starting materials.

The product from the above reaction can be

fluorinated at 20°C using the procedures outlined in

Example 28 to give a perfluorinated fluid of the following structure:

CF₃CF₂O(CF₂CF₂O)₃CF(CF₃)O(CF₂CF₂O)₂CF(CF₃)O- (CF₂CF₂O)₃CF₂CF₃ Example 34

A mixture of 400 g triethylene glycol ethyl ether (2.24 mol), 258 g acetaldehyde diethylacetal (1.39 mol), 300 ml benzene, and 10 g acidic ion exchange resin was refluxed in a 1 liter stirred flask equipped with a continuous extractor to remove the by-product ethanol from the refluxing benzene. The solution was refluxed for 6 hr, then filtered and placed in a rotary evaporator to remove the benzene solvent.

The product was fluorinated in a 22 liter stirred tank which contained 5.7 liters of

1,1,2-trichlorotrifluoroethane and 1100 g sodium fluoride powder. The hydrocarbon, 219 g, was diluted to a volume of 700 ml with 1,1,2-trichlorotrifluoroethane. The solution was slowly pumped into the fluorination reactor, which was held at -5°C, over a period of 28 hr. The fluorine flow was set at a level approximately 10% higher than that required to react with all of the organic entering the reactor. Filtration of the crude reactor product followed by distillation yielded 224 g of a clear fluid with an F-nmr spectra consistent with the following structure: CF₃CF₂OCF₂CF₂OC_F2CF₂OCF₂CF₂OCF(CF₃ )OCF₂CF₂O- CF₂CF₂OCF₂CF₂OCF₂CF₃

Example 35

In a run very similar to Example 34, 400 g

dipropylene glycol monomethylether (2.70 mol) was reacted with 159.5 g acetaldehyde diethylacetal ()1.35 mol) in benzene with an acid catalyst. Fluorination of 250 g of the material afforded 480 g of a perfluorinated fluid having the following structure:

CF₃O-iso-C₃F₆O-iso-C₃F₆OCF(CF₃ )iso-C₃F₆O-iso-C₃F₆OCF₃

Example 36 Butoxyethoxyethanol (400 g, 2.47 mol) was reacted with 130 g polymeric chloroacetaldehyde in 150 ml benzene to give a fluid which distilled at 190°C at approximately 1 torr. The product (266 g) was mixed with 500

ml, 1,2-trichlorotrifluoroethane and pumped into a 15-liter fluorination reactor containing 5.7 liters

1,1,2-trichlorotrifluoroethane and 1150 g sodium fluoride powder. Fluorine, diluted with approximately four volumes of nitrogen, was metered into the 0°C reactor at a rate approximately 10% greater than that required to react stoichiometrically with the polyether. The organic feed rate was set to allow complete addition in approximately 23 hr. Filtration of the product and removal of the

1,1,2-trichlorotrifluoroethane via a distillation gave a fluorocarbon product which was further purified by a 12 hr fluorination at 200°C with 40% fluorine. Approximately 520 g of fluid was recovered with approximately 50% being a material with a bp of 245.5°C and a F-nmr spectra consistent with the following structure:

CF₃ CF₂ CF₂ CF₂ OCF₂ CF ₂ OCF ₂ CF₂ OCF ( CF ₂ Cl ) OCF₂ CF ₂ OCF ₂ CF ₂ O- CF₂ CF₂ CF₂ CF₃

Example 37

Chloroacetaldehyde dimethyl acetal (124 g, 1 mol), 1,3-dichloro-2-propanol (258 g, 2 mol) and 5 g ion

exchange resin were mixed in a 1 liter stirred flask. The mixture was heated to allow the methanol formed in the reaction to slowly distill from the flask. Approximately 70 ml of methanol was recovered over a 6 hr period. The remaining solution was vacuum-distilled and the fraction (120 g, 38% yield) boiling between 100°C and 145°C at 2 mm Hg was collected. The fluid as shown by F-nmr and

elemental analyses to have the following structure:

( ClCH₂ )₂CHOCHOCH(CH₂Cl)₂

CH₂Cl The above acetal (210 g), diluted with a small amount of chloroform and 1,1,2-trichlorotrifluoroethane, was metered over a 14 hr period into a 22°C fluorination reactor containing 5.7 liters of 1,1,2-trichlorotri- fluoroethane. The crude product was further treated with 30% fluorine at 200°C for several hours to give 197 g (57% yield) of clear fluid with a bp of 202°C and a F-nmr spectra consistent with the following structure: (CF₂Cl)₂CFOCFOCF(CF₂Cl)₂

CF₂Cl

Example 38

Into a 1 liter stirred flask containing 300 ml benzene were placed 516 g 1,3-dichloro-2-propanol (4 mol), 120 g paraformaldehyde (4 mol) and 10 g ion exchange resin. The mixture was refluxed as the water formed during the reaction was continuously removed. After refluxing for 6 hr, the reaction mixture was filtered and vacuum-distilled to give 354 g of a product, bp 141°C/0.05 mm Hg, with the following structure:

(ClCH₂)₂CHOCH₂OCH(CH₂Cl)₂ The above acetal (354 g) was mixed with 70 g

chloroform and 360 g 1,1,2-trichlorotrifluoroethane and fluorinated over a 24 hr period at 20°C using the

procedure described in the previous example. The reaction product was concentrated and the crude product was further treated with fluorine at 200°C to give 430 g of a clear fluid (69% yield) having a boiling point of 178°C and an F-nmr spectra consistent with the following structure:

[(ClCF₂)₂CFO]₂CF₂

Example 39

A mixture of 300 g 1-propanol (5.0 mol), 231 g epichlorohydrin and 10 g ion exchange resin was refluxed for 22 hr. The reaction mixture was then cooled, filtered and distilled to give 281 g of

1-chloro-3-propoxy-2-propanol (74% yield). Reaction of this product with paraformaldehyde (2.8 mol) gave 202 g of product (69% yield), bp 132°C at 2 mm Hg having the following structure:

CH₃CH₂CH₂OCH₂CHOC_H OCHCH₂OCH₂CH₂CH₃

CH₂Cl CH₂Cl

Fluorination of the above acetal in a 23 hr reaction at 20°C gave 404 g of product (81% yield, bp 207°C), with a F-nmr spectra consistent with the following structure: CF₃CF₂CF₂OCF₂CFOCF₂OCFCF₂OCF₂CF₂CF₃

CF₂CL CF₂Cl

Example 40

A mixture of 600 ml ethoxyethanol, 200 g

epichlorohydrin, and 10 g ion exchange resin was heated to 130°C for 20 hours. The reaction mixture was then cooled, filtered, and distilled to give 250 g of product which was then reacted with 116 g paraformaldehyde as in Example 38 to give 266 g of a product boiling above 150°C at 0.01 mm Hg.

Fluorination of 261 g of the product in a reactor containing 5 liters of 1,1,2-trichlorotrifluoroethane and

1000 g sodium fluoride gave 446 g of perfluorinated fluid, bp 224, of which approximately 70% had a F-nmr spectra consistent with the following structure:

CF₃CF₂OCF₂CF₂OCF₂CFOCF₂OCFCF₂OCF₂CF₂OCF₂CF₃

CF₂Cl CF₂Cl Example 41

A mixture consisting of 100 g 2-chloroethanol (12.4 mol), 573 g epichlorohydrin (6.2 mol) and 20 g of an acidic ion exchange resin were refluxed for 24 hr The mixture was then filtered to remove the ion exchange resin and the excess alcohol and unreacted epichlorohydrin were removed by distillation. The residue was distilled under vacuum and the product, 1-chloro-3-(2-chloroethoxy)-2- propanol (804 g, 75% yield), distilled between 89 and 91°C at 0.05 mm Hg.

Into a 1 liter stirred flask was placed 346 g

1-chloro-3-(2-chloroethoxy)-2-propanol (2 mol), 90 g paraformaldehyde (3 mol), 10 g ion exchange resin and 300 nil benzene. The mixture as refluxed for 4 hr as the water formed during the reaction was removed. The reaction mixture was filtered and distilled to give 267 g of a product (75% yield) with the following structure: C₁CH₂CH₂OCH₂CHOCH OCHCH₂OCH₂CH₂Cl

CH₂Cl CH₂Cl

Fluorination of the product (660 g) in a typical reaction at 20°C gave 1086 g of a product (82% yield, bp 223°C), having a F-nmr spectra consistent with the

following structure:

ClCF₂CF₂OCF₂CFOCF OCFCF₂OCF₂CF₂Cl

CF₂Cl CF₂Cl

Example 42

Into a 1 liter flash was charged 300 g trichloro- pentaerythritol, (1.58 mol), 150 ml of benzene, 10 g ion exchange resin and 60 g paraformaldehyde (2 mol). The mixture was refluxed as water was being removed

continuously.

A stripped portion of the above product, 192 g, was diluted with 1,1,2-trichlorotrifluoroethane to give 210 ml of solution which was pumped into a 22°C reactor

containing 4.3 liters of 1,1,2-trichlorotrifluoroethane. The reaction was complete in approximately 8 hr. The unreacted fluorine was flushed from the reactor with nitrogen gas and the product (307 g, 87.8% yield) was recovered by distillation and its F-nmr spectra was consistent with the following structure:

[(ClCF₂)₃CCF₂O]₂CF₂

Example 43

Butoxyethoxyethanol (400 g, 2.47 mol) was reacted with 130 g polymeric chloroacetaldehyde in 150 ml benzene to give a fluid which distilled at 190°C at approximately 1 torr. The product (266 g) was mixed with 500 ml 1,1,2- trichlorotrifluoroethane and pumped into a 15 liter fluorination reactor containing 5.7 liters 1,1,2-trichlorotrifluoroethane and 1150 g sodium fluoride powder. Fluorine, diluted with approximately four volumes of nitrogen, was metered into the 0°C reactor at a rate approximately 10% greater than that required to react stoichiometrically with the polyether. The organic feed rate was set to allow complete addition in approximately 23 hours. Filtration of the product and removal of the 1,1,2-trichlorotrifluoroethane via a distillation gave a fluorocarbon product which was further purified by a 12 hour fluorination at 200°C with 40% fluorine.

Approximately 520 g of fluid was recovered with

approximately 50% being the target material.

CF₃CF₂CF₂CF₂OCF₂CF₂OCF₂CF₂OCF(CF₂Cl)OCF₂CF₂OCF₂CF₂ OCF₂CF₂CF₂CF₃ b.p. 245.5ºC

¹⁹ F NMR ( δ ppm vs CFCl₃ )

-73.3 :OCF Cl)O:-81.7: CF₂CF₂CF₂O;

-83.3 :CF₃CF₂CF₂CF₂O;-88.0 and .88.7:OC

-96.7: CF₂Cl)O;-126.5:CF₃ CF₂ o.

Example 44

Chloroacetaldehyde dimethyl acetal (124 g, 1 mol) 1,3-dichloro-2-propanol (258 g, 2 mol) and 5 g ion exchange resin were mixed in a 1 liter stirred flask. The mixture was heated to allow the methanol formed in the reaction to slowly distill from the flask. Approximately 70 ml of methanol was recovered over a 6 hour period. The remaining solution was vacuum-distilled and the fraction (120 g, 38% yield) boiling between 100°C and 145°C at 2 mm Hg was collected. The fluid was shown by ¹⁹F NMR and elemental analysis to have the following structure:

( ClCH₂)₂ CHOCHOCH(CH₂Cl)

CH₂ Cl

The above acetal (210 g) diluted with a small amount of chloroform and 1,1,2-trichlorotrifluoroethane was metered over a 14 hour period into a 22°C fluorination reactor containing 5.7 liters of 1,1,2-trichlorotrifluoroethane. The crude product was further treated with 30% fluorine at 200°C for several hours to give 197g (57% yield) of clear fluid: ( CF₂ Cl ) ₂ CFO

CFOCF ( CF₂ Cl ) ₂

CF₂Cl b.p. :202°C

¹⁹ F NMR (δ ppm vs CFCl₃):-64.5 and -65.0(a),

-71.0(d), -86.7(c) and -133.7(b)

[(ClCF₂)₂CFO]₂CF(CF₂Cl)

a b c d

Various modifications and variations will become apparent to those skilled in the art without departing from the spirit and scope of this invention.

Claims

WHAT IS CLAIMED IS:

1. A perfluorinated gem-alkylenedioxy composition which is normally liquid and consists or consists

essentially of one or a mixture of perfluorinated

gem-alkylenedioxy compounds having at least 12 carbon atoms.

2. A perfluorinated compound represented by the formula

wherein Y and Y' are the same or different and are

selected from the group consisting of perfluoroalkyl, perfluoroalkyleneoxyalkyl, and perfluoropoly( alkyleneoxy)- alkyl wherein one or more of the fluorine atoms may be halogen atoms other than fluorine; wherein R₂ and R₂ are the same or different and are selected from the group consisting of -F, -Cl, -CF₂ Cl, -CFCl₂, -CCl₃, and

perfluoroalkyl of 1 to 10 carbon atoms wherein one or more of the fluorine atoms may be halogen atoms other than fluorine and wherein the perfluoroalkyl group may contain one or more ether oxygen atoms.

3. A perfluorinated compound of Claim 2 wherein R₁ and R₂ are fluorine.

4. A perfluorinated compound of Claim 2 wherein R₁ is fluorine and R₂ is perfluoromethyl.

5. A normally liquid, perfluoroacetal composition which consists or consists essentially of one or more saturated perfluoro-1,1-bis-(alkoxy)alkane compounds each of which compounds can have two

perfluoro-1,1-alkylenedioxy moieties provided such moieties are separated from each other by at least two catenary carbon atoms of a perfluoroalkylene moiety.

6 The composition of Claim 1 consisting or consisting essentially of one of said compounds.

7. The composition of Claim 1 consisting or

consi sting essentially of a mixture of said compounds.

8. The composition of Claim 1 wherein each said compound is represented by the formula

wherein and are independently selected from the

group consisting of C₁ to C8 linear or branched

perfluoroalkyl, C₁ to C₈ linear or branched

chloroperfluoroalkyl, and unsubstituted or lower

alkyl-substituted perfluorocycloalkyl or

chloroperfluorocycloalkyl wherein the number of ring carbon atoms is 4 to 6; and are independently

selected from the group consisting of C₂ to C₄ linear or branched perfluoroalkylene and C₂ to C₄ linear or branched chloroperfluoroalkylene; each

is independently a fluorine atom or perfluoroalkyl with 1 to 4 carbon atoms; x and w are each independently an integer of 0 to 4; y is an integer of 1 to 6; z is an integer of 0 to 1; and where the total number of carbon atoms in said compound is 6 to 30.

9. The composition of Claim 8, wherein each R^ is independently F or CF₃ and the total number of carbon atoms in said compound is 12 to 17.

10. The composition of Claim 5 wherein said compound is represented by the formula C_n F_{2 n} +₁ ( OC_mF_{2 m} )_a -OCF[(CF₂)pF]O-(C_m ,F_{2 m} O)_bC_n,F_2n,₊₁ wherein each n and n' is independently an integer of 1 to 6, each m and m' is independently an integer of 2 to 4, a and b are each independently an integer of 0 to 4, and p is 0 or 1, each said compound having 13 or 14 total carbon atoms, said composition having a viscosity at -70°C of less than about 300 centistokes.

11. The composition of Claim 8 wherein said compound is perfluoro-bis(2-butoxyethoxy)methane.

12. The composition of Claim 8 wherein said compound is perfluoro-3,6,9,11-tetraoxaheptadecane.

13. The composition of Claim 8 wherein said compound is perfluoro-5,7,10,13-tetraoxaheptadecane.

14. The composition of Claim 8 wherein said compound is perfluoro-2,14-dimethyl-4,7,9,12-tetraoxapentadecane .

15. The composition of Claim 8 wherein said compound is perfluoro-3,6,9,11,14,17-hexaoxanonadecane.

16. The composition of Claim 8 wherein said compound is perfluoro-2,5,7,10,13,16,18,21-octaoxadocosane.

17. The composition of Claim 8 wherein said compound is perfluoro-3,6,8,11,14,16,19-heptaoxaheneicosane.

18. The composition of Claim 8 wherein said compound is perfluoro-3,5,8,11,14-pentaoxaoctadecane.

19. The composition of Claim 7 consisting or

consisting essentially of a mixture of

perfluoro-bis (2-butoxyethoxy)methane, perfluoro

3 , 6 , 9 , 11 , 14 , 17-hexaoxanonadecane, and, optionally,

perfluoro-3,6,9,11,14-pentaoxaoctadecane.

20. The composition of Claim 1 wherein said compound is represented by the formula CF₃CF₂CF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂- CF₂CF₃

21. The composition of Claim 1 wherein said compound is represented by the formula

CF₃CF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂OCF₂CF₂OCF₂CF₂OCF₂- CF₂OCF₂CF₃

22. The composition of Claim 1 wherein said compound is represented by the formula

CF₃CF₂CF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂OCF₂CF₂OCF₂CF₂- OCF₂CF₂OCF₂CF₂CF₂CF₃

23. The composition of Claim 1 wherein said compound is represented by the formula CF₃CF₂CF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂OCF₂CF₂- OCF₂CF₂OCF₂CF₂OCF₂CF₂OCF₂CF₂CF₂CF₃

24. The composition of Claim 1 wherein said compound is represented by the formula

CF₃O(iso-C₃F₆O)₃CF₂ (O-iso-C₃F₆ )₃OCF₃

25. The composition of Claim 1 wherein said compound is represented by the formula

CF₃CF₂O(CF₂CF₂O)₃CF(CF₃ )O(CF₂CF₂O)₂CF(CF₃ )O-

(CF₂CF₂O)₃CF₂CF₃

26. The composition of Claim 1 wherein said compound is represented by the formula

CF₃CF₂OCF₂CF2OCF₂CF₂OCF₂CF₂OCF(CF₃ )OCF₂CF₂- CF₂CF₂OCF₂CF₂OCF₂CF₃

27. The composition of Claim 1 wherein said compound is represented by the formula

CF₃3P-iso-C₃F₆O-iso-C₃F₆O-OCF(CF₃ )O-iso-C₃F₆O-iso- C₃F₆OCF₃

28. The composition of Claim 1 wherein said compound is represented by the formula

CF₃CF₂CF₂CF₂OCF₂CF₂OCF₂CF₂OCF(CF₂Cl)OCF₂CF₂OCF₂CF₂O- CF₂CF₂CF₂CF₃

29. The composition of Claim 1 wherein said compound is represented by the formula l (ClCH₂)₂CHOCHOCH(CH₂Cl)₂

CH₂Cl

30. The composition of Claim 1 wherein said compound is represented by the formula

( ClCH₂ ) ₂ CHOCH₂ OCH ( CH₂ Cl ) ₂

31. The composition of Claim 1 wherein said compound is represented by the formula

CF₃CF₂CF₂OCF₂CFOCF OCFCF₂OCF₂CF₂CF₃

CF₂Cl CF₂Cl

32. The composition of Claim 1 wherein said compound is represented by the formula

CF₃CF₂OCF₂CF₂OCF₂CFOCF OCFCF₂OCF₂CF₂OCF₂CF₃

CF₂C1 CF₂Cl

33. The composition of Claim 1 wherein said compound is represented by the formula ClCF₂CF₂OCF₂CFOCF₂OCFCF₂OCF₂CF₂Cl

CF₂Cl CF₂Cl

34. A process for making the composition of Claim 1, which comprises contacting with fluorine the corresponding perfluorinateable, fluorine-free or partially fluorinated precursor to perfluorinate the same.

35. The process of Claim 34 wherein said contacting is carried out in the presence of a hydrogen fluoride scavenger.

36. A method of transferring heat from an article to a cooling liquid comprising directly contacting the article with a cooling liquid comprising the composition of Claim 5.

37. A method of inducing thermal shock of an article comprising:

a) heating a first bath of a heating liquid to a temperature above ambient temperature; b) cooling a second bath of a cooling liquid to a temperature below ambient temperature; and c) sequentially:

i) immersing the article in an initial bath which is one of said first and second baths and allowing said article to come to the temperature of said initial bath before removing said article from said initial bath, and

ii) then immersing said article in the other of said first and second baths and allowing said article to come to the temperature of said other bath before removing said article from said other bath;

wherein said liquids are inert, thermally stable,

perfluoroinated liquids, at least one of which is the composition of Claim 5.

38. A method in accordance with Claim 23, wherein said heating and cooling liquids are identical and are the composition of Claim 6.

39. A perfluorinated polyether having an average formula:

Y-O-CF₂-O-Y' wherein Y and Y' are the same or different and are

selected from the group consisting of perfluoroalkyl, perfluoroalkoxyalkyl, and perfluoroalkyleneoxyalkyl; and wherein the polyether comprises fewer than 8 or 12 or more carbon atoms provided that Y and Y' cannot both be -CF₃ or

-C₂F₅ .

40. The perfluorinated polyether of Claim 39, wherein the polyether comprises from 12 to 20 carbon atoms.

41. A perhalogenated polyether having an average formula:

wherein Y and Y' are the same or different and are

selected from the group consisting of perfluoroalkyl, perfluoroalkoxyalkyl, and perfluoroalkyleneoxyalkyl;

wherein R₁ and R₂ are the same or different and are selected from the group consisting of -Cl, CF₂Cl, -CFCl₂, -CCl₃, perfluoroalkyl having 1 to 20 carbon atoms and perfluoroalkyleneoxyalkyl; and wherein the polyether comprises 12 or more carbon atoms.

42. The polyether of Claim 41, wherein the polyether comprises 12 to 25 carbon atoms.

43. A perhalogenated polyether having an average formula:

wherein Y and Y' are the same or different and are

selected from the group consisting of perfluoroalkyl, perfluoroalkoxyalkyl, and perfluoroalkyleneoxyalkyl;

wherein R is selected from the group consisting of -Cl, CF₂Cl, -CFCl₂, -CCl₃, perfluoroalkyl having 1 to 20 carbon atoms and perfluoroalkyleneoxyalkyl; and wherein the polyether comprises 12 or more carbon atoms.

44. The polyether of Claim 43, wherein the polyether comprises from 12 to 25 carbon atoms.

45. A perhalogenated polyether having an average formula:

wherein Y and Y' are the same or different and are selected from the group consisting of perfluoroalkyl, perfluoroalkoxyalkyl, and perfluoroalkyleneoxyalkyl;

wherein R₁ and R₂ are the same or different and are selected from the group consisting of -F, -Cl, CF₂Cl,

-CFCl₂, -CCl₃, perfluoroalkyl having 1 to 20 carbon atoms and perfluoroalkyleneoxyalkyl; and wherein the polyether contains at least one halogen atom other than fluorine.