CA1298927C - Fluoropolymer dispersions - Google Patents
Fluoropolymer dispersionsInfo
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- CA1298927C CA1298927C CA000510632A CA510632A CA1298927C CA 1298927 C CA1298927 C CA 1298927C CA 000510632 A CA000510632 A CA 000510632A CA 510632 A CA510632 A CA 510632A CA 1298927 C CA1298927 C CA 1298927C
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Abstract
ABSTRACT
The invention is a dispersion for the manufacture of films and articles for use in electrolytic cells, fuel cells and gas or liquid permeation units, wherein the dispersion comprises a fluorinated polymer containing sites convertible to ion exchange groups dispersed in a dispersant having:
a boiling point less than 110°C;
a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and wherein the densities of the dispersant and the fluorinated polymer are selected such that they are balanced with each other.
Preferred is a dispersant having the general formula: XCF2-CYZX' wherein: X is selected from F, Cl, Br, and I;
X1 is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
34,247-F -35-R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms. Particularly preferred as a dispersant is 1,2-dibromotetrafluoroethane.
34,247 -36-
The invention is a dispersion for the manufacture of films and articles for use in electrolytic cells, fuel cells and gas or liquid permeation units, wherein the dispersion comprises a fluorinated polymer containing sites convertible to ion exchange groups dispersed in a dispersant having:
a boiling point less than 110°C;
a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and wherein the densities of the dispersant and the fluorinated polymer are selected such that they are balanced with each other.
Preferred is a dispersant having the general formula: XCF2-CYZX' wherein: X is selected from F, Cl, Br, and I;
X1 is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
34,247-F -35-R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms. Particularly preferred as a dispersant is 1,2-dibromotetrafluoroethane.
34,247 -36-
Description
~29892'7 NOVEL FLUOROPOLYMER DISPERSIONS
Ion exchange active fluoropolymer films or sheets have been widely used in industry, particularly as ion exchange membranes in chlor-alkali cells. Such membranes are made from fluorinated polymers having ion exchange active groups attached to pendant groups on the polymeric backbone.
Such polymers are usually thermoplastic and may be fabricated into films or sheets while in their molten form using mechanical extrusion equipment.
However, such equipment is operated in the temperature region near the crystalline melting point of the polymer, which is commonly near the decomposition temperature of some of the polymers. Thus, decomposition may be a problem when some polymers are formed into films by conventional methods. Likewise, it is difficult to make such polymers into films thinner tha~ about 10 microns using such techniques. In addition, it is difficult to make films of consistent thickness. It would therefore be highly desirable to be able to make thin films having a consistent thickness.
34,247-F -1-, Forming membrane structures and support st uctures into multiple layers is the subject of several patents and applications including U.S. Patents 3,925,135; 3,909,378; 3,770,567; and 4,341,605. However, these methods use complicated procedures and equipment including such things as vacuum manifolds, rolls and release media.
Prior art methods for fabricating films from perfluorinated polymers have been ~imited by the solubil-ity of the polymers and the temperature-dependent viscosity-shear rate behavior of the polymers. To overcome these characteristics of perfluorinated carboxy-lic ester polymers, workers have tried to swell the polymers using various types of swelling agents and to reduce the fabrication temperatures of the polymers to practical ranges by extraction. Extractions methods have been taught in, for example, U.S. Patent 4,360,601.
There, low molecular weight oligomers were removed from carboxylic ester polymers. Polymer "fluff" was extracted in a Soxhlet device at atmospheric pressure for 24 hours (see Examples 1 and 3 of U.S. Patent 4,360,601).
Such treatments has been found to make some fluorinated carboxylic ester copolymers more processible and operate more efficiently in a chlor-alkali cell when in a hydrolyzed form. Such extractions modify the fabricated polymer article, for example, by forming grease of the.
polymer as shown in-Example 3 of U.S. Patent 4,360,601.
In addition, such extractions seem to lower processing temperatures of carboxylic ester polymers after isolation. Isolation means separation from the polymerizatian latex by conventional methods of deacti-vating the surfactant such as freezing, heating, shearing, salting out or pH adjustment.
34,247-F -2-British Patent No. 1,286,859 teaches that highly polar organic "solvents" dissolve small amounts of fluorinated vinyl ether~tetrafluoroethylene copolymer in its thermoplastic form. Thermoplastic form means the polymer is in a form which can be molded or proces-sed above some transition temperature (such as the glass transition temperature or the melting point) without altering its chemical structure or composition.
The patent teaches the use of the "solvents" including butanol, ethanol, N,N-dimethylacetamide, and N,N-dimethyl-aniline.
Similar approaches have been used to swell membranes in their ionic forms. Ionic forms of membranes are membranes which have been converted from their thermoplastic form (-SO2F or -COOCH3) to their ionic forms (-SO3M or -COOM where M is H , K , Na , or NH4 or other metal ion.
Prior art workers have used highly polar solvents or mixtures of solvents on substantially perfluorinated polymers and less polar solvents on fluorinated polymers containing hydrocarbon components as co-monomers, ter-monomers or crosslinking agents.
However, each of the prior art methods for swelling, dispersing or extracting the polymers has 25 certain shortcomings which are known to those practic-ing the art. Polar solvents have the potential for water absorption or reactivity with the functional groups during subsequent fabrication Qperations, thus making poor coatings, films, etc. High boiling solvents are difficult to remove and frequently exhibit toxic or flammability properties. Functional form (ionic forms) of the polymers can react with solvents. (C~e Analyt-ical Chem., 1982, Volume 54, pages 1639-1641).
34,247-F -3-The more polar of the solvents such as methanol, butanol esters, and ketones as disclosed in U.S. Patent 3,740,369; British Patent 1,286,859; and Chemical Abstracts 7906856 have high vapor pressures at ambient conditions, which is desirable for solvent removal;
however, they tend to absorb water. Their water content is undesirable because it causes problems in producing continuous coatings and films of hydrophobic polymers.
In addition, polar solvents frequently leave residues which are incompatible with the polymers. Also, they frequently leave residues which are reactive during subsequent chemical or thermal operations if they are not subsequently removed.
Another approach taken by the prior art workers to form films from fluoropolymers include the use of high molecular weight "solvents" which have been produced by halogenating vinyl ether monomers. (See British Patent No. 2,066,824).
The swelling of the functional (ionic) forms of the fluoropolymers by polar or hydrophilic agents has been known for some time. In addition, the solvent solubility parameters were compared to the swelling effect of 1200 equivalent weight Nafion ion exchange membrane (available from E. I. DuPont Company) by Yeo 2S at Brookhaven Laboratory (see Polymer, 1980, Volume 21, page 432).
The swelling was found to be proportional to two different ranges of the solubility parameter and a calculation was developed for optimizing ratios of solvent mixtures. Ionic forms of functional fluoro-polymers may be treated in such a manner, however, the subsequent physical forming or manipu'ation of the 34,247-F -4-~298927 polymers into usable configurations by any thermal operation is limited when the polymers are in the functional forms. In addition, non-ionic forms of polymers treated in this manner are also limited in the thermoplastic processing range by the stability of the functional group bonds.
Other solvation methods have used temperatures near the crystalline melting points of the polymers being solvated, thus requiring either high boiling point "solvents" or high pressure vessels to maintain the system in a solid/liquid state. See Analytical Chem., 1982, Volume 54, pages 1639-1641.
Burrell states the theory of Bagley [J. Paint Tech., Volume 41, page 495 (1969)] predicts a noncrystalline polymer will dissolve in a solvent of similar solubility parameter without chemical similarity, association, or any intermolecular force.
However, he fails to mention anything dbut ~he solubility of polymers demonstrating crystallinity.
More particularly, the invention resides in a dispersion composition for dispersing perfluorinated polymer particles in a dispersant wherein said perfluorinated polymer contains sites convertible to ion exchange groups and wherein said dispersant has a boiling point less than 110C; 0 a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and wherein the densities of the dispersant and the fluorinated polymer are selected such that they are balanced with each other.
34,247-F -5-i~
,~
~2989%~
-5a-The invention also resides in a method for dispersing perfluorinated polymer particles containing sites convertible to ion exchange groups comprising the steps of:
contacting the polymer with a dispersant for a time and at a temperature sufficient to disperse at least a portion of the polymer in the solvent, wherein the dispersant has:
a boiling point less than 110C; and a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and selecting the densities of the dispersant and the fluorinated polymer such that they are balanced with each other.
34,247-F -5a-XCF2-CYZX' wherein:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluorcalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms.
The most preferred dispersant is 1,2-dibromo-tetrafluoroethane.
Dispersion, as used herein, means a composi-tion containing a dispersant and a perfluorinated polymer containing sites convertible to ion exchange groups, wherein the polymer is dispersed in the disper-sant, but is only partially dissolved in the dispersant.
The present invention can be used to make ion exchange media, films and articles for use in electro-lytic cells, fuel cells and gas or liquid permeation units.
Non-ionic forms of perfluorinated polymers described in the following U.S. Patents are suitable for use in the present invention: 3,282,875; 3,909,378;
4,025,405; 4,065,366; 4,116,888; 4,123,336; 4,126,588;
4,151,052; 4,176,215; 4,178,218; 4,192,725; 4,209,635;
4,212,713; 4,251,333; 4,270,996; 4,329,435; 4,330,654;
4,337,137; 4,337,211; 4,340,680; 4,357,218; 4,358,412;
34,247-F -6-~29892~
4,358,545; 4,417,969; 4,462,877i 4,470,889; and 4,478,695 European Patent Publication No. 0,027,009. Such polymers usually have equivalent weights of from 500 to 2000.
Particularly preferred are copolymers of monomer I with monomer II (as defined below). Option-ally, a third type of monomer may be copolymerized with I and II.
The first type of monomer is represented by the general formula:
CF2=CZZ' (I) where:
Z and Z' are independently selected from -H, -Cl, -F, and CF3.
The second monomer consists of one or more monomers selected from compounds represented by the general formula:
Ion exchange active fluoropolymer films or sheets have been widely used in industry, particularly as ion exchange membranes in chlor-alkali cells. Such membranes are made from fluorinated polymers having ion exchange active groups attached to pendant groups on the polymeric backbone.
Such polymers are usually thermoplastic and may be fabricated into films or sheets while in their molten form using mechanical extrusion equipment.
However, such equipment is operated in the temperature region near the crystalline melting point of the polymer, which is commonly near the decomposition temperature of some of the polymers. Thus, decomposition may be a problem when some polymers are formed into films by conventional methods. Likewise, it is difficult to make such polymers into films thinner tha~ about 10 microns using such techniques. In addition, it is difficult to make films of consistent thickness. It would therefore be highly desirable to be able to make thin films having a consistent thickness.
34,247-F -1-, Forming membrane structures and support st uctures into multiple layers is the subject of several patents and applications including U.S. Patents 3,925,135; 3,909,378; 3,770,567; and 4,341,605. However, these methods use complicated procedures and equipment including such things as vacuum manifolds, rolls and release media.
Prior art methods for fabricating films from perfluorinated polymers have been ~imited by the solubil-ity of the polymers and the temperature-dependent viscosity-shear rate behavior of the polymers. To overcome these characteristics of perfluorinated carboxy-lic ester polymers, workers have tried to swell the polymers using various types of swelling agents and to reduce the fabrication temperatures of the polymers to practical ranges by extraction. Extractions methods have been taught in, for example, U.S. Patent 4,360,601.
There, low molecular weight oligomers were removed from carboxylic ester polymers. Polymer "fluff" was extracted in a Soxhlet device at atmospheric pressure for 24 hours (see Examples 1 and 3 of U.S. Patent 4,360,601).
Such treatments has been found to make some fluorinated carboxylic ester copolymers more processible and operate more efficiently in a chlor-alkali cell when in a hydrolyzed form. Such extractions modify the fabricated polymer article, for example, by forming grease of the.
polymer as shown in-Example 3 of U.S. Patent 4,360,601.
In addition, such extractions seem to lower processing temperatures of carboxylic ester polymers after isolation. Isolation means separation from the polymerizatian latex by conventional methods of deacti-vating the surfactant such as freezing, heating, shearing, salting out or pH adjustment.
34,247-F -2-British Patent No. 1,286,859 teaches that highly polar organic "solvents" dissolve small amounts of fluorinated vinyl ether~tetrafluoroethylene copolymer in its thermoplastic form. Thermoplastic form means the polymer is in a form which can be molded or proces-sed above some transition temperature (such as the glass transition temperature or the melting point) without altering its chemical structure or composition.
The patent teaches the use of the "solvents" including butanol, ethanol, N,N-dimethylacetamide, and N,N-dimethyl-aniline.
Similar approaches have been used to swell membranes in their ionic forms. Ionic forms of membranes are membranes which have been converted from their thermoplastic form (-SO2F or -COOCH3) to their ionic forms (-SO3M or -COOM where M is H , K , Na , or NH4 or other metal ion.
Prior art workers have used highly polar solvents or mixtures of solvents on substantially perfluorinated polymers and less polar solvents on fluorinated polymers containing hydrocarbon components as co-monomers, ter-monomers or crosslinking agents.
However, each of the prior art methods for swelling, dispersing or extracting the polymers has 25 certain shortcomings which are known to those practic-ing the art. Polar solvents have the potential for water absorption or reactivity with the functional groups during subsequent fabrication Qperations, thus making poor coatings, films, etc. High boiling solvents are difficult to remove and frequently exhibit toxic or flammability properties. Functional form (ionic forms) of the polymers can react with solvents. (C~e Analyt-ical Chem., 1982, Volume 54, pages 1639-1641).
34,247-F -3-The more polar of the solvents such as methanol, butanol esters, and ketones as disclosed in U.S. Patent 3,740,369; British Patent 1,286,859; and Chemical Abstracts 7906856 have high vapor pressures at ambient conditions, which is desirable for solvent removal;
however, they tend to absorb water. Their water content is undesirable because it causes problems in producing continuous coatings and films of hydrophobic polymers.
In addition, polar solvents frequently leave residues which are incompatible with the polymers. Also, they frequently leave residues which are reactive during subsequent chemical or thermal operations if they are not subsequently removed.
Another approach taken by the prior art workers to form films from fluoropolymers include the use of high molecular weight "solvents" which have been produced by halogenating vinyl ether monomers. (See British Patent No. 2,066,824).
The swelling of the functional (ionic) forms of the fluoropolymers by polar or hydrophilic agents has been known for some time. In addition, the solvent solubility parameters were compared to the swelling effect of 1200 equivalent weight Nafion ion exchange membrane (available from E. I. DuPont Company) by Yeo 2S at Brookhaven Laboratory (see Polymer, 1980, Volume 21, page 432).
The swelling was found to be proportional to two different ranges of the solubility parameter and a calculation was developed for optimizing ratios of solvent mixtures. Ionic forms of functional fluoro-polymers may be treated in such a manner, however, the subsequent physical forming or manipu'ation of the 34,247-F -4-~298927 polymers into usable configurations by any thermal operation is limited when the polymers are in the functional forms. In addition, non-ionic forms of polymers treated in this manner are also limited in the thermoplastic processing range by the stability of the functional group bonds.
Other solvation methods have used temperatures near the crystalline melting points of the polymers being solvated, thus requiring either high boiling point "solvents" or high pressure vessels to maintain the system in a solid/liquid state. See Analytical Chem., 1982, Volume 54, pages 1639-1641.
Burrell states the theory of Bagley [J. Paint Tech., Volume 41, page 495 (1969)] predicts a noncrystalline polymer will dissolve in a solvent of similar solubility parameter without chemical similarity, association, or any intermolecular force.
However, he fails to mention anything dbut ~he solubility of polymers demonstrating crystallinity.
More particularly, the invention resides in a dispersion composition for dispersing perfluorinated polymer particles in a dispersant wherein said perfluorinated polymer contains sites convertible to ion exchange groups and wherein said dispersant has a boiling point less than 110C; 0 a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and wherein the densities of the dispersant and the fluorinated polymer are selected such that they are balanced with each other.
34,247-F -5-i~
,~
~2989%~
-5a-The invention also resides in a method for dispersing perfluorinated polymer particles containing sites convertible to ion exchange groups comprising the steps of:
contacting the polymer with a dispersant for a time and at a temperature sufficient to disperse at least a portion of the polymer in the solvent, wherein the dispersant has:
a boiling point less than 110C; and a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and selecting the densities of the dispersant and the fluorinated polymer such that they are balanced with each other.
34,247-F -5a-XCF2-CYZX' wherein:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluorcalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms.
The most preferred dispersant is 1,2-dibromo-tetrafluoroethane.
Dispersion, as used herein, means a composi-tion containing a dispersant and a perfluorinated polymer containing sites convertible to ion exchange groups, wherein the polymer is dispersed in the disper-sant, but is only partially dissolved in the dispersant.
The present invention can be used to make ion exchange media, films and articles for use in electro-lytic cells, fuel cells and gas or liquid permeation units.
Non-ionic forms of perfluorinated polymers described in the following U.S. Patents are suitable for use in the present invention: 3,282,875; 3,909,378;
4,025,405; 4,065,366; 4,116,888; 4,123,336; 4,126,588;
4,151,052; 4,176,215; 4,178,218; 4,192,725; 4,209,635;
4,212,713; 4,251,333; 4,270,996; 4,329,435; 4,330,654;
4,337,137; 4,337,211; 4,340,680; 4,357,218; 4,358,412;
34,247-F -6-~29892~
4,358,545; 4,417,969; 4,462,877i 4,470,889; and 4,478,695 European Patent Publication No. 0,027,009. Such polymers usually have equivalent weights of from 500 to 2000.
Particularly preferred are copolymers of monomer I with monomer II (as defined below). Option-ally, a third type of monomer may be copolymerized with I and II.
The first type of monomer is represented by the general formula:
CF2=CZZ' (I) where:
Z and Z' are independently selected from -H, -Cl, -F, and CF3.
The second monomer consists of one or more monomers selected from compounds represented by the general formula:
2 a ( Rf)b (CFRf,)c-O-[CF[CF2X)-CF -O] CF=CF (II) where:
Y is selected from -SO2Z, -CN, -COZ, and C(R3f)(R4f)0H;
- Z is selected from I, Br, Cl, F, OR and NR1R2;
R is selected from a branched or linear alkyl radical having from 1 to 10 carbon atoms or an aryl radical;
R3f and R4f are independently selected f-rom perfluoroalkyl radicals having from l to 10 carbon atoms;
34,247-F -7-Rl and R2 are independently selected from H, a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
a is 0-6;
b is 0-6;
c is 0 or 1;
provided a+b+c is not equal to 0;
. X is selected from Cl, Br, F and mixtures thereof when n>1;
n is 0 to 6; and Rf and Rf, are independently selected from F, Cl, perfluoroalkyl radicals having from 1 to 10 carbon atoms and fluorochloroalkyl radicals having from 1 to 10 carbon atoms.
Particularly preferred is when Y is -SO2F or -COOCH3; n is 0 or 1; Rf and Rf, are F; X is Cl or F;
and a+b+c is 2 or 3.
The third.and optional monomer suitable is ; one or more monomers selected from the compounds repre-sented by the general formula:
Y ~(C~F2)a~-(cFRf)b~-(cFR~f)c~-o-[cF(cF2x~ )-CF2-Oln,-CF=CF2 . . where: . .
~ Y' is selected from F, Cl and Br;
a' and b' are independently 0-3;
c' is 0 or 1;
provided a'+b'+c' is not equal to 0 n' is 0-6;
Rf and R'f are independently selected from Br, Cl, F, perfluoroalkyl radicals having from 1 to 10 34,247-F -8-carbon atoms, and chloroperfluoroalkyl radicals having from 1 to 10 carbon atomsi and X' is selected from F, Cl, Br, and mixtures thereof when n'>1.
Conversion of Y to ion exchange groups is well known in the art and consists of reaction with an . alkaLine solution.
The monomer FSO2CF2CF2OCF=CF, has a density of about 1.65 grams per cubic centimeter and polytetra-fluoroethylene has a density of about 2.2 grams percubic centimeter. A copolymer of this monomer with tetrafluoroethylene would, thus, have a density between the two values.
It has been discovered that certain perhalo-genated dispersant have a surprising effect of dispers-ing the polymers, especially when the polymers are in a finely divided state.
Dispersants suitable for use in the present invention should have the following characteristics:
a boiling point less than about 110C;
a density of from 1.55 to 2.97 grams per cubic centimeter; and a solubility parameter of from greater than 7.1 to 8.2 hildebrands.
It is important that the dispersant has a boiling point of from 30C to 110C. The ease of removal of the dispersant and the degree of dispersant removal is important in the producing of various films, 34,247-F -9-coatings and the like, without residual dispersanti hence a reasonable boiling point at atmospheric pressure allows convenient handling at ambient temperature conditions yet effective dispersant removal by atmos-pheric drying or mild warming.
It is important that the dispersant has adensity of from 1.55 to 2.97 grams. per cub~c centimeter.
The polymers of the present invention have densities on the order of from 1.55 to 2.2 grams per cub~c centimeter.
Primarily, the polymers have densities in the range of from 1.6 to 2.2 grams per cubic centimeter. Dispersants of the present invention will therefore swell, dissolve and disperse small particles of this polymer, aided by the suspending effects of the similarity in densities.
In the prior art, there was no recognition and thus no attempt was made to balance density. The prior art was only interested in forming solutions, and solutions do not separate.
Solubility parameters are related to the cohesive energy density of compounds. Calculating solubility parameters is discussed in U.S. Patent 4,348,310.
It is important that the dispersant has-a ~ solubility parameter of from greater than 7.1 to 8.2 hildebrands. The similarity in cohesive energy densities between the dispersant and the pol~mer determine the likelihood of dissolving and swelling the polymer in the dispersant.
.
34,247-F -10-It is preferable that the dispersant has a vapor pressure of up to about 760 millimeters of mercury at the specified temperature limits at the point of dispersant removal. The dispersant should be conveni-ently removed without the necessity of higher tempera-tures or reduced pressures involving extended heating such as would be necessary in cases similar to U.S.
Patent 3,692,569 or the examples in British Patent 2,066,824 in which low pressures (300 mm) had to be employed as well as non-solvents to compensate for the higher boiling points and low vapor pressures of the complex solvents.
It has been found that dispersants represented by the following general formula are particularly preferred provided they also meet the characteristics discussed above (boiling point, density, and solubility parameter):
XCF2-CYZ-X' whereln:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms.
The most preferred dispersants are 1,2-dibromo-~ tetrafluoroethane (commonly known as Freon 114 B 2) 5..~.
BrCF2 -CF2Br ~ 7-M~
34,247-F -11-1~9892~
.
and 1,2,3-trichlorotrifluoroethane (commonly known as Freon 113):
ClF2C-CCl~F
- Of these two dispersants, 1,2-dibromotetrafluoroethane is the most preferred dispersant. It has a boiling - point of about 47.3~, a density of about 2.156 grams per cubic centimeter, and a solubility parameter of about 7.2 hildebrands.
1,2-dibromotetrafluoroethane is thought to work particularly well because, though not directly . polar, it is highly polarizable. Thus, when 1,2-dibromo-tetrafluoroethane is associated with a polar molecule, its electron density shifts and causes it to behave as a polar molecule. Yet, when 1,2-dibromotetrafluoro-ethane is in contact with a non-polar molecule, it behaves as a non-polar dispersant. Thus, 1,2-dibromo-tetrafluoroethane tends to dissolve the non-polar backbone of polytetrafluoroethylene and also the polar pendant groups. The solubility parameter of 1,2-di-bromotetrafluoroethane is calculated to be from 7.13 to7.28 hildebrands.
It is surprising that an off-the-shelf, readïly-available compound such as 1,2-dibromotetra-fluoroethane would act as a solvent for the fluoro-polymers described above. It is even more surprisingthat 1,2-dibromotetrafluoroethane happens to have a boiling point, a density and a solubility parameter such that it is particularly suitable for use as a solvent/dispersant in the present invention.
34,247-F -12-lX-91~-927 In practicing the present invention, the polymer may be in any physical form. However, it is preferably in the form of fine particles to speed dissolution and dispersion of the particles into the dispersant. Preferably, the particle size of the polymers is from 0.01 microns to 840 microns. More preferably, the particle size is less than about 250 microns..
To dissolve and disperse the polymer particles into the dispersant, the polymer particles are placed in contact with the dispersant of choice and intimately mixed. The polymer and the dispersant may be mixed by any of several means including, but not limited to, shaking, stirring, milling or ultra sonic means.
Thorough, intimate contact between the polymer and the dispersant are needed for optimum dissolution and dispersion.
The polymers of the present invention are dissolved and dispersed into the dispersants at concen-trations ranging from 0.1 to 50 weight percent ofpolymer to dispersant. At concentrations below 0.1 weight percent, there is insufficient polymer dissolved and dispersed to be effective as a medium for coating of articles or forming films within a reasonable number of repetitive operations. Conversely, at concentrations above 50 weight percent there-is sufficient polymer present as a separate phase such that viable, coherent films and coatings of uniform structure cannot be formed without particulate agglomerates, etc.
Preferably, the concentration of the polymer in the dispersant is from 1 to 20 weight percent. Most preferably, the concentration of the polymer in the dispersant is from 5 to 15 weight percent.
34,247-F -13-~2989Z7 The dispersion of the polymer into the disper-sant can be conducted at room temperature conditions.
However, the optimum dispersion effects are best achieved -at temperatures from 10C to 50C. At temperatures above 50C the measures for dissolving and dispersing the polymer have to include pressure confinement for the preferred dispersants or method of condensing the dispersants. Conversely, at temperatures below 10C
many of the polymers of the present invention are below their glass transition temperatures thus causing their dispersions to be difficult to form at reasonable conditions of mixing, stirring, or grinding.
The dispersion of the polymers of the present invention into the dispersant are best conducted at atmospheric pressure. However, dispersion effects can be achieved at pressures from 760 to 15,000 mm Hg or greater. At pressures below 760 mm Hg, the operation of the apparatus presents no advantage in dissolving and dispersing polymers, rather hindering permeation into the polymers and thus preventing forming of the dispersions.
Conversely, pressures above 760 mm Hg aid in dissolving and dispersing polymers very little compared to the difficulty and complexity of the operation.
Experiments have shown that at about 20 atmospheres the amount of polymer dissolved and dispersed in the.disper-sant is not appreciably greater.
After the polymer dispersions of the present invention have been formed, they may be fixed to other polymer films or substrates by sintering or compression to fix the polymer from the dispersion to the substrate.
34,247-F -14-, The following methods are suitable for fixing the dispersion of the present invention to a substrate.
Dipping the substrate into the dispersion, followed by air drying and sintering at the desired temperature with sufficient repetition to build the desired thick-ness. Spraving the dispersion onto the substrate is used to advantage for covering large or irregular shapes. Pouring the dispersion onto ~the substrate is sometimes used. Painting the dispersion with brush or roller has been successfully employed. In addition, coatings may be easily applied with metering bars, knives, or rods. Usually, the coatings or films are built up to the thickness desired by repetitive drying and sintering.
The type of substrate upon which the disper-sion of the present invention may be applied can include such things as glass, polytetrafluoroethylene tapes, or sheets, expanded mesh metal electrodes, scrim materials made of, for example, fibers selected from carbon or graphite, PTFE and metal, metal foil or sheets, prefer-ably aluminum foil or other polymer films or objects.
The substrate upon which the dispersion is to be deposited is cleaned or treated in such a way as to assure uniform contact with the dispersion. The sub-str,ate can be cleansed by washing with a degreaser-or similar solvent followed by drying to remove any dust or oils from objects to be used as substrates. Metals should usually be acid etched, then washed with a solvent to promote adhesion, if desired, unless the metal is new in which case degreasing is sufficient.
34,247-F -15-After being cleaned, the substrates may be pre-_onditioned by heating or vacuum drying prior to contact with the dispersions and the coating operation.
Temperatures and pressures,in the following ranges are preferably used: 20 mm Hg at 110C is sufficient in all cases; however, mild heat is usually adequate when applied at a temperature of 50C at atmospheric pressure.
After preparation, the substrates are coated with the dispersion by any of several means including, but not limited to, dipping, spraying, brushing, pouring.
Then the dispersion may be evened out using scraping knives, rods, or other suitable means. The dispersion can be applied in a single step or in several steps depending on the concentration of the polymer in the dispersion and the desired thickness of the coating or film.
Following the application of the dispersion, the dispersant is removed by any of several methods including, but not limited to, evaporation or extraction.
Extraction is the use of some agent which selectively dissolves or mixes with the dispersant but not the polymer.
These removal means should be emp~oyed until a uniform deposition of polymer is obtained and a continuous film is formed.
The dispersant removal is typically carried out by maintaining the coated substrate at temperatures ranging from 10C to 110C, with the preferred heating range being from 20C to 100C. The heating temperature selected depends upon the boiling point of the dispeLsant.
34,247-F -16--17-.
Heating temperatures are customarily in the range of from 20C to 50C for 1,2-dibromotetrafluoro-ethane.
The pressures employed for the removal of the dispersant from the coated substrate can range from 20 mm Hg to 760 mm Hg depending on the nature of the . dispersant, although pressures are typically in the range of from 300 mm Hg to 760 mm Hg for 1,2-dibromotetra-fluoroethane.
10The forming of the coatir,g or film can be carried out as part of the polymer deposition and dispersant removal process or as a separate step by adjusting the thermal and pressure conditions associated with the separation of the polymer from the dispersant.
If the dispersion is laid down in successive steps, a continuous film or coating free from pinholes can be formed without any subsequent heating above ambient temperature by control of the rate of evaporation.
This can be done by vapor/liquid equilibrium in a container or an enclosure; therefore, the dispersant removal step can be merely a drying step or a controlled process for forming a coating or film. If the dispersant is removed as by flash evaporation, a film will not form without a separate heating step.
After the dispersant has been removed, the residual polymer, as a separate step, is preferably subjected to a heat source of from 250C to 380C for times ranging from 10 seconds to 120 minutes, depending upon the thermoplastic properties of the polymers. The polymers having melt viscosities on the order of 5 x 105 poise at a temperature of 300C at a shear rate of 1 sec. 1, as measured by a typical capillary rheometer, 34,247-F -17-would require the longer times and higher temperatures within the limits of the chemical group stability.
Polymers with viscosities on the order of 1 poise at ambient temperatures would require no further treatment.
The most preferred treatment temperatures are from 270C to 350C and a time of from 0.2 to 45 minutes .
for the most preferred polymers for use in the present invention. Such polymers form thin continuous films under the conditions described above.
Films of varying thicknesses can be easily produced by the methods and means described above.
Such films are suitable as membranes when in their ionic forms, for use in electrochemical cells. They are particularly useful for the electrolysis of sodium chloride brine solutions to produce chlorine gas and sodium hydroxide solutions. Membranes prepared according to the present invention have surprisingly good current efficiencies when used in chlor-alkali cells.
EXAMPLES
ExamPle 1 A copolymer of CF2=CF2 and CF2=CFOCF2CF2SO2F
having equivalent weight of about 1144 was prepared.
The polymer was prepared according to the following ^ procedure. 784 grams of CF2=CFOCF2CF2SO2F was added to 4700 grams of deoxygenated water contain-ing 25 grams NH4O2CC7Fl 5, 18.9 grams of Na2HPO4 7H2O, 15.6 grams of NaH2PO4 H2O and 4 grams of (NH4)2S2O8 - under a positive pressure of 250 psig (1722 kPa~ of tetrafluoroethylene at 60C for 58 minutes. The 34,247-F -18-~298927 reactor was vented under heat and vacuum to remove residual monomers. The reactor contents was frozen, thawed, and vigorously washed to remove residual salts and soap. After vacuum drying, a dispersion was prepared by placing 56 grams of polymer prepared above . in a laboratory-size single tier 290 revolutions per minute roller Norton Jar Mill with 168 grams of i,2-di-bromotetrafluoroethane. Th.e mixture was mixed in the ball mill overnight at ambient temperature and at atmospheric pressure.
To the resulting soft paste about 300 addi-tional grams of 1,2-dibromotetrafluoroethane was added and the mill was rolled an additional 3 hours. The resulting dispersion was found to contain 12.5 weight percent polymer. The mixture was coated onto a sheet of aluminum foil having a thickness of 38 microns by dipping the foil into the dispersion. The coated aluminum foil was allowed to air dry. Thus, the dispers-ant evaporated from the dispersion at ambient tempera-ture.
The coated aluminum foil was then heated to a temperature of 300C in a muffle furnace for 1 minute to sinter the polymer into a more uniform film form.
The resulting film was found to be a continuous film and had a thickness of 0.5 mils (12.7 microns).
The dipping and heating process was repeated5 times until a 2.5 mil (63.5 microns) thick polymer film was built up.
34,247-F -19-~2989Z7 Two pieces of aluminum foil which had been coated in the above described manner were pressed together, coated side to coated side, under a pressure of 800 psi (5512 kPa) at a temperature of 595F (313C) for 4 minutes. The resulting film, with aluminum foil on both sides, was hydrolyzed for 16 hours in a 25 weight percent sodium hydroxide aqueous solution at a temperature of 90C. This treatment dissolved the aluminum foil and left only the two layer film. The two layer film was tested in a chlor-alkali membrane cell. The cell was operated at a temperature of 89C
at a current density of 2 amps/in2 (Q.31 amps/cm2) of electrode surface areas with a 3 mm (3000 micron) gap between the anode and cathode. A cathode having an electrocatalyst on its surface was used. The cell voltage was 3.11 volts at 12.9 weight percent sodium hydroxide concentration being produced in the cathode chamber. The caustic current efficiency was found to be 92.2 percent. The caustic produced in the catholyte chamber was analyzed and found to contain 1030 parts per million sodium chloride. The total energy consumed for the production of one metric ton of sodium hydroxide was calculated to be 2259 kilowatt hours.
Examp~e 2 A copolymer of CF2=CF2 and CF2=CFOCF2CF2CO3CH3 was prepared having an equivalent weight of abou~ 847.
- 50 Grams of CF2=CFOCF2CF2CO3CH3 was added to 300 grams of deoxygenated water containing 3.0 grams of NH4O2CC7Fl 5, 1.5 grams of Na2HPO4 7H2O, 1.0 gram NaH2PO4 H2O, and 0.20 gram (NH4)2S2O8 under a positive pressure of tetrafluoroethylene of 250 psig (1722 kPa) pressure at 50C for 180 minutes in a glass reactor. The reactor was vented and the reactor contents was acidified with - 34,247-F -20-6 normal HCl to coagulate the polymer. The coagulam was filtered out, vigorously washed and vacuum dried.
35 Grams of the polymer was ground and mixed overnight in 315 grams of 1,2-dibromotetrafluoroethane 5. in the laboratory jar mill described in Example 1.
. The dispersant was analyzed and found to contain about 10 weight percent solids. The dispersion was used to coat a sheet of aluminum foil having a thickness of 38 microns by dipping the foil, allowing the coating to air dry and sintering the coating at a temperature of 250C (482F) for 1 minute in the muffle furnace described in Example 1.
This coating procedure was repeated until a series of coated foils had been made in which the coating thickness varied. From 2 to 5 dips on the various films resulted in film thicknesses of the sintered coating of from 0.7 to 1.8 mils (17.8 to 48.6 microns).
The coated foils were then pressed onto an 850 equivalent weight fluorosulfonyl copolymer films which was 4 mils (101.6 microns) thick. The 850 equi-valent weight polymer was prepared as the previous fluorosulfonyl copolymer example except for using a pressure of 192 psi~ (1323 kPa) and a run time of 88 2~ minutes. The dried polymer was extruded at a tempera-ture of 500F (260C) to 550F (288C) using a Haake Rheomiex 254 1.9 cm vented 25:1 length/diameter 316 stainless steel screw extruder and a 15 cm die. With a 20 mil (508 microns) die gap, the film was drawn down to 4-5 mils (101 to 127 microns) thickness and quenched 34,247-F -21-12989;~
.
on an unheated 316 stainless steel roll. The cast film samples were cleaned by degreasing with acetone and air dried. The coated side of the foil was placed against the cast film and the two were placed between two sheets of polytetrafluoroethylene coated glass cloth.
These were then placed between two photographic plates.
The entire sandwich was compressed at a temperature of . 250C in a hydraulic hot press using about 20 tons force for five minutes.
.
The combinations were hydrolyzed in a 25 weight percent sodium hydroxide aqueous solution at a temperature of 90C for 16 hours. This treatment dissolved the aluminum foil from each combination. The resulting two layer films were tested in a chlor-alkali test cell. The cell has an exposed electrode surface of 56 cm2 with a titanium anode compartment and a plexiglass cathode compartment. The anode was a ruthenium oxide coated expanded metal electrode. A cathode having an electrocatalyst as its surface was used.
Brine containing 20 weight ~ercent sodium chloride was introduced into the anode compartment and water was added to the cathode compartment as the direct current was passed through the electrodes at 2 amps/in2 (0.3 amps/cm2) of electrode surface area. The membrane was disposed between the electrodes and bolted between the two cell halves with gas exits and overflows from each half.
The data on these films is set forth in Table I following:
34,247-F -22-TABLE I
Sample No. 1 2 # of Dippings 2 5 Thickness of Coatings mils (microns) 0.8 (20) 1.8 .(4~) Thickness of Pressed - Loading mils-(microns) 0.2 (5.1) - 0.4-0.6 (10.2-15.2) Caustic Current Efficiency (%) 95.6 96.7 Voltage 3.22 3.33 % NaOH 34.7 35-4 Energy (kwh/metric ton NaOH) 2256 2307 The caustic current efficiency is determined as the moles of caustic per Faradays of current times 100. That is, the number of moles of caustic which were produced in a test period, divided by the time in seconds times the current over the test period, all divided by 96,520 coulombs per equivalent (Faraday).
The resultant decimal fraction represents the proportion of electrons that produced NaOH. This fraction times 100 gives the caustic current efficiency.
The above data was taken after 13 days of operation and was essentially unchanged after 90 days operation.
ExamPle 3 A copolymer of CF2=CF2 and CF2=CFOCF2CF2CO3CH3 was prepared having an equivalent weight of 755. 50 Grams 34,247-F -23-of CF2=CFOCF2CF2CO3CH3 was added to 300 grams of deoxygen-ated water containing 3.0 grams of NH4O2CC7F1 5, 1 5 grams of Na2HPO4-7H2O, 1.0 gram NaH2PO4 H2O, and 0.10 gram (NH~)2S2O8 under a positive pressure of tetrafluoro-ethylene of 235 psig (1619 kPa) pressure at a temperature of 50C fQr 5 hours in a glass reactor. The reactor was vented and the reactor contents was acidified with 6 normal HCl to coagulate the latex. ~he coagulam was filtered and washed vigorously to remove inorganics and soap. The polymer was vacuum dried for 16 hours at a temperature of 85C.
15 Grams of the polymer prepared above was ground in a lab mortar and pestle with 135 grams of 1,2-dibromotetrafluoroethane to produce a viscous dispersion. The dispersion was used to coat a sheet of aluminum foil which was 38.1 microns thick. The coated foil was pressed in a heated hydraulic press at a pressure of 2000 psi (13,780 kPa) and at a temperature of 540F (282C) for 4 minutes and 20 seconds between glass reinforced polytetrafluoroethylene backing sheets.
The backing sheets were removed from the first polymer film and the coated side of the foil placed against a 5 mil (127 micron) thick film of the second ion exchange polymer film. The pressing opera-tion was repeated using 670 psig (4616 kPa) to attach the first film to the second film. The resulting-two-layer film was hydrolyzed in a 25 weight percent sodium hydroxide aqueous solution for 16 hours at a temperature of 90C. The aluminum foil dissolved in this process. The two-layer film was mounted in a test cell with the 755 equivalent weight polymer facing the cathode compartment.
34,247-F -24-~ ;~98927 After 190 days of operation in a chlor-alkali test cell as described in Example 2 to produce chlorine gas and NaOH from the electrolysis of a NaCl brine, produced a 33 weight % NaOH in an aqueous solution at a 95.6% caustic current efficiency and 3.38 volts.
Example 4 .. A copolymer of CF~=CF2 and CF2=CFOCF2CF2SO2F
having an equivalent weight of 1160 was prepared accord-ing to the following procedure. 50 Grams of CF2=CFOCF2CF2SO2F was added-to 300 milliliters of deoxygenated water containing 3 grams NH4CO2C7F1s, 1.5 grams of Na2HPO4-7H2O, 1 gram of NaH2PO4 H2O and 0.1 grams of (NH4)2S2Og under a positive pressure of 245 psig (1688 kPa) of tetrafluoroethylene at a temperature of 60C for 75 minutes in a glass reactor. The reactor was vented under heat and acidified to coagulate the latex. The coagulated polymer was washed repeatedly to remove inorganics and soap. The polymer was vacuum dried for 16 hours at a temperature of 110C.
30 Grams of the fluorosulfonyl copolymer was ground with 270 grams of 1,2-dibromotetrafluoroethane in a lab mortar and pestle until a viscous dispersion was produced.
.This dispersion was used to coat a sheet of aluminum foil having a thickness of 38.1 microns. The coating was allowed to air dry. The coated foil was then pressed between glass reinforced polytetrafluoro-ethylene backing sheets which were held between photo-graphic plates in a heated press. The pressure was 2000 psig (13,780 kPa) and the temperature was 595F
(313C). The time was 4 minutes and 20 seconds.
34,247-F -25-Thereafter, the backing sheet was removed from the press and a thin polymeric film emained on the foil.
A second copolymer was prepared. It was a copolymer of CF2=CF2 and CF2=CFOCF2CF2SO2F having an equivalent weight of 974. The polymer was prepared according to the following procedure. 784 Grams of CF2=CFOCF2CF~SO2F was added to 4700 grams of deoxygen-ated water containing 25 grams NH4COzC7Fl5~ 18.9 grams of Na2HPO4-7H2O, 15.6 grams of NaH2PO4 H2O and 4 grams of (NH4 )2S208 under a positive pressure of 220 psig (1516 kPa) of tetrafluoroethylene at a temperature of 60C for 30 minutes. The reactor was vented under heat and vacuum to remove residual monomers. The reactor contents was frozen, thawed, and vigorously washed to remove residual salts and soap. The film was vacuum dried for 16 hours at a temperature of 85C.
The second film was extruded on a commercially available Killion laboratory extruder with a regular Xaloy barrel and screw. The screw was a standard type commonly used to extrude polyethylene. Blown film was made with a 3.2 cm die with a 20 mil (508 micron) gap heated to a temperature of 550C using no cooling ring.
The extruder was operated at a temperature of from 450 to 550F (232 to 288C) and 20 to 40 revolutions per minute. The hauloff (a mechanical device to roll up the film) operated a~ a rate of 30 to 60 cm/min.
Various thicknesses of blown film were produced as desired by varying speeds and the blowing of the bubble.
A 5 mil (127 microns) extruded polymeric film 30 of 84K3023 fluorosulfonyl copolymer was placed against the coated side of the foil and pressed as above except 34,247-F -26-, 1~98927 only 670 psig (4613 kPa) pressure was used. This two layer film was hydrolyzed in 25 weight percent sodium hydroxide aqueous solution for 16 hours at a tempera-ture of 90C. The foil was etched away in this process.
The resulting two layer film was placed in a test cell (the same cell described in Example 3) with the 83P019 polymer facing the cathode compartment. After 2 days of operating the following results were obtained.
Cell voltage was found to be 3.02 volts and the caustic current efficiency was 91.5 percent at a caustic concentration of 12.56 weight percent. The sodium chloride concentration in the caustic was analyzed and found to be 940 parts per million. The cell energy was calculated to be about 2211 kilowatt hours per metric ton of caustic.
34,247-F -27-
Y is selected from -SO2Z, -CN, -COZ, and C(R3f)(R4f)0H;
- Z is selected from I, Br, Cl, F, OR and NR1R2;
R is selected from a branched or linear alkyl radical having from 1 to 10 carbon atoms or an aryl radical;
R3f and R4f are independently selected f-rom perfluoroalkyl radicals having from l to 10 carbon atoms;
34,247-F -7-Rl and R2 are independently selected from H, a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
a is 0-6;
b is 0-6;
c is 0 or 1;
provided a+b+c is not equal to 0;
. X is selected from Cl, Br, F and mixtures thereof when n>1;
n is 0 to 6; and Rf and Rf, are independently selected from F, Cl, perfluoroalkyl radicals having from 1 to 10 carbon atoms and fluorochloroalkyl radicals having from 1 to 10 carbon atoms.
Particularly preferred is when Y is -SO2F or -COOCH3; n is 0 or 1; Rf and Rf, are F; X is Cl or F;
and a+b+c is 2 or 3.
The third.and optional monomer suitable is ; one or more monomers selected from the compounds repre-sented by the general formula:
Y ~(C~F2)a~-(cFRf)b~-(cFR~f)c~-o-[cF(cF2x~ )-CF2-Oln,-CF=CF2 . . where: . .
~ Y' is selected from F, Cl and Br;
a' and b' are independently 0-3;
c' is 0 or 1;
provided a'+b'+c' is not equal to 0 n' is 0-6;
Rf and R'f are independently selected from Br, Cl, F, perfluoroalkyl radicals having from 1 to 10 34,247-F -8-carbon atoms, and chloroperfluoroalkyl radicals having from 1 to 10 carbon atomsi and X' is selected from F, Cl, Br, and mixtures thereof when n'>1.
Conversion of Y to ion exchange groups is well known in the art and consists of reaction with an . alkaLine solution.
The monomer FSO2CF2CF2OCF=CF, has a density of about 1.65 grams per cubic centimeter and polytetra-fluoroethylene has a density of about 2.2 grams percubic centimeter. A copolymer of this monomer with tetrafluoroethylene would, thus, have a density between the two values.
It has been discovered that certain perhalo-genated dispersant have a surprising effect of dispers-ing the polymers, especially when the polymers are in a finely divided state.
Dispersants suitable for use in the present invention should have the following characteristics:
a boiling point less than about 110C;
a density of from 1.55 to 2.97 grams per cubic centimeter; and a solubility parameter of from greater than 7.1 to 8.2 hildebrands.
It is important that the dispersant has a boiling point of from 30C to 110C. The ease of removal of the dispersant and the degree of dispersant removal is important in the producing of various films, 34,247-F -9-coatings and the like, without residual dispersanti hence a reasonable boiling point at atmospheric pressure allows convenient handling at ambient temperature conditions yet effective dispersant removal by atmos-pheric drying or mild warming.
It is important that the dispersant has adensity of from 1.55 to 2.97 grams. per cub~c centimeter.
The polymers of the present invention have densities on the order of from 1.55 to 2.2 grams per cub~c centimeter.
Primarily, the polymers have densities in the range of from 1.6 to 2.2 grams per cubic centimeter. Dispersants of the present invention will therefore swell, dissolve and disperse small particles of this polymer, aided by the suspending effects of the similarity in densities.
In the prior art, there was no recognition and thus no attempt was made to balance density. The prior art was only interested in forming solutions, and solutions do not separate.
Solubility parameters are related to the cohesive energy density of compounds. Calculating solubility parameters is discussed in U.S. Patent 4,348,310.
It is important that the dispersant has-a ~ solubility parameter of from greater than 7.1 to 8.2 hildebrands. The similarity in cohesive energy densities between the dispersant and the pol~mer determine the likelihood of dissolving and swelling the polymer in the dispersant.
.
34,247-F -10-It is preferable that the dispersant has a vapor pressure of up to about 760 millimeters of mercury at the specified temperature limits at the point of dispersant removal. The dispersant should be conveni-ently removed without the necessity of higher tempera-tures or reduced pressures involving extended heating such as would be necessary in cases similar to U.S.
Patent 3,692,569 or the examples in British Patent 2,066,824 in which low pressures (300 mm) had to be employed as well as non-solvents to compensate for the higher boiling points and low vapor pressures of the complex solvents.
It has been found that dispersants represented by the following general formula are particularly preferred provided they also meet the characteristics discussed above (boiling point, density, and solubility parameter):
XCF2-CYZ-X' whereln:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms.
The most preferred dispersants are 1,2-dibromo-~ tetrafluoroethane (commonly known as Freon 114 B 2) 5..~.
BrCF2 -CF2Br ~ 7-M~
34,247-F -11-1~9892~
.
and 1,2,3-trichlorotrifluoroethane (commonly known as Freon 113):
ClF2C-CCl~F
- Of these two dispersants, 1,2-dibromotetrafluoroethane is the most preferred dispersant. It has a boiling - point of about 47.3~, a density of about 2.156 grams per cubic centimeter, and a solubility parameter of about 7.2 hildebrands.
1,2-dibromotetrafluoroethane is thought to work particularly well because, though not directly . polar, it is highly polarizable. Thus, when 1,2-dibromo-tetrafluoroethane is associated with a polar molecule, its electron density shifts and causes it to behave as a polar molecule. Yet, when 1,2-dibromotetrafluoro-ethane is in contact with a non-polar molecule, it behaves as a non-polar dispersant. Thus, 1,2-dibromo-tetrafluoroethane tends to dissolve the non-polar backbone of polytetrafluoroethylene and also the polar pendant groups. The solubility parameter of 1,2-di-bromotetrafluoroethane is calculated to be from 7.13 to7.28 hildebrands.
It is surprising that an off-the-shelf, readïly-available compound such as 1,2-dibromotetra-fluoroethane would act as a solvent for the fluoro-polymers described above. It is even more surprisingthat 1,2-dibromotetrafluoroethane happens to have a boiling point, a density and a solubility parameter such that it is particularly suitable for use as a solvent/dispersant in the present invention.
34,247-F -12-lX-91~-927 In practicing the present invention, the polymer may be in any physical form. However, it is preferably in the form of fine particles to speed dissolution and dispersion of the particles into the dispersant. Preferably, the particle size of the polymers is from 0.01 microns to 840 microns. More preferably, the particle size is less than about 250 microns..
To dissolve and disperse the polymer particles into the dispersant, the polymer particles are placed in contact with the dispersant of choice and intimately mixed. The polymer and the dispersant may be mixed by any of several means including, but not limited to, shaking, stirring, milling or ultra sonic means.
Thorough, intimate contact between the polymer and the dispersant are needed for optimum dissolution and dispersion.
The polymers of the present invention are dissolved and dispersed into the dispersants at concen-trations ranging from 0.1 to 50 weight percent ofpolymer to dispersant. At concentrations below 0.1 weight percent, there is insufficient polymer dissolved and dispersed to be effective as a medium for coating of articles or forming films within a reasonable number of repetitive operations. Conversely, at concentrations above 50 weight percent there-is sufficient polymer present as a separate phase such that viable, coherent films and coatings of uniform structure cannot be formed without particulate agglomerates, etc.
Preferably, the concentration of the polymer in the dispersant is from 1 to 20 weight percent. Most preferably, the concentration of the polymer in the dispersant is from 5 to 15 weight percent.
34,247-F -13-~2989Z7 The dispersion of the polymer into the disper-sant can be conducted at room temperature conditions.
However, the optimum dispersion effects are best achieved -at temperatures from 10C to 50C. At temperatures above 50C the measures for dissolving and dispersing the polymer have to include pressure confinement for the preferred dispersants or method of condensing the dispersants. Conversely, at temperatures below 10C
many of the polymers of the present invention are below their glass transition temperatures thus causing their dispersions to be difficult to form at reasonable conditions of mixing, stirring, or grinding.
The dispersion of the polymers of the present invention into the dispersant are best conducted at atmospheric pressure. However, dispersion effects can be achieved at pressures from 760 to 15,000 mm Hg or greater. At pressures below 760 mm Hg, the operation of the apparatus presents no advantage in dissolving and dispersing polymers, rather hindering permeation into the polymers and thus preventing forming of the dispersions.
Conversely, pressures above 760 mm Hg aid in dissolving and dispersing polymers very little compared to the difficulty and complexity of the operation.
Experiments have shown that at about 20 atmospheres the amount of polymer dissolved and dispersed in the.disper-sant is not appreciably greater.
After the polymer dispersions of the present invention have been formed, they may be fixed to other polymer films or substrates by sintering or compression to fix the polymer from the dispersion to the substrate.
34,247-F -14-, The following methods are suitable for fixing the dispersion of the present invention to a substrate.
Dipping the substrate into the dispersion, followed by air drying and sintering at the desired temperature with sufficient repetition to build the desired thick-ness. Spraving the dispersion onto the substrate is used to advantage for covering large or irregular shapes. Pouring the dispersion onto ~the substrate is sometimes used. Painting the dispersion with brush or roller has been successfully employed. In addition, coatings may be easily applied with metering bars, knives, or rods. Usually, the coatings or films are built up to the thickness desired by repetitive drying and sintering.
The type of substrate upon which the disper-sion of the present invention may be applied can include such things as glass, polytetrafluoroethylene tapes, or sheets, expanded mesh metal electrodes, scrim materials made of, for example, fibers selected from carbon or graphite, PTFE and metal, metal foil or sheets, prefer-ably aluminum foil or other polymer films or objects.
The substrate upon which the dispersion is to be deposited is cleaned or treated in such a way as to assure uniform contact with the dispersion. The sub-str,ate can be cleansed by washing with a degreaser-or similar solvent followed by drying to remove any dust or oils from objects to be used as substrates. Metals should usually be acid etched, then washed with a solvent to promote adhesion, if desired, unless the metal is new in which case degreasing is sufficient.
34,247-F -15-After being cleaned, the substrates may be pre-_onditioned by heating or vacuum drying prior to contact with the dispersions and the coating operation.
Temperatures and pressures,in the following ranges are preferably used: 20 mm Hg at 110C is sufficient in all cases; however, mild heat is usually adequate when applied at a temperature of 50C at atmospheric pressure.
After preparation, the substrates are coated with the dispersion by any of several means including, but not limited to, dipping, spraying, brushing, pouring.
Then the dispersion may be evened out using scraping knives, rods, or other suitable means. The dispersion can be applied in a single step or in several steps depending on the concentration of the polymer in the dispersion and the desired thickness of the coating or film.
Following the application of the dispersion, the dispersant is removed by any of several methods including, but not limited to, evaporation or extraction.
Extraction is the use of some agent which selectively dissolves or mixes with the dispersant but not the polymer.
These removal means should be emp~oyed until a uniform deposition of polymer is obtained and a continuous film is formed.
The dispersant removal is typically carried out by maintaining the coated substrate at temperatures ranging from 10C to 110C, with the preferred heating range being from 20C to 100C. The heating temperature selected depends upon the boiling point of the dispeLsant.
34,247-F -16--17-.
Heating temperatures are customarily in the range of from 20C to 50C for 1,2-dibromotetrafluoro-ethane.
The pressures employed for the removal of the dispersant from the coated substrate can range from 20 mm Hg to 760 mm Hg depending on the nature of the . dispersant, although pressures are typically in the range of from 300 mm Hg to 760 mm Hg for 1,2-dibromotetra-fluoroethane.
10The forming of the coatir,g or film can be carried out as part of the polymer deposition and dispersant removal process or as a separate step by adjusting the thermal and pressure conditions associated with the separation of the polymer from the dispersant.
If the dispersion is laid down in successive steps, a continuous film or coating free from pinholes can be formed without any subsequent heating above ambient temperature by control of the rate of evaporation.
This can be done by vapor/liquid equilibrium in a container or an enclosure; therefore, the dispersant removal step can be merely a drying step or a controlled process for forming a coating or film. If the dispersant is removed as by flash evaporation, a film will not form without a separate heating step.
After the dispersant has been removed, the residual polymer, as a separate step, is preferably subjected to a heat source of from 250C to 380C for times ranging from 10 seconds to 120 minutes, depending upon the thermoplastic properties of the polymers. The polymers having melt viscosities on the order of 5 x 105 poise at a temperature of 300C at a shear rate of 1 sec. 1, as measured by a typical capillary rheometer, 34,247-F -17-would require the longer times and higher temperatures within the limits of the chemical group stability.
Polymers with viscosities on the order of 1 poise at ambient temperatures would require no further treatment.
The most preferred treatment temperatures are from 270C to 350C and a time of from 0.2 to 45 minutes .
for the most preferred polymers for use in the present invention. Such polymers form thin continuous films under the conditions described above.
Films of varying thicknesses can be easily produced by the methods and means described above.
Such films are suitable as membranes when in their ionic forms, for use in electrochemical cells. They are particularly useful for the electrolysis of sodium chloride brine solutions to produce chlorine gas and sodium hydroxide solutions. Membranes prepared according to the present invention have surprisingly good current efficiencies when used in chlor-alkali cells.
EXAMPLES
ExamPle 1 A copolymer of CF2=CF2 and CF2=CFOCF2CF2SO2F
having equivalent weight of about 1144 was prepared.
The polymer was prepared according to the following ^ procedure. 784 grams of CF2=CFOCF2CF2SO2F was added to 4700 grams of deoxygenated water contain-ing 25 grams NH4O2CC7Fl 5, 18.9 grams of Na2HPO4 7H2O, 15.6 grams of NaH2PO4 H2O and 4 grams of (NH4)2S2O8 - under a positive pressure of 250 psig (1722 kPa~ of tetrafluoroethylene at 60C for 58 minutes. The 34,247-F -18-~298927 reactor was vented under heat and vacuum to remove residual monomers. The reactor contents was frozen, thawed, and vigorously washed to remove residual salts and soap. After vacuum drying, a dispersion was prepared by placing 56 grams of polymer prepared above . in a laboratory-size single tier 290 revolutions per minute roller Norton Jar Mill with 168 grams of i,2-di-bromotetrafluoroethane. Th.e mixture was mixed in the ball mill overnight at ambient temperature and at atmospheric pressure.
To the resulting soft paste about 300 addi-tional grams of 1,2-dibromotetrafluoroethane was added and the mill was rolled an additional 3 hours. The resulting dispersion was found to contain 12.5 weight percent polymer. The mixture was coated onto a sheet of aluminum foil having a thickness of 38 microns by dipping the foil into the dispersion. The coated aluminum foil was allowed to air dry. Thus, the dispers-ant evaporated from the dispersion at ambient tempera-ture.
The coated aluminum foil was then heated to a temperature of 300C in a muffle furnace for 1 minute to sinter the polymer into a more uniform film form.
The resulting film was found to be a continuous film and had a thickness of 0.5 mils (12.7 microns).
The dipping and heating process was repeated5 times until a 2.5 mil (63.5 microns) thick polymer film was built up.
34,247-F -19-~2989Z7 Two pieces of aluminum foil which had been coated in the above described manner were pressed together, coated side to coated side, under a pressure of 800 psi (5512 kPa) at a temperature of 595F (313C) for 4 minutes. The resulting film, with aluminum foil on both sides, was hydrolyzed for 16 hours in a 25 weight percent sodium hydroxide aqueous solution at a temperature of 90C. This treatment dissolved the aluminum foil and left only the two layer film. The two layer film was tested in a chlor-alkali membrane cell. The cell was operated at a temperature of 89C
at a current density of 2 amps/in2 (Q.31 amps/cm2) of electrode surface areas with a 3 mm (3000 micron) gap between the anode and cathode. A cathode having an electrocatalyst on its surface was used. The cell voltage was 3.11 volts at 12.9 weight percent sodium hydroxide concentration being produced in the cathode chamber. The caustic current efficiency was found to be 92.2 percent. The caustic produced in the catholyte chamber was analyzed and found to contain 1030 parts per million sodium chloride. The total energy consumed for the production of one metric ton of sodium hydroxide was calculated to be 2259 kilowatt hours.
Examp~e 2 A copolymer of CF2=CF2 and CF2=CFOCF2CF2CO3CH3 was prepared having an equivalent weight of abou~ 847.
- 50 Grams of CF2=CFOCF2CF2CO3CH3 was added to 300 grams of deoxygenated water containing 3.0 grams of NH4O2CC7Fl 5, 1.5 grams of Na2HPO4 7H2O, 1.0 gram NaH2PO4 H2O, and 0.20 gram (NH4)2S2O8 under a positive pressure of tetrafluoroethylene of 250 psig (1722 kPa) pressure at 50C for 180 minutes in a glass reactor. The reactor was vented and the reactor contents was acidified with - 34,247-F -20-6 normal HCl to coagulate the polymer. The coagulam was filtered out, vigorously washed and vacuum dried.
35 Grams of the polymer was ground and mixed overnight in 315 grams of 1,2-dibromotetrafluoroethane 5. in the laboratory jar mill described in Example 1.
. The dispersant was analyzed and found to contain about 10 weight percent solids. The dispersion was used to coat a sheet of aluminum foil having a thickness of 38 microns by dipping the foil, allowing the coating to air dry and sintering the coating at a temperature of 250C (482F) for 1 minute in the muffle furnace described in Example 1.
This coating procedure was repeated until a series of coated foils had been made in which the coating thickness varied. From 2 to 5 dips on the various films resulted in film thicknesses of the sintered coating of from 0.7 to 1.8 mils (17.8 to 48.6 microns).
The coated foils were then pressed onto an 850 equivalent weight fluorosulfonyl copolymer films which was 4 mils (101.6 microns) thick. The 850 equi-valent weight polymer was prepared as the previous fluorosulfonyl copolymer example except for using a pressure of 192 psi~ (1323 kPa) and a run time of 88 2~ minutes. The dried polymer was extruded at a tempera-ture of 500F (260C) to 550F (288C) using a Haake Rheomiex 254 1.9 cm vented 25:1 length/diameter 316 stainless steel screw extruder and a 15 cm die. With a 20 mil (508 microns) die gap, the film was drawn down to 4-5 mils (101 to 127 microns) thickness and quenched 34,247-F -21-12989;~
.
on an unheated 316 stainless steel roll. The cast film samples were cleaned by degreasing with acetone and air dried. The coated side of the foil was placed against the cast film and the two were placed between two sheets of polytetrafluoroethylene coated glass cloth.
These were then placed between two photographic plates.
The entire sandwich was compressed at a temperature of . 250C in a hydraulic hot press using about 20 tons force for five minutes.
.
The combinations were hydrolyzed in a 25 weight percent sodium hydroxide aqueous solution at a temperature of 90C for 16 hours. This treatment dissolved the aluminum foil from each combination. The resulting two layer films were tested in a chlor-alkali test cell. The cell has an exposed electrode surface of 56 cm2 with a titanium anode compartment and a plexiglass cathode compartment. The anode was a ruthenium oxide coated expanded metal electrode. A cathode having an electrocatalyst as its surface was used.
Brine containing 20 weight ~ercent sodium chloride was introduced into the anode compartment and water was added to the cathode compartment as the direct current was passed through the electrodes at 2 amps/in2 (0.3 amps/cm2) of electrode surface area. The membrane was disposed between the electrodes and bolted between the two cell halves with gas exits and overflows from each half.
The data on these films is set forth in Table I following:
34,247-F -22-TABLE I
Sample No. 1 2 # of Dippings 2 5 Thickness of Coatings mils (microns) 0.8 (20) 1.8 .(4~) Thickness of Pressed - Loading mils-(microns) 0.2 (5.1) - 0.4-0.6 (10.2-15.2) Caustic Current Efficiency (%) 95.6 96.7 Voltage 3.22 3.33 % NaOH 34.7 35-4 Energy (kwh/metric ton NaOH) 2256 2307 The caustic current efficiency is determined as the moles of caustic per Faradays of current times 100. That is, the number of moles of caustic which were produced in a test period, divided by the time in seconds times the current over the test period, all divided by 96,520 coulombs per equivalent (Faraday).
The resultant decimal fraction represents the proportion of electrons that produced NaOH. This fraction times 100 gives the caustic current efficiency.
The above data was taken after 13 days of operation and was essentially unchanged after 90 days operation.
ExamPle 3 A copolymer of CF2=CF2 and CF2=CFOCF2CF2CO3CH3 was prepared having an equivalent weight of 755. 50 Grams 34,247-F -23-of CF2=CFOCF2CF2CO3CH3 was added to 300 grams of deoxygen-ated water containing 3.0 grams of NH4O2CC7F1 5, 1 5 grams of Na2HPO4-7H2O, 1.0 gram NaH2PO4 H2O, and 0.10 gram (NH~)2S2O8 under a positive pressure of tetrafluoro-ethylene of 235 psig (1619 kPa) pressure at a temperature of 50C fQr 5 hours in a glass reactor. The reactor was vented and the reactor contents was acidified with 6 normal HCl to coagulate the latex. ~he coagulam was filtered and washed vigorously to remove inorganics and soap. The polymer was vacuum dried for 16 hours at a temperature of 85C.
15 Grams of the polymer prepared above was ground in a lab mortar and pestle with 135 grams of 1,2-dibromotetrafluoroethane to produce a viscous dispersion. The dispersion was used to coat a sheet of aluminum foil which was 38.1 microns thick. The coated foil was pressed in a heated hydraulic press at a pressure of 2000 psi (13,780 kPa) and at a temperature of 540F (282C) for 4 minutes and 20 seconds between glass reinforced polytetrafluoroethylene backing sheets.
The backing sheets were removed from the first polymer film and the coated side of the foil placed against a 5 mil (127 micron) thick film of the second ion exchange polymer film. The pressing opera-tion was repeated using 670 psig (4616 kPa) to attach the first film to the second film. The resulting-two-layer film was hydrolyzed in a 25 weight percent sodium hydroxide aqueous solution for 16 hours at a temperature of 90C. The aluminum foil dissolved in this process. The two-layer film was mounted in a test cell with the 755 equivalent weight polymer facing the cathode compartment.
34,247-F -24-~ ;~98927 After 190 days of operation in a chlor-alkali test cell as described in Example 2 to produce chlorine gas and NaOH from the electrolysis of a NaCl brine, produced a 33 weight % NaOH in an aqueous solution at a 95.6% caustic current efficiency and 3.38 volts.
Example 4 .. A copolymer of CF~=CF2 and CF2=CFOCF2CF2SO2F
having an equivalent weight of 1160 was prepared accord-ing to the following procedure. 50 Grams of CF2=CFOCF2CF2SO2F was added-to 300 milliliters of deoxygenated water containing 3 grams NH4CO2C7F1s, 1.5 grams of Na2HPO4-7H2O, 1 gram of NaH2PO4 H2O and 0.1 grams of (NH4)2S2Og under a positive pressure of 245 psig (1688 kPa) of tetrafluoroethylene at a temperature of 60C for 75 minutes in a glass reactor. The reactor was vented under heat and acidified to coagulate the latex. The coagulated polymer was washed repeatedly to remove inorganics and soap. The polymer was vacuum dried for 16 hours at a temperature of 110C.
30 Grams of the fluorosulfonyl copolymer was ground with 270 grams of 1,2-dibromotetrafluoroethane in a lab mortar and pestle until a viscous dispersion was produced.
.This dispersion was used to coat a sheet of aluminum foil having a thickness of 38.1 microns. The coating was allowed to air dry. The coated foil was then pressed between glass reinforced polytetrafluoro-ethylene backing sheets which were held between photo-graphic plates in a heated press. The pressure was 2000 psig (13,780 kPa) and the temperature was 595F
(313C). The time was 4 minutes and 20 seconds.
34,247-F -25-Thereafter, the backing sheet was removed from the press and a thin polymeric film emained on the foil.
A second copolymer was prepared. It was a copolymer of CF2=CF2 and CF2=CFOCF2CF2SO2F having an equivalent weight of 974. The polymer was prepared according to the following procedure. 784 Grams of CF2=CFOCF2CF~SO2F was added to 4700 grams of deoxygen-ated water containing 25 grams NH4COzC7Fl5~ 18.9 grams of Na2HPO4-7H2O, 15.6 grams of NaH2PO4 H2O and 4 grams of (NH4 )2S208 under a positive pressure of 220 psig (1516 kPa) of tetrafluoroethylene at a temperature of 60C for 30 minutes. The reactor was vented under heat and vacuum to remove residual monomers. The reactor contents was frozen, thawed, and vigorously washed to remove residual salts and soap. The film was vacuum dried for 16 hours at a temperature of 85C.
The second film was extruded on a commercially available Killion laboratory extruder with a regular Xaloy barrel and screw. The screw was a standard type commonly used to extrude polyethylene. Blown film was made with a 3.2 cm die with a 20 mil (508 micron) gap heated to a temperature of 550C using no cooling ring.
The extruder was operated at a temperature of from 450 to 550F (232 to 288C) and 20 to 40 revolutions per minute. The hauloff (a mechanical device to roll up the film) operated a~ a rate of 30 to 60 cm/min.
Various thicknesses of blown film were produced as desired by varying speeds and the blowing of the bubble.
A 5 mil (127 microns) extruded polymeric film 30 of 84K3023 fluorosulfonyl copolymer was placed against the coated side of the foil and pressed as above except 34,247-F -26-, 1~98927 only 670 psig (4613 kPa) pressure was used. This two layer film was hydrolyzed in 25 weight percent sodium hydroxide aqueous solution for 16 hours at a tempera-ture of 90C. The foil was etched away in this process.
The resulting two layer film was placed in a test cell (the same cell described in Example 3) with the 83P019 polymer facing the cathode compartment. After 2 days of operating the following results were obtained.
Cell voltage was found to be 3.02 volts and the caustic current efficiency was 91.5 percent at a caustic concentration of 12.56 weight percent. The sodium chloride concentration in the caustic was analyzed and found to be 940 parts per million. The cell energy was calculated to be about 2211 kilowatt hours per metric ton of caustic.
34,247-F -27-
Claims (21)
1. A dispersion composition for dispersing perfluorinated polymer particles in a dispersant wherein said perfluorinated polymer contains sites convertible to ion exchange groups and wherein said dispersant has a boiling point of less than 110°C;
a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and wherein the densities of the dispersant and the fluorinated polymer are selected such that they are balanced with each other.
a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and wherein the densities of the dispersant and the fluorinated polymer are selected such that they are balanced with each other.
2. The composition of Claim 1, wherein the perfluorinated polymer is a copolymer comprising a first monomer represented by the general formula:
CF2=CZZ' where:
Z and Z' are independently selected from -H,-Cl, -F, and CF3; and a second monomer represented by the general formula:
Y-(CF2)a-(CFRf)b-(CFRf,)c-O-[CF(CF2X)-CF2-O]n-CF=CF2 34,247-F -28-where:
Y is selected from -SO2Z, -CN, -COZ, and C(R3f)(R4f)OH;
Z is selected from I, Br, Cl, F, OR and NR1R2;
R is selected from a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
R3f and R4f are independently selected from perfluoroalkyl radicals having from 1 to 10 carbon atoms;
R1 and R2 are independently selected from H, a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
a is 0-6;
b is 0-6;
c is 0 or 1;
provided a+b+c is not equal to 0;
X is selected from Cl, Br,F and mixtures thereof when n>1, n is 0 to 6; and Rf and Rf' are independently selected from F, Cl, perfluoroalkyl radicals having from 1 to 10 carbon atoms and fluorochloroalkyl radicals having from 1 to 10 carbon atoms.
CF2=CZZ' where:
Z and Z' are independently selected from -H,-Cl, -F, and CF3; and a second monomer represented by the general formula:
Y-(CF2)a-(CFRf)b-(CFRf,)c-O-[CF(CF2X)-CF2-O]n-CF=CF2 34,247-F -28-where:
Y is selected from -SO2Z, -CN, -COZ, and C(R3f)(R4f)OH;
Z is selected from I, Br, Cl, F, OR and NR1R2;
R is selected from a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
R3f and R4f are independently selected from perfluoroalkyl radicals having from 1 to 10 carbon atoms;
R1 and R2 are independently selected from H, a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
a is 0-6;
b is 0-6;
c is 0 or 1;
provided a+b+c is not equal to 0;
X is selected from Cl, Br,F and mixtures thereof when n>1, n is 0 to 6; and Rf and Rf' are independently selected from F, Cl, perfluoroalkyl radicals having from 1 to 10 carbon atoms and fluorochloroalkyl radicals having from 1 to 10 carbon atoms.
3. The composition of Claim 2, wherein the perfluorinated polymer includes a third monomer represented by the general formula:
Y1-(CF2)a-(CFRf)b-(CFRf,)c-O-[CF(CF2X)-CF2-O]n-CF=CF2 where:
Y' is selected from F, Cl or Br;
a' and b' are independently 0-3;
c' is 0 or 1;
34,247-F -29-provided a'+b'+c' is not equal to 0;
n' is 0-6;
Rf and R'f are independently selected from Br.
Cl, F, perfluoroalkyl radicals having from 1 to 10 carbon atoms, and chloroperfluoroalkyl radicals having from 1 to 10 carbon atoms; and X' is selected from F, Cl, Br, and mixtures thereof when n'>1.
Y1-(CF2)a-(CFRf)b-(CFRf,)c-O-[CF(CF2X)-CF2-O]n-CF=CF2 where:
Y' is selected from F, Cl or Br;
a' and b' are independently 0-3;
c' is 0 or 1;
34,247-F -29-provided a'+b'+c' is not equal to 0;
n' is 0-6;
Rf and R'f are independently selected from Br.
Cl, F, perfluoroalkyl radicals having from 1 to 10 carbon atoms, and chloroperfluoroalkyl radicals having from 1 to 10 carbon atoms; and X' is selected from F, Cl, Br, and mixtures thereof when n'>1.
4. The composition of Claim 1, wherein the boiling point of the dispersant is from 30°C to 110°C.
5. The composition of Claim 1, wherein the solubility parameter of the dispersant is from greater than 7.1 to 7.5 hildebrands.
6. The composition of Claim 1, wherein the density of the dispersant and the density of the polymer are both from 1.55 to 2.2 grams per cubic centimeter.
7. The composition of Claim 1, wherein the dispersant has the general formula:
XCF2-CYZX' wherein:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms.
XCF2-CYZX' wherein:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms.
8. The composition of Claim 7, wherein X and X' are Br or Cl.
34,247-F -30-
34,247-F -30-
9. The composition of Claim 7, wherein the polymer is present in the dispersion at a concentration of from 0.1 to 50 weight percent.
10. The composition of Claim 7, wherein the polymer is present in the dispersion at a concentration of from 1 to 20 weight percent.
11. The composition of Claim 1, wherein the dispersant is selected from 1,2-dibromotetrafluoroethane or 1,2,3-trichlorotrifluoroethane.
12. A method for dispersing perfluorinated polymer particles containing sites convertible to ion exchange groups comprising the steps of:
contacting the polymer with a dispersant for a time and at a temperature sufficient to disperse at least a portion of the polymer in the solvent. wherein the dispersant has:
a boiling point less than l10°C:
a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and wherein the densities of the dispersant and the fluorinated polymer are selected such that they are balanced with each other.
contacting the polymer with a dispersant for a time and at a temperature sufficient to disperse at least a portion of the polymer in the solvent. wherein the dispersant has:
a boiling point less than l10°C:
a solubility parameter of from greater than 7.1 to 8.2 hildebrands, and wherein the densities of the dispersant and the fluorinated polymer are selected such that they are balanced with each other.
13. The method of Claim 12, wherein the boiling point of the dispersant is from 30°C to 110°C.
14. The method Or Claim 12, wherein the density of the dispersant and the density of the polymer are both from 1.55 to 2.2 grams per cubic centimeter.
34,247-F -31-
34,247-F -31-
15. The method of Claim 12, wherein the solubility parameter of the dispersant is from greater than 7.1 to 7.5 hildebrands.
16. The method of Claim 12, wherein the dispersant is represented by the general formula:
XCF2-CYZX' wherein:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms.
XCF2-CYZX' wherein:
X is selected from F, Cl, Br, and I;
X' is selected from Cl, Br, and I;
Y and Z are independently selected from H, F, Cl, Br, I and R';
R' is selected from perfluoroalkyl radicals and chloroperfluoroalkyl radicals having from 1 to 6 carbon atoms.
17. The method of Claim 16, wherein the dispersant is selected from 1,2-dibromotetrafluoroethane or 1,2,3-trichlorotrifluoroethane.
18. The method of Claim 12, wherein the polymer is present in the dispersion at a concentration of from 0.1 to 50 weight percent.
19. The method of Claim 18, wherein the polymer is present in the dispersion at a concentration of from 1 to 20 weight percent.
20. The method of Claim 12, wherein the perfluorinated polymer is a copolymer of a first monomer represented by the general formula:
CF2-CZZ' (I) 34,247-F -32-where:
Z and Z' are independently selected from -H, -Cl, -F, and CF3; and a second monomer represented by the general formula:
Y-(CF2)a-(CFRf)b-(CFRf,)c-O-[CF(CF2X)-CF2-O]n-CF=CF2 where:
Y is selected from -SO2Z, -CN, -COZ, and C(R3f)(R4f)OH;
Z is selected from I, Br, Cl, F, OR and NR1R2;
R is selected from a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
R3f and R4f are independently selected from perfluoroalkyl radicals having from 1 to 10 carbon atoms;
R1 and R2 are independently selected from H. a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
a is 0-6;
b is 0-6;
c is 0 or 1;
provided a+b+c is not equal to O;
X is selected from Cl, Br,F and mixtures thereof when n>1;
n is 0 to 6; and Rf and Rf' are independently selected from F, Cl, perfluoroalkyl radicals having from 1 to 10 carbon atoms and fluorochloroalkyl radicals having from 1 to 10 carbon atoms.
34, 247-F -33-
CF2-CZZ' (I) 34,247-F -32-where:
Z and Z' are independently selected from -H, -Cl, -F, and CF3; and a second monomer represented by the general formula:
Y-(CF2)a-(CFRf)b-(CFRf,)c-O-[CF(CF2X)-CF2-O]n-CF=CF2 where:
Y is selected from -SO2Z, -CN, -COZ, and C(R3f)(R4f)OH;
Z is selected from I, Br, Cl, F, OR and NR1R2;
R is selected from a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
R3f and R4f are independently selected from perfluoroalkyl radicals having from 1 to 10 carbon atoms;
R1 and R2 are independently selected from H. a branched or linear alkyl radical having from 1 to 10 carbon atoms and an aryl radical;
a is 0-6;
b is 0-6;
c is 0 or 1;
provided a+b+c is not equal to O;
X is selected from Cl, Br,F and mixtures thereof when n>1;
n is 0 to 6; and Rf and Rf' are independently selected from F, Cl, perfluoroalkyl radicals having from 1 to 10 carbon atoms and fluorochloroalkyl radicals having from 1 to 10 carbon atoms.
34, 247-F -33-
21. The method of Claim 20, including a third monomer represented by the general formula:
Y-(CF2)a-(CFRf)b-(CFRf')c-O-[CF(CF2X)-CF2-O]n-CF=CF2 where:
Y' is selected from F, Cl or Br;
a' and b' are independently 0-3;
c' is 0 or 1;
provided a"+b'+c' is not equal to 0;
n' is 0-6;
Rf and R'f are independently selected from Br, Cl, F, perfluoroalkyl radicals having from 1 to 10 carbon atoms, and chloroperfluoroalkyl radicals having from 1 to 10 carbon atoms; and X' is selected from F, Cl, Br, and mixtures thereof when n'>1, 34,247-F -34-
Y-(CF2)a-(CFRf)b-(CFRf')c-O-[CF(CF2X)-CF2-O]n-CF=CF2 where:
Y' is selected from F, Cl or Br;
a' and b' are independently 0-3;
c' is 0 or 1;
provided a"+b'+c' is not equal to 0;
n' is 0-6;
Rf and R'f are independently selected from Br, Cl, F, perfluoroalkyl radicals having from 1 to 10 carbon atoms, and chloroperfluoroalkyl radicals having from 1 to 10 carbon atoms; and X' is selected from F, Cl, Br, and mixtures thereof when n'>1, 34,247-F -34-
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US73995585A | 1985-05-31 | 1985-05-31 | |
| US739,955 | 1985-05-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1298927C true CA1298927C (en) | 1992-04-14 |
Family
ID=24974483
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000510632A Expired - Fee Related CA1298927C (en) | 1985-05-31 | 1986-06-02 | Fluoropolymer dispersions |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1298927C (en) |
-
1986
- 1986-06-02 CA CA000510632A patent/CA1298927C/en not_active Expired - Fee Related
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