CA1081884A - Tetrafluoroethylene polymer aromatic polyethersulphone coating compositions - Google Patents
Tetrafluoroethylene polymer aromatic polyethersulphone coating compositionsInfo
- Publication number
- CA1081884A CA1081884A CA258,111A CA258111A CA1081884A CA 1081884 A CA1081884 A CA 1081884A CA 258111 A CA258111 A CA 258111A CA 1081884 A CA1081884 A CA 1081884A
- Authority
- CA
- Canada
- Prior art keywords
- polyethersulphone
- dispersion
- polymer
- coating
- dispersion according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D127/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers
- C09D127/02—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
- C09D127/12—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C09D127/18—Homopolymers or copolymers of tetrafluoroethene
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
- B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
- B05D5/083—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface involving the use of fluoropolymers
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D181/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing sulfur, with or without nitrogen, oxygen, or carbon only; Coating compositions based on polysulfones; Coating compositions based on derivatives of such polymers
- C09D181/06—Polysulfones; Polyethersulfones
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L81/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing sulfur with or without nitrogen, oxygen or carbon only; Compositions of polysulfones; Compositions of derivatives of such polymers
- C08L81/06—Polysulfones; Polyethersulfones
Abstract
ABSTRACT OF THE DISCLOSURE
A coating composition comprises a dispersion of a fluorocarbon polymer in an inert diluent having dissolved, or preferably dispersed, therein a low molecular weight (RV less than 0.25) polyethersulphone or precursor thereto.
A coating composition comprises a dispersion of a fluorocarbon polymer in an inert diluent having dissolved, or preferably dispersed, therein a low molecular weight (RV less than 0.25) polyethersulphone or precursor thereto.
Description
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This invention relates to coating compositions and in particular to compositions that exhibit non-stick properties, e.g. for cookware.
Tetra~luoroethylene polymers, i.e. homopolymers 5 of tetrafluoroethylene and copolymers of tetrafluoro-ethylene with up to 1596 by weight of other monomers such as ethylens, vinyl chloride, vinyl fluoride and hexafIuoropropsne have heretofore been widely used for such applications, often in admixture with other 10 plastics materials which act as binders. An example i~ of such a coating composition is described in our U,K. patent specification 1 253 971.
In our U.K. patent specification 1 426 342 we describe coating compositions comprising a tetra-~ 15 fluoroethylene polymer and a thermoplastic aromatic ;~l polyethersulphone. The prefsrred polyethersulphones of those compositions had molecular weights corresponding to reduced viscosities of at least 0,3.
~j ~ Reduced viscosity (RV) as used herein refers to l~ 20 viscosity measurements made at 25C on a solution of J~ the polymer in dimethyl formamide containing 1 g of polymer in 1ao cm3 of solution.
We have found that while satisfactory coating ~¦ ~ compositions can be mads from such polysthersulphones 25 by dispersing the tetrafluoroethylene polymer in a solution of the polyethersulphone in a solvent therefor, e.g. dimethyl formamide, coatings made from wholly aqueous dispsrsions of such polyethersulphonss, while ~ exhibiting good adhesion to the substrate, are dis-`~ ~ 30 continuous. Such discontinuous coatings often have a speckled appearance in contrast to the uniform mat appearance of a continuous coating.
It has also been proposed in U.S. patent 3 622 376, to make coating compositions containing a poly(arylene ~, 35 sulphide) and titanium dioxide. It was proposed therein '' . , , ,:
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to incorporate n.5 to 50% by weight, based on the weight cr the poly(arylene sulphide), of a fluoro-carbon polymerJ i.e. a fluorocarbon polymer/poly-(arylene sulphide) weight ratio of 1:2 to 1:199.
Preferred compositions contained 5 to 20% by weight ~-r, of polytetrafluoroethylene (PTFE), i.e. a PTFE/poly-(arylene sulphide) weight ratio of 1:4 to 1:19, Such coating compositions wers preferably applied to the desired substrate in the form of a slurry of the ingredients in an inert diluent and, after diluent removal, were fused to give a continuous coating.
We have found that, by utilising low molecular weight polyethersulphones, continuous coatings exhibiting , good adhesion can be obtained from aqueous coating -dispersions. We have further found that coatings made ,j from such compositions exhibit improvsd adhesion compared with coatings made from a composition containing a ~j similar proportion of a poly~arylens sulphide). Thus i~ it is possible, by using the compositions of the present invbntion, to utilise a greater proportion of the tetrafluoroethylene polymer in the coating and so the lubricating, or ~non-stick~, properties of the coating are not decreased unduly by the presence of the binder polymer.
, 25 Accordingly we provide a coating dispersion i~ comprising a tetrafluoroethylene polymer dispersed in an inert diluent having dissolved, or preferably dis-persed, therein a thermoplastic aromatic polyethersulphone of reduced viscosity below 0.25, or the precursor to such a polyethersulphone, By the term precursor to a polyethersulphone, we mean monomeric material, which is polymerisable by the 3 action of heat, to form a polyethersulphone. Examples of such monomeric materials include alkali metal salts of phenols containing halophenylsulphonyl groups with ' ' ' ,"
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~- the halogen ortho or para to the sulphone group, such as the potassium salt of 4-~4-chlorophenylsulphonyl) phenol (the p~lymerisation of which to form polyether-sulphones is described in our U.K. patent 1 153 035) and mixtures in approximately equimolar amounts of a dialkali metal salt of a bisphenol with a dihalobenzenoid compound in which each halogen atom is activated by a sulphone group ortho or para thereto. Polymerisation of such a mixture, e.g. the dipotassium salt of 2,2-bis-(4-hydroxyphenyl)propane and bis-~4-chlorophenyl) sulphone, in the absence of a polar solvent has been described in, for example, U.K, patent specification 1 417 664.
`` We prefer howsver to utilise a preformed polymer.
15 The preferred polyethersulphones made by a nucleophilic polymerisation process may have halogen end groups or alkali metal phenate (-OM) end groups, (where M is alkali metal), When made from a single monomer, e.g. by self ' condensation of a halophenate, the halogen and phenate ~3 20 end groups will be present in equal proportions and ;~ polymerisation may continue, upon heating, after coating a substrate with the dispersion, producing a higher ~i molecular weight polymer and an alkali metal halide.
3 (This would also be the case if an equimolar mixture ,~ Z5 of an activated dihalobenzenoid compound and a bisphenate ~ ~ had been employed to make the polyethersulphone.) The J`~ formation of alkali metal halide in the coating is undesirable as it could be leached out, e.g. by washing of the coated article leaving pinholes which would 30 expose the substrate and, if the substrate is metallic, the alkali metal halide could promote corrosion. In ~ addition, in the case of coated cookware, pinholes give ;~ rise to the possibility of build up of food and/or s~ cooking oil or fat which could degrade and discolour ~ ;
~ 35 the cooking utensil. ~-1 . - , ~ ' " '',', ~
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, : - 5 -, For these reasons we prefer to use polyether- :
sulphones that do not contain phenate end`groups. Such ~
.`~ polyethersulphones may be made by the addition of a small r", amount of an activated dihalobenzenoid compound to ' 5 halophenate polymerisation so that any phenate end .:~ groups are reacted to give a polyethersulphone having .
~ halogen end groups. In the case of polyethersulphones .l made from an activated dihalobenzenoid compound and a .
.i bisphenate, a very slight excess of the dihalobenzenoid . 10 compound may be employed so as to obtain polyether-l sulphones with halide end groups.
However such processes are subject to variability ~' partly because the total amount of dihalobenzenoid compound present cannot be assessed su-fficiently accurately 15 or reproducibly.
An alternative method of obtaining a polyethersulphone r3 with stabilised end groups is by converting the phenate (-OM) . end groups remaining when polymerisation has proceeded to the desired extent to alkoxy ~-OR) end groups twhere R
20 is an alkyl group containing 1 to 4 carbon atoms) by addition of an alkyl halide such as methyl chloride, . Alternatively thè phenate end groups can be converted to -OH end groups by acidification or by reaction with an alkyl halide, such as t-butyl chloride, that eliminates 25 HCl rather than undergoes the substitution reaction. `:
`~ Such a process for the production of polyethersulphones having -OH end.groups is described in our Selgian patent 819 3û3.) : As disclosed in our U.K. patent specification : 1 342 589, polyethersulphones having -OH end groups .may give better adhssion than polyethersulphones having alkoxy end groups. .:
In addition we have found that the nature of the `
polyethersulphone end groups.has an effect on the :
35 viscosity of the dispersion and phenate end grouped ~
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'~` This results in a relatively thin coating on the substrate.For the above reasons, e,g, those connected with ~' the formation of alkali metal halide in the coating '':l 5 and the effect of the end groups, we prefer not to ~ -'1 ~ake the polyethersulphone in situ, i.e. we prefer '' not to use a precursor to the polyethersulphone, but rather we prefsr to employ a preform'ed polyethsrsulphone .5 not containing phenate end groups.
:', 10 To obtain satisfactory coatings, the RV of the ~, l polyethersulphone must be be'low 0.25. It can however be very low - thus polyethersulphones of RV 0.03 havs given good results.' We prefer to use polyethersulphones of RV between 0.0~ and 0.2 and in particular between 0.05 and 0.18. With polyethersulphones at the low end ~"1 of the molecular weight range, below RV 0.03, there is `~ a greater risk of the presence of organic material that c'' ' might be extracted in use. Furthermore the very low RV
' ~ polyethersulphones are harder to make consisten'tly on ;' 20 a commercial scale.
''~ While we prefer to use a single polyethersulphone, blends may be employed. 'For example a mixture of poly-;~ ethersulphones of RV below 0.25 may be usedJ alternatively, ' but less preferably, a polyethersulphone of RV above 0.25 '' 25 may be used in admixture with'one of RV below 0.25 provided ~ -that the RV of the mixture is below 0.25. Where two or ' more polyethersulphones are employed they may have the '~' ~ same or different repeat units.
i; It is desirable, in the interests of coating 30 'uniformity and dispersion stability, that the poly- '' ethersulphone has a particle size of below 25 ~m, as '~
measured by a Micromerograph tPennwalt Corporation, ' Pennsylvania, U.S.A.), preferably below 20 ~m. Preferably i the polyethersulphone has a particle size above 5 ~m 35 because it becomes more difficult and time consuming to ~' .,3 :
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obtain polyethersulphones of smaller particle size.
The use of low molecular weight polyethersulphones ;i~ (RV below O.Z5) also has the advantage that aqueous ,., ~................................................................... . .
dispersions thereof can more easily be made than with ~.
~;l 5 ~igh molecular weight polyethersulphones. Thus, while -it may take a week or more to obtain such a particle ;J size by ball milling a polyethersulphone of RV 0.42, a polyethersulphone of RV 0.21 can be ball milled, `~
under similar conditions, to below 25 ~m in less than 24 hours.
Thermoplastic-aromatic polyethersulphones comprise , repeat units of the general formula Ar-S02-in which Ar is a divalent aromatic radical, which may vary from unit to unit in the polymer chain, at least some of the Ar units having the structure -~
in which Y is oxygen or the divalent radical obtained by removal of the hydrogsn atoms from the OH groups of an aromatic diol such as a 4,4'-bisphenol. Up to 50% of the -S02- groups may be replaced by -CO- groups.
Examples of such polyethersulphonss have the repeating units '~ o-~;3so- ' ~
25 and ~ o ~ C(CH3)2 ~ O ~ SD2- ~-~ ~ alone or in conjunction with repeating units such as .~ ~ SD2-~ and ~ D ~ SD~-~, ,"~
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a -Exarnples of polyethersulphones and processes for their production are described in British patent specifications 1 016 245, 1 060 546, 1 078 234, 1 109 842, 1 122 192, 1 133 561, 1 153 035, 1 153 52H, 1 163 332, 1 177 1B3, 1 234 301, 1 264 90û, 1 265 144, 1 296 3~3, 1 298 821 ~, and 1 303 252, Canadian patent specification a47 963, German 0LC specifications 1 93B 806 and 2 433 400 and , Swiss patent specification 491 981.
I The compositions of the invention preferably have -~ 10 tetrafluoroethylene polymer/polyethersulphone (or ~ precursor thereto) weight ratios between 9:1 and 1:9, - particularly between 4:1 and 1:3.
As the proportion of tetrafluoroethylene polymer '`'i! ~ is increased, the coatings made from the dispersions become softer and more porous and less strongly adherent to the substrate. On the other hand the non-stick properties of the coatings deteriorate as the proportion of polyethersulphone increases. We therefore particularly prefer to employ tetrafluoroethylene polymer/polyether-sulphone weight ratios of between 0.75:1 and 2:1, most `
i; ~ preferably between 0.9:1 and 1.4:1.
,'t~ The dispersion preferably has a combined content of tetrafluoroethylene polymer and polyethersulphone of 20 to 50% by weight of the dispersion. The total solids ~3!~ 25 content of the dispersion ~i.e. weight of dispersed polymer plus any pigmsnts, fillers, etc) is preferably 30 to ~!~ 60~ by weight of the dispersion.
The coating dispersion is preferably an aqueous l dispersion as this avoids the presence`of organic ;1 30 solvents which may present handling problems. ;
However in some cases the dispersion may be a dispersion of the tetrafluoroethylene polymer in a ~;J solution of the polyethersulphone in a solvent such as ~ dimethyl formamide, N-methyl-2-pyrrolidone, dialkyl or '~f 35 diaryl sulphones and sulphoxides including 1,1-dioxothiolan ~ (sulpholane).
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:','., ~ ., Alternatively the tetrafluoroethylene polymsr may be dispersed in a dispersion of a polyethersulphone in a mixture of diluents, e.g. water and dimethyl formamide.
However, as stated above, the polyethersulphons is preferably dispersed in water. Such an aqueous di5persion may be made by ball milling polyethersulphone powder or granules with water in the presence of an emulsifier, or by precipitation from solution.
An altsrnative msthod of making the polyether-sulphone dispersion is by first making a solution of the polyethersulphone in a solvsnt such as methylene chloride, then forming an emulsion of that solution ;~
in water using a suitable emulsifier, 8,g. sodium dioctyl sulphosuccinate, and finally evaporating off the solvent.
The tetrafluoroethylene polymer is preferably polytetrafluoroethylene or a copolymer of tetrafluoro-ethylene with up to 5%, especial~y 0.05 to 2%, by weight of other monomers such as ethylene, vinyl chloride, hsxafluoropropene or perfluoropropyl perfluorovinyl stherJ preferably the tetrafluoroethylene polymer is ~-a ~lubricant grade~ polytetrafluoroethylene powder~
Such matsrials, which are commercially available, e.g. as thermally or irradiation degraded polytstrafluoroethylene powders, andare characterised by an average particle size of lsss than 20 ~m (as measured opticallyl. Examples of commercially available lubricant grade polytetra-fluoroethylens powders are 'Fluon~ L169, L170 and L171 sold by Imperial Chemical Industries Limited. For example 'Fluon' L170 is a friable polytetrafluoroethylene powder of 4 ~m median particle size which can be broken down to smaller particle size when processed in various media, ; e.g. by a high shear mixer.
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Other lubricant grade tetrafluoroethylene polymsrs that may ba employed are telomers of tetrafluoroethylene -I and known telogens which telomers can be obtained by telomeration in an organic medium as described for ~ 5 example in United States patent specifications 3 105 824 ;' and 3 067 262, or in aqueous emulsion as described in United Kingdom patent specification 1 391 246.
Thus coating dispersions in accordance with the present invention may be made by mixing a lubricant grade polytetrafluoroethylene powder or dispersion into ~l an aqueous polyethersulphone dispersion. Such mixing ~i is conveniently performsd using a high shear mixer.
The dispersions may also be mads by dry mixing the polyethersulphone and a tetrafluoroethylene polymer powder and then forming a dispersion from the mixture.
We therefore further provide, in accordance with the ~`~ present invention, a mixture of a tetrafluoroethylen3 polymer and a polyethersulphone of RV less than 0.25.
Other ingredients, e.g. pigments, fillers, emulsifiers, viscosity modifiers, may bs incorporated if desired. The incorporation of titanium dioxide as a pigment is particularly preferred as it beneficially i affects the sedimentation behaviour of the dispersion i ~ and, in some cases, the adhesion of the final coating.
!~ . 25 Preferred amounts of titanium dioxide are 1-10% by weight `lj of the dispersion.
j As disclosed in U.K. patent specification 1 337 434 the incorporation of 0.01 to 10% by weight of diphenyl ;--sulphone, based on the weight of ths polyethersulphone, into the polyethersulphone may act as a processing aid and its incorporation into the dispersions of the present ', invention, e.g. prior to milling the polyethersulphone, may give coatings of better appearance.
While it is preferred to utilise lubricant grade 35 polytetrafluoroethylene, it is also possible to utilise ` -: ~ :
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tetrafluoroethylens polymer aqueous dispersions. Such dispersions may be made by polymerisation of tetrafluoro-ethylene in an aqueous medium, normally in the presence of an emulsifying agent. Examples of such processes are described in ~ritish patent specifications 689 400 and B21 353. The emulsifying agent is preferably of the anionic type in the form of a fluorinated carboxylic acid compound such as ammonium perfluorooctanoate. For !'~
~ use in this invention, after polymerisation, the dis-,-!t,'", 10 persion is further stabilised by means of a surfactant and, if necessary, concentrated. A suitable stabilissr ~, is a non-ionic surfactant such as polyoxyethylated octyl phenol containing 9 to 10 moles of ethylene oxide per mole of octyl phenol sold by Rohm and Haas Company under ~k:., 15 the trademark 'Triton' X100 or a surfactant sold by / '', , ' . / '.'.' ~ /
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R~hm and Haas Company under the trademark ~Triton' DN65 u ~nd described by the suppliers as a modified ethoxylated ., straight chain alcohol. .~
We have found that, while satisfactory coatings can - .
' 5 be made by using mixturss, in accordance with the present ;~
.' invention, of an aqueous low molecular weight polyether- :
.l sulphone dispersion with an aqueous tetrafluoroethylene h;
~' polyrner dispersion, similar coatings made using a high ~ molecular weight (i,B. RV above 0.25) polyethersulphone .:
not only were discontinuous but also exhibited inferior ;~ adhesion. :
"N The substrates to which the coating compositions .:.
'~are applied should be clean and free from grease and ::
unless they have a fritted surface are preferably 15 roughened, for example by abrading by grit blasting or ..
. by etching, Coatings may be applied by any of the .. .
conventional techniques, including spraying, dipping ,~ and brushing, followed by drying. The coating is .
:~ . thsn-cured by heating, preferably in the prssence of .~ 20 air, at temperatures of 300C to 450CJ preferably :
above 350C and particularly between 380C to 400C.
Generally temperatures in excess of 350C should ;
be employed but the addition of a cross-linking agent such as sulphur in the coating composition.gave a coating ~3:.; 25 of acceptable appearance when cured at temperatures as .--. low as 300C. However the coatings tended to be softer ~.
than those cured at-above 350C.
:Likewise when using very low RV polyethersulphones ~.- ~ (RV below 0.1) coatings of satisfactory appearance may .~30 bs made when cured at temperatures as low as 300C but .. ~.
~.thé adhesion may, in some cases, be inferior to that ~.
:;........... obtained when using curing temperatures above 350C.
Where the polyethersulphone has hydroxyl (-OH) ;.
,;,end groups, such a heating step, if carried out in air, ~.. .
,~;;35 will result in an increase in the molecular weight of - . .
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the p~lyethersulphone, (as described in our U.K. patent ?~ specification 1 415 77B for high molecular weight poly-ethersulphones).
'1 The compositions of the present invention are f1 5 particularly suitable for use in low friction coating applications where excellent performance is required, for example, resistance to environmental high tem~eratures, e.g. more than 150C, consistent with good adhesion to substrates, The compositions of the invention may be applied as coatings to a variety of substrates, including glass, e.g. for non-stick ovenware and non-stick autoclave liningsJ ceramicsl composite surfaces such as a metal~
metals such as ferrous metals, for example cast iron, mild steel, stainless steel, and aluminium and its alloysJ
and composite surfaces such as metals having a reinforcing coating, such as a sprayed ceramic and~or metal powder coating. The substrate may bé in the form of sheet, tube, ,~ rod, wire, fibre, or woven fabric.
The compositions are particularly suited to coating cooking utensils for example frying pans, saucepans and I bakeware or for oven linings. In making cooking utensils, a blank may be coated and then formed, or an already formed ~ -~; utensil may be coated. --Compositions according to the invention may also be used to form adherent non-stick, low friction, coatings on many other articles including industrial procsssing equipment including moulds, rollers, stirrers, mixers, chutes, hoppers and heat sealing jaws, domestic articles such as iron sole plates, ?'`~ ~ food mixers and ice separators and tools such as saw blades, electrical applications such as for example wire insulation.
The service temperature that can be employed will depend on the nature of the polyethersulphone. Thus ; l .~, .
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while coatin~s made from dispersions containing poly-ethersulphone of repeat unit ~-, ~, . .
~3 o~SOz-~ can be used for "top-of-the-stove" cookware, e.g. frying `~ 5 pans, saucepans, as well as ovenware, coatings made from i~ dispersions containing polyethersulphone of repeat unit , .~! .
~' ~ ~ C(CH3)2 ~ O ~ S~2 are best used in applications subjected to lower service temperatures, e,g, ba~eware, egg boilers, and non cooking ~i 1û utensil applications such as coatings on hair curlers -:! and saws.
~ One particular non-cookware application for which ,~i the dispersions are particularly suited is the coating ,~ of glass cloth or other fabrics. For coating glass cloth, 15 it is in some cases desirable to incorporate very fine glass beads in the coating dispersion. Such coated ;l fabrics are of utility in the manufacture of air inflatable structures such as temporary aircraft hangers, exhibition ~!~ halls, etc. In some cases it is not necessary to cure , 2û the coating by heating to above 30~C. This is particularly the case with dispersions made using, as the dispersing medium for the tetrafluoroethylene polymer,~ a volatile non-aqueous solvent for the polyethersulphone.
Thus satisfactory coatings may be made on fabrics, 25 or other substrates that cannot withstand the normal curing temperatures employed, merely by evaporating ~; off the volatile solvent.
Such solvent based dispersions may also be used for coating polyethersulphone film so as to provide 30 a non-stick coating thereon.
3 The invention is illustrated by the following Examples: (Examples 1 to 3, 13 and 20 to 22 are com-parative.) ~3 ~ .
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'i~ EXAMPLE 1 ~ A sample ~50 g) of a thermoplastic polyethersulphone ' ;~ having repeat units o~ 50z-and a reduced viscosity of 0.42 was ball milled with an aqueous solution (200 g) containing 1.25% by weight A of an adduct of approximately 9 to 10 moles of ethylene i~ oxide with 1 mole of octyi phenol as a non-ionic ~; smulsifier, in a ceramic ball mill for 432 hours after 10 which time the average particle size was 1~ ~m as ' measured by a Micromerograph.
To a portion (142 g) of the'resultant dispersion were added: a lubricant grade polytetrafluoroethylene powder median particle diameter 3 to 4 ~m, 'Fluon' L171, '' (14.2 g), titanium dioxide t7.1 g), a carbon b-lack pigment ' (10.65 g), a further quàntity of the non-ionic emulsifier (5,6B g of a solution containing 1 part by weight of ' emulsifier to 2 parts by weight of wat~r) and a hydrous ; magnesium silicate viscosity modifier, (7.17 g of a gel `~ Z0 made by mixing 2.5 parts by weight of ~entone EW with ~ -97.5 parts by weight of water).
'~ ~ These ingredients were mixed with the polyether-sulphone dispersion using a Silverson mixer.
he~dispersion was thén sprayed on to a degreased ~` 25 ~ aluminium plate which was then dried'in an air oven at B0C for 10 minutes and then sintered in air at 400C
for 10 minutes.
The coating thickness was 21 ~m as measured by a ~Permascope~ (Helmut Fischer GmbH, Maichingen, Germany).
To assess adhesion of the coating the fol-lowing procedure is adopted: ' The test plaque is immersed in boiling water for 15 minutes and then dried. A cross-hatch pattern of cuts providing approximately 2 mm x 2 mm squares over . ',, '' ,.
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'J 15 an area of 650 mm is then applied to the coating using a razor blade to cut through the coating and into the -metal. A length of 25 mm wide, pressure-se!~sitiv~
3j adhesive tapa is firmly pressed over the cross- -; 5 hatched area and the tape is subsequently pulled sharply backwards at an angle of 45 to the direction of ' application. The application, and removal, of tape to the cross-hatched area is repsated with fresh pieces of tape until there is evidsnce that the coating is detaching from the metal or, if no failure is observed, up to a maximum of 15 times. A coating that survives five applications is considered satisfactory. The adhesion j~ can also be assessed qualitatively by the ease of peeling off the coating lafter the immersion in boiling water) with a thumbnail after penetrating the coating with a ¦ scalpel to expose the aluminium substrate. The ease of removal is assessed on a scaIe of 5 (good) to 0 (poor).
A grading of 4 or lower is recorded as a failure. The coating of this example had a grading of 5. Thus by both tests the adhesion was satisfactory.
Example 1 was repeated, but stopping the milling as soon as the polyethersulphone had reached a suitable particle size, with polyethersulphones of differing reduced viscosities. As slightly different sized samples of the polyethersulphone dispersion were taken for mixing with the polytetrafluoroethylene and other ingredients, the quantities of the polytetrafluoroethylene and other ` ingredients employed were adjusted to ensure that -the coating compositions had the`same solids content ~; and proportions of ingredients. The results are shown in Table 1. In all cases adhesion, as assessed by both methods, was adsquate.
Similar results were obtained using the polyether-sulphone of repeat unit ~O~.C(CH3)2~0~S02 . .,-, ...
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s in place of that of repeat unit ~30~3so2- , :- ,,, ~ EXAMPLE 11 `~ A polytetrafluoroethylene containing dispersion was made up as in Example 1 but using the potassium ¦ salt of 4-(4-chlorophenylsulphonyl)ph.enol (37.5 g) ..
dissolved in water (104.5 g) in place of the 142 g of , polyethersulphone dispersion. .. ~:.
The results are shown in Table 1. The adhesion.was .
10 satisfactory as measured by ths adhesive tape test but ~.
on~the thumbnail test the adhesion was inferior to that of the coatings of Examples .1 to 10. : .
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A dispersion similar to that of Example 7 ~poly-ethersulphone RV 0 15) was made but using an aqueous polytetrafluoroethylene dispersion ('Fluon' GP1) in ; 5 place of the lubricant powder ('Fluon' L171) The j amount of the polytetrafluoroethylene dispersion e~ployed (which contained 60% by weight of polytetrafluoroethylene ~ and 6% by weight of a non-ionic surfactant and was made ~ -r by polymerisation of tetrafluoroethylens in an aqueous medium in the presence of a perfluorinated emulsifier , followed by concentration) was such as to give a poly-tetrafluoroethylene/polyethersulphone weight ratio of ' 1:2.
Aluminium plates were coated using the-above mixture and the conditions employed in ths preceding Examples.
The coating, of thicknsss 10 ~m, was continuous having a slightly misty appearance and adequate adhesion. `
By way of comparison Example 12 was repeated but, in place of the polyethersulphone of RV 0.15, a hydroxy ended polyethersulphone (1.02 OH groups per 100 polymer repeat units) of RV 0.49 was used. The ball milling timo to give a polyethersulphone dispersion of average particle size 14 ~m was 16~ hours.
The coating was discontinuous and also failed the thumbnail adhesion test, bsing scraped off on the first scratch with ths thumbnail.
EX~MpLES 14 TO 19 ` Example 7 was repeated but using different proportions of the polyethersulphone of RV 0,15 so that the dispersions had tetrafluoroethylene polymer/polyethersulphone weight ratios ranging from 0.5:1 to 2:1. The curing times were increased to 15 minutes at aoc and 15 minutes at 400C.
The results are shown in Table 2.
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` TA~LE 2 ~rookfield Appearance , Example PTFE/polyether- Viscosity (CP) (under 50X
sulphone ratio at 30 rpm magnification) 14 0.5:1 536 Good 1:1 764 Good 16 1,21:1 593 Good 17 1.4~:1 693 porous 1~ 1,73:1 767 Porous 19 2:1 550 Porous 1 . .~
The adhesion of ths coatings of Examples 1~ and 19 was slightly inferior ton the thumbnail test) to that of Examples 14 to 17. The adhe~ion of all the coatings as ~ `
assessed by the adhesive tape test was satisfactory.
; EXAMPLES 20 T0 2Z
By way of comparison dispersions similar to those of Exampl~ 7 were made but using a polyphenylene sulphide t'Ryton' V1 sold by Phillips Petroleum Company) in place of the polyethersulphone. The milling time, to average particle size 13 ~m~was 18 hours. Dispersions were made with varying tetrafluoroethylene polymer/polyphenylene sulphide ratios.
Aluminium plates were coated with ths dispersions using the conditions adopted in the previous Examples.
The coatings were continuous but had poor adhesion as --shown in Table 3.
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This invention relates to coating compositions and in particular to compositions that exhibit non-stick properties, e.g. for cookware.
Tetra~luoroethylene polymers, i.e. homopolymers 5 of tetrafluoroethylene and copolymers of tetrafluoro-ethylene with up to 1596 by weight of other monomers such as ethylens, vinyl chloride, vinyl fluoride and hexafIuoropropsne have heretofore been widely used for such applications, often in admixture with other 10 plastics materials which act as binders. An example i~ of such a coating composition is described in our U,K. patent specification 1 253 971.
In our U.K. patent specification 1 426 342 we describe coating compositions comprising a tetra-~ 15 fluoroethylene polymer and a thermoplastic aromatic ;~l polyethersulphone. The prefsrred polyethersulphones of those compositions had molecular weights corresponding to reduced viscosities of at least 0,3.
~j ~ Reduced viscosity (RV) as used herein refers to l~ 20 viscosity measurements made at 25C on a solution of J~ the polymer in dimethyl formamide containing 1 g of polymer in 1ao cm3 of solution.
We have found that while satisfactory coating ~¦ ~ compositions can be mads from such polysthersulphones 25 by dispersing the tetrafluoroethylene polymer in a solution of the polyethersulphone in a solvent therefor, e.g. dimethyl formamide, coatings made from wholly aqueous dispsrsions of such polyethersulphonss, while ~ exhibiting good adhesion to the substrate, are dis-`~ ~ 30 continuous. Such discontinuous coatings often have a speckled appearance in contrast to the uniform mat appearance of a continuous coating.
It has also been proposed in U.S. patent 3 622 376, to make coating compositions containing a poly(arylene ~, 35 sulphide) and titanium dioxide. It was proposed therein '' . , , ,:
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1081884 P 2~077 .`'', ' .
to incorporate n.5 to 50% by weight, based on the weight cr the poly(arylene sulphide), of a fluoro-carbon polymerJ i.e. a fluorocarbon polymer/poly-(arylene sulphide) weight ratio of 1:2 to 1:199.
Preferred compositions contained 5 to 20% by weight ~-r, of polytetrafluoroethylene (PTFE), i.e. a PTFE/poly-(arylene sulphide) weight ratio of 1:4 to 1:19, Such coating compositions wers preferably applied to the desired substrate in the form of a slurry of the ingredients in an inert diluent and, after diluent removal, were fused to give a continuous coating.
We have found that, by utilising low molecular weight polyethersulphones, continuous coatings exhibiting , good adhesion can be obtained from aqueous coating -dispersions. We have further found that coatings made ,j from such compositions exhibit improvsd adhesion compared with coatings made from a composition containing a ~j similar proportion of a poly~arylens sulphide). Thus i~ it is possible, by using the compositions of the present invbntion, to utilise a greater proportion of the tetrafluoroethylene polymer in the coating and so the lubricating, or ~non-stick~, properties of the coating are not decreased unduly by the presence of the binder polymer.
, 25 Accordingly we provide a coating dispersion i~ comprising a tetrafluoroethylene polymer dispersed in an inert diluent having dissolved, or preferably dis-persed, therein a thermoplastic aromatic polyethersulphone of reduced viscosity below 0.25, or the precursor to such a polyethersulphone, By the term precursor to a polyethersulphone, we mean monomeric material, which is polymerisable by the 3 action of heat, to form a polyethersulphone. Examples of such monomeric materials include alkali metal salts of phenols containing halophenylsulphonyl groups with ' ' ' ,"
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~- the halogen ortho or para to the sulphone group, such as the potassium salt of 4-~4-chlorophenylsulphonyl) phenol (the p~lymerisation of which to form polyether-sulphones is described in our U.K. patent 1 153 035) and mixtures in approximately equimolar amounts of a dialkali metal salt of a bisphenol with a dihalobenzenoid compound in which each halogen atom is activated by a sulphone group ortho or para thereto. Polymerisation of such a mixture, e.g. the dipotassium salt of 2,2-bis-(4-hydroxyphenyl)propane and bis-~4-chlorophenyl) sulphone, in the absence of a polar solvent has been described in, for example, U.K, patent specification 1 417 664.
`` We prefer howsver to utilise a preformed polymer.
15 The preferred polyethersulphones made by a nucleophilic polymerisation process may have halogen end groups or alkali metal phenate (-OM) end groups, (where M is alkali metal), When made from a single monomer, e.g. by self ' condensation of a halophenate, the halogen and phenate ~3 20 end groups will be present in equal proportions and ;~ polymerisation may continue, upon heating, after coating a substrate with the dispersion, producing a higher ~i molecular weight polymer and an alkali metal halide.
3 (This would also be the case if an equimolar mixture ,~ Z5 of an activated dihalobenzenoid compound and a bisphenate ~ ~ had been employed to make the polyethersulphone.) The J`~ formation of alkali metal halide in the coating is undesirable as it could be leached out, e.g. by washing of the coated article leaving pinholes which would 30 expose the substrate and, if the substrate is metallic, the alkali metal halide could promote corrosion. In ~ addition, in the case of coated cookware, pinholes give ;~ rise to the possibility of build up of food and/or s~ cooking oil or fat which could degrade and discolour ~ ;
~ 35 the cooking utensil. ~-1 . - , ~ ' " '',', ~
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, : - 5 -, For these reasons we prefer to use polyether- :
sulphones that do not contain phenate end`groups. Such ~
.`~ polyethersulphones may be made by the addition of a small r", amount of an activated dihalobenzenoid compound to ' 5 halophenate polymerisation so that any phenate end .:~ groups are reacted to give a polyethersulphone having .
~ halogen end groups. In the case of polyethersulphones .l made from an activated dihalobenzenoid compound and a .
.i bisphenate, a very slight excess of the dihalobenzenoid . 10 compound may be employed so as to obtain polyether-l sulphones with halide end groups.
However such processes are subject to variability ~' partly because the total amount of dihalobenzenoid compound present cannot be assessed su-fficiently accurately 15 or reproducibly.
An alternative method of obtaining a polyethersulphone r3 with stabilised end groups is by converting the phenate (-OM) . end groups remaining when polymerisation has proceeded to the desired extent to alkoxy ~-OR) end groups twhere R
20 is an alkyl group containing 1 to 4 carbon atoms) by addition of an alkyl halide such as methyl chloride, . Alternatively thè phenate end groups can be converted to -OH end groups by acidification or by reaction with an alkyl halide, such as t-butyl chloride, that eliminates 25 HCl rather than undergoes the substitution reaction. `:
`~ Such a process for the production of polyethersulphones having -OH end.groups is described in our Selgian patent 819 3û3.) : As disclosed in our U.K. patent specification : 1 342 589, polyethersulphones having -OH end groups .may give better adhssion than polyethersulphones having alkoxy end groups. .:
In addition we have found that the nature of the `
polyethersulphone end groups.has an effect on the :
35 viscosity of the dispersion and phenate end grouped ~
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~ 108~8~4 P 28077 .' :: -- Ei -'.~. ' '' polyethersulphones tend to give low viscosity dispersions.
'~` This results in a relatively thin coating on the substrate.For the above reasons, e,g, those connected with ~' the formation of alkali metal halide in the coating '':l 5 and the effect of the end groups, we prefer not to ~ -'1 ~ake the polyethersulphone in situ, i.e. we prefer '' not to use a precursor to the polyethersulphone, but rather we prefsr to employ a preform'ed polyethsrsulphone .5 not containing phenate end groups.
:', 10 To obtain satisfactory coatings, the RV of the ~, l polyethersulphone must be be'low 0.25. It can however be very low - thus polyethersulphones of RV 0.03 havs given good results.' We prefer to use polyethersulphones of RV between 0.0~ and 0.2 and in particular between 0.05 and 0.18. With polyethersulphones at the low end ~"1 of the molecular weight range, below RV 0.03, there is `~ a greater risk of the presence of organic material that c'' ' might be extracted in use. Furthermore the very low RV
' ~ polyethersulphones are harder to make consisten'tly on ;' 20 a commercial scale.
''~ While we prefer to use a single polyethersulphone, blends may be employed. 'For example a mixture of poly-;~ ethersulphones of RV below 0.25 may be usedJ alternatively, ' but less preferably, a polyethersulphone of RV above 0.25 '' 25 may be used in admixture with'one of RV below 0.25 provided ~ -that the RV of the mixture is below 0.25. Where two or ' more polyethersulphones are employed they may have the '~' ~ same or different repeat units.
i; It is desirable, in the interests of coating 30 'uniformity and dispersion stability, that the poly- '' ethersulphone has a particle size of below 25 ~m, as '~
measured by a Micromerograph tPennwalt Corporation, ' Pennsylvania, U.S.A.), preferably below 20 ~m. Preferably i the polyethersulphone has a particle size above 5 ~m 35 because it becomes more difficult and time consuming to ~' .,3 :
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obtain polyethersulphones of smaller particle size.
The use of low molecular weight polyethersulphones ;i~ (RV below O.Z5) also has the advantage that aqueous ,., ~................................................................... . .
dispersions thereof can more easily be made than with ~.
~;l 5 ~igh molecular weight polyethersulphones. Thus, while -it may take a week or more to obtain such a particle ;J size by ball milling a polyethersulphone of RV 0.42, a polyethersulphone of RV 0.21 can be ball milled, `~
under similar conditions, to below 25 ~m in less than 24 hours.
Thermoplastic-aromatic polyethersulphones comprise , repeat units of the general formula Ar-S02-in which Ar is a divalent aromatic radical, which may vary from unit to unit in the polymer chain, at least some of the Ar units having the structure -~
in which Y is oxygen or the divalent radical obtained by removal of the hydrogsn atoms from the OH groups of an aromatic diol such as a 4,4'-bisphenol. Up to 50% of the -S02- groups may be replaced by -CO- groups.
Examples of such polyethersulphonss have the repeating units '~ o-~;3so- ' ~
25 and ~ o ~ C(CH3)2 ~ O ~ SD2- ~-~ ~ alone or in conjunction with repeating units such as .~ ~ SD2-~ and ~ D ~ SD~-~, ,"~
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a -Exarnples of polyethersulphones and processes for their production are described in British patent specifications 1 016 245, 1 060 546, 1 078 234, 1 109 842, 1 122 192, 1 133 561, 1 153 035, 1 153 52H, 1 163 332, 1 177 1B3, 1 234 301, 1 264 90û, 1 265 144, 1 296 3~3, 1 298 821 ~, and 1 303 252, Canadian patent specification a47 963, German 0LC specifications 1 93B 806 and 2 433 400 and , Swiss patent specification 491 981.
I The compositions of the invention preferably have -~ 10 tetrafluoroethylene polymer/polyethersulphone (or ~ precursor thereto) weight ratios between 9:1 and 1:9, - particularly between 4:1 and 1:3.
As the proportion of tetrafluoroethylene polymer '`'i! ~ is increased, the coatings made from the dispersions become softer and more porous and less strongly adherent to the substrate. On the other hand the non-stick properties of the coatings deteriorate as the proportion of polyethersulphone increases. We therefore particularly prefer to employ tetrafluoroethylene polymer/polyether-sulphone weight ratios of between 0.75:1 and 2:1, most `
i; ~ preferably between 0.9:1 and 1.4:1.
,'t~ The dispersion preferably has a combined content of tetrafluoroethylene polymer and polyethersulphone of 20 to 50% by weight of the dispersion. The total solids ~3!~ 25 content of the dispersion ~i.e. weight of dispersed polymer plus any pigmsnts, fillers, etc) is preferably 30 to ~!~ 60~ by weight of the dispersion.
The coating dispersion is preferably an aqueous l dispersion as this avoids the presence`of organic ;1 30 solvents which may present handling problems. ;
However in some cases the dispersion may be a dispersion of the tetrafluoroethylene polymer in a ~;J solution of the polyethersulphone in a solvent such as ~ dimethyl formamide, N-methyl-2-pyrrolidone, dialkyl or '~f 35 diaryl sulphones and sulphoxides including 1,1-dioxothiolan ~ (sulpholane).
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However, as stated above, the polyethersulphons is preferably dispersed in water. Such an aqueous di5persion may be made by ball milling polyethersulphone powder or granules with water in the presence of an emulsifier, or by precipitation from solution.
An altsrnative msthod of making the polyether-sulphone dispersion is by first making a solution of the polyethersulphone in a solvsnt such as methylene chloride, then forming an emulsion of that solution ;~
in water using a suitable emulsifier, 8,g. sodium dioctyl sulphosuccinate, and finally evaporating off the solvent.
The tetrafluoroethylene polymer is preferably polytetrafluoroethylene or a copolymer of tetrafluoro-ethylene with up to 5%, especial~y 0.05 to 2%, by weight of other monomers such as ethylene, vinyl chloride, hsxafluoropropene or perfluoropropyl perfluorovinyl stherJ preferably the tetrafluoroethylene polymer is ~-a ~lubricant grade~ polytetrafluoroethylene powder~
Such matsrials, which are commercially available, e.g. as thermally or irradiation degraded polytstrafluoroethylene powders, andare characterised by an average particle size of lsss than 20 ~m (as measured opticallyl. Examples of commercially available lubricant grade polytetra-fluoroethylens powders are 'Fluon~ L169, L170 and L171 sold by Imperial Chemical Industries Limited. For example 'Fluon' L170 is a friable polytetrafluoroethylene powder of 4 ~m median particle size which can be broken down to smaller particle size when processed in various media, ; e.g. by a high shear mixer.
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Other lubricant grade tetrafluoroethylene polymsrs that may ba employed are telomers of tetrafluoroethylene -I and known telogens which telomers can be obtained by telomeration in an organic medium as described for ~ 5 example in United States patent specifications 3 105 824 ;' and 3 067 262, or in aqueous emulsion as described in United Kingdom patent specification 1 391 246.
Thus coating dispersions in accordance with the present invention may be made by mixing a lubricant grade polytetrafluoroethylene powder or dispersion into ~l an aqueous polyethersulphone dispersion. Such mixing ~i is conveniently performsd using a high shear mixer.
The dispersions may also be mads by dry mixing the polyethersulphone and a tetrafluoroethylene polymer powder and then forming a dispersion from the mixture.
We therefore further provide, in accordance with the ~`~ present invention, a mixture of a tetrafluoroethylen3 polymer and a polyethersulphone of RV less than 0.25.
Other ingredients, e.g. pigments, fillers, emulsifiers, viscosity modifiers, may bs incorporated if desired. The incorporation of titanium dioxide as a pigment is particularly preferred as it beneficially i affects the sedimentation behaviour of the dispersion i ~ and, in some cases, the adhesion of the final coating.
!~ . 25 Preferred amounts of titanium dioxide are 1-10% by weight `lj of the dispersion.
j As disclosed in U.K. patent specification 1 337 434 the incorporation of 0.01 to 10% by weight of diphenyl ;--sulphone, based on the weight of ths polyethersulphone, into the polyethersulphone may act as a processing aid and its incorporation into the dispersions of the present ', invention, e.g. prior to milling the polyethersulphone, may give coatings of better appearance.
While it is preferred to utilise lubricant grade 35 polytetrafluoroethylene, it is also possible to utilise ` -: ~ :
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tetrafluoroethylens polymer aqueous dispersions. Such dispersions may be made by polymerisation of tetrafluoro-ethylene in an aqueous medium, normally in the presence of an emulsifying agent. Examples of such processes are described in ~ritish patent specifications 689 400 and B21 353. The emulsifying agent is preferably of the anionic type in the form of a fluorinated carboxylic acid compound such as ammonium perfluorooctanoate. For !'~
~ use in this invention, after polymerisation, the dis-,-!t,'", 10 persion is further stabilised by means of a surfactant and, if necessary, concentrated. A suitable stabilissr ~, is a non-ionic surfactant such as polyoxyethylated octyl phenol containing 9 to 10 moles of ethylene oxide per mole of octyl phenol sold by Rohm and Haas Company under ~k:., 15 the trademark 'Triton' X100 or a surfactant sold by / '', , ' . / '.'.' ~ /
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R~hm and Haas Company under the trademark ~Triton' DN65 u ~nd described by the suppliers as a modified ethoxylated ., straight chain alcohol. .~
We have found that, while satisfactory coatings can - .
' 5 be made by using mixturss, in accordance with the present ;~
.' invention, of an aqueous low molecular weight polyether- :
.l sulphone dispersion with an aqueous tetrafluoroethylene h;
~' polyrner dispersion, similar coatings made using a high ~ molecular weight (i,B. RV above 0.25) polyethersulphone .:
not only were discontinuous but also exhibited inferior ;~ adhesion. :
"N The substrates to which the coating compositions .:.
'~are applied should be clean and free from grease and ::
unless they have a fritted surface are preferably 15 roughened, for example by abrading by grit blasting or ..
. by etching, Coatings may be applied by any of the .. .
conventional techniques, including spraying, dipping ,~ and brushing, followed by drying. The coating is .
:~ . thsn-cured by heating, preferably in the prssence of .~ 20 air, at temperatures of 300C to 450CJ preferably :
above 350C and particularly between 380C to 400C.
Generally temperatures in excess of 350C should ;
be employed but the addition of a cross-linking agent such as sulphur in the coating composition.gave a coating ~3:.; 25 of acceptable appearance when cured at temperatures as .--. low as 300C. However the coatings tended to be softer ~.
than those cured at-above 350C.
:Likewise when using very low RV polyethersulphones ~.- ~ (RV below 0.1) coatings of satisfactory appearance may .~30 bs made when cured at temperatures as low as 300C but .. ~.
~.thé adhesion may, in some cases, be inferior to that ~.
:;........... obtained when using curing temperatures above 350C.
Where the polyethersulphone has hydroxyl (-OH) ;.
,;,end groups, such a heating step, if carried out in air, ~.. .
,~;;35 will result in an increase in the molecular weight of - . .
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the p~lyethersulphone, (as described in our U.K. patent ?~ specification 1 415 77B for high molecular weight poly-ethersulphones).
'1 The compositions of the present invention are f1 5 particularly suitable for use in low friction coating applications where excellent performance is required, for example, resistance to environmental high tem~eratures, e.g. more than 150C, consistent with good adhesion to substrates, The compositions of the invention may be applied as coatings to a variety of substrates, including glass, e.g. for non-stick ovenware and non-stick autoclave liningsJ ceramicsl composite surfaces such as a metal~
metals such as ferrous metals, for example cast iron, mild steel, stainless steel, and aluminium and its alloysJ
and composite surfaces such as metals having a reinforcing coating, such as a sprayed ceramic and~or metal powder coating. The substrate may bé in the form of sheet, tube, ,~ rod, wire, fibre, or woven fabric.
The compositions are particularly suited to coating cooking utensils for example frying pans, saucepans and I bakeware or for oven linings. In making cooking utensils, a blank may be coated and then formed, or an already formed ~ -~; utensil may be coated. --Compositions according to the invention may also be used to form adherent non-stick, low friction, coatings on many other articles including industrial procsssing equipment including moulds, rollers, stirrers, mixers, chutes, hoppers and heat sealing jaws, domestic articles such as iron sole plates, ?'`~ ~ food mixers and ice separators and tools such as saw blades, electrical applications such as for example wire insulation.
The service temperature that can be employed will depend on the nature of the polyethersulphone. Thus ; l .~, .
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while coatin~s made from dispersions containing poly-ethersulphone of repeat unit ~-, ~, . .
~3 o~SOz-~ can be used for "top-of-the-stove" cookware, e.g. frying `~ 5 pans, saucepans, as well as ovenware, coatings made from i~ dispersions containing polyethersulphone of repeat unit , .~! .
~' ~ ~ C(CH3)2 ~ O ~ S~2 are best used in applications subjected to lower service temperatures, e,g, ba~eware, egg boilers, and non cooking ~i 1û utensil applications such as coatings on hair curlers -:! and saws.
~ One particular non-cookware application for which ,~i the dispersions are particularly suited is the coating ,~ of glass cloth or other fabrics. For coating glass cloth, 15 it is in some cases desirable to incorporate very fine glass beads in the coating dispersion. Such coated ;l fabrics are of utility in the manufacture of air inflatable structures such as temporary aircraft hangers, exhibition ~!~ halls, etc. In some cases it is not necessary to cure , 2û the coating by heating to above 30~C. This is particularly the case with dispersions made using, as the dispersing medium for the tetrafluoroethylene polymer,~ a volatile non-aqueous solvent for the polyethersulphone.
Thus satisfactory coatings may be made on fabrics, 25 or other substrates that cannot withstand the normal curing temperatures employed, merely by evaporating ~; off the volatile solvent.
Such solvent based dispersions may also be used for coating polyethersulphone film so as to provide 30 a non-stick coating thereon.
3 The invention is illustrated by the following Examples: (Examples 1 to 3, 13 and 20 to 22 are com-parative.) ~3 ~ .
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'i~ EXAMPLE 1 ~ A sample ~50 g) of a thermoplastic polyethersulphone ' ;~ having repeat units o~ 50z-and a reduced viscosity of 0.42 was ball milled with an aqueous solution (200 g) containing 1.25% by weight A of an adduct of approximately 9 to 10 moles of ethylene i~ oxide with 1 mole of octyi phenol as a non-ionic ~; smulsifier, in a ceramic ball mill for 432 hours after 10 which time the average particle size was 1~ ~m as ' measured by a Micromerograph.
To a portion (142 g) of the'resultant dispersion were added: a lubricant grade polytetrafluoroethylene powder median particle diameter 3 to 4 ~m, 'Fluon' L171, '' (14.2 g), titanium dioxide t7.1 g), a carbon b-lack pigment ' (10.65 g), a further quàntity of the non-ionic emulsifier (5,6B g of a solution containing 1 part by weight of ' emulsifier to 2 parts by weight of wat~r) and a hydrous ; magnesium silicate viscosity modifier, (7.17 g of a gel `~ Z0 made by mixing 2.5 parts by weight of ~entone EW with ~ -97.5 parts by weight of water).
'~ ~ These ingredients were mixed with the polyether-sulphone dispersion using a Silverson mixer.
he~dispersion was thén sprayed on to a degreased ~` 25 ~ aluminium plate which was then dried'in an air oven at B0C for 10 minutes and then sintered in air at 400C
for 10 minutes.
The coating thickness was 21 ~m as measured by a ~Permascope~ (Helmut Fischer GmbH, Maichingen, Germany).
To assess adhesion of the coating the fol-lowing procedure is adopted: ' The test plaque is immersed in boiling water for 15 minutes and then dried. A cross-hatch pattern of cuts providing approximately 2 mm x 2 mm squares over . ',, '' ,.
. .. ',.
, '.
.. ...
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, :. :. : .
~-` 10818B4 P 28077 -; :. . . .
'J 15 an area of 650 mm is then applied to the coating using a razor blade to cut through the coating and into the -metal. A length of 25 mm wide, pressure-se!~sitiv~
3j adhesive tapa is firmly pressed over the cross- -; 5 hatched area and the tape is subsequently pulled sharply backwards at an angle of 45 to the direction of ' application. The application, and removal, of tape to the cross-hatched area is repsated with fresh pieces of tape until there is evidsnce that the coating is detaching from the metal or, if no failure is observed, up to a maximum of 15 times. A coating that survives five applications is considered satisfactory. The adhesion j~ can also be assessed qualitatively by the ease of peeling off the coating lafter the immersion in boiling water) with a thumbnail after penetrating the coating with a ¦ scalpel to expose the aluminium substrate. The ease of removal is assessed on a scaIe of 5 (good) to 0 (poor).
A grading of 4 or lower is recorded as a failure. The coating of this example had a grading of 5. Thus by both tests the adhesion was satisfactory.
Example 1 was repeated, but stopping the milling as soon as the polyethersulphone had reached a suitable particle size, with polyethersulphones of differing reduced viscosities. As slightly different sized samples of the polyethersulphone dispersion were taken for mixing with the polytetrafluoroethylene and other ingredients, the quantities of the polytetrafluoroethylene and other ` ingredients employed were adjusted to ensure that -the coating compositions had the`same solids content ~; and proportions of ingredients. The results are shown in Table 1. In all cases adhesion, as assessed by both methods, was adsquate.
Similar results were obtained using the polyether-sulphone of repeat unit ~O~.C(CH3)2~0~S02 . .,-, ...
:.;
J, . , . 1081884 :.
`~ - 16 - .
.~ .
s in place of that of repeat unit ~30~3so2- , :- ,,, ~ EXAMPLE 11 `~ A polytetrafluoroethylene containing dispersion was made up as in Example 1 but using the potassium ¦ salt of 4-(4-chlorophenylsulphonyl)ph.enol (37.5 g) ..
dissolved in water (104.5 g) in place of the 142 g of , polyethersulphone dispersion. .. ~:.
The results are shown in Table 1. The adhesion.was .
10 satisfactory as measured by ths adhesive tape test but ~.
on~the thumbnail test the adhesion was inferior to that of the coatings of Examples .1 to 10. : .
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1 . ~ tr~ ~ ~ Ul m o 1~ o C~ Q O 111 :: .
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^ ~ .rl al ~ o a Lq Q Q Q b4 I, tlO h N O lD O ~ ~ :1 ~O c) 1~ Q: Q W >~
C 7 tr) ~ ~ N N N ~-- ~ ~ ~ I 0 0 ~ C
~ D ;t N ~r~ ~ 3 ,~ ~c ~_ } ~ ;: _I _ ~ E I . .
. ~ O ~ N
~ ~1) * ~ c bO b~
~D C * * ~ ~
c o t~ Irl co ~ ~ tD 11'1 0 aD ~r) O ~ ~ ~
1 ~ ~ ~ ~ ~ tr) N N ~ ~ ~ O O * ~ C 0 Ill 0 1: 0~ Q 1~ . . . . * c O ~ C c E
>,~1 oooooooooo* .,~O~ ~
i ~ ` o 0 C ~ C ~ ~ 0 t~ 0 0 ~C >` >' ~
. . Q~ O O O O
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1081884 P 2ao77 : ' .
. . .
: EXAMPLE 12 .
A dispersion similar to that of Example 7 ~poly-ethersulphone RV 0 15) was made but using an aqueous polytetrafluoroethylene dispersion ('Fluon' GP1) in ; 5 place of the lubricant powder ('Fluon' L171) The j amount of the polytetrafluoroethylene dispersion e~ployed (which contained 60% by weight of polytetrafluoroethylene ~ and 6% by weight of a non-ionic surfactant and was made ~ -r by polymerisation of tetrafluoroethylens in an aqueous medium in the presence of a perfluorinated emulsifier , followed by concentration) was such as to give a poly-tetrafluoroethylene/polyethersulphone weight ratio of ' 1:2.
Aluminium plates were coated using the-above mixture and the conditions employed in ths preceding Examples.
The coating, of thicknsss 10 ~m, was continuous having a slightly misty appearance and adequate adhesion. `
By way of comparison Example 12 was repeated but, in place of the polyethersulphone of RV 0.15, a hydroxy ended polyethersulphone (1.02 OH groups per 100 polymer repeat units) of RV 0.49 was used. The ball milling timo to give a polyethersulphone dispersion of average particle size 14 ~m was 16~ hours.
The coating was discontinuous and also failed the thumbnail adhesion test, bsing scraped off on the first scratch with ths thumbnail.
EX~MpLES 14 TO 19 ` Example 7 was repeated but using different proportions of the polyethersulphone of RV 0,15 so that the dispersions had tetrafluoroethylene polymer/polyethersulphone weight ratios ranging from 0.5:1 to 2:1. The curing times were increased to 15 minutes at aoc and 15 minutes at 400C.
The results are shown in Table 2.
' '.
.
....
~, . " , ., . , . . ~
108~U34 P Z8077 : 19 '~:
,':
` TA~LE 2 ~rookfield Appearance , Example PTFE/polyether- Viscosity (CP) (under 50X
sulphone ratio at 30 rpm magnification) 14 0.5:1 536 Good 1:1 764 Good 16 1,21:1 593 Good 17 1.4~:1 693 porous 1~ 1,73:1 767 Porous 19 2:1 550 Porous 1 . .~
The adhesion of ths coatings of Examples 1~ and 19 was slightly inferior ton the thumbnail test) to that of Examples 14 to 17. The adhe~ion of all the coatings as ~ `
assessed by the adhesive tape test was satisfactory.
; EXAMPLES 20 T0 2Z
By way of comparison dispersions similar to those of Exampl~ 7 were made but using a polyphenylene sulphide t'Ryton' V1 sold by Phillips Petroleum Company) in place of the polyethersulphone. The milling time, to average particle size 13 ~m~was 18 hours. Dispersions were made with varying tetrafluoroethylene polymer/polyphenylene sulphide ratios.
Aluminium plates were coated with ths dispersions using the conditions adopted in the previous Examples.
The coatings were continuous but had poor adhesion as --shown in Table 3.
~ , ' .
~ ' . .
Polytetrafluoroethylene/ Adhesion Example polyphenylene sulphide woght ratio ¦ AdTnpu ¦ThtmbtaiII ~ ;
1:1 Fail Fail 21 1:2Borderline Fail 22 1:3 Adequate Fail .
' ' . ~' ~'' ''' .
. , " .
.
. . . ~ ~,. ,., , ~
Claims (18)
1. A coating dispersion comprising a tetrafluoro-ethylene polymer, which is polytetrafluoroethylene or a co-polymer of tetrafluoroethylene with up to 5% of a comonomer, dispersed in an inert diluent containing a thermoplastic arom-atic polyethersulphone of reduced viscosity below 0,25 (as measured at 25°C on a solution of the polymer in dimethyl formamide containing 1 g of polymer in 100 cm3 of solution), or the precursor to such a polyethersulphone, dissolved or dispersed therein.
2. A dispersion according to Claim 1 wherein the polyethersulphone is a preformed polymer.
3. A dispersion according to Claim 2 wherein the polyethersulphone has alkoxy end groups containing 1 to 4 carbon atoms.
4. A dispersion according to Claim 2 in which the polyethersulphone has the repeat unit:
5. A dispersion according to Claim 2 in which the polyethersulphone has the repeat unit:
6. A dispersion according to Claim 2 in which the polyethersulphone has a reduced viscosity within the range 0.03 to 0,2.
7. A dispersion according to Claim 1 wherein the dispersion has a tetrafluoroethylene polymer/polyethersulphone (or precursor thereto) weight ratio between 9:1 and 1:9.
8. A dispersion according to Claim 7 wherein the dispersion has a tetrafluoroethylene polymer/polyethersulphone (or precursor thereto) weight ratio between 0.9:1 and 1.4:1.
9. A dispersion according to Claim 1 wherein the inert diluent is water.
10. A dispersion according to Claim 9 wherein the polyethersulphone has a particle size (as measured by a Micromerograph) of less than 25 µm.
11. A dispersion according to Claim 1 wherein the tetrafluoroethylene polymer is a lubricant grade polytetra-fluoroethylene.
12. A dispersion according to Claim 1 containing a combined content of tetrafluoroethylene and polyethersulphone of 20 to 50% by weight of the dispersion.
13. A dispersion according to Claim 1 containing 1 to 10% by weight of titanium dioxide, based on the weight of the dispersion.
14. A method of coating a substrate comprising applying a dispersion of a tetrafluoroethylene polymer, which is polytetrafluoroethylene or a copolymer of tetrafluoro-ethylene with up to 5% of a comonomer, dispersed in an inert diluent containing a thermoplastic aromatic polyethersulphone of reduced viscosity below 0.25 (as measured at 25°C on a solution of the polymer in dimethyl formamide containing 1 g of the polymer in 100 cm3 of solution), or the precursor to such a polyethersulphone, dissolved or dispersed therein to the substrate and then removing the inert diluent, and there-after curing the coating at a temperature within the range 300 to 450°C.
15. A method according to Claim 14 wherein the coating is cured at a temperature above 350°C.
16. A method according to Claim 14 wherein the coating is cured at a temperature between 380 and 400°C.
17. A method according to Claim 14 wherein the substrate is a metal.
18. A method according to Claim 14 wherein the substrate is a fabric.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB31709/75A GB1537851A (en) | 1975-07-29 | 1975-07-29 | Coating compositions |
| GB31709/75 | 1975-07-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1081884A true CA1081884A (en) | 1980-07-15 |
Family
ID=10327237
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA258,111A Expired CA1081884A (en) | 1975-07-29 | 1976-07-29 | Tetrafluoroethylene polymer aromatic polyethersulphone coating compositions |
Country Status (13)
| Country | Link |
|---|---|
| US (1) | US4090993A (en) |
| JP (1) | JPS5216535A (en) |
| AU (1) | AU502262B2 (en) |
| BE (1) | BE844676A (en) |
| CA (1) | CA1081884A (en) |
| CH (1) | CH606360A5 (en) |
| DE (1) | DE2633940C3 (en) |
| ES (1) | ES450273A1 (en) |
| FR (1) | FR2319696A1 (en) |
| GB (1) | GB1537851A (en) |
| HK (1) | HK50579A (en) |
| IT (1) | IT1064758B (en) |
| NL (1) | NL7608368A (en) |
Families Citing this family (42)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1031094A (en) * | 1973-11-19 | 1978-05-09 | Imperial Chemical Industries Limited | Polysulphone-fluorocarbon coating compositions |
| AU507930B2 (en) * | 1977-01-25 | 1980-03-06 | Ici Ltd. | Coating with polytetrafluoroethylene-polyethersulphone composition |
| AU3230778A (en) * | 1977-01-25 | 1979-07-19 | Ici Ltd | Aromatic polyethersulphones |
| US4191811A (en) * | 1977-03-01 | 1980-03-04 | Ionics, Incorported | Ion exchange membranes based upon polyphenylene sulfide and fluorocarbon polymeric binder |
| JPS5492251U (en) * | 1977-12-14 | 1979-06-29 | ||
| EP0004136A1 (en) * | 1978-02-28 | 1979-09-19 | Imperial Chemical Industries Plc | Aromatic polyethersulphones, their preparation, dispersions thereof and their use as adhesives and coatings |
| EP0032630A1 (en) * | 1980-01-21 | 1981-07-29 | Imperial Chemical Industries Plc | Production of aqueous dispersion of aromatic polyethersulphone |
| JPS58160353A (en) * | 1982-03-16 | 1983-09-22 | Sumitomo Chem Co Ltd | Resin composition |
| EP0100889B1 (en) * | 1982-07-20 | 1986-09-24 | Hoechst Aktiengesellschaft | Primer for coatings containing fluorocarbon polymers with an amount of poly(arylene sulfide) resin, aromatic polyether sulfone resin or aromatic polyether ketone resin, and use thereof |
| FR2535332B1 (en) * | 1982-11-03 | 1986-09-26 | Electricite De France | POLYMER ALLOY, ITS PREPARATION AND ITS APPLICATION TO THE MANUFACTURE OF ELECTROCHEMICAL REACTOR ELEMENTS |
| DE3244714A1 (en) * | 1982-12-03 | 1984-06-07 | Glyco-Metall-Werke Daelen & Loos Gmbh, 6200 Wiesbaden | Process for the preparation of a composite layered material having a polysulphone-based matrix in the functional layer |
| US4503168A (en) * | 1983-05-25 | 1985-03-05 | Union Carbide Corporation | Cookware made from polyarylethersulfone |
| JPS60155430U (en) * | 1985-01-17 | 1985-10-16 | シャープ株式会社 | heating cooker |
| JPS61111352A (en) * | 1985-10-14 | 1986-05-29 | Daikin Ind Ltd | Composition for coating fluororesin |
| US4800661A (en) * | 1986-05-20 | 1989-01-31 | Toshiba Heating Appliances Co., Ltd. | Electric iron |
| US5536583A (en) * | 1986-07-01 | 1996-07-16 | Edlon Products, Inc. | Polymer metal bonded composite and method of producing same |
| AR244295A1 (en) * | 1986-07-01 | 1993-10-29 | Eldon Products Inc | Polymer-metal bonded composite and method of producing same |
| US4897439A (en) * | 1986-07-01 | 1990-01-30 | Edlon Products, Inc. | Polymer-metal bonded composite and method of producing same |
| US5093403A (en) * | 1986-07-01 | 1992-03-03 | Edlon Products, Inc. | Polymer-metal bonded composite and method of producing same |
| DE3715543A1 (en) * | 1987-04-07 | 1988-10-27 | Bayer Ag | POWDER COMPOSITIONS BASED ON POLYARYL SULFIDES |
| JPH0245546A (en) * | 1988-08-05 | 1990-02-15 | Mitsui Toatsu Chem Inc | Non-tacky heat-resistant coating composition |
| US5079073A (en) * | 1989-08-21 | 1992-01-07 | E. I. Du Pont De Nemours And Company | Non-stick coating system with thin undercoat of polyamide imide |
| US5071695A (en) * | 1989-08-21 | 1991-12-10 | E. I. Du Pont De Nemours And Company | Non-stick coating system with two thin undercoats, the first being polysiloxane |
| US5049437A (en) * | 1989-08-21 | 1991-09-17 | E. I. Du Pont De Nemours And Company | Non-stick coating system with thin undercoat of polyether sulfone |
| US5223343A (en) * | 1990-12-12 | 1993-06-29 | E. I. Du Pont De Nemours And Company | Non-stick coating system with high and low melt viscosity PTFE for concentration gradient |
| JPH04111925U (en) * | 1991-03-18 | 1992-09-29 | エヌテイエヌ株式会社 | torque limiter |
| IT1265451B1 (en) * | 1993-12-27 | 1996-11-22 | Lambda Srl | WATER-BASED PAINTS APPLICABLE BY ROLLER FOR THE NON-STICK COATING OF ALUMINUM POTS AND PROCEDURE FOR THEIR APPLICATION |
| GB9418682D0 (en) * | 1994-09-16 | 1994-11-02 | Smith & Nephew | Elastomeric articles |
| GB9418688D0 (en) * | 1994-09-16 | 1994-11-02 | Smith & Nephew | Elastomeric articles |
| GB9418684D0 (en) * | 1994-09-16 | 1994-11-02 | Smith & Nephew | Elastomeric articles |
| GB9500828D0 (en) * | 1995-01-17 | 1995-03-08 | Smith & Nephew | Elastomeric articles |
| US6228932B1 (en) * | 1997-12-22 | 2001-05-08 | Dupont Mitsui Fluorochemicals | Fluororesin powder liquid dispersion capable of forming thick coatings |
| US7026036B2 (en) | 2000-08-17 | 2006-04-11 | Whitford Corporation | Single coat non-stick coating system and articles coated with same |
| US6846570B2 (en) * | 2000-08-17 | 2005-01-25 | Whitford Corporation | Multiple coat non-stick coating system and articles coated with same |
| JP4268344B2 (en) * | 2001-04-12 | 2009-05-27 | Ｊｆｅスチール株式会社 | Electrical steel sheet with insulating coating that is excellent in workability |
| ITMI20020403A1 (en) * | 2002-02-28 | 2003-08-28 | Ausimont Spa | PTFE BASED WATER DISPERSIONS |
| EP1605012A1 (en) * | 2004-06-10 | 2005-12-14 | SOLVAY (Société Anonyme) | Fluoropolymer tape, article comprising a fluoropolymer tape and process for manufacturing a fluoropolymer tape |
| US7147634B2 (en) | 2005-05-12 | 2006-12-12 | Orion Industries, Ltd. | Electrosurgical electrode and method of manufacturing same |
| US8814861B2 (en) | 2005-05-12 | 2014-08-26 | Innovatech, Llc | Electrosurgical electrode and method of manufacturing same |
| WO2009052163A2 (en) * | 2007-10-15 | 2009-04-23 | Advanced Flexible Composites, Inc. | Crosslinkable fluoropolymer composition and uses thereof |
| KR101104680B1 (en) * | 2009-07-23 | 2012-01-13 | (주) 더몰론코리아 | Porcelain enamel heat-cooker having non stick ceramic coating layer |
| CN113528003B (en) * | 2021-08-06 | 2022-06-07 | 浙江鹏孚隆新材料有限公司 | Low-VOC organic-solvent-free heat-resistant water-based paint and high-temperature-resistant corrosion-resistant coating prepared from same |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3993843A (en) * | 1973-03-13 | 1976-11-23 | E. I. Du Pont De Nemours And Company | Aqueous dispersion of aromatic polysulfone resin with perfluorocarbon resin, and coated articles |
| US3992347A (en) * | 1973-06-29 | 1976-11-16 | E. I. Du Pont De Nemours & Co. | Arloxysulfone copolymer solution having perfluoro-carbon polymer particles dispersed therein |
| CA1031094A (en) * | 1973-11-19 | 1978-05-09 | Imperial Chemical Industries Limited | Polysulphone-fluorocarbon coating compositions |
-
1975
- 1975-07-29 GB GB31709/75A patent/GB1537851A/en not_active Expired
-
1976
- 1976-07-22 US US05/707,766 patent/US4090993A/en not_active Expired - Lifetime
- 1976-07-26 AU AU16250/76A patent/AU502262B2/en not_active Expired
- 1976-07-28 DE DE2633940A patent/DE2633940C3/en not_active Expired
- 1976-07-28 NL NL7608368A patent/NL7608368A/en unknown
- 1976-07-29 JP JP51089763A patent/JPS5216535A/en active Granted
- 1976-07-29 ES ES450273A patent/ES450273A1/en not_active Expired
- 1976-07-29 IT IT7625819A patent/IT1064758B/en active
- 1976-07-29 FR FR7623169A patent/FR2319696A1/en active Granted
- 1976-07-29 CA CA258,111A patent/CA1081884A/en not_active Expired
- 1976-07-29 BE BE169375A patent/BE844676A/en not_active IP Right Cessation
- 1976-07-29 CH CH972676A patent/CH606360A5/xx not_active IP Right Cessation
-
1979
- 1979-07-26 HK HK505/79A patent/HK50579A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5216535A (en) | 1977-02-07 |
| US4090993A (en) | 1978-05-23 |
| ES450273A1 (en) | 1977-10-01 |
| NL7608368A (en) | 1977-02-01 |
| AU1625076A (en) | 1978-02-02 |
| HK50579A (en) | 1979-08-03 |
| CH606360A5 (en) | 1978-10-31 |
| DE2633940A1 (en) | 1977-02-03 |
| FR2319696A1 (en) | 1977-02-25 |
| FR2319696B1 (en) | 1979-09-28 |
| BE844676A (en) | 1977-01-31 |
| DE2633940C3 (en) | 1981-11-05 |
| IT1064758B (en) | 1985-02-25 |
| AU502262B2 (en) | 1979-07-19 |
| GB1537851A (en) | 1979-01-04 |
| JPS5334134B2 (en) | 1978-09-19 |
| DE2633940B2 (en) | 1981-02-12 |
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