CA1046360A - Fluorocarbon polymer compositions - Google Patents

Abstract

FLUOROCARBON POLYMER COMPOSITIONS

ABSTRACT OF THE DISCLOSURE

Coating compositions containing (a) a fluorocarbon polymer and (b) a polymer which depolymerizes, and whose depolymerization products vaporize, at the fluorocarbon polymer fusion temperature, when applied to cookware, give films with greater density and less porosity than conventional compositions.

Description

BACKGROUND OF THE INVENTION

Cookware coated with fluorocarbon polymers of various sorts has come into widespread use in recent years. Almost e~ery housewife prefers to use such cook-ware in her kitchen because food is less likely to stick to it and because it is 80 easy to clean.
It has now been round, according to this lnvention, that the fluorocarbon polymer film which coats such cookware can be made denser and less porous than it was previously, and that this makes the product still easier to clean and improves its appearance by making the fllm glossier.

: .
, -~, -..
~; ' ' , -'``~ . :-"
.: .:
': 3~ , '.' ,:

... . .

- 2 -,.~ ,., .-SUMMARY OF THE INVENTION

One can get these advantages by using, lnsteadof the customary fluorocarbon polymer cookware enamel, a compositlon whlch contains as lts principal ingredients a fluorocarbon polymer, a polymeric ad~unct having specific physical properties, and a liquid carrier.
The fluorocarbon polymers used ln this composi-tlon are those of hydrocarbon monomers completely substltuted with fluorlne atoms or a combination of fluorine atoms and chlorlne atoms. Included in this group are polytetrarluoroethylene ( ~ 3, copolymers Or tetrafluoro-ethylene and hexa~luoropropylene in all monomer unit weight ratlos (FEP) and fluorochlorocarbon polymers such as polymonochlorotrifluoroethylene. PTFE 18 preferred because o~ the excellence of the products it gives.
The iluorocarbon polymers used are particulate.
For best results, ~he partlcles should be small enough to pass through the nozzle Or a spray gun without clogglng lt and al~o small enough to give the resultlng fllm integrlty.
~ 20 In most cases thls means the partlcles should be no larger ¦ than about 0.35 mlcronl in the longest dlmension.
r The rluorocarbon polymer 18 ordlnarlly present ln the composltion at a concentratlon of about 25% to about ` 95% (by welght) of the total Or fluorocarbon polymer and ~ ad~unct polymer sollds, preferably about 85% to about 95%, j- even more prererably about 85~ to about 89%.
~ , , ' .
`: _ 1. Neasured optlcally agalnst a ~tandard.

.,,~` ~
~ .

- 3 -l. . . ` - :
.', . ~ . ~ 1 Broadly ~peaking, the polymeric ad~unct can be any polymer or copolymer (in the sense of being compo~ed o~
two or more types of monomers) of monoethylenlcally unsaturated monomers whlch depolymerlzes, and whose depolymerlzation products vaporlze, ln the temperature range of from about 150C. below the fusion temperature o~ the fluorocarbon polymer used to about the fluorocarbon polymer'~
decomposltiQn temperature. The closer the depolymerization and vaporizatlon temperatures are to the fluorocarbon's ;~
fuslon temperature, the better. ~-"Depolymerization" means degradation of the polymer to the point at whlch the degradatlon products are ~olatlle at the temperatures encountered in curing the ~ilm. These degradatlon products can be monomers, dimers or oligomers.
"Vaporlze" means volatilizatlon Or the degradation products and thelr e~aporation from the rllm. Ideally, all Or the degradation products pass ~rom the ~ilm, but a~ a ~; practical matterJ a ~mall but inslgnlricant amount generally remains. - ' ~, Illustrati~e o~ the polymeric ad~uncts which can be usod are polymera Or monoethylenically un~aturated monomers which contain one or more monoethylenically unsaturated acld units.
~ . .
Representative o~ these monoethylenically nsaturated monomers are alkyl acrylates and methacrylates ha~ing 1-8 carbon atoms in the alkyl group, styrene, -meth~l styrene, vinyl toluene and glycidyl esters o~
c~arbon atoms. Representatl~e of the monoethylenica~ly nsaturated~'aoids are~aorylic acid, methaaryl~c acld, ~........................................ .

;, ...................................... . .
.: ~

4 - : :

,. . . .. ... .-.~ . ; . . . . . , . : . ... : . . .

~04~3~0 fumaric ac~d, itaconic acid and malelc acid (or anhydride).
Alkyl acrylates and methacrylates and acryllc- and methacrylic acids are preferred ~or the density and glo~s Or the finlshes obtained when they are used.
The preferred glycldyl ester unit is one derived from a product ~old by the Shell Chemical Company as CARDURA E* ester. This i8 a mixed ester of the general formula ~0~ n /Rl ~-H2C - C~ - CH2 - O - C - C~ R2 ~here R ~ CH

and ~ and R3 are lowcr alkyl groups, Rl, R2 and R3 contain~ng a total of 7-9 carbon atoms.

Repre~entatlve Or these monoethylenlcally j~`` unsaturated monom-rs are alkyl acrylates and methacrylates having 1-8 carbon atoms ln tho alkyl group, styrene, ormethyl ~tyrene, vinyl toluene and glycldyl esters Or *denote6 trade mark ~ .

- 5 -~A~

- ~. . . . .

- ~046360 4-14 carbon atoms. Prererred for the density and glo86 Or the finishes obtained when they are u~ed are the alkyl acrylate~, alkyl methacrylate6 and a glycidyl ester sold by Shell Chemical Company a~ CARDURA E ester, whlch i~
a mlxed e~ter of the general formula O O R

H2C - CH - CH2 - O - C - C \ R2 ~here Rl 1~ CH

and R2 and R3 are lower alkyl groups, Rl, ~ and R3 contalnlng a total Or 7-9 carbon atoms.

Repre-entatlv- Or the monoethylenically un~aturat-d acld~ are acryllc acid, methacrylic acid, rumarlc acld, ltaconlc acld and malelc acld (or anhydrlde).
Acrylic acid and methacrylic acid are pre~erred.
The polymerlc adJunct~ especlally preferred ~or u~e are ~,:

~046360 1 methyl methacrylate/2-ethylhexyl acrylate/
methacrylic ~cid terpolymers, prerer~bly the 40-50/48-52/1-4 (weight ratio) terpolymers;
2. butyl acrylate/methyl methacrylate/CARW RA E/
acryllc acld, qu~dripolymers, preierably the 23-27/33-37/21-25/15-19 quadripolymers;
3. styrenc/methyl methacrylate/CARDURA E/
acrylic acld quadrlpolymer~, prerer~bly the 28-32/ 8-32/21-25/15-19 quadripolymer6;
4 mcthyl ~ethacrylate/ethyl acrylate/methacrylic acid terpolymers, preferably the 37-41/55-59/ ~ :
1-6 terpolymers Th~ polymeric adJuact i8 ordlnarily pre~ent in t~e co~po~ltiQn at a concentration or rrom about ~ through about 75% (by ~eight) o~ the total Or rluorocarbon poly~er and adJunct pol ~ er ~olids, preferably about 5% through about 15%, ~:
ev-n ~ore pr-rerably ~bout 11% through 15%
m e~- poly~erlc adJu~ct~ can be ~d- by any of thc conventlonal ~re--radical technigues ramlliar to any poly~-r che~l~t The carrlor used in the compo~ltlon can bo any or those normally us-d in compoJlt`10ns Or this type It i8 an ln rt, not a reactive or function~l (in the ~en~e Or contrlbuting to the working o~ tho invention) co~ponent and lts naturo ~8 thercrore, gen-r lly spcaklng, Or ~econdary i~lportallco. me carrier s-r~-s o~ly to k-ep the compo~ition honog~eou~J asd acts a~ a ~-chanis~ ~or conv-ylng the ~olid co~pol~ts to t~e Jubstrate. Arter a coating ha8 be~

, ,' - 7 - ~

: ,:
~A~ ` -, ~. ...

104~3~;0 deposited, the carrier evaporate~. It i~ nece~Rary, therefore, only that it be compatible with the other components Or the composition and that it have no adverse ef~eets on the coating itself.
Commonly, the lluorocarbon polymer used in the eomposition i8 provlded in the ~orm Or an aqueous dispersion, and the water introduced into the co~posltion with the polymer also serves a8 the carrier for the composition.
Organic liquid~ ~uch as ethanol, iRopropanol, acetone and the CELLOSOLVE~ solvents ean also be used as carrlers.
m e composition ean also eontain sueh eonventional addltives as pigments, rillers, f}0~ eontrol agents, pla~ticlzers, etc., as seem neeessary or desirable. The~e additives are added for the u~ual reasons, in the usual ways and in the ueual amounts.
The composition is made by flr6t ehoo6ing the fluoroearbon polymer, polymer adJunet, liquid earrier and ~ ,... .
~uch conventional additives a~ may be used, and the amount~ of these best suited to the purpo~e. Thls ean be done ~lth no trouble by one skilled in this art. Prepara-tion Or the eomposition is then a simple matter Or thoroughly mixing the~e eomponent~.
The eomposition will be most userul for topeoatlng metal eookware, e~peeially rrypans, but ean be used ~u~t as ~ell on other metal artieles requiring lubrielous surraees, sueh as bearings, valves, wire, metal roll, bQilers, pipe~, ship botto~s, oven llner~, iron soleplates, war~le irons, iee eube trays, sno~ shov~ls and plow~, ehutes, eonveyors, dies, tools ~ueh as sa~, rile~ and drills, hoppers and . .:, "
~denotes trade ~ark t~A ''' ~'.

~ . . . . . ... . . - ~. . , . -- -104~3~;0 other indu~trial containers and molds.
The composition can be applied in ang of the u~ual ways. Spraying, roller-coating, dlpping, doctor-blading --all are suitable, although spraying iB generally the method Or choice. m e artlcle to be coated 18 preferably pre-treated by grit-blasting, bg the rlame-spraying of metals or by rrit-coating. m e artlcle i~ thcn primed with a composltion co~prising a fluoropolymer, a liquid carrier and either (1) a combination o~ (a) phosphoric acid and (b) colloidal aluminum oxide, boron oxlde or aluminum phosphate, a~ is disclosed in U.S. Patent 3,489,595; (2) an alkyl silicate ~hose alkyl group contains 1-5 carbon atom~, as i~ disclosed in U.S. Patent 3,644,260; ~3) alu~inum borophosphate, as 1~ disclosed in U.S. Patent 3,644,261, (4) colloldal silica, a8 iB dlsclo~ed in U.S. Patent 3,655,604 and Belglan Patent 820 968, granted April 11, 1975, or (5) lithlum polysilicate, a~ is disclosed in U.S. Patent 3,694,392. The preparatioA and application Or such prlmer co~posltion6 are de~¢rlbed in greater detall in the aror-~ontloned reforence~.
m e composition i~ prererably applied to a thlc~ness Or about 10 to 125 microns (dry) ana then cured ror rro~ 0.5 to 30 ~inutes at a temperature Or ~rom 370 to 460C.
ESCRIPTION OF THE PREFERRED EM~ODDME~TS
Those skilled in this art ~$11 be able to practlce thl~ invention more easll~ b~ rirst rererring to the ~olIo~ing illustratlve exa~ples. The~e arti~ans, will, no d~ubt, be able to co~pose nu~erous variations on the theme disclosed, such a~ chaa~ing the a~ount~ Or ingredient~ sl~ghtlr but iasigniricantly rrO~ tho~e ~ho~n, addlng innocuous substances, or ~ub~tituting equivalent or nearly equivalent co~ponents ror tho~e sho~n. All these variations are considered to be part o~ the ~nv~ntlve concept.
In the~e exa~ple~, all parts and percentages are by ~eight.

_ g _ .. , . - . -. . .. ..

.
A representative coating compositlon of the invention is made as follows (all parts are by weight):

(1) Mlx together PTFE disperslon aqueous, 60% solids411 parts Water 72 part~

(2) Separately mix Triethanolamine 12 parts Oleic acid 6 parts Toluene 40.2 parts Butyl carbltol 7.2 parts ~3) Prepare a mill base by mixing and then pebble milling Water 67 parts Channel black 20 part~
Sodlum polynapthalene-sulfonate 3 parts Alumlnum silicate 10 parts , ~ .
.~.. i ~ . ...
Thoroughly mix (1) and (2). Then add to this mlxt~re, with stirrlng, 90 parts o~ an aqueous dispersion, 4 ~ solids~ of a methyl methacrylate/ethyl acrylate/
mebhacrylic acid 39/57/4 (welght ratio) terpolymer. Then blend 37.2 parts of (3) into this mixture, with stirring.
Spray the result$ng composition to frit-coated aluminum p~n, primed with a primer o~ the type ~hown in U.S. Patent 3~694,392, to a thic~ness o~ 20-25 micron~ (dry). Then bake the pan for 5 minutes at 430C. The re~ultlng finish will be glo~y and dense.
, . . .
: , ~

- . . i .

10463~0 Repeat Example 1, except in place of the prlmer of U.S. Patent 3,694,392, u~e one m~de as follows:

(1) Mlx together PTP~ dlopersion aqueou~, 60% solids 478.76 parts Delonized water 130.23 part~ c-Colloidal silica 801l 30~ solids in water 327.18 parts (2) Separ~tely mix TRITON X-100*
(non-lonic surractant sold by Rohm & Haas Co.)17.52 parts Toluene 34.56 parts Butyl carbitol 13.36 parts Sillcone (Do~-Cornlng DC-801*, 60~ solid~ ln xylene)34.56 parts Add 85.52 parts Or (2) to (1) in a 8~all str~am o~er a 2-3 ~inute perlod, ~lth stirring. Then a~d, wlth stlrring, ~ . .
TiO2 (45f ~olid~ in wAter) 35.46 part~
~nd Channel black (22% ~olid~ in water) o.85 parts Continue ~tlrring ror 10-20 mlnutes.
Spray this compositlon OA the ~rit-coated aluminu~
pan of ~xamplo 1 to a thlck~ess Or 5-15 mlcrons (dry) and alr dr~ it. :

.
1. LUDOX A~ oollQidal silica, stabll~zea w~th sodium ion~, :
sold by E. I. du Po~t de ~emour~ and Company.

~d0notes trade ~ark .''.

h~
. . :
.

. - - -~. . - , ~

Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An article bearing (A) a cured primer coating derived from a composition comprising a fluoropolymer, a liquid carrier and matter selected from the group consisting of (1) a combination of (a) phosphoric acid and (b) colloidal aluminum oxide, boron oxide or aluminum phosphate;
(2) an alkyl silicate whose alkyl group contains 1-5 carbon atoms; and (3) aluminum borophosphate, overlaid with (B) a cured topcoat derived from a composition comprising (i) about 25% to about 95%, by weight of the total of (i) and (ii) solids, of a polymer of hydrocarbon monomers completely substituted with fluorine atoms or a combination of fluorine atoms and chlorine atoms, (ii) 5-75% by weight of the total of (i) and (ii) solids, of a polymer of monoethylenically unsaturated monomers, which depolymerizes, and whose depolymerization products vaporize, in the temperature range of about 150°C. below the fusion temperature of the fluorocarbon polymer used to about the fluorocarbon polymer's decomposition temperature, and (iii) a liquid carrier.

2. The article of Claim 1 wherein the polymer in (ii) contains one or more monoethylenically unsaturated acid units.

3. The article of Claim 2, wherein the polymer contains monoethylenically unsaturated monomers selected from the group consisting of an alkyl acrylate or methacrylate having 1-8 carbon atoms in the alkyl group, styrene, .alpha.-methyl styrene, vinyl toluene and a glycidyl ester, and mixtures thereof, and the acid unit is selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid and maleic anhydride, and mixtures thereof.

4. The article of Claim 3, wherein the polymer is a methyl methacrylate/2-ethylhexyl acrylate/methacrylic acid terpolymer.

5. The article of Claim 3, wherein the polymer is a butyl acrylate/methyl methacrylate/ester/acrylic acid quadripolymer, where said ester is wherein the R1, R2 and R3 groups are saturated aliphatic chains which contain a total of 7 to 9 carbon atoms, and at least one of R1, R2 and R3 is a methyl group.

6. The article of Claim 3, wherein the polymer is a styrene/methyl methacrylate/ester/acrylic acid quadripolymer, where said ester is wherein the R1, R2 and R3 groups are saturated aliphatic chains which contain a total of 7 to 9 carbon atoms, and at least one of R1, R2 and R3 is a methyl group.

7. The article of Claim 3, wherein the polymer is a methyl methacrylate/ethyl acrylate/methacrylic acid terpolymer.

8. The article of Claim 1 where in (A) and (B) (i) the polymer is polytetrafluoroethylene.

9. The article of Claim 2 where in (A) and (B) (i) the polymer is polytetrafluoroethylene.

10. The article of Claim 3 where in (A) and (B) (i) the polymer is polytetrafluoroethylene.

11. The article of Claim 4 where in (A) and (B) (i) the polymer is polytetrafluoroethylene.

12. The article of Claim 5 where in (A) and (B) (i) the polymer is polytetrafluoroethylene.

13. The article of Claim 6 where in (A) and (B) (i) the polymer is polytetrafluoroethylene.

14. The article of Claim 7 where in (A) and (B) (i) the polymer is polytetrafluoroethylene.

15. The article of Claim 8 where in (A) and (B) (i) the polymer is polytetrafluoroethylene.