LAQUES A BASE DE FLUOROPOLYMERES RESISTANT MIEUX AUX EGRATIGNURES

FLUOROPOLYMER FINISHES HAVING IMPROVED SCRATCH RESISTANCE

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
Compositions containing
(a) fluoropolymer,
(b) mica particles, mica particles coated
with pigment, or metal flake,
(c) a polymer of ethylencially unsaturated
monomers and
(d) a liquid carrier
are useful for coating metal, especially cookware, to give
lubricious surfaces.
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Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A coating composition consisting essentially of
(a) about 80-99.8% by weight of the total of (a)
and (b), of a particulate polymer of one or
more monoethylenically unsaturated hydrocarbon
monomers completely substituted with fluorine
atoms or a combination of fluorine atoms and
chlorine atoms;
(b) about 0.2-20%, by weight of the total of (a)
and (b), of mica particles, mica particles
coated with pigment or metal flake;
the total of (a) and (b) equaling 100%;
(c) about 2-300%, by weight of (a), of one or more
polymers of monoethylenically unsaturated monomers
which depolymerize and whose depolymerization
products vaporize in the temperature range of
about 150°C below the fusion temperature of (a)
to about the decomposition temperature of (a);
and
(d) a liquid carrier,
said coating composition being suitable for forming finishes
having improved scratch resistance.
2. The composition of claim 1 in which (b) is
present at a concentration of about 2-15%, by weight of the
total of (a) and (b).
3. The composition of claim 1 in which (b) is
present at a concentration of about 8-12%, by weight of the
total of (a) and (b).
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4. The composition of claim 1 wherein the polymer
in (a) is PTFE.
5. The composition of claim 1 wherein the mica
particles in (b) are coated with an oxide of titanium, zirconium,
aluminum, zinc, antimony, tin, iron, copper, nickel, cobalt,
chromium or vanadium.
6. The composition of claim 1 wherein the polymer
in (c) contains one or more monoethylenically unsaturated
carboxylic acid units.
7. The composition of claim 6 wherein the polymer
in (c) is of one or more of an alkyl acrylate or methacrylate
having 1-8 carbon atoms in the alkyl group, styrene, alpha-
methylstyrene, vinyl toluene and the acid unit is of acrylic
acid, methacrylic acid, fumaric acid, itaconic acid, or maleic
acid, optionally esterified with a glycidyl ester of 4-14 carbon
atoms (total).
8. The composition of claim 1 wherein the polymer
in (c) is
(1) a methyl methacrylate/2-ethylhexl acrylate/
methacrylic acid terpolymer,
(2) a butyl acrylate/methyl methacrylate/acrylic
acid terpolymer esterified with a mixed ester
having the structure
<IMG>
where
R1 is CH3
and
R2 and R3 are lower alkyl groups,
R1, R2 and R3 containing a total
of 7-9 carbon atoms.
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(3) a styrene/methyl methacrylate/acrylic acid
terpolymer esterified with a mixed ester having
the structure
<IMG>
where
R1 is CH3
and
R2 and R3 are lower alkyl groups,
R1, R2 and R3 containing a total
of 7-9 carbon atoms.
or
(4) a methyl methacrylate/ethyl acrylate/methacrylic
acid terpolymer.
9. The composition of claim 1 wherein the carrier
in (d) is water.
10. The composition of claim 1 wherein the polymer
in (a) is PTFE, the mica particles in (b) are coated with
titanium dioxide, the polymer in (c) is a methyl methacrylate/
ethyl acrylate/methacrylic acid terpolymer and the carrier in
(d) is water.

Description

Cookware coated wit~ :~luoropolg~ae~3~ esp~cially
pol~tra~luoxoethylene (PTFE) ~ has csme in~o w~despxead us~
~ re~ent year~ cook~ prefer to u8e~ ~3uch cOOk:~a~8 be-
ca.~e o~ lts non~t~ck propertie~ and becau~e i~ o ~a~y
to cle~.
Nhi:Le cookware o~ thi~ type 13 quit~ d~lrable,, the
fluoropol~mor coal;in~3: t~nas to become ~cratch~d ag~ter ~e~de~
u~e becau~e i~ ~ 80m8Wh~Lt ~o~t~r than the utell~ils u~ed to
10 stir and tur~ the ~o~d in the ware.
~U~ Opl ~E I~ TION
I~ has now been ~ound that th~ scratch res~sta~ce o~
. ~ ~luo~opoly~er coa~ can be ~r~v~. i~ th~ CoD~?~si~ion ~ro~
which t~e ~s:~at~g ~5 der~ed compr~ses
luoxopol~mer~
(~) m~cai p~cle i m:Lca p~icleg coated with
plgme~tg. or metal ~Iak~,
~c) a po~me~ o~ ~onoeth~le~ca~ atuxate~
~on~er~ ~i;ch depo~er~ze~ and ~aporizes
~0 a~ ~out th~ ~luoropolymer~ fusion
temperatlare5,
a~d
(d~ a liquid ca~ri.e~,
Such ~ coating ~:Lso hs~ ~xcelle~ crack re~ista~ce ~d
bl~3~r resi3ta~c~,~ and ha~ a~the~icaIly plea~ing a~pear~n~e..
:~ :
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P$~
~*3~
~ e ~luoropoly~er~ used; in the compo3itions o~ t~e
in~re~tion are homspolymers a~d copolymea~ (meaning the polymer
conta~ two or more d:~fere~ monomer ~t~) o~ monoet~
le~ical:L~ unsatuxate~ h~drocar~o~ mon~mers compl~ y 3ubst~-
tut~ ~th ~luorin~ atom~ or co~pletely ~ubstitu~ed ~ith a
combirlation of ~luorine a~om~ and chlor~n~ atom~. In~_luded in
thi~ group are per:eluorolerin pol~7mers ~uch ~ polytetra:eluoro-
ethyl~n~ a~ copoly~era o~ t~tra~luoroethyle~e ~n~ hexa~laoro-
propylene in all monomer unit we~ght ratio~ ~luorochloxocarbonpolymers uch as polymonochlorotri~luoroethyle~e,. and the
norfflally solid copol~mers of tetr ~luoroethylene and perfluoro-
~lkyl vinyl e~hers (wherein the alkyl ~roup is o~ 1-5 carbon
atom~). M~ture~ of the~e can also be u~e~.. P~FE is pre~erred
~or its thermal stab~l~ty.
~ The ~luoropolymar~u~ed 1~ partlc~late. The p~rtlcle~
ar~ pr~ferabl~ ~ ~ enough to pas~ through the no2æle o~
spr~y g~ wlthou~- clog~ng i~ 2n~ ~re ~l~o ~m~ll e~ough to
g~a the re~ultin~ ~ilm ~te~rit~.
2Q The-Pluoropolym~r p~e~s~a~ly ~a~ ~ ~umher ar~r~ge
molecul~r ~eigh~ o~ ~t l~a~t sbou~ 20~0~ eYe~ more pre~rab~y
~~~lea~ about 2~0~00 ~ b~cau~e su~h ~luoropo1y~ers~~~hax~er
~ini~h~s.. Nu~e~ aYer~e ~olecular ~elg~t o~ P~F~ easurod
: b~ ~h~ethod aesc:~lbe~ by Su~, Tskehl~a &~d Machi ~n Journal
olu~e 179 pp~. 325~-3257 ~lg73)~
The ~u~b~r a~erage~mol uIar weigh~ o~ ~ te~ra~luoroeth~len~
; hexa~luoroprop~lene copoly~er iæ~me~sured by ~rst determinlng
.
i~* mèlt ~lo~r rate (~) accord~ng tQ AST~ D21l6, u~i~ the MFR ~:~
to dete~ni2l~ ;melt ~i~Go3ity (MV) accordl~g to the equation
,

~ 1?~ ;~ pr~3~ur~ u~ed. (mm) ac or~i.c~ radi~
an~ then d~te~l~g moleculaE ~eight (MW) accord~g ~v the
e~uation
\ 3~4/ 3~V
6 ~ lQ ~
~lmiber average mol~cul~ ~reight o~ a ~luo:roch:loroc~r~on poly
m~r 1~ measured by ASTM D1~30..
Although a po~de~ o~ ~luoropslymer can be u~ed ~d
a c~r~er provided Se!!paratel9`3 a polymer in th~ ~O~D o~ an
aqueous dlsp~rsiorl i~ pr~erred ~or i~s s~abllity and b~cau~e
10 it is most eas~r ob~ained ~ that ~rm.
~ he ~luoropolymer is ordillar~ly pr~nt ~ the compo~$-
ti.o~ a~- a concentrat~on G:~ abou~ 80 9~ , pre~rabl5~ about
85-982~ by Me~ o~ ~he total ol~ ~luoropol~mer ~ iC~L parti-
Cl~r mic~ ~ert~cl ~-co~l~c~ ~el- p~gmen~g or ~o~al ~ke.
e 3~ic~ p~lcles.~ 60~edL mica par~icle~- ~d metal
~ke us~ i~ the com~os~tlons o~ the t~entio~ ean b~ an~ Or
. tho~e ~ilable~ comm~rci~ly. The~ partic~s~ e~ ~a
an averag~ 10~Jt di~en~lors o~ lO to l~0 ~rons; pro~erab3~r
15-~0 m~crons~. ~lth no p~ticles or ~ e~ h~ ~ longe~t
20 dinension o~e ~or~ t~ about 200 ~crons~ Partlcle and ~lake
~iz~ ~ m~a~ured o~p~cally ga~ ~ 3tandard..
T`he :m~c~ part~c~e~ coatedt ~rith pi~e~t pre~erred ~or
use are ~hose d~scr~b~d ~ U,S. Pat~t ~,087,827~ to KIenke and
Sbratton~ and U~ Paterlt~ 33087,828 asld~ 3,087,829~ to Iinton~
T~e d~closure~ o~ the~ pat~t~ are lncorporated i~to this
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3p~C :Eication to d~scr~b~ th~ ~rar~ou~ coalte~ ~ic~ ho~
~hey are prepared~ ~
The mlca~ described in thes~ patents are coated
~h o~ des .or hydrou~ oxides of tita~itIm, zir~o~i~, aluminum~
:~inc, ant~ony~ tirl, iron~ copper, ~cl~el, cobalt~ chrom7~m
or Y~rladium. Tltanium dioxide coated mica ls pre~erred
beca~e o~ ~t~ &vai:Lab1lity.. MiX~ !8 oi~ coa~ed mica~ c~
also be u~ed~
Repres~ntati~r~ OI the metal fla~e whi.ch can b2 u3ed
10 are alumlnum ~lake, ~tainl~s ste~ ke,~ nickel fïake and
bronze flake~ cture~ of flake can ~lso be u~ed.
The mica9 coated mi a or metal ~laks i~ ordinar~ly
pre~ent i~ a compo~ition o~ the invention at a concentration
o~ about 0,,2-2~, by weight o~ the t~tal OI ~luoropolymer and
mica~ coated m~c~ or metal ~la~se, pre~erabl~ about 2 15~6, e~en
more pre~era,bly about 8~
T~ polymer o~ morloeth~lenicall~ un~lLrated mono-
mers usea in the compo~ltlon~ o~ th~ e~ltio~ c~ be any
~olymer or copolymer (in th~ ~en~e of bei2lg compo~ed o~ two or
20 more type~s of monomer~) o~ ~thyl~n~cally- uIlsat~r~ed motlomer~
whic~ à~oly~eriæ~ ~d who$~ depol~n~r~zation products Y~por-
~:Z:~3 in the temperatux ~ r~ge o~ ~rom abou~ 150 0C . belo~ the
~ion temper~eure o~ the ~luoropolgmer used to about the
~luoropolymer ' s decompo~ tion t~erature . The closer th~
depo~rmeriæat~on a~d vapQr~za.t~on t~mperature~ are to th~
fluoropolymert~ f~on te~per~ure, the bette~.
'rDepoly~.erization'r m~s d~gradation of th~ polymer
to the polnt at ~hich the degradatio~ products are volat~l~
at ~he t;emp~ratures ~ncountered ~n curing the Ilnal ~llm;
3 T~e~e d~;radatio~ product~ can be mollom~r~9 dim~rs or ollgomer~.
~ 5 --

~5~5
'1Vaporize" means volatilization o~ the degrada~ion
product~ and their evaporation ~rom the film. Ideally, all
o~ the degradation products pass ~rom the film, but as a
practical matter, a small but ins:Lgn~ficant amount generally
remains.
Illustrative o~ the.pol~mers which can be used are
polymers o~ monoethylenically unsatura~ed monomers which con-
tain one or more mono~th~lenically unsaturat~d acid ~lit~.
Representati~ o~ these monoethylenically unsaturated
monomers are alkyl acrylates and methacrylates hav~ng 1-8
carbon atoms ~n the alkyl group, styrene, a-methyl styr~ne,
vinyl toluene and glycldyl esters o~ 4-14 carbon atoms. Re-
presentative of the monoethylenically unsakurated ~cid~ are
acrylic acid, methacrylic acid~ fumaric acid, itaconic acid
and maleic acid (or anhydride), Mixtures of these polymers can
also be used~
Pre~erred ~or the denslt~ a~d g10SB 0~ the ~inishes
obtain~d when ~hey are used are the polymers of alXyl acrylates~
alkyl methacr~lates~ acrylic acid, methacrylic acid and a
glycidyl ester sold by Shell Chemical Company as "Cardura E'
ester, which i~ a mixed ester o~ the general ~ormula
: :
: ~ ~ \ / R~
H2C - CH - C~2 - 0 - C - C - R2
R9
where
Rl i~ CH3
and
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:,
:
~ . . . . - . - .
' ~, ,

JJ~
and ~3 are lo~er alkyl groups 3
Rl, ~ and R3 containing a total o~
7-9 carbon atoms.
The polymers ~pec~ally pre~erred for the ~ame
rea~on~ ar~
1. methyl methacrylate/2-ethylhexyl acryl~te/
methacryllc acid ~erpolymer~, pre~0rably ~h~
40 50/48-52/1-4 (wei~hk ratio) terpolym~r~;
2~ butyl acrylat~/meth~l m~thacrylat~/CARDURA E*/
acryllc acid qu~dripolymers3 pre~rably the
23-27/33-37/21-25/15-19 quadr~polymers;
ætyrene/methyl ~ethacrylate/CA~DURA E/
acr~lic aci~ ~uadrlp~lymers, p~Per~bly the
28-32/~-32/21-25/15-19 quadrlp~lymer~;
4. methyl methacrylate/ethyl acryl~te/methacrylic
;~ acid terpolymers~ pre~erably the 37-41~55-59/1-6
terpol~mer~.
; Such a polymer ~s ordlnarily prese~t in a comp~s~-
- tion ~ the l~vention at a conce~tr~ti~n o~ a~ouk 2-3Q0~ by
weight o~ the ~luoropQlymer, preferabl~ about 5-20%, I~
can be made by any ~ the conventional free-radical techni-
que3 famlllar to any polym~r chemist~ :
~ The carrier used in the co~position o~ the ln~e~tlo~
; ca~ be any o~ ~ho~e normally used 1~ e~mp~sitio~ of this ty~O
It is a~ lnert, n~t a reac~lve or functlon~ the sense of
* denotes trade olark
~ .
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.:~
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contributing to the w~rking c~ the inve~tt on ) component and
it~ nature i~ the~e~ore o~ secondary importance. The carrier
ser~e~ only to keep th~ composition homogerleou~ and a~ts as a
mecha~ or convey~ the ~olid cos~ponent~ to the sub~tr~te.
er a coat~g ha~ been deposited, the carrier e~aporate~.
It i~ nece~ary., there:eore~ only 1;hat lt be compatlble wikh
the other component~ o~ the compo~l;tivn and that it ~ re no
ad~rerse e~ect~ on the coat~g it~eli~
Co~only, the ~luorocar~on pol~mer u~ed in the
10 composit;ion i~ provid~d i21 the ~oxm of` a~ aqu~ous di3persion,
and the wster introduced into th~ compo~ltion wi.th the polymer
also ser~e~ ~s ~11. or as part of the carrler for khe composi-
tion ~ Organic l:iquid~ such as alcohols ~ ketone~, aliphatic
and a~omatic h;ydrocarbons, or mix~ures o~ theseJ ca2l also be
used .,
The composl~ion~ o~ the i~vention c~n ~lso con~ain
such convent~orlal additiv~s a~3~ flow control agen~3. sur-
~cta~t~a~d p:La~tic~zer~ as are nece~sar~r or 3eem de~able~. .
rhese add~t~v~ are added for the usual re~oIl~, in the usu~l
20 ~ ~d in the usu~ aou~s.
The ~mou~t oi~ ~otal solld~ in the coat~g compost-
tions will be gover2~ed by the substPate to wh~ch the compos~;
tlon~ to be applied,, the method o~ appllcation" the curlng
procedura~, a~d like ~actor~ the usual ca e, the composi-
tio~ 1 contain ~bout lO-80%~ by welght, o~ solids,
- The compos~tio~s can be made b~ ~lmply mixing together
appropriate amounts o~ th~ proper compone2~ts. Pigmerlts ean be
added, 1:1~ th;~ ~s desired, by ~irst conventlonally preparing
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a suitable pigment dispersion and then adding this dispersi.on
to the compo 8 ition.
The composltions can be applied in any o~ the usual
ways. Spraying, roller-coating, dippingg doctor-blading --
all are suitable, although spraying is generally the method
of choice. The article to be coated is preferably pretreated
by grit~blasting, by the flame-spraying of metals or by frit-
coating. The article is then primed with a compositlon of`
the type disclosed in U S. Patent 3,655~604 or 3,694,392.
In a preferred embodiment the priming procedure is as ~ollows:
1. The ~ollowing were mixed together:
PTFE dispersion 478.76 parts
aqueous, 60~ solids
Deionized water 130.23 parts
Colloidal silica sol,327.18 par~s
30~ solids in water
(LUDQX AM* colloidal
silica~ E.I. du Pont
de Nemours and Company)
2. The following were separately mixed:
TRITON X-100* 17.52 parts
(Non-ionic sufactant
sold by Rohm & Haas Co.)
Toluene 31~ ~6 parts
Butyl carbitol 13.36 parts
Silicone 34.56 parts
(Dow Corni~g DC-8O1J
60% solids in x~lene)
85.52 part~ o~ (2) were added to (1) in a small
stream, with stirring, over a 2-3 minute period. To this
were then added, with stirring,
* denotes trade mark
, .

TiO2 (45% sollds disperslon35.46 parts
in water3
Channel black (22~ solicls0.85 parts
dispersion in
water)
Stirring was continued ~or 10-20 minutes. The resultlng
composition was then sprayed to a frit coated alumlnum
fry pan to a thickness o~ 0.2-0,6 mil (dry) and dried in
air.
The coating compositions of the invention are
ordin~rily applied to a thickness of about 20-30 microns
(dry) and the coated article is then baked at a tempera-
ture and for a time sufficient to fuse the fluoropolymer
used.
The compositions o~ the invention are most
useful for coating met~l cookware, especiall~ frypans,
but the compositions can also be used to coat other
articles requiring scratch resistant fluoropolymer coatings.
These other articles can be made of glass or any other mater-
lal capable of withstanding the baking temperatures used.
For example, the compositions can be used to coat bearings~
valves, wire, metal foil, boilers9 pipesJ ship bottoms,
oven liners, irorl soleplates~ waffle irons, ice cube trays,
snow shovels a~d plows~ chutes, conveyors, dies, tools such ~-
as saws, files and drills 9 hoppers and other industrial
containers and mcilds. ~ ~-
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3~
~ followlng example~ lllu~;tr~te the in7Jellt:Lon.
In these e~amples, all part~ and percent~ge~ ~re by weight
unless indicated otherwise.
The followlng were mixed~, in the order listed:
( 1 ) PTFE dispers ivn 64 . 9 pa~ts
(60% q~lid~ ln water~
TEFLON* Tp~ uorocQrbo~
~sin, Aqueou~ DlspersionJ
T 30, sold by E. I. du Pont
de Nemour~ and Compa~
(2) Deionized wa~er 10.5 parts
( 3 ) T102 coated mica 4 . 00 parts
(.AFFI AIR* NF- 140-D,
sold by :1:. I. du PoIlt de
Ne~ours and Compa~y)
t4) Red mill base 0.2 part
(made by b~ll milling a
rQlxture of
Red iron o~ide44.9 parts
Deionized w~tel~ 33.7 parts
Ole~ c acid30 3 part~
Trietha~olamir~e 6 . 7 part~
But~l c~rbitol2 . 9 p~Lrts
Toluene 8.5 parts)
(5~ A mixture o~
Triethanolamine . 92 part
Ol~ic acid ~ 75 part
To:Luene 3.48 paxts
Bul;yl carbitol 1.3 parts
* denotes trade ~Irk
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(6~ Methyl methacrylate/ethyl 14 parts
acrylate/methacrylic acid
39/57/4 terpolymer disper-
sion (40% in water)
The resulting compositioll was applied to an
aluminum frypan3 which had been fi:rst fritcoated and primed
according to the ~referred embodiment of a priming procedure
described hereinbefore.
The composition was applied by spraying ts a thick-
ness of 25 microns (dry). The coated pan was khen baked for5 minutes at 425C. to give a scratch-resiskant gold fini~h.
Example 2
The procedure of Example 1 was repeated, except that
the following were substituted for (3) and (4):
(3) TiO coated mica 4 parts
(~FFL~IR NF-154-D
sold by E,I. du Pont
de Nemours and Company)
(4) Mill base
(made by ball milling a
~ mixture Or
: Deionized water ~5 par~s
C~balt oxide blue 45 parts)
The resulting composition was applied to a frit
coated, primed aluminum frypan, as in Example 1, to give a
scratch resistant silver finish.
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~e~
The following were mix~d, in the srdel listed:
(1) PT~E di~per~l~n ~ Example 1 69.7 parts
(2) D~ionized water 8.7 par~s
( 3 ) T~02 coated mica 1. 0 pQrts
(AFPLAIR NF-140~I), 301dl by
E. I. du Po~t de Nemours and
Compa~y)
( 4 ) Red mlll bas ~ o:E Example 1 0 . 2 part
(5) The mi~sture in (5) o~ Example 1 6,45 p~r~s
(6) ~he disperslon of (6) in Example 1 14.0 part~
The r~sultirlg c~p~sition was applied to a ~:rit-
coated, primed alumi~um ~ryp~n3 as i~ :E5xample 1, t~ give a
~cratch resistant copper ~ini~h..
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