FLUOROCARBON POLYMER COMPOSITIONS

POLYMERES DE FLUOROCARBONE

English Abstract

FLUOROCARBON POLYMER COMPOSITIONS
ABSTRACT OF THE DISCLOSURE
Fluorocarbon polymer coating compositions
containing
(a) a fluorocarbon polymer
and
(b) a polymer which depolymerizes, and whose
depolymerization products vaporize, at the
fluorocarbon polymer fusion temperature,
give films with greater density and less porosity when
applied to cookware.

Claims

The embodiments of the invention in which an exclu-
sive property or privilege is claimed are defined as follows:
1. An article bearing
(a) a cured primer coating derived from a composition
selected from the group consisting of (A) a composi-
tion comprising
(1) 30-90%, by weight of the total of (1) and (2)
solids, of a polymer of hydrocarbon monomers
completely substituted with fluorine atoms or
a combination of fluorine atoms and chlorine
atoms,
(2) 10-70%, by weight of the total of (1) and (2)
solids, of colloidal silica having a silica
content of 30% and a pH of 9.0 at 25°C, whose
particles are surface modified with aluminum,
have a size of 13-14 millimicrons and a
specific surface area of 210-230 square meters
per gram,
and
(3) a liquid carrier,
and (B) a composition comprising a fluoropolymer,
a liquid carrier and lithium polysilicate;
overlaid with
(b) a cured topcoat of a composition comprising
(4) 25-95%, by weight of the total of (4) and (5)
solids, of a polymer as in (a)(1),
(5) 5-75%, by weight of the total of (4) and (5)
solids, of a polymer of ethylenically unsatur-
ated monomers which contains one or more mono-
ethylenically unsaturated acid units,
and

(6) a liquid carrier.
2. The article of Claim 1 in which the cured
primer coating is derived from composition (A).
3. The article of Claim 1 in which the cured
primer coating is derived from composition (B).
4. The article of Claim 2 where in (b)(5) the
ethylenically unsaturated monomer is 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 or a glycidyl ester of 1-14 carbon atoms, and
mixtures thereof, and the monoethylenically unsaturated acid
is selected from the group consisting of acrylic acid, meth-
acrylic acid, fumaric acid, itaconic acid, maleic acid or
maleic anhydride, and mixtures thereof.
5. The article of Claim 2 where in (b)(5) the
polymer is a methyl methacrylate/2-ethylhexyl acrylate/meth-
acrylic acid terpolymer.
6. The article of Claim 2 where in (b)(5) the
polymer is a butyl acrylate/methyl methacrylate/ester/acrylic
acid quadripolymer, where the ester is
<IMG>
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.
16

7. The article of Claim 2 where in (b)(5) the
polymer is a styrene/methyl methacrylate/ester/acrylic acid
quadripolymer, where the ester is
<IMG>
wherein the R1, R2 and R3 groups are saturate 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.
8. The article of Claim 2 where in (b)(5) the
polymer is a methyl methacrylate/ethyl acrylate/methacrylic
acid terpolymer.
9. The article of Claim 2 where in (a)(1) and (b)
(4) the polymer is polytetrafluoroethylene.
10. The article of Claim 3 where in (a)(1) and
(b)(4) the polymer is polytetrafluoroethylene.
11. The article of Claim 5 where in (a)(1) and
(b)(4) the polymer is polytetrafluoroethylene.
12. The article of Claim 6 where in (a)(1) and
(b)(4) the polymer is polytetrafluoroethylene.
13. The article of Claim 7 where in (a)(1) and
(b)(4) the polymer is polytetrafluoroethylene.
14. The article of Claim 8 where in (a)(1) and
(b)(4) the polymer is polytetrafluoroethylene.
17

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
15. An article bearing
(a) a cured primer coating derived from a composition
selected from the group consisting of
(A) a composition consisting of
(1) 30-90%, by weight of the total of (1) and (2)
solids, of a polymer of hydrocarbon monomers
completely substituted with fluorine atoms or
a combination of fluorine atoms and chlorine
atoms,
(2) 10-70%, by weight of the total of (1) and (2)
solids, of colloidal silica having a silica
content of 30% and a pH of 9.0 at 25°C, whose
particles are surface modified with aluminum,
have a size of 13-14 millimicrons and a
a specific surface area of 210-230 square
meters per gram,
and
(3) a liquid carrier:
(B) a composition comprising a fluoropolymer, a
liquid carrier and lithium polysilicate;
(C) a composition comprising
(i) 30-90%, by weight of total solids, of
a polymer of hydrocarbon monomers completely
substituted with fluorine atoms or a
combination of fluorine atoms and chlorine
atoms,
(ii) 10-70%, by weight of total solids, colloidal
silica having a pH of 8.4 - 9.9 at 25°C whose
particles have a size of 5-100 millimicrons
and specific surface area of 125-420
square meters per gram;
18

(iii) 1-10%, by weight of total composition,
alkyl benzene
(iv) 1-10%, by weight of total composition,
alcohol containing 4 or more carbon atoms,
said alcohol being miscible with water;
(v) 0.3-10%, by weight of total composition,
fatty acid containing 8 or more carbon
atoms;
(vi) 1-15%, by weight of total composition,
amine having the formula NR1R2R3 wherein
R1 contains 1 to 6 carbon atoms, said R1
being unsubstituted or substituted with
other functional groups, and R2 and R3
contain one to six carbon atoms or are
hydrogen; and
(vii) a liquid carrier; and
(D) a composition comprising
(?) 30-90%, by weight of the total (?) and (.beta.)
solids, of a polymer of hydrocarbon monomers
completely substituted with fluorine atoms
or a combination of fluorine atoms and
chlorine atoms;
(.beta.) 10-70%, by weight of the total of (?) and (.beta.)
solids, of a binder which comprises (i) about
5-95%, by weight of the total of (i) and (ii)
solids, of a colloidal silica which air dries
to form a continuous film when laid down
by itself, and (ii) about 5-95%, by weight
of the total of (i) and (ii) solids, of a
salt of a polyamide acid represented by
the structure
19

<IMG>
where G is hydrogen or a carboxyl group; ? denotes
isomerism;
R is a tetravalent organic radical containing at
least two carbon atoms, no more than two
carboxyl groups of each polyamide acid unit
being attached to any one carbon atom of
each tetravalent radical;
R1 is a divalent radical containing at least two
carbon atoms, the amide groups of adjacent
polyamide acid units each being attached to
separate atoms of the divalent radical;
and n is a number large enough to give the polyamide
acid an inherent viscosity of at least 0.1,
measured as a 0.5% solution in N,N-dimethyl-
acetamide at 30°C
neutralized with a stoichiometric amount of tertiary
amine;
(.delta.) about 10-90%, by weight of the polyamide
acid amide salt, of a compound selected
from the group consisting of N-methyl
pyrrolidone, dimethyl formamide, dimethyl-
acetamide, dimethylsulphoxide, cresylic acid,
sulpholane and formamide, and

(?) a liquid carrier,
overlaid with
(?) a cured topcoat of a composition comprising
(4) 25-95%, by weight of the total of (4) and (5)
solids, of a polymer as in (a)(1),
(5) 5-75%, by weight of the total of (4) and (5)
solids, of a polymer of ethylenically unsatur-
ated monomers which contains one or more mono-
ethylenically unsaturated acid units,
and
(6) a liquid carrier.
16. The article of Claim 15 in which the cured
primer coating is derived from composition (C).
17. The article of Claim 15 in which the cured
primer coating is derived from composition (D).
18. The article of Claim 16 in which composition
(C) additionally contains an anti-mudcracking agent, said
agent being a silicone, at a concentration of up to 10%
by weight of total solids.
19. The article of Claim 16 in which composition
(C) additionally contains a polymeric adjunct at a con-
centration of 5-25% by weight of total solids.
21

Description

1046359
BACKGROUND OF THE INVENTION
Cookware coated with fluorocarbon polymeræ of
various sorts has come into widespread use in recent years.
Almost every housewife prefers to use such cookware in her
kitchen because food is less likely to stick to it and
because it is so easy to clean.
~,-
It has now been found, according to th$s invention,
that the ~luorocarbon polymer film whlch coatE such cookware
can be made den er and less porous, and that this makes the
product still easier to clean and improves its appearance
by making the fini~h glossier.
. ~ , .
:.
. ' '
~:.
. ~ '
`~: , ' ' - - -
- 2 -
.. .
'~

1046359
SU~lARY OF THE INVE~TION -
One can get these advantages by uslng, lnstead of
the customary fluorocarbon polymer coo}cware enamel, a compos-
ltlon ~rhlch cont~ins as lts prlncipal lngredlents a fluoro-
c~rbon polymer, a polymerlc ad~unct having specl~ic physlcal
properties, and a llquld carrler.
The fluorocarbon polymers used in thl~ composltion
are tho~e of hydrocarbon monomers completely substltuted
wlth fluorlne atoms or a coaibination of rluorlne atoms ~nd
10 chlorlne atoms. Included ln thls group are polytetrafluoro-
ethylene (PTFE), copolymers o~ tetrarluoroethylene and hexa-
rluoropropylene ln all monomer unit welght ratios (FEP) and
fluorochlorocarbon polymers such a6 polymonochlorotrifluoro-
ethylene. PTFE 18 preferred.
The fluorocarbon polymers used are particulate.
Tho partlcles should be small enoug~ to pass through the
noz~le Or a spray gun wlthout clogging lt and also small
enough to glve the resulting rilm lntegrity. In ordinary
sltuatlons, the partlcles ~hould be no larger than about 0.35
20 mlcron ln the longest dimenslon.
Although a d~ rlour or powder Or fluorocarbon
polymer can be used, a polymer in the rorm of an aqueous dis-
persion i8 pre*erred because lt is most easlly obtained in
that *orm. Dlsperslons Or rluorocarbon polymer in org~nlc
llqulds miscible ~rith water, such as ethanol, isopropanol,
acotone and CELLOSOLVE* solvent~, can al80 be u~ed. In
either case, the liquld also serves as a carrier *or the
compositlon.
* denotes trade mark
-- 3 --
',
. ~ .
" ~, . . .

~04~359
The fluorocarbon polymer 18 ordinarlly present
in the compo~itlon at a concentration Or rro~ about 25f
through about 95~ (by wel8ht) Or the total or rluorocarbon
polymer and ad~unct poly~er sollds, pre~erably from about
85% through about 95~, even ~ore prererably 85~ through
about 89~
Broadly spoaking, the poly~oric adJuact can be
any polymer or ~thylenlcally unsaturated ~ono~ers wAlch
dopoly~eri~es, and ~hOBO dopolyoorlzation products ~ porl~e,
in the te~peraturo range or rro~ about 150C belo~ tho
rusio~ to~per~ture o~ the rluorocarbon poly~er u~ed
to about the rluorocarbon poly~or's doco~posltlon t-~perature
The closer the depoly~erl~ation nd ~apori~ation te~peratures
are to the ~luorocarbon'a ~u~io~ te~p-raturo, tho better
~ Depoly~eri~atlon" m-an8 degrad~tlon o~ tho poly~cr
to the point at ~hlch ~ho degr d~tion products are volatile
at tho teuper~ture~ ncounterod ln curlng th- ~lla The-o
dogradatlon producta can be ~onomora, di~ors or oligo~r~
UVaporl~o" oan~ ~ol-tlll~ation o~ the degradatlon
product- and thelr e~aporatloA`rro~ th- ril- Ido~ , all
o~ tho dogradatlon produets pas~ rrO~ the rll., but as~a
pr~ctical ~tter, a aa~ll but insignirlcant auount g-nerally
r- ain-
Illuatr tive o~ the polY~eric adJunct~ ~hich ean
b- usod re poly~-rs o~ thyle~i~ally unsatur~ted ~on~a~r~ ~-
~hich ¢ontal~ o~- or ~ore ~onocthylenieally un~aturat-d aeid
unit~

~O~f~359 -
Representative of the~e ethylenically unsaturated
monomers are alkyl acrylates and methacrylates having 1-8
carbon atoms in the alkyl group, styrene, alpha methyl styrene,
vlnyl toluene and glycidyl esters of 1-14 carbon atoms.
Alkyl acrylates and methacrylates are preferred.
RepresentatiYe Or the monoethylenlcally un~aturated
acids are acrylic acid, methacrylic acid, fumaric acid,
itaconic acld and maleic acld (or anhydrlde). Acrylic acld
and methacryllc acid are pre~erred.
The preferred glycldyl ester unlt 18 one derlved
rrom a product sold by the Shell Chemical Co. as CARDURA E*
ester. Thls i8 a mixed ester Or the general ~ormula
0 0 R
/ \ " ~ 1
H2C - CH - CH2 - 0 - C - C - R2
where
R1 1B CH3
and
R2 and R3 are lo~er alkyl groups,
Rl, R2 a~d R3 containlng a total
Or 7-9 carbon atoms.
* denotes traae m~rk
-- 5 --
.. . .. .
,

~046359
The polymerlc adJuncts preferred ror use are
1. methyl meth~crylate/2-ethylhexyl acrylate/
methacryllc acld terpolymers, pre~erably the
46-50/48-52/1-4 (welght ratlo) terpolymers,
2. butyl ~crylate/methyl meth~crylate/CARDURA E/
acryllc acid quadripolymers, prererably the
23-27/33-37/21-25/15-19 quadripolymers.
3. styrene/methyl methAcrylate/CARDURA E/acrylic
acld quadrlpolymers, pre~erably the 28-32/28-32/ ~-~
21-25/15-19 quadrlpolymer6.
.
4. methyl methacrylate/ethyl acrylate/methacrylic
acld terpolymers, preferably the 37-41/55-59/1-6
terpolymers.
The polymeric adJunct 18 ordln~rlly pre~ent in the composi-
tlon at a concentratlon Or rrom about 5% through about 75%
(by w-lght) Or the tot-l Or ~luorocarbon polymer and ~d~unct
polymer ~ollds, pre~erably about 5% through about 15%, even
more prerera~l~ 11% through about 15%.
m ese polymerlc adJuncts can be m~de by any o~ the
20 conventional ~ree-radlcal tecbniques ~amiliar to any polymer - ;
chemist. The composltlon can also contaln such conventional
additlves as pig~ents, ~lllers~ ~lo~ co~trol agents, plastici-
zer~, etc., as seea nece~sary or desirable. These additlves^
arc added ror the u8ual reasons, in the usual ~ay~ and in tbe -~
usual amounts.
_ 6 -
..
. . . -. . -, -- . .... ~ -. ~ ,, , , . ~ , .- ,.
. , . . -. .. - , ~ - . ~ . . . . ....

~o4~35~3 :
m e compo~ltion is made by first choosing the rluor
carbon polymer, polymeric ad~unct and such conventional addi-
tive~ as may be used, and the amountR of these be~t suited to
the purpose. m is can be done wlth no trouble by one skllled
in thls art. Preparation of the composition i8 then a slmple
matter of thoroughly mlxlng these components.
The composltion will be most userul ror topcoating
metal cookware, especially rrypans, but can be used ~ust as
well on other cookware, or other metal articles requiring lub-
rlcious surraces, such as bearings, valves, wire, metal rObollers, plpes, ship bottoms, oven liners, iron soleplates,
wa~le lrons, lce cube tray~, snow shovels and plows, chutes,
conveyors, dles, tools such as saws, riles and drills, hoppers,
and other industrlal container~ and molds.
The composltion can be applled ln any Or the usual
ways. Spraylng, roller-coating, dlpping, doctor-blading--all
are suitable, although spraylng 18 generally the method Or
cholce. The article to be coated 18 preferably pretreated by
grlt-blastlng, by the rlame-spraylng Or metals or by frlt-
coatlng. m e article i~ then primed ~ith a lithium poly~ill-
cate composltion Or the type dl~closed ln U.S. Patent 3,694,392 ~'
o~, alternatlvely, ~lth a composltion comprising
(l) 30-90~, by weight Or the total of (l) and (2)
sollds, Or a poly~er of hydrocarbon monomers
co~pletely sub~tltuted ~lth rluorlne ato~s or
a combinatlon Or ~luorine atoms and chlorlne
- atom~,
(2) 10-70~, by weight Or the total Or (l) and (2)
solids, Or colloldal 811ica having a slllca
content Or 30% and a pH Or 9.0 at 25C, ~hose
partlcles are surrace modlried wlth alumlnum,
have a size Or 13-14 mlllimlcrons and a speclrlc
,. . . . - . ~ . ..

~046359
surface area Or 210-230 square meter~ per gram,
and
(3) a liquid carrier.
The compo61tion lf preferably applied to a thick-
ne~s Or about 0.5 to 5 mil~ (dry) and then baked for from 0.5
to 30 minutes at a temperature o~ from 370 to 460C.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Those ~killed in this art will be able to practice
this invention more ea6ily by rirst referring to the rollow-
ing lllu~trative example. These artisans, will, no doubt, beablc to compo~e num-rous variations on the theme dlsclosed,
euch as chan~ing the amounts Or ingredi~nts sllghtly but
inslgnlflcantly ~ro~ those show~, aading innocuous substances,
or substitutlng oquivalent or nearly equlvalent components
ror those shown. All these variations are considered to be
part Or the inventlve concept.
- 8 -
A
r: . . , , .. . , ,, ~

10~6359
~xa~ple 1
A repr~sentative coatlng co~po~itlon of the
ln~-ntion i8 ~adc a~ ~0110~8 (all parts are by ~elght)
lx togeth-r
PTFE dlspersion 411 parts
~queous, 60~ ~olids
~ater 72 p~rt~ -
(2) Separat~ly ix
Triethanola-~ne 12 part~ -
Oleic acid 6 part~
Tolu~n~ 40 2 part~
Butyl carbitol 7 2 part~
(3) Propare a ~111 b-~e b~ d xing and
then pobbl- ~llliag
~at-r 67 part~
Ch~n~l blac~ 20 part~ -
Sodlu~ polynapthal~no 3 part~
~ulronate
Alu ln~ ~llleato 10 part-
morou4hly d x (1) a~d (2). Then add to thl~
~i~turo, ~lth tlrring, 90 p~rt~ o~ an aquoou~ disperslon,
40~ 8011~, 0~ a n thyl ~thaer~l t~/~thyl acr~lat /-
~othacrrllc acld 39/57 h (~oight ratlo) terpoly~ r Th~n
bl~cd 37 2 part- o~ (3) l~to thls l~turo, ~lth stlrrlng
Jpray thc re-ultla~ co posltlon to ~rlt-coatcd alu lnu~ pa~
prl~ d ~lth a prl~er o~ thc typc sho~n ln U8P 3,694,392, to
-~thlc~ ~s Or 0 8-1 ~il (dry). Th~A ba~e the paa ~or
5 ~inut-~ a~ ~30C. Tho ra-ultlng ~inish ~111 bo glo88
and d~n~
_ 9 _
,
.. . . .

10463S9
Example 2
Repeat Example 1, except in place o~ the prlmer
~hown, use one m~dc as rollo~8:
(1) ~ix together
PTFE dlspersion 478.76 part~
~queous, 60~ Bollds
Delonized ~ater 130.23 part~ :
Colloidal sillca sol 327.18 part-
30% 801idB in ~ater
(2) Scparately alx
TRIT0~ S-100~ 17.52 parts - -
(non-ionic ~urracta~t
801d by Roh- & ~aa~ Co.)
Toluene 3~.56 part~ :
Butyl carbltol 13.36 part-
Slllcoa~ 34.56 parts - .
(D~-Corning DC-801~, .
60% ~olld8 i~ xyl~ne)
A~d 85.52 part~ Or (2) to (1) in a 8mall strea~ ov~r a 2-3
~i~ute porlod, ~lth ~tlrr~ag. Thea add, ~lth ~tlrri~g,
.
T102 (45~ ~ollds ia ~t-r)35.46 part~
~ aa~l `! , . '
~ Ch DC ~ blac~ o.85 parts
l`~ (22~ .Olia~ t~r)
Coatl~u- ~tlrrln~ rOr 10-20 ~inute~. ~
` Spray thl~ co~po81~10~ oa th~ ~rlt-coat~d alu~inua. .:. :
; p~ o~ ~xw~plo 1 to w thlc~c-~ or 0.2-0.6 ~il (dry) d lr ~ `
r~ lt.
l. i . , :
9 `' ` ~
` L~DOX ~ colloidal ~llica, ~old b~ ~.I. du Pont d- J ~our~
` ~ - 10 - ,
~"~' ~ ,'"' '
~ A

1046359
SUPPLEMENTARY DISCLOSURE
It has now been found that further compositions
may be used in the preparation o~ the cured primer coatings
Or thc artlcles of the present invention.
As stated hereinabove the article to be coated is
preferably pretreated by grlt-blasting, by the flame spraying
Or metal~ or by frlt-coating. m e article may then be
primed with a composition of the~type de~cribed previou~ly
or, alternatively, the article may be primed with composltions
of the type disclosed in U.S. Patents 3 986 993 and
4 011 361. Such compositlons contaln ~luorocarbon polymer,
colloidal silica and a liquid carrier.
one prlmer composition, descrlbed ln U.S. 3 986 993,
comprlses (a) 30-90~ by weight o~ total solids of ~luoro- -
carbon polymer Or the type described hereinabove, (b) 10-70%,
by weight o~ total solids, colloidal silica h-ving a pH
Or 8.4 - 9.9 at 25C whose partlcles have a size Or 5 - 100
~lllimlcrons and speclfic surrace area Or 125 - 420 square
mctrc~ per gram; (c) 1 - 10~, b~ welght Or total co~position,
alkyl benzene; (d) 1 - 10~, by weight of total composition,
alcohol containing 4 or more carbon atoms, ~uch alcohol belng
~lsclble wlth ~ater; (e) 0.3 - 10~, by welght o~ total
compositlon, ratty acid containing 8 or more carbon atoms;
~ (r) 1 - 15~, by ~ei8ht Or total compositionJ amine having the
rormula NR~ hereln Rlcontains 1 to 6 carbon ato~s
and ~y contain other runctional group~, and ~ ana
contain one to ~i~ carbon ato~s or are hydrogen; and (g)
a liquld carrier. me compo61tlon Eay al~o contain an anti-
mudcracklng age~t, e.g. a slllcone, at a concentratlon up
to 10% ~y ~eight Or total solids, or a poly~eric ad~unct
at a concentratlon Or ~ - 25% by ~elght of total ~olid~.
The polymer ad~unct can be any polymer Or ethylenlcally --
:::
- 11 -
_. .,
..,., ,; , . ... ,.. - - -, , ~ ,
.. . . . .. .

104~3S9
unsaturated monomers which depoly~erizes, and whose depoly-
merization products vaporize, in the temperature range of
~rom about 150C below the fusion temperature o~ the
rluorocarbon polymer used to about the fluorocarbon polymer~ 8
decompo~ition temperature. The clo6er the depolymerization
and vaporlzation temperatures are to the fluorocarbon's
fu~ion temperature the better.
Anothcr primer composition, de~cribed in U.S.
4 011 361, comprises (a) about 30 - 90% by weight of the
total (a) and (b) solids, Or fluorocarbon polymer Or the
type described hereinabove, (b) about 10 - 70%, by welght
Or the total of (a) and (b) ~olids, Or a binder whlch ~ -
comprises (i) about 5 - 95~, by welght of the total of
(1) and (ii) solids, of a colloidal ~llica which air dries
to rorm a continuous rilm when laid down by itselr, and
(11) about 5 - 95~, by weight Or the total of (i) and (ii) . :
solids, Or a salt Or a polyamide acid represented by the
structure
.' :
G COOH ..
R
_ N C C N Rl _ :
O O ''~'
_ _ n0 ~here a 18 hydrogen or a carboxyl group; ~denotes
isomerism;
R 18 a tetravalent orgaaic radical containing at ~ ;
least two carbon atoms, no ~ore th~n two carboxyl
groups Or each polyamlde acld unit being attached
to any one carbon atom Or each tetravalent radlcal;
_ ~2- '

~046359
Rl i8 a dlvalent radlcal containlng at least tw~
carbon ~toms, the amide group~ Or ad~acent poly-
amide acid unit~ e~ch bcing attached to sep~rate
atoms oi the dlvalent radical;
and n is a number large enough to give the polyamide
acid an lnherent visc06ity of at least 0.1,
measured as a 0.5% solution in N,N-dimethyl~cet~mide
at 30C
neutralized with a stoichoimetric amount of tertiary ~mine;
10 (c) about 10 - 90,~, by weight of the polyamide acid amide
salt, of N-methyl pyrrolidone, dimcthyl formamide, di-
methylacetamide, dimethyl sulphoxide, cresylic acid,
sulpholane or ~ormamide ~nd (d) A liquid carrier.
The colloidal silica Or the primer composltion used
in the present inventian is generally in the form Or an
aqueous 801 Or silica particles. me colloidal silica is
made up of discr~te spheroldal particles of 8ilica having
no detectable crystallinity. Some surface silica atom~ -
may be replaced by aluminum atoms, and ammonium or sodium
lons ~r be used to stabillze the 801, as is known in the
art. Typlcally, particles have a size in the range of
5 - 100 millimicrons, pre~erably 7 - 25 millimicrons as
measured optically against a ~tandard, with a speciric
surrace area of 125 - 140 squore meters per gram and a
pH of 8.4 - 9.9 at 25C. Colloidal silica 801s useful with
this invention include those sold by E. I. du Pont de
Nemours and Company a6 LUDOX - H540, LUDOX - HS, LUDOX - LS,
LU130X - SM30, LUDOX - ~M, LUDOX - AS and LUDOX - AM.
Mi~ctures Or comp~tible colloidal sllica s018 can be used.
The topcoat composition Or the invention is
applied over the primer composition, a8 described previously.
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1046359
m e preRent invention is further illu~trated by
the following example:
EXAMPLE 3
A primer com~osltion of thc type described in
U.S. Patent 4 011 361 wa~ made by adding to a vessel in
the order stated and mixing:
1. The polyamide acid amine
salt solution of Example 1
of U.S. Patent 4 014 834
(containing 18% of furfuryl
alcohol and 10~ Or N-methyl-
pyrolidone) 151.8 p~rts ~-~
2. Furfuryl alcohol 15.2 parts
3. Deionized ~ater 520.0 parts
4. Whlte pig~ent dispersion
(m~de by ball-mllllng a
mixture of :
T102 46 parts
Water 46 part~
Triethanola~ine/
oleic acid mi~ture
2/1 8 parts
5. PIFE di~persion in water
(60% solids) 222.5 parts
6. L~DOX AM colloidal ~llica29.8 part~
The resulting composition is ~prayed on a grit-
.
blasted aluminum pan to a thickne~s of 5 microns (dry) and
then air-dried.
The prlmed pan i6 then coated with the topcoat of
Ex~mple 1, and the pan i~ baked for 5 mlnutes at 400C.
The resulting finish wlll be glo~sy and dense.
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