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Patented Mar. 11, 1947
2,417,344
UNITED STATES
‘OFFICE
420 Monsanto "Chemical ‘company, YSt. vlL‘ifllliS,
‘Mm, alcoriporation‘of Delaware
'
‘Noinawiiig. ii'ppiicajtionmayisfrei'z,
serial No. 4423232
(Cl. 11064-186‘)
:8 Claims.
‘1
improved coating compositions, and particularly
This invention ~relatesfto ‘the preparationof
‘to the preparation of-la'cquer 'compositionscon
’
I
It vhas been recognized forrnfany years Ethat
‘pigmented ooatin’ga'such asipaints and varnishes,
are subject to what ‘is known as “h'ardisettli'ng,”
i. e., that type of-‘settling-tvhiéh'resultslin'lthe
formation er a hard cake ‘which ‘isyvery difficult
‘hinder in-thelacquer'isnot too-low. Lacquers,
however, ‘commonly-1oompriselmixtures ¥ or more for
;less polar isdlvents, f-su'ch asl'es'ters, 'iketo'ne‘s. and
to redisperse. IIn'generaL-"highIydispersed pig
alcohols, ‘with hydrocarbons, which ;are essentially
‘non-pclan'and-as' the proportion of hydrocarbons
I ine'nts settle slowly, ‘but are especially subject-to
hardse'ttlin'g of'thetype described. riAe-?occulated
pigment -'suspension, on ‘the other vhand, ‘settles
rapidly, but ‘forms a voluminous, iloosely packed ‘‘
layer, enclosing considerable liquidin the pores
and capable ofeasy redis‘persion. The extent of
settling and the degree ofe?occulationlu'sually de—
pend not only ‘upon what ‘is adsorbed at~the*s1ir
‘face of’ the ‘pigment but also upon the ‘nature :of
the adsorbed layer and upon the nature or the
‘liquid in which the pigment and i-lits'a'dsorbed
layer ‘are suspended.
In the case of pure liquids, noni'polar-solvents
tend to'yield ?occulated suspensions ‘while polar
liquids tend to yielddispersed, hard settling types.
In non-polar liquids,‘ such as benzene, the pres~
fence of or'addition of an amountcof-"water su?‘l
‘cient to coat the-suspended pigment with a mono
molecular layer of water tends'toIpro-mote ?occu
lation and the formation ‘of more voluminous
sediments than is the c'as'e‘with pure liquids ‘not
containing Water. ‘As thepolarity of the solvent
increases, however, thatis, as its kinship @with
water becomes closer, the'addition 'of‘waterrbe
comes less effective and the pigment tends'more
and more to settle hard. In the case of'ethyl
acetate, for example, ‘which is more polar
than benzene, a larger amount of Wateris'neces
sary to give a certain degree of ‘?occulation as
measured by the volume of the ‘settled, pigment
layer. In the case of methanol, Which is more
polar still, no amount'of'w'at'er produces ?occula
tion.
Numerous 'eifo'rts have beenmade to avoid ‘the
e?ects ‘of- hard v-s'ettling,iin some instances, with
considerable success. Small amounts of 'stearates,
such‘ as sodium,‘ aluminum - and zinc stearate, "for
example, ‘have been added to paints, varnishesand
lacquersior ‘the purpose of ?occula'ting or pre
venting the ‘hard settling of "suc'h‘subs'tances as
diatomaceous earth. These'materiais, however,
‘tend to1vveaken'1the ?lm‘ formed upon-applying
‘jection‘all?lms.
As indicated above, water is also in some 9in
- stances -'e'ifective iii-‘preventing :hard settling, :and
‘this supp-lies vnot only‘to ' ordinary pigments, ‘but
' also '7 to Ia'ero‘gel containing »-l'ac'q'uers, particularly
‘if the co‘r1'centrationv of ‘the nitrocellulose ‘or other
‘Gaining pigments, aerogels or like substances
tending toi‘rs‘ettle.
2
“er'ates which vresult ~"in rough or rotherwise ob~
is decreased ;~m'or'e and. ‘more water 1is- required? for
i'?occu-lation, "While insome cases inc amount of
"Water vwill produce ‘satisfactory suspensions. 'In
“any case, the addition ‘of’ large amounts of ‘Water
‘is ‘inadvisableas it ‘increases the possibility 3.0f
~"c‘ontamination or‘ discoloration Lo'fcth'e ‘coating. in
the presence of metals.
lJItli's at primary‘ object-fofithe present :invention
“to ipr’ovi'defa‘n 'improvedx'methodiof preventing
ihardlsettling inicoating compositions.
further i'objectiof the invention is to prepare
soft ‘settling ‘coating :compo’sitions ‘which "do not
lfo'rmi‘tveak orfpoorlyadhering ?lms lupon drying.
'furthersobj ect ‘ofi the invention is to prepare
soft: settling rcoating .i'compositions of :the type de
scribed; Iwhich previously;could ‘not-be. made‘ soft
settling-'i-bec'ause-"of the low-concentration'iof the
binder and/or the excessive polarity of the vehicle
‘used.
L‘A"furth‘er object of theinvention ‘is'to'p'rovide
an agent'for incorporation ‘in 'la'cquerspr' ‘other
. coating 'compos'itionswvhich‘not "only'acts" to we
‘vent hard settling,'but ‘t‘endst'o‘prevent ‘deteriora
tion 'or ‘discoloration vof ' the ‘ coating 'whe‘n‘in" the
.ipres'en‘c'e‘ of ‘ metals.
‘ Still further objects and - advantages or the in
"ventionwilrappear from the following description
~~andzappended ‘claims. :Beior'e explaining in de
‘itaiihtheipresent- invention, however, it is to-ibe
': understood-that the/invention’ is not limited in its
"applicationit‘o the details-described herein,-since
Lthe inventionis' capable'cof other embodiments and
~ofi1b'ein'gpra'cti‘ced orrcarried out in variousways.
:--A1so1' it' 'isi-to bet-understood‘ that‘ithe ,phraseology
for terminology employedxherein is- for-the-purpose
of description andinot. oflimitationeand it-is'not
~lintended l-tosli'mit the invention claimed ‘herein? be
50 » yond: the requirements :of' the :prior art.
The invention is‘ carriedi'out‘ inlzgeneralvby ad
mixing withthetpigmentedcoating'solutionismall,
' and‘ inlmostinstances;minuteiamounts of; an. am
'the coating, and "to" reduce its adhesion-tometa'ls
- monium,':aiky1amine; silkylblarhinaialicyciic amine
"orother‘surfaces. They also tend'to‘form- agglom-' 55 or h'eterocy'cli'ci amineisailt of a suitable inorganic
2,417,344
the range of 1X10?‘3 to l.8><10'5. In order to be
effective however, the amines should be used in
the presence of, or in the form of salts of acids
or organic acid. The salt employed should be sol
uble in the coating vehicle in the small amount
required and should be a salt of at least moder
about as strong as or stronger than formic acid,
ately ionizable constituents. Speci?c salts which
which has a dissociation constant of 2.4><10-4.
Moreover, the salts thus formed or used should
may be used in accordance with the invention in
clude: the mono, di and tributyl and amyl amine
be suf?ciently soluble in the solution being treated
to avoid any appreciable precipitation. Citric.
acid, which has a primary dissociation constant
salts of ortho and pyrophosphoric acids; dibutyl
. amine sulfate; triamyl amine malate; the ammo
nium salts of maleic andphthalic acids; and the
of 8><l0-4, gives somewhat more satisfactory re
diethyl amine, mono, di, and tributyl and amyl 10 sults
than formic acid, while acetic acid, which has
amine and the Cyclohexyl amine and morpholine
a dissociation constant of 1.9><l0—5,,is, distinctly .
salts of citric acid.
‘
less satisfactory than formic acid. Salicylic acid,
Instead of adding salts, as such, to the coating
which
has a dissociation constant of 1>< 10-3,
solution, it is also possible to add separately, a
'would be expected to be satisfactory, but was
suitable amine or ammonia, and an acid capable 15
found to be entirely unsuitable, probably because
of reacting with the amine to form a salt having
of the formation of a complex ion, which pre- the desired anti-settling or flocculating action.
cluded the formation of the R1 R2 R3 NH+ ion in
,In every instance it is essential that the resulting
sufficient amounts.
salt be thoroughly soluble in the solvents of the
Tests were also made with pyridine, which has
coating, that is, thoroughly soluble at least in the 20
a
dissociation constant of 1.6X10f9, and. aniline,
small amount required. Both substances should
which has a dissociation constant of 4.6><l0—l°,
also be at least moderately ionizable, as previously
in both instances in combination with suitably
indicated.
‘
I
strong acids, Salts of these bases however do not
In those instances Where the coating composi
appreciably improve the hard settling character
tion is already quite acid, thatis, already contains 25 istics of the lacquers treated, which indicates be
appreciable quantities of acid, as for examplein
yond doubt that the effectiveness of any soluble
lacquer containing shellac, copals, alkyd resins,
ammonium or amine compound employed depends
et cetera, the'addition of acid is unnecessary, and
suitable results may be obtained by merely adding
an amine or ammonia to the coating composition. 30
Moreover, quaternary ammonium compounds,
.
When strong bases such as cyclohexyl trimethyl
ammonium hydroxide are used, it is unneces
sary to employ an acid, as such bases are suf
such as cyclohexyl trimethyl ammonium hydrox
?ciently dissociated and have the desiredeffect
on the lacquer, provided they are su?icientlysolu
ide, dicyclohexyl dimethyl ammonium hydroxide,
phenyl trimethyl ammonium hydroxide,‘ and
phenyl ethyl dimethyl ammonium hydroxide, may
largely upon the extent of its ionization. ‘
35 ble, without the addition of acids.
In the case
of
the
weaker
bases,
such
as
ammonia
and the
be used in all instances without acid addition, as
aliphatic
amines,
which
in
general
have
a dis
these compounds are all very highly ionizable and
sociation constant of not less than about 1x104,
do not require the addition of an ionizable acid to
it is necessary to employ in combination there
obtain the desired results.
with preferably an acid which is as strong or
40
In determining what substances are suitable
stronger than citric acid, but in any case about
and what degree of ionization is required for the
as strong as formic acid. Thus, the acid should
purposes of this invention, tests were made‘ by
have a dissociation constant‘ of not less than
adding varying but in all instances minute
about lXl0'4.
amounts of selected salts or hydroxides, or mix
In general, exceedingly small amounts'of'the
tures of amines and acids capable of forming
salts or bases described herein as being suitable
salts of the type described, to a lacquer solution
may be used. For example, as little as .0001
prepared by mixing 9 parts by volume of commer
mol of alkylamine and an equal amount of acid
cial butyl acetate with one part by volume of a
for each 100 cc. of lacquer solution is suflicient.
base grind of the following composition:
When the amounts of amine and acid are each
Per cent by weight '
reduced to less than .0001 mol per 10000. of
solution, protection against hard settling in the
lacquer is lost. Cyclohexyl trimethyl ammonium
hydroxide and like quaternary ammonium com
Butyl acetate ___________________________ __ 25
Butyl alcohol ___________________________ __ 20
Toluene
___
__
29
Denatured alcohol ______________________ __
2.4
Blown castor oil ________________________ __
5
1/2 sec. nitrocellulose ____________________ __ ‘ 5.5
Santocel (silica aerogel) ________________ __ 13.1
,
pounds, however, may be used in amounts as
lowas .00005 mols per 100 cc. of solution. Larger
amounts of the anti-settling or flocculating agent
' may be required, when the amount of pigment in
This permitted a relatively accurate comparison
of the relative eiiectiveness of the various sub
stances tested. As a result it was discovered that
the amine or ammonium salts or hydroxides, or
the mixtures of amines and acids, to be effective,
must be soluble in the liquid being treated and
must be capable of developing a high concentra
tion of NR1 R2 R3 R4+ ions, in which R1, R2, R3, R4
represent either hydrogen or an organic radical.
Where the amine or ammonium hydroxide, or the
the coating is increased. ’,
A further understanding of the invention will
be obtained from the following examples:
Erample I
A commercial furniture lacquer was prepared
by dissolving suitable amounts of 5 second nitro
cellulose, a rosin-maleic aci-d-‘glyceride‘resin and
a plasticizer in a conventional lacquer solvent
mixture comprisingra mixture of esters,alc0ho1s
and hydrocarbons. The resulting lacquer was
acid in combination with it, has little tendency
given a dull or ?at finish by incorporating there
to dissociate, the effect is to produce in the solu 70 in a pebble mill grind of silica aerogel in, such an
tion not the active NR1 R2 R3 R4+ ion, but the
amount as to provide 15% by weight of’ silica
free amine NR1 R2 R3, which is inactive.
' based on the weight of the solids in the lacquer.
Of the amines tested, including'ammonia, those
About 0.25% by weight of dibutyl amine _pyro
which were e?ective for the purposes of this in
ventionall had a dissociation constant within 75.
phosphate based on the total weight of‘the lac
agreem
"5
'16
quee- wes then; added after ?rst dissolving; the
nwiolihosphate: in about. an. equal; weight of de
natured; alcohotto iacilitate mixing. The aerogel
in; the lacquer’ settled, in a ?occulent. condition
which permitted: easy redispersion. whereas the
A. base. grind of silica aerogel in a. portion of
the above, clear vehicle was then prepared by
mixing the following materials in a pebble mill
in the proportions given:
same-lacquer was; subject to hard settling when
the, pyrophosphate was omitted.
Per cent by weight
'
Clear base _______________ __‘ ______________ __ '74
Example II»
To a solution- containing, '75 parts by; volume
of,‘ ethyl; acetate. and. 25.‘ parts of ethyl alcohol
Silica aerogel ____________________________ __ 15
Butyl acetate ____________________________ __ 1‘0
10 Citric, acid _______________________________ __ 1
The resulting grind was then, mixed with ad'
there-was added about 6% by weight. of 5 sec
ond nitrocellulose and about 0.2% of dewaxed
shellac‘, The resulting‘ lacquer was flattened» by
grindinginto it about 1% by. weight of. silica aero
geibased on~,the_ solids in the lacquer. About
ditional clear base and monoamyl amine in the
following proportions to give a ?nal flat lacquer
composition having very desirable soft settling
15
characteristics.
,
0.201%, by. Weight of dibutylaminepyrophosphate
Per cent by/weight
leased; 0.11- the; total, weight of the lacquer was
then added the: pyrophosphate being, first dis.
solved inalcohol'to facilitate, mixing. The, addi
Aerogel grind _________________________ __
10
Clear base ______________________________ _. 89.96
Monoarnyl amine ______________________ I. 0.04
the?hardsettling, which occurred ._ when the pyroe
ment of lacquers which have been ?atted with
tion of_ the pyrophosphate e?ectually ‘ prevented 20
Although the examples refer solely to the treat
silica aerogel, it should be understood that‘the
phosphate was. Omitted...
invention may be equally as well, if not more
Example III
advantageously applied to other types ofcoating
Five percent by. weight of silica aerogel based
on the lacquer solids was ground in a pebble mill
into a celluloseacetate lacquer of the following
composition‘: ,
materials, such as paints‘, varnishes and “syn
thetics,” to which aerogels" or‘ other forms" of
pigment have been added for any purpose. In
general, however, there is- more need for the
Per cent. by weight 30 ?occulating‘agents‘ described herein in lacquers,
as ‘lacquer solutions frequently contain a large
9.2
proportion of polar solvents, which tend to‘in
-g _____ __,__-___ ____ __._ _____ -- 11-5
Toluene,_____,,_g,_ ____ _________ ____________ __
Butyl acetate
crease the possibilities of hard settling.
The anti-settling ‘or ?occulating agents used‘ in
accordance-with the invention may be added to
35 the coating solutions in anyv desired manner; It
Methyl phthalyl ethyl glycollate ____ _,_____ 9.2
is preferableihowever to ?rst prepare a relatively
Cellulose acetate _______________________ __ 4.1
concentrated solution of the ?occulating agent
The silica’ aerogel in the above lacquer settled in
in a solvent or solvent mixture which is readily
a ~few>hours tosa compact mass, butwhen 0.05%
miscible with the coating composition to be
by weight Of dibutyl amine‘ pyrophosphate based 40 treated. Suitable solvents for this purpose in
on the» total weight of the lacquer was added
clude acetone, lower aliphatic alcohols, glycol
thereto, only'a slight subsidence to a‘ soft volu
mono ethers, and the like.
minous layer‘ occurred.
'
Aerogels may be added to the lacquer in vary
Example IV
ing amounts depending on the degree of flatting
desired. Thus it is possible to employ the
To a lacquer consisting of 37% by weight of
aerogels in amounts varying from 0.02 to 30%
ethyl cellulose and 93% of acetone was added,
by. weight based on the weight of the lacquer‘
about 3% by weight of silica aerogel based on
Acetonehgg-g-g ------------- _-,_ _______ -- 26.4
Ethyl acetate __________________________ __, 24.0
Methyl Cellosolve ___ ___________________ __ 15.6
solids. When relatively hlgh'COl'lCBIltl‘?tlOllS of
the solids in the‘lacquer; The suspension of silica
silica aerogels are~ employed, it is advantageous
aerogel thus formed was effectively stabilized
against hard settlingby adding‘ to, the lacquer 50 ?rst to incorporate in the lacquer a small por
tion of acid, such‘ as phosphoric or citric acid, as
about 0.3% by weight of "dibutyl amine pyro
the presence ‘of the acid in the lacquer during
the grinding tends either to lower the viscosity
phosphatebased ‘on the total weight of the lac
quer whereas when the pyrophosphate. was
omitted theyaerogell settled. to ,acompact cake,
of the grind for a given silica concentration or
permit. a higher silica concentration for a, given
not easily redispersed.
viscosity. A composition free of hard settling
can then‘ be obtained by treating the lacquer
thus prepared with a suitable amine, which; if
added during the grinding in of the aerogel, tends
but- in which theethyll cellulose l was replaced
by cellulose .acetobutyrate orchlorinated rubber. 60 to raise “the viscosity.
The primary, secondary and tertiary butyl or
Example V
amyl amine salts of phosphoric or pyrophosphoric'
Alsoft settling ?at lacquer was prepared by
acid are preferred for the purposes of this in
?rst making a clear base of the following com
vention, since they not only favorably aiiect the
position:
65 suspension of the aerogel or other pigment'in the
Per cent by weight
coating solution, but have a marked anti-cor
Equally good results were also obtained by =
adding’ small amounts of- dibutyl amine pyro
phosphate to compositions similar to the above,
Ethyl
Butyl
Ethyl
Butyl
acetate
acetate
alcohol
alcohol
_________________________ __
__________________________ __
__________________________ __
__________________________ __
10
17
10
l0
Aromatic petroleum naphtha ___________ __ 30
5 second nitrocellulose _________________ __ 5
Rosin-maleic ester resin ________________ __ 15
Dibutyl phthalate ______________________ __ 1.5
Blown castor oil _______________________ __ 1.5
rosive action when used in coatings which are to
be packaged in metal containers.
Where reference is made herein or in the ap
70 pended claims to “pigments,” it is to be under
stood that this includes not only the inorganic
oxides commonly added to coatings for coloring
and other purposes, but also aerogels, which are
usually added to obtain a ?at or dull ?nish in
75 the applied coating. The term. "hard settling”
* 2911173344
solvent therefor, and silica aerogel, said aeroge'l
is also intended to ‘referst'oithat form of settling
cellulose esters’ and cellulose ethers, said deriv
ative being thinned to a flowable consistency
being present in an amount su?icient to provide
from 0.02 to 30% of silica based on the weight
of said nitrocellulose, said'composition having‘
added. thereto from 0.02 to 0.5% by weight of
dibutyl amine pyrophosphate based on the total
weight of the lacquer composition and su?lcient
to substantially prevent the settling of said
and inorganic aerogels, and a small amount of
pigment suspended therein which tends to settle '
which results in a hard or compact cake, which
is di?icult to redisperse by ordinary means.
i
What I claim is:
1. A lacquer composition comprising a cellulose
derivative selected from the group consisting of
aerogel in the form of a hard cake.
with ‘a solvent therefor, an inorganic pigment
7. A coating composition comprising an organic '
suspended therein which tends to settle in the 10
?lm-forming vehicle thinned to a ?owable' con
form of a hard cake, said pigment being selected
sistency with a solvent therefor,’ an ‘inorganic
from the group consisting of inorganic oxides
in the form of a hard cake, said pigment being
‘dibutyl amine pyrophosphate, said pyrophosphate
selected from the group consisting of inorganic
oxides and inorganic ,aerogels, and a small
amount of an ammonium compound selected
from the group consisting of ammonium‘ and
amine salts of an acid other than salicylic acid,
being present in the amount of not less than
0.0001 mols per 100 c.;c. of said composition and
in anamount su?icient to subsantially prevent
the settling of said pigment in the form of a
hard cake.
<
2. A lacquer composition comprising a cellulose en the basic constituent of said salts having a dis
sociation constant of not less than 1><10-5 and
derivative selected from the group consisting of
the acid constituent of saidv salts having a dis
cellulose esters and cellulose ethers, said deriv
sociation constant of not less than 1><10-4, said
ative being thinned to a ?owable consistency
basic and acid constituents each being‘present
with a solvent-therefor, an inorganic pigment
suspended therein which tends to settle in the _. in the amount of not less than 0.0001 mols per
100 c. c. of said composition and in an amount
form of a hard cake, said pigment being selected
suf?cient to substantially prevent the settling of
from the group consisting of inorganic oxides and
said pigment in the form of a hard cake.
8. A coating composition comprising an organic
?lm-forming vehicle thinned to a ?owable con
sistency with a solvent therefor, and an inorganic
inorganic aerogels, and a small amount of mono
amyl amine citrate, said citrate being present
in the amount of not less than 0.0001 mols per 100 '
c. c. of said composition and in an amount suffi
pigment suspended therein which tends to settle
in the form of a hard cake, said pigment being
selected from the group consisting of inorganic
oxides and inorganicaerogels, said composition
having added thereto small amounts of an am
monic compound selected from the group con
sisting of ammonia and amines and an acid other
than salicylic acid, said ammonic compound hav
cient to substantially prevent the settling of said
pigment in the form of a hard cake.
3. A lacquer composition comprising a cellulose
derivative selected from the group consisting of
cellulose esters and cellulose others, said deriv
ative being thinned to a flowable consistency with
a solvent therefor, an inorganic pigment sus
pended vtherein which tends to settle in the form
of a hard cake, said pigment being selected from 40 ing a dissociation constant of not less than
1><10—5 and said acid having a dissociation con
the group consisting of inorganic oxides'and in
stant of not less than 1>< 10~4, said ammonic com
organic aerogels, and a small amount of triamyl
pound and said acid each being added in the
amine malate, said malate being present in the
amount of not less than 0.0001 mols per, 100 c. c.
amount of not less than 0.0001 mols per 100 c. c.
of said composition and in an amount sufficient
of said composition and in an amount sufficient
to substantially ‘prevent the settling of said pig
to substantially prevent the settling of said pig
ment in the form of a hard cake.
4. The lacquer composition substantially as de
ment in the form of a hard cake.
scribed in claim v1 but further characterized in
that the inorganic pigment contained therein is
an aerogel of an inorganic oxide.
'
GERALD R. BARRETT.
50
'
5. A lacquer composition comprising a cellulose "
derivative selected from the group consisting of
cellulose esters and cellulose ethers, said deriv
' REFERENCES CITED
Thei'following referencep are of record in the
?le of this patent:
a solvent therefor, and silica aerogel, said com
position having added thereto a small amount
of dibutyl amine pyrophosphate, said pyrophos
phate being added in the amount of not less
than 0.0001 mols per 100 c. c. of said composition
and in an amount su?icient to substantially pre
:
“UNITED STATES PATENTS
ative being thinned to a flowable consistency with .
Number
Name
Date
2,245,104
Greubel __________ __ June 10, 1941
2,192,954
Sloan et a1. _.._>______ Mar. 12, 1940
2,192,956
Sloan et a1 ________ _.. Mar. 12, 1940
2,288,413
Morgan __________ __ June30, 1942.
2,192,955
2,126,925
Sloan et'jal ________ __ Mar. 12, 1940
vRyan et a1 ______ __ Aug. 16, 1938
7
2,371,866
6. A lacquer composition comprising nitrocel
65.
lulose thinned to a ?owable consistency with a
. Barrett -1 ________ __ Mar. 20, 1945'
vent the settling of said aerogel in the form of
a hard cake.
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