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Description  |
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BACKGROUND OF THE INVENTION
A coating system gaining wide acceptance, particularly in the automotive
industry, is one which is known as "color plus clear". In this system the
substrate is coated with one or more applications of a pigmented
basecoating composition, which is in turn coated with one or more
applications of a generally clear topcoating composition.
However, there are several difficulties in employing "color plus clear"
coating systems especially as attempts are made to employ coating
compositions having high solids contents and also as metallic flake
pigments are used to provide a special variable appearance to the coated
substrate as it is viewed from different angles to a direction normal to
the surface of the substrate. This variable appearance is sometimes
referred to as "flop" in the coatings industry. For example, it is
important in a "color plus clear" coating system that the applied basecoat
not be attacked by components of the topcoating composition, particularly
solvents, at the interface of the two, a phenomenon often referred to as
strike-in. Strike-in adversely affects the final appearance properties of
the coated product. Strike-in is an especially serious problem when
metallic-flake pigments are employed in the basecoating composition.
Strike-in, among other things, can destroy the desired metallic-flake
orientation in the basecoat.
Additionally, irrespective of the problems associated with strike-in, it is
important to prevent sagging during curing of the coating composition
after application to a nonhorizontal substrate. Also, especially where
metallic-flake pigments are employed, it is important to achieve and
maintain proper pigment orientation in the pigmented basecoating
composition during the curing or drying operation.
One attempt to address some of these problems has been to incorporate in
the basecoating composition as part of the organic polymer system present,
a proportion of organic, insoluble polymer microparticles as described for
example in U.S. Pat. No. 4,220,679 to Backhouse. Another attempt to
address at least some of the problems of achieving proper metallic-flake
orientation in a high solids basecoat has been to substantially increase
the amount of metallic-flake pigment in the basecoating composition as
described in U.S. Pat. No. 4,359,504 to Troy.
It has now been found that the incorporation of an effective amount of an
organo-modified clay in the basecoating composition permits the
basecoating composition to be formulated for example at a high solids
content and alleviates the problems of strike-in, the problems of
achieving excellent metallic-pattern control where metallic-flake pigments
are employed, and the problem of sagging of the coating composition on a
nonhorizontal substrate during curing or drying.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a method for coating a substrate comprising
the steps of: (A) coating the substrate with one or more applications of a
basecoating composition comprising (1) an organic film-forming resin, and
where the film-forming resin can be crosslinked, optionally a crosslinking
agent for the film-forming resin, (2) an organo-modified clay stably
dispersed in the basecoating composition, (3) a solvent system for the
film-forming resin and the optional crosslinking agent for the
film-forming resin, and (4) pigment particles, to form a basecoat, and
optionally before allowing the basecoating composition to become
substantially cured or hardened; (B) coating the basecoat with one or more
applications of a topcoating composition comprising (1) an organic
film-forming resin, which may be the same or different from the
film-forming resin of the basecoating composition, and where the
film-forming resin of the topcoating composition can be crosslinked,
optionally a crosslinking agent for the film-forming resin of the
topcoating composition, and (2) a solvent system for the organic
film-forming resin of the topcoating composition and the optional
crosslinking agent for the film-forming resin of the topcoating
composition, to form a transparent topcoat.
DETAILED DESCRIPTION OF THE INVENTION
The film-forming resin of the basecoating composition may be any of the
film-forming resins useful for coating compositions. The film-forming
resins of the basecoating composition can be film-forming thermoplastic
resins and/or thermosetting resins. Examples of such film-forming
thermoplastic resins and/or thermosetting resins include the generally
known cellulosics, acrylics, aminoplasts, urethanes, polyesters, epoxies,
and polyamides. These resins, when desired, may also contain functional
groups characteristic of more than one class, as for example, polyester
amides, uralkyds, urethane acrylates, urethane amide acrylates, etc. As
indicated above, the film-forming resin may be thermoplastic or it may be
thermosetting. As used herein, the term thermosetting is intended to
include not only those resins capable of being crosslinked upon
application of heat but also those resins which are capable of being
crosslinked without the application of heat. In preferred embodiments of
the present invention, the film-forming resin of the basecoating
composition is selected from thermosetting acrylic resins and
thermosetting polyester resins.
Cellulosics refer to the generally known thermoplastic polymers which are
derivatives of cellulose, examples of which include: nitrocellulose;
organic esters and mixed esters of cellulose such as cellulose acetate,
cullulose propionate, cellulose butyrate, and cellulose acetate butyrate;
and organic ethers of cellulose such as ethyl cellulose.
Acrylic resins refer to the generally known addition polymers and
copolymers of acrylic and methacrylic acids and their ester derivatives,
acrylamide and methacrylamide, and acrylonitrile and methacrylonitrile.
Examples of ester derivatives of acrylic and methacrylic acids include
such alkyl acrylates and alkyl methacrylates as ethyl, methyl, propyl,
butyl, hexyl, ethylhexyl and lauryl acrylates and methacrylates, as well
as similar esters, having up to about 20 carbon atoms in the alkyl group.
Also, hydroxyalkyl esters can readily be employed. Examples of such
hydroxyalkyl esters include 2-hydroxyethyl acrylate, 2-hydroxypropyl
acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,
3-hydroxypropyl-4-hydroxybutyl methacrylate, and mixtures of such esters
having up to about 5 carbon atoms in the alkyl group. In some instances,
corresponding esters of other unsaturated acids, for example, ethacrylic
acid, crotonic acid, and other similar acids having up to about 6 carbon
atoms can be employed. Where desired, various other ethylenically
unsaturated monomers can be utilized in the preparation of arylic resins
examples of which include: vinyl aromatic hydrocarbons optionally bearing
halo substituents such as styrene, alphamethyl styrene, vinyl toluene,
alpha-chlorostyrene, alpha-bromostyrene, and para-fluorostyrene;
nonaromatic monoolefinic and diolefinic hydrocarbons optionally bearing
halo substituents such as isobutylene, 2,3-dimethyl-1-hexene,
1,3-butadiene, chloroethylene, chlorobutadiene and the like; unsaturated
organosilanes such as gamma-methacryloxypropyltriethoxysilane,
gamma-acryloxypropyltriethoxysilane, vinyltrimethoxysilane and the like;
esters of organic and inorganic acids such as vinyl acetate, vinyl
propionate, and isopropenyl acetate; and vinyl chloride, allyl chloride,
vinyl alpha-chloroacetate, dimethyl maleate and the like.
The above polymerizable monomers are mentioned as representative of the
##STR1##
containing monomers which may be employed; but essentially any
copolymerizable monomer can be used.
Aminoplast resins refer to the generally known condensation products of an
aldehyde with an amino- or amido-group containing substance examples of
which include the reaction products of formaldehyde, acetaldehyde,
crotonaldehyde, benzaldehyde and mixtures thereof with urea, melamine, or
benzoguanimine. Preferred aminoplast resins include the etherified (i.e.,
alkylated) products obtained from the reaction of alcohols and
formaldehyde with urea, melamine, or benzoguanimine. Examples of suitable
alcohols for preparing these etherified products include: methanol,
ethanol, propanol, butanol, hexanol, benzylalcohol, cyclohexanol,
3-chloropropanol, and ethoxyethanol.
Urethane resins refer to the generally known thermosetting or thermoplastic
urethane resins prepared from organic polyisocyanates and organic
compounds containing active hydrogen atoms as found for example in
hydroxyl, and amino moieties. Some examples of urethane resins typically
utilized in one-pack coating compositions include: the isocyanate-modified
alkyd resins sometimes referred to as "uralkyds"; the isocyanate-modified
drying oils commonly referred to as "urethane oils" which cure with a
drier in the presence of oxygen in air; and isocyanate-terminated
prepolymers typically prepared from an excess of one or more organic
polyisocyanates and one or more polyols including, for example, simple
diols, triols and higher alcohols, polyester polyols and polyether
polyols. Some examples of systems based on urethane resins typically
utilized as two-pack coating compositions include an organic
polyisocyanate or isocyanate-terminated prepolymer (first pack) in
combination with a substance (second pack) containing active hydrogen as
in hydroxyl or amino groups along with a catalyst (e.g., an organotin salt
such as dibutyltin dilaurate or an organic amine such as triethylamine or
1,4-diazobicyclo-(2:2:2) octane). The active hydrogen-containing substance
in the second pack typically is a polyester polyol, a polyether polyol, or
an acrylic polyol known for use in such two-pack urethane resin systems.
Many coating compositions based on urethanes (and their preparation) are
described extensively in Chapter X Coatings, pages 453-607of
Polyurethanes: Chemistry and Technology, Part II by H. Saunders and K. C.
Frisch, Interscience Publishers (N.Y., 1964).
Polyester resins are generally known and are prepared by conventional
techniques utilizing polyhydric alcohols and polycarboxylic acids.
Examples of suitable polyhydric alcohols include: ethylene glycol;
propylene glycol; diethylene glycol; dipropylene glycol; butylene glycol;
glycerol; trimethylolpropane; pentaerythritol; sorbitol; 1,6-hexanediol;
1,4-cyclohexanediol; 1,4-cyclohexanedimethanol;
1,2-bis(hydroxyethyl)cyclohexane; and
2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate. Examples of
suitable polycarboxylic acids include: phthalic acid; isophthalic acid;
terephthalic acid; trimellitic acid; tetrahydrophthalic acid;
hexahydrophthalic acid; tetrachlorophthalic acid; adipic acid; azelaic
acid; sebacic acid; succinic acid; maleic acid; glutaric acid; malonic
acid; pimelic acid; suberic acid; 2-2-dimethylsuccinic acid;
3,3-dimethylglutaric acid; 2,2dimethylglutaric acid; maleic acid; fumaric
acid; and itaconic acid. Anhydrides of the above acids, where they exist,
can also be employed and are encompassed by the term "polycarboxylic
acid." In addition, certain substances which react in a manner similar to
acids to form polyesters are also useful. Such substances include lactones
such as caprolactone, propylolactone and methyl caprolactone, and hydroxy
acids such as hydroxy caproic acid and dimethylol propionic acid. If a
triol or higher hydric alcohol is used, a monocarboxylic acid, such as
acetic acid and benzoic acid may be used in the preparation of the
polyester resin. Moreover, polyesters are intended to include polyesters
modified with fatty acids or glyceride oils of fatty acids (i.e.,
conventional alkyd resins) Alkyd resins typically are produced by reacting
the polyhydric alcohols, polycarboxylic acids, and fatty acids derived
from drying, semi-drying, and non-drying oils in various proportions in
the presence of a catalyst such as litharge, sulfuric acid, or a sulfonic
acid to effect esterification. Examples of suitable fatty acids include
saturated and unsaturated acids such as stearic acid, oleic acid,
ricinoleic acid, palmitic acid, linoleic acid, linolenic acid, licanic
acid, elaeostearic acid, and clupanodonic acid.
Epoxy resins, often referred to simply as "epoxies", are generally known
and refer to compounds or mixtures of compounds containing more than one
1,2-epoxy group of the formula
##STR2##
i.e., polyepoxides. The polyepoxides may be saturated or unsaturated,
aliphatic, cycloaliphatic, aromatic or heterocyclic. Examples of suitable
polyepoxides include the generally known polyglycidyl ethers of
polyphenols and/or polyepoxides which are acrylic resins containing
pendant and/or terminal 1,2-epoxy groups. Polyglycidyl ethers of
polyphenols may be prepared, for example, by etherification of a
polyphenol with epichlorohydrin or dichlorohydrin in the presence of an
alkali. Examples of suitable polyphenols include:
1,1-bis(4-hydroxyphenyl)ethane; 2,2-bis(4-hydroxyphenyl)propane;
1,1-bis(4hydroxyphenyl)isobutane;
2,2-bis(4-hydroxytertiarybutylphenyl)propane;
bis(2-hydroxynaphthyl)methane; 1,5-dihydroxynaphthalene;
1,1-bis(4-hydroxy-3-allylphenyl)ethane; and the hydrogenated derivatives
thereof. The polyglycidyl ethers of polyphenols of various molecular
weights may be produced, for example, by varying the mole ratio of
epichlorohydrin to polyphenol in known manner.
Epoxy resins also include the polyglycidyl ethers of mononuclear polyhydric
phenols such as the polyglycidyl ethers of resorcinol, pyrogallol,
hydroquinone, and pyrocatechol.
Epoxy resins also include the polyglycidyl ethers of polyhydric alcohols
such as the reaction products of epichlorohydrin or dichlorohydrin with
aliphatic and cycloaliphatic compounds containing from two to four
hydroxyl groups including, for example, ethylene glycol, diethylene
glycol, triethylene glycol, dipropylene glycol, tripropylene glycol,
propane diols, butane diols, pentane diols, glycerol, 1,2,6-hexanetriol,
pentaerythritol, and 2,2-bis(4-hydroxycyclohexyl)propane.
Epoxy resins additionally include polyglycidyl esters of polycarboxylic
acids such as the generally known polyglycidyl esters of adipic acid,
phthalic acid, and the like.
Addition polymerized resins containing epoxy groups may also be employed.
These polyepoxides may be produced by the addition polymerization of epoxy
functional monomers such as glycidyl acrylate, glycidyl methacrylate and
allyl glycidyl ether optionally in combination with ethylenically
unsaturated monomers such as styrene, alpha-methyl styrene, alpha-ethyl
styrene, vinyl toluene, t-butyl styrene, acrylamide, methacrylamide,
acrylonitrile, methacrylonitrile, ethacrylonitrile, ethyl methacrylate,
methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, and
isobornyl methacrylate.
Many additional examples of epoxy resins are described in the Handbook of
Epoxy Resins, Henry Lee and Kris Neville, 1967, McGraw Hill Book Company.
When desired, generally known crosslinking agents may be utilized in the
method of the invention particularly when thermosetting resins containing
active hydrogen atoms, for example, from moieties such as hydroxyl,
carboxyl, amino, and amido, are employed in the coating compositions.
As will be appreciated by one skilled in the art, the choice of
crosslinking agent depends on various factors such as compatibility with
the film-forming resin, the particular type of functional groups on the
film-forming resin and the like. The crosslinking agent may be used to
crosslink the film-forming resin either by condensation or addition or
both. When the thermosetting reactants include monomers having
complementary groups capable of entering into crosslinking reactions, the
crosslinking agent may be omitted if desired.
Representative examples of crosslinking agents include blocked and/or
unblocked diisocyanates, diepoxides, aminoplasts, phenoplasts, and silane
crosslinking agents. When aminoplast resins are employed as crosslinking
agents, particularly suitable are the melamine-formaldehyde condensates in
which a substantial proportion of the methylol groups have been etherified
by reaction with a monohydric alcohol such as those set forth previously
in the description of aminoplast resins suitable for use as film-forming
resins in compositions of the invention.
The term "solvent system" as used herein, for example in the phrase
"solvent system for the film-forming resin and optional crosslinking
agent", is employed in a broad sense and is intended to include true
solvents as well as liquid diluents for the film-forming resin and for the
optional crosslinking agent which are not true solvents for these
components. The solvent system generally is organic. It may be a single
compound or a mixture of compounds. Ordinarily the solvent system does not
comprise water. However when the solvent system does comprise both water
and an organic portion, the components are usually miscible in the
proportions employed. The relationship between the solvent system and the
film-forming resin, and also between the solvent system and the
organo-modified clay (described infra), depends upon the absolute and
relative natures of these materials and upon the relative amounts used.
Such factors as solubility, miscibility, polarity, hydrophilicity,
hydrophobicity, lyophilicity and lyophobicity are some of the factors
which may be considered. Illustrative of suitable components of the
solvent system which may be employed are alcohols such as lower alkanols
containing 1 to 8 carbon atoms including methanol, ethanol, propanol,
isopropanol, butanol, secondary-butyl alcohol, tertiary-butyl alcohol,
amyl alcohol, hexyl alcohol and 2-ethylhexyl alcohol; ethers and ether
alcohols such as ethylene glycol monoethyl ether, ethylene glycol
monobutyl ether, ethylene glycol dibutyl ether, propylene glycol
monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol
dibutyl ether, dipropylene glycol monoethyl ether, and dipropylene glycol
monobutyl ether; ketones such as acetone, cyclohexanone, methyl ethyl
ketone, methyl isobutyl ketone, methyl amyl ketone and methyl N-butyl
ketone; esters such as ethyl acetate, butyl acetate, 2-ethoxyethyl acetate
and 2-ethylhexyl acetate; aliphatic and alicyclic hydrocarbons such as the
various petroleum naphthas and cyclohexane; aromatic hydrocarbons such as
benzene, ethyl benzene, toluene and xylene; chlorinated hydrocarbon
solvents such as methylene chloride, chloroform, carbontetrachloride,
chloroethane, and 1,1,1-trichloroethane; and water.
As will be appreciated by one skilled in the art, the organic solvents,
examples of which have been described previously, suitable for the solvent
system in the method of the present invention may be broadly classified
into five categories which include aliphatic, aromatic, moderately polar,
highly polar and chlorinated solvents. Essentially nonpolar aliphatic
solvents include normal and branched chain aliphatic hydrocarbons having
from about 5 to 12 carbon atoms and cycloaliphatic compounds. Essentially
nonpolar aromatic solvents include such materials as benzene, toluene,
xylene and ethyl benzene. Moderately polar solvents include ketonic and
ester solvents such as acetone, methylethylketone, methylbutylketone,
methylisobutylketone, cyclohexanone, ethyl acetate, butyl acetate,
ethoxyethyl acetate, and the like. Highly polar solvents include such
materials as low molecular weight alcohols such as methanol, ethanol,
propanol, 2-propanol, butanol, 2-butanol, and ethoxyethanol. Chlorinated
hydrocarbon solvents include such materials as methylene chloride,
chloroform, carbon tetrachloride, chloroethane and 1,1,1-trichloroethane.
The basecoating composition also contains a pigment. Examples of opacifying
pigments include titanium dioxide (rutile or anatase), zinc oxide,
zirconium oxide, zinc sulfide, and lithopone. Examples of coloring
pigments include iron oxides, cadmium sulfide, carbon black,
phthalocyanine blue, phthalocyanine green, indanthrone blue, ultramarine
blue, chromium oxide, burnt umber, benzidine yellow and toluidine red.
Examples of reactive pigments include silicate-treated barium metaborate,
strontium chromate and lead chromate. Examples of extender pigments
include pigmentary silica, barytes, calcium carbonate, barium sulfate,
talc, aluminum silicates, sodium aluminum silicates, potassium aluminum
silicates and magnesium silicates. Metallic pigments include metallic
powders and metallic flakes. Examples of metallic powders include aluminum
powder, copper powder, bronze powder and zinc dust. Examples of metallic
flakes include aluminum flakes, nickel flakes, copper flakes, bronze
flakes, brass flakes and chromium flakes. A single pigment may be used or
mixtures of pigments may be employed. It is preferred that at least a
portion of the pigment particles be metallic flakes. The metallic flakes
usually comprise aluminum flakes.
The principles respecting the formation of solutions, dispersions,
pseudodispersions, and emulsions of film-forming resins are generally
known in the art. Any of these systems may be utilized in the basecoating
and/or topcoating composition.
The method of the invention requires that an organo-modified clay be
employed in the basecoating composition. The organo-modified clays which
are suitable in the method of the present invention are produced from the
reaction of an organic cation, organic anion and smectite-type clay. The
clays used to prepare these organo-modified clays suitable for the process
of the present invention are smectite-type clays which have a cation
exchange capacity of at least 75 milliequivalents per 100 grams of clay.
Particularly desirable types of clay are the naturally occurring Wyoming
varieties of swelling bentonites and like clays and hectorite, a swelling
magnesium-lithium silicate clay.
The clays, especially the bentonite type clays, are preferably converted to
the sodium form if they are not already in this form. This can
conveniently be done by preparing an aqueous clay slurry and passing the
slurry through a bed of cation exchange resin in the sodium form.
Alternatively, the clay can be mixed with water and a soluble sodium
compound such as sodium carbonate, sodium hydroxide and the like, followed
by shearing the mixture with a pugmill or extruder.
Smectite-type clays prepared naturally or synthetically by either a
pneumatolytic or, preferably a hydrothermal synthesis process can also be
used to prepare the organophilic, organo-modified clays suitable for the
present invention. Representative of such clays are montmorillonite,
bentonite, beidellite, hectorite, saponite, and stevensite. These clays
may be synthesized hydrothermally by forming an aqueous reaction mixture
in the form of a slurry containing mixed hydrous oxides or hydroxides of
the desired metal with or without, as the case may be, sodium (or
alternate exchangeable cation or mixture thereof) fluoride in the
proportions for the particular synthetic smectite desired. The slurry is
then placed in an autoclave and heated under autogenous pressure to a
temperature within the range of approximately 100.degree. to 325.degree.
C., preferably 274.degree. to 300.degree. C., for a sufficient period of
time to form the desired product.
The cation exchange capacity of the smectite-type clays can be determined
by the well-kown ammonium acetate method.
Organo-modified clays of one preferred type which do not require the
addition of polar solvent activators (such as acetone, alcohols and the
like) for use in the method of the present invention are produced from the
reaction of the smectite-type clay with an organic cation and an organic
anion described below. Additional description may be obtained from U.S.
Pat. No. 4,412,018 which is hereby incorporated by reference.
The organic cationic compounds which are useful in preparing these
preferred organo-modified clays suitable for the method of the present
invention may be selected from a wide range of materials which are capable
of forming an organophilic clay by exchange of cations with the
smectite-type clay. The organic cationic compound generally has a positive
charge localized on a single atom or on a small group of atoms within the
compound. Preferably the organic cation is selected from the group
consisting of quaternary ammonium salts, phosphonium salts, sulfonium
salts and mixtures thereof wherein the organic cation contains at least
one lineal or branched alkyl group having 12 to 22 carbon atoms. The
remaining moieties on the central positively charged atoms are chosen from
(a) lineal or branched alkyl groups having 1 to 22 carbon atoms; (b)
aralkyl groups, that is benzyl and substituted benzyl moieties including
fused ring moieties having lineal or branched alkyl groups having 1 to 22
carbon atoms in the alkyl portion of the structure; (c) aryl groups such
as phenyl and substituted phenyl including fused ring aromatic
substituents; and (d) hydrogen.
The long chain alkyl radicals containing at least one group having 12 to 22
carbon atoms may be derived from naturally occurring oils including
various vegetable oils, such as corn oil, coconut oil, soybean oil,
cottonseed oil, castor oil and the like, as well as various animal oils or
fats such as tallow oil. The alkyl radicals may likewise be
petrochemically derived such as from alpha olefins. Additional exemplary
radicals include methyl, ethyl, decyl, lauryl, and stearyl.
Additional examples of aralkyl groups, that is benzyl and substituted
benzyl moieties would include those materials derived from, e.g. benzyl
halides, benzhydryl halides, trityl halides, alpha-halo-alphaphenylalkanes
wherein the alkyl chain has from 1 to 22 carbon atoms such as
1-halo-1-phenylethane, 1-halo-1-phenyl propane, and
1-halo-1-phenyloctadecane; substituted benzyl moieties such as would be
derived from ortho, meta and para-chlorobenzyl halides, para-methoxybenzyl
halides, ortho, meta and para-methoxybenzyl halides, ortho, meta and
para-nitrilobenzyl halides, and ortho, meta and para-alkylbenzyl halides
wherein the alkyl chain contains from 1 to 22 carbon atoms; and fused ring
benzyl-type moieties such as would be derived from
2-halomethylnaphthalene, 9-halomethylanthracene and
9-halomethylphenanthrene, wherein the halo group would be defined as
chloro, bromo, iodo, or any other such group which serves as a leaving
group in the nucleophilic attack of the benzyl type moiety such that the
nucleophile replaces the leaving group on the benzyl type moiety.
Examples of aryl groups would include phenyl such as in N-alkyl and
N,N-dialkyl anilines, wherein the alkyl groups contain between 1 and 22
carbon atoms; ortho, meta and para-nitrophenyl, ortho, meta and para-alkyl
phenyl, wherein the alkyl group contains between 1 and 22 carbon atoms,
2-, 3-, and 4-halophenyl wherein the halo group is defined as chloro,
bromo, or iodo, and 2-, 3-, and 4-carboxyphenyl and esters thereof, where
the alcohol of the ester is derived from an alkyl alcohol, wherein the
alkyl group contains between 1 and 22 carbon atoms, aryl such as a phenol,
or aralkyl such as benzyl alcohols; fused ring aryl moieties such as
naphthalene, anthracene, and phenanthrene.
Many processes are known to prepare organic cationic salts. For example
when preparing a quaternary ammonium salt one skilled in the art would
prepare a dialkyl secondary amine, for example, by the hydrogenation of
nitriles, see U.S. Pat. No. 2,355,356; form the methyl dialkyl tertiary
amine by reductive alkylation using formaldehyde as the source of methyl
radical. Also see Shapiro et al U.S. Pat. No. 3,136,819 for forming the
quaternary amine halide by adding benzyl chloride or benzyl bromide to the
tertiary amine as well as Shapiro et al U.S. Pat. No. 2,775,617. The salt
anion is preferably selected from the group consisting of chloride and
bromide, and mixtures thereof, and is more preferably chloride, although
other anions such as acetate, hydroxide, nitrite, etc., may be present in
the organic cationic compound to neutralize the cation.
These organic cationic compounds can be represented by the formulas:
##STR3##
wherein X is nitrogen or phosphorus, Y is sulfur, M.sup.- is selected from
the group consisting of chloride, bromide, iodide, nitrite, hydroxide,
acetate, methyl sulfate, and mixtures thereof; and wherein R.sub.1 is an
alkyl group having 12 to 22 carbon atoms; and wherein R.sub.2, R.sub.3 and
R.sub.4 are selected from the group consisting of hydrogen; alkyl groups
containing 1 to 22 carbon atoms; aryl groups; aralkyl groups containing 1
to 22 carbon atoms on the alkyl chain, and mixtures thereof.
The organic anions useful in preparing these preferred organo-modified
clays suitable for the method of the present invention may be selected
from a wide range of materials providing they are capable of reacting with
the above-described organic cation and form intercalations with a
smectite-type clay as an organic cation-organic | | |
