Note: Descriptions are shown in the official language in which they were submitted.
~6234Q
BACKGROUND OF TH~ INVENTION
Emulsion polymerization probably had its origin in the observations
by early scientists of natural latexes or saps exuded by many plants. The most
important of these is without a doubt, natural Tubber latex. Natural rubber is
a milklike collodial dispersion in water of polyisoprene particles protected
from coagulation by natural proteins and emulsifiers. The earliest reference
to emulsion polymerization is made in German patent DRP 250690 in 1909. Work
on emulsion polymerization continued in Germany through World War I with
relatively little progress being made in the technical development. Industrial
development of emulsion polymerization appears to have started toward the end
of the 1920's. In German Patent DRP 558,890 ~1927) there is described the
polymerization of butadiene to a synthetic latex using soaps as emulsifiers and
hydrogen peroxide as the initiator.
The first significant breakthrough in the industrial development of
emulsion polymerization occurred in 1938 when it was shown that polymerization
occurs in the aqueous phase and not in the monomer droplets. Understanding the
mechanism of the emulsion polymerization widened knowledge so that predictions
and improvements of the techniques could be made.
The advantages of emulsion polymerization over other methods such as
bulk or solution polymerization are as follows:
~ 1) An emulsion polymerized product, i.e. the latex itself, is in
an ideal form for use in paints and surface coatings, adhesives, paper coating
and impregnation, leather treatment, textile treatment, dipping and latex foam
rubber.
(2) Control of the initiator, propagation, chain transfer, and
termination reaction is easy and, in most cases, at a relatively low polymeri-
zation temperature. -.~!C~
~6234~
(3) Emulsion polymerization lends itself to easy continuous process
operation .
~ 4) ~ligh rates of polymerization can be obtained simultaneously with
high degrees of polymerization.
(5) In contrasts to solutions of polymers, the viscosity of a latex
is independent of the molecular weight of the polymer it contains. Thus high
polymer concentrations can be obtained at low viscosity.
(6) Emulsion polymerization uses water as tne inexpensive solvent
eliminating solvent recovery problems and fire risk factors.
(7) When a solid product is required work up of the polymer presents
no problems since the latex is simply coagulated in an appropriate manner and
the coagulated crumb washed with water of other aqueous solutions, pressed and
dried.
It has been said that the choice of an emulsifier is probably the
most important single factor in an emulsion polymerization recipe. First, the
emulsifier must produce a stable emulsion between the monomer and water phases
and later a stable latex. Second, it must not interfere adversely with the
initiation system or the propagation of the reaction. Third, since the
emulsifier residues will remain in the product recovered after polymerization
it must impart no adverse properties to the product.
Numerous synthetic emulsifiers have been studied for their efficiency
in emulsion polymerization. ~ccording to the nature of the hydrophilic groups,
surface active agents can be divided into four classes: (a) anionic,
(b) cationic, (c) amphoteric, and (d) nonionic. Each of these main groups can
be further subdivided chemically according to the hydrophilic group (e.g.
carboxylic acids, sulfates, sulfonates) and according to the hydrophobic group
(e.g. alkyl, alkylaryl, alkylamide, alkylester). Thus the choice from the
o
number of possible permutations and combinations is very wide.
Illustrative of suitable surfactants commonly employed in emulsion
polymerization processes of the prior art are the anionic surfactants such as
potassium caprylate, potassium myristate, potassium palmitate, potassium
stearate, potassium oleate, sodium decyl sulfonate, sodium dodecyl sulfonate,
sodium tetradecyl sulfate, sodium decyl sulfate, sodium lauryl sulfate, potassium
dehydroabietate, sodium rosinate, alkyl sodium sulfosuccinate esters and the
like; cationic surfactants such as the long chain quaternary amine salts; and
nonionic surfactants such as ethylene oxide condensates of oleyl alcohol, cetyl
alcohol, lauryl alcohol etc., ethylene oxide condensates of linoleic acid,
lauric acid, ricinoleic acid, caproic acid, etc., block copolymer of ethylene
oxide and propylene oxide and the ethylene oxide condensates of octyl phenol or
nonyl phenol.
The role of the emulsifier in emulsion polymerization is threefold:
(a) an increased amount of the monomer is taken into the water phase owing to
solubilization in the micelles; (b) the nonsolubilized monomer is emulsified
into fine stable droplets; and (c) the latex particles created are protected
against coagulation during and after the polymerization.
It is known that different emulsifiers have molar concentrations
below which no micelle formation occurs. This is the critical micelle concen-
tration, i.e., cmc. In most cases no polymerization of significance occurs
below the critical micelle concentration (cmc). As the concentration of the
emulsifier is lowered, the number of latex particles formed is decreased. It
is known that emulsifier residue left in the latex system can leave the latex
with undesirable properties, i.e., the latex may lose some of its stability.
It has been recognized that an emulsifier should bring three basic
properties to a latex system. These properties are (a) good solubility at
the polymerization temperature, (b) good solubilizing power, and (c) imparting
good stability to the latex. Further, the emulsifier must not interfere with
the initiation or the propagation of the polymerization reactions.
The variety of initiator systems in emulsion polymerization processes
is no less than the variety of emulsifiers described. All systems used
commercially are based on the liberation of an active free radical. These
active free radicals are produced by either of two means la) thermal decomposi-
tion of a compound into free radicals or (b) interaction of chemical agents to
produce free radicals.
The most commonly used initiators are those compounds containing a
peroxide bond, i.e., -0-0-. The organic peroxides can be regarded as being
derived from hydrogen peroxide by replacement of hydrogens by organic groups.
Some specific organic peroxide initiators are diisopropyl peroxycarbon-
ate, caprylyl peroxide, lauroyl peroxide, benzoyl peroxide, dicumyl peroxide,
tert-butyl hydroperoxide, methyl ethyl ketone peroxide, di-tert-butyl peroxide,
cumene peroxide and tert-butyl peroxybenzoate. Compounds that release peroxydi-
sulfate ions may also be used as an initiator.
Hydrogen peroxide-iron systems can be used as the initiators for the
polymerization of certain monomers, e.g. methyl methacrylate and acrylonitrile
while the organic hydroperoxides are preferred for the less polar monomers such
as styrene and butadiene. For the manufacture of "cold" SBR recipes containing
p-methane hydroperoxide, pinone hydroperoxide, or diiosopropylbenzene hydro-
peroxide are most frequently encountered.
In addition emulsifiers and initiators, certain materials may be added
to the emulsion polymerization reaction mixture to retard or inhibit the pro-
pagation reaction. Any substances which will trap free radicals and either
destroy them, prevent them from getting to the locus of polymerization, or
~1 ~4l~
produce by transfer another free radical which is not active as a polymerizationinitiators or inhibitors may be used. Some substances may act as both retarder
and an inhibitor. Some commonly used substances are diethylhydroxylamine,
hydroquinone, methylether of hydroquinone, p-aminophenol, water soluble dithio-
carbamates, etc.
The Invention
This application claims a process and the latices produced thereby
where the conventional surface active agents and/or emulsifiers are replaced
by a polyurethane prepolymer amine salt. This polyurethane prepolymer amine
salt eliminates the effects of the residues in the finished product by the
emulsifier remaining therein since the salt upon curing of the latex becomes a
part of the cured latex.
The no~el polyurethane prepolymer amine salt when used in emulsion
polymerization systems has been found to act as a particle initiator and thus
can be substituted for seed latex used in preparing latex compositions where a
high degree of uniformity in particle size is required (for example see United
States Patent 3,397,165). It has been found that the novel polyurethane pre-
polymer amine salt when used in an emulsion polymerization system acts as a
stabilizing medium for the latex system.
In the process of this invention latex initiation is performed in
accordance with the procedures known in the art. The aqueous reaction medium
is charged to the reaction zone and the monomer or monomers to be polymerized
are thereafter fed continuously to the aqueous medium in the reaction zone
together with a catalyst and, if desired, surfactants, buffer, etc. By the term
"aqueous reaction medium" is meant water plus any o~her constituents, e.g.
catalyst, surfactants, buffer, etc. which are present in the reaction zone in
which the polymerization of this process is carried out. The temperature of
34~
initiation varies depending on the type of monomers used and the amount and
type of catalyst used, and those skilled in the art will know the correct
initiation temperature for any given system. Typically, when polymerizing
lower alkyl acrylate or methacrylate monomers, e.g. methyl methacrylate, N-
butyl acrylate, etc., it is preferred to initiate polymerization at a temperature
of from about 40 to about 84C depending on the catalyst employed.
Any reactor, properly equipped, can be used in the carrying out of
emulsion polymerization reactions. The different types of reactors and their
suitability for emulsion polyerization are well known to those skilled in the
art. Typically, a stirred tank with means for controlling temperature and
pressure, means for providing a continuous feed of the monomer, catalyst,
surfactant, buffer, etc., means for continuously withdrawing a portion of the
tank's contents, and, where desired, means for providing an inert atmosphere
(e.g. N2) above the reactants, is suitably employed as the reactor.
The emulsion polymerizable monomers which are useful in the process
of our invention are any of the monomers having at least one olefinically
unsaturated group of the formula
C=C
which are known to those skilled in the art to undergo addition polymerization
under the conditions of emulsion polymerization in an aqueous medium. These
monomers are so well known to those skilled in the art as to require no further
elaboration herein. Nonetheless, one can mention as illustrative thereof,
unsaturated compounds such as ethylene, propylene, l-butene, 2-butene, isobutyl-
ene, l-pentene, 2-methyl-2-butene, l-hexene, 4-methyl-1-pentene, 3,3-dimethyl-
l-butene, 2,4,4-trimethyl-1-pentene, 6-ethyl-1-hexene, l-heptene, l-octene,
l-decene, l-dodecene, allene, butadiene, isoprene, chloroprene, l,5-hexadiene,
-- 6 --
1~34~
1,3,5-hextriene, divinylacetylene, cyclopentadiene, dicyclopentadiene, norbornene,
norbornadiene, methylnorbornene, cyclohexene, styrene, alpha-chlorostyrene,
alphamethylstyrene, allylbenzene, phenylacetylene, l-phenyl-l, 3-butadiene
vinylnaphthalene, 4-methylstyrene, 2,4-dimethylstyrene, 3-ethylstyrene, 2,4-
diethylstyrene, 2-methoxystyrene, 4~methoxy-3-methylstyrene, 4-chlorostyrene,
3,4-dimethyl-alpha-methylstyrene, 3-bromo-4-methyl-alpha-methylstyrene, 2,5-
dichlorostyrene, 4-fluorostyrene, 3-iodostyrene, 4-cyanostyrene, 4-vinylbenzoic
acid, 4-acetoxystyrene, 4-vinyl benzyl alcohol, 3-hydroxystyrene, 1,4-dihyroxy-
styrene, 3-hydroxystyrene 1,4-dihydroxystyrene, 3-nitrostyrene, 2-aminostyrene,
4-N,N-dimethylaminostyrene, 4-phenylstyrene, 4-chloro-1-vinylnaphthalene,
acrylic acid, methacrylic acid, acrolein, methacrolein, acrylonitrile~ meth-
acrylonitrile, acrylate, methacrylamide methyl acrylate, methyl methacrylate,
norbornenyl acrylate, norbornyl diacrylate, 2-hydroxyethyl acrylate, 2-phenoxy-
ethyl acrylate, trimethoxysilyloxypropyl acrylate, dicyclopentenyl acrylate,
cyclohexyl acrylate, 2-tolyloxyethyl acrylate, N,N-dimethylacrylamide, isopropyl
methacrylate, ethyl acrylate, methyl alpha-chloroacrylate, betadimethylamino-
ethyl methacrylate, N-methyl methacrylamide, ethyl methacrylate, 2-ethylhexyl
acrylate, neopentyl glycol diacrylate, cyclohexyl methacrylate, beta-bromoethyl
methacrylate, benzyl methacrylate, phenol methacrylate, neopentyl methacrylate,
butyl methacrylate, chloroacrylic acid, methyl chloroacrylic acid, hexyl acrylate,
dodecyl acrylate, 3-methyl l-butyl acrylate, 2-ethoxyethyl acrylate, phenyl
acrylate, butoxyethoxyethyl acrylate, 2-methoxyethyl acrylate, isodecyl acrylate,
pentaerythritol triacrylate, methoxy poly (ethyleneoxy) acrylate, tridecoxy
: poly (ethyleneoxy) acrylate, chloroacrylonitrile, dichloroisopropyl acrylate,
ethacrylonitrile, N-phenyl acrylamide, N,N-diethylacrylamide, N-cyclohexyl
acrylamide, vinyl chloride, vinylidene chloride, vinylidene cyanide, vinyl
fluoride, vinylidene fluoride, trichlorethene, vinyl acetate, vinyl propionate,
vinyl butyrate, vinyl benzoate, vinyl butyral, vinyl propionate, vinyl chloro-
acetate, isopropenyl acetate, vinyl formate, vinyl methoxyacetate, vinyl
caproate, vinyl oleate, vinyl adipate, methyl vinyl ketone, methyl isopropenyl
ketone, vinyl phenyl ketone, methyl alpha-chlorovinyl ketone, ethyl vinyl
ketone, divinyl ketone, allylidene diacetate, methyl vinyl ether, 2-methoxy-
ethyl vinyl ether, 2-chloroethyl vinyl ether, methoxyethoxy ethyl vinyl ether,
hydroxyethyl vinyl ether, aminoethyl vinyl ether, alpha-methylvinyl methyl
ether, divinyl ether, divinyl ether of ethylene glycol or diethylene glycol or
triethanolamine, cyclohexyl vinyl ether, benzyl vinyl etherJ phenethyl vinyl
ether, cresyl vinyl etherJ hydroxyphenyl vinyl etherJ chlorophenyl vinyl etherJ
napthyl, vinyl ether, dimethyl maleate, diethyl maleate, di-(2-ethylhexyl)
maleate, maleic anhydride, dimethyl fumarate, dipropyl fumarate, diamyl
fumarate, vinyl ethyl sulfide, divinyl sulfide, vinyl p-tolyl sulfide, divinyl
sulfone, vinyl ethyl sulfoneJ vinyl ethyl sulfoxideJ vinyl sulfonic acidJ
sodium vinyl sulfonate, vinyl sulfonamide, vinyl benzamide, vinyl pyridineJ
N-vinyl pyrollidoneJ N-vinyl carbazole, N-(vinyl benzyl)-pyrrolidiene, N-(vinyl
benzyl) piperidine, l-vinyl pyrene, 2-isopropenyl furanJ 2-vinyl dibenzofuran,
2-methyl-5-vinyl-pyridineJ 3-isopropenyl pyridineJ vinyl piperidineJ 2-vinyl
quinoline, 2-vinyl benzoxazoleJ 4-methyl-5-vinyl-thiazoleJ vinyl thiopheneJ
2-isopropenyl thiopheneJ indeneJ coumaraone, l-chloroethyl vinyl sulfide, vinyl
2-ethoxyethyl sulfideJ vinyl phenyl sulfideJ vinyl 2-naphthyl sulfideJ allyl
mercaptans, divinyl sulfoxide, vinyl phenyl sulfoxide, vinyl chlorophenyl
sulfoxide, methyl vinyl sulfonate, vinyl sulfoanilide, and the like.
The catalysts, buffers, and any other constituents which can be
employed in the emulsion polymerization reaction mixture in the process of this
invention are the same as those which can be employed in the known emulsion
polymerization processes of the prior art. The particular choice of the
materialsJ other than the emulsifierJ to be employed does not constitute the
il~234~
invention and is a matter of routinism in the art of emulsion
po]ymerization.
The catalyst employed is typically a free radical initiator
or a redox catalyst. One can mention, as merely illustrative of
suitable catalysts which can be employed, free radical initiators
such as hydrogen peroxide, peracetic acid, t-butyl hydroperoxide,
di-t-butyl peroxide, dibenzoyl peroxide, benzoyl hydroperoxide,
2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-bis(hydroperoxy)
hexane, perbenzoic acid, t-butyl peroxypivalate, t-butyl peracetate,
azo-bis-isobutylonitrile, ammonium persulfate, sodium persulfate,
potassium persulfate, sodium perphosphate,potassium perphosphate
isopropyl peroxycarbonate, etc; and redox catalyst systems such
as sodium persulate-sodium formaldehyde sulfoxylate, cumene hydro-
peroxide-sodium mètabisulfite, hydrogen peroxide-ascorbic acid,
sulfur dioxide-ammonium persulphate, etc.
The catalysts are employed in the usual catalytically
effective concentration which are known to those skilled in the art
of emulsion polymerization.
The novel polyurethane polymer amine salt emulsifier is
the subject of Canadian Application Serial No. 350,885 filed on
April 29, 1980.
The polyurethane polymer amine salt consists essentially
of the reaction product of an NCO-terminated prepolymer blocked
with an oxime reacted with an amine and then further reacted with
an acid whereby infinitely water dilutable waterborne polyurethane
polymer amine salts are obtained.
As used throughout this application the term "waterborne"
will indicate the state or condition of the amine salts of the
~1~234~
amine reaction product with the oxime blocked isocyanate prepolymers
in an aqueous medium. It is not always apparent whether the
polyurethane polymers in water is a microscopically
- 9a -
,~
34~
heterogenous mixture of two or more finely divided phases, i.e., liquid in
liquid, and thus a dispersion or whether the polyurethane polymers are partially
or wholly dissolved in the aqueous base and thus a solution.
We have observed the polyurethane polymers in water where the resulting
product appears to be optically clear indicating a homogenous solution. In this
situations we believe that the individual molecules of polyurethane polymers
are not bound together. On the other hand we have also observed polyurethane
polymers in water where the resulting product is cloudy indicating a dispersion.
Thus when used in this application the term "waterborne" will mean the novel
amine salts in an aqueous system and may be either a homogenous solution, a
dispersion or any combination thereof.
In order to provide a satisfactory end product having adequate film
forming characteristics it has been recognized that branched reactants must be
included in the preparation of the waterborne polyurethane in order to get the
necessary cross-linking to produce a three dimensional polymeric structure upon
curing. Therefore it is understood throughout the following description that
either the polyol, the polyfunctional amine, the prepolymer, a portion of each
or any combination thereof shall have a reactive functionality greater than two.
The novel polyurethane polymer amine salt is made in four basic steps.
First, a polyol is reacted with a polyisocyanate to prepare an NCO-terminated
prepolymer. The prepolymer is blocked with an oxime in the second step. Third,
the oxide blocked NCO-terminated prepolymer is reacted with one or more selected
polyfunctional amines as hereinafter described. The amine reaction product is
reacted with an acid. We found that in order to obtain a product with useful
properties that a reactant having functionality greater than 2 should be used
in the first and/or third steps. Thus functionality of the NCO-prepolymer plus
functionality of the polyfunctional amine will be at least four or greater.
- 10 -
It has been found that the reaction product of the polyfunctional
amines with the oxime blocked NC0-terminated prepolymer tends to increase in
viscosity with time until a complete gelation/setting up of the product occurs.
Thus in another aspect of this invention it has unexpectantly been discovered
that the gelation time and viscosity of the waterborne polyurethane polymer
dispersion can be controlled and/or adjusted by the addition of a secondary
amine to the reaction product.
The isocyanate capped polyoxyalkylene polyol, NC0-terminated prepolymer
or urethane prepolymer useful in the invention are prepared by reacting polyoxy-alkylene polyol with an excess of polyisocyanate, e.g., toluene diisocyanate.
The polyol should have a molecular weight of from about 200 to about 200,000
and preferably from about 600 to about 6,000. The hydroxyl functionality
following reaction is from 2 to about 8. When the isocyanate functionality of
the polyol and the corresponding isocyanate functionality of the prepolymer is
two the functionality of the step 3 amine reactant must be greater than two.
When the isocyanate functionality of the prepolymer is greater than two the
functionality of the amine reactant in step 3 may be as little as two.
The preferred isocyanate capped or NC0-terminated prepolymer consists
of a mixture of
(1) an isocyanate capped hydrophilic polyoxyethylene diol, said diol
having an ethylene oxide content of at least 40 mole percent; and
(2) an isocyanate capped polyol having a hydroxy functionality in the
range 3 to 8 prior to capping; said isocyanate capped polyol being present in
an amount in the range 2.9 to 50~ by weight of (1) and (2).
The polyoxyethylene diol is the reaction product of alkylene oxides
of which at least ~0 mole percent is ethylene oxide with an initiator such as
ethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol
1~23~1~
or mixtures thereof. Preferably the molecular weight of the diol is between
abo~t 400 to about 6,000.
Examples of suitable polyols (to be capped with polyisocyanates)
include: (A) essentially linear polyols formed for example by reaction of
ethylene oxide with ethylene glycol as an initiator. Mixtures of ethylene
oxide with other alkylene oxide can be employed so long as the mole percent of
ethylene oxide is at least 40 percent. Where the linear polyethers are mixtures
of ethylene oxide with e.g., propylene oxide, the polymer can be either random
or a block copolymer. A second class of polyol (B) includes those with a
hydroxy functionality of 3 or more. Such polyols are commonly formed by react-
ing alkylene oxides with a polyfunctional initiator such as trimethylolpropane,
pentaerythritol, etc. In forming the polyol B, the alkylene oxide used can be
ethylene oxide or mixtures of ethylene oxide with other alkylene oxides as
described above. Useful polyols can be further exemplified by (C) linear
branched polyfunctional polyols as exemplified in A and B above together with
an initiator or crosslinker. A specific example of C is a mixture of polyethyl-
ene glycol (m.w. about 1,000) with trimethylolpropane, trimethylolethane or
glycerine. This mixture can be subsequently reacted with excess polyisocyanate
to provide a prepolymer useful in the invention. Alternatively the linear or
branched polyols, (e.g., polyethylene glycol) can be reacted separately with
excess polyisocyanate. The initiator, e.g., trimethylolpropane, can also be
separately reacted with polyisocyanate. Subsequently the two capped materials
can be combined to form the prepolymer.
Polyoxyalkylene polyol is terminated or capped by reaction with a
polyisocyanate. The reaction may be carried out in an inert moisture-free
atmosphere such as under a nitrogen blanket, at atmospheric pressure at a
temperature in the range of from about 0C to about 120C for a period of time
11~23~0
of about 20 hours depending upon the temperature and degree of agitation. This
reaction may be effected also under atmospheric conditions provided the product
is not exposed to excess moisture.
Capping of the polyoxyalkylene polyol may be effected using stoichio-
metric amounts of reactants. Desirably, however, an excess of isocyanate is
used to insure complete capping of the polyol. Thus, the ratio of isocyanate
groups to the hydroxyl groups used is between about 2 to about ~ isocyanate to
hydroxyl, and preferably about 2 to about 2.5 isocyanate to hydroxyl molar
ratio.
To obtain the maximum strength, solvent resistance, heat resistance
and the like, the isocyanate capped polyoxyalkylene polyol reaction products
are formulated in such a manner as to give crosslinked polymer network.
Any ketoxime is ef~ective among these being acetone oxime, butanone
oxime, cyclohexanone oxime, and the like. An oxime based on a relatively
volatile ketone is believed to be preferred. The most preferred oxime is
butanone oxime, also commonly known as methyl ethyl ketoxime. Mixtures of oximes
may be used, but there is no known merit in so doing. The proportions of oxime
utilized may range from about 0.7 to about 1.2 equivalents of the isocyanate
groups present. A more preferred range is 1.05 to 1.15 equivalents.
To prepare the blocked prepolymer, the oxime and prepolymer are simply
admixed at temperatures of from 50 to 70C for from about 1/2 to 1-1/2 hours.
A solvent is not generally necessary although materials such as butyl cellosolve
acetate can be employed. Other appropriate solvents include materials which are
not reactive with either the oxime or urethane groups. Based on the moles of
reactive oxime and NCO groups involved, the NOH/NCO molar ratio should be from
about 0.7 to about 1.2 and preferably from about 1.05 to about 1.15. Generally
it is most effective to use sufficient oxime to completely react with the NCO
- 13 -
11~23~3~
groups .
In preparing the blocked prepolymer the oxime selected to provide a
product that will undergo curing reactions in a reasonable time at a reasonable
temperature. The curing temperature is influenced by materials such as sub-
strates and catalysts so that in curing the waterborne polyurethane dispersion
temperatures outside the range of 140-180C can be employed. Curing temperatures
of at least 120C have proved convenient in view of the curing times which must
be employed. Lower temperatures result in longer cure times unless a catalyst
is employed. Numerous oximes and catalysts which can be employed are described
in: Petersen, Liebigs Ann. Chem., 562 tl949), p. 215; Wicks, Progress in
Organic Coatings, 3 (1975), pp. 73-99; and Hill et al, Journal of Paint Tech.,
43 (1971) p. 55. Oximes having the above unblocking temperatures are liquid
materials at temperatures of about 80C, and the condensation products with
urethane prepolymers are miscible with water or can be dispersed in water with
the aid of surfactants. Generally the oximes are aliphatic cyclic, straight-
chain or branched materials containing 2-8 (preferably 3-6) carbons.
The oxime blocked NCO-terminated prepolymer is reacted with an amine
that is capable of causing the polymer to cure at a low temperature. Many of
the amines usable within the scope of Applicants' invention are well known in
the art and are referred to as polyfunctional amines. Specific examples of
amines include, but are not limited to, ethylenediamine 1,3 propane-diamine,
diethylenetriamine, triethylenetetramine, iminobispropylamine, tetraethylene-
pentamine, methyliminobispropylamine, 2t2-aminoethylamine)-ethanol and the
polyoxypropyleneamines manufactured by Jefferson Chemical Company, Inc. and
~ n~R ~
sold under the trade m moc JEFFAMINE D-400, D-2000 and T-403. The polyoxy-
propyleneamines are aliphatic polyether primary di- and tri-functional amines
derived from propylene oxide adducts of diols and triols.
- 14 -
34C~
As can be observed from the amines listed some of the amines can be
represented by general formulae NH2R'-NH'2 and HO-R NH2 where R' is a C2C6
group .
We have found in our experimental work that polyfunctional amines with
a functionality of at least 2 primary amine end groups are the preferred amines
in getting adequate curing of the polyurethane polymer subsequently produced.
Some of the polyfunctional amines may be represented by the formula
H2N- (CnH2n- 1 ) Z~CnH2n NH2
where z is an integer from 1 to 4, n is an integer larger than 1 and R is hydro
gen, an alkyl group of 1 to 4 carbon atoms, or a hydroxyalkyl group of 1 to 4
carbon atoms.
The polyoxypropyleneamines may be represented by the formula
N}12CH~CH3)CH2~ CH2CH(CH3 ~x NH2
where x is greater than 2, and by the formula
CH2 { CH2-cH-(cH ~ NH2
CH3CH2 C -CH2{CH2-CH- (CH~NH2
~H2 { CH -CH-(CH ~ NH2
where x+y+z is about 5.3. The molecular weights of these polyoxypropylene amines
range from 200 to 2000 or larger with the preferred polyoxypropyleneamines having
molecular weights of about 400 to 2000.
The amount of polyfunctional amine added to the oxime blocked NC0-
terminated prepolymer should be in the range of 0.6 to 1.5 equivalents with thepreferable range between 0.9 to 1.1 equivalents based on the total equivalents
of all the isocyanate groups present in the NC0-terminated prepolymer.
Where the isocyanate functionality of the NC0-terminated prepolymer is
two, a polyfunctional amine having a functionality of greater than two is
required in order to provide a satisfactory cross-linked product. When the
isocyanate functionality of the NC0-terminated prepolymer is greater than two,
the polyfunctional amine functionality may be as little as two. It is to be
understood from this that in the same reactive sys~em that the functionality
of the NC0-terminated prepolymer and the amine or polyoxypropyleneamines will
have a total functionality of greater than four.
The reaction between the oxime blocked prepolymer and the polyfunc-
tionalamine is controlled by adding an acid or a mixture of acid and water
prior to the completion of the reaction. Failure to control the amine-oxime
blocked prepolymer reaction at the proper time may result in an amine reaction
product too viscous for the purposes of this invention. Thus the proper portions
of the blocked prepolymer and polyfunctional amine are placed in a reaction
vessel and reacted under controlled conditions of heating and stirring. With
experience we have been able to determine the state of the reaction by observing
the increase in viscosity. With proper equipment such as temperature controlled
mixing head devices the reaction times can be rapid at elevated temperatures.
For example reaction times can be as short as about 3 minutes at about 95C,
4 minutes at about 80C, etc. Preferred reaction times are from about one-half
hour to about one hour with temperatures between about 40 and 60C. Sufficient
acid or water-acid mixture is stirred into the amine reaction product to lower
the pH value to about 5 or below.
The cationically stabilized waterborne polyurethane polymers are
prepared by dispersing the amine reaction product in water in the presence of
sufficient acid to provide a pH of from about 5 or below. In preparing the
waterborne polymers the acid can be added directly to the amine reaction product
and admixed therewith followed by dilution with water. This is the preferred
- 16 -
3~0
method. However, it is also possible to first add the acid to the water
followed by dispersion of the amine reaction product in the water. Other addi-
tives such as surfactants, ultraviolet absorbers, stabilizers, pigments, etc.,
may be formulated into the waterborne polyurethane polymers as required.
It has been found that if the pH is not controlled within the broad
range set forth above, settling problems are encountered and/or portions of the
amine reaction product reacts with the water to form a crust. While the pH
value range is to be considered we have found that from about 1 to 10 parts or
more of acid may be used for each 100 parts of amine reaction product. A more
preferred range is from about 4 to 8 parts acic per 100 parts amine reaction
product. ~hese waterborne polymers have been found to be stable for periods of
several months at ambient temperatures, e.g., 20C, and also exhibit excellent
resistance to freeze-thaw cycles.
While any organic or inorganic acid will form the amine salt and per-
form the function of controlling the pH value, the acids which we have used in-
clude glacial acetic acid, acrylic acid, citric acid, ethylenediaminetetraacetic
(fiDTA) acid, formic acid~glycine (aminoacetic acid), hydrochloric acid, lactic
acid (alpha-hydroxypropionic acid), orthophosphoric acid ~H3P04), phosphorous
acid (H3P03), sulfamic acid, sulfuric acid, tartaric acid (dihydroxysuccinic
acid), paratoluenesulfonic acid and mixtures thereof.
The following specific examples are illustrative but not limitative
of our invention, it being understood that similar improved results are obtain-
able with other combinations of different composition specified above. All
such variations which do not depart from the basic concept of the invention and
composition disclosed above are intended to come within the scope of the
amended claims.
Preparation of Polyurethane Prepolymer
Amine Salt
-
A preferred isocyanate terminated polyol prepolymer is prepared by
mixing a hydrophilic polyoxyethylene diol having an ethylene oxide content of
at least 40 mole percent with a polyol having a hydroxyl functionality in the
range 3 to 8, said polyol being present in the admixture in an amount in the
range 1.0 to 20% by weight, reacting with the mixture at a temperature in the
range 0 to 120C an amount of a diisocyanate equal to 1.8 - 1.9 NCO to OH
equivalents for a time sufficient ~o cap substantially all the hydroxyl groups
of the admixture, adding additional diisocyanate to provide 0.1 - 0.3 equivalents
of NCO per initial equivalent of OH in excess of the theoretical amount
necessary to react with the hydroxyl groups.
To 100 grams of the NCO terminated polyol prepolymer at 24C in a
stainless steel vessel is added 22 grams of butanone oxime with stirring. The
reaction of the oxime with the isocyanate is exothermic and the temperature
went to 60C. A hot water bath is used to control the temperature between 80-
90C for twenty minutes.
After twenty minutes and the temperature at 90C, 12 grams of diethyl-
enetriamine is added with stirring. The reaction with the amine is also
exothermic which accelerates chain extension.
The viscogity continues to increase and after ten minutes at 90-95C,
7.1 grams of glacial acetic acid and 7.1 grams of o-phosphoric acid dissolved
in 100 grams of deionized water is slowly added to control the viscosity. After
all the acid/water mixture is in, the material is cooled and packaged. Water
may be added to achieve the desired % non volatiles (%N.V) and viscosity.
Typical physical properties of the emulsifier prepared are:
- 18 -
1~23`4~?
% N.V 52.0
pH 4.5-6.9
Viscosity (Brookfield LVF) 600-1000 cps
Appearance clear, straw colored solution
EXAMPLE 1
To a two liter resin kettle fitted with a condenser, thermometer,
graduated addition funnel, stirrer, and a nitrogen source was added 327.5 g.
of demeneralized water, 2.0 g of isoascorbic acid, and 687.5 g (196.6 grams
nonvolatiles) of cationic polyurethane prepolymer amine salt @ 24% nonvolatiles.
The mixture was stirred and heated to 40C, under a nitrogen blanket.
At 40C, 100 g of a monomer mixture of 240.0 g of methylmethacrylate,
120.0 g of butylacrylate, 40.0 g of acrylonitrile and 8.0 g of acrylic acid
was added to the kettle with stirring. To the material in the resin kettle was
charged 4 cc of 30% hydrogen peroxide. The heat of reaction caused the tempera-
ture to go from 41C to 47C in three minutes. The remaining monomer mixture
was charged at a rate to maintain a temperature of 55-60C in the resin kettle
without auxiliary heating. Discrete shots of 30% H202 were added at 2 cc
levels during the monomer mixture addition. The total monomer mixture addition
time was 39 minutes. When the last of the monomer mixture was charged, the
temperature was 57C.
Eight minutes after the final monomer mixture addition and at a
temperature of 54C, 0.1 g of isoascorbic acid dissolved in 10 cc demineralized
water and 1.0 g of tertiary butylhydroperoxide were added to reduce the free
monomer.
The two liter resin kettle (after packaging latex) had no solid build-
up at all and required only a water rinse. The resulting latex had 39.6% Total
Solids, a pH value of 4.3, a surface tension of 43.2 dynes/cm and a Brookfield
- lg -
46~
LVF #1 @ 60 viscosity of 53.4 centipoises.
EXAMPLE 2
REACTANT % WET
vinylidene chloride 67 640
butyl acrylate 15.0 144
glacial acetic acid 2 16
polyurethane prepolymer amine 17 400
salt @ 40% solids
ascorbic acid .2 2
hydrogen peroxide 1.0 10
demineralized water - 800
To a 2 liter resin kettle fitted with a thermometer, stirrer and addition funnel
was added 800 g. water, 400 g. polyurethane prepolymer amine salt at 40% solids,
and 2 g. ascorbic acid. This mixture was heated to 36C under a nitrogen
purge.
To the above was added 200 cc of a mixture consisting of 640 g.
vinylidene chloride, 144 g. butyl acrylate, and 16 g. glacial acetic acid
followed by the addition of 2 cc of 20% hydrogen peroxide. The heat or reaction
raised the temperature to 46C. The remainder of the monomer was added in 100
cc increments along with 1-2 cc shots of hydrogen peroxide to maintain a tem-
perature range of 45-50C. After the last of the monomer was added, a 2 cc
parting shot of hydrogen peroxide was added and the batch was allowed to cook
to reach maximum conversion. The latex had the following properties:
Total Solids 39.0%
Conversion 81.6%
Surface Tension 52.8 dynes/cm
pH Value 4.0
Examples 3 through 12 below illustrate emulsion polymerization using the poly-
urethane prepolymer amine salt as emulsifier with various monomer combinations.
The procedure used in Examples 3-12 was that described in Example 2. All
ingredients are indicated in weight percent.
- 20 -
234~)
Example 3-
Weight %
vinylidene chloride 32
styrene 33
acrylic acid 2
PAS 33
Example 4:
Weight %
vinylidene chloride 56
methylacrylate 5
acrylic acid 2
PAS 37
Example 5:
Weight %
methylmethacrylate 6
butylacrylate 13
methylacrylate 37
acrylic acid 6
PAS 38
Examples 6, 7, 8:
Weight %
6 7
methylmethacrylate 49 42 39
butyl acrylate 25 21 20
acrylonitrile 8 7 6
acrylic acid 2 2 2
PAS 16 28 33
Examples 9,_10:
Weight %
8 9
vinylidene chloride 33 28
styrene 33 28
butyl acrylate 16 14
acrylic acid 2 2
PAS 16 11
- 21 -
~1~2~5
Example 11:
Weight %
methylmethacrylate 71
PAS 29
Example 12:
Weight %
12_1 12-2
methylmethacrylate 42 37
butylacrylate 21 18
acrylonitrile 7 6
acrylic acid 2 2
PAS 28 37
The te~ns and expressions which have beem employed are used as terms
of description and not of limitation, and there is no intention, in the use of
such terms and expressions, of excluding any equivalents of the features shown
and described or portions thereof, but it is recognized that various modifications
are possible within the scope of the invention claimed.
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