Note: Descriptions are shown in the official language in which they were submitted.
~L2~387
--1--
SELF-CURABLE LATEX COMPOSITIONS
This invention relate~ to self-curing polymer
latexes.
Diverse self-~uring polymer latexes are k~own
in the art~ For example, blends of a carboxylated
latex such as an a~~rylic acid/styrene/butadiene terpoly-
mer latex with a melamine formaldehyde or urea formal-
dehyde resin are known to be self-cu A ng, i.e., they
~orm a curable composition which cures at elevated
temperatures.
Other self-curable latex systems employ a
car~oxylated latex which is cxosslinked with a polyvalent
cation or with a cationic polymer. Such latexes have
~he disadvantages of being pH dependent and of forming
films which are highly sensitive to water, solvents or
other chemicals.
Consequently, a self-curable latex which is
free of the disadvantages of previously known self-
-curable latexes would be highly desirable.
31,759-F -1-
*
__
~Z4~3~7
--2--
This invention is such a self-curable latex~
The latex of ~his invention is a curable latex composi-
tion comprising an aqueous dispersion of (a) discrete
particles of an oxazoline modified addition polymer
containing pendant oxazoline groups which polymer has
been prepared in an emulsion polymerization process
from (1) an oxazoline as represented by the formula:
R2 fR2
Q N
Rl
wherein Xl is an acyclic organic radical h~ving addition
polymerizable unsaturation; each R2 is independently
hydrogen, halogen or an inertly sub~tituted organic
radical and n is 1 or 2 and (2) at least one other
addition polymerizable monomer which is copolymerizable
with said oxa~oline and is not a coreactive monomer or
an oxazoline and (b) discrete particles of a coreactive
polymer containing pendant coreactive groups which
coreactive polymer has been prepared in an emulsion
polymerization process from tl) an addition polymerizable
coreactive monomer containing pendant groups which are
capable sf reacting with an oxazoline group to form a
covalent bond thereto and (2) at least one other monomer
which is copolymerizable with said coreactive monomer.
Surprisingly, the latexes of this invention,
when dried to form films, coatings, or other articles,
exhibit excellent tensile and elongation properties and
are surprisingly resistant to aqueous and organic
31,759-F -2-
~2~931~7
-3-
fluids. ~lso surprising is that many of the latexes of
this invention are self-curable at room temperature,
i.e., crosslinking of the latex occurs without heating
the latex and without the addition of curing agents.
The composition of this in~ention contains
discrete particles of an oxazoline modified polymer.
Said oxazoline modified polymer has been prepared by
- the emulsion polymeriæation of certain addition polym-
erizable oxazolines and at least one other copolymeriz-
able monomer.
The oxazolines employed herein are as repre-
sented by the general structure:
R2 ~R2
l ~2)
R2-l- ~ ~n
~ lC~
Rl
wherein R1 is an acyclic organic radical having addi-
tion polymeri~able unsaturation; each R2 is indepen-
dently hydrogen, halogen or an inertly substituted
organic radical and n is 1 or 2. Preferably, R1 is
~2C=C-
wherein R3 is hydrogen or an alkyl radical. Most
preferably, R1 is an isopropenyl group. Each R2 is
preferably hydrogen or an alkyl group with hydrogen
31, 759-F -3-
~Z49387
-4-
being most preferred; and n is preferably 1. Most
preferably the oxazoline is 2-isopropenyl-2-o~azoline.
The oxazoline modified polymer also contains
repeating units derived from at least one monomer which
is not an oxazoline and which is copolymerizable with
the aforementioned oxazoline. A broad range of addition
polymerizable monomers are copolymerizable with said
oxazoline and are suitable herein. Suitable monomers
include, for example, the monovinyl aromatics, alkenes,
esters of Q, ~-ethylenically unsaturated carboxylic
acid; car~o~ylic acid esters wherein the ester group
contain~ addition polymerizable unsaturation; halo-
genated alkenes; acyclic aliphatic conjugated dienes
and the ll~ke. Small amounts of crosslinking monomers
15 such as divinylbenzene may also be employed.
The term "monovinyl aromatic monomer" is
intended to include those monomers wherein a radical of
the formula:
CY2=C-
(w~erein R is hydrogen or a lower alkyl such as an alkyl
having from 1 to 4 carbon atoms~ is attached directly
to an aromatic nucleus containing from 6 to 10 carbon
atoms, including those monomers wherein the aromatic
nucleus is substituted with alkyl or halogen substitu-
ents. Typical of these monomers are styrene; ~-methyl-
styrene; ortho-, meta- and para-methylstyrene; ortho-,
meta-and para-ethylstyrene; o,p-dimethylstyrene;
31,759-F -4-
~2~93~7
-5-
o,p-diethylstyrene; isopropylstyrene; o-methyl p-iso-
propylstyrene; t-butyl styrene; p-chlorostyrene;
p-bromostyrene; o,p-dichlorostyrene; o,p-dibromostyrene;
vinylnaphthal~ne; diverse vinyl (alkylnaphthalenes) and
vinyl ~halonaphthalenes) and comonomeric mixtures
thereof. Because of considerations such as cost,
availability and ease of use, styrene and vinyltoluene
are preferred and styrene is especially preferred as
the monovinyl aromatic monomer.
Alkenes suitably employed herein include the
monounsaturated aliphatic organic compounds such as
ethylene, n- and isopropylene, the diverse butenes,
pentenes, and hexenes as well as alkenes containing
diverse substituent groups which are inert to the
polymerization thereof. Preferred are unsubstituted
C2 C8 alkenes with C2-C4 unsaturated alkenes being most
pre~erred.
Esters of a,~-ethylenically unsaturated
carbcxylic acids useful herein include typical~y soft
acrylates, those whose homopolymers have a glass
transition temperature (Tg) of less than about 25C.
~xamples of these include ben~yl acrylate, butyl
acrylate, sec-butyl acrylate, cyclohexyl acrylate,
dodecyl acrylate, ethyl acrylate, 2-ethylbutyl
acrylate, 2-ethylhexyl acrylate, heptyl acrylate, hexyl
acrylate, isobutyl acrylate, isopropyl acrylate, methyl
acrylate and propyl acrylate. Hard acrylates, those
whose homopolymers have a Tg of greater than about 25C,
can also be used. Examples of these include 4-biphenylyl
acrylate and tert-butyl acrylate. Soft methacrylates
are also suitable for use. Examples of such include
butyl methacrylate and hexyl methacrylate. Also useful
31,759-F -5-
~4g387
-6-
in the present invention are hard methacrylates such as
sec-butyl methacrylate, tert-butyl methacrylate, cyclo-
he~yl methacrylate, ethyl methacrylate, isobutyl
methacrylate, isopropyl methacrylate, methyl methacrylate
and propyl methacrylate. The cost, availability and
known properties of butyl acrylate and ethyl acrylate
make these monomers preferred among the acrylates. The
cost, availability and known properties of methyl
methacrylate make it preferred among the methacrylates.
Halogenated alkenes useful herein include,
for example, vinyl chloride, vinylidene chloride, vinyl
fluoride, vinylidene fluoride, and the diverse polychloro-,
polyfluoro- and polybromo alkenes.
Acyclic aliphatic conjugated dienes usefully
employed herein include typically those compounds which
have from 4 to 9 carbon atoms, for example, 1,3-butadiene;
2-methyl-1,3-butadiene; 2,3-dimethyl-1,3-butadiene;
pentadiene; 2-neopentyl-1,3-butadiene and other hydro-
carbon analogs of 2,3-butadienes, such as 2-chloro-
-1,3-butadiene and 2-cyano-1,3-butadiene; the substituted
straight chain conjugated pentadienes; the straight
chain and branched chain conjugated hexadienes; other
straight and branched chain conjugated dienes having
from 4 to 9 carbon atoms; and comonomeric mixtures
thereof. The 1,3-butadiene hydrocarbon monomers such
a~ those mentioned hereinbefore provide interpolymers
having particularly desirable properties and are therefore
preferred. The cost, ready availability and the excellent
properties of interpolymers produced therefrom makes
1,3-butadiene the most preferred acyclic aliphatic
-conjugated diene.
-
31,759-F -6-
~249387
-7-
Mixtures of two or more of the foregoing
monomers may, of course, be employed herein, if desired.
Of the foregoing monomers, most preferred are styrene,
mixtures of styrene and butadiene, butyl acrylate,
methyl methacrylate and vinyl acetate.
The proportion of monomers used in the oxazo-
line modified latex may vary considerably depending on
the particular end use of the composition. Typically,
however, the oxazoline is employed in ~elatively minor
amounts, e.g. from 0.1 to 20, preferably from 1 to 10,
weight percent of the monomers. In general, the
oxazoline monomer is employed primarily to impart the
desired self-curing characteristics to latex composition
and the other monomers are employed to impart the other
desired properties to the composition. For example, in
a preferred oxazoline modified styrene/butadiene latex,
the oxazoline modified polymer will advantageously
exhibit physical properties ~e.g., gla~s transition
temperature and hardness) similar to those commonly
associated with styrene/butadiene polymers. However,
certain properties of the polymer, especially adhesion
and crosslinking, will generally be enhanced by the
inclusion of the oxazoline monomer.
The latexes are conveniently prepared by
conventional emulsion polymerization techniques in an
agueous medium with conventional additives. Thus, for
example, the mono~er charge desired to be employed for
-- the oxazoline modified latex is dispersed in an aqueous
- -- medium with agitation with from 0.5 to 5 weight percent
- 30 (based on the monomer charge) of conventional anionic _ _
-~ and/or nonionic emulsifiers ~e.g., potassium n-dodecyl
sulfonate, sodium isooctobenzene sulfonate, sodium
31,759 F -7-
~Z~931~7
-8-
laurate and nonylphenol ethers of polyethyl~ne glycols)
and thereafter polymerizing the resulting aqueous
dispersion.
Conventional emulsion polymerization catalysts
can be employed in the foregoing latex polymerization
and common examples thereof include peroxides, persul-
fates, azo compounds such as sodium persulfate, potassium
persulfate, ammonium persulfate, hydrogen peroxide and
azodiisobutyric diamide. Also suitable are catalysts
(e.g., redox catalysts) which are activated in the
water phase (e.g., by a water-soluble reducing agent).
The type and amount of catalyst, as well as the particular
polymerization conditions employed, will typically
depend primarily on the other monomers which are used,
and polymerization conditions will be generally selected
to optimize the polymerization of such other monomers.
Typically, the catalyst is employed in a catalytic
amount, e.g., ranging from 0.01 to 5 weight percent
based upon the monomer weight. In general, the
~0 polymerization is conducted at a temperature in the
range of from -10 to 110C (preferably from 50 to
90C). Since the oxazoline group of the oxazoline
monomer will hydrolyze or react with other monomers at
high or low pH, the polymerization is conducted at such
pH such that said hydrolysis or reaction is minimized.
Typically, a pH of 3-11, preferably 6-11 is suitable.
More preferably, a pH of 7 to 10 is suitable. The
polymerization may be conducted continuously, semi-
continuously, or batch-wise.
Similarly, conventional chain transfer agents
such as, for example, n-dodecyl mercaptan, bromoform
and carbon tetrachloride can also be employed in the
31,759 F -~-
~L24931~7
normal fashion in the aforementioned polymerization to
regulate the molecular weight of the polymer formed
therein. Typically, when such chain transfer agents
are used, they are employed in amounts ranging from
0.01 to 10 (preferably from 0.1 to 5) weight percent
based upon the weight of the monomers employed in the
polymerization. Again, the amount of chain transfer
agent employed depends somewhat on the particular chain
transfer agent employed and the particular monomers
being polymerized.
Suitable latex polymerization procedures are
taught, for instance, in U.S. Patent Nos. 4,325,856;
4,001,163; 3,513,121; 3,575,913; 3,634,2g8; 2,399,684;
2,790,735; 2,880,189; and 2,949,386.
The latex of this i~vention further comprises
discrete particles of a coreactive polymer. Said
coreactive polymer particles are prepared in an emulsion
polymerization process from an addition polymerizable
monomer containing pendant groups which are capable of
reacting with an oxazoline group to form a covalent
bond thereto (hereinafter "coreactive monomer") and at
least one other monomer which is copolymerizable with
said coreactive monomer.
The coreactive monomers employed herein are
those which contain pendant coreactive groups which are
capable of reacting with an oxazoline group to form a
covalent bond thereto. It is understood that the
reaction of such coreactive groups with the oxazoline
group will typically, but not necessarily, cause the
oxazoline ring to open.
31,759-~ _9_
~LZ4~387
, --10--
Typically, the pendant coreactive group on
the coreactive monomer wilI contain a reactive hydrogen
atom. Exemplary coreactive groups containing an active
hydrogen atom include strong and weak acid groups;
aliphatic alcohols; aromatic alcohols, i.e., phenols;
amines; and amides, i.e., -CONH2 and -CONH- groups. In
general, the more reactive of such groups, i.e., those
having the more labile hydrogen, such as the acids and
aromatic alcohols, are preferred herein. Such more
reactive groups will generally react with the oxazoline
ring more readily under milder conditions than the less
reactive groups such as the amines and aliphatic alcohols.
Amide groups are generally intermediate in reactivity.
Especially preferred are monomers containing
pendant strong or weak acid groups or acid anhydride
groups. Such monomers include those ethylenically
unsaturated monomers containing acid groups, such as
carboxylic acid and sulfonic acid groups, or acid
anhydride groups. Sulfoethyl acrylate is an example of
a suitable monomer containing a sulfonic acid group.
Exemplary of suitable monomers containing carboxylic
acid groups include itaconic acid, acrylic acid,
methacrylic acid, fumaric acid, maleic acid, vinylbenzoic
acid and isopropenylbenzoic acid. The more preferred
species include acrylic, methacrylic, fumaric, itaconic
and maleic acids. Maleic anhydride is an exampl~ of a
suitable monomer containing an acid anhydride group.
Suitable coreactive monomers containing
phenolic groups include ortho- and meta-vinyl phenol.
31,759-F -10-
~249387
Suitable coreactive monomers containing
aliphatic hydroxyl groups include, for example,
hydroxyethylacrylate, hydroxypropyl methacrylate and
N-hydroxymethyl-N-methyl acrylamide. Derivatives of
styrene having aliphatic hydroxyl groups are also
useful herein.
Suitable coreactive monomers containing amide
groups include acrylamide, methacrylamide, vinyl acetamide
and ~-chloroacrylamide. N-methylacrylamides and N~methyl-
m~thacrylamide are examples of monomers containing~CONH~ g~oups.
Suitable coreactive monomers containing amin~
groups include allyl amine, 2-aminoethylacrylate and
2-aminoethylmethacrylate.
The other monomers suitably employed in the
coreactive polymer particles are those which are copolym-
erizable with the coreactive monomer. In general,
those monomers described hereinbefore as being useful
in the preparation of the oxazoline modified polymer
are also useful in the preparation of the coreactive
polymer. In fact, it is often desirable to "match" the
polymer backbone of the coreactive polymer to that of
the oxazoline modified polymer; that is, except for the
oxazoline and coreactive monomers, to employ the same
monomers in the same proportions in both the coreactive
and oxazoline modified polymers. It is understood,
however, that different monomers may be employed in the
preparation of the oxazoline and coreactive polymers in
order to obtain the particular characteristics desired.
31,759-F -11-
~2~93g~'
-12-
As with the oxazoline modified polymer, the
coreactive polymer generally contains only a minor
portion of repeating units which are derived from the
coreactive monomer. In general, the coreactive monomer
is employed in amounts sufficient to impart the desired
auto-curable properties to the latex composition and
the other monomers are employed to impart the properties
which are typically associated with polymers made from
such monomers. In general, the coreactive monomer will
lLO comprise from 0.1 to 50, preferably from 0.1 to 20,
most preferably from 1 to 10, weight percent of the
monomers employed in the preparation of the coreactive
pol~mer.
The coreactive pol~mer particles are conven-
iently prepared in an emulsion polymerzation process
similar to that described hereiDbefore for the prepara-
tion of the oxazoline modified polymer. When the
coreactive monomer is one containing pendant weakly
acidic groups such as carboxyl groups, the polymerization
is advantageously conducted under conditions sufficiently
acidic to promote the copolymerization of the weakly
acidic coreactive monomers with the other monomers
being employed. Preferably the pH is maintained
between 1 and 6, more preferably between l and 4.
Then, following the polymerization reaction, the pH of
the agueous phase is typically adjusted with base to
raise the pH to 7.5 to 9, in order to prevent
hydrolysis of the oxazoline rings in the oxazoline-
-modified latex upon subsequent blending.
The curable latex composition of this
invention is advantageously prepared from the oxazoline
modified latex and the coreactive latex by simple
31,759-F-12-
~24931~7
-13-
blending of the respective latexes in the desired
proportion. In general, the relative proportions of
oxazoline modified and acidic latexes are chosen such
that the resulting self-curable latex composition
contains from 0.05 to 20, preferably from 0.2 to 5,
more preferably from 0.5 to 2, equivalents of acid
groups per equivalent of oxazoline group. In addition,
better water and solvent resistance, as well as greater
tensile strength is generally seen when the latex
composition contains comparable amounts of particles of
oxazoline-modified polymer and coreactive polymer.
Preferably, the latex contains 0.1 to 10, more
preferably 0.2 to 5, most preferably 0.40 to 2.5,
particles of oxazoline-modified polymer per coreactive
polymer particle. Such blending is advantageousIy
performed at room temperature with mild agitation. The
resulting product is an aqueous dispersion containing
discrete particles of the oxazoline modified polymer
and discrete particles of the acidic polymer.
Advantageously, the respective particle sizes
of the oxazoline-modified and the coreactive polymers,
and the respective particle size distributions are such
that the particles tend to pack together well to form
dense, coherent films. The particles may all be of
relatively uniform size, or may have different sizes
such that the packing together of said particles upon
film formation is enhanced.
The curable latex composition of this
invention may be used for a variety of applications
including paper coating compositions, adhesives,
binders and fibrous, nonwoven fabric compositions.
Such compositions are especially suitable for
31,759 ~ -13-
~Z49387
-14-
those applications in which a self-curable, curable
polymer composition is desired.
The latexes of this i~vention may be employed
as adhesives, films or binders by applying the latex to
the desired substrate, then dewatering the latex and
curing the dewatered polymers. T~e dewatering step may
be performed by merely allowing the aqueous phase to
evaporate under ambient conditi~ns. Alter~atively,
elevated (i.e., 50-165C) temperatures may be employed
to dewater the latex. Curing of the polymer may,
likewise, be performed at ambient temperatures. Such
ambient temperature curing is an unexpected property of
the latexes of this invention. Such room temperature
curing is generally conducted over a period of several
hours to several days depending on the particular
polymers employed, the amounts of oxazoline and acidic
groups in the polymer, the thickness of the film adhesive
or binder layer, the amount of crosslinking desired and
like factors. Curing may also be effected by heating
the polymers preferably to 105 to 165C, more preferably
135 to 150C for short periods. The foregoing drying
and curing points may not be distinct steps but may be
carried out simultaneously if desired.
The following examples are intended to illus-
trate the invention but not to limit the scope thereof.
All parts and percentages are by weight unless otherwise
indicated.
Exam~le
A. Pre~aratlon of Carboxylated Latex
Into a 0.0038 cubic meter (l-gallon), jacketed
reactor equipped with FMI lab pumps to deliver monomer
31,759-F -14-
-
~249387
-15-
and aqueous feeds were added 590 g of water, 7 g of a 1
percent active aqueous pentasodium diethylene triamine
pentaacetate solution and 24.4 g of a 29 percent solids
seed latex. The seed latex contained polystyrene
particles having a volume average particle size of
about 0.0275 micrometers (~m), i.e., 275 A.
The reactor was purged with nitrogen and
heated to 9OC. Then, over a 3-hour period, was added
a monomer stream containing 455 g of butyl acrylate,
~11 g of styre~e and 2~ g of acrylic ~cid. Added to the
reaction mixture continuously over a four-hour period,
beginning simultaneously with the start of the monomer
stream, was 245 g of deionized water, 15.56 y of a 45
percent active aqueous surfactant solution, 14 g of a
10 percent aqueous sodium hydroxide solution and 4.9 g
of sodium persulfate. Following the addition of the
monomer in aqueous streams, the reaction mixture was
heated at 90C for 1 additional hour and then cooled.
The product was a 44.8 percent solids latex of a butyl
acrylate/styrene/acrylic acid polymer in a 65/31~4
weight ratio.
B. Preparation of Oxazoline Modified Latex
Into a 0.0038 cubic meter (1-gallon), jacketed
reactor were added 146 parts deionized water, 0.01 part
of a 1 percent agueous pentasodium diethylene triamine
pentaacetate solution, 5.0 parts of DresinateTM 214
surfactant (available commercially from Hercules, Inc.)
and 0.5 part of sodium persulfate. The reactor was
agitated and purged with nitrogen. To the stirred
reactor was then added a mixture of 25 parts of styrene,
5 parts of 2-isopropenyl-2-oxazoline (IPO), and 0.5 part
t-dodecyl mercaptan. Then, 70 parts of butadiene were
31,759-F -15-
~2493~37
-16-
added and the mixture polymerized at 60C for 8 hours.
The reactor was then opened, and 0.5 part o~ sodium
dimethyl dithiocarbamate were added. The latex was
then steam distilled to remove any unreacted monomers.
The resulting latex contained 33.5 percent solids and
had polymer particles of a butadiene/styrene/IPO
terpolymer in a 70/25/5 weight ratio. This oxazoline
modified latex was designated as Latex No. 1 in Table I
following.
Oxazoline modified Latex Nos. 2, 3 and 4 and
Comparative Latex Nos. C-1, C-2 and C-3 were prepared
using the general procedure employed in preparing Latex
No. 1 except that the amounts of butadiene/styrene/IPO
and t-dodecyl mercaptan were varied as indicated in
Table I followingO In those latexes containing 50
parts butadiene, no sodium dimethyl dithiocarbamate was
added. These latexes are components which are blended
with the above-described carboxylated latex to prepare
latex compositions according to the present invention
or, in some uses, Comparative latexes which present
invention.
31,759-F -16-
~2~938~
TABLE I
Latex PARTS ~Y WEIGHT
No. Butadiene Styrene IPO TDDMl % Solids
1 70 25 5 0.5 33.5
5 C-l* 70 30 0 0.5 3~.0
2 70 25 5 1.0 41.7
C-2* 70 30 0 1.0 39.3
3 50 45 5 0.5 4~.9
4 50 40 10 0.5 37.2
10C-3* 50 50 0 0.~ 38.4
* Not an example of this invention.
T-dodecyl mercaptan.
Self-curable latex compositions were prepared
by stirring together at room temperature equal weights
~based on solids) of IP0 modified Latex No. 1 and the
carboxylated latex. The IPO modified latex and the
carboxylated latex were compatible at all proportions.
The resulting blend was designated as Latex Composition
No. 1 in Table II following. In like manner, Latex
Composition Nos. 2, 3 and 4 and Comparative Latex
Composition Nos. C-l, C-2 and C-3 in Table II below
were prepared by mixing IP0 modified Latex Nos. 2, 3
and 4 and Comparative Latex Nos. C-l, C-2 and C-3 from
Table I above on an equal weight solids basis with the
carboxylated latex. Sample No. C-4 was the carboxylated
latex alone. Multiple films were prepared from Latex
Composition Nos. 1 through 4 and Comparative Latex
Composition Nos. C-l through C-3 by drawing down a
31,759-F -17-
1;~4938 17
-18-
0.51 millimeter (20 mil~ thick film onto a Teflon brand
coated steel plate and then drying the film at ambient
temperatures until it becomes transparent. The trans-
parent films were then peeled from the plate and further
dried at ambient temperature for about 24 hours. Some
of the resulting films were then cured for 5 minutes at
80C, 120C or 150C. The resulting films were then
cut into stips 13 millimeters (0.5 inch) wide and
tested on an Instron tensile tester for elongation at
break and tensile strength. In addition, duplicate
samples were soaked for 5 minutes in a 0.5 percent
aqueous surfactant solution and the thus wetted ~ilms
were tested on the Instron for elongation at break and
tensile strength. The results were as r~corded in
Table II following. The Elongation values are in
percent and the Tensile values are in megapascals
(MPa).
31,759-F -18-
12~93~37
-61- ~-6SL ' 1~
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--61--
~24~387
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--OZ--
1~493~7
-21-
As can be seen from Table II, the latex
compositions of this invention generally formed films
having higher tensile strength and somewhat lower
elongation than the comparative latex compositions.
The data presented in Table II clearly illustrates the
improved resi tance to water exhibited by the latex
- compositions of this invention. Films prepared from
the ~omparative latex compositions exhibited decreases
in the range from about 30 to 70 percent in ten~ile
strength upon wetting. By contrast, the latex
compositions of thls invention typically lost only
about 10 to 25 percent of their tensile strength.
Thus, the films prepared from the latex composition of
this invention are clearly significantly less water
sensitive than the films prepared from the comparative
latex compositions. In addition, the films prepared
from the latex compositions of this invention exhibit
an excellent combination of good elongation and high
tensile strength both in the dry and wet samples.
In order to measure degree of crosslinking
and resistance to solvents, the swelling index and
percent gel of the above-prepared films which have been
cured at room temperature, 100, 120 and 150C were
determined as follows.
Duplicate film samples were prepared from
Latex Composition Nos. 1 and C-1, using a 0.51 millimeter
(0.020 inch) casting bar. Each film was allowed to dry
until clear and was peeled off as a continuous film.
One film was evaluated without curing; others were
evaluated after 5 minute cures at 100, 120 and 150C,
respectively. The film being tested was weiyhed and
placed into a centrifuge tube. To the tube was added
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30 g of toluene. The tube was sealed and shaken vigorously
for 90 minutes. The tube was then centrifuged at about
18,000-19,200 rpm for 1 hour. The toluene was then
poured off and the remaining wet gel was weighed. The
5 gel was then dried in a vacuum oven until a constant
weight was obtained. Percent gel was calculated as:
weight of dry gel x 100%
weight of film sample
Swelling index is calculated as:
10 w 'ght wet qel-weiqht dry gel
weight dry gel
The results obtained were as reported in
Table III following.
TABLE III
Latex Com~osition Latex Composition
No. 1 No. C~l*
Swellinq Index
R.T. Cure 13.86 23.3
100C Cure 7.58 22.62
20 120C Cure 8.23 27.41
150C Cure 7.02 23.88
% Gel
R. T . Cure81.3 42.03
100C Cure 81.65 49.83
25 120C Cure 80.87 46.38
150C Cure 82099 49.66
* Not an example of the invention.
As can be seen in Table III, films prepared
from the latexes of this invention exhibit greatly
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incxeased resistance to solvents and greater proportions
of insoluble material than did the comparative samples.
Testing of films prepared from Latex Composition Nos. 2,
3 and 4 showed similarly improved sol~ent resistance and
higher amounts of insoluble material as compared to the
relevant controls.
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