Note: Descriptions are shown in the official language in which they were submitted.
WO 91/17201 PCr/US91/02606
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WATER-RESISTANT LATEXES, ADHESIVES AND LAMINATES
The present invention relates to water
resistant latexes and a process for the preparation
thereof. Typical applications for such latexes include
adhesives, binders and coatin~s whether used in
combination with a filler or without a filler.
Latexes are typically prepared with additives
which are thought to contribute to undesirable water
sensitivity in various latex applications. This problem
in various latex systems has prompted the development of
solvent-based systems having less sensitivity to water.
These solvent based systems Fenerally are more costly
than aqueous systems, all other factors being equal.
Nonaqueous solvent based systems have the additional
disadvantage that solvent emissions into the environment
from these systems increasingly is a problem.
U.S. Patent Number 4,972,018 discloses the use
of ammonia-based latexes in a latex based adhesive
composition containing ammonium zirconium carbonate for
the enhancement of hot, green bond adhesive properties
of paperboard and corrugated board. U.S. Patents Number
4,721,748 and 4,668~730 disclose the use aqueous
ammonium hydroxide as a fugitive alkali in the
preparation of colloid stabilized latex adhesives. U.S.
WO91/17201 ~ PCT/US91/02606
~ 3~ -2- ~
Patent Number 4.626,567 relates to a water-resistant
clear and colored acrylic latex sealant~ U.S. Patent
Number 4,425,291 relates to a method ~or the production
of more water-resistant foamed elements from a
waterglass containing natural latex dispersion~ U.S.
Patent Number 4,340,524 discloses water-resistant latex
sealants. U.S. Patent Number 3.966~6~1 discloses a
continuous process for the preparation o~ carboxylated
late~es in a two reactor system which possibly uses
ammonium based ingredients.
It would be desirable to produce a water-based
latex for use in systems where water resistance is
important, where the constituents of the latex do not
compromise the water resistance of the system.
An important embodiment of the present
invention is a process for preparing latexes which
comprises:
(a) emulsion polymerizing one or more monomers
selected from monoethylenicàlly
unsaturated carboxylic acid monomer,
monovinyl aromatic monomer~ aliphatic
conjugated diene monomer, acrylate
monomer, vinylidene halide monomer and
vinyl halide monomer to form a polymeric
latex in the presence of a stabilizing
amount of a surfactant in either an acid
form or an ammonium salt form and
optionally a sodium salt surfactant in an
amount not to exceed 0.3 parts per hundred
parts monomer, and
WO91/17201 PCT/US91/02606
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(b) stabilizing the polymer prior to stripping
with ammonium hydroxide.
Another embodiment of the instant invention is
a process for preparing an adhesive which comprises:
(a) emulsion polymeri2ing one or more
monoethylenically unsaturated oarboxylic
acid monomers with a group of one or more
comonomers
to form a polymeric latex in the presence of:
ti) a stabilizing amount of a surfactant in
an acid form or an ammonium salt form
and optionally a sodium salt surfactant
in an amount not to exceed 0~3 parts per
hundred parts monomer, and
(ii) an initiating amount of ammonium
persulfate and optionally potassium or
sodium persulfate in an amount of up to
1.75 parts per 100 parts monomer; and
(b) stabilizing the polymer prior to stripping
with ammonium hydroxide~ and
(c) adding a wetting agent to the latex to
form an adhesive in an amount of from 0.5
to 6~0 weight percent based on the total
3 weight of the adhesive.
Other aspects of the invention include the
latex and the adhesive produced by the processes of this
invention, and a laminate prepared with the adhesive of
this invention.
WO91/17201 PCT/US91/02606
-4-
e invention additionally includes the use of
specific monoethylenically unsaturated car~oxylic acid
monomers, such as acrylic. fumaric and itaconic acids to
impart stability to the latex when ammonium hydroxide is
used as the neutralizing agent.
Although the instant invention pro~ides a
general process ~or the preparation of latexes suitable
for use in water-resistant applications~ such as water
resistant adhesives, another important aspect o~ the
invention is a process for preparing latexes which
comprises:
(a) emulsion polymerizing one or more
monoethylenically unsaturated carboxylic
acid monomers with a group of one or more
comonomers to form a polymeric latex in
the presence of a stabilizing amount of a
surfactant in either an acid form or an
ammonium salt form and optionally a sodium
salt surfactant in an amount not to exceed
0.3 parts per hundred parts monomer, and
(b) stabilizing the polymer prior to stripping
with ammonium hydroxide~
The comonomer group is one of groups (i) through (~
(i) one or more monovinyl aromatic monomers
and one or more aliphatic conjugated
diene monomers;
(ii) one or more monovinyl aromatic monomers,
one or more aliphatic conjugated diene
WO9ltl7201 P~T/US91/02606
:~ ~5~ ~838~
monomers and one or more acrylate
monomers;
(iii) one or more monovinyl aromatic monomers
and one or more acrylate monomers;
(iv) one or more acrylate monomers;
~v) one or more ~inylidene halide and one or
more bu~adiene monomers; and
(vi) one or more vinyl halide monomers.
Another important embodiment of the instant
invention is a process for preparing an adhesive which
comprises:
(a) emulsion polymerizing one or more
monoethylenically unsaturated carboxylic
acid monomers with a group of one or more
comonomers
to form a polymeric latex in the presence of:
(i) a stabilizing amount of a surfactant in
2~ an acid form or an ammonium salt form
and optionally a sodium salt surfactant
in an amount not to exceed 0.3 parts per
hundred parts monomer, and
(ii) an initiating amount of ammonium
persulfate and optionally potassium or
sodium persulfate in an amount of up to
1.75 parts per 100 parts monomer; and
(b) stabilizing the polymer prior to stripping
with ammonium hydroxide; and
Wogl/t~201 PCT/US91/02606
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3o~ `
c) adding a wetting agent to the latex to
form an adhesive in an amount of ~rom 0~5
to 6.0 weight percent based on the total
weight o~ the adhesive.
The comonomer group is one of groups (i~ throu~h ~vi):
(i) one or more monovinyl aromatic monomers
and one or more aliphatic conjugated
diene monomers:
(ii) cne or more monovinyl aromatic monomers,
one or more aliphatic conjugated diene
monomers and one or more acrylate
monomers;
(iii) one or more monovinyl aromatic monomers
and one or more acrylate monomers;
(iv) one or more acrylate monomers;
(v) one or more vinylidene halide and one or
more butadiene monomers; and
(vi) one or more vinyl halide monomers.
Typical monomers that could be employed to
produce homopolymer or copolymer latexes to be used in a
system of the present invention, include monovinyl
aromatic monomer, aliphatic conjugated diene, acrylate
monomer t a vinylidene halide or vinyl halide monomer,
vinyl esters of carboxyl acids containing from 1 to 18
carbon atoms, such as vinyl acetate or vinyl stearate,
methacrylonitrile and acrylonitrile. Optimally a
monoethylenically unsaturated carboxylic acid monomer is
3~
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"``` 2083~'17
used. Crosslinking agents such as divinylbenzene and
ethylene glycol dimethacrylate could also be used.
Representative late~ compositions include
styrene~butadiene copolymers; vinyl acetate homopolymer
and copolymers; vinylidene chloride~butadiene
copolymers; vinylidene chloride copolymers; vinyl
chloride copolymers; styreneiacrylate and methacrylate
copol~mers; and acrylate and methacrylate homopolymers
and copolymers. Typical preferred examples of latexes
which oan be employed in adhesives of the present
invention are styrene-butadiene latexes and carboxylated
styrene-butadiene latexes similar to those disclosed in
U.S. Patent 4,396,453, which is hereby incorporated by
reference.
The term "monovinyl aromatic monomer", as used
herein, is meant to include those monomers with a
radical of the formula:
R
CH2=C-
(wherein R is hydrogen or a lower alkyl such as an alkyl
having from 1 to 4 carbon atoms) attached directly to an
aromatic nucleus containing from 6 to 10 carbon atoms,
including those wherein the aromatic nucleus is
substituted with alkyl or halogen substituents. The
preferred monomers are styrene and vinyltoluene.
The term '`aliphatic conjugated diene", as used
herein, is meant to in~lude compounds such as
1,3-butadiene, 2-methyl-1,3-butadiene, piperylene
(1,3-pentadiene). and other hydrocarbon analogs of
1,3-butadiene.
WO91/17201 PCT/US91/02606
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?,~
"Vinylidene halides" and "vinyl halides"
suitable for this invention include vinylidene chloride
and vinyl chloride~ which are highly preferred~
Vinylidene bromides and vinyl bromide can also be
employed.
The term "acrylate~", as used herein~ is meant
to include the acrylate or methacrylate monomers~
Additionally, the acrylates can include acids, esters,
amides, and substituted derivatives thereof. Generally,
the preferred acrylates are Cl-Cg alkyl acrylates or
methacrylates. Examples of such acrylates include butyl
acrylate, 2-hexyl acrylate, tert-butyl acrylate,
methylmethacrylate, butylmethacrylate,
hexylmethacrylate, isobutylmethacrylate, and
isopropylmethacrylate. The preferred acrylates are
butyl acrylate and methylmethacrylate.
The term "monoethylenically unsaturated
carboxylic acid monomer", as used herein, is meant to
include those monocarboxylic monomers such as acrylic
acid, and methacrylic acid; dicarboxylic monomers such
as itaconic acid, fumaric acid, maleic acid, and their
monoesters. The comparatively higher pKa acids are
acrylic and methacrylic acid and the relatively lower
PKa value acids are itaconic, fumaric and maleic. The
most practical acids and therefore the most preferred
monomers for incorporation into the latex polymers are
acrylic, itaconic, and fumaric~
The amount of monoethylenically unsaturated
carboxylic acid monomer typically present in a latex
particle can vary from 1.0 to 8.0 parts based on total
monomer present in the particle. The preferred amount
of monoethylenically unsaturated carboxylic acid monomer
WO91/17201 PCT/US91/02606
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83~7
present in a latex particle is from 1.0 to 3.0 parts
based on total monomer present in the particle. The
optimal amount of acid will vary depending on the type
of acid utilized and the properties the latex is meant
to impart in a given end use. However. a more preferred
amount of acid present is 2.5 parts based on total
monomer present in the particle.
The most preferred copolymer latexes o~ the
present invention are prepared as carbo~ylated
styrene/butadiene, carboxylated acrylate and
carboxylated styrene~acrylate latexes in various ratios.
The typical optimum ratios for these latex
monomers are: (1) for carboxylated styrene/butadiene,
20/80 to 65/35 by weight and (2) for styrene/acrylate
latexes, depending on the acrylate chosen, 10/90 to
50/50 by weight.
Many emulsion polymerization processes utilize
salt forms of surfactants which cause water-sensitivity
in the resultant latex, such as potassium and sodium
salt surfactants; the most common are sodium salt
surfactants which significantly contribute to the
2~ stability of the latex system but are thought to cause
water-sensitivity in the resultant latex.
The present process calls for use of volatile
salt forms of surfactants such as ammonium salt
3 surfactants or surfactants in the acid form which are
thought to decrease the sensitivity of the resultant
latex without sacrificing the stability of the latex
system. The present process will yield water-resistant
3~ latexes in the presence of sodium salt surfactants, so
long as the amount of sodium salt surfactant does not
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exceed ~.50 parts based on one hundred parts monomer.
Preferably the amount of sodium salt surfactant will not
exceed 0.30 parts based on one hundred parts monomer.
Any non-sodium salt or non-potassium salt
surfactant which does not inhibit watPr-resistance
properties in the resultant latex, can be used in the
present invention. One example of such ~ surfactant is
an ammonium salt of dodecyl sul~onated phenyl ether.
The acid form of the surfactant or the ammonium
salt surfaotant can typically be present in an amount
sufficient to stabilize the latex which is dependent on
the polymerization variables for preparing the latex. A
stabilizing amount is therefore known in the art as
being typically dependent on the types and amounts of
initiators, desired latex particle size and acid monomer
used in the polymerization. An amount of ammonium salt
surfactant which can be considered a stabilizing amount
is in the range of from 0.1 to 3.0 parts based on one
hundred parts monomer. The ammonium salt surfactant can
also be a post-additive to the latex prior to stripping
the latex.
2~ ~ ~
Sodium hydroxlde lS also a typical
polymerization additive as well as post-additive; the
presence of sodium hydroxide is also thought to inhibit
the water-resistance of the resultant latex. However,
when neutralizing the latex, the sodium hydroxide is
advantageously thought to sufficiently ionize carboxyl
groups of high pKa carboxylio acid monomers which
thereby impart stability to the latex. Combining high
PKa acid monomers with lower pKa acid monomers enables
3~ ammonium hydroxide to be substituted for sodium
hydroxide for neutralization to increase the water-
WO 91/1720~ PCltlJS91/0~606
(i". -11- 2~8~8'~
resistance of the latex without sacrificing the end use
benefits of using high pKa acid monomers. For example~
where acrylic acid, which is a high pKa acid~ is used as
a carboxylic acid monomer for the latex, itaconic acid
ean be incorporated as well without sacrifieing the
benefits of using the acrylic acid monomer and without
sacrificing ionization of the carboxyl groups.
The most practical high PKa acid ~or use as a
carboxylic acid monomer is acrylic acid and the most
practical lower p~a acids are itaconic and ~umaric
acids~ If acrylic acid is incorporated as a carboxylic
acid monomer of the latex and ammonium hydroxide is used
as the pre-stripping additive, itaconic or ~umaric acid
will be preferred acids to use in combination with
acrylic acid. The ratio of acrylic acid to itaconic
acid will be in the range of from 16 to 1 to 2.0 to 1.
The ratio of acrylic acid to ~umaric acid will also
typically be in the range of from 16 to 1 to 5 to 1. A
mixture of itaconic and fumaric can also be mixed with
the acrylic acid in similar ratios.
The conventional post-additive neutralizing
agent in the art is sodium hydroxide. In the present
process the post-additive neutralizing agent will be
ammonium hydroxide rather than sodium hydroxide. The
ammonium hydroxide will typically be post-added to bring
the pH of the system up to stabilize the latex; such an
amount is typically dependent on the type and amou`nt of
acid monomer incorporated in the system, but is
typically in the range of from 0.3 to 3.5 parts based on
one hundred parts monomer. Preferably the range is from
0.3 to 1.0 parts when about 3 parts of carboxylic acid
monomer is used and from 1. 0 to 3.5 parts when between
WO91/17201 ~ PCT/US91/~2606
~ A~ 12
3 and 8 parts of acid monomer is used based on one
hundred parts monomer.
Similarly. typical polymerization processes
utilize initiators. such as sodium and potassium
persulfate, which are also thought to contribute to the
water-sensitivity of a latex prepared from such
processes~ The present invention provides for the use
of ammonium persul~ate as the optimal initiator ~or
emulsion polymerizing water-resistant latexes. An
initiating amount of ammonium persulfate initiator is
that amount conventionally know in the art which is
necessary to begin polymerization o~ the monomers during
the polymerization process. Such an amount is typically
in the range of from 0.2 to 3~0 parts and is optimally
in the range of from 0.25 to 2.0 parts based on total
parts monomer.
Initiators such as sodium or potassium
persulfate can be present in the polymerization proeess
but optimally should not exceed a level of greater than
1.75 parts based on one hundred parts moromer.
The Latex as an Adhesive
The latex of the present invention can be
utilized as a water-resistant adhesive and can be
combined with a suitable wetting-agent to enhance such
adhesive properties. Examples of such wetting-agents
are non-surfactant or non-detergent type wetting-agents
conventionally known in the art such as diols and other
polyols. The most preferred wetting-agents are the diol
based wetting-agent
Typically, such wetting agents are used in
amounts of from 0.5 to 6.0 weight percent based on the
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total weight o~ the adhesive~ The more preferred range
of wetting agent present in the adhesive is from 1 to 4
and the most preferred range of wetting agent in the
adhesive is from 2 to 4 weight percent based on total
weight of the adhesive.
The term "laminate" as used herein~ is meant to
includa structures which are manufaetured by lamination,
using the present late~ system as the laminating
adhesive. A laminate structure is typically comprised
of substrates which are laminated to the same or
different substrate. The film laminate structure is
typically comprised of films which are laminated to each
other by coating the primary film or web with the
present adhesi~e. The secondary web is then laminated
to the primary web after the adhesive is dried.
The term "substrate" means any solid material
having a surface which can be adhered to a complimentary
surface of the same or different substrate with the
present latex and a diol based wetting agent acting as
an adhesive formulation. The term substrate is
inclusive of any type of naturally occurring and
synthetic solid materials. Representative examples of
such solids and their forms include the following:
plastic, plastic film, paper, paperboard, fabrics, wood,
glass, ceramic, metal. foil, metallized plastio film, or
most any other solid in the form of a film, sheet, board
or block.
The term "plastic substrates" is inclusive of
all eonventional plastic substrates. for example,
polyolefin films, such as polypropylene and
3~
WO91/17201 PCT/~S91/02606
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polyethylene~ as well as polyester film or polyamide
film~ or metallized polyester or polypropylene films.
Plastic substrates generally have low energy
surfaces and are difficult to adhere to other
substrates. Therefore. the surfaces are normally
activated by flame oxidation, corona discharge, and
chemical etching or primer coatings in an attempt to
improve adhesion.
The P eParation of the Polymeric Latex
The polymeric latex is prepared by conventional
emulsion polymeri2ation techniques. Water and a seed
latex are introduced into a reactor equipped with lab
pumps to deliver monomer and aqueous feeds. The reactor
is purged with nitrogen and heated. Over a four hour
period is added two monomer streams and a third stream
containing water, the ammonium salt aqueous surfactant
and ammonium persulfate (or equivalent initiator(s) for
producing water-resistant latex). Following the
addition of the monomer streams and aqueous streams, the
reaction mixture is sustained at a heated temperature
for one additional hour and then cooled. The resulting
2~ latex will be neutralized with ammonium hydroxide to a
pH of at least 6. The latex is then stripped to remove
unreacted monomer.
The peel adhesion for plastic film to plastic
film is measured by a T-Peel test (ASTM D-1876-72) on an
Instron.
Although as specified some of the laSexes in
the following examples are prepared without added
3~ surfacSant present, these latexes are vulnerable to
instability and are prepared without surfactant for
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purposes of comparison. The practice of the process
would conventionally entail the use of surfactant as
someone familiar with latex preparation would recognize.
Further, the latexes from the following
Examples 1-6 are prepared using approximately 0.7 parts
of sodium persul~ate initiator based on 100 parts
monomer~
o E~amDle 1
A styrene/butadiene~acrylie acid ~in about a
50f50 ratio with about 2 parts aeid) latex is prepared
according to a conventional recipe, however, no
surfa~tant is used in the recipe and ammonium hydroxide
is used as the neutralizin~ agent for the example latex.
Five parts of a diol based wetting-agent is added to the
ammonium neutralized latexes~ The comparative latex is
made similarly but with surfactant: 1.0 part sodium salt
of dodecyl sulphonated phenyl ether. Both the example
and comparative example formulations are diluted with
water to 34 percent solids and evaluated as film
laminating adhesives. The formulated adhesives are
coated to film using conventional gravure coating
methods to give eoat weights approximately 1 to 1.5 lbs.
per 3000 sq. ft. of film. The coated film is dried in a
forced air oven. The adhesive coated film is laminated
to ~econdary film under pressure and heat. The
laminates are cut in 1 inch strips and exposed to 100F
and 100 percent relative humidity environment for a
week. The humid peel adhesion is determined using
Instron T-peel test (ASTM D-1876 -72) at 12
inches/minutes.
Laminate 1 is prepared by drawing the adhesive
down a corona treated polypropylene film (available from
WOgl/17201 PCT/US9~/02606
~3~ -16- ~
Hercules as Hercules B-523) and is laminated to the
polypropylene side of a polyvinylidene chloride treated
70 gauge polypropylene film (available from ~obil as
Mobil 70 PXS). Laminate 2 is prepared by coating the
adhesive on metallized polyester film and laminating to
the ethylene vinyl acetate side of ~ ethylene vinyl
aoetate/Surlyn* coextruded film (~DuPont trademark)~
Laminate 3 is prepared by coating the polyvinylidene
chloride side of a polyvinylidene chloride~oriented
polyethylene terephthalate film and is laminated to the
ethylene vinyl acetate side of an ethylene vinyl
acetate/Surlyn~ coextruded film (~DuPont trademark).
The results are shown in Table 1. The examples
having any sodium salt surfactant present, whether by
being prepared in the presence of the surfactant or by
post-addition of surfactant, show significantly less
tolerance to the peel adhesion test which measures the
strength of the bond the adhesive forms thereby
indicating that the stronger bonds are exhibited by the
laminates which have no sodium salt of dodecyl
sulphonated phenyl ether present.
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.
TABLE I
_
Adhesive Laminate Laminate Laminate
Formulation 1 2 3
Example 1 Film 3~0 1~7
no sodium salt of Teargms/inch gms/inch
dodecyl
sulphonated phenyl
ether present
1 n _
Example 1 210 220 16~
plus a post- gms~inch gms~inch gms~inch
addition of 0~5
parts sodium salt
of dodecyl
sulphonated phenyl
ether
Comparative 100 57 40
Example 1 gms/inch gms/inch ~ms/inch
Prepared with 1.0
part sodium sàlt
of dodecyl
sulphonated phenyl
ether present
As is shown in the Table I~ a minor amount of a
sodium salt of dodecyl sulphonated phenyl ether
surfactant will yield water-resistant adhesive bonds,
2~ however, the bond is not as strong as one prepared
without the sodium salt of dodecyl sulphonated phenyl
ether~ If more than a minor amount of the sodium salt
of dodecyl sulphonated phenyl ether is added the water-
resistance of adhesive is not acceptable as shown in the
Comparative Example 1
Example 2
This example compares the effect of using
conventional sodium salt of dodecyl sulphonated phenyl
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ether as a surfactant and an ammonium salt of dodecyl
sulphonated phenyl ether as a surfactant.
The latex of Example 2 is prepared similarly to
the latex of Example 1, however, an ammonium salt of
dodecyl sulphonated phenyl ether is used as a
~surfactant. The latex o~ Comparative Example 2 is also
prepared similarly the latex o~ Example 1~ however,
using a sodium salt of dodecyl sulphonated phenyl ether
as a surfactant at approximately 0.5 parts based on 100
parts monomer. Although the Comparative Example 2 only
uses a minor amount of sodium salt of dodecyl
sulphonated phenyl ether, and the latexes are ammonium
hydroxide neutralized, the adhesive properties of the
Comparative Example 2 are not as desirable as those
exhibited by Example 2 prepared with the ammonium salt
of dodecyl sulphonated phenyl ether surfactant.
Laminate 1 is prepared by drawing the adhesive
down a corona treated polypropylene film (available from
Hercules as Hercules B-523) and is laminated to the
polypropylene side of a polyvinylidene chloride treated
70 gauge polypropylene film (available from Mobil as
2~ Mobil 70 PXS). Laminate 2 is prepared by coating the
adhesive on metallized polyester film and laminatin~ to
medium density polyethylene film.
The laminates were allowed to cure at 100F for
18 hours. The laminates are cut in 1 inch strips and
dry peel adhesion is then measured. The 1 inch strips
are exposed to 100~F 100 percent relative humidity ~or
five days for the humid peel adhesion evaluation. The
humid peel adhesion is determined using Instron T-peel
test (ASTM D-1876-72) at 12 inches~minutes.
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TABLE II
Formulation Laminate 1 Laminate 2
Example 2 233 gms/in 361 gms~in
0.5 parts
ammonium salt of
dodecyl
sulphonated phenyl
ether present _
Comparative 162 gmsiin 8~ gms~in
Example 2
0.5 parts
sodium salt of
dodecyl
sulphonated phenyl
ether present
. .. .__
The data in Table II demonstrate the large
delta between the bond strength of a latex adhesive
prepared with an ammonium salt surfactant and a latex
adhesive prepared with a sodium salt surfactant. The
sodium salt surfactant latex does not have the desirable
bond strength of the ammonium salt surfactant latex.
The data in Table II demonstrate that this
effect is even greater for a laminate prepared with a
metal film. Laminate 2, than for a laminate prepared
with a plastic film, Laminate 1.
Example 3
This example demonstrates the effect of the
type of neutralizing agent on humid peel adhesion
strength. The latex is prepared similarly to the latex
of Example 1. The latexes are prepared without
surfactant and neutralized according to the schedule in
Table III. The adhesive is formulated from the latex
and four parts of a diol wetting agent and diluted to
34 percent solids.
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Laminate 1 is prepared by drawing the adhesive
down a corona treated polypropylene film ~availabl~ ~rom
Hercules as Hercules B-523) and is laminated to the
polypropylene side of a polyvinylidene chloride treated
70 gauge polypropylene film (available from Mobil as
Mobil 70 PXS~ Laminate 2 is prepared by coating the
adhesive on metallized polyester film and laminating to
medium density polyethylene ~ilm~
The laminates are ~llowed to cure at 100F for
18 hours. The laminates are cut in 1 inch strips and
dry peel adhesion is then measured. The 1 inch strips
are exposed to 100F 100 percent relative humidity for
five days prior to the humid peel adhesion evaluation.
The humid peel adhesion is determined using Instron
T-peel test (ASTM D-1876-72) at 12 inchesiminutes.
Results are shown in Table III.
` TABLE III
. . . _
Adhesive Laminate 1 Laminate 2
_ _
ammonium hydroxide 168 gmsfinch 373 gms/inch
neutralized~ no
surfactant
. __ ............. ._
sodium hydroxide 12g gms/inch 65 gms/inch
neutralized plus
0.485 parts NaOH,
no surfactant
. _
sodium hydroxide 19 gms~inch29 gms/inch
neutralized
0~485 parts NaOH
0.5 sodium salt of
dodecyl
sulphonated phenyl
ether _ -__
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Table III illustrates that by having both a
sodium salt as a surfactant and a sodium hydroxide
neutralizing agent present in the latex~ the humid
adhesive bond strength is unacceptable, therefore the
latex water-resistance of the adhesive is unacceptable.
Example 4
A series o~ ammonium hydroxide neutrali2ed
latexes are prepared similarly in composition to the
late~ of Example 1, without surfactant present.
However, the acid component ratios of acrylic acid and
itaconic acid are varied according to the schedule in
Table IV. These latexes are diluted to approximately 36
percent solids. Three parts of a diol wetting agent is
also added to the latexes.
The laminates are prepared by drawing the
adhesive down a corona treated polypropylene film
(available from Hercules as Hercules B-523) and
laminated to the polypropylene side of a polyvinylidene
chloride treated 70 gauge polypropylene film (available
from Mobil as Mobil 70 PXS).
The laminate is prepared by drawing the
adhesive down a corona treated polypropylene film
(available from Hercules as Hercules B-523) and is
laminated to the polypropylene side of a polyvinylidene
chloride treated 70 gauge polypropylene ~ilm (available
from Mobil as Mobil 70 PXS).
The laminates ~ere allowed to cure at 100~ F for
1~ hours~ The laminates are cut in 1 inch strips and
dry peel adhesion is then measured. The 1 inch strips
are exposed to 100C F lOOp relative humidity for five
days prior to the humid peel adhesion evaluation. The
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~3~ -22- ~ `.
humid peel adhesion is determined using Instron T-peel
test (ASTM D-1876-72) at 12 inchesiminutes. The results
are shown in Table IV~
TABLE IV
Acid Modification Peel Peel Peel
Parts Acid per 100 Adhesion Adhesion Adhesion
parts monomer gms~in gms/in gmstin
. . _
Acrylic Itaconic
10 Acid Acid Dry Humid Dry~Humid
, . .
~5 0.~ 210 218 1.04
2.0 0.5 206 173 0.84
1.?50.75 224 186 0.83
__ 1.0 190 161 0.85
0 2.2 215 165 0.77
Table IV shows the Acrylic Acid modified latex
retains the optimum bond strength as shown in the
Dry/Humid ratio column. However, the use of acrylic
acid alone in combination with volatile bases, such as
ammonium hydroxide raSher `than sodium hydroxide, can
render the latex vulnerable to instability. Itaconic
25 Acid alone exhibits the least desirable bond strength
r retention. The various combinations of acrylic and
itaconic yield acceptable bond strength retention and
can retain stability even when neutralized with ammonium
hydroxide.
ExamDle 5
Similarly to Example 4, a series of latexes are
prepared varying the ratios of acrylic acid to fumaric
acid. These latexes are formulated and evaluated
3~ similarly to Example 4.
WO91/17201 PCT/~'S91/02606
i~ -23- ~0838`17
The laminate is prepared by drawing the
adhesive down a corona treated polypropylene film
(available from Hercules as Hercules B-523) and is
laminated to the polypropylene side of a polyvinylidene
chloride treated 70 gauge polypropylene film (available
rom Mobil as Mobil 70 PXS).
The laminates were allowed to cure at 100F for
18 hours~ The laminates are cut in 1 inch strips and
dry peel adhesion is then measured~ The 1 inch strips
are exposed to 100~F 100 percent relative humidity for
five days prior to the humid peel adhesion evaluation.
The humid peel adhesion is determined usin~ Instron
T-peel test (ASTM D-1876-72) at 12 inches/minutes, The
results are shown in Table V.
TABLE V
Parts Acid Based on 100 Peel Adhesion gms/in
20Parts ~ tonomer .
Acrylic Fumaric Dry Humid Dry/Humid
2.5 0 216 220 1.02
2.0 0.5 195 167 0.86
25ComparativeComparative 199 127 0.64
. Example 5 0.75 .
The results can be similarly compared to the
3o results in Example 4. Fumaric Acid has a lower PKa to
acrylic and there~ore. does not perform as well as the
pure acrylic acid modified latex as shown in Example 4.
~xamDle 6
3_ A latex with the monomer composition of methyl
methacrylate/butyl acrylate/acrylic acid (that is a
20/80 ratio with approximately 2 parts total acid) is
WO91/17201 ~ ~ PCT/VS91/02606
~ 24-
prepared without surfaotant present and neutralized in
the presence of ammonium hydroxide. A comparative
adhesive is similarly formulated but with 1.0 part
sodium salt of dodecyl sulphonated phenyl ether. Both
the latexes are than formulated with 3 parts of a diol
wetting agent and evaluated as described in Example 4.
The results are shown in Table VI.
Laminate 1 is prepared by drawing the adhesive
down a corona treated polypropylene film ~available ~rom
Hercules as Hercules B-523) and is laminated to the
polypropylene side of a polyvinylidene ohloride treated
70 gauge polypropylene film (available ~rom Mobil as
Mobil 70 PXS). Laminate 2 is prepared by coating the
adhesive on metallized polyester film and laminating to
medium density polyethylene film.
The laminates were allowed to eure at 100F for
18 hours. The laminates are cut in 1 ineh strips and
dry peel adhesion is then measured. The 1 inch strips
are exposed to 100F 100 peroent relative humidity for
five days prior to the humid peel adhesion evaluation.
The humid peel adhesion is determined using Instron
T-peel test (ASTM D-1876-72) at 12 inohes/minutes. The
results are shown in Table VI.
WO 91/17201 PCI`/US91/02606
25- 2U838
TABLE VI
Laminate 1 Laminate 2
peel adhesion inpeel adhesion in
Adhesive gms/inch gms/inch
Formulation
Dry Humid HDurmYi~d Dry Humid Humid
..... ~ __
Example 6 175 170 0~97 250 200 0.8
Acrylic Latex ~ _
10 Comparative 200 150 0~75 210 10 C.0
Example ~
Acrylic Latex
+ 1~0 part
sodium salt of
dodecyl
sulphonated
15 phenyl ether
post-added ~
As is shown in Table VI, the retention of
adhesive bond strength for the comparative latex having
1.0 parts of post-added sodium salt surfactant is
unacceptably low. The latex prepared without surfactant
performs acceptably.
Example 7
This example compares the effect of using
conventional sodium persulfate as an initiator and an
ammonium persulfate as an initiator. The latex of
Example 7 is prepared similarly to the latex of
Example 1. Laminate 1 is prepared as described in
Example 1 by coating the adhesive on metallized
polyester film and laminating adhesive to the ethylene
vinyl acetate side of a ethylene viny acetate/Surlyn*
coextruded film (* Dupont trademark).
The laminates were allowed to cure at 100F for
18 hours. The laminates are cut in 1 inch strips and
W O 91/17201 PC~r/US91/02606
9 ~3~ -26- ~
dry peel adhesion is then measured. The 1 inch strips
are exposed to 100E 100 percent relative humidity for
five days prior to the humid peel adhesion evaluation.
The humid peel adhesion is determined using Instron
T-peel test (ASTM D-1876-72) at 12 inches~minutes. The
results are shown in Table VII~
The latex prepared with ammonium persulfate
initiator exhibits hi~her desirable peel adhesion than
the latex prepared with sodium persulfate.
TABLE VII
Initiator Type Laminate
Based on 100 psrtsPeel Adhesion
monomer gms~in
Example 7 410
0.7 Parts Ammonium
Persulfate
Comparative Example 7 355
0.7 Parts Sodium
Persulfate
3o
