Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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"EASY-CLEAN" VINYL ACETATE ADHESI~E COMPOSITION
Improved vinyl acetate homo- and copolymer-based emulsion adhesives
characterized by superior '!easy-clean" properties are prepared by the
addition thereto of specific water soluble, ionic salts. Furthermore,
when such salts are added to those emulsions adhesives which are suitable
for remoistening applications, the resultant products are also charac-
terized by improved "lay-flat" performance.
Vinyl acetate-based emulsion adhesives are used for a wide range
of applications in industry. Typically, they are used in remoistening,
stenciling, laminating, packaging and other high speed adhesive appli-
cations. It will be recognized that the high speed machining of theseadhesives results in the formation of deposits of dried adhesive on the
various machine parts which eventually interferes with the machining.
Therefore, the need to clean off these deposits quickly and simply with
water (a property referred to as "easy-clean") and thereby minimi7e shut-
down time is being emphasized by adhesive users. Heretofore, the "easy-
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clean" properties have been achieved, for example, by the use of rela-
tively large amounts of polyvinyl alcohol. However, polyvinyl alcohol
is expensive and, in come cases, the use thereof may undesirably thicken
the adhesive or may react unfavorably with the substrate to be adhered
as in the case of "patch-gumming" of polystyrene panels in the manu-
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facturing of envelopes.
In a related area, certain vinyl acetate-based emulsion adhesives
also require a degree of water-sensitivity in order to provide for
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remoistenable applications. However, the use of these aqueous emulsions
to produce remoistenable adhesives results in the swelling of the paper
fibers and eventual curling of the substrate, a problem which is further
aggravated upon drying. Attempts have been made to avoid or minimize
the curling by the addition of various humectants or plasticizers,
however, none, to date, have resulted in the production of a satisfactory
"lay-flat" aqueous adhesive. The latter property has been achieved
only by passing the curled substrate over knife edges or rollers in
order to destroy the continuity of the adhesive film and thereby allow
the substrate to resume its flat configuration.
The present invention provides vinyl acetate homo- and copolymer-
based aqueous emulsion adhesives which are characterized by improved
easy-clean properties. It also provides specific adhesives particularly
useful for "patch gumming" or stenciling applications. It further
provides specific adhesives containing partially hydrolyzed polyvinyl
alcohol which, in addition to possessing easy-clean properties, are
also useful as remoistenable adhesives which mdintain their lay-flat
configuration even after drying. The addition of specific
water-soluble, ior,ic salts to the conventional vinyl acetate-based
aqueous emulsions produces the superior "easy-clean" and, in certain
cases, "lay-flat" performance.
The aqueous adhesive composition characterized by "easy-clean"
properties colnprises, per 100 parts by weight of the -total composition,
50~99.5 parts of an aqueous vinyl acetate homo- or copolymer emulsion,
0.5-15 parts of a salt selected from the group consisting of calcium
chloride, calcium nitrate, ~agnesium chloride, magnesium nitrate,
aluminum chloride, aluminum nitrate, ammonium chloride, ammonium acetate,
potassium acetate and blends thereof, 0-35 parts humectant, 0-35 parts
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plasticizer, 0-35 parts solvent, and 0-20 parts water soluble protective
colloid, wherein the total of the last four components comprises 0-49.5
parts by weight per 100 parts by weight of the total formulation. The
adhesive composition useful for "patch gumming" operations comprises,
per 100 parts by weight of the total composition, 50-89.5 parts of an
aqueous vinyl acetate copolymer emulsion, 0.5-15 parts of a salt
selected from the group consisting of calcium chloride, calcium nitrate,
magensium chloride, magesium nitrate, aluminum chloride, aluminum
nitrate, ammonium chloride, ammonium acetate, potassium acetate and
blends thereof, 5-20 parts plasticizer, and 5-35 parts humectant. The
remoistenable adhesive composition characterized by improved "lay-flat"
properties comprises, per 100 parts by weight of the total composition~
50-89.5 parts of an aqueous vinyl acetate homo- or copolymer emulsion,
0.5-15 parts of a salt selected from the group consisting of calcium
chloride, calcium nitrate, maynesium chloride, magnesiulll nitrate,
aluminum chloride, aluminum nitrate, ammonium chloride, ammonium
acetate, potassium acetate and blends thereof, 5-15 parts partially
hydrolyzed polyvinyl alcohol, and 5-30 parts humectant.
The specific salts to be utilized herein may be generally class-
ified as hygroscopic, deliquesent, water soluble, ionic salts. Speci-
fically preferred for reasons of effectiYeness, concentration, cost and
availability are calcium chloride, calcium nitrate, magnesium chloride,
magnesium nitrate, aluminum chloride, aluminum nitrate, ammonium
chloride, amrnonium acetate and potassium acetate. Blends of these
salts or mixtures of these salts with other inorganic salts not listed
above may also be used herein. The amount of the salt used will vary
depending upon the specific salt chosen, the vinyl acetate base, as
well as the end use for which the system is intended; however, the
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amount will generally be within the range of 0.5 to 15 parts by weight
per 100 parts of the total formulation.
Any conventional vinyl acetate based emulsion adhesive may benefit
from the use of the salts in accordance wi-th the teachings herein.
Formulae for such ~nulsions are well known in the art and generally
include vinyl acetate homopolymer emulsions as well as emulsions of
vinyl acetate copolymerized with up to about 50% by weight of a
copolymerizable monolner or mixtures thereof. In particular, copolymers
of vinyl acetate with ethylene as well as with acrylate and maleate
esters are widely used in industrial applications. These emulsions are
commercially a~!ailable or easily prepared and are generally used in the
form of aqueous emulsions at about 55% solids levels although higher or
lower levels could be employed. In considering the relative amounts of
components present in the adhesive compositions herein, wherein amounts
are based as 100 parts by weight, it will be understood that the water
used in the vinyl acetate emulsions is included in all calculations.
It will be recognized that the adhesives herein are formulated in
accordance with known techniques and, dependiny upon the desired use,
may include plasticizers such as, for example, polyethylene glycol,
dibutyl phthalate, butyl benzyl phthalate, propylene glycol dibenzoate,
triethylene glycol polyester of benzoic acid and phthalic acid, alkyd
resin plasticizers, etc~; humectants such as glycerin, triethylene
glycol, propylene glycol and urea; water soluble polymers or protective
colloids such as polyvinyl alcohol, polyvinyl pyrrolidine, polyvinyl
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pyrrolidine-acetate copolymer, polyacrylamide, etc.; solvents like
toluene, 1,1,1-trichloroethane, etc,, as well as mixtures of any of the
above. Generally the humectants, plastici~ers and solvents may be
present in amounts varying from 0 to 35 parts per 100 parts of the
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total composition with the protective colloid used in amounts up to
about 20 parts. In all cases, however, the total amount of the above
described optional additives will represent less than ~9.5 parts per
100 parts of the total formulation.
In particular, the vinyl acetate emulsion adhesives suitable for
use in remoistening applications will usually contain approximately 5
to 15 parts partially hydrolyzed polyvinyl alcohol and 5-30 parts hume-
ctant per 100 parts total formulation. The alcohol is often used in
aqueous solution form, with 40% solutions being the most conveniently
made. (The water present in solutions is not included in the calcu-
lations herein.)
In addition, other additives known in the adhesive art may also
be present in minor amounts. These additives would include, for
example, fillers such as clay and chalk; antioxidants such as butylated
hydroxyanisole and butylated hydroxytoluene; preserva-tiYes such as
sodium benzoate and formaldehyde; lubricants; waxes; pigments; dyes;
defoamers; flavoring agen-ts; chelating agen-ts; anti-corrosion agents;
perfumes; etc.
The resultant adhesive compositions of the present invention are
usually enployed at solids leve1s of at least about 30%, preferably 50%
or higher, although addi-tional water may be post-added via the addition
of protective colloids or in order to adjust the final viscosity for
proper machining.
Those skilled in the art will recognize that the specific formula-
tions chosen as well as the choice of additives, if any, will vary
depending upon the end use to which the particular adhesive or coating
is to be employed.
Adhesives formulated with these specific salts in accordance with
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the teachings herein may be applied using suitable conventional
techniques. The adhesives show no appreciable change in application,
machining or adhesive properties while requiring only an effortless
cleaning with water of the dried adhesive spills on the machines and
other applications apparatus.
It is noted that certain salts, including some of the salts
utilized herein, have preYiously been employed as stabilizers and to
prevent "pasting-up" of starch-based adhesiYes (a premature setting or
forming of the adhesive in a storage pot) or to modify soft pressure
sensitive polyacrylate and related copolymer emulsions in which the
salt serves to crosslink the dried film via carboxyl or other reactive
groups on the polymer to give higher cohesive values and insolubility,
properties contrary to those required in the present invention. For
this reason, adhesive systems containing carboxyl or related functional
groups which react with metal ions cannot be emplo~ed for use herein.
Further details of the invention as well as exemplary formulations
will be described below. In the examples all parts are by weight.
EXAMPLE 1
Adhesive formulations were prepared using a vinyl acetate homo-
polymer emulsion (55~O solids) and varying amounts of calcium chloridein order to show the "easy-clean" properties achieved thereby. Thus,
adhesive compositions were formulated as follows:
Samples ~parts)
A B __ C D
Vinyl acetate homopolymer emulsion 100 100 100 100
Calcium chloride 10 5 0.5 -
The adhesives were tested ~or cleaning properties by casting 1 ml
portions of each formulation on glass plates and allowing the coatings
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to dry and aye 1 week. Drops of water were then put on each film and
rubbed comparatively. Samples A, B and C containing the calcium chloride
salt disintegrated readily with formulations A and B containing higher
amounts of salt disintegrating almost immediately while the control D
formulation containing no salt required prolonged rubbing in order to
achieve removal.
EXAMPLE 2
Other conventional adhesive formulations based on 55% solids vinyl
acetate homopolymer and copolymer emulsions were prepared as follows:
Samples ~ parts~
A __B_ _ C D _ E F G H
Vinyl acetate homopolymer 100 100 100 100 100 100 - -
emulsion
Vinyl acetate-acrylate - - - - - - 100 100
copolymer
Butyl benzyl phthalate 10 10 64 6~ 44 44
(Sanitizer 160* - Monsan-to)
Ca!cium chloride 20 - - - - - S
Magnesium chloride - - 18 - 18
1,1,1-Trichloroethane - - - - 20 20
~ hen tested for cleaning properties, the adhesives designa~ed A, C,
E and G were readily rerno~ed from the glass plates using only water as
described in Exarnple 1. Comparatively, Samples B, D, F and H we~e not
easily removed.
EXAMPLE 3
;~ The adhesive formulation described in Sample ~, Example 1 was pre-
~; pared replacing the calcium chloride with calcium nitrate, magnesium
chloride, magnesium nitrate, aluminum chloride, aluminum nitrate, ammonium
chloride, ammonium acetate, potassium acetate, a blend of equal parts
of calcium chloride and magnesium chloride and a blend of equal parts
* Trade Mark
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sodium chloride and calcium chloride. All samples possessed the "easy-
clean" characteristic similar to that of the calcium chloride sample.
EXAMPLE ~
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The following ~ormulations exemplify adhesives useful for "patch
gumming" or stenciling applications such as for window enYelope adhesives
wherein polystyrene inserts or related films are attached to paper
envelopes using high speed stenciling techniques. These adhesives are
generally formulated with aqueous vinyl acetate copolymer emulsions
containing 5-20 parts plasticizer and 5-35 parts humectant per 100 parts
total composition.
Samples (parts)
A _ B C _ D
Vinyl acetate-maleate copolymer - - 100 100
Vinyl acetate-ethylene copolymer 100 100
emulsion (55% solids)
Tiethylene glycol polyester of 23.4 23.424 24
benzoic and phthalic acid
(Hercoflex 900,* a produc~ of
~lercules Chemical Co.)
" 20 Glycerin 28.1 28.164 64
Magnesium chloride 3.1 - 10
When tested, samples A and C containing magnesium chloride were
~` readily cleaned with water while samples B and D which did not contain
salt had to be rubbed excessively in order to remove the dried adhesive.
EXAMPLE S
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In a similar manner, various adhesive formulations were prepared
which are useful for remoistening applications. Calcium chloride was
then added to such systems in order to show the "easy clean" and addi-
tionally, the "lay-flat" properties achieved thereby.
* Trade Mark
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Samples (parts)
A B C D E F G H I J
Vinyl acetate homopolymer 100 100 100 100 100 100 100 100 100 100
emulsion (55% solids)
Glycerin 20 20 20 20 - - 10 10 20 20
40% Aqueous polyvinyl alcohol 20 20 30 30 - - 20 20 50 50
solution (88% hydroly~ed)
Polyoxyethyle~e glycol (600 MW) - - - - 1~ 14 10 10
(Carbowax 600-Union Carbide)
Polyvinyl Pyrrolidines/ - - - - 6 6
vinyl acetate (1:1 ratio)
An alkyd plastici~er (Resoflex - - 3 3
R296* - Cambridge Industries)
Calcium chloride 10 - 10 - 10 - 10 - 10
All the above adhesive samples were coated at 12 lbs./ream on standard
gumming stock paper in the machine direction, air dried and permitted
to set overnight. Thereafter 6" x 4 1/2" (machine direction) cutouts
were taken and observed daily (coated side up) for 1 week to observe
curl or relative lay flat properties. The examples containing the
suitable salt herein started to exhibit a slight convex curl
(considered desirable from a lay-flat aspect); while those samples
which did not contain the salt developed a slight concave curl. At the
end of one week, those samples with salt were still slightly convex
while those control samples without salt were considerably concave,
i.e. had excessive curl.
The "easy-clean" test described in Example 1 was also repeated
using all the above described formulations with those containing salt
exhibiting "easy-clean" properties and those control samples very
difficult to clean.
* Trade Mark
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EXAMPLE 6
The formulation described in Sample A of Example 5 was prepared
using a variety of salts in place of calcium chloride. Thus formula-
tions ~ere prepared with magnesium chloride, magnesium nitrate, calcium
nitrate and a blend of equal parts calcium chloride plus ammonium
aceta-te. When tested as described in Example 5 all Formula-tions pos-
sessed the desired "easy-clean" and "lay flat" properties.
In summary, aqeuous adhesive compositions characteri7ed by "easy-
clean" properties and, in some cases by improYed "patch gumming" and
"lay-flat" properties, are provided.
