Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02377439 2002-06-20
HEAT-ACTIVATABLE ALKALI-REMOVABLE LABELLING SYSTEMS
This patent application is based upon co-pending U.S. Provisional Patent
Applica-
tion Serial No. 60/191,135, filed March 22, 2000, incorporated herein by
reference.
FIELD OF THE INVENTION
This application is directed to coating systems for applying labels to
bottles. More
particularly, this application is directed to heat-activatable, alkali-
removable labelling
systems formed from blends of high acid acrylic resins. The labels produced
can be rapidly
and completely removed in an environmentally friendly manner by heated aqueous
alkaline
solutions.
BACKGROUND OF THE INVENTION
With the increasing emphasis on environmental protection, reduction of
landfill
disposal areas, and the economic advantages of recycling containers, there is
interest in
environmentally friendly labelling systems, especially ones where labels are
removable in
aqueous alkaline solutions. Known alkali-removable labelling systems have been
formulated from alkaline solutions of casein, which systems have the
disadvantages of
degradation and discoloration upon exposure conditions of heat and aging.
Furthermore,
such systems are not thermoplastic, a property that necessitates application
of label
adhesives prepared for these compositions by direct gluing rather than by
melting and heat
activation.
A further deficiency in such known labelling systems has been the slow and
incomplete removal of labels and label adhesives from the containers to which
they have
been attached. Also, in the case of heat-transferred "paperless" labels, the
alkali-removable
protective top coatings have exhibited poor visual appearance resulting from
cracking on
CA 02377439 2002-06-20
aging and developing surface scratches from abrasion encountered during
friction due to the
containers being in close contact while moving on the production line.
Thus, there is a need for better labelling systems in which labels can be
rapidly and
completely removed.
OBJECTS OF THE INVENTION
It is an object of the invention to provide an environmentally friendly
labelling
system.
It is also an object of the invention to provide a heat-activatable, alkali-
removable
labelling system.
It is a further object of the invention to provide a method of producing
abrasion-
resistant, protective topcoats, inks, and heat-activatable adhesive
formulations that produce
non-hazing, clear, glossy films under conditions of pasteurization and
immersion in ice
water.
These and other objects of the invention will become more apparent from the
discussion below.
SUMMARY OF THE IlWENTION
The current invention achieves the desired characteristics of alkali-
removability,
heat activation, and abrasion resistance by utilizing solutions of blends of
high acid acrylic
resins with other harder acrylic resins thereby resulting in formulations low
enough in
viscosity for application by flexagraphic or gravure coaters and presses. The
dried films of
these products have excellent interlayer adhesion, and, in the case of the
adhesive coating,
sufficiently low softening point, high wet tack, non-blocking in the dried
film, and provide
excellent adhesion to plastic, glass, and metal containers.
According to a first embodiment of the invention, a heat-transfer label is
particularly
well-suited for use on silane-treated glass containers of the type that are
subjected to
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pasteurization conditions, regardless of whether the glass containers have
previously been
pre-treated with polyethylene, oleic acid, stearate or the like. The heat-
transfer label
comprises (a) a support portion comprising a sheet of paper overcoated with a
release layer
of polyethylene and (b) a transfer portion over said support portion for
transfer of the
transfer portion from the support portion to an article upon application of
heat to the
support portion while the transfer portion is placed into contact with the
article. The
transfer portion comprises (i) an optionally alkali-removable protective
lacquer layer, (ii) an
optionally alkali-removable ink layer over said protective lacquer layer; and
(iii) an alkali-
removable, heat-activatable adhesive layer over said ink layer. Preferably the
adhesive
layer comprises an adhesive of the type present in a solvent- or water-based
adhesive form
or in a water-based adhesive dispersion. Each layer comprises one or more
acrylic resins.
In a second embodiment of the invention the heat-transfer label comprises (i)
an
optional, optionally alkali-removable protective lacquer layer, (ii) an
optionally alkali-
removable ink layer over said protective lacquer layer, (iii) a substrate, and
(iv) an alkali-
removable, heat-activatable adhesive layer.
According to another aspect of the invention, the heat-transfer label is
particularly
well-suited for use on aluminum cans that have been treated with a highly-
lubricating
acrylic coating or varnish of the type used to prevent scratching and abrasion
of such cans
(said varnish either being used alone or in combination with a white ink),
said heat-transfer
label comprising (a) a support portion comprising a sheet of paper overcoated
with a release
layer of polyethylene and (b) a transfer portion over said support portion for
transfer of the
transfer portion from the support portion to an article upon application of
heat to the
support portion while the transfer portion is placed into contact with the
article.
In addition to being directed to the above-described heat-transfer portion of
the heat-
transfer labels, as well as to the adhesive compositions used to form the
adhesive layers of
the heat-transfer labels, the invention is directed to methods for forming the
adhesive layers
with the aforementioned adhesive compositions, to the adhesive layers formed
using the
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foregoing adhesive compositions, and to methods of labelling surfaces with the
above-
described heat-transfer labels.
It is to be understood that certain terms used herein, such as "on" or "over",
when
used to denote the relative positions of two or more layers of a heat-transfer
label, are
primarily used to denote such relative positions in the context of the way in
which those
layers are situated prior to transfer of the transfer portion of the label to
an article since,
after transfer, the arrangement of layers is inverted as those layers which
were furthest
removed from the associated support sheet are now closest to the labelled
article.
The current invention achieves the desired characteristics of alkali-
removability,
heat activation, and abrasion resistance by utilizing solutions of high acid
acrylic resins
and/or blends with other harder acrylic resins thereby resulting in
formulations low enough
in viscosity for application by flexographic or gravure coaters and presses.
The dried films
of these products have excellent interlayer adhesion, and, in the case of the
adhesive
coating, sufficiently low softening point, high wet tack, non-blocking in the
dried film, and
provide excellent adhesion to plastic, glass, and metal containers.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a schematic cross-sectional view of one embodiment of the invention;
and
Fig. 2 is a schematic cross-sectional view of another embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
The invention herein can perhaps be better appreciated by making reference to
the
drawings. FIG. 1 represents a schematic cross-sectional view of a first
embodiment of a
heat-transfer label according to the invention. Heat-activatable label 10
comprises a
support portion 12 and a transfer portion 14. Support portion 12, in turn,
comprises a
substrate or carrier web 16 overcoated with a polyethylene release layer 18.
Carrier web 16
is typically made of paper or a similarly suitable substrate. Details of the
composition and
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preparation of polyethylene layer 16 are disclosed, for example, in U.S.
Patents Nos.
4,935,300, and 4,927,709, both of which are specifically incorporated herein
by reference.
Label 10 optionally comprises a skim coat 20, which is coated directly on top
of the
entirety of polyethylene layer 18. During label transfer, a small portion of
skim coat 20
may be transferred along with the transfer portion 14 of label 10 onto the
article being
labelled, the amount of skim coat 20 transferred onto the article being
labelled not being
readily discernible.
Transfer portion 14 comprises an optional, optionally alkali-removable,
organic
solvent soluble acrylic protection layer 22 printed directly on top of
polyethylene layer 18
or skim coat 20, an optionally alkali-removable organic solvent soluble ink
design layer 24
printed onto a desired area of protective layer 22, and an alkali-removable,
heat-activatable,
organic solvent soluble acrylic adhesive layer 26 printed onto ink design
layer 24.
In Fig. 2, heat-activatable label 40 comprises an optional, optionally alkali-
removable, organic soluble acrylic protective layer 42, an optionally alkali-
removable,
organic solvent soluble ink design layer 44 printed onto a desired area of
protective layer
42, a substrate layer 46, and an alkali-removable, heat-activatable, organic
solvent soluble
acrylic adhesive layer 48 printed onto substrate layer 46.
The coating compositions utilized in the above-described applications are
comprised
of solutions of single component or blends of acrylic resins having varying
degrees of
alkaline solubility and film hardness. Protective lacquer layer 22 or 42
preferably
comprises one or more suitable alkali-soluble, organic solvent soluble acrylic
resins. One
of the alkaline-soluble acrylic resins found particularly useful in the
formulations is a
proprietary, solid, all acrylic, low molecular weight resin with a Tg of
70° C and an acid
number of 100. This resin, known as CARBOSET 526, is manfactured by B.F.
Goodrich
Specialty Chemicals, 9911 Brecksville Road, Cleveland, Ohio 44141-3247.
A second example of a useful alkaline-soluble acrylic resin is a proprietary,
high
molecular weight (Mw of 12,500) solid, styrene acrylic resin with a Tg of
73° C, an acid
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number of 213 and a ring and ball softening point of 160° C. This
resin, identified as
JONCRYL 67, is manufactured by S.C. Johnson and Sons, Inc., Racine, Wisconsin
53403-
5011.
A third example of an alkaline-soluble, organic solvent soluble, solid acrylic
resin
found useful for this application is a styrene terpolymer with acrylic acid
and acrylic ester
supplied by Belland Inc., 250 Clark Street, North Andover, MA 01845-1018,
under the
name GBC 8504.
Two additional hard, high molecular weight acrylic resins incorporated into
the
protective layer for the purpose of increasing abrasion resistance and water
resistance are
proprietary resins supplied by Rohm and Haas Company, 100 Independence Mall
West,
Philadelphia, PA 19106-2399. The first of these, PARALOID~ A-21, is extremely
hard,
methyl methacrylate polymer with a molecular weight (Mw) of 120,000,
solubility
parameter of 9.4, and a Tg of 105° C. The second, PARALOID B-44, is a
methyl
methacrylate/ethyl acrylate copolymer adhesive resin with a molecular weight
(Mw) of
140,000, solubility parameter of 9.8, and a Tg of 60° C.
To form protective layer 22 or 42, a lacquer composition comprising one or
more
suitable acrylic resins dissolved in one or more suitable volatile organic
solvents is
deposited onto a desired area of polyethylene layer 18 or skim coat 20 or a
hard surface,
preferably applied by gravure printing or a similar technique. After
deposition of the
lacquer composition, the volatile solvents) evaporate(s), leaving only the non-
volatile resin
components thereof to make up protective layer 22 or 42.
A number of organic solvents well known to those in the art can be used.
However,
the solvents isopropanol (isopropyl alcohol, C.A.S. #67-63-0) and methyl ethyl
ketone
(C.A.S. #78-93-3) are preferably used in these formulations according to the
invention.
The protective layer lacquer composition comprises a total of from 5 to 40 %
by
weight, based upon the total weight of the composition, of one or more acrylic
resins, and a
total of from 60 to 90 % by weight of one or more organic solvents, water, an
aqueous
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solution, or a mixture of two or more thereof. Small amounts of surfactants,
dispersants, or
other conventional components may be present as well. The protective layer
resulting after
evaporation will comprises a total of from about 50 to 100 % by weight, based
upon the
total weight of the layer, of one or more acrylic resins.
Ink design layer 24 of transfer portion 14 preferably comprises one or more
acrylic
inks. Ink design layer 24 is formed in the conventional manner by depositing,
by gravure
printing or the like, an ink composition comprising an acrylic resin of the
type described
above, a suitable pigment or dye and one or more suitable volatile organic
solvents onto one
or more desired areas of lacquer layer 22. After application of the ink
composition onto
lacquer layer 22, the volatile organic solvent components) of the ink solvent
system
evaporate(s), leaving only the non-volatile ink components to form layer 24. A
preferred
example of a suitable resin for use in forming an acrylic ink is CARBOSET 526.
A number of known pigments are compatible in inks formulated using the above
described acrylic resin solutions. Representative examples of such pigments
include, but
are not limited to Raven 1040 carbonblack, (CI pigment black 7) supplied by
Columbian
Chemicals Company, 1600 Parkwood Circle, Atlanta, GA 30339; Kronos 2020
Titanium
dioxide (C.I. pigment white 6) supplied by Kronos Inc., 6825 Northchase Drive,
Houston,
Texas 77060; Heliogen Blue D7072DD (C.I. pigment blue 15:3) supplied by BASF
Colorants, P.O. Box 75908M, Charlotte, NC 28275; and 13-3151 permanent carmine
FBB-
02 (C.I. pigment red 146) supplied by Clariant Corporation, 500 Washington
Street,
Coventry, RI 02816.
As a means of improving dispersing of pigments in solutions of these resins,
the
addition of 0.25% of Disperse AYD-1 has proven to be effective. This is a
proprietary
blend of seventy-five percent by weight of a modified alkyd dispersion in
mineral spirits
(C.A.S. #64742-88-7) and is manufactured by Elementis Specialties, 400
Claremont
Avenue, Jersey City, NJ 07304. BYK 346 is a proprietary silicone surfactant
manufactured by BYK-Chemie USA, 524 South Cherry Street, Wallingford, CT
06492.
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FLUORAD FC-430 is a proprietary fluorosurfactant manufactured by the 3M
Speciality
Chemicals Division of 3M Co. of St. Paul, MN 55144-1000.
The ink design layer composition comprises a total of from 5 to 50 % by
weight,
based upon the total weight of the composition of one or more acrylic resins,
and a total of
from 60 to 90 % by weight of one or more organic solvents, water, an aqueous
solution, or
a mixture of two or more thereof. Small amounts of surfactants, dispersants,
or other
conventional components may be present as well. The ink layer resulting after
evaporation
will comprise a total of from about 50 to 100 % by weight, based upon the
total weight of
the layer, of one or more acrylic resins.
Adhesive layer 26 of transfer portion 14 comprises an acrylic adhesive of the
type
present in a solvent-based or water-based adhesive solution or a water-based
adhesive
dispersion of a suitable acrylic resin, such as one or more of the acrylic
resins described
herein. Adhesive layer 26 is formed by depositing onto ink layer 24, by
gravure printing or
the like, an adhesive composition comprising an acrylic adhesive solution or
dispersion and,
preferably, a surface tension lowering agent. After application of the
adhesive composition
onto ink layer 24, the volatile components of the composition (e.g., water,
organic solvent)
evaporate, leaving only the non-volatile solid components thereof to form
layer 26.
The adhesive layer composition comprises a total of from 15 to 45 % by weight,
based upon the total weight of the composition of one or more acrylic resins,
and a total of
from 60 to 85 % by weight of one or more organic solvents, water, an aqueous
solution, or
a mixture of two or more thereof. Small amounts of surfactants, dispersants,
or other
conventional components may be present as well. The adhesive layer resulting
after
evaporation will comprise a total of from about 70 to 100 % by weight, based
upon the total
weight of the layer, of one or more of the acrylic resins.
The labels prepared according to the invention are particularly well-suited
for, but
not limited to, use on silane-treated glass containers of the type that are
subjected to
pasteurization conditions. It is to be understood that, for purposes of the
present
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specification and claims, the expression "silane-treated glass containers"
refers both to
silane-treated glass containers" refers both to silane-treated glass
containers that have been
pre-treated with an abrasion resistant material, such as polyethylene, olecic
acid, stearate or
the like, and to silane-treated glass containers that have not been so pre-
treated.
As a means of more completely removing the multilayer label composition in a
shorter time during immersion of the labeled substrate in the heated aqueous
alkaline
solution, about five to twenty five percent by weight of the solid acrylic
resin material may
be replaced with a hot water soluble material such as 3,3,7,7 - tetra-
hydroxymethyl -5-
oxanonane that is a solid material melting at 106° to 111 °C,
having two percent solubility
in water at 20°C, and fifty percent solubility in water at 65°C.
This product, di-trimethylol
propane, is supplied by Perstorp Polyols, Inc. 600 Matzinger Rd., Toledo, Ohio
43612.
The following are illustrative examples of compositions that may be used to
form
layers of the heat-activatable labelling system useful according to the
invention. It should
be understood that other acrylic resins and compositions of the general type
described
above may also be used to form layers and that the examples given below are in
no way
intended to be limiting:
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EXAMPLES
EXAMPLE 1. Composition for Grinding Vehicles for Inks % BY WEIGHT
ISOPROPANOL 40
METHYL ETHYL KETONE 20
CARBOSET 526 24
JONCRYL 67 16
100
EXAMPLE 2. Adhesive Layer Composition % BY WEIGHT
METHYL ETHYL KETONE 72
CARBOSET 526
_28
100
EXAMPLE 3. Adhesive Layer Composition % BY WEIGHT
METHYL ETHYL KETONE 72
BELLAND GBC-8304 _28
100
EXAMPLE 4. Composition for Abrasive Resistant % BY WEIGHT
Protection Layer
70.0
METHYL ETHYL KETONE 7.5
PARALOID B-44 7.5
PARALOID A-21
15.0
CARBOSET 526 100.0
In Examples 1, 2, 3, and 4, the dry resin or resins are added to the organic
solvent component under agitation. The mixture is mixed until the resin or
resins dissolve in the organic solvent.
EXAMPLE 5. Composition for Single Pigment Black Ink Layer % BY WEIGHT
43.95
ISOPROPANOL
22.60
METHYL ETHYL ICETONE 15.12
CARBOSET 526
10.08
JONCRYL 67 0.25
DISPERSE AYD #1
8.00
RAVEN 1040
100.00
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EXAMPLE 6. Multi Agent Ink Composition % BY WEIGHT
ISOPROPANOL 43.95
METHYL ETHYL KETONE 22.60
CARBOSET 526 15.12
JONCRYL 67 10.08
DISPERSE AYD #1 0.25
PERMANENT CARMINE FBB-02 7.00
HELIOGEN BLUR D7072DD 1.00
100.00
EXAMPLE 7. Composition for Single Pigment White Ink % BY WEIGHT
ISOPROPANOL 26.0
METHYL ETHYL KETONE 14.0
CARBOSET 526 14.4
JONCRYL 67 9.6
DISPERSE AYD #1 1.0
KRONOS 2020 35.0
In Examples 5, 6, and 7, the dry resins are added to the
organic solvent component under agitation, and the mixture is
mixed until the resins dissolve. Under continued mixing of the
solution formed the dispersing agent and the pigment or
pigments are added, so that the pigment or pigments are well
dispersed.
100.0
EXAMPLE 8. Composition for Adhesive or Protective Layer % BY WEIGHT
WATER 83.4
26% AQUEOUS AMMONIA 6.0
BYK 346 0.5
FLUORAD FC-430 0.1
CARBOSET 526 10.0
100.0
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EXAMPLE 9. Composition for Adhesive or Protective Layer % BY WEIGHT
WATER 62.4
26% AQUEOUS AMMONIA
7.0
ISOPROPANOL 10.0
BYK 346
0.5
FLUORAD FC-430 0.1
JONCRYL 67
15.0
CARBOSET 526 5.0
100.0
In Examples 8 and 9, the aqueous ammonia is
added to the water. Then,
under agitation, the additional components
are slowly added. Mixing
continues until the additional components
dissolve.
EXAMPLE 10. Adhesive Layer Composition % BY WEIGHT
ISOPROPANOL
JONCRYL 67 72
DI-TRIMETHYLOLPROPANE 23.8
4.2
100.0
In Example 10, the dry materials, JONCRYL
67 and di-
trimethylolpropane, are added to the organic
solvent, isopropanol, under
agitation. The mixture is mixed until the
solid materials dissolve.
The preceding specific embodiments are illustrative of the practice of the
invention.
It is to be understood, however, that other expedients known to those skilled
in the art or
disclosed herein, may be employed without departing from the spirit of the
invention or the
scope of the appended claims.
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