U.S. patent application number 15/908092 was filed with the patent office on 2018-07-05 for solventless laminating adhesive for flexible packaging laminations and laminated structures made with the adhesive.
The applicant listed for this patent is ASHLAND LICENSING AND INTELLECTUAL PROPERTY LLC. Invention is credited to Randy A. Johnson.
Application Number | 20180186130 15/908092 |
Document ID | / |
Family ID | 45352830 |
Filed Date | 2018-07-05 |
United States Patent
Application |
20180186130 |
Kind Code |
A1 |
Johnson; Randy A. |
July 5, 2018 |
SOLVENTLESS LAMINATING ADHESIVE FOR FLEXIBLE PACKAGING LAMINATIONS
AND LAMINATED STRUCTURES MADE WITH THE ADHESIVE
Abstract
Two-component solventless adhesive compositions for lamination
applications and laminated structures, including flexible laminated
packaging, comprising at least two substrates, including structures
comprising reverse printed ink films and/or metallized films. The
adhesive comprises a prepolymer having one or more oligomers with a
relatively high molecular weight.
Inventors: |
Johnson; Randy A.;
(Hilliard, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASHLAND LICENSING AND INTELLECTUAL PROPERTY LLC |
Dublin |
OH |
US |
|
|
Family ID: |
45352830 |
Appl. No.: |
15/908092 |
Filed: |
February 28, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13172304 |
Jun 29, 2011 |
|
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15908092 |
|
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61359646 |
Jun 29, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G 18/4808 20130101;
B32B 2037/1269 20130101; B32B 2250/04 20130101; Y10T 428/31681
20150401; Y10T 428/31931 20150401; B32B 2250/40 20130101; B32B
2553/00 20130101; B32B 2250/03 20130101; B32B 27/10 20130101; B32B
29/00 20130101; B32B 7/12 20130101; C08G 18/7837 20130101; C09J
175/04 20130101; B32B 15/09 20130101; B32B 27/34 20130101; Y10T
428/31696 20150401; B32B 15/085 20130101; B32B 27/08 20130101; B32B
27/40 20130101; Y10T 428/24917 20150115; Y10T 428/31605 20150401;
B32B 2307/75 20130101; Y10T 428/24802 20150115; B32B 27/36
20130101; Y10T 428/31786 20150401; C08G 18/12 20130101; Y10T
428/31855 20150401; B32B 38/145 20130101; B32B 37/1284 20130101;
B32B 2255/205 20130101; B32B 15/20 20130101; B32B 15/08 20130101;
Y10T 428/31551 20150401; Y10T 428/31678 20150401; B32B 2307/714
20130101; B32B 27/32 20130101; Y10T 428/31725 20150401; Y10T
428/31504 20150401; C08G 18/12 20130101; C08G 18/42 20130101 |
International
Class: |
B32B 27/08 20060101
B32B027/08; B32B 7/12 20060101 B32B007/12; B32B 37/12 20060101
B32B037/12; B32B 15/08 20060101 B32B015/08; B32B 27/36 20060101
B32B027/36; C08G 18/48 20060101 C08G018/48; C08G 18/12 20060101
C08G018/12; B32B 27/40 20060101 B32B027/40; C08G 18/78 20060101
C08G018/78; B32B 27/10 20060101 B32B027/10; B32B 15/20 20060101
B32B015/20; B32B 15/09 20060101 B32B015/09; B32B 29/00 20060101
B32B029/00; B32B 27/34 20060101 B32B027/34 |
Claims
1. A two-component solventless adhesive comprising a prepolymer
having a) a first oligomer with a molecular weight of at least
about 3,500 g/mole; and b) an isocyanate.
2. The adhesive of claim 1 wherein the oligomer is a polyol
selected from the group consisting of polyoxypropylene glycol,
polyoxyethylene glycol, copolymers of ethylene oxide and propylene
oxide and polyester polyols.
3. The adhesive of claim 1 wherein the first oligomer is in an
amount of at least about 20% by weight of the prepolymer.
4. The adhesive of claim 1 wherein the isocyanate is selected from
the group consisting of hexamethylene diisocyanate, toluene
diisocyanate, diphenylmethane diisocyanate, allophonate modified
diphenylmethane diisocyanate, m-phenylene diisocyanate, p-phenylene
diisocyanate, bitolylene diisocyanate, cyclohexane diisocyanate,
bis-(isocyanatomethyl)cyclohexane, dicyclohexylmethane
diisocyanate, dimer acid diisocyanate, trimethyl hexamethylene
diisocyanate, lysine diisocyanate and its methyl ester, isophorone
diisocyanate, methyl cyclohexane diisocyanate, 1,5-napthalene
diisocyanate, xylylene diisocyanate and methyl derivatives thereof,
xylene diisocyanate and methyl derivatives thereof, polymethylene
polyphenyl isocyanates, chlorophenylene-2,4-diisocyanate,
polyphenylene diisocyanates, isophorone diisocyanate, hydrogenated
methylene diphenyl isocyanate, tetramethyl xylene diisocyanate,
hexamethylene diisocyanate, trimer of isophorone diisocyanate,
trimer of hexamethylene diisocyanate, biuret of hexamethylene
diisocyanate and combinations thereof.
5. The adhesive of claim 1 comprising a curative having an
isocyanate reactive component selected from the group consisting of
polyhydroxyls, polythiols, polyamines and combinations thereof.
6. A two-component solventless adhesive comprising a prepolymer
having a) a first oligomer with a molecular weight of about 2,000
g/mole to about 5,000 g/mole a second oligomer having a molecular
weight of about 5,500 g/mole to about 10,000 g/mole; and b) an
isocyanate.
7. A process for making a laminated structure comprising the steps
of a) providing a first substrate and a second substrate each
having an upper surface and a lower surface wherein at least one of
the first substrate or second substrate is selected from the group
consisting of substrate having water-base ink, a substrate having a
metallized film and combinations thereof; b) providing the adhesive
of claim 1 and applying the adhesive to at least one surface of at
least one of the first substrate or second substrate; and c)
bonding the first substrate to the second substrate to form a
laminated structure.
8. The process of claim 7 wherein the adhesive is applied by a
method selected from the group consisting of roll coating, gravure,
and offset gravure.
9. The process of claim 7 wherein the first substrate is a reverse
printed film comprising a water-base adhesive and the second
substrate comprises a metallized film.
10. The process of claim 7 wherein the first substrate comprises a
metallized film and the second substrate is a reverse printed film
comprising a water-base ink.
11. The process of claim 7 wherein at least one of the first
substrate or second substrate is surface treated.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Patent
Application No. 61/359,646, filed Jun. 29, 2010. U.S. Patent
Application No. 61/359,646 is incorporated herein in its entirety
by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention pertains to two-component solventless adhesive
compositions for lamination applications and structures, such as
laminations and flexible laminated packaging, including those
comprising metal or ink decals, comprising and/or made with the
two-component solventless adhesive composition. The two-component
solventless adhesive composition is softer than conventional
two-component solventless adhesive compositions but retains the
beneficial properties of conventional adhesives. The adhesive
composition described herein comprises relatively high molecular
weight oligomers and has an elongation.
The Related Art
[0003] Flexible packaging structures were traditionally made with
solvent-borne laminating adhesives. Over the past 20-30 years, new
water-borne and two-component solventless adhesives have been
developed and commercialized to replace solvent-borne adhesives due
to the benefit of lower costs and a desire in the industry for more
environmentally friendly adhesives. However, some applications
today remain using solvent-borne adhesive technology because of the
specific performance of that technology and the properties of the
substrates being bonded. Thus, two-component solventless laminating
adhesives are not useful for all structures and applications.
[0004] Problematic structures for two-component solventless
adhesives include (1) reverse printed film (i.e., polyethylene
terephthalate ("PET")) to metallized film (i.e., PET) and (2)
reverse printed PET film with water-base inks to secondary films.
Presently these structures are typically made with either
solvent-borne or water-borne laminating adhesives. Metallized film
is generally a plastic film sheet having attached to the film a
layer of metal, generally a thin metal layer. Metallized films are
used in flexible laminated packaging materials where it is desired
to reflect light from the contents of the packaging or for visual
appearance of consumer packaging.
[0005] Typical structures of reverse printed PET laminated to the
metal side of metallized PET with typical two-component solventless
laminating adhesive results in low bonds with up to 100% metal
failure from the metallized PET. Such failure result typically does
not happen when using solvent-borne or water-borne laminating
adhesives. When two-component solventless adhesive is applied with
reverse printed PET with water-base inks, the water-base ink decals
off of the PET at lower bond values.
[0006] Conventional two-component solventless adhesives comprise
relatively lower molecular weight monomers and relatively lower
molecular weight oligomers that typically act as reactive diluents.
These low molecular weight reactive materials generally provide
favorable characteristics and properties for many, but not all,
laminating applications. Without wishing to be bound by any theory,
the inventor believes that in specific applications, such as those
discussed above involving reverse printed film to metallized film
and reverse printed film, including reverse printed PET film, with
water-base inks to secondary films, the relatively lower molecular
weight monomers and relatively lower molecular weight oligomers
contribute to the negative affects of decalling metal
(demetallization) or ink from the film.
[0007] All parts and percentages set forth herein are on a
weight-by-weight basis unless specified otherwise. The molecular
weight referred to herein is the number average molecular weight
(Mn) in grams/mole ("g/mole").
SUMMARY OF THE INVENTION
[0008] The two-component solventless adhesive described herein
improves bond strength in many applications, including in
structures comprising either the metal or ink decals. The
two-component solventless adhesive is softer than conventional
two-component solventless adhesives but maintains many of the same
benefits as conventional two-component solventless adhesives such
as low enough viscosity to apply at 100% solids, good adhesion,
chemical resistance, and the like.
[0009] The two-component solventless adhesive comprises high
molecular weight oligomers, i.e. oligomers having higher molecular
weight than oligomers used in conventional two-component
solventless adhesives. The two-component solventless adhesive is
suited for any lamination application but is particularly suited
for applications where conventional solventless adhesives provide
poorer performance, such as for (1) reverse printed film (i.e.,
PET) to metallized film (i.e., PET) and (2) reverse printed film,
including reverse printed PET film, with water-base inks to
secondary films.
DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates a side, cross-sectional view of a
laminated flexible packaging material in accordance with the
invention.
[0011] FIG. 2 illustrates a side, cross-sectional view of a
laminated flexible packaging material in accordance with the
invention.
[0012] FIG. 3 illustrates a side, cross-sectional view of a
laminated flexible packaging material in accordance with the
invention.
[0013] FIG. 4 is a graph showing bond value in relation to curing
time in days for a reverse printed 48 gauge PET and metallic PET
film laminated structure.
[0014] FIG. 5 is graph showing bond strength for various laminated
structures comprising water-base ink printed films made with
various conventional adhesives.
[0015] FIG. 6 is a graph showing bond strength for various
laminated structures comprising water-base ink printed films made
with control adhesive formulations and adhesive formulations in
accordance with the invention.
[0016] FIG. 7 is a graph showing bond strength for various
laminated structures comprising metallized films made with control
adhesive formulations and adhesive formulations in accordance with
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Two-component solventless adhesives are supplied as two
separate components and mixed prior to application followed by
curing. The two components are called the prepolymer and the
curative. The two-component solventless adhesive has no solvent
and/or is applied without solvent, such as organic solvent or
water.
[0018] The two-component solventless adhesive comprises oligomers
having relatively high molecular weight, such as oligomers having
molecular weight in excess of about 1,000 g/mole, typically
oligomers having molecular weight of at least about 3,000 g/mole
such as about 3,500 g/mole or more, for example oligomers having a
molecular weight of about at least 8,000 g/mole and also those
having molecular weight in excess of about 10,000 g/mole. Included
are oligomers having molecular weight in the range of about 3,500
g/mole to about 20,000 g/mole.
[0019] The two-component solventless adhesive composition may
comprise a combination of relatively high molecular weight
oligomers, having different molecular weights. Thus, the
two-component solventless adhesive may have a first oligomer and,
in embodiments where a combination of oligomers are present, a
second oligomer. For example, the combination of oligomers having a
molecular weight of about 2,000 g/mole to about 5,000 g/mole,
preferably about 3,000 g/mole to about 5,000 g/mole including about
3,500 g/mole to about 5,000 g/mole, and another having a molecular
weight of about 5,000 g/mole to about 10,000 g/mole or more, such
as about 5,500 g/mole to about 10,000 g/mole.
[0020] The two-component solventless adhesive typically has 100%
solids content, although in embodiments the adhesive may have less
than 100% solids content. The molecular weight of the oligomer must
be such that, when combined with other ingredients of the adhesive,
the viscosity is not too high for application without any or a
significant amount of solvent.
[0021] Oligomers useful in the invention include all types of
polyols, for example polypropylene oxide having relatively high
molecular weight. Polyether polyols such as polyoxypropylene
glycol, polyoxyethylene glycol and copolymers of ethylene and
propylene oxide may also be used. Also, polyesterpolyols such as
those compositions obtained from diacids or higher such as, adipic
acid, and various alkane diols are useful. Examples of alkane diols
include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and
1,6-hexanediol. Other useful polyols are obtained by copolymerizing
at least one compound of ethylene oxide, propylene oxide, butylene
oxide, tetrahydrofuran, and the like with at least one compound
having at least two active hydrogen atoms on average in one
molecule such as polyhydric alcohols which include ethylene glycol,
propylene glycol, dipropylene glycol, glycerol and the like. Other
suitable polyhydric compounds include sucrose, ethylenediamine,
propylenediamine, triethanolamine, 1,2-propanedithiol, and the
like.
[0022] Typically, the oligomers are incorporated into the
prepolymer; however, the oligomers can be incorporated into the
curative or in both the curative and prepolymer. Preferably, the
oligomers have relatively low viscosity.
[0023] The oligomers are incorporated in relatively high amounts
and can be incorporated as all or part of the total amount of
oligomer in a two-component solventless adhesive formulation. For
example, when the relatively higher molecular weight oligomers are
incorporated into the prepolymer, the amount of such oligomers may
be at least about 20% by weight of the prepolymer, such as at least
about 40% by weight of the prepolymer and may be as high as at
least about 60% by weight of the prepolymer, including in the
ranges of about 20% by weight to about 80% by weight, such as about
20% by weight to about 60% by weight, such as about 20% by weight
to about 40% by weight, all by weight of the prepolymer.
[0024] The prepolymer may comprise other components typically found
in the prepolymer part of two-component solventless adhesives, such
as isocyanates. Isocyanates useful in the prepolymer of the
invention include hexamethylene diisocyanate, toluene diisocyanate
(TDI), diphenylmethane diisocyanate (MDI) (which is available
commercially as MONDUR.RTM. MR from Bayer Material Science,
Pittsburgh, Pa., USA), allophonate-modified diphenylmethane
diisocyanate (allophonate modified MDI which is commercially
available as MONDUR MA from Bayer Material Science), m- and
p-phenylene diisocyanates, bitolylene diisocyanate, cyclohexane
diisocyanate (CHDI), bis-(isocyanatomethyl)cyclohexane
(H.sub.6XDI), dicyclohexylmethane diisocyanate (H.sub.12MDI), dimer
acid diisocyanate (DDI), trimethyl hexamethylene diisocyanate,
lysine diisocyanate and its methyl ester, isophorone diisocyanate,
methyl cyclohexane diisocyanate, 1,5-napthalene diisocyanate,
xylylene and xylene diisocyanate and methyl derivatives thereof,
polymethylene polyphenyl isocyanates,
chlorophenylene-2,4-diisocyanate, polyphenylene diisocyanates
available commercially as, for example, MONDUR MR or MONDUR MRS
(both available from Bayer Material Science), isophorone
diisocyanate (IPDI), hydrogenated methylene diphenyl isocyanate
(HMDI), tetramethyl xylene diisocyanate (TMXDI), hexamethylene
diisocyanate (HDI), or oligomer materials of these materials such
as a trimer of IPDI, HDI or a biuret of HDI, and the like and
combinations thereof. The preferred isocyanate comprises MDI, such
as MONDUR MA from Bayer Material Science, which is an allophonate
modified MDI. Typically, when the prepolymer part includes both
polyol and isocyanate, the isocyanate content of the prepolymer is
about 5% to about 25%, preferably about 6% to about 17%.
[0025] The prepolymer part of the two-part solventless adhesive
composition typically comprises the relatively high molecular
weight oligomers and isocyanate. For example, in an embodiment the
prepolymer comprises isocyanate and oligomers having molecular
weight in excess of about 1,000 g/mole, typically oligomers having
molecular weight of at least about 3,000 g/mole such as about 3,500
g/mole or more, for example oligomers having a molecular weight of
about at least 8,000 g/mole and also those having a molecular
weight in excess of about 10,000 g/mole. Included are oligomers
having a molecular weight in the range of about 3,500 g/mole to
about 20,000 g/mole. In a further embodiment, the prepolymer
comprises a combination of relatively high molecular weight
oligomers, having different molecular weights, for example a
composition having a molecular weight of about 2,000 g/mole to
about 5,000 g/mole, preferably from about 3,000 g/mole to about
5,000 g/mole including about 3,500 g/mole to about 5,000 g/mole and
another having a molecular weight of about 5,000 g/mole to about
10,000 g/mole or more, such as about 5,500 g/mole to about 10,000
g/mole. The prepolymer may consist essentially of or consist of
these components and combinations.
[0026] In addition, the relatively high molecular weight oligomers
can be used in epoxy/amine solventless two-component adhesives.
[0027] The curative part of the two-component solventless adhesive
may be any curative typically used in two-part adhesives and is
typically an isocyanate reactive curative. The curative part
comprises an isocyanate reactive component, such as a component
selected from the group consisting of polyhydroxyls, polythiols,
polyamines, and the like, and combinations thereof. The curative
part may also comprise isocyanates and/or oligomers, including
those mentioned above with respect to the prepolymer. PURELAM.RTM.
laminating adhesives available from Ashland Inc., Dublin, Ohio,
USA, like PURELAM 6050, may comprise the isocyanate reactive
curative.
[0028] In addition to the above, other components may be included
in the two-component solventless adhesive, in the prepolymer, the
curative or both the prepolymer and curative. These components
include polymerization control agents, inhibitors, antioxidants,
wetting agents, adhesion promoters, fillers and the like.
Polymerization control agents include dibutyl tindilaurate and
trimethyl amine. Fillers include finely divided silicon dioxide,
bentonites or calcium carbonate.
[0029] The prepolymer is generally made by reacting an excess
amount of isocyanate with an isocyanate reactive material, such as
a polyether polyol, which results in the oligomers described herein
and excess isocyanate. Other components of the prepolymer may be
added prior to or after the reaction. The curative may be made by
reacting a diacid (or higher order acid) with a glycol or a
commercially available isocyanate reactive product may be used for
the curative in the two-component solventless adhesive.
[0030] The two-component solventless adhesive is applied with any
type of substrates to create a laminated structure, and laminated
structures made with or comprising the two-component solventless
adhesive are within the scope of the invention, such as flexible
laminated packaging materials. The adhesive is compatible with any
substrates.
[0031] Metallized films are useful with the two-component
solventless adhesive. The metallized films comprise a plastic sheet
and a layer of metal generally deposited on the plastic sheet. The
metallized film is usually formed prior to the process for making
the laminated structures described herein. The plastic material of
the metallized film may be selected from the group consisting of
PET, biaxially oriented polypropylene ("BOPP"), polylactic acid and
polyethylene. The metal layer may be aluminum. Commercially
available metallized films that may be used in the invention
include 48 gauge metallized polyester film (BARRIER-MET.RTM.
Polyester) from VACUMET.RTM., Austell, Ga., U.S.A. and metallized
oriented polypropylene ("OPP") films (METTALYTE.TM. OPP) from
ExxonMobil Chemicals, Houston, Tex., U.S.A., such as 70 gauge
metallic OPP from ExxonMobil.
[0032] The two-component solventless adhesive inhibits, and in
cases prevents, decaling (or demetallizing) of the metal layer from
the plastic sheet of the metallized film in laminated structures
wherein the metallized film is laminated to one or more other
substrates with the two-component solventless adhesive. Also, the
two-component solventless adhesive inhibits, and in cases prevents,
decaling of water-base ink from substrates in laminated structures
wherein at least one substrate comprising water-base ink is
laminated to one or more other substrates, including metallized
substrates, with the two-component solventless adhesive. Decaling
or demetallizing can occur when the laminated structure is torn, in
that the metal layer will be removed from the plastic sheet and
remain attached to the other substrate in the laminated structure
or the water-base ink will remove from the printed substrate. This
is undesirable, particularly with respect to flexible laminated
packaging materials for consumer products.
[0033] The laminated flexible packaging materials may be formed by
conventional means understood to those skilled in the art. The
laminated flexible packaging materials described herein can be
produced using conventional techniques and replacing conventional
laminating adhesives with the two-part solventless adhesive
described herein. Generally, the process for making the laminated
structures comprises the steps of providing at least two
substrates, each having an upper surface and a lower surface,
providing the two-component solventless adhesive described herein,
applying the adhesive to a surface of at least one of the
substrates and bonding the substrates together. Preferably, at
least one of the two substrates is either printed with a water-base
ink or comprises a metallized film substrate, and processes wherein
one of the substrates comprises a water-base ink and the other
comprises a metallized film substrate are within the scope of the
invention. Typical methods of applying adhesive include use of web
coating methods such as roll coating, gravure, offset gravure, and
the like. The adhesive may be applied and cured in-line with the
printing or off-line in a separate laminating step as desired.
[0034] When the prepolymer and curative are mixed, the adhesive
begins to cure and continues to cure over a period of time until
the adhesive cures. During curing, the oligomers in the prepolymer
and the isocyanate reactive component of the curative react. The
laminated structures described herein comprise a cured adhesive
layer, which adhesive in the uncured state is the two-component
solventless adhesive described herein.
[0035] The laminated structures, such as the flexible laminated
packaging, comprise at least two substrates, such as layers of
flexible material, bonded together having at least one layer of the
adhesive, a cured adhesive layer which is a cured form of the
solventless two-part adhesive, between each substrate thereby
forming a laminated construction. Laminated structures, such as
flexible laminated packaging materials, are illustrated in FIGS.
1-3. As shown in FIGS. 1-3, the structures, i.e. laminated flexible
packaging material, 1, 2 and 3 comprise at least one second
substrate, such as a second layer of flexible material, 4 laminated
to a first substrate, such as a first layer of flexible material, 6
by the solventless two-part laminating adhesive described herein 5,
where layer 6 is the layer that will be on the inside of the
finished construction, i.e. package. The adhesive layer 5 may be a
cured adhesive layer of the two-component solventless adhesive
described herein. FIGS. 1-3 illustrate the laminated structures 1,
2 and 3 with two substrates, however, laminated flexible packaging
materials, as well as other laminated structures made with the
solventless two-component laminating adhesive described herein,
comprising more than two substrates, are within the scope of the
invention, such as 3, 4, 5, 6, 7 and 8, or more, substrates.
[0036] Examples of suitable materials for the at least one second
substrate 4 and first substrate 6 independently include, but are
not limited to: paper, aluminum foil, metallized films, coated
films, printed films, co-extruded films, polyester films,
polyolefin based films, white polyolefin based films, polyamide
based films, copolymer films, and films containing various polymer
blends. Typically, the two-part solventless laminating adhesive is
used in flexible laminating packaging wherein one of the substrates
is a reverse printed film, such as a reverse printed film
comprising water-base inks, and the other substrate is a metallized
film. In embodiments, the laminated construction, for example
flexible laminated packaging comprises reverse printed film (such
as PET) laminated with metallized film (such as metallized PET
film) or the combination of reverse printed PET film, such as those
printed with water-base inks, laminated to one or more secondary
films of any of the types described herein. Also, one or more of
the films may comprise linear low density polyethylene.
[0037] FIG. 2 shows an example of a laminated flexible packaging
material 2 comprising reverse printed film. The structure shown in
FIG. 2 comprises a substrate 6, such as a clear layer, which has
been reverse printed 7 on the inside surface thereof, for example a
reverse printed PET film, and then bonded to a second substrate 4,
for example a metallized film layer or other secondary film, using
the solventless two-part adhesive composition 5. In this type
package, the printed material would be readable on the inside
surface of the package.
[0038] FIG. 3 shows a further example of a laminated flexible
packaging material 3 comprising reverse printed film. The structure
shown in FIG. 3 comprises a substrate 4, such as a clear layer,
which has been reverse printed 7 on inside surface thereof, for
example a reverse printed PET film, and then bonded to a substrate
6, for example a metallized film layer or other film like linear
low density polyethylene using the solventless two-part adhesive
composition 5. In this type of package, the printed material would
be readable on the outside of the package.
[0039] In an embodiment, such as when using low surface energy
substrates, such as polyolefins, the surface of the substrate to be
bonded may be surface-treated to enhance adhesion. Surface treating
is well known and any conventional surface treating method can be
used as desired for the particular application. Examples of
suitable surface treating methods include corona treatments,
chemical treatments, plasma treatments and flame treatments.
[0040] The two-component solventless adhesive comprising the
relatively high molecular weight oligomers reduces or eliminates
metal decal or ink decal when using the two-component solventless
laminating adhesives on substrates or inks that traditionally
exhibit decal when conventional two-component solventless adhesives
are applied. Examples include laminations of reverse printed PET
film/solventless adhesive/metallized PET film and reverse
water-base ink printed PET/solventless adhesives/sealant film
(i.e., linear low density polyethylene). For example, replacing
conventional polyols of relative low molecular weights in a
two-part solventless adhesive formulation with polyols having a
molecular weight of about 8,000 g/mole provided significant
improvement causing the failure mode to go from low bonds with 100%
metal decal to bonds greater than 400 gli with adhesive failure on
reverse printed PET adhesively bonded to metallized PET.
EXAMPLES
Comparative Example A
[0041] A reverse printed PET film was bonded with a standard
solventless laminating adhesive (PURELAM.RTM. 6000
(prepolymer)/6050 (curative), available from Ashland Inc.) to the
metal side of metallized PET film. The bond strength of the
laminated structures was tested using ASTM standard D1876-08 which
is incorporated herein by reference in its entirety and the results
are shown graphically in FIG. 4. Initial bond development is
normal, but as the adhesive fully cures the failure mechanism
changes from cohesive adhesive failure to demetalization with low
bond strengths.
Comparative Example B
[0042] Reverse printed PET with standard water-base acrylic inks
were bonded to second substrates with three conventional laminating
adhesives as noted in FIG. 5. The adhesive applied to make the
laminations for this comparative example are PURELAM 6000
(prepolymer)/6050 (curative), PURELAM 8810 (prepolymer)/8253
(curative) and FASTCURE.TM. 110 (prepolymer)/230 (curative); all
available from Ashland Inc. The substrates for each of the printed
film laminates of FIG. 5 are the following: [0043] A--PET reverse
printed with water-base acrylic ink laminated to PET [0044] B--PET
reverse printed with water-base acrylic ink laminated to
polyethylene [0045] C--biaxially oriented polypropylene ("BOPP")
with water-base acrylic ink laminated to BOPP [0046] D--BOPP with
water-base acrylic ink laminated to polyethylene [0047] E--BOPP
with hybrid ink laminated to BOPP. The bond strength (gil) was
tested for each lamination using ASTM standard D1876-08. The
results are set forth in the graph in FIG. 5. The bond strength was
measured at 14 days of curing time.
Example 1
[0048] A prepolymer (Experimental Prepolymer 1) was made in
accordance with the invention by combining the ingredients set
forth in Table 1. A prepolymer was made for comparative purposes as
a control (Control Prepolymer A) by combining the ingredients set
forth in Table 2 including polypropylene oxide having a molecular
weight of 1,000 g/mole.
TABLE-US-00001 TABLE 1 Experimental Prepolymer 1 Materials Wt %
Polypropylene oxide molecular weight 40 8,000 g/mole Polypropylene
oxide molecular weight 21 3,000 g/mole MONDUR MDI 39
TABLE-US-00002 TABLE 2 Control Prepolymer A Materials Wt %
Polypropylene oxide molecular weight 40 1,000 g/mole MONDUR MDI
60
[0049] Both the Experimental Prepolymer 1 and Control Prepolymer A
were mixed with a PURELAM 6050 isocyanate reactive curative from
Ashland Inc. PURELAM 6050 has a hydroxyl number of 270 and
viscosity 2,000 cps. The mix ratios for both adhesive formulations
were calculated in order to provide about 20% excess isocyanate
(Isocyanate Index=1.2) for each adhesive. The experimental has good
phase stability and comparable viscosity to the control. The
adhesive formulation comprising Experimental Prepolymer 1 and the
adhesive formulation comprising Control Prepolymer A were each
applied in making a reverse printed PET film to metallized PET film
layer structure. Both structures were tested for adhesion in
accordance with standard testing protocols and the results are set
forth in Table 3.
TABLE-US-00003 TABLE 3 Adhesion Results Reverse Printed PET
film/solventless adhesive/metallized PET film layer 1 Day 3 Days 7
Days 14 Days Control Prepolymer/ 1.035 c 0.675 50% MT 0.279 100% MT
0.245 100% MT PURELAM 6050 1.010 c 0.681 50% MT 0.212 100% MT 0.216
100% MT 1.096 c 0.607 50% MT 0.342 100% MT 0.251 100% MT Avg.
(lbs/in) 1.047 0.654 0.278 0.237 Avg. (g/in) 475 297 126 108 EXP
#1/PURELAM 0.000 0.186 c 0.929 c 1.351 fs 6050 0.000 0.221 c 1.023
c 1.116 a 0.000 0.205 c 0.887 c 1.187 a Avg. (lbs/in) 0.000 0.204
0.946 1.218 Avg. (g/in) 0 93 429 552 c--cohesive failure
a--adhesive failure MT--metal transfer fs--film split/failure
[0050] The data set forth in Table 3 demonstrates that the
structure made with the adhesive comprising Experimental Prepolymer
1 provided better adhesion to the structure compared to the
adhesive formulation comprising Control Prepolymer A.
Examples 2-6
[0051] Prepolymers were prepared for Examples 2-6 from the
components set forth in Table 4. Examples 2 and 3 are control
prepolymers not made with high molecular weight oligomers and
Examples 4, 5 and 6 are made with oligomers having molecular weight
of at least 3,000 g/mole. The prepolymers for Examples 2-6 were
prepared by reacting the isocyanate (MONDUR MA 2300 from Bayer
Material Science) with the oligomers.
TABLE-US-00004 TABLE 4 Example 2 Example 3 Example 4 Example 5
Example 6 Adh Adh Adh Adh Adh Prepolymer mass wt % mass wt % mass
wt % mass wt % mass wt % MONDUR MA 2300 78.0 46.8 70.0 44.1 60.0
40.0 47.7 34.4 44.7 32.2 Polypropylene 11.0 6.6 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 glycol molecular weight 1,000 Polypropylene 11.0 6.6
30.0 18.9 0.0 0.0 16.2 11.7 0.0 0.0 glycol molecular weight 2,000
Polypropylene 0.0 0.0 0.0 0.0 40.0 26.7 17.0 12.3 17.0 12.3 glycol
molecular weight 3,000 Polypropylene 0.0 0.0 0.0 0.0 0.0 0.0 19.2
13.9 38.4 27.7 glycol molecular weight 8,000 Total 100.0 60.0 100.0
63.0 100.0 66.7 100.0 72.2 100.0 72.2 Curative mass mass mass mass
mass PURELAM 6050 100 40.0 100 37.0 100 33.3 100 27.8 100 27.8
polyester Adhesive Total 100 100 100 100 100 % NCO 16.6 14.8 12.7
9.6 9.4 Prepolymer OH# Curative 270 270 270 270 270 Mix Ratio 1.7:1
1.7:1 2:1 2.6:1 2.6:1 Isocyanate Index 1.23 1.25 1.26 1.24 1.21
[0052] The prepolymers of Examples 2-6 were used with curative as a
laminating adhesive. The prepolymers were mixed with PURELAM 6050
isocyanate reactive curative from Ashland Inc. Additionally,
commercially available laminating adhesives from Ashland (PURELAM
6000 (prepolymer)/6050 (curative)) and PURELAM 8810
(prepolymer)/8253 (prepolymer)) were run as controls. PURELAM 6050
has a hydroxyl number of 270 and viscosity 2,000 cps. The mix
ratios for all adhesive formulations were calculated in order to
cps. The mix ratios for all adhesive formulations were calculated
in order to provide about 25% excess isocyanate (Isocyanate
Index=1.25) for each adhesive. All of the mixed adhesives had good
phase stability.
[0053] The adhesives of Examples 2-6 and the two Ashland adhesive
controls were used to make laminated structures with water-base
acrylic ink printed substrates and metallic substrates and tested
for bond strength using ASTM standard D1876-08. The results are set
forth in FIGS. 6 and 7. The combination of substrates used in the
laminated structures are as follows:
FIG. 6
[0054] PET printed with water-base acrylic ink and PET [0055] PET
printed with water-base acrylic ink and polyethylene [0056] PET
printed with water-base acrylic ink and metallic PET film [0057]
BOPP with water-base acrylic ink and BOPP [0058] BOPP with
water-base acrylic ink and polyethylene [0059] BOPP water-base
acrylic ink and metallic BOPP film
FIG. 7
[0059] [0060] Reverse Printed PET and metallic PET film [0061] PET
and metallic PET film [0062] PET and metallic polylactic acid
[0063] The water-base ink used for the printed substrates in
Examples 2-6 and the Ashland controls was water-base acrylic,
formula is MWF-4135 blended with 10% MWF-120 Extender, from Wikoff
Color Corp., Fort Mill, S.C., U.S.A. The water-base ink was printed
with 550 LPI 4.3 BCM ceramic anilox. Print receptive films were
corona treated with 1.9 kiloWatts. Line speed for printing was 210
feet per minute on a Nilpeter FA-4, 16 inch web width.
[0064] A pilot lab scale solventless adhesive press was used for
making the film-to-film laminations with the adhesives of Examples
2-6 and the Ashland controls with the substrates discussed above
and shown in the graphs of FIGS. 6 and 7. Primary unwind film with
12'' width is corona treated followed by roll coat with 1-2 lb/ream
of the adhesives of Examples 2-6 and the Ashland controls followed
by nipping to secondary corona treated film that is 12'' wide. Line
speed is 40 feet per minute. For laminations including water-base
printed film, this film is the primary web with the solventless
adhesive coated directly on top of the ink followed by nipping to
secondary web. For laminations including metallized films, this
substrate is the secondary web. The metal side is facing the
solventless adhesive. The laminated film structures are cured at
ambient temperature and the bond strengths were measured at 14 days
after lamination.
* * * * *