U.S. patent application number 17/202680 was filed with the patent office on 2021-07-01 for method for forming a laminate comprising a two-component solventless adhesive composition including an amine-initiated polyl.
The applicant listed for this patent is Dow Global Technologies LLC, Rohm and Haas Company. Invention is credited to Marco Frasconi, Thorsten Schmidt, Daniele Vinci.
Application Number | 20210197523 17/202680 |
Document ID | / |
Family ID | 1000005459683 |
Filed Date | 2021-07-01 |
United States Patent
Application |
20210197523 |
Kind Code |
A1 |
Schmidt; Thorsten ; et
al. |
July 1, 2021 |
METHOD FOR FORMING A LAMINATE COMPRISING A TWO-COMPONENT
SOLVENTLESS ADHESIVE COMPOSITION INCLUDING AN AMINE-INITIATED
POLYL
Abstract
Methods for forming a laminate structure comprising a
two-component solventless polyurethane adhesive compositions are
disclosed. The adhesive composition is formulated such that each
component is applied independently to corresponding substrates
prior to the substrates being brought together to form the laminate
structure. The adhesive compositions are highly-reactive and can
comprise amine-initiated polyols or catalysts providing for fast
curing. The amine-initiated polyols comprise a functionality of
from 2 to 12, a hydroxyl number of from 5 to 1,830, and a viscosity
at 40.degree. C. of from 500 to 20,000 mPa-s. The catalyst can be
bismuth catalysts, zinc catalysts, zirconium catalysts, tin
catalysts, and aluminum catalysts. Still further, a laminate formed
according to the methods is disclosed.
Inventors: |
Schmidt; Thorsten;
(Richterswil, CH) ; Vinci; Daniele; (Luzern,
CH) ; Frasconi; Marco; (Fagnano Olona, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dow Global Technologies LLC
Rohm and Haas Company |
Midland
Collegeville |
MI
PA |
US
US |
|
|
Family ID: |
1000005459683 |
Appl. No.: |
17/202680 |
Filed: |
March 16, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16300561 |
Nov 10, 2018 |
|
|
|
PCT/US2017/029287 |
Apr 25, 2017 |
|
|
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17202680 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 27/12 20130101;
C08G 18/7614 20130101; B32B 29/005 20130101; B32B 15/12 20130101;
C09J 2475/00 20130101; B32B 2307/718 20130101; B32B 27/08 20130101;
B32B 2305/72 20130101; B32B 2250/26 20130101; B32B 2255/10
20130101; B32B 2255/205 20130101; C08G 18/24 20130101; B32B 15/14
20130101; C08G 18/222 20130101; B32B 2307/4023 20130101; B32B 5/022
20130101; B32B 2307/50 20130101; B32B 2037/1269 20130101; B32B
29/02 20130101; B32B 5/26 20130101; C08G 18/4018 20130101; C08G
18/227 20130101; B32B 27/10 20130101; C08G 18/10 20130101; B32B
27/06 20130101; B32B 2250/20 20130101; B32B 2439/70 20130101; B32B
7/12 20130101; B32B 2250/24 20130101; C09J 175/08 20130101; C08G
18/76 20130101; C09J 5/04 20130101; B32B 37/0053 20130101; B32B
2250/02 20130101; B32B 2307/75 20130101; B32B 29/002 20130101; B32B
5/024 20130101; C08G 18/3275 20130101; B32B 15/08 20130101; C08G
18/5021 20130101; C09J 175/04 20130101; C09J 175/12 20130101 |
International
Class: |
B32B 7/12 20060101
B32B007/12; C08G 18/10 20060101 C08G018/10; C09J 5/04 20060101
C09J005/04; B32B 27/08 20060101 B32B027/08; B32B 27/10 20060101
B32B027/10; B32B 27/12 20060101 B32B027/12; C09J 175/04 20060101
C09J175/04; C09J 175/08 20060101 C09J175/08; C08G 18/50 20060101
C08G018/50; C08G 18/76 20060101 C08G018/76; B32B 27/06 20060101
B32B027/06; B32B 5/02 20060101 B32B005/02; B32B 15/12 20060101
B32B015/12; B32B 29/00 20060101 B32B029/00; B32B 29/02 20060101
B32B029/02; B32B 15/08 20060101 B32B015/08; B32B 15/14 20060101
B32B015/14; B32B 5/26 20060101 B32B005/26; C08G 18/40 20060101
C08G018/40; B32B 37/00 20060101 B32B037/00; C08G 18/32 20060101
C08G018/32; C09J 175/12 20060101 C09J175/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 10, 2016 |
IT |
102016000047944 |
Mar 20, 2017 |
CN |
201710165096.0 |
Claims
1. A method for forming a laminate structure, comprising: uniformly
applying an isocyanate component to a first substrate, the
isocyanate component comprising at least one isocyanate; uniformly
applying a polyol component to a second substrate; bringing the
first and second substrates together, thereby mixing and reacting
the isocyanate component and the polyol component to form an
adhesive between the first and second substrates; and curing the
adhesive to bond the first and second substrates, wherein the
adhesive comprises a viscosity greater than 10,000 mPa-s (at
40.degree. C.) within 10 minutes after bringing the first and
second substrates together.
2. The method for forming a laminate structure of claim 1, wherein
the isocyanate component and polyol component are applied to the
first substrate and second substrate, respectively, in a ratio of
isocyanate component to polyol component from 0.5:1 to 1.5:1.
3. The method for forming a laminate structure of claim 1, wherein
the isocyanate component and polyol component are each applied to
the first substrate and second substrate, respectively, at a
coating weight of from 0.25 to 1.5 g/m.sup.2.
4. The method for forming a laminate structure of claim 1, wherein
the adhesive composition comprises a bond strength of at least 0.5
N/15 mm within 60 minutes after bringing the first substrate and
second substrate together.
5. The method for forming a laminate structure of claim 1, wherein
bringing the first substrate and second substrate together
comprises passing the first and second substrates through a nip
roller.
6. The method for forming a laminate structure of claim 1, further
comprising mixing the isocyanate component and polyol component
after bringing the first substrate and second substrate together by
passing the first substrate and second substrate through one or
more rollers.
7. The method for forming a laminate structure of claim 1, wherein
the first substrate and second substrate are each selected from
group consisting of paper, woven and nonwoven fabrics, metal foils,
polymer films, metal-coated polymer films, printed films, and
combinations of two or more thereof.
8. The method for forming a laminate structure of claim 1, further
comprising heating the isocyanate component and polyol component to
between from 30 to 80.degree. C. prior to application to the first
substrate and second substrate, respectively.
9. The method for forming a laminate structure of claim 1, wherein
the isocyanate component and polyol component each comprises a
viscosity at 40.degree. C. of from 500 to 10,000 mPa-s.
10. A method for forming a laminate structure, comprising:
uniformly applying an isocyanate component to a first substrate,
the isocyanate component comprising at least one isocyanate;
uniformly applying a polyol component to a second substrate, the
polyol component comprising at least one amine-initiated polyol
comprising primary hydroxyl groups and a backbone incorporating
tertiary amines; bringing the first and second substrates together,
thereby mixing and reacting the isocyanate component and the polyol
component to form an adhesive between the first and second
substrates; and curing the adhesive to bond the first and second
substrates.
11. The method for forming a laminate structure of claim 10,
wherein the adhesive comprises a viscosity greater than 10,000
mPa-s (at 40.degree. C.) within 10 minutes after bringing the first
and second substrates together.
12. The method for forming a laminate structure of claim 10,
wherein the amine-initiated polyol has the structure I:
##STR00002## wherein R.sup.1, R.sup.2, and R.sup.3 are
independently a linear or branched alkyl group.
13. The method for forming a laminate structure of claim 10,
wherein the amine-initiated polyol comprises a functionality of
4.
14. The method for forming a laminate structure of claim 10,
wherein the amine-initiated polyol comprises a hydroxyl number of
37.
15. The method for forming a laminate structure of claim 10,
wherein the amine-initiated polyol comprises a viscosity at
25.degree. C. of about 1,200 mPa-s.
16. The method for forming a laminate structure of claim 10,
wherein the amine-initiated polyol comprises a molecular weight of
about 6,000 g/mol.
17. The method for forming a laminate structure of claim 10,
wherein the isocyanate component and polyol component are applied
to the first substrate and second substrate, respectively, in a
ratio of isocyanate component to polyol component from 0.5:1 to
1.5:1.
18. A method for forming a laminate structure, comprising:
uniformly applying an isocyanate component to a first substrate,
the isocyanate component comprising at least one isocyanate;
uniformly applying a polyol component to a second substrate, the
polyol component comprising at least one catalyst selected from the
group consisting of bismuth catalysts, zinc catalysts, zirconium
catalysts, tin catalysts, and aluminum catalysts; bringing the
first and second substrates together, thereby mixing and reacting
the isocyanate component and the polyol component to form an
adhesive between the first and second substrates; and curing the
adhesive to bond the first and second substrates.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application of
U.S. application Ser. No. 16/300,561, filed on Nov. 10, 2018, which
is a section 371 of PCT/US2017/029287 filed on Apr. 25, 2017, which
claims the benefit of Italy Application No. 102016000047944, filed
on May 10, 2016 and Chinese Application No. 201710165096.0, filed
on March 20, 2017.
FIELD OF THE DISCLOSURE
[0002] The instant disclosure relates to methods for forming a
laminate structure comprising solventless adhesive compositions.
More particularly, the disclosure relates to methods for forming a
laminate comprising a two-component solventless polyurethane
adhesive composition formulated such that each component is
configured to be applied independently to corresponding substrates
prior to the substrates being brought together to form the laminate
structure. The adhesive compositions can comprise amine-initiated
polyols providing for fast curing speeds and improved conversion
efficiency. In some embodiments, the adhesive compositions can
comprise catalysts for increasing the reactivity of the adhesive
composition, such as bismuth catalysts, zinc catalysts, zirconium
catalysts, tin catalysts, and aluminum catalysts.
[0003] In some embodiments, one component of the adhesive
composition is configured to be uniformly applied to a surface of a
first substrate and the other component of the adhesive composition
is configured to be applied to a surface of a second substrate. The
first and second substrates are subsequently brought together,
thereby mixing and reacting the two components to form an adhesive
between the first and second substrates. In this way, the adhesive
can then be cured, thereby bonding the first and second
substrates.
BACKGROUND OF THE DISCLOSURE
[0004] Adhesive compositions are useful for a wide variety of
purposes. For instance, adhesive compositions are used to bond
together substrates such as polyethylene, polypropylene, polyester,
polyamide, metal, paper, or cellophane to form composite films,
i.e., laminates. The use of adhesives in different end-use
applications is generally known. For example, adhesives can be used
in the manufacture of film/film and film/foil laminates used in the
packaging industry, especially for food packaging. Adhesives used
in laminating applications, or "laminating adhesives," can be
generally placed into three categories: solvent-based, water-based,
and solventless. The performance of an adhesive varies by category
and by the application in which the adhesive is applied.
[0005] Solventless laminating adhesives can be applied up to one
hundred percent solids without either organic solvent or an aqueous
carrier. Because no organic solvent or water has to be dried from
the adhesive upon application, these adhesives can be run at high
line speeds and are preferable in applications requiring quick
adhesive application. Solvent and water-based laminating adhesives
are limited by the rate at which the solvent or water can be
effectively dried and removed from the laminate structure after
application of the adhesive. For environmental, health, and safety
reasons, laminating adhesives are preferably aqueous or
solventless.
[0006] Within the category of solventless laminating adhesives,
there are many varieties. One particular variety includes premixed
two-component polyurethane-based laminating adhesives. Typically, a
two-component polyurethane-based laminating adhesive includes a
first component comprising an isocyanate-containing prepolymer
and/or a polyisocyanate and a second component comprising a polyol.
The prepolymer can be obtained by the reaction of excess isocyanate
with a polyether and/or polyester containing two or more hydroxyl
groups per molecule. The second component comprises a polyether
and/or polyester functionalized with two or more hydroxyl groups
per molecule. The two components are combined in a predetermined
ratio, or "premixed," and then applied on a first substrate
("carrier web"). The first substrate is then brought together with
a second substrate to form a laminate structure. The first and
second substrates must be brought together within the pot-life of
the adhesive composition, usually less than thirty minutes.
[0007] Additional layers of substrate can be added to the structure
with additional layers of adhesive composition located between each
successive substrate. The adhesive is then cured, either at room
temperature or elevated temperature, thereby bonding the substrates
together.
[0008] Further processing of the laminate structure depends upon
the curing speed of the adhesive. The curing speed of the adhesive
is indicated by the time in which the mechanical bond between the
laminated substrates takes to become sufficient to allow for
further processing and the laminate is in compliance with
applicable regulations (e.g., food contact regulations). Slow
curing speed results in lower conversion efficiency. Premixed
two-component solventless laminating adhesives, compared to
traditional solvent-containing adhesives, exhibit weak initial
bonds and slow curing speed. The general trend in the converting
industry is towards faster curing laminating adhesives. Faster
curing improves the operational efficiency for converters.
Specifically, quickly moving finished products out of a warehouse
increases production capacity and flexibility for handling last
minute orders (e.g., retailer promotional campaigns). In order to
increase operational efficiency, an adhesive composition with a
reactivity much higher than existing adhesive compositions should
be used to form laminates. However, such an adhesive composition
would provide a challenge for traditional adhesive application
technologies.
[0009] Accordingly, faster and more efficient methods for forming a
laminate comprising two-component solventless polyurethane-based
laminating adhesive compositions are desirable.
SUMMARY OF THE DISCLOSURE
[0010] Methods for forming a laminate structure are disclosed. In
some embodiments, the method includes uniformly applying an
isocyanate component to a first substrate. The isocyanate component
includes at least one polyisocyanate. The method further includes
uniformly applying a polyol component to a second substrate. The
first and second substrates are then brought together, thereby
mixing and reacting the isocyanate component and the polyol
component to form an adhesive between the first and second
substrates. The mixed adhesive composition is then cured, thereby
bonding the first and second substrates. Because of the reactivity
of the constituents of the adhesive composition, the adhesive
composition is capable of achieving a viscosity greater than 10,000
mPa-s within 10 minutes after bringing the first and second
substrates together.
[0011] Laminated structures made according to the disclosed methods
can be slit within as little as two hours after lamination and
delivered within two days to a customer. Laminates made using
existing general purpose adhesive compositions typically require
two to three days from lamination for slitting and five to seven
days for delivery. Accordingly, the process efficiencies are
greatly improved according to the disclosed methods. In addition,
the pot-life of the adhesive compositions used in the disclosed
methods is indefinite compared to a twenty to thirty minute
pot-life for existing general purpose adhesives. This is because
the pot-life of the disclosed adhesive compositions is completely
decoupled from the curing process, as will be discussed below.
[0012] Because the adhesive compositions used in the disclosed
methods are formulated to be more highly reactive than existing
adhesive compositions, they are not ideally suited for use with
existing adhesive application apparatuses. This is because the two
components react very quickly, causing the adhesive to gel and be
unfit for application to a substrate. For this reason, the adhesive
compositions used in the disclosed methods are formulated such that
the isocyanate and polyol components are applied separately on two
different substrates, instead of being premixed and applied on a
carrier web.
[0013] In particular, the adhesive compositions used in the
disclosed methods are formulated such the isocyanate component can
be uniformly applied to a surface of a first substrate and the
polyol component can be uniformly applied to a surface of a second
substrate. The surface of the first substrate is then brought into
contact with the surface of the second substrate to mix and react
the two components, thereby forming a laminate. The adhesive
composition is then cured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Reference is made to the accompanying drawings in which:
[0015] FIG. 1 is a schematic illustration of an application
apparatus for forming a laminate comprising an adhesive
composition; and
[0016] FIG. 2 is a plot illustrating the viscosity of an
Illustrative Example and a Comparative Example versus time.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0017] The two-component solventless adhesive compositions used in
the disclosed methods comprises an isocyanate component and a
polyol component, as stated above.
[0018] Isocyanate Component
[0019] The isocyanate component comprises at least one isocyanate.
The at least one isocyanate can be selected from the group
consisting of an isocyanate prepolymer, an isocyanate monomer, a
polyisocyanate (e.g., dimmers, trimmers, etc.), and combinations of
two or more thereof. As used herein, a "polyisocyanate" is any
compound that contains two or more isocyanate groups. The
isocyanate prepolymer is the reaction product of reactants
comprising at least one isocyanate and at least one polyol. As used
herein, the "isocyanate prepolymer" can be a polyisocyanate
itself.
[0020] The at least one isocyanate comprises a functionality of
from 1.5 to 10, or from 1.8 to 5, or from 2 to 3. As used with
respect to the isocyanate component, "functionality" refers to the
number of hydroxyl reactive sites per molecule. Compounds having
isocyanate groups, such as the isocyanate component, may be
characterized by the parameter "% NCO," which is the amount of
isocyanate groups by weight based on the weight of the compound.
The parameter % NCO is measured by the method of ASTM D 2572-97
(2010). The disclosed isocyanate component has a % NCO of at least
3%, or at least 6%, or at least 10%. Preferably the isocyanate
component has a % NCO not to exceed 25%, or 18%, or 14%.
[0021] Further, the at least one isocyanate comprises a free
monomer content of from 0 to 50%, or from 5 to 40%, or from 10 to
30%. Still further, the at least one isocyanate comprises a
molecular weight of from 200 to 3,000 g/mol, or from 300 to 2,000
g/mol, or from 500 to 1,000 g/mol. Even further, the isocyanate
component has viscosity at 25.degree. C. of from 300 to 40,000
mPa-s, or from 500 to 20,000 mPa-s, or from 1,000 to 10,000 mPa-s,
as measured by the method of ASTM D2196.
[0022] The at least one isocyanate of the isocyanate component can
be selected from the group consisting of an aromatic isocyanate, an
aliphatic isocyanate, a cycloaliphatic isocyanate, and combinations
thereof. An "aromatic polyisocyanate" is an isocyanate that
contains one or more aromatic rings. An "aliphatic polyisocyanate"
contains no aromatic rings. A "cycloaliphatic polyisocyanate" is a
subset of aliphatic polyisocyanates, wherein the chemical chain is
ring-structured.
[0023] Examples of aromatic isocyanates suitable for use according
to the disclosure include, but are not limited to, isomers of
methylene diphenyl diisocyanate ("MDI"), such as 4,4-MDI, 2,2-MDI
and 2,4-MDI, isomers of toluene-diisocyanate ("TDI") such as
2,4-TDI, 2,6-TDI, isomers of naphthalene-diisocyanate ("NDI") such
as 1,5-NDI, isomers of norbornane diisocyanate ("NBDI"), isomers of
tetramethylxylylene diisocyanate ("TMXDI"), and combinations of two
or more thereof. Preferred are isomers of MDI, particularly a
mixture of 4,4-MDI and 2,4-MDI (i.e., liquid MDI) or 4,4-MDI (i.e.,
solid MDI).
[0024] Examples of aliphatic and cycloaliphatic isocyanates
suitable for use according to the disclosure include, but are not
limited to, isomers of hexamethylene diisocyanate ("HDI"), isomers
of isophorone diisocyanate ("IPDI"), isomers of xylene diisocyanate
("XDI"), and combinations thereof.
[0025] The amount of the at least one isocyanate in the adhesive
composition is, by weight based on the weight of the adhesive
composition (i.e., the total weight of the isocyanate component and
the polyol component), at least 5 wt %, or at least 10 wt %, or at
least 20 wt %. The amount of the at least one isocyanate in the
adhesive composition is, by weight based on the weight of the
adhesive composition, not to exceed 100 wt %, or not to exceed 95
wt %, or not to exceed 90 wt %.
[0026] The isocyanate component can further comprise other
constituents commonly known to those of ordinary skill in the art,
e.g., polyols, catalysts, etc.
[0027] Polyol Component
[0028] In some embodiments, the solventless adhesive composition
further comprises a polyol component comprising at least one
highly-reactive amine-initiated polyol. Inclusion of the at least
one amine-initiated polyol in the polyol component provides for
higher reactivity and faster curing than traditional polyols used
in existing two component solventless adhesive compositions. The
amine-initiated polyol comprises primary hydroxyl groups and a
backbone incorporating at least one tertiary amine. In some
embodiments, the polyol component can also comprise another type of
polyol which is a non-amine-initiated polyol. Each polyol type may
include one kind of polyol. Alternatively, each polyol type may
include mixtures of different kinds of polyols. In some
embodiments, one polyol type may be one kind of polyol whereas the
other polyol type may be a mixture of different kinds of
polyols.
[0029] The amine-initiated polyol comprises primary hydroxyl groups
and a backbone incorporating at least one tertiary amine In some
embodiments, the amine-initiated polyol has the chemical structure
of I:
##STR00001##
[0030] wherein R.sup.1, R.sup.2, and R.sup.3 are each independently
a linear or branched alkyl group. For instance, can each
independently be a C.sub.1-C.sub.6 linear or branched alkyl group.
In some embodiments, the amine-initiated polyol comprises tertiary
amines and secondary amines.
[0031] The at least one amine-initiated polyol comprises a
functionality of from 2 to 12, or from 3 to 10, or from 4 to 8. As
used with respect to the polyol component, "functionality" refers
to the number of isocyanate reactive sites per molecule. Further,
the at least one amine-initiated polyol comprises a hydroxyl number
of from 5 to 1,830, or from 20 to 100, or from 31 to 40. As used
with respect to the polyol component, "hydroxyl number" is a
measure of the amount of reactive hydroxyl groups available for
reaction. This number is determined in a wet analytical method and
is reported as the number of milligrams of potassium hydroxide
equivalent to the hydroxyl groups found in one gram of the sample.
The most commonly used methods to determine hydroxyl number are
described in ASTM D 4274 D. Still further, the at least one
amine-initiated polyol comprises a viscosity at 25.degree. C. of
from 500 to 20,000 mPa-s, or from 1,000 to 15,000 mPa-s, or from
1,500 to 10,000 mPa-s.
[0032] Amine-initiated polyols suitable for use according to this
disclosure are made by alkoxylating one or more amine initiators
with one or more alkylene oxides.
[0033] The amount of the at least one amine-initiated polyol in the
adhesive composition is, by weight based on the weight of the
adhesive composition (i.e., the total weight of the isocyanate
component and the polyol component), at least 2 wt %, or at least
10 wt %, or at least 20 wt %. The amount of the at least one
amine-initiated polyol in the adhesive composition is, by weight
based on the weight of the adhesive composition, not to exceed 100
wt %, or not to exceed 95 wt %, or not to exceed 90 wt %.
[0034] In some embodiments, the polyol component comprises a
catalyst for increasing the reactivity of the system. Catalysts
suitable for sufficiently increasing the reactivity of the adhesive
compositions so that they can be used according to the disclosed
methods include, but are not limited to, bismuth catalysts, zinc
catalysts, zirconium catalysts, tin catalysts, and aluminum
catalysts.
[0035] In some embodiments, at least one non-amine-initiated polyol
may optionally be included in the adhesive composition, e.g., in
the polyol component. Examples of the non-amine-initiated polyol
include, but are not limited to, polyester polyols, polyether
polyols, polycarbonate polyols, polyacrylate polyols,
polycaprolactone polyols, polyolefin polyols, natural oil polyols,
and combinations of two or more thereof. Preferably the
non-amine-initiated polyol has viscosity at 25.degree. C. of from
30 to 40,000 mPa-s, or from 50 to 30,000 mPa-s, or from 70 to
20,000 mPa-s, as measured by the method of ASTM D2196. Preferably
the non-amine-initiated polyol has viscosity of 100 to 10,000 mPa-s
at 25.degree. C., as measured by the method of ASTM D2196.
[0036] The amount of the at least one non-amine-initiated polyol in
the adhesive composition is at least 0 wt %, or at least 5 wt %, or
at least 10 wt %. The amount of the at least one
non-amine-initiated polyol in the adhesive composition is not to
exceed 98 wt %, or not to exceed 90 wt %, or not to exceed 80 wt
%.
[0037] The mix ratio of the isocyanate component to the polyol
component, by weight, is controlled by adjusting the coating weight
of each component to its respective substrate. In some embodiments,
the mix ratio of the isocyanate component to the polyol component
in the final adhesive composition can be 100:100, or 100:90, or
100:80. The disclosed adhesive compositions are more forgiving than
traditional adhesives and can accommodate some coating weight error
(e.g., up to about 10% coating weight error).
[0038] In some embodiments, one or more additives can optionally be
included in the adhesive composition. Examples of such additives
include, but are not limited to, tackifiers, plasticizers, rheology
modifiers, adhesion promoters, antioxidants, fillers, colorants,
surfactants, catalysts, solvents, and combinations of two or more
thereof.
[0039] The polyol component can further comprise other constituents
commonly known to those of ordinary skill in the art, e.g.,
additional polyols, catalysts, isocyanates, etc.
[0040] Laminate Formation
[0041] It is contemplated that the isocyanate component and the
polyol component of the solventless adhesive compositions used in
the disclosed methods are formulated separately and stored until it
is desired to form a laminate structure. Preferably, the isocyanate
component and polyol component are in a liquid state at 25.degree.
C. Even if the components are solid at 25.degree. C., it is
acceptable to heat the components as necessary to put them into a
liquid state. As the pot-life of the adhesive composition is
decoupled from the curing process, the components can be stored
indefinitely.
[0042] A laminate formed according to the disclosed methods can be
formed by applying the isocyanate and polyol components of an
adhesive composition separately to two different substrates, such
as two films. As used herein, a "film" is any structure that is 0.5
mm or less in one dimension and is 1 cm or more in both of the
other two dimensions. A "polymer film" is a film that is made of a
polymer or mixture of polymers. The composition of a polymer film
is, typically, 80 percent by weight or more by weight one or more
polymers.
[0043] Turning now to FIG. 1, a schematic view of an apparatus for
carrying out the method is shown, for illustrative purposes. The
apparatus includes a first substrate 102 which is unwindable from a
first unwinder web 104. The first substrate can be a film, as
discussed above. The first substrate 102 passes through an
application unit 106 in which a layer of an isocyanate component of
an adhesive composition is applied to the first substrate 102. The
application unit includes dosing rollers typically operated between
30 and 40.degree. C. The application unit further includes an
application roller typically operated between 30 and 60.degree. C.
The apparatus further includes a second substrate 108 which is
unwindable from a second unwinder web 110. The second substrate 108
can also be a film. The second substrate passes 108 through an
application unit 112 in which a layer of a polyol component of the
adhesive composition is applied to the second substrate 108.
Preferably, the thickness of the first and second layers applied to
the first and second substrates 102, 108, respectively, are from
0.5 to 2.5 .mu.m each. By controlling the thickness of the layers
applied to each substrate, the ratio of the components can be
controlled.
[0044] The surfaces of the first and second substrates 102, 108 are
then run through a device for applying external pressure to the
first and second substrates 102, 108, such as nip roller 114. The
nip roller is typically operated between 30 and 50.degree. C. and
at a pressure between 2 and 4 bar. Bringing the isocyanate
component and polyol component together forms a curable adhesive
mixture layer. When the surfaces of the first and second substrates
102, 108 are brought together, the thickness of the curable
adhesive mixture layer is 1 to 5 .mu.m. The isocyanate component
and polyol component begin mixing and reacting when the first and
second substrates 102, 108 are brought together and the components
come into contact with each other. This marks the beginning of the
curing process.
[0045] Further mixing and reacting is accomplished as the first and
second substrates 102, 108 are run through various other rollers,
e.g., roller 116, and ultimately to a rewind roller 118. The
further mixing and reacting occurs as the first and second
substrates 102, 108 pass through rollers because the substrates
each take longer or shorter paths than the other substrate across
each roller. In this way, the two substrates move relative to one
another, mixing the components on the respective substrates.
Arrangements of rollers in an application apparatus are commonly
known in the art. The curable mixture is then cured or allowed to
cure.
[0046] Suitable substrates in the laminate structure include films
such as paper, woven and nonwoven fabric, metal foil, polymers, and
metal-coated polymers. Films optionally have a surface on which an
image is printed with ink; the ink may be in contact with the
adhesive composition.
[0047] Turning now to FIG. 2, a plot showing the reactivity
profiles of adhesive compositions according to the present
disclosure, i.e., comprising a disclosed amine-initiated polyol,
and that of an adhesive composition without an amine-initiated
polyol are shown. In FIG. 2, an adhesive composition comprising 13
percent by weight of an amine-initiated polyol, based on the weight
of the polyol component, initially comprises a viscosity at
40.degree. C. of approximately 4,000 mPa-s at the time of
lamination. Surprisingly, the viscosity increases rapidly to
greater than 10,000 mPa-s in less than fifteen minutes after
lamination. An adhesive composition comprising 8 percent by weight
of an amine-initiated polyol, based on the weight of the polyol
component, initially comprises a viscosity at 40.degree. C. of
approximately 3,000 mPa-s at the time of lamination.
[0048] Surprisingly, the viscosity increases rapidly to greater
than 10,000 mPa-s in less than twenty minutes after lamination.
Conversely, the adhesive composition without an amine-initiated
polyol initially comprises a viscosity at 40.degree. C. of
approximately 1,000 mPa-s at the time of lamination. The viscosity
does not exceed 10,000 mPa-s until approximately sixty minutes
after lamination. This reactivity profile is typical of existing
solventless adhesive compositions.
EXAMPLES OF THE DISCLOSURE
[0049] The present disclosure will now be explained in further
detail by describing examples illustrating the disclosed adhesive
compositions and existing adhesive compositions (collectively, "the
Examples"). However, the scope of the present disclosure is not, of
course, limited to the Examples.
[0050] In the Examples, the isocyanate component comprises aromatic
isocyanates commonly known to those of ordinary skill in the art,
e.g., TDI MDI. The polyol components of the Examples are prepared
according to the formulations listed in Table 1, below:
TABLE-US-00001 TABLE 1 OH Component Sample Formulations Chemical E1
E2 E3 E4 E5 E6 E7 Component Nature (wt %) (wt %) (wt %) (wt %) (wt
%) (wt %) (wt %) A Polyol 61 73 75 74 B Polyol 55 54 55 C Polyol 15
D Polyol 20 E Polyol 4 2 2 2 F Polyol 8 5 G Amine- 11 20 20 10 10
11 Initiated Polyol H Polyester 8 I Polyester 16 J Polyester 16 K
Polyester 8 8 8 L Aromatic 10 5 10 8 6 10 Isocyanate OH Number 149
226 128 136 128 130 142
[0051] Laminate structures comprising the polyol components
described in Table 1 are prepared on a Nordmeccanica LABO COMBI.TM.
laminator. The prepared laminate structures are then tested for
bond strength and primary aromatic amine decay on the LABO
COMBI.TM. laminator. The bond strength of the laminate structures
is tested according to ASTM F904. The primary aromatic amine decay
analysis is a test for the determination of primary aromatic amines
in aqueous food stimulants (3% acetic acid). The test is based on
the official BrF Method No. L 00-00.6 and Commission Regulation
(EU) No. 10/2011.
[0052] Performance results are shown in Table 2, below. Bond
strength is measured according to ASTM F904 at 2 hours, 4 hours, 1
day, and 2 days after lamination. Primary aromatic amine decay is
tested according to BrF Method No. L 00-00.6 and Commission
Regulation (EU) No. 10/2011 at 24 hours, 2 days, and 3 days after
lamination.
TABLE-US-00002 TABLE 2 Performance Results on LABO COMBI .TM. OH
Bond Strength PAA decay Component Laminate (N/15mm) (.mu.g/100 mL)
Sample Structure 2 hr 4 hr 1 day 2 day 24 h 2 d 3 d E2 PET-ALU/PE
0.5 a 2.1 a PE 4.8 a ALU + 4.8 a ALU 0.6 <0.2 -- coex WL PE E3
PET-ALU/PE 1.6 a 3.5 a PE 2.5 a PE 2.1 a PE 0.4 0.3 -- coex E4
PET-ALU/PE 2.4 a PE 2.5 a PE 2.1 a PE 1.9 a PE 1 0.6 -- E5
PET-ALU/PE 0.7 a 2.6 a PE 3.9 a PE 3.8 a PE <0.2 <0.2 -- coex
E6 PET-ALU/PE <0.2 a 1.6 a PE 3.6 a PE 2.7 a PE <0.2 -- --
coex E7 PET-ALU/PE 0.7 a 2.9 a PE 3.0 a PE 4.1 a PE 0.24 0.34 --
coex E1 PET-ALU/PE 0.9 a 2.3 a PE 5.2 a PE 6.0 a coex 0.24 <0.2
-- coex E1 PET/PE 0.7 a 1.9 a PE 2.9 t PET 5.3 t PET -- 0.23
<0.2 (mix ratio 100/90) coex E1 PET/PE 0.7 a 1.9 a PE 2.4 t PET
4.2 t PET -- 0.26 <0.2 (mix ratio 100/95) coex E1 BOPP ink/metPP
1.4 a 1.6 a 1.6 a 1.7 a -- <0.2 BOPP BOPP BOPP BOPP E1 OPA/PE
2.2 a 5.0 t PE 5.7 t + b PE 6.9 t + b PE -- 0.5 0.5 coex E1 PET/PE
0.7 a 1.9 a PE 2.9 t PET 5.3 t PET -- 0.2 <0.2 (mix ratio
100/90) coex
[0053] In Table 2, "a" indicates that the adhesive remains intact,
and "t" indicates that one of the laminate structures is torn.
Based upon the data in Table 2, inclusion of an amine-initiated
polyol increases the reactivity of the adhesive composition. As
illustrated in Table 3, the formulations comprising the
amine-initiated polyol exhibit faster bond development and faster
PAA decay. In particular, full bond development is achieved in two
days. Full bond development occurs when all functional groups
(e.g., NCO and OH groups) of the at least one isocyanate and
polyols have been reacted and integrated into the final polymer
chain, i.e., no further crosslinking reaction are ongoing and the
final bond performance, thermal and chemical resistance is
achieved. However, a bond sufficient to slit the laminate structure
is achieved within one hour after lamination using the polyol
component comprising the highly-reactive amine-initiated polyol. A
laminate structure has a bond sufficient to slit when it has a bond
strength of at least 1 N/15 min and a tack-free adhesive.
[0054] Laminate structures are also formed on a lamination machine
with two coating heads, as envisioned according to this disclosure.
The prepared laminate structures are then tested for bond strength
and primary aromatic amine decay.
TABLE-US-00003 TABLE 3 Performance Results on Two Coating Head
Laminator OH NCO OH Coating Line Bond Bond Bond Bond Component
Component Component Weight/Sub- Speed (N/15mm) (N/15mm) (N/15mm)
(N/15mm) Sample Substrate Substrate strate (g/m.sup.2) (m/min) @
0.5 hr @ 1 hr @ 1.5 hr @ 2 hr E2 PET-ALU PE 1.8 300 -- -- -- 0.5 E1
PET Metallized 1.8 300 0.13 0.47 1.1 2.0 Unprinted PP E1 Metallized
PET 1.8 150 0.11 0.43 0.94 1.5 PP Unprinted E1 PET-ALU PE 1.75 300
0.15 0.37 1.4 2.1 E1 PE ALU-PET 1.75 300 0.13 0.32 1.1 2.1 E1 BOPP
PE 2 300 0.11 0.27 0.93 1.5 Printed E1 PE BOPP 1.85 150 0.11 0.21
0.61 1.0 Printed
[0055] As indicated in Table 3, adhesive compositions including the
disclosed amine-initiated polyol surprisingly all achieved bond
strengths in excess of 1.0 N/15 min within two hours of laminating.
Many of the Examples even exhibited bond strengths in excess of 2.0
N/15 min within two hours of laminating.
* * * * *