U.S. patent application number 17/582490 was filed with the patent office on 2022-05-12 for wet and dry surface adhesives.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Michael P. Daniels, Shimpei Kudo, Gregg A. Patnode, Shinobu Sato.
Application Number | 20220145139 17/582490 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-12 |
United States Patent
Application |
20220145139 |
Kind Code |
A1 |
Sato; Shinobu ; et
al. |
May 12, 2022 |
Wet and Dry Surface Adhesives
Abstract
A pressure sensitive adhesive comprising the polymerization
product of a polymerizable composition comprising: (a) one or more
(meth)acrylate ester monomers; (b) one or more hydrophilic
non-acidic monomers; and (c) reactive, ionic surfactant. Also
articles comprising such adhesives and methods for making such
adhesives and such articles.
Inventors: |
Sato; Shinobu; (Tokyo,
JP) ; Kudo; Shimpei; (Kanagawa, JP) ; Patnode;
Gregg A.; (Woodbury, MN) ; Daniels; Michael P.;
(Inver Grove Heights, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Appl. No.: |
17/582490 |
Filed: |
January 24, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16319404 |
Jan 21, 2019 |
11261351 |
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PCT/US2017/046113 |
Aug 9, 2017 |
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17582490 |
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62374433 |
Aug 12, 2016 |
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International
Class: |
C09J 7/38 20060101
C09J007/38; C09J 7/35 20060101 C09J007/35; C08F 220/18 20060101
C08F220/18; C08F 220/06 20060101 C08F220/06; C08F 220/28 20060101
C08F220/28; C08F 220/56 20060101 C08F220/56; C08F 2/46 20060101
C08F002/46; C08F 2/38 20060101 C08F002/38; C08K 5/19 20060101
C08K005/19; C08K 5/42 20060101 C08K005/42; C08K 5/14 20060101
C08K005/14 |
Claims
1. A pressure sensitive adhesive comprising the polymerization
product of a polymerizable composition comprising: (a) one or more
(meth)acrylate ester monomers that when polymerized in the absence
of other co-monomers yield a polymer or copolymer having a T.sub.g
of less than about 10.degree. C.; (b) one or more hydrophilic
non-acidic monomers, wherein the one or more (meth)acrylate ester
monomers and the one or more hydrophilic non-acidic monomers are
present in a ratio of about 1:1 to about 1.8:, wherein the
polymerizable composition comprises 30 to 70 to 70 to 90 parts by
weight of a mixture of one or more (meth)acrylate ester monomers
and one or more hydrophilic non-acidic monomers; and (c) about 10
wt % to about 30 wt %, based on the total weight of polymerization
product, of a reactive, ionic surfactant.
2. The adhesive of claim 1 wherein the one or more (meth)acrylate
ester monomers are selected from the group consisting of n-butyl
acrylate, decyl acrylate, 2-ethylhexyl acrylate, hexyl acrylate,
isoamyl acrylate, isodecyl acrylate, isononyl acrylate, isooctyl
acrylate, lauryl acrylate, 2-methyl butyl acrylate,
4-methyl-2-pentyl acrylate, ethoxy ethoxyethyl acrylate, 2-octyl
acrylate, monomers comprising structural isomers of a secondary
alkyl (meth)acrylate, and mixtures thereof.
3. The adhesive of claim 1 wherein the one or more hydrophilic
non-acidic monomers are selected from the group consisting of
N,N-dimethyl acrylamide, N,N-diethyl acrylamide, tert-octyl
acrylamide, N,N-dimethyl methacrylamide, N,N-diethyl
methacrylamide, n-octyl acrylamide, and mixtures thereof.
4. The adhesive of claim 1 wherein the polymerization composition
further comprises one or more hydrophilic acidic comonomers.
5. The adhesive of claim 4 wherein the one or more hydrophilic
acidic comonomers is selected from the group consisting of
ethylenically unsaturated carboxylic acids, ethylenically
unsaturated sulfonic acids, ethylenically unsaturated phosphonic
acids, and mixtures thereof.
6. The adhesive of claim 1 wherein the reactive, ionic surfactant
is selected from the group consisting of ammonium or sodium salts
of sulfate and phosphoric acid.
7. The adhesive of claim 1 wherein the polymerization composition
further comprises one or more initiators selected from the group
consisting of photoinitiators and thermal initiators.
8. The adhesive of claim 7 wherein the one or more initiators is
selected from the group consisting of benzoin ethers, substituted
benzoin ethers, aromatic sulfonyl chlorides, and photoactive
oxides.
9. The adhesive of claim 8 wherein the one or more initiators is
selected from the group consisting of hydroperoxides and
peroxides
10. The adhesive of claim 8 wherein the one or more initiators is
in an amount of about 0.005 to about 1 wt % based on the weight of
the copolymerizable monomers.
11. The adhesive of claim 1 wherein the polymerization composition
further comprises one or more chain transfer agents selected from
the group consisting of halogenated hydrocarbons, sulfur compounds,
and mixtures thereof.
12. The adhesive of claim 11 wherein the polymerization composition
comprises from about 0 part to about 10 parts by weight per 100
parts of total monomer.
13. A hot melt pressure sensitive adhesive comprises a wet-stick
pressure sensitive adhesive having a flow temperature and a
thermoplastic packaging material enveloping said wet-stick pressure
sensitive adhesive, said thermoplastic packaging material having a
melting temperature lower than the flow temperature of the
wet-stick pressure sensitive adhesive, wherein said pressure
sensitive adhesive comprises the polymerization product of a
polymerizable composition comprising: (a) one or more
(meth)acrylate ester monomers that when polymerized in the absence
of other co-monomers, yield a polymer or copolymer having a T.sub.g
of less than about 10.degree. C.; (b) one or more hydrophilic
non-acidic monomers, wherein the one or more (meth)acrylate ester
monomers and the one or more hydrophilic non-acidic monomers are
present in a ratio of about 1:1 to about 1.8:1, and (c) about 10 wt
% to about 30 wt %, based on the total weight of polymerization
product, of a reactive, ionic surfactant.
14. An article a substrate; and a hot melt pressure sensitive
adhesive applied to a surface of said substrate, said hot melt
adhesive comprising a mixture of a pressure sensitive adhesive
having a flow temperature and a thermoplastic material having a
melting temperature that is less than the flow temperature of the
pressure sensitive adhesive, said pressure sensitive adhesive
comprising the polymerization product of a polymerizable
composition comprising: (a) one or more (meth)acrylate ester
monomers that when polymerized in the absence of other co-monomers
yield a polymer or copolymer having a T.sub.g of less than about
10.degree. C.; (b) one or more hydrophilic non-acidic monomers,
wherein the one or more (meth)acrylate ester monomers and the one
or more hydrophilic non-acidic monomers are present in a ratio of
about 1:1 to about 1.8:1, and (c) about 10 wt % to about 30 wt %,
based on the total weight of polymerization product, of a reactive,
ionic surfactant.
15-17. (canceled)
18. The adhesive of claim 1 wherein the polymerizable composition
comprises 25 to 40 wt. % of the one or more hydrophilic non-acidic
monomers.
19. The adhesive of claim 1 wherein the pressure sensitive adhesive
is solventless.
20. The adhesive of claim 1 wherein the adhesive is not an
emulsion.
Description
FIELD OF THE INVENTION
[0001] This invention pertains to pressure-sensitive adhesives, and
more particularly to non-emulsion, solventless acrylate based
pressure-sensitive adhesives incorporating a hydrophilic non-acidic
co-monomer and high loadings of a reactive ionic surfactant within
the polymer backbone. The adhesives exhibit the properties of good
tack and strong adhesion to both wet and dry surfaces.
BACKGROUND OF INVENTION
[0002] Pressure sensitive adhesives that adhere effectively to wet
or moist surfaces, so-called "wet-stick" adhesives, are useful in
selected industrial, commercial, and consumer applications. In
pharmaceutical and other medical fields, wet-stick adhesives are
typically used for adhering articles such as tapes, bandages,
dressings, and drapes to moist skin surfaces such as wounds or
areas of the body prone to moistness. Wet-stick adhesives also find
use in outdoor or exterior applications, such as on pavement
surfaces (e.g., pavement, cement, and concrete pavement), and
marine and automotive coatings and surfaces. Wet-stick adhesives
are also used on labels for food containers and other products that
are exposed to moisture due to condensation or subjected to water
or ice immersion.
[0003] (Meth)acrylate pressure sensitive adhesives are attractive
materials for many tape and label applications. (Meth)acrylates are
known for their optical clarity, oxidative resistance, and
inherently tacky nature. Inherently tacky (meth)acrylate pressure
sensitive adhesives (i.e., materials that require no additives such
as tackifying resins in order to provide desired tack) are
typically formulated predominately from acrylic acid ester monomers
of non-tertiary alcohols. Examples of such monomers include n-butyl
acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl
acrylate, isodecyl acrylate and dodecyl acrylate. For applications
where room temperature tack is desired, (meth)acrylate monomers
which when polymerized yield homopolymers having glass transition
temperatures (T.sub.g) of less than about 0.degree. C. are
typically used. However, such (meth)acrylate polymers are
hydrophobic in nature (i.e., solubility with water is less than 1
wt %) and, without modification, are generally unsuitable for use
as wet-stick adhesives.
[0004] A means to render (meth)acrylate polymers more hydrophilic
is to copolymerize the (meth)acrylate monomers with hydrophilic
acidic comonomers, such as acrylic acid, methacrylic acid,
beta-carboxyethyl acrylate, itaconic acid, sulfoethyl acrylate, and
the like. Addition of these hydrophilic acidic comonomers in minor
amounts (e.g., about 1 to about 15 wt %, typically preferably about
1 to about 10 wt %) can also enhance the internal or cohesive
strength of the resultant PSA. This increased polymer
reinforcement, however, can diminish the resultant copolymer. In
addition, the use of hydrophilic acidic co-monomers can produce
adhesive compositions that will cross-link and exhibit degraded
performance on surfaces that contain metal cations, such as
concrete.
[0005] At higher acidic or non-acidic co-monomer levels,
(meth)acrylate copolymers can dramatically lose their tack and
become highly hydrophilic. When exposed to water, the moisture
helps to transform these highly acidic, low tack compositions into
tacky materials that are suitable as wet-stick adhesives used in
many medical applications. When the water evaporates, these
adhesives lose their pressure-sensitive tack. Such compositions can
also be useful as water-soluble or water dispersible adhesives.
Water-dispersible or soluble (meth)acrylate copolymers can be
formulated as repulpable adhesives used to splice dry paper rolls
and designed to lose adhesive integrity and fully degrade when
undergoing paper recycling operations.
[0006] U.S. Pat. No. 6,855,386 (Daniels et al.) discloses wet-stick
adhesives comprising the reaction product of (meth)acrylate
copolymers, hydrophilic acidic comonomer, and non-reactive,
non-ionic plasticizing agent.
[0007] When producing wet-stick adhesives based on (meth)acrylate
copolymers having high levels of acidic or non-acidic co-monomers,
it is necessary to provide a means to overcome the glassy nature of
the adhesive. While such systems will produce a bond in the
presence of surface moisture, they have the disadvantage of being
relatively low tack systems that take time for the bond to form in
the presence of water. The time required for such adhesives to bond
in the presence of water is of a greater magnitude that the time
required to apply the adhesives. In addition, these systems do not
make strong or quick bonds in the absence of moisture. One means to
address the stiffness of such adhesives is incorporation of a
non-reactive, plasticizer such as described in U.S. Pat. No.
6,855,386 (Daniels et al.). These systems have the disadvantage of
potential plasticizer migration out of the adhesive when immersed
in water. In addition, the incorporation of a non-reactive
plasticizer into the adhesive can dilute the adhesive polymer
entanglements producing adhesives having inherently low shear
strength.
[0008] Another means to address the stiffness associated with high
acidic co-monomer adhesives is incorporation of a reactive agent
that will function as a plasticizer to lower adhesive T.sub.g and
modulus. U.S. Pat. No. 5,397,614 (Patnode et al.) discloses alkali
dispersible pressure sensitive adhesive compositions based on a
terpolymer system containing (meth)acrylate comonomer, beta
carboxyethylacrylate comonomer and ethylene oxide acrylate
comonomer. The ethylene oxide acrylate monomer acts as a
plasticizer that is incorporated into the polymer backbone. The
system is neutralized with metal salt to control level of tack and
dispersibility. These adhesives, however, do not have wet-stick
properties and are only used in systems with hydrophilic acidic
co-monomer.
[0009] U.S. Pat. No. 8,030,395 (Tseng et al.) discloses an emulsion
acrylate pressure sensitive adhesive which utilizes 0.1 to 2 parts
reactive ionic surfactant in a latex binder. The low level of
reactive ionic surfactant is present to provide the ability to
produce an emulsion acrylate adhesive. These adhesives do not have
effective wet-stick properties.
[0010] There exists a need for wet-stick pressure sensitive
adhesives that have good dry and wet adhesion, good tack, and
stability. In addition, there exists a need for wet-stick adhesive
compositions that are free of acid functional, hydrophilic monomers
so as to avoid their becoming chemically cross-linked when adhered
to surfaces that contain metal cations, such as concrete, resulting
in a loss of tack and adhesion.
SUMMARY OF INVENTION
[0011] The present invention provides novel pressure sensitive
adhesive compositions that provide surprising performance, articles
comprising such adhesive formulations, and methods for making such
adhesive formulations.
[0012] The adhesive compositions of the invention comprise the
reaction product of (meth)acrylate comonomers, hydrophilic
non-acidic monomers (e.g., N,N-Dimethylacrylamide (nnDMA) or the
like), and a reactive ionic surfactant of the type used for the
production of emulsion acrylate adhesives. The reactive ionic
surfactant is a compound having a hydrophilic group, a hydrophobic
group, and a radically reactive group in the molecule. Reactive
ionic surfactants useful for the invention include radically
polymerizable, ionic surfactants having poly(alkyleneoxide), and
vinyl functions. Illustrative examples of useful ionic
functionality includes ammonium or sodium salts of sulfate and
phosphoric acid. Some examples of materials for use in the present
invention include HITENOL.TM. KH-10, (Dai-ichi Kogyo Seiyaku Co.,
Ltd., Tokyo, Japan), which is believed to include a
poly(oxy-1,2-ethanediyl),
alpha-sulfo-omega-((1-((2-propenyloxy)methyl)undecyl)oxy)-,
ammonium salt, where n is approximately 10 in the structure shown
below; and HITENOL.TM. HS-10 (Dai-ichi Kogyo Seiyaku Co., Ltd.),
which is believed to include a
poly(oxy-1,2-ethanediyl),a-sulfo-w-[4-nonyl-2-(1-propen-1-yl)phenoxy]-,
branched ammonium salt, where n is approximately 10 in the
structure shown below. These reactive ionic surfactants can have
the following structures:
##STR00001##
[0013] Other examples of useful reactive ionic surfactants include
HITENOL.TM. KH-5 and HITENOL.TM. KH-20, (Dai-ichi Kogyo Seiyaku
Co., Ltd.) which are believed to be similar to HITENOL.TM. KH-10
but with n approximately equal to 5 and 20, respectively, and ADEKA
REASOAP.TM. SR-10 (a reactive anionic ether sulfate surfactant
which is believed to includes ammonium salts of
poly(oxy-1,2-ethanediyl),alpha-sulfo-omega-[1-(hydroxymethyl)-2-(2-propen-
yloxy)ethoxy]-, C.sub.11-rich, C.sub.10-14-branched alkyl ethers),
ADEKA REASOAP.TM. SE-10N (a reactive anionic ether sulfate
surfactant, which is believed to include
.alpha.-Sulfo-.omega.-[1-(nonylphenoxy)methyl]-2-(2-propenyloxy)ethoxy]-p-
oly(oxy-1,2-ethandiyl),ammonium salt), and ADEKA REASOAP.TM. PP-70
(a reactive anionic phosphoric acid ester surfactant) (all from
Adeka Corporation, Tokyo, Japan). These reactive ionic surfactants
can have the following structures:
##STR00002##
and, [0014] PP-70
[0014]
[CH.sub.2.dbd.CHCH.sub.2O(CH.sub.2C(CH.sub.3)HO).sub.m].sub.LP(.d-
bd.O)--(OH).sub.3-L(L: 1 or 2).
[0015] It has been surprisingly discovered that if the
(meth)acrylate co-monomers and hydrophilic non-acidic monomers are
present in a range of ratios (by weight) of from about 1:1 to about
1.8:1, then the presence of reactive ionic surfactant at levels of
at least about 10% (by weight based on total weight of all three
components) in the polymerizable composition provides stable
adhesive compositions with wet and dry adhesion, good tack, and
good performance in the presence of surfaces with metal cations. As
a result, these novel compositions provide heretofore unattained
combinations of performance properties enabling surprising,
heretofore unattained advantages.
[0016] Briefly, in one aspect the present invention is a pressure
sensitive adhesive comprising the polymerization product of a
polymerizable composition comprising, and in some embodiments
consisting essentially of: [0017] (a) one or more (meth)acrylate
ester monomers that when polymerized in the absence of other
co-monomers yield a polymer or copolymer having a T.sub.g of less
than about 10.degree. C.; [0018] (b) one or more hydrophilic
non-acidic monomers, wherein the one or more (meth)acrylate ester
monomers and the one or more hydrophilic non-acidic monomers are
present in a ratio of about 1:1 to about 1.8:1; and [0019] (c)
about 10 wt % to about 30 wt %, based on the total weight of
polymerization product, of a reactive, ionic surfactant. Such
adhesive compositions have been discovered to adhere surprisingly
well to wet substrate surfaces.
[0020] Advantageously, pressure sensitive adhesives of the present
invention are hydrophilic in character, but do not suffer the usual
problems often described in the art of low tack and poor adhesion
to dry surfaces. The novel adhesives of the present invention
provide quick stick, high or acceptably good tack (i.e., an ASTM
D3121 rolling ball tack value of less than 60 mm or of less than
250 mm, respectively), and high or acceptably good adhesion (i.e.,
a 90.degree. peel adhesion to a surface of greater than 10 N/10 cm,
or of greater than 5 N/10 cm, respectively) to both wet and dry
surfaces.
[0021] In another aspect of the present invention, a hot melt
pressure sensitive adhesive is provided wherein the hot melt
pressure sensitive adhesive comprises a wet-stick pressure
sensitive adhesive having a flow temperature and a thermoplastic
packaging material enveloping said wet-stick pressure sensitive
adhesive, the thermoplastic packaging material having a melting
temperature lower than the flow temperature of the wet-stick
pressure sensitive adhesive, wherein the adhesive comprises the
polymerization product of a polymerizable composition comprising,
and in some embodiments consisting essentially of: [0022] (a) one
or more (meth)acrylate ester monomers that when polymerized in the
absence of other co-monomers yield a polymer or copolymer having a
T.sub.g of less than about 10.degree. C.; [0023] (b) one or more
hydrophilic non-acidic monomers, wherein the one or more
(meth)acrylate ester monomers and the one or more hydrophilic
non-acidic monomers are present in a ratio of about 1:1 to about
1.8:1, and [0024] (c) about 10 wt % to about 30 wt %, based on the
total weight of polymerization product, of a reactive, ionic
surfactant.
[0025] In yet another aspect of the present invention, an article
is provided wherein the article comprises a substrate; and a hot
melt pressure sensitive adhesive on at least a portion of a surface
of the substrate, the hot melt adhesive comprising a mixture of a
pressure sensitive adhesive having a flow temperature and a
thermoplastic material having a melting temperature that is less
than the flow temperature of the pressure sensitive adhesive, the
pressure sensitive adhesive comprising the polymerization product
of a polymerizable composition comprising, and in some embodiments
consisting essentially of: [0026] (a) one or more (meth)acrylate
ester monomers that when polymerized in the absence of other
co-monomers yield a polymer or copolymer having a T.sub.g of less
than about 10.degree. C.; [0027] (b) one or more hydrophilic
non-acidic monomers, wherein the one or more (meth)acrylate ester
monomers and the one or more hydrophilic non-acidic monomers are
present in a ratio of about 1:1 to about 1.8:1, and [0028] (c)
about 10 wt % to about 30 wt %, based on the total weight of
polymerization product, of a reactive, ionic surfactant.
[0029] In yet another aspect of the present invention, a method for
preparing a pressure sensitive adhesive comprising the steps of:
[0030] (a) preparing a solventless polymerizable composition
comprising, and in some embodiments consisting essentially of:
[0031] (i) one or more (meth)acrylate ester monomers that when
polymerized in the absence of other co-monomers yield a polymer or
copolymer having a T.sub.g of less than about 10.degree. C.; [0032]
(ii) one or more hydrophilic non-acidic monomers, wherein the one
or more (meth)acrylate ester monomers and the one or more
hydrophilic non-acidic monomers are present in a ratio of 1:1 to
1.8:1, and [0033] (iii) about 10 wt % to about 30 wt %, based on
the total weight of polymerization product, of a reactive, ionic
surfactant. [0034] and [0035] (b) polymerizing the solventless
polymerizable composition to yield the pressure sensitive
adhesive.
[0036] In yet another aspect of the present invention, a method for
preparing a hot melt pressure sensitive adhesive comprising the
steps of: [0037] (a) preparing a solventless polymerizable
composition comprising, and in some embodiments consisting
essentially of: [0038] (i) one or more (meth)acrylate ester
monomers that when polymerized in the absence of other co-monomers
yield a polymer or copolymer having a T.sub.g of less than about
10.degree. C.; [0039] (ii) one or more hydrophilic non-acidic
monomers, wherein the one or more (meth)acrylate ester monomers and
the one or more hydrophilic non-acidic monomers are present in a
ratio of about 1:1 to about 1.8:1, and [0040] (iii) about 10 wt %
to about 30 wt %, based on the total weight of polymerization
product, of a reactive, ionic surfactant; [0041] (b) enveloping the
polymerizable composition in a thermoplastic packaging material;
and [0042] (c) exposing the enveloped polymerizable mixture to
radiation in an amount sufficient to polymerize the polymerizable
mixture and to form the pressure sensitive adhesive that adheres
well to wet and dry substrate surfaces, said pressure sensitive
adhesive having a flow temperature, wherein the thermoplastic
packaging material has a melting temperature lower than the flow
temperature of the pressure sensitive adhesive.
[0043] In yet another aspect of the present invention, a method for
preparing a hot melt pressure sensitive adhesive comprising the
steps of: [0044] (a) preparing a prepolymeric syrup comprising, and
in some embodiments consisting essentially of: [0045] (i) one or
more (meth)acrylate ester monomers that when polymerized in the
absence of other co-monomers yield a polymer or copolymer having a
T.sub.g of less than about 10.degree. C.; [0046] (ii) one or more
hydrophilic non-acidic monomers, wherein the one or more
(meth)acrylate ester monomers and the one or more hydrophilic
non-acidic monomers are present in a ratio of about 1:1 to about
1.8:1; [0047] (iii) optionally about 10 wt % to about 30 wt %,
based on the total weight of such (meth)acrylate ester monomers and
such hydrophilic non-acidic monomers, of a reactive, ionic
surfactant; and [0048] (iv) about 0.04 wt %, based on the total
weight of the polymerization product, of a photoinitiator; [0049]
(b) mixing the prepolymeric syrup until photoinitiator dissolves;
[0050] (c) exposing the prepolymeric syrup to UV-A light having a
spectrum which includes 350 nm, until syrup has sufficient
viscosity deemed appropriate for coating; [0051] (d) adding an
additional 0.1 wt % of at least one photoinitiator, and about 10 wt
% to about 30 wt % (by weight based on total weight of the
surfactant plus (meth)acrylate ester monomers and hydrophilic
non-acidic comonomers, of a reactive, ionic surfactant if it was
not added in step (1) (for instance, to optimize chain transfer
properties), and mixing until the photoinitiator is dissolved and
the composition is well mixed; [0052] (e) coating the resulting
syrup, optionally using a notch bar, between two release liners,
optionally comprising a polyester; and [0053] (f) exposing the
coated syrup, optionally from both sides, to UV-A light having a
spectrum which includes 350 nm, optionally providing an approximate
total energy of at least 1440 milliJoules/square centimeter.
[0054] The adhesives and methods for forming them can be used to
make a variety of useful adhesive articles such as tapes, pavement
markings, labels, patches, etc.
Glossary
[0055] As used herein in this application, the following terms and
acronyms have the indicated meaning.
[0056] "Pressure-sensitive adhesive" or "pressure sensitive
adhesive" or "PSA" refers to a viscoelastic material that possesses
the following properties: (1) aggressive and permanent tack, (2)
adherence with no more than finger pressure, and (3) sufficient
ability to hold onto a substrate.
[0057] "Wet-stick adhesive" refers to a material that exhibits
pressure-sensitive adhesive properties when adhered to a substrate
that has been flooded with water. Wet-stick adhesives generally may
or may not demonstrate pressure-sensitive adhesive properties under
dry conditions. Adhesives of the invention are wet-stick adhesives
and do demonstrate pressure sensitive adhesive properties under dry
conditions.
[0058] "Hot melt adhesive" refers to a material that is heated to
above room or ambient temperature to increase flow or tendency to
wet an adherend, resulting in bond upon cooling to ambient
temperature. Hot melt adhesives may or may not exhibit a degree of
pressure sensitive character.
[0059] "High-tack" refers to adhesive tack value of less than 60 mm
as measured by rolling ball test using ASTM D3121.
[0060] "Good-tack" refers to adhesive tack value of less than 250
mm as measured by rolling ball test using ASTM D3121.
[0061] "High-adhesion" refers to 90.degree. peel adhesion to a
NAKAICHI.TM. Pre Stone Mini Red concrete interlocking block of
greater than 10 N/10 cm width as measured using an Aikoh
Engineering Model RZ-100 Push-Pull gauge.
[0062] "Good-adhesion" refers to 90.degree. peel adhesion to a
NAKAICHI.TM. Pre Stone Mini Red concrete interlocking block of
greater than 5 N/10 cm width as measured using an Aikoh Engineering
Model RZ-100 Push-Pull gauge.
[0063] "(Meth)acrylate monomers" or "(meth)acrylate ester monomers"
are acrylic acid esters or methacrylic acid esters of non-tertiary
alcohols, the alcohols preferably having 4 to 12 carbon atoms, and
any terms beginning with "(meth)acryl" are similarly intended to be
inclusive of "acryl" and "methacryl".
[0064] "Hydrophilic acidic monomers" or "hydrophilic acidic
comonomers" are water soluble ethylenically unsaturated, free
radically reactive monomers having carboxylic, sulfonic or
phosphonic acid functionality and are copolymerizable with the
(meth)acrylate monomers.
[0065] "Reactive ionic surfactant" refers to a compound having a
hydrophilic group with ionic functionality, a hydrophobic group,
and a radically reactive group through which the molecule can be
copolymerized and which may be a vinyl group, and, optionally a
poly alkylene oxide group.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENT(S)
[0066] Generally, a wet-stick pressure-sensitive adhesive of the
present invention comprises the polymerization product of: [0067]
(a) one or more (meth)acrylate ester monomers that when polymerized
in the absence of other co-monomers yield a polymer or copolymer
having a T.sub.g of less than about 10.degree. C.; [0068] (b) one
or more hydrophilic non-acidic monomers, wherein the one or more
(meth)acrylate ester monomers and the one or more hydrophilic
non-acidic monomers are present in a ratio of about 1:1 to about
1.8:1, and [0069] (c) about 10 wt % to about 30 wt %, based on the
total weight of polymerization product, of a reactive, ionic
surfactant.
[0070] (Meth)acrylate Ester Monomers
[0071] The wet-stick adhesives of the present invention contain at
least one monofunctional unsaturated monomer selected from the
group consisting of (meth)acrylate esters of non-tertiary alkyl
alcohols, the alkyl groups of which preferably comprise from 4 to
12, more preferably 4 to 8 carbon atoms; and mixtures thereof.
Preferred (meth)acrylate monomers have the following general
Formula (I):
##STR00003##
wherein R.sup.1 is H or CH.sub.3, the latter corresponding to where
the (meth)acrylate monomer is a methacrylate monomer; R.sup.2 is
broadly selected from linear or branched hydrocarbon groups and may
contain one or more heteroatoms, and the number of carbon atoms in
the hydrocarbon group is preferably 4 to 12, and more preferably 4
to 8.
[0072] Illustrative examples of (meth)acrylate monomers useful in
the present invention include n-butyl acrylate, decyl acrylate,
2-ethylhexyl acrylate, hexyl acrylate, isoamyl acrylate, isodecyl
acrylate, isononyl acrylate, isooctyl acrylate, lauryl acrylate,
2-methyl butyl acrylate, 4-methyl-2-pentyl acrylate, ethoxy
ethoxyethyl acrylate, 2-octyl acrylate. Also suitable are monomers
comprising structural isomers of a secondary alkyl (meth)acrylate
and mixtures thereof, as described in U.S. Pat. 9,102,774 (Clapper
et al.). Particularly preferred are n-butyl acrylate, 2-ethylhexyl
acrylate, isooctyl acrylate, lauryl acrylate, and mixtures
thereof.
[0073] Hydrophilic Non-Acidic Comonomers
[0074] Useful hydrophilic non-acidic comonomers include, but are
not limited to, N,N-dimethyl acrylamide, N,N-diethyl acrylamide,
tert-octyl acrylamide, N,N-dimethyl methacrylamide, N,N-diethyl
methacrylamide, and n-octyl acrylamide.
[0075] Hydrophilic Acidic Comonomers
[0076] Hydrophilic Acidic Comonomers may, optionally, also be used.
Useful hydrophilic acidic co-monomers include, but are not limited
to, those selected from ethylenically unsaturated carboxylic acids,
ethylenically unsaturated sulfonic acids, ethylenically unsaturated
phosphonic acids, and mixtures thereof. Examples of such compounds
include those selected from acrylic acid, methacrylic acid,
itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleic
acid, beta-carboxyethyl acrylate, 2-sulfoethyl methacrylate,
styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid,
vinyl phosphonic acid, and the like, and mixtures thereof. Due to
their availability and effectiveness in reinforcing (meth)acrylate
pressure sensitive adhesives, particularly preferred hydrophilic
acidic monomers are the ethylenically unsaturated carboxylic acids.
Beta-carboxyethyl acrylate can be a preferred hydrophilic acidic
comonomer. Acrylic acid can be a preferred hydrophilic acidic
comonomer when used in combination with one or more other
hydrophilic acidic monomer(s) to meet the other criteria of the
present invention, good wet and dry adhesion plus good tack.
[0077] Minor amounts of monomers copolymerizable with the
(meth)acrylate monomers and hydrophilic acidic monomers can be
used. Examples of such monomers include (meth)acrylamides, vinyl
esters, and N-vinyl lactams.
[0078] Reactive Ionic Surfactants
[0079] Useful ionic functionalities include ammonium or sodium
salts of sulfate and phosphoric acid. Some useful examples include
HITENOL.TM. KH-10, (Dai-ichi Kogyo Seiyaku Co., Ltd.), which is
believed to include a poly(oxy-1,2-ethanediyl),
alpha-sulfo-omega-((1-((2-propenyloxy)methyl)undecyl)oxy)-,
ammonium salt, where n is approximately 10 in the structure shown
below; and HITENOL.TM. HS-10 (Dai-ichi Kogyo Seiyaku Co., Ltd.),
which is believed to include a
poly(oxy-1,2-ethanediyl),a-sulfo-w-[4-nonyl-2-(1-propen-1-yl)phenoxy]-,br-
anched ammonium salt, where n is approximately 10 in the structure
shown below.
[0080] These reactive ionic surfactants can have the following
structures:
##STR00004##
[0081] Other useful reactive ionic surfactants include HITENOL.TM.
KH-5 and HITENOLTM KH-20, (Dai-ichi Kogyo Seiyaku Co., Ltd.) which
are believed to be similar to HITENOL.TM. KH-10 but with n
approximately equal to 5 and 20, respectively, and ADEKA
REASOAP.TM. SR-10 (a reactive anionic ether sulfate surfactant
which is believed to includes ammonium salts of
poly(oxy-1,2-ethanediyl),alpha-sulfo-omega-[1-(hydroxymethyl)-2--
(2-propenyloxy)ethoxy]-, C.sub.11-rich, C.sub.10-14-branched alkyl
ethers), ADEKA REASOAP.TM. SE-10N (a reactive anionic ether sulfate
surfactant, which is believed to include
.alpha.-Sulfo-.omega.-[1-(nonylphenoxy)methyl]-2-(2-propenyloxy)ethoxy]-p-
oly(oxy-1,2-ethandiyl),ammonium salt), and ADEKA REASOAP.TM. PP-70
(a reactive anionic phosphoric acid ester surfactant) (all
available from Adeka Corporation).
[0082] These reactive ionic surfactants can have the following
structures:
##STR00005##
[0083] The copolymerizable mixture of the present invention
comprises, based upon 100 parts by weight total, about 30 to 70 to
about 70 to 90 parts by weight of a mixture of one or more
(meth)acrylate ester monomers and one or more hydrophilic
non-acidic monomers wherein the weight ratio of (meth)acrylate
ester monomers to hydrophilic non-acidic monomers is about 1:1 to
about 1.8:1, and about 10 wt % to about 30 wt %, based on the total
weight, of a reactive, ionic surfactant. The (meth)acrylate ester
monomers, that when polymerized in the absence of other comonomers
yield a polymer or copolymer having a T.sub.g of less than about
10.degree. C.
[0084] The ratio and type of each co-monomer in the wet-stick
adhesive composition can be chosen within the stated limits to
optimize the performance.
[0085] Initiators
[0086] One or more free radical initiators is optionally added to
aid in the copolymerization of (meth)acrylate comonomers and acidic
comonomers.
[0087] As will be understood by those skilled in the art, selection
of useful type of initiator used depends on the polymerization
process. Photoinitiators which are useful for polymerizing the
polymerizable mixture monomers include benzoin ethers such as
benzoin methyl ether or benzoin isopropyl ether, substituted
benzoin ethers such as 2-methyl-2-hydroxypropiophenone, aromatic
sulfonyl chlorides such as 2-naphthalenesulfonyl chloride, and
photoactive oxides such as
1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)oxime. An example of
a commercially available photoinitiator suitable for use in many
embodiments is IRGACURE.TM. 651
(2,2-dimethoxy-1,2-diphenylethane-1-one, from Ciba-Geigy
Corporation). Generally, the photoinitiator is present in an amount
of about 0.005 to about 1 weight percent based on the weight of the
copolymerizable monomers.
[0088] Illustrative examples of suitable thermal initiators include
AIBN (i.e., 2,2'-azobis(isobutyronitrile), hydroperoxides, such as
tert-butyl hydroperoxide, and peroxides, such as benzoyl peroxide
and cyclohexane peroxide.
[0089] Chain Transfer Agents
[0090] Optionally, the composition may also include one or more
chain transfer agents to control the molecular weight of the
polymerized compositions. Chain transfer agents are materials that
regulate free radical polymerization and are generally known in the
art. Suitable chain transfer agents include halogenated
hydrocarbons such as carbon tetrabromide; sulfur compounds such as
lauryl mercaptan, butyl mercaptan, ethanethiol,
isooctylthioglycolate (IOTG), 2-ethylhexyl thioglycolate,
2-ethylhexyl mercaptopropionate, 2-mercaptoimidazole, and
2-mercaptoethyl ether and mixtures thereof.
[0091] The amount of chain transfer agent that is useful depends
upon the desired molecular weight and the type of chain transfer
agent. The chain transfer agent is typically used in amounts from
about 0 part to about 10 parts by weight per 100 parts of total
monomer, and preferably from about 0 part to about 0.5 part.
[0092] Solventless Polymerization Processes
[0093] Solventless polymerization methods, such as the continuous
free radical polymerization method described in U.S. Pat. No.
4,619,979 (Kotnour et al.) and U.S. Pat. No. 4,843,134 (Kotnour et
al.); the essentially adiabatic polymerization methods using a
batch reactor described in U.S. Pat. No. 5,637,646 (Ellis); and,
the methods described for polymerizing packaged polymerizable
mixtures described in U.S. Pat. No. 5,804,610 (Hamer et al.) may
also be utilized to prepare the polymers.
[0094] In one preferred embodiment of this latter method, from
about 0.1 to about 500 g of the polymerizable mixture comprising
the (meth)acrylate monomers, hydrophilic acidic comonomers,
plasticizing agent, initiator, and optional chain transfer agent is
completely surrounded by a packaging material. In another preferred
embodiment, from about 3 to about 100 g of the polymerizable
mixture is surrounded by the packaging material. In another
embodiment of the invention, the polymerizable mixture is
substantially surrounded by the packaging material. In yet another
embodiment, the polymerizable mixture is disposed on the surface of
a sheet, or between a pair of two substantially parallel sheets of
the packaging material. In another embodiment of the invention, the
polymerizable mixture is substantially or completely surrounded by
a hollow profile of packaging material with a length: square root
of the cross-sectional area ratio of at least about 30:1.
[0095] The packaging material is made of a material that when
combined with the adhesive does not substantially adversely affect
the desired adhesive characteristics. A hot melt coated adhesive
produced from a mixture of the adhesive and the packaging material
may have improved adhesive properties compared to hot melt coated
adhesive produced from adhesive alone.
[0096] The packaging material preferably melts at or below the
processing temperature of the adhesive (i.e., the temperature at
which the adhesive flows, or the flow temperature). The packaging
material preferably has a melting point, or melting temperature, of
about 200.degree. C. or less, preferably about 170.degree. C. or
less. In a preferred embodiment the melting point ranges from about
90.degree. C. to about 150.degree. C. The packaging material may be
a flexible thermoplastic polymeric film. The packaging material is
preferably selected from ethylene-vinyl acetate, ethylene-acrylic
acid, polypropylene, polyethylene, polybutadiene, or ionomeric
films. In a preferred embodiment the packaging material is an
ethylene-acrylic acid or ethylene-vinyl acetate film.
[0097] The amount of packaging material depends upon the type of
material and the desired end properties. The amount of packaging
material typically ranges from about 0.5 percent to about 20
percent of the total weight of the polymerization mixture and the
packaging material. Preferably, the packaging material is from
about 2 percent to about 15 percent by weight, and more preferably
from about 3 percent to about 5 percent. Such packaging materials
may contain plasticizers, stabilizers, dyes, perfumes, fillers,
slip agents, antiblock agents, flame retardants, anti-static
agents, microwave receptors, thermally conductive particles,
electrically conductive particles, and/or other materials to
increase the flexibility, handleability, visibility, or other
useful property of the film, as long as they do not adversely
affect the desired properties of the adhesive.
[0098] The packaging material should be appropriate for the
polymerization method used. For example, with photopolymerization,
it is necessary to use a film material that is sufficiently
transparent to ultraviolet radiation at the wavelengths necessary
to effect polymerization.
[0099] The transmissive energy may be selected from ultraviolet
radiation, visible radiation, thermal radiation, or thermal
conduction. The transmissive energy is preferably ultraviolet
radiation or thermal conduction. Preferably, at least about 80
percent of the pre-adhesive is converted to adhesive; more
preferably, at least about 90 percent of the pre-adhesive is
converted to adhesive.
[0100] Thermal polymerization can be effected by immersing the
packaged composition in a heat exchange medium at temperatures from
about 40.degree. C. to about 100.degree. C. for a time sufficient
to polymerize the composition. The heat exchange medium may be a
forced or impinged gas or a liquid such as water, perfluorinated
liquids, glycerin, or propylene glycol. The heat necessary for
thermal polymerization may also be provided by a metal platen,
heated metal rolls, or microwave energy.
[0101] The temperature at which the polymerization occurs depends
upon the activation temperature of the initiator. For example,
polymerization using VAZO.TM. 64, a commercially available
initiator from DuPont Company can be carried out at about
65.degree. C., while VAZO.TM. 52, also from DuPont Company, can be
used at about 45.degree. C.
[0102] It is preferable to carry out the polymerization in an
appropriate liquid heat exchange medium at a controlled
temperature. A suitable liquid heat exchange medium is water,
heated to the desired reaction temperature. Commercially available
heat transfer fluids may also be used. Additional information
concerning thermal polymerization may be found in U.S. Ser. No.
08/234,468, filed Apr. 26, 1994, entitled "Thermal Free-Radical
Cure Adhesives and Articles Made Thereby".
[0103] Polymerization can also be effected by exposure to
ultraviolet (UV) radiation as described in U.S. Pat. No. 4,181,752
(Martens et al.). In a preferred embodiment, the polymerization is
carried out with UV black lights having over 60 percent, and
preferably over 75 percent of their emission spectra from about 280
to about 400 nm, with an intensity from about 0.1 to about 25
mW/cm.sup.2.
[0104] During photopolymerization it is desirable to control the
temperature by blowing cooling air around the packaged
polymerizable mixture, by running the packaged polymerizable
mixture over a cooled platen, or by immersing the packaged
polymerizable mixture in a water bath or a heat transfer fluid
during polymerization. Preferably, the packaged polymerizable
mixtures are immersed in a water bath, with water temperatures from
about 5.degree. C. to 90.degree. C., preferably below about
30.degree. C. Agitation of the water or fluid helps to avoid hot
spots during the reaction.
[0105] The packaged polymerized wet-stick adhesive compositions may
be used to make a coatable hot melt adhesive by introducing the
adhesive and its packaging material into a vessel in which the
adhesive and its packaging material are melted. This hot melt
adhesive may be used to form a pressure sensitive adhesive sheet by
coating the melted adhesive and its packaging material onto a sheet
material or another suitable substrate. The sheet material is
preferably selected from a tape backing or a release liner.
Preferably, the polymerized adhesives are hot melt coated by
putting the packaged adhesive in a hot melt coater at a temperature
sufficient to melt the packaged adhesive and with sufficient mixing
to form a coatable mixture, which is coated onto a substrate. This
step can be done conveniently in a heated extruder, bulk tank
melter, melt-on-demand equipment, or a hand-held hot melt adhesive
gun.
[0106] For any of these embodiments, the coatable hot melt adhesive
can then be delivered out of a film die, subsequently contacting
the drawn adhesive to a moving plastic web or other suitable
substrate. A related coating method involves extruding the coatable
hot melt adhesive and a coextruded backing material from a film die
and cooling the layered product to form an adhesive tape. Other
forming methods involve directly contacting the coatable hot melt
adhesive to a rapidly moving plastic web or other suitable
preformed substrate. Using this method, the adhesive blend is
applied to the moving preformed web using a die having flexible die
lips, such as a rotary rod die. After forming by any of these
continuous methods, the adhesive films or layers can be solidified
by quenching using both direct methods (e.g., chill rolls or water
baths) and indirect methods (e.g., air or gas impingement).
[0107] The packaged adhesive composition may further comprise an
effective amount of a crosslinking agent that may be activated
after the adhesive has been hot melt coated. Typically, the amount
ranges from about 0.01 to about 5.0 parts based upon 100 parts of
the (meth)acrylate monomers and the hydrophilic acidic comonomers.
The crosslinking agent can be added to the polymerized adhesive
before or during hot melt coating, or it can be added to the
polymerizable mixture. When added to the polymerizable mixture, the
crosslinking agent can remain intact as a separate species in the
adhesive, or it can be co-polymerized with the monomers.
Crosslinking is preferably initiated after hot melt coating, and
the crosslinking is preferably initiated by ultraviolet radiation,
or ionizing radiation such as gamma radiation or electron beam (the
use of separate crosslinking agents being optional in the case of
ionizing radiation). Preferred crosslinking agents that can be
added after polymerization and before hot melt coating include
multi-functional (meth)acrylates such as 1,6-hexanedioldiacrylate
and trimethylolpropane triacrylate, and substituted triazines such
as 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-s-triazine and
2,4-bis(trichloromethyl)-6-(3,4-dimethoxyphenyl)-s-triazine, as
described in U.S. Pat. No. 4,329,384 (Vesley et al.) and U.S. Pat.
No. 4,330,590 (Vesley). Another class of preferred crosslinking
agents are the copolymerizable mono-ethylenically unsaturated
aromatic ketone comonomers free of ortho-aromatic hydroxyl groups
such as those disclosed in U.S. Pat. No. 4,737,559 (Kellen et al.).
Specific examples include para-acryloxybenzophenone,
para-acryloxyethoxybenzophenone,
para-N-(methylacryloxyethyl)-carbamoylethoxybenzophenone,
para-acryloxyacetophenone, ortho-acrylamidoacetophenone, acrylated
anthraquinones, and the like.
[0108] Yet another class of suitable crosslinking agents are the
multifunctional radiation-activatable crosslinking agents described
in PCT Patent Application WO 97/07161 (Stark et al.), and in U.S.
Pat. No. 5,407,971 (Everaerts et al.). An example of these
crosslinking agents is 1,5-bis(4-benzoylbenzoxy) pentane. Also
suitable are hydrogen-abstracting carbonyls such as anthraquinone,
benzophenone, and derivatives thereof, as disclosed in U.S. Pat.
No. 4,181,752.
[0109] The acrylate copolymers can be crosslinked by exposure to
ultraviolet radiation from, for example, medium pressure mercury
arc lamps. It is preferred that crosslinking agents activated by
ultraviolet radiation be primarily activated by a different
wavelength of energy than that used for the polymerization. For
example, low intensity black lights may be used for polymerization
and mercury arc lamps may be used for the subsequent
crosslinking.
[0110] The steps may be done in-line, that is, the polymerizable
mixture may be surrounded by the packaging material, polymerized,
hot melt coated to form a tape, and optionally crosslinked, or the
steps may be performed individually at separate times and sites.
For example, the packaged prepolymeric mixture may be polymerized
at one time, and extruded and crosslinked at another time.
[0111] In another preferred bulk polymerization method, the
wet-stick (meth)acrylate pressure sensitive adhesives of the
present invention are prepared by photoinitiated polymerization
methods of the technique described in U.S. Pat. No. 4,181,752. The
(meth)acrylate monomers, hydrophilic acidic comonomers,
plasticizing agent and a photoinitiator are mixed together in the
absence of solvent and partially polymerized to a viscosity in the
range of from about 500 cps to about 50,000 cps to achieve a
coatable syrup. Alternatively, the (meth)acrylate monomers,
hydrophilic acidic comonomers, plasticizing agent may be mixed with
a thixotropic agent such as fumed hydrophilic silica to achieve a
coatable thickness. The crosslinking agent and any other
ingredients are then added to the prepolymeric syrup.
Alternatively, these ingredients (with the exception of the
crosslinking agent) can be added directly to the monomer mixture
prior to pre-polymerization.
[0112] The resulting composition is coated onto a substrate (which
may be transparent to ultraviolet radiation) and polymerized in an
inert (i.e., oxygen free) atmosphere (e.g., a nitrogen atmosphere)
by exposure to ultraviolet radiation. Examples of suitable
substrates include release liners (e.g., silicone release liners)
and tape backings (which may be primed or unprimed paper or
plastic). A sufficiently inert atmosphere can also be achieved by
covering a layer of the polymerizable coating with a plastic film
which is substantially transparent to ultraviolet radiation, and
irradiating through that film in air as described in the
aforementioned patent using ultraviolet lamps. Alternatively,
instead of covering the polymerizable coating, an oxidizable tin
compound may be added to the polymerizable syrup to increase the
tolerance of the syrup to oxygen as described in U.S. Pat. No.
4,303,485. The ultraviolet light source preferably has 90% of the
emissions from about 280 to about 400 nm (more preferably from
about 300 to about 400 nm), with a maximum at about 351 nm.
[0113] The polymerizable mixture may also contain a crosslinking
agent, or a combination of crosslinking agents, to increase the
shear strength of the adhesive. Useful crosslinking agents include
substituted triazines such as
2,4,-bis(trichloromethyl)-6-(4-methoxy phenyl)-s-triazine,
2,4-bis(trichloromethyl)-6-(3,4-dimethoxyphenyl)-s-triazine, and
the chromophore-substituted halo-s-triazines disclosed in U.S. Pat.
Nos. 4,329,384 and 4,330,590. Other useful crosslinking agents
include multifunctional alkyl (meth)acrylate monomers such as
trimetholpropane triacrylate, pentaerythritol tetra-acrylate, 1,2
ethylene glycol diacrylate, 1,4 butanediol diacrylate, 1,6
hexanediol diacrylate, and 1,12 dodecanol diacrylate. Various other
crosslinking agents with different molecular weights between
(meth)acrylate functionality would also be useful. Generally, the
crosslinker is present in an amount of about 0.005 to about 1
weight percent based on the combined weight of the monomers.
[0114] Other Additives
[0115] As will be understood, other additives can be included in
the polymerizable mixture or added at the time of compounding or
coating to change the properties of the adhesive. Such additives,
or fillers, include pigments, glass or polymeric bubbles or beads
(which may be expanded or unexpanded), fibers, reinforcing agents,
hydrophobic or hydrophilic silica, toughening agents, fire
retardants, antioxidants, finely ground polymeric particles such as
polyester, nylon, and polypropylene, and stabilizers. The additives
are added in amounts sufficient to obtain the desired end
properties.
[0116] The wet-stick pressure sensitive adhesives of the present
invention that provide good tack, and good adhesion to both wet and
dry surfaces are useful in many industrial, commercial and consumer
applications. For example these good tack, and good adhesion to
both wet and dry surface adhesives are useful in medical
applications, such as tapes, bandages, dressings, and drapes to
adhere to dry and to moist skin surfaces such as wounds or areas of
the body prone to moistness. Additionally, these good tack, and
good adhesion to both wet and dry surface adhesives also find use
in outdoor or exterior applications, such as on roadway materials,
such as pavement surfaces such as asphalt pavement, and in pavement
marking tapes, traffic control signage, and marine or automotive
coatings and surfaces. Furthermore, labels for food containers and
other products that are exposed to moisture due to condensation or
subjected to water or ice immersion also can be coated with good
tack, and good adhesion to both wet and dry surface adhesives.
EXAMPLES
[0117] This invention is further illustrated by the following
examples that are not intended to limit the scope of the invention.
In the examples, all parts, ratios and percentages are by weight
unless otherwise indicated. The following test methods were used to
evaluate and characterize the wet-stick adhesive compositions
produced in the examples. All materials are commercially available,
for example from Aldrich Chemicals (Milwaukee, Wisconsin), unless
otherwise indicated or described.
[0118] Several abbreviations and units are used in the description
including the following:
TABLE-US-00001 Abbreviation Meaning Hr Hour Kg Kilogram Min Minutes
Ml Milliliter Mm Millimeter mW milliWatt Cm Centimeter N Newton Nm
Nanometer 2EHA 2-ethylhexyl acrylate AA acrylic acid B-CEA
beta-carboxyethyl acrylate DMA N,N-dimethyl acrylamide IOA isooctyl
acrylate IOTG isooctyl thioglycolate IRG 651 IRGACURE .TM. 651,
2,2-dimethoxy-2-phenyl acetophenone photoinitiator, from BASF
Corporation, Florham Park, New Jersey KH-10 HITENOL .TM. KH-10,
reactive ionic surfactant from Dai-ichi Kogyo Seiyaku Co., Ltd.
SE-10N ADEKA REASOAP .TM. SE-10N, reactive ionic surfactant from
Adeka Corporation. SR-10 ADEKA REASOAP .TM. SR-10, reactive ionic
surfactant from Adeka Corporation. RN-20 RN-20, reactive non-ionic
surfactant from Dai-ichi Kogyo Seiyaku Co., Ltd.
Test Methods
[0119] 90.degree. Peel Adhesion to Dry Interlocking Concrete
Block
[0120] A 25 mm strip of adhesive sample, notch bar coated on a 50
micron thick PET film was attached to dry interlocking block (water
permeable interlocking block, "Pre Stone" Mini Red (200
mm.times.200 mm.times.30 mm, 2.3 kg weight/each) from Nakaichi Co.,
Ltd., Maebashi-city, Gunma, Japan) and was rolled down using one
pass with a 2 kg weight roller at a speed of approximately 30.5
cm/min. The 90.degree. peel adhesion was measured using a Model
RZ-100 Push-Pull gauge (Aikoh Engineering Co., Ltd., Osaka, Japan)
by attaching a triangular clip to the free end of the adhesive
sample using #800 Filament Tape (3M, St. Paul Minn.), attaching the
Push-Pull gauge to the triangular clip attached to the adhesive
sample and drawing the sample away from the interlocking concrete
block at an angle of 90.degree. and at a rate of approximately 10
mm/s. The reading was recorded in Newtons, and the reported data is
the average of a number of repeated tests.
[0121] Peel adhesions in the range of 5 N/dm or higher, as measured
by this procedure, were considered acceptably good for dry stick
adhesives of the present disclosure. Peel adhesions greater than 10
N/dm were considered to be "high adhesion" for the present
disclosure.
[0122] 90.degree. Peel Adhesion to Wet Interlocking Concrete
Block
[0123] A wet interlocking block was prepared as follows:
[0124] a) A 30 mm thick Pre Stone Mini Red interlocking concrete
block was completely submerged in container of 20.degree. C. water
for 1 hour.
[0125] b) The 30 mm thick block was removed from submersion, and
placed in a container, the container was filled with 20.degree. C.
water such that the bottom 15 mm of the concrete block were
immersed in the water. The top 15 mm were not immersed in
water.
[0126] c) The top surface of the concrete block was wiped with
paper towel to remove excess water from the surface.
[0127] With the wet block thus prepared, a 25 mm strip of adhesive
sample, notch bar coated on a 50 micron thick PET film, was
attached to the top surface of the wet interlocking block and was
rolled down using one pass with a 2 kg weight roller at a speed of
approximately 30.5 cm/min.
[0128] The container with the interlocking block, water and adhered
adhesive sample was covered and sealed with polyethylene film to
retain moisture until the peel test was conducted.
[0129] A 90.degree. peel adhesion was measured by using Model
RZ-100 Push-Pull gauge (Aikoh Engineering Co., Ltd.) by attaching a
triangular clip to the free end of the adhesive sample using #800
Filament tape (3M), attaching the Push-Pull gauge to the triangular
clip attached to the adhesive sample and drawing the sample away
from the interlocking concrete block at an angle of 90.degree. and
an a rate of approximately 10 mm/s. The reading was recorded in
Newtons, and the reported data is the average of a number of
repeated tests.
[0130] Peel adhesions in the range of 5 N/dm or higher, as measured
by this procedure, were considered acceptably good for wet-stick
adhesives of the present disclosure. Peel adhesions greater than 10
N/dm were considered to be "high adhesion" for the present
disclosure.
[0131] Tack Test
[0132] A 300 mm strip (2.54 centimeter wide) of adhesive sample,
notch bar coated on a 50 micron thick PET film, was laid flat,
adhesive coated side facing up. Tack was measured per ASTM D3121,
rolling ball tack test, using a 1.11 cm diameter steel ball.
Results are recorded as travel distance in mm of the steel ball.
Travel distance of 60 mm or less is defined as high tack. Travel
distance of 250 mm or less is defined as good tack. For some
applications, a higher tack corresponding to a travel distance of
30 mm or less, or even 10 mm or less, may be preferred.
Examples 1-13, Comparative Examples C1-C7
Preparation of Acrylate Wet-Stick Adhesive Compositions
[0133] For each Example or Comparative Example, a glass jar was
charged with (meth)acrylate monomers, hydrophilic non-acidic
co-monomer, reactive ionic surfactant, and 0.04% photoinitiator
(IRGACURE.TM. 651) in the amounts shown in Table 1, and stirred
until the photoinitiator had dissolved and a homogenous mixture was
obtained. Oxygen was removed from the mixture by introducing
nitrogen gas into the mixture via a tube inserted through an
opening in the jar's cap and bubbling vigorously for at least 3
minutes. The nitrogen flow rate was decrease to a level at which no
bubbles were observed and the contents of the jar were gently mixed
and exposed to UV-A light until a pre-adhesive syrup having a
viscosity deemed suitable for coating was formed. The target
viscosity was 3000 to 8000 centipoise.
[0134] The nitrogen supply was then stopped and the jar was opened
to introduce air into the jar.
[0135] The UV-A light source was a black light fluorescent lamps
having a peak emission of 350 nanometers, and having over 60
percent of its emission spectrum in the range of from about 280 nm
to about 400 nm.
[0136] Next, an additional 0.1 wt % IRGACURE.TM. 651 photoinitiator
was added to the pre-adhesive syrup and mixed until the
photoinitiator was dissolved.
[0137] The resulting pre-adhesive syrup was then coated as
follows:
[0138] Between two 50 micrometers thick, silicone coated polyester
films, pre-adhesive syrup was coated using a notch bar having a gap
setting of approximately 400 micrometers greater than the combined
thickness of the two support layers. The coated composition was
irradiated equally from both sides using UV-A black light
fluorescent lamps having a peak emission of 350 nanometers to
provide an approximate total energy of 1440 milliJoules/square
centimeter. (Top side: 720 milliJoules/square centimeter, Bottom
side: 720 milliJoules/square centimeter).
[0139] The total UV-A energy was determined using UV integrating
radiometer Model UR 365CH from Electronic Instrumentation &
Technology (EIT, LLC, Sterling, Va.) at a web speed of 1.0
meter/minute. The radiometer web speed and energy were then used to
calculate the total energy exposure at the web speed used during
curing of the pre-adhesive syrup.
[0140] Table 1 lists the respective formulation by component and
amount in parts by weight of each illustrative composition. All
data is in parts, except IOTG, which is in % of formulation.
TABLE-US-00002 TABLE 1 Exam- SE- SR- ple 2EHA DMA EHA:DMA KH10 10N
10 RN20 IOTG C-1 80 20 4.0:1 0 0 0 0 0 C-2 60 40 1.5:1 0 0 0 0 0
C-3 59 39 1.5:1 2 0 0 0 0 C-4 54 36 1.5:1 10 0 0 0 0 C-5 50 50 1:1
0 0 0 0 0 C-6 47 47 1:1 6 0 0 0 0 C-7 47 41 1:1 0 0 0 12 0 1 51 34
1.5:1 15 0 0 0 0 2 48 32 1.5:1 20 0 0 0 0 3 44.5 29.5 1.5:1 26 0 0
0 0 4 42 28 1.5:1 30 0 0 0 0 5 40 40 1:1 20 0 0 0 0 6 37 37 1:1 26
0 0 0 0 7 35 35 1:1 30 0 0 0 0 8 50 40 1.25:1 10 0 0 0 1.6 9 50 40
1.25:1 10 0 0 0 3.3 10 45 25 1.8:1 30 0 0 0 0 11 48.2 26.8 1.8:1 25
0 0 0 0 12 42 37 1.1:1 0 21 0 0 0 13 42 37 1.1:1 0 0 21 0 0
[0141] Both "wet" and "dry" peel adhesion as well as rolling ball
tack for specimens of each of these Examples and Comparative
Examples, were measured as described above. The results of these
tests are recorded in Table 2.
TABLE-US-00003 TABLE 2 Peel from Dry Rolling Block Peel from Wet
Block ball (N/25 mm) (N/25 mm) tack Example 60 min dwell 20 min
dwell 60 min dwell (mm) C-1 20.0 0.0 0.0 13 C-2 8.0 0.0 0.0 300+
C-3 4.0 0.0 2.0 300+ C-4 4.0 0.0 2.0 51 C-5 4.0 0.0 0.0 300+ C-6
0.0 0.0 12.0 300+ C-7 3.0 1.0 2.0 -- 1 6.0 2.0 4.0 22 2 8.0 11.0
15.0 19 3 12.0 15.0 14.0 13 4 16.0 17.0 10.0 9 5 4.0 18.0 20.0 37 6
5.0 14.0 16.0 19 7 6.0 14.0 13.0 4 8 10.0 6.5 21.0 233 9 12.0 12.0
18.0 68 10 8.0 3.0 4.5 22 11 3.0 1.0 3.5 24 12 6.5 6.0 8.0 -- 13
7.5 9.0 12.0 --
[0142] The data demonstrate that the use of at least 10 wt %
reactive ionic surfactant polymerized into a system with a ratio of
(meth)acrylate ester monomer to hydrophilic non-acidic monomer of
1:1 to 1.8:1, provides adhesives with a combination of initial wet
and dry adhesion as well good tack. The data demonstrate that when
reactive ionic surfactant is present in amounts less than 10 wt %,
initial wet-stick performance was not achieved. The data
demonstrate that good wet and dry adhesion were not obtained when a
reactive, non-ionic surfactant is used (C-7). The data demonstrate
that for adhesives made using 10 wt % reactive ionic surfactant,
(Ex 8 and Ex 9) the use of chain transfer agent can permit the
production of adhesives with initial wet adhesion, good dry
adhesion and good tack.
* * * * *