U.S. patent application number 14/138366 was filed with the patent office on 2014-04-24 for sprayable water-based adhesive.
This patent application is currently assigned to HENKEL US IP LLC. The applicant listed for this patent is HENKEL US IP LLC. Invention is credited to Jeffrey CASH, Richard W. JOHNSTON, Michael C. KASPRZAK, Daniel J. LOVULLO, Michael MAUE, Robert W. ROWITSCH, Brian J. STACHOWSKI.
Application Number | 20140113126 14/138366 |
Document ID | / |
Family ID | 38541446 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140113126 |
Kind Code |
A1 |
ROWITSCH; Robert W. ; et
al. |
April 24, 2014 |
SPRAYABLE WATER-BASED ADHESIVE
Abstract
Water-based adhesive compositions are improved by the
incorporation of hollow polymeric microspheres having outer
surfaces coated with one or more barrier materials such as calcium
carbonate particles. The adhesive compositions exhibit enhanced
rheology, sprayability, drying time, tack and storage stability as
compared to analogous adhesives that are not modified with coated
hollow polymeric microspheres. Such compositions are useful as both
contact adhesives as well as wet bonding one-way adhesives.
Inventors: |
ROWITSCH; Robert W.;
(Springville, NY) ; CASH; Jeffrey; (Travelers
Rest, SC) ; MAUE; Michael; (Buffalo, NY) ;
LOVULLO; Daniel J.; (Eden, NY) ; STACHOWSKI; Brian
J.; (Lackawanna, NY) ; KASPRZAK; Michael C.;
(Lackawanna, NY) ; JOHNSTON; Richard W.; (Ontario,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HENKEL US IP LLC |
Rocky Hill |
CT |
US |
|
|
Assignee: |
HENKEL US IP LLC
Rocky Hill
CT
|
Family ID: |
38541446 |
Appl. No.: |
14/138366 |
Filed: |
December 23, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11690497 |
Mar 23, 2007 |
|
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14138366 |
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60785559 |
Mar 24, 2006 |
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Current U.S.
Class: |
428/313.5 ;
156/333; 521/76 |
Current CPC
Class: |
Y10T 428/251 20150115;
Y10T 442/699 20150401; C08L 11/02 20130101; Y10T 428/24372
20150115; C09J 147/00 20130101; C09J 2301/412 20200801; Y10T
428/254 20150115; C09J 5/00 20130101; C09J 111/00 20130101; C08L
11/00 20130101; C09J 11/08 20130101; Y10T 428/25 20150115; C08L
2666/04 20130101; Y10T 428/2438 20150115; Y10T 428/249972 20150401;
C08K 3/013 20180101; C08L 33/00 20130101; Y10T 428/24405 20150115;
C09J 111/00 20130101; C08L 2666/04 20130101 |
Class at
Publication: |
428/313.5 ;
156/333; 521/76 |
International
Class: |
C09J 147/00 20060101
C09J147/00; C09J 5/00 20060101 C09J005/00 |
Claims
1-29. (canceled)
30. A water-based adhesive composition comprising at least about 30
weight percent of water, based on the weight of the water-based
adhesive composition; an adhesive polymer comprising at least one
homopolymer or copolymer of chloroprene, or a blend of at least one
homopolymer or copolymer of chloroprene and at least one acrylic
copolymer, wherein the adhesive polymer has a glass transition
temperature that is less than about 0.degree. C.; and about 1
weight percent to about 3 weight percent of hollow, polymeric
microspheres, based on the weight of the water-based adhesive
composition, wherein the microspheres are coated with at least one
barrier material.
31. The water-based adhesive composition of claim 30, wherein the
microspheres are coated with talc, calcium carbonate, barium
sulfate, alumina, silica, carbon, titanium dioxide, zinc oxide,
ceramic beads, quartz beads, glass beads, poly(tetrafluoroethylene)
beads, glass fibers, cotton fibers, polyamide fibers, carbon
fibers, ceramic fibers, or a mixture thereof.
32. The water-based adhesive composition of claim 30, wherein the
microspheres have a composite density of not greater than about
0.15 g/cm.sup.3, as measured including the outer coating.
33. The water-based adhesive composition of claim 30, wherein the
microspheres are thermally clad with the at least one barrier
material.
34. The water-based adhesive composition of claim 30, wherein the
shells of the microspheres comprise at least one thermoplastic
polymer.
35. The water-based adhesive composition of claim 30, wherein the
shells of the microspheres comprise a polymer that is a methyl
methacrylate-acrylonitrile copolymer, a vinylidene
chloride-acrylonitrile copolymer, or a vinylidene
chloride-acrylonitrile-methyl methacrylate copolymer.
36. The water-based adhesive composition of claim 30, wherein the
microspheres are pre-expanded.
37. The water-based adhesive composition of claim 30, wherein the
adhesive polymer has a glass transition temperature that is less
than about -20.degree. C.
38. The water-based adhesive composition of claim 30, further
comprising at least one additive selected from the group consisting
of an antioxidant, a defoamer, a wetting agent, a fungicide, a
preservative, a biocide, a stabilizer, a tackifying resin, a
filler, a processing oil, a corrosion inhibitor, a pigment, a
plasticizer, an adhesion promoter, a viscosity modifier, an
internal coagulant, a pH adjustment agent, a flame retardant, a
rheology improver, or a mixture thereof.
39. The water-based adhesive composition of claim 30, wherein the
microspheres have an average diameter of about 20 microns to about
60 microns.
40. The water-based adhesive composition of claim 30, wherein the
water-based adhesive composition has a viscosity of less than about
300 Pas at a shear stress of 10 Pa.
41. A process for bonding a first substrate to a second substrate
comprising applying the water-based adhesive composition of claim
30 on a surface of the first substrate; drying, at least partially,
the water-based adhesive composition to form an adhesive film layer
on the surface of the first substrate; and bonding the first
substrate to the second substrate.
42. The process of claim 41, wherein the bonding is by contacting
the second substrate with the adhesive film layer on the surface of
the first substrate.
43. The process of claim 41, further comprising prior to the
bonding step, applying the water-based adhesive composition of
claim 30 on a surface of the second substrate; and drying, at least
partially, the water-based adhesive composition to form an adhesive
film layer on the surface of the second substrate; wherein the
bonding is by contacting the adhesive film layer on the surface of
the second substrate with the adhesive film layer on the surface of
the first substrate.
44. The process of claim 41, wherein the application is by
spraying.
45. The process of claim 42, further comprising pressing the first
and second substrates together.
46. The process of claim 42, wherein the adhesive film layer is
heated above ambient temperature prior to contacting the second
substrate with the adhesive film layer on the surface of the first
substrate.
47. The process of claim 41, wherein the first and second
substrates are plastic, wood, metal, rubber, glass, ceramic, paper,
fabric, plasterboard, fiber, leather, concrete, rock, or sheet
rock.
48. The process of claim 41, wherein one or both of the first and
second substrates are porous substrates.
49. The process of claim 44, wherein the water-based adhesive
composition is sprayed on the surface of the first substrate from a
pressurized canister.
50. An assembly produced according to the process of claim 41.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Application No. 60/785,559, filed 24 Mar. 2006 and incorporated
herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] This application relates to a sprayable water-based adhesive
containing a plurality of barrier material-coated polymeric hollow
microspheres, to its production and to its use.
BACKGROUND OF THE INVENTION
[0003] In the past, most commercially available contact adhesives
have been solvent-based, i.e., adhesives containing one or more
volatile organic solvents. "Contact adhesives" are adhesives which
typically are applied to the surfaces of two substrates that are to
be joined together and dried to form an adhesive coating layer on
the substrate surfaces, with the adhesive coating layers then
brought into contact with each other under pressure to form an
immediate, durable bond. Such adhesives typically comprise an
elastomeric polymer dissolved in solvent, perhaps in combination
with certain other components. The elastomeric polymer provides the
basis for forming an effective adhesive bond upon setting of the
contact adhesive.
[0004] It is usually desirable that the contact adhesive applied to
the substrate surface quickly dries to form an adhesive film that
is capable of providing sufficient bond strength shortly after the
adhesive film layers are brought together under pressure such that
the joined substrates are effectively held together and
substantially resist separation during subsequent handling (e.g.,
after the contacting pressure is released). Fast drying (i.e.,
highly volatile) organic solvents have traditionally been used to
formulate contact adhesives, particularly sprayable contact
adhesives, since such solvents offer the advantage of short dry
times, wherein the applied coating of adhesive is ready to be
bonded to another coated substrate shortly after being applied so
that assembly times for the bonded substrates and therefore
production rates may be optimized.
[0005] However, the use of organic solvent-based contact adhesives
has come under increased scrutiny in recent years because of
environmental and worker exposure concerns. In addition, many
organic solvents are flammable. Due to the harm that at least
certain organic solvents used in such adhesives may cause after
being released into the atmosphere upon drying of the adhesive,
regulations on these solvent-based contact adhesives have become
stricter. Although in principle it is possible to control solvent
losses and emissions through the installation of ventilation and
recycling systems, such systems significantly add to the cost of
employing such adhesives and in certain end-use applications (such
as the construction industry) it is simply not practical to do so.
As a result, there has been an increasing interest in developing
alternative adhesives that avoid the use of volatile organic
solvents altogether. Water-based contact adhesives represent one
type of adhesive that can in principle be substituted for the
traditional solvent-based contact adhesives and to date have
typically been formulated to include a latex or emulsion of an
elastomeric polymer in water. Polychloroprene is an example of a
suitable elastomeric polymer for such formulations, as described in
more detail in Gerlach, "Polychloroprene--An Evergreen Product for
the Formulation of Water Based Contact Adhesives", Advances in
Adhesives & Sealants Technology, Paper 14, 1994; and U.S. Pat.
Nos. 6,086,997 and 6,440,259 (each of which is incorporated herein
by reference in its entirety).
[0006] However, the water-based contact adhesives developed to date
have typically suffered from a number of deficiencies as compared
to the conventional organic solvent-based contact adhesives. For
example, the solvent-based contact adhesives have good storage and
shelf stability, whereas the water-based contact adhesives have a
tendency to coagulate over time. Such coagulation substantially
interferes with the ease with which the adhesive can be applied to
a substrate surface, especially by spraying. Although stabilizers
(such as emulsifying agents) are commonly used to increase the
stability of the elastomeric polymer emulsion, the water-based
contact adhesives still tend to have a relatively short shelf life,
particularly at elevated temperatures. Also, the water-based
contact adhesives are more difficult to apply to substrate surfaces
by spraying than the solvent-based contact adhesives, as the spray
pattern observed is generally far inferior. The use of water as a
contact adhesive carrier instead of an organic solvent additionally
tends to greatly decrease both the drying rate and the degree of
tack attained in the dried adhesive film. Such deficiencies have
made it difficult for water-based contact adhesives to fully
replace solvent-based contact adhesives, even though significant
environmental, health and safety advantages could thereby be
achieved. Further improvements in water-based contact adhesive
formulations are therefore highly desired by the adhesive industry
as well as the end users of such adhesives.
[0007] U.S. Pat. No. 5,264,467 discloses aqueous high performance
contact adhesives containing an adhesive polymer emulsion and
thermoplastic hollow microspheres. The adhesive polymer can be a
vinyl acetate-ethylene, acrylic, styrene-acrylic, styrene butadiene
or neoprene polymer. However, there is no teaching or suggestion
that microspheres having an outer coating of a barrier material
could be utilized. In addition, U.S. Pat. No. 5,264,467 does not
mention that such contact adhesives could be applied by spraying or
could be provided in sprayable form within a pressurized
container.
BRIEF SUMMARY OF THE INVENTION
[0008] It has now been surprisingly discovered that the
incorporation of hollow polymeric microspheres having outer
surfaces coated with at least one barrier material (such as finely
divided calcium carbonate particles) into a water-based adhesive
composition comprising an aqueous emulsion of at least one
elastomeric adhesive polymer (e.g., a chloroprene polymer) provides
significant benefits as compared to analogous formulations that do
not contain such coated microspheres. In particular, the storage
stability/shelf life, drying rate and tack are all improved. For
example, contactability of the adhesive film during the bonding
phase is enhanced. Additionally, the presence of the coated
microspheres unexpectedly causes the spray pattern of the
water-based adhesive to widen and soften, thereby making the
adhesive much easier to apply in a satisfactory manner to a
substrate surface by spraying. Another surprising effect of the
coated microspheres is that the bonding attributes of a water-based
contact adhesive are preserved or even enhanced at loadings of up
to at least about 5 percent by weight of the coated microspheres,
even though the density of the adhesive is significantly reduced.
The coated microspheres preferably do not contain significant
amounts of free volatile organic compounds and thus do not
compromise the recognized environmental and worker exposure
advantages of water-based contact adhesives.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION
[0009] The following are among the advantages provided by at least
certain embodiments of the adhesives of the present invention:
[0010] Density reduction [0011] Reduction in applied cost [0012]
Increased storage stability (maintenance of homogeneity) [0013] Gap
filling properties [0014] High build [0015] Enhanced application
properties [0016] Sound deadening [0017] Reduced thermal transfer
[0018] Increased modular strength [0019] Reduced bonding pressures
[0020] Increased flexural strength [0021] Vibration dampening
[0022] Improved impact/fracture resistance
[0023] The reasons why such enhancements are realized are not
completely understood, but it has been observed that a dried film
or coating of an adhesive in accordance with the present invention
generally exhibits a homogeneous dispersion of the coated hollow
polymeric microspheres throughout the film or coating, wherein each
individual microsphere is uniformly coated or surrounded by a
matrix containing the elastomeric adhesive polymer. Water-borne
adhesives in accordance with the present invention surprisingly
have much higher shear strength as well as much higher bond
strength at significantly lower bonding pressures as compared to
unfilled adhesives (i.e., water-borne adhesives that do not contain
coated hollow polymeric microspheres). Additionally, the
water-borne adhesives of the present invention exhibit much better
application properties than water-borne adhesives filled to the
same volume with conventional solid particulate mineral fillers.
For example, the viscosity of an adhesive in accordance with the
invention drops into a range suitable for application by spraying,
brushing, or rolling with only minimal shear energy, whereas the
use of much higher shear energy often is ineffective in achieving a
suitably low application viscosity in the case of a calcium
carbonate-filled water-borne contact adhesive.
[0024] The adhesives of the present invention are water-based,
meaning that substantial amounts of water are present in the
composition. Typically, the adhesive contains at least about 30
weight percent water or at least about 40 weight percent water and
the solid components of the adhesive are stably suspended in an
aqueous phase. Preferably, the adhesive composition is free or
essentially free of volatile organic solvents and other volatile
organic compounds. For example, in preferred embodiments the
adhesive comprises less than 1 weight percent or less than 0.5
weight percent or less than 0.1 weight percent or even 0 wt. %
total volatile organic compounds (defined as compounds having vapor
pressures equal to or greater than 0.1 mm Hg).
[0025] The water-based adhesives of the present invention are
comprised of an aqueous emulsion of at least one elastomeric
adhesive polymer. The elastomeric adhesive polymer may be any of
the rubbery macromolecular materials generally having glass
transition temperatures below room temperature (e.g., less than
about 0.degree. C. or less than about -20.degree. C.)
conventionally used or known in the formulation of adhesives
containing latex emulsions or dispersions. These materials include,
but are not limited to, acrylic homopolymers and copolymers
(including homopolymers and copolymers of C1-C12 alkyl acrylates
and/or methacrylates, where such monomers may be copolymerized with
other types of ethylenically unsaturated monomers, particularly
homopolymers and copolymers having relatively low glass transition
temperatures), acrylonitrile-butadiene copolymers, diene
copolymers, polydimethyl butadiene, styrene-isoprene copolymers,
isoprene-acrylonitrile copolymers, diene-vinyl aromatic monomer
copolymers, polyvinyl acetates, ethylene-vinyl acetate copolymers,
styrene-butadiene rubbers, styrene-acrylic copolymers (including
styrenated acrylic resins), nitrile rubbers, polyisoprene,
polybutadiene, natural rubber (including natural rubber that has
been modified or graft copolymerized with ethylenically unsaturated
monomers such as (meth)acrylic monomers and/or vinyl aromatic
monomers), polyurethanes and the like and mixtures, hybrids or
blends thereof, including functionalized derivatives thereof (e.g.,
carboxylated styrene-butadiene rubbers, carboxylated ethylene-vinyl
acetate copolymers). The elastomeric adhesive polymer may be linear
or branched, crosslinked or non-crosslinked, thermoplastic or
thermoset. Methods of preparing emulsions of such polymers in water
are well-known in the art. Typically, the emulsion will contain
about 30% to about 70% by weight of the polymer, the balance being
predominately water although small amounts of other substances such
as emulsifiers, stabilizers, organic solvents and the like are
often also present. The emulsified polymer will generally be
present in the form of particles having an average size of from
about 0.1 to about 1 microns in diameter.
[0026] In a particularly preferred embodiment of the invention, the
adhesive comprises a homopolymer or copolymer of chloroprene in the
form of an emulsion. The chloroprene thus may be either
homopolymerized or copolymerized with one or more other
ethylenically unsaturated monomers such as styrene, vinyl toluene,
and other vinyl aromatic compounds, other dienes such as
2,3-dichlorobutadiene, isoprene, butadiene and the like,
unsaturated carboxylic acids and esters thereof such as acrylic
acid, methacrylic acid and C1-C12 alkyl esters thereof, nitriles
such as acrylonitrile and methacrylonitrile, and the like. Many
different types of polychloroprene are available. For example, the
crystallinity of polychloroprene may vary from low to high. Also,
polychloroprene may contain varying amounts of crosslinked polymer
or "gel". The type of polychloroprene used can influence the
ability of the adhesive composition to achieve a fast set time as
well as other properties and characteristics of a water-based
contact adhesive (e.g., elongation, dry tack, cohesive strength,
modulus, tensile strength, hardness), as is well known in the art
and as is described in Gerlach, "Polychloroprene--An Evergreen
Product for the Formulation of Water Based Contact Adhesives",
Advances in Adhesives & Sealants Technology, Paper 14, 1994.
Copolymerization of chloroprene with one or more comonomers is
another way in which the adhesive properties may be controlled as
desired. "Carboxylated" chloroprene polymers can also be
utilized.
[0027] Emulsions of chloroprene polymers and copolymers are
typically prepared by emulsion polymerization, wherein free radical
initiators are added to an emulsion of monomer(s) and surfactants
(sometimes also referred to as emulsifiers or emulsion stabilizers)
in water. Polymerization occurs through a free radical growth
mechanism in which the initiator generates free radicals which
react with successive monomer molecules at an active chain end. The
polymer particles which form and which are initially submicron in
size are stabilized by the surfactants. Commonly used surfactants
for this purpose include anionic as well as nonionic surfactants.
Stabilizers such as polyvinyl alcohol or rosins can also be
utilized. Self-emulsification may also be possible when certain
functionalized comonomers are copolymerized with the chloroprene.
The molecular weight of the polymer chain can be controlled through
the addition of chain transfer agents. Crystallinity can be
controlled by polymerization temperature, comonomers and other
variables. As explained in the aforementioned paper by Gerlach,
crystallinity can be affected by the different configurations in
which the chloroprene monomer can enter into the polymer backbone,
including 1,4 trans, 1,4 cis, 1,2, and 3,4 configurations. The gel
content is typically affected by the degree of monomer conversion
achieved during polymerization. A pH control agent (e.g., a base)
may be present to prevent the emulsion from coagulating
prematurely.
[0028] Polychloroprene emulsions from commercial sources may be
utilized in the contact adhesives of the present invention.
Suitable anionic surfactant-stabilized polychloroprene emulsions,
for example, include those available from DuPont Dow Elastomers
under the tradenames: LATEX 750; AQUASTIK 2161 (a copolymer with
2,3-dichlorobutadiene); AQUASTIK 2540 (also a copolymer with
2,3-dichlorobutadiene); AQUASTIK 2900; AQUASTIK 2901; AQUASTIK
2920, AQUASTIK 2540, AQUASTIK 2126 and AQUASTIK 9426. Another
suitable anionic surfactant-stabilized polychloroprene emulsion is
DISPERCOLL C-74, available from Bayer. A suitable anionic/nonionic
surfactant-stabilized polychloroprene blend emulsion is available
from Bayer under the tradename DISPERCOLL C-84. A nonionically
stabilized chloroprene/methacrylic acid copolymer emulsion that is
suitable for use is available from DuPont Dow Elastomers under the
tradename AQUASTIK 1120.
[0029] The adhesives of the present invention may contain a mixture
of different elastomeric adhesive polymers such as, for example, a
blend of polychloroprene and natural rubber or a blend of
polychloroprene and styrene-butadiene rubber or a blend of
polychloroprene and an acrylic polymer or copolymer. The adhesive
may also contain, in addition to the elastomeric adhesive polymer,
a different type of polymer or resin such as a non-elastomeric
thermoplastic (for example, an acrylic homopolymer or copolymer
having a glass transition temperature above 20 degrees C.) or a
reactive resin such as an epoxy resin. In preferred embodiments of
the invention, however, the adhesive is free or essentially free of
reactive resins (i.e., resins capable of being cured or
cross-linked by reaction with curatives or cross-linking
agents).
[0030] Preferably, the adhesives of the present invention are
one-part (one-component) adhesives, i.e., they do not need to be
applied from two separate containers or mixed immediately prior to
application or upon application to a substrate surface.
[0031] As previously noted, the sprayable water-based adhesives of
the present invention contain a plurality of hollow polymeric
microspheres having outer surfaces coated with at least one barrier
material. Preferably, the microspheres are already expanded when
combined with the other components of the adhesive, although
expandable microspheres could alternatively be utilized. The outer
surfaces of the hollow polymeric microspheres are preferably
covered with an adherent coating of a surface barrier solid, a
surface barrier liquid or a mixture of a surface barrier liquid
with a surface barrier solid. Microspheres having such adherent
coatings generally have free flowing properties when dried and are
sometimes referred to in the art as thermally clad
microspheres.
[0032] Although the size of the microspheres is not believed to be
particularly critical, typically the microspheres useful in the
present invention will have diameters of from about 5 microns to
about 500 microns. In one embodiment, the particle size (diameter)
of the microspheres is from about 20 to about 60 microns. In
preferred embodiments of the invention, the composite density
(i.e., the density of the coated hollow polymeric microspheres) is
from about 0.06 to about 0.15 g/cm.sup.3. The precise density of
the microspheres selected for use is not thought to be especially
important, although generally speaking the microsphere density will
not be greater than about 0.04 g/cm.sup.3 (as calculated in the
absence of the barrier material outer coating). This microsphere
density may be calculated from the measured composite density using
the known weight ratios of the microspheres and surface barrier
material(s) used to prepare the coated microspheres.
[0033] Methods of preparing expandable hollow polymeric
microspheres are well-known in the art and are described, for
example, in the following United States patents and applications,
each of which is incorporated herein by reference in its entirety:
U.S. Pat. Nos. 3,615,972; 3,864,181; 4,006,273; 4,044,176;
6,365,641; 6,235,800; 5,834,526; 5,155,138; 5,536,756; 6,903,143;
6,235,394; 6,509,384; and 2005-0080151. Typically, such expandable
hollow polymeric microspheres comprise a hollow polymeric shell and
a blowing agent such as a volatile hydrocarbon or halogenated
hydrocarbon contained therein.
[0034] The preparation of hollow polymeric microspheres containing
an adherent outer coating of a barrier material (also sometimes
referred to as a processing aid) such as a barrier solid and/or a
barrier liquid (e.g., thermally clad hollow polymeric microspheres)
from such expandable hollow polymeric microspheres is also
well-known in the art, as described, for example, in the following
United States patents and applications, each of which is
incorporated herein by reference in its entirety: U.S. Pat. Nos.
4,722,943; 4,829,094; 4,843,104; 4,888,241; 4,898,892; 4,898,894;
4,908,391; 4,912,139; 5,011,862; 5,180,752; 5,580,656; 6,225,361;
5,342,689; and 2005-0282014. As described in certain of the
aforementioned patents, coating of the microspheres may be carried
concurrently or sequentially in coordination with drying and
expansion. However, the barrier material-coated microspheres need
not be dried before being incorporated into the water-based
adhesives of the present invention.
[0035] Hollow polymeric microspheres can be made from a rather wide
diversity of thermoplastic polymers (including crosslinked
thermoplastic polymers) as well as thermoset polymers. In practice,
the polymers used in commercially available microspheres are
generally limited to polyvinylidene chloride homopolymers, random
copolymers of vinylidene chloride and acrylonitrile, and random
terpolymers of polyvinylidene chloride, acrylonitrile, and divinyl
benzene. Microspheres of other materials, such as
polyacrylonitrile, polyalkyl methacrylates, polystyrene, or vinyl
chloride, are known, but such microspheres are not widely and
generally available.
[0036] Suitable polymers for the formation of hollow polymeric
microspheres for use in the present invention include materials
which are effective vapor barriers to the blowing agent at
expansion temperatures, and which have adequate physical properties
to form self-supporting expanded microspheres.
[0037] Acrylic monomers useful in forming the thermoplastic
polymers in the manufacture of microspheres useful in the present
invention include acrylonitrile, methacrylonitrile, alkyl acrylates
and alkyl methacrylates, including methyl methacrylate, methyl
acrylate, butyl acrylate, butyl methacrylate, isobutyl
methacrylate, stearyl methacrylate, and other related acrylic
monomers such as 1,3-butylene dimethacrylate, allyl methacrylate,
trimethylolpropane trimethacrylate, trimethylolpropane triacrylate,
1,4-butanediol dimethacrylate, 1,3-butanediol dimethacrylate,
isobornyl methacrylate, dimethylaminoethyl methacrylate,
hydroxyethyl methacrylate, hydroxypropyl methacrylate, diurethane
dimethacrylate, and ethylene glycol dimethacrylate. Other,
non-acrylic monomers such as, for example, styrene, di-vinyl
benzene, vinylidene chloride and the like, may be included in the
copolymer, typically in minor proportions.
[0038] The monomers used to prepare the thermoplastic may comprise
multifunctional monomers which are capable of introducing
crosslinking. Such monomers include two or more carbon-carbon
double bonds per molecule which are capable of undergoing addition
polymerization with the other monomers. Suitable multifunctional
monomers include divinyl benzene, di(meth)acrylates,
tri(meth)acrylates, allyl(meth)acrylates, and the like. If present,
such multifunctional monomers preferably comprise from about 0.1 to
about 1 weight percent or from about 0.2 to about 0.5 weight
percent of the total amount of monomer. In one embodiment, the
thermoplastic is a terpolymer of acrylonitrile, vinylidene chloride
and a minor proportion (normally less than 5% by weight) of divinyl
benzene. Microspheres comprised of this preferred terpolymer are
commercially available from Sovereign Specialty Chemicals (now part
of Henkel Corporation).
[0039] In another embodiment, the thermoplastic is a copolymer
containing 0-80% by weight vinylidene chloride, 0-75% by weight
acrylonitrile, and 0-70% by weight methyl methacrylate, wherein at
least two of these monomers are utilized. In still another
embodiment, the thermoplastic is prepared by copolymerization of
0-55% by weight vinylidene chloride, 40-75% by weight
acrylonitrile, and 0-50% by weight methyl methacrylate, with at
least two of such monomers being employed. For example, the
thermoplastic may be a methyl methacrylate-acrylonitrile copolymer,
a vinylidene chloride-acrylonitrile copolymer or a vinylidene
chloride-acrylonitrile-methyl methacrylate copolymer.
[0040] In one preferred embodiment of the invention, the hollow
polymeric microspheres are thermally clad with an outer adherent
coating of at least one solid particulate material selected from
the group consisting of pigments, reinforcing fillers,
and:reinforcing fibers, such as those conventionally used in
polymer formulations. For example, talc, calcium carbonate
(including colloidal calcium carbonate), barium sulfate, alumina
(particularly alumina tri-hydrate), silica, titanium dioxide, zinc
oxide, and the like may be employed. Other materials of interest
include spherical or hollow beads of ceramics, quartz, glass or
polytetrafluoroethylene, or the like.
[0041] Among the fibrous materials of interest are glass fibers,
cotton flock, polyamide fibers, particularly aromatic polyamide
fibers, carbon and graphite fibers, metallic fibers, ceramic
fibers, and the like. Conductive surface barrier coatings, such as
conductive carbon, copper or steel fibers, and organic fibers with
conductive coatings of copper or silver or the like are also of
particular use. The solid barrier material (solid processing aid)
typically is relatively small in size, i.e., is a finely divided
solid. The particle size is not believed to be especially critical,
but generally will be smaller on average than the average particle
size of the hollow polymeric microspheres on which it is coated.
For example, the barrier material may have an average particle size
of at least about 0.01 microns or about 0.1 microns and not greater
than about 10 microns or about 5 microns. The particles may be
regular or irregular in shape, e.g., spherical, rod-like, fibrous,
platelet, and so forth. In certain embodiments, at least a portion
of the particulate solid barrier material is embedded in and/or
bound to the outer surfaces of the microspheres.
[0042] Barrier material-coated hollow polymeric microspheres
suitable for use in the present invention are available from
commercial sources, including the expanded microspheres sold under
the DUALITE brand name by Sovereign Specialty Chemicals (now part
of Henkel Corporation). Specific illustrative microspheres that can
be used include, for example, DUALITE MS7000.
[0043] Although the precise concentration of the coated hollow
polymeric microspheres in the water-based adhesive is not believed
to be particularly critical, typically at least about 0.2 or at
least about 0.5 percent by weight (calculated on a dry basis)
coated microspheres are utilized. Typically, the coated microsphere
concentration is not greater than about 10 percent by weight or not
greater than about 6 percent by weight.
[0044] In certain embodiments of the invention, the water-based
adhesive will advantageously contain from about 20 to about 60
volume % (e.g., from about 25 to about 55 volume % or from about 30
to about 50 volume %) coated hollow polymeric microspheres.
[0045] The adhesive according to the present invention may
additionally comprise one or more of the following: antioxidants
(e.g., hindered phenols), defoamers, wetting agents or surfactants
(e.g., non-ionic surfactants), fungicides, blowing agents,
chelating or sequestering agents (e.g., sodium silicate, ethylene
diamine salts, phosphates), preservatives, dispersants, biocides,
stabilizers, accelerators, crosslinking agents and curing agents
(e.g., thiocarbanilide, butyl zimate, or amines, although in
preferred embodiments the adhesive is free or essentially free of
crosslinking agents and curing agents), sulfur, tackifying resins
(e.g., coumarone-indene resins, polyterpenes, terpene phenolic
resins, resin esters, hydrocarbon resins, rosin acids), UV and
ozone screening agents (e.g., carbon black, red iron oxide, waxes,
fatty oils, antiozonants), fillers (e.g., clay, calcium carbonate,
feldspar, hydrated alumina), processing oils, corrosion inhibitors
(e.g., potassium or sodium nitrite), pigments (carbon black, red
iron oxide, black iron oxide), plasticizers (e.g., esters such as
phthlate and benzoate esters such as dioctyl phthalate, diethylene
glycol dibenzoate, dipropylene glycol dibenzoate, oils such as
hydrocarbon oils, glycols such as diethylene glycol), melamine
formaldehyde resins, adhesion promoters/coupling agents, viscosity
modifiers or thickeners (e.g., acrylates, cellulose derivatives,
polyurethane based thickeners, caseinates, clays, silica gel), acid
acceptors (e.g., metal oxides such as zinc oxide), internal
coagulants (e.g., amino acids such as glycine), humectants (e.g.,
glycerin, diethylene glycol, propylene glycol and other
polyalcohols), pH adjustment agents (e.g., bases such as alkali
metal hydroxides and amines, acids such as citric, boric or formic
acid), flame retardants (e.g., hydrated alumina, antimony trioxide,
zinc borate, chlorinated or brominated paraffin waxes), mechanical
stabilizers (e.g., caseinates), and/or rheology improvers.
Preferably, the adhesive is essentially free or entirely free of
any volatile organic compounds (VOCs).
[0046] Any tackifier known in the art that can yield the properties
desired in the adhesive composition can be utilized. Generally, the
tackifier can be selected from the group consisting of rosins,
rosin derivatives, rosin esters, hydrocarbon resins, synthetic
polyterpenes, natural terpenes, and the like. More particularly,
useful tackifying resins include, but are not limited to, (1)
natural and modified rosins and the hydrogenated derivatives
thereof; (2) esters of natural and modified rosins and the
hydrogenated derivatives thereof; (3) polyterpene resins and
hydrogenated polyterpene resins; (4) aliphatic petroleum
hydrocarbon resins and the hydrogenated derivatives thereof; (5)
aromatic hydrocarbon resins and the hydrogenated derivatives
thereof; and (6) alicyclic petroleum hydrocarbon resins and the
hydrogenated derivatives thereof. Mixtures of two or more of the
above-described tackifiers may be required for some formulations.
Natural and modified rosins and the hydrogenated derivatives
thereof include, but are not limited to, gum rosins, wood rosins,
tall-oil rosins, distilled rosins, hydrogenated rosin, dimerized
rosins, and polymerized rosins. Suitable examples of esters of
natural and modified rosins and the hydrogenated derivatives
thereof include, but are not limited to, the glycerol esters of
rosins, the glycerol esters of hydrogenated rosins, the glycerol
esters of polymerized rosins, and the pentaerythritol esters of
hydrogenated rosins. Polyterpene resins generally result from the
polymerization of terpene hydrocarbons, such as the bicyclic
monoterpene known as pinene, in the presence of Friedel-Crafts
catalysts at moderately low temperatures. Aliphatic petroleum
hydrocarbon resins and hydrogenated derivatives thereof are
generally produced from the polymerization of monomers consisting
of primarily olefins and diolefins. Aromatic hydrocarbon resins
include, for example, hydrocarbon resins derived from at least one
alkyl aromatic monomer, such as, for example, styrene, alpha-methyl
styrene and vinyl toluene, and the hydrogenated derivatives
thereof. The alkyl aromatic monomers can be obtained from petroleum
distillate fractions or from non-petroleum feedstocks, such as, for
example, feedstocks produced from phenol conversion processes. An
alicyclic petroleum hydrocarbon resin can be produced utilizing a
hydrocarbon mixture comprising dicyclopentadiene as the
monomer.
[0047] The optional additives mentioned above may, for convenience,
be utilized in the form of aqueous dispersions or emulsions. That
is, the additive may be dispersed or emulsified in water at the
time it is combined with the other components of the adhesive. For
example, the tackifier may be added as a tackifier dispersion in
water. Examples of tackifier dispersions that can be added to the
adhesive composition are disclosed in U.S. Pat. Nos. 4,526,577,
4,460,728 and 4,411,954, all of which are herein incorporated by
reference in their entirety.
[0048] Illustrative adhesives in accordance with the present
invention which are particularly suitable for application by
spraying may, for example, comprise water and:
TABLE-US-00001 Polychloroprene.sup.1 25-40 or 30-35 wt. %
Antioxidant(s) 0.5-5 or 1-3 wt. % Acid Acceptor(s) 0.5-5 or 1-3 wt.
% Plasticizer(s) 1-6 or 2-4 wt. % Tackifier(s) 10-20 or 12-18 wt. %
Pigment(s) 0-1 or 0.01-0.5 wt. % Coated Microspheres 0.5-6 or 1-3
wt. % .sup.1Added as emulsion in water (typically, ca. 40-60 wt. %
polymer; concentrations listed are based on dry weight of
polymer).
[0049] The weight percent concentration ranges stated are based on
the dry (solids) weight of each component. Preferably, the
polychloroprene, antioxidants, acid acceptors, tackifiers and
pigment are supplied to the adhesive composition in the form of
aqueous dispersions or emulsions (typically, containing about 25 to
about 60 weight % solids). Such adhesives may additionally contain
relatively minor amounts (e.g., less than about 0.1 weight %) of
one or more other additives such as surfactants, solvents (e.g.,
glycol ethers), pH control agents (e.g., alkali metal hydroxide),
and the like. In certain embodiments, the components of the
water-based adhesive composition are selected so as to provide a
viscosity at 20 degrees C. of not more than about 3000 Pas at a
shear stress of 10 Pa and of not more than about 200 Pas
(alternatively, not more than about 100 Pas) at a shear stress of
40 Pa.
[0050] The adhesive compositions of the present invention can be
prepared by mixing the selected ingredients together at
approximately room temperature. Conventional, low shear mixing
equipment can be used. For convenience, certain of the ingredients
(in particular, the elastomeric adhesive polymer) may be added to
or combined into the mixture in an already emulsified or dispersed
state, for example as an emulsion of about 50 to about 60 weight
percent of the polymer in water).
[0051] The adhesives of the present invention may be employed in
any of the applications and end uses where water-based contact
adhesives are conventionally utilized. Typical applications
include, but not limited to, adhering carpet, carpet padding,
ceramic tiles, resilient tiles, resilient sheet goods, wooden
planks and boards, wooden tiles, synthetic flooring material, and
other such materials that are used for flooring purposes to
flooring surfaces or other suitable substrates comprised of wood,
concrete, or the like. The adhesive may also, for example, be
utilized in general construction, curtain wall construction, high
pressure lamination, film and foil lamination, tapes,
do-it-yourself products, hobbies and crafts, manufacturing, boat
construction, mobile home construction, vehicle assembly, wall
covering installation, edge banding, furniture construction,
countertop construction (e.g., lamination of a decorative plastic
veneer to a wood or other cellulosic core or support material),
container labelling, and so forth.
[0052] The adhesives of the present invention can generally be used
in methods for contact bonding substrates together, wherein the
water-based adhesive is applied in wet form to surfaces of a first
substrate and a second surface, the adhesive is permitted to dry at
least partially to form an adhesive film layer on each substrate
surface, and the substrate surfaces having the adhesive film layers
thereon brought together to form an adhesive bond joining the two
substrates together. Preferably, the substrates are pressed and
held together for a time sufficient to form a secure bond. After
drying and just prior to contact bonding, the adhesive film layer
can, if desired, be further activated by heating to a temperature
above ambient temperature. Such an activation method may be
particularly desirable where the elastomeric polymer has a high
degree of crystallinity, as heating helps to reduce crystallinity
and provide the adhesive film with enhanced grab.
[0053] The adhesives of the present invention can, in at least
certain embodiments, also be used as wet bonding one-way adhesives,
where the adhesive is applied to the surface of only one substrate
before two substrates are joined together.
[0054] The film of adhesive on the substrate surface may be
continuous or discontinuous. The coating weight of adhesive used
will vary considerably depending upon the substrates as well as
other factors, but typically will be from about 1 to about 250
g/m.sup.2 or about 10 to about 125 g/m.sup.2.
[0055] Substrates capable of being bonded to each other using the
adhesives of the present invention include, but are not limited to,
plastic (including foamed plastics, solid plastics, thermoplastic
plastics, as well as thermoset plastics and both flexible and rigid
foams), wood (including consolidated or composite wood products
such as plywood and particle board), metal, rubbers (elastomers,
both thermoplastic as well as thermoset), glass, ceramics, paper
(& other cellulosic substrates), fabric (textiles, including
natural as well as synthetic textiles in woven or non-woven form),
plasterboard, fibers, leather, concrete, rock (e.g., marble or
granite), sheet rock, and the like. The substrates bonded to each
other may be the same as or different from each other. In certain
embodiments, at least one of the substrates that are bonded
together is relatively thin and flat; in such cases, the resulting
composite is often referred to in the art as a laminate or
laminated structure. For example, the present adhesives are useful
in laminating thin plastic laminates to the edges and or sides of
wood-containing substrates to provide components for countertops,
furniture, and the like. However, the adhesives of the present
invention can also be utilized to join together many other types of
substrates.
[0056] In one embodiment of the invention, the water-based adhesive
may be formulated to provide a fast-breaking adhesive for bonding
of porous substrates such as open-cell foams. In such a
formulation, the components are selected so that the aqueous
emulsion of the elastomeric adhesive polymer(s) is marginally
stable under storage conditions but breaks when subjected to high
shear (for example, when sprayed through the tip of a spray head).
Breaking of the emulsion prior to or when the adhesive is applied
to the porous substrate surface allows the water to be readily
absorbed into the porous substrate, leaving the elastomeric
adhesive polymer(s) on the porous substrate surface as a tacky
adhesive layer or coating. Such a product can be employed as either
a contact adhesive or as a wet bonding one-way adhesive on porous
substrates and is particularly suitable for use in bonding flexible
open-cell foams, such as polyurethane or natural rubber foams, in
furniture and bedding applications, for example. Two porous
substrates (for example, two flexible open-cell foam sheets) may be
readily joined to each other in this way. Other end-use
applications include, for example, foam to foam, foam to fabric,
foam to plastic, foam to wood, and foam to luan. Possible
advantages of using a fast-breaking adhesive of the type described
herein include better green strength (as demonstrated, for example,
by a foam fold test), improved spray characteristics, improved
rheology, density reduction, and softer bond lines. In such
fast-breaking adhesives, the use of mixtures of chloroprene
polymers and acrylic polymers (for example, an acrylic homopolymer
or polymer having a Tg greater than 0 degrees C., e.g., about 10 to
about 30 degrees C.) has been found to be advantageous. It may be
helpful to employ a surfactant stabilizer such as sodium lauryl
sulfate to achieve the desired stability characteristics in the
water-based adhesive, with such stabilizer preferably being added
to the adhesive before addition of the coated microspheres.
[0057] A fast-breaking adhesive in accordance with the present
invention may, for example, comprise water and:
TABLE-US-00002 Acrylic Homopolymer or Copolymer.sup.1 7.5-10 wt. %
Chloroprene Homopolymer or Copolymer.sup.1 30-35 wt. % Defoamer
0.001-1 wt. % Acid Acceptor 1-5 wt. % Acid (pH Adjusting Agent)
0.1-5 wt. % Plasticizer 0.5-5 wt. % Surfactant Stabilizer 0.001-1
wt. % Biocide/Preservative 0.001-1 wt. % Internal Coagulant 0.001-1
wt. % Thickener 0.001-2 wt. % Coated Microspheres 0.001-5 wt. %
.sup.1Added as emulsion in water (typically, ca. 40-60 wt. %
polymer; concentrations listed are based on dry weight of
polymer).
[0058] The water-based adhesive of the present invention may be
applied to a substrate surface using any suitable method, including
the methods conventionally used for water-based contact adhesives
including, but not limited to, spraying, brushing, troweling,
rolling, pouring, and the like. Spraying is a particularly
preferred application method; suitable spray-coating equipment
includes manual spray operators as well as automated spray
operators. It has been observed that the sprayed droplets of a
water-based adhesive in accordance with the present invention
typically dry much faster and bond at much lower pressure than
sprayed droplets of conventional contact adhesives. In one
embodiment, the application system used for the water-based
adhesive is a self-contained, portable, pressurized container,
wherein the adhesive is packaged together with a propellant in the
container under pressure. Preferably, the application system does
not include a flammable solvent or propellant, as such materials
will limit the ability to safely apply the adhesive within enclosed
spaces such as buildings. Non-flammable propellants thus are
preferably utilized. Suitable containers for such an application
system include, but are not limited to, aerosol cans, pressure
tanks, canisters, and the like (for example, the cylinders
conventionally utilized for propane or refrigerant storage).
Typically, such containers are fabricated of metal (e.g., steel or
aluminum) but relatively rigid plastics may also be used. The
materials of construction should be selected such that the portions
of the container in contact with the adhesive are
corrosion-resistant.
[0059] For example, the adhesive may be packaged in a cylinder
designed for containing pressure that includes a discharge valve
and a pressure hose attached to the cylinder by means of a threaded
opening in the valve. The other end of the pressure hose is
attached by means of a threaded fitting to a spray gun, which may
optionally have an extension wand attached. The pressure hose and
spray gun are configured to permit the adhesive to be applied to a
substrate surface in a suitable spray pattern. An internal dip tube
is provided within the cylinder that is attached to the discharge
valve and extends from the valve to a point near the bottom of the
cylinder. The dip tube has an inlet at the end near the cylinder
bottom that permits the adhesive to flow into the dip tube. To
operate the application system, the discharge valve is opened. The
adhesive, which is under pressure from the propellant within the
cylinder, is forced into the dip tube, through the discharge valve
and the pressure hose and out through the spray gun, or extension
wand if present. The spray gun may contain a trigger mechanism
that, when activated, opens a normally-closed valve and permits the
adhesive to be discharged from the application system.
* * * * *