U.S. patent application number 10/461954 was filed with the patent office on 2006-08-24 for aqueous polymeric composition containing polymeric nanoparticles and treatments prepared therefrom.
Invention is credited to David Richard Amick, Wayne Devonport, Catherine Ann Finegan, Joseph Michael Hoefler, Dennis Paul Lorah, Alvin Michael Maurice, Antony Keith Van Dyk.
Application Number | 20060189748 10/461954 |
Document ID | / |
Family ID | 36781717 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060189748 |
Kind Code |
A1 |
Amick; David Richard ; et
al. |
August 24, 2006 |
AQUEOUS POLYMERIC COMPOSITION CONTAINING POLYMERIC NANOPARTICLES
AND TREATMENTS PREPARED THEREFROM
Abstract
An aqueous polymeric composition containing select polymeric
nanoparticles is provided. The select polymeric nanoparticles
contain as polymerized units at least one multiethylenically
unsaturated monomer and at least one water soluble monomer; and
have a mean diameter in the range of from 1 to 50 nanometers. Also
provided are aqueous polymeric compositions that further contain
second particles such as pigment particles or second polymer
particles. The aqueous polymeric composition is useful for
preparing coatings having at least one improved property compared
to a coating absent the select polymeric nanoparticles. Further,
the aqueous polymeric composition is useful for treating wood. A
coating prepared from the aqueous polymeric composition is also
provided.
Inventors: |
Amick; David Richard;
(Doylestown, PA) ; Devonport; Wayne; (Doylestown,
PA) ; Van Dyk; Antony Keith; (Blue Bell, PA) ;
Finegan; Catherine Ann; (Warrington, PA) ; Hoefler;
Joseph Michael; (Bensalem, PA) ; Lorah; Dennis
Paul; (Lansdale, PA) ; Maurice; Alvin Michael;
(Lansdale, PA) |
Correspondence
Address: |
ROHM AND HAAS COMPANY;PATENT DEPARTMENT
100 INDEPENDENCE MALL WEST
PHILADELPHIA
PA
19106-2399
US
|
Family ID: |
36781717 |
Appl. No.: |
10/461954 |
Filed: |
June 13, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60389043 |
Jun 14, 2002 |
|
|
|
60414589 |
Sep 30, 2002 |
|
|
|
Current U.S.
Class: |
524/515 ;
524/502; 524/525; 524/556; 524/560 |
Current CPC
Class: |
C09D 133/02 20130101;
C08K 3/22 20130101 |
Class at
Publication: |
524/515 ;
524/556; 524/560; 524/525; 524/502 |
International
Class: |
C08K 5/00 20060101
C08K005/00 |
Claims
1. (canceled)
2. An aqueous polymeric composition comprising: (a) polymeric
nanoparticles, dispersed in an aqueous medium, said polymeric
nanoparticles comprising, as polymerized units: i) at least one
multiethylenically unsaturated monomer, and ii) at least one water
soluble monomer, said polymeric nanoparticles having a mean
diameter in the range of from 1 to 10 nanometers and a glass
transition temperature of at least 50.degree. C.; and (b) second
particles dispersed in said aqueous medium, said second particles
being selected from the group consisting of second polymer
particles and mixtures of second polymer particles and pigment
particles; said second polymer particles having a glass transition
temperature in the range of from -40.degree. C. to 70.degree. C.;
wherein a weight ratio of said polymeric nanoparticles to said
second polymer particles is in the range of from 1:99 to 1:1.
3. The aqueous polymeric composition according to claim 1 wherein:
said second particles include said second polymer particles; said
second polymer particles have a glass transition temperature of at
least 0.degree. C.; said polymeric nanoparticles have a glass
transition temperature of less than 50.degree. C.; and a weight
ratio of the said polymeric nanoparticles to said second polymer
particles is in the range of from 1:99 to 1:1.
4. The aqueous polymeric composition according to claim 2 wherein:
said polymeric nanoparticles have a first reactive group; and said
second polymer particles have a second reactive group capable of
reacting with said first reactive group of said polymeric
nanoparticles.
5. An aqueous polymeric composition comprising: (a) polymeric
nanoparticles, dispersed in an aqueous medium, said polymeric
nanoparticles comprising, as polymerized units: i) at least one
multiethylenically unsaturated monomer, and ii) at least one water
soluble monomer, said polymeric nanoparticles having a mean
diameter in the range of from 1 to 10 nanometers; and (b) second
particles dispersed in said aqueous medium, said second particles
being selected from the group consisting of second polymer
particles, pigment particles and mixtures thereof, said second
polymer particles having a glass transition temperature of at least
50.degree. C.; wherein a total volume concentration of said pigment
particles and said second polymer particles is at least 70%, based
on total solids volume of said aqueous polymeric composition.
6. The aqueous polymeric composition according to claim 2 wherein
said aqueous polymeric composition has a volatile organic compound
level of less than 150 grams per liter of said aqueous polymeric
composition.
7. (canceled)
8. (canceled)
9. A method for providing a coating, comprising the steps of: a)
applying onto a substrate, an aqueous polymeric composition
comprising polymeric nanoparticles, said polymeric nanoparticles
comprising as polymerized units: i) at least one multiethylenically
unsaturated monomer and ii) at least one water soluble monomer,
wherein said polymeric nanoparticles have a mean diameter in the
range of from 1 to 50 nanometers; and b) drying or allowing to dry
said aqueous polymeric composition applied to said substrate to
provide said coating.
10. A method for treating a porous substrate, comprising the steps
of: a) applying onto said porous substrate, an aqueous polymeric
composition comprising polymeric nanoparticles, said polymeric
nanoparticles comprising as polymerized units: i) at least one
multiethylenically unsaturated monomer, and ii) at least one water
soluble monomer, wherein said polymeric nanoparticles have a mean
diameter in the range of from 1 to 50 nanometers; b) allowing said
aqueous polymeric composition to penetrate into said porous
substrate; and c) drying or allowing to dry said aqueous polymeric
composition applied to said porous substrate to provide a treated
porous substrate.
11. The aqueous polymeric composition according to claim 5 wherein:
said second particles include said second polymer particles; said
polymeric nanoparticles have a first reactive group; and said
second polymer particles have a second reactive group capable of
reacting with said first reactive group of said polymeric
nanoparticles.
12. The aqueous polymeric composition according to claim 5 wherein
said aqueous polymeric composition has a volatile organic compound
level of less than 150 grams per liter of said aqueous polymeric
composition.
Description
[0001] The present invention relates to an aqueous polymeric
composition containing select polymeric nanoparticles. The present
invention also relates to aqueous polymeric compositions containing
a blend of select polymeric nanoparticles and second particles,
such as polymer particles or pigment particles. The aqueous
polymeric composition is useful for preparing coatings with
improved properties such as block resistance, print resistance, and
dirt pickup resistance. The aqueous polymeric composition is also
useful in providing compositions that have a low volatile organic
content. The present invention also relates to methods for using
the aqueous polymeric composition to prepare coatings and
penetrative treatments.
[0002] As used herein, "coatings" is used to refer to compositions
that are commonly identified as architectural coatings, such as,
for example, flat coatings, semigloss coatings, gloss coatings,
primers, topcoats, stain-blocking coatings, elastomeric coatings,
mastics, caulks, and sealants, as well as industrial coatings, such
as, for example, board and paneling coatings, transportation
coatings, furniture coatings, and coil coatings; maintenance
coatings such as, for example, bridge and tank coatings, and road
marking paints; inks; varnishes; leather coatings and treatments;
floor care coatings; paper coatings; personal care coatings such as
for hair, skin, and nails; and coatings for woven and nonwoven
fabrics, all of which are applied to a variety of substrates. Such
coatings are characterized by the formation of a substantially
continuous film on the surface of the substrate to which they are
applied, when in the dry state.
[0003] As used herein, "penetrative treatments" is used to refer to
substances which, when applied to certain substrates of a porous
nature, such as, for example, wood, penetrate into the pores of the
substrate rather than form a substantially continuous film on the
surface of the substrate.
[0004] Unless specifically indicated to the contrary, as used
herein, the term "treatments" is used to generally and broadly
refer to both coatings and penetrative treatments, as respectively
defined above.
[0005] There has long been and there is an ongoing need in the art
for aqueous polymeric compositions for preparing coatings having
certain desired properties in the dry state after application to a
substrate, that reflect an improvement in at least one purpose for
which the coating is applied, such as, for example, improving the
block resistance, print resistance, mar resistance, scrub
resistance, burnish resistance, dirt pickup resistance, adhesion,
gloss, flexibility, toughness, impact resistance, water resistance,
heat seal resistance, chemical resistance, and stain resistance of
the coated substrate. There has also been and there is an ongoing
need in the art for aqueous polymeric compositions for preparing
penetrative treatments for protecting certain substrate materials
of a porous nature, such as wood, and other natural and engineered
cellulosic based substrates.
[0006] The present invention is based on our discovery that the
incorporation of certain select polymeric nanoparticles into
aqueous based treatments greatly improves the properties of both
coatings and penetrative treatments.
[0007] Published PCT Patent Application WO 99/01522 discloses a
composition including a crosslinking agent and polymeric particles
having a mean particle diameter that is most preferably between
about 20 and about 40 nanometers, formed in the presence of the
reaction product of one or more carboxylic fatty acids and ammonia
or one or more polyfunctional aromatic or aliphatic amines, with
the dried composition providing a water resistant wood. The
compositions prepared according to the above are described both as
coatings and as being penetrative, although specific improvements
to any of the coating properties mentioned above are not disclosed
therein. Moreover, certain compositions according to this reference
have the disadvantage of involving the use of ammonia in their
preparation, which causes certain environmental and health and
safety concerns.
[0008] Accordingly, it is still desired to provide aqueous based
coating and penetrative treatment compositions which demonstrate at
least one improved property as described above, and which do not
involve the use of ammonia. It has now been found that such
improvements are provided by aqueous based treatments that include
an aqueous dispersion of polymeric particles having a mean diameter
of from 1 to 50 nanometers, the particles including, as polymerized
units, at least one multiethylenically unsaturated monomer and at
least one water soluble monomer.
[0009] Improvements in the aforementioned coating and penetrative
treatment properties are obtained in treatments according to the
present prepared from aqueous polymeric compositions including
select polymeric nanoparticles (PNPs). The select PNPs have a mean
diameter of from 1 to 50 nanometers (nm) and contain, as
polymerized units, at least one multiethylenically unsaturated
monomer and at least one water soluble monomer.
[0010] According to a first aspect of the present invention, an
aqueous polymeric composition includes PNPs dispersed in an aqueous
medium, the PNPs having, as polymerized units, at least one
multiethylenically unsaturated monomer and at least one water
soluble monomer, wherein the PNPs have a mean diameter in the range
of from 1 to 50 nm; and second particles, dispersed in the aqueous
medium, the second particles being selected from second polymer
particles, pigment particles, and mixtures thereof.
[0011] A second aspect of the present invention relates to a method
for providing an aqueous polymeric coating composition containing
PNPs, the PNPs having, as polymerized units, at least one
multiethylenically unsaturated monomer and at least one water
soluble monomer, and wherein the PNPs have a mean diameter in the
range of from 1 to 50 nm, the method including the steps of:
applying the coating onto a substrate and drying or allowing to dry
the aqueous polymeric PNP-containing composition to provide a dried
coating on the substrate.
[0012] A third aspect of the present invention provides a coating
containing PNPs having a mean diameter in the range of from 1 to 50
nm, the PNPs having, as polymerized units, at least one
multiethylenically unsaturated monomer and at least one water
soluble monomer.
[0013] A fourth aspect of the present invention provides a
penetrative treatment composition and method for treating a porous
substrate, such as wood, the method including the steps of applying
onto the porous substrate an aqueous polymeric composition
containing PNPs, the PNPs having, as polymerized units, at least
one multiethylenically unsaturated monomer and at least one water
soluble monomer, and wherein the PNPs have a mean diameter in the
range of from 1 to 50 nm; allowing the aqueous polymeric
composition to penetrate into the porous substrate; and drying or
allowing to dry the aqueous polymeric composition applied to the
porous substrate to provide a treated porous substrate.
[0014] The aqueous polymeric composition of the present invention
includes an aqueous dispersion of polymeric particles having a mean
diameter in the range of from 1 to 50 nm, the particles including,
as polymerized units, at least one multiethylenically unsaturated
monomer and at least one ethylenically unsaturated water soluble
monomer. As used herein, the term "dispersion" refers to a physical
state of matter that includes at least two distinct phases, wherein
a first phase is distributed in a second phase, with the second
phase being a continuous medium. The term "aqueous" is used herein
to refer to a medium that is from 50 to 100 weight % water, based
on the weight of the aqueous medium.
[0015] The PNPs of the present invention are addition polymers
which contain, as polymerized units, at least one
multiethylenically unsaturated monomer and at least one
ethylenically unsaturated water soluble monomer. Suitable
multiethylenically unsaturated monomers useful in the present
invention include di-, tri-, tetra-, and higher multifunctional
ethylenically unsaturated monomers, such as, for example, divinyl
benzene, trivinylbenzene, divinyltoluene, divinylpyridine,
divinylnaphthalene divinylxylene, ethyleneglycol di(meth)acrylate,
trimethylolpropane tri(meth)acrylate, diethyleneglycol divinyl
ether, trivinylcyclohexane, allyl(meth)acrylate, diethyleneglycol
di(meth)acrylate, propyleneglycol di(meth)acrylate,
2,2-dimethylpropane-1,3-di(meth)acrylate, 1,3-butylene glycol
di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol
di(meth)acrylate, tripropylene glycol di(meth)acrylate, triethylene
glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate,
polyethylene glycol di(meth)acrylates, such as polyethylene glycol
200 di(meth)acrylate and polyethylene glycol 600 di(meth)acrylate,
ethoxylated bisphenol A di(meth)acrylate, poly(butanediol)
di(meth)acrylate, pentaerythritol tri(meth)acrylate,
trimethylolpropane triethoxy tri(meth)acrylate, glyceryl propoxy
tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,
dipentaerythritol monohydroxypenta(meth)acrylate, divinyl silane,
trivinyl silane, dimethyl divinyl silane, divinyl methyl silane,
methyl trivinyl silane, diphenyl divinyl silane, divinyl phenyl
silane, trivinyl phenyl silane, divinyl methyl phenyl silane,
tetravinyl silane, dimethyl vinyl disiloxane, poly(methyl vinyl
siloxane), poly(vinyl hydro siloxane), poly(phenyl vinyl siloxane),
and mixtures thereof. As used herein, the term "(meth)acrylic"
includes both acrylic and methacrylic and the term "(meth)acrylate"
includes both acrylate and methacrylate. Likewise, the term
"(meth)acrylamide" refers to both acrylamide and methacrylamide.
"Alkyl" includes straight chain, branched and cyclic alkyl
groups.
[0016] Typically, the PNPs contain at least 1% by weight, based on
the weight of the PNPs, of at least one polymerized
multiethylenically unsaturated monomer. Up to and including 99.5
weight % polymerized multiethylenically unsaturated monomer, based
on the weight of the PNPs, is effectively used in the particles of
the present invention. It is preferred that the amount of
polymerized multiethylenically unsaturated monomer is from 1% to
80%, more preferably from 1% to 60%, and most preferably from 1% to
25%, by weight, based on the weight of the PNPs.
[0017] The PNPs further contain, as polymerized units, at least one
water soluble monomer. By "water soluble monomer" herein is meant a
monomer having a solubility in water of at least 7 weight %,
preferably at least 9 weight %, and most preferably at least 12
weight %, at a temperature of 25.degree. C. Data for the water
solubility of monomers is found, for example, in "Polymer Handbook"
(Second Edition, J. Brandrup, E. H. Immergut, Editors, John Wiley
& Sons, New York) and "Merck Index" (Eleventh Edition, Merck
& Co, Inc., Rahway, N.J.). Examples of water soluble monomers
include ethylenically unsaturated ionic monomers and ethylenically
unsaturated water soluble nonionic monomers. Typically, the amount
of the polymerized water soluble monomer is at least 0.5 weight %,
based on the weight of the PNPs. Up to and including 99 weight %
polymerized water soluble monomer, based on the weight of the PNPs,
is effectively used in the particles of the present invention.
[0018] Ethylenically unsaturated ionic monomer, referred to herein
as "ionic monomer", is a monomer that is capable of bearing an
ionic charge in the aqueous medium in which the PNPs are dispersed.
Suitable ionic monomers include, for example, acid-containing
monomers, base-containing monomers, amphoteric monomers;
quaternized nitrogen-containing monomers, and other monomers that
are subsequently formed into ionic monomers, such as monomers which
are neutralized by an acid-base reaction to form an ionic monomer.
Suitable acid groups include carboxylic acid groups and strong acid
groups, such as phosphorus containing acids and sulfur containing
acids. Suitable base groups include amines. It is preferred that
the amount of polymerized ionic monomer based on the weight of the
PNPs is in the range from 0.5 to 99 weight %, more preferably in
the range of from 1 to 50 weight %, even more preferably from 2 to
40 weight %, and most preferably from 3 to 25 weight %.
[0019] Suitable carboxylic acid-containing monomers include
carboxylic acid monomers, such as (meth)acrylic acid,
acryloxypropionic acid, and crotonic acid; dicarboxylic acid
monomers, such as itaconic acid, maleic acid, fumaric acid, and
citraconic acid; and monomers which are half esters of dicarboxylic
acids, such as monomers containing one carboxylic acid
functionality and one C.sub.1-6 ester. Preferred are acrylic acid
and methacrylic acid. Suitable strong acid monomers include sulfur
acid monomers, such as 2-acrylamido-2-methyl propane sulfonic acid,
styrene sulfonic acid, vinyl sulfonic acid,
sulfoethyl(meth)acrylate, sulfopropyl(meth)acrylate,
2-acrylamido-2-methyl propane sulfinic acid, styrene sulfinic acid,
and vinyl sulfinic acid; and phosphorus acid monomers, such as
2-phosphoethyl(meth)acrylate, vinyl phosphoric acid, and vinyl
phosphinic acid. Other acid monomers include terminally unsaturated
acid containing macromonomers, such as are disclosed in U.S. Pat.
No. 5,710,227. Phosphorus acid monomers are desirable as they
provide improved adhesion to certain substrates (e.g., metal).
[0020] Suitable base-containing monomers include monomers having
amine functionality, which includes
N,N-dimethylaminoethyl(meth)acrylate,
N,N-diethylaminoethyl(meth)acrylate,
N-t-butylaminoethyl(meth)acrylate,
N,N-dimethylaminopropyl(meth)acrylamide, p-aminostyrene,
N,N-cyclohexylallylamine, allylamine, diallylamine,
dimethylallylamine, N-ethyldimethylallylamine, crotyl amines, and
N-ethylmethallylamine; monomers having pyridine functionality,
which includes 2-vinylpyridine and 4-vinylpyridine; monomers having
piperidine functionality, such as vinylpiperidines; and monomers
having imidazole functionality, which includes vinyl imidazole.
Other suitable base-containing monomers include
oxazolidinylethyl(meth)acrylate, vinylbenzylamines,
vinylphenylamines, substituted diallylamines,
2-morpholinoethyl(meth)acrylate, methacrylamidopropyl trimethyl
ammonium chloride, diallyl dimethyl ammonium chloride, 2-trimethyl
ammonium ethyl methacrylic chloride, and the like.
[0021] Suitable amphoteric monomers include N-vinylimidazolium
sulfonate inner salts and
N,N-Dimethyl-N-(3-methacrylamidopropyl)-N-(3-sulfopropyl) ammonium
betaine.
[0022] Suitable functional monomers, in which the functionality is
subsequently formed into an acid or base include monomers
containing: an epoxide functionality, such as
glycidyl(meth)acrylate and allyl glycidyl ether; an anhydride, such
as maleic anhydride; an ester such as methyl acrylate; and a
halide. Suitable halide-containing functional monomers include
vinylaromatic halides and halo-alkyl(meth)acrylates. Suitable
vinylaromatic halides include vinylbenzyl chloride and vinylbenzyl
bromide. Other suitable functional monomers include allyl chloride,
allyl bromide, and (meth)acrylic acid chloride. Suitable
halo-alkyl(meth)acrylates include chloromethyl(meth)acrylate.
Suitable functional monomers, in which the functionality is
subsequently forming into a nonionic water soluble group include
vinyl acetate. Hydrolysis of the polymerized vinyl acetate provides
hydroxyl groups to the PNPs.
[0023] Multiethylenically unsaturated monomers that are also water
soluble monomers are alternatively used to prepare the PNPs. In
such embodiments, these monomers are classified for the purposes of
the present invention as both a multiethylenically unsaturated
monomer and a water soluble monomer. An example of a water soluble,
multiethylenically unsaturated monomer is phosphodi(ethyl
methacrylate).
[0024] Ethylenically unsaturated water soluble nonionic monomers
are referred to herein as "water soluble nonionic monomers".
Examples of water soluble nonionic monomers include
hydroxyalkyl(meth)acrylates, such as hydroxyethyl (meth)acrylate
and hydroxypropyl(meth)acrylate; poly(alkylene oxide) esters of
(meth)acrylic acid, such as poly(ethylene oxide).sub.20
methacrylate and poly(propylene oxide).sub.150 acrylate;
acrylamide; and methacrylamide. It is preferred that the amount of
polymerized water soluble nonionic monomer based on the weight of
the PNPs is in the range from 0.5 to 99 weight %, more preferably
in the range of from 20 to 90 weight %, even more preferably from
30 to 80 weight %, and most preferably from 40 to 70 weight %. When
the PNPs include, as polymerized units, ionic monomer and nonionic
water soluble monomer, lower levels of polymerized nonionic water
soluble monomer are preferred.
[0025] The PNPs optionally contain, as polymerized units, one or
more third monomers that are not multiethylenically unsaturated
monomers and are not water soluble monomers. Suitable third
monomers include C.sub.1-C.sub.24 alkyl(meth)acrylates, such as
methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate,
butyl(meth)acrylate, isobutyl(meth)acrylate, hexyl(meth)acrylate,
cyclohexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,
octyl(meth)acrylate, decyl(meth)acrylate, dodecyl(meth)acrylate,
pentadecyl(meth)acrylate, hexadecyl(meth)acrylate,
octadecyl(meth)acrylate, and nonadecyl(meth)acrylate, and mixtures
thereof. Other suitable third monomers include vinyl acetate; vinyl
versatate; diisobutylene; ureido containing monomers such as
N-(ethyleneureidoethyl)-4-pentenamide,
N-(ethylenethioureido-ethyl)-10-undecenamide, butyl
ethyleneureido-ethyl fumarate, methyl ethyleneureido-ethyl
fumarate, benzyl N-(ethyleneureido-ethyl) fumarate, and benzyl
N-(ethyleneureido-ethyl)maleamate; vinylaromatic monomers, such as
styrene, .alpha.-methylstyrene, vinyltoluene, p-methylstyrene,
ethylvinylbenzene, vinylnaphthalene, vinylxylenes, and nonylphenoxy
propenyl polyethoxylated alcohol. The vinylaromatic monomers also
include their corresponding substituted counterparts, such as
halogenated derivatives, i.e., containing one or more halogen
groups, such as fluorine, chlorine or bromine; and nitro, cyano,
(C.sub.1-C.sub.10)alkoxy, halo(C.sub.1-C.sub.10)alkyl,
(C.sub.1-C.sub.10)alkoxy, carboxy, and the like.
[0026] The PNPs have a mean diameter in the range of from 1 to 50
nm, preferably in the range of from 1 to 40 nm, more preferably
from 1 to 30 nm, even more preferably from 1 to 25 nm, even further
preferably from 1 to 20 nm, and most preferably from 1 to 10 nm. It
is further typical that the PNPs have a mean particle diameter of
at least 1.5 nm, preferably at least 2 nm. One method of
determining the particle sizes (mean particle diameter) of the PNPs
is by using standard dynamic light scattering techniques, wherein
the correlation functions are converted to hydrodynamic sizes using
LaPlace inversion methods, such as CONTIN.
[0027] Typically, PNPs including, as polymerized units, less than
10 weight % multiethylenically unsaturated monomer, have a glass
transition temperature from -90.degree. C. to 170.degree. C. for
the composition in the absence of the polymerized
multiethylenically unsaturated monomer, as determined by a
modulated differential scanning calorimetry (DSC) measurement. PNPs
containing, as polymerized units, at least 50 weight %
multiethylenically unsaturated monomer are considered to have glass
transition temperatures of at least 50.degree. C.
[0028] The PNPs of the present invention typically have an
"apparent weight average molecular weight" in the range of from
5,000 to 1,000,000, preferably in the range of from 10,000 to
500,000, and more preferably in the range of from 15,000 to
100,000. As used herein, "apparent weight average molecular weight"
reflects the size of the PNP particles using standard gel
permeation chromatography methods, e.g., using THF solvent at
40.degree. C., 3 Plgel.TM. Columns (Polymer Labs, Amherst, Mass.),
100 Angstrom (10 nm), 103 Angstroms (100 nm), 10.sup.4 Angstroms (1
micron), 30 cm long, 7.8 mm ID, 1 milliliter per minute, 100
microliter injection volume, calibrated to narrow polystyrene
standards using Polymer Labs CALIBRE.TM. software.
[0029] The PNPs are further characterizable as having suitable
hydrophilicities that allow the PNPs to be dispersed into an
aqueous medium. One method to characterize the hydrophilicity of
the PNPs is to calculate the Hansch parameter, which is actually a
measure of hydrophobicity. The Hansch parameter is calculated using
a group contribution method. The monomer units forming the polymer
are assigned a hydrophobicity contribution and the relative
hydrophobicity of the polymer is calculated based on the weight
average of the monomers in the polymer. Hansch and Fujita, J. Amer.
Chem. Soc., 86, 1616-1626 (1964); H. Kubinyi, Methods and
Principles of Medicinal Chemistry, Volume 1, R. Mannhold et al.,
Eds., VCH, Weinheim (1993); C. Hansch and A. Leo, Substituent
Constants for Correlation Analysis in Chemistry and Biology, Wiley,
New York (1979); and C. Hansch, P. Maloney, T. Fujita, and R. Muir,
Nature, 194. 178-180 (1962).
[0030] Values of the hydrophobicity contributions for several
monomers are listed in Table 1. TABLE-US-00001 TABLE 1 Monomer
Hydrophobicity Contribution ethyl acrylate 2.11 butyl acrylate 3.19
2-ethyl hexylacrylate 5.22 styrene 4.29 methyl methacrylate 1.89
ethyl methacrylate 2.43 butyl methacrylate 3.51 isobornyl
methacrylate 5.0 butadiene 4.0 acrylic acid -2.52 methacrylic acid
-2.2 maleic anhydride -3.5
Preferred PNPs have a Hansch parameter in the range of from -2.5 to
4, preferably from -1 to 3.
[0031] Certain embodiments of the PNPs further contain other
functional groups, which are provided by the polymerization of
monomers containing those groups or precursor groups thereof. One
method of attaching such other functional groups to the PNPs is by
reacting the ionic group of the PNP with a suitable compound. For
example, PNPs containing carboxylic acid groups are modified to
contain pendant hydrophilic groups by reacting carboxylic acid
groups with a suitable alcohol, such as a capped polyalkylene
oxide. Alternatively, functional groups are affixed to the PNPs
through non-radical reactions resulting in the formation of ionic
or covalent bonds between a modifying compound containing the
groups and complementary reactable groups covalently bound to the
PNP, such as is taught in U.S. Pat. No. 5,270,380.
[0032] The complementary reactable groups in the PNP and modifying
compound provide either ionic or covalent bonding, as appropriate
for each reactable group. Complementary ionic bonding includes
acid-base interaction and ion pair bonding of negatively and
positively charged atoms. Covalent bonding by complementary
reactable groups includes, for example: (a) acetoacetate-aldehyde;
(b) acetoacetate-amine; c) amine-aldehyde; (d) amine-anhydride; (e)
amine-isocyanate; (f) amine-epoxy; (g) aldehyde-hydrazide; (i)
acid-epoxy; j) acid-carbodiimide; (k) acid-chloro methyl ester; (O)
acid-chloro methyl amine; (m) acid-anhydride; (n) acid-aziridine;
(O) epoxy-mercaptan; and (p) isocyanate-alcohol. One of the first
and second reactable groups in each pair is present either in the
PNP or, alternatively, in the modifying compound.
[0033] A suitable method to prepare the aqueous polymeric
composition containing the PNPs dispersed in an aqueous medium
includes the steps of preparing a nonaqueous PNP dispersion
containing the PNPs dispersed in at least one solvent; and
combining the nonaqueous PNP dispersion with an aqueous medium. By
"nonaqueous" herein is meant a medium that contains from zero to
less than 50 weight % water, based on the weight of the nonaqueous
medium. Aqueous polymeric compositions containing PNPs that
include, as polymerized units, ionic monomers, are optionally
partially or completely neutralized prior to, during, or after
combining with the aqueous medium.
[0034] A suitable polymerization process to prepare the nonaqueous
PNP dispersion is free radical solution polymerization of at least
one multiethylenically unsaturated monomer, at least one water
soluble monomer, and, in certain embodiments, at least one third
monomer. As used herein, "solution polymerization" means free
radical addition polymerization in a suitable solvent for the
polymer. As used herein, "suitable solvent for the polymer" means
that linear random (co)-polymers having substantially similar
polymerized monomer units to the PNPs, are soluble in the solvent.
Another method for selecting a suitable solvent or mixture of
solvents is on the basis of using solubility parameter analysis.
According to such methods, the suitability of the solvent is
determined by substantially matching the solubility parameters of
the PNP and of the solvent, such as the Van Krevelen parameters of
delta d, delta p, delta h and delta v. See, for example, Van
Krevelen et al., Properties of Polymers. Their Estimation and
Correlation with Chemical Structure, Elsevier Scientific Publishing
Co., 1976; Olabisi et al., Polymer-Polymer Miscibility, Academic
Press, NY, 1979; Coleman et al., Specific Interactions and the
Miscibility of Polymer Blends, Technomic, 1991; and A. F. M.
Barton, CRC Handbook of Solubility Parameters and Other Cohesion
Parameters, 2.sup.nd Ed., CRC Press, 1991. Delta d is a measure of
dispersive interactions, delta p is a measure of polar
interactions, delta h is a measure of hydrogen bonding
interactions, and delta v is a measure of both dispersive and polar
interactions. Such solubility parameters are calculated by
alternative methods, such as by the group contribution method, and
by experimental determination, as is known in the art. A preferred
solvent has a delta v parameter within 5 (joule per cubic
centimeter).sup.1/2, preferably within 1 (Joule per cubic
centimeter).sup.1/2 of the polymer delta v parameter. Suitable
solvents for the polymerization include organic solvents, such as
hydrocarbons; alkanes; halohydrocarbons; chlorinated, fluorinated,
and brominated hydrocarbons; aromatic hydrocarbons; ethers;
ketones; esters; alcohols; and mixtures thereof. Particularly
suitable solvents, depending on the composition of the PNP, include
dodecane, mesitylene, xylenes, diphenyl ether, gamma-butyrolactone,
ethyl acetate, ethyl lactate, propyleneglycol monomethyl ether
acetate, caprolactone, 2-heptanone, methylisobutyl ketone, acetone,
methyl ethyl ketone, diisobutylketone, propyleneglycol monomethyl
ether, alkyl-alcohols, such as isopropanol, decanol, and t-butanol;
and supercritical carbon dioxide.
[0035] The nonaqueous PNP dispersion is prepared by first charging
a heel charge, containing solvent, or alternatively, a mixture of
solvent and some portion of the monomers, to a reaction vessel. The
monomer charge is typically composed of monomers, an initiator, and
a chain transfer agent. Typically, initiation temperatures are in
the range of from 55.degree. C. to 125.degree. C., although lower
or higher initiator temperatures are possible when using suitable
low temperature and high temperature initiators, respectively, as
is known in the art. After the heel charge has reached a
temperature sufficient to initiate polymerization, the monomer
charge or balance of the monomer charge is added to the reaction
vessel. The monomer charge time period is typically in the range of
from 15 minutes to 4 hours, although both shorter and longer time
periods are utilizable. During the monomer charge, the reaction
temperature is typically kept constant, although it is also
possible to vary the reaction temperature. After completing the
monomer mixture addition, additional initiator in solvent is
charged to the reaction and/or the reaction mixture is held for a
time.
[0036] Control of PNP particle size and distribution is achieved by
choice and control of one or more parameters such as solvent,
initiator, total solids level, initiator level, type and amount of
multi-functional monomer, type and amount of ionic monomer, type
and amount of chain transfer agent, and reaction conditions.
[0037] Initiators useful in the free radical polymerization of the
present invention include, for example, one or more of
peroxyesters, alkylhydroperoxides, dialkylperoxides, azoinitiators,
persulfates, redox initiators and the like. The amount of the free
radical initiator used is typically from 0.05 to 10% by weight,
based on the weight of total monomer. According to certain
embodiments, chain transfer reagents are used to control the extent
of polymerization of the PNPs useful in the present invention.
Suitable chain transfer agents include, for example: alkyl
mercaptans, such as dodecyl mercaptan; aromatic hydrocarbons with
activated hydrogens, such as toluene; and alkyl halides, such as
bromotrichloroethane.
[0038] In one method of preparing the aqueous polymeric composition
of the present invention, at least a portion of the polymerized
ionic monomer units of the PNPs is neutralized with at least one
neutralizing agent to form an at least partially neutralized
nonaqueous PNP dispersion. The polymerized ionic monomer units of
the PNPs are neutralized in a variety of ways. When the polymerized
ionic monomer units are acidic, the neutralizing agent is typically
a base. Likewise, when the polymerized ionic monomer units are
basic, the neutralizing agent is typically an acid. Suitable bases
include inorganic and organic bases. Suitable inorganic bases
include the full range of the hydroxide, carbonate, bicarbonate,
and acetate bases of alkali or alkaline metals. Suitable organic
bases include ammonia, primary/secondary/tertiary amines, diamines,
and triamines. Preferred basic neutralizing agents include sodium
hydroxide, and ammonium hydroxide. Suitable acids include
carboxylic acids, such as acetic acid; dicarboxylic acids;
(di)carboxylic/hydroxyl acids; aromatic acids, such as benzoic
acid; and a variety of other acids, such as boric, carbonic,
citric, iodic, nitrous, nitric, periodic, phosphoric, phosphorous,
sulfuric, sulfurous, and hydrochloric acid. None of the foregoing
categories of bases and acids are deemed to be limiting.
[0039] The amount of neutralizing agent required to neutralize the
nonaqueous PNP dispersion is typically determined on a molar basis
of neutralizing agent to polymerized ionic monomer units of the
PNPs. Without being bound to a particular theory, the amount of
polymerized ionic monomer units (i.e., level of charge) needed to
stabilize the PNPs (i.e., maintain particle size during conversion
from non-aqueous to aqueous medium) varies as PNP composition and
properties are varied. It is believed that the PNP hydrophobicity,
Tg, crosslinking level, and type of counter-ion from the
neutralizing agent are important variables. For providing stable
aqueous PNP dispersions (i.e., wherein flocculation of the PNPs is
minimized), the polymerized ionic monomer units are preferably at
least 20%, more preferably at least 50%, even more preferably at
least 80%, and most preferably at least 90% neutralized.
[0040] Neutralizing the PNPs is alternatively carried out in a
variety of ways. In one method, the nonaqueous PNP dispersion is
added to a solution containing the neutralizing agent while
stirring. Preferably, the neutralizing agent is added as an aqueous
solution over time while stirring the nonaqueous PNP dispersion to
provide an at least partially neutralized nonaqueous PNP
dispersion.
[0041] In one method of preparing the aqueous polymeric composition
containing dispersed PNPs, the at least partially neutralized
nonaqueous PNP dispersion is combined with an aqueous medium. The
aqueous medium optionally contains the neutralizing agent(s) for
neutralizing the PNPs, in which case the nonaqueous PNP dispersion
is capable of being simultaneously neutralized and combined with an
aqueous medium. The aqueous medium optionally contains surfactants,
which are capable of altering the stability of the PNPs, or of
altering other properties of the resulting aqueous PNP dispersion,
such as its surface tension.
[0042] The sequence of admixing the partially neutralized
nonaqueous PNP dispersion and the aqueous medium is not critical.
Various methods and equipment, which are suitable for mixing are
described in The Chemical Engineer's Handbook, 5.sup.th Edition,
Perry and Chilton, Eds., McGraw-Hill, Ch. 21, 1973. Typically, the
aqueous medium is continuously stirred while adding the partially
neutralized nonaqueous PNP dispersion to it in order to ensure that
the solvent is intimately mixed with the aqueous medium, which
minimizes flocculation of the PNPs.
[0043] Suitable weight percentages of the PNPs in the aqueous
polymeric composition, based on total weight of the aqueous
polymeric composition, are typically from 1 to 90 weight %, more
typically from 2 to 75 weight %, even more typically from 4 to 65
weight %, further more typically from 8 to 55 weight %, and most
typically from 10 to 45 weight %.
[0044] While the preparation of the aqueous polymeric composition
of the present invention does not require the use of surfactants,
and it is typical that the nonaqueous PNP dispersions are
substantially free of surfactants, surfactants are included in
certain embodiments. When present, the amount of surfactants is
typically less than 3 weight percent, more typically less than 2
weight percent, even more typically less than 1 weight percent,
further typically less than 0.5 weight percent, and even further
typically less than 0.2 weight percent, based on total weight of
the PNPs.
[0045] The aqueous polymeric composition is optionally treated to
remove at least a portion of the solvent, and in certain
embodiments, also water, to increase the solids content of the
PNPs. Suitable methods to concentrate the PNPs include distillation
processes, such as forming azeotropes of water and a suitable
solvent; evaporation of solvent or water; drying the aqueous
polymeric composition by freeze drying or spray drying; solvent
extraction techniques; and ultrafiltration techniques. Preferably
at least 25 weight %, more preferably at least 50 weight %, even
more preferably at least 75 weight %, and most preferably 100
weight % of the solvent is exchanged with water. Removal of the
solvent is preferably carried out under conditions that minimize
destabilization (i.e., flocculation) of the PNPs.
[0046] In an alternative method, the aqueous polymeric composition
of this invention is prepared by a method including the steps of
preparing a nonaqueous PNP dispersion containing the PNPs dispersed
in at least one solvent that is both a suitable solvent for the
PNPs and is compatible or miscible in water; and combining the
nonaqueous PNP dispersion with an aqueous medium. Examples of such
suitable solvents for acrylic-containing PNPs, which are also
compatible or miscible with water, include isopropanol and ether
alcohols (e.g., monobutyl ether of ethylene glycol and monoethyl
ether of diethylene glycol). In this method, the PNPs do not
require the addition of neutralizing agents to impart particle
stability when combined with water.
[0047] Alternative embodiments of the aqueous polymeric
compositions of the present invention have a wide range of PNP
content. Typically, the PNP weight fractions range from 0.1 to 99
weight %, more typically from 1 to 90 weight %, even more typically
from 2 to 75 weight %, further typically from 5 to 50 weight %, and
most typically from 10 to 40 weight %, based on the weight of the
aqueous polymeric composition.
[0048] The PNPs are present in the aqueous polymeric composition at
a level of from 0.1 to 100 weight % PNPs, based on the total weight
of the polymer particles in the aqueous polymeric composition. The
functional role of the PNPs determines the level of PNPs present.
Some of the functional roles of the PNPs are, for example, as
additives, as co-binders, as principal binders, and as sole
binders. A lower level of PNPs is utilized when the PNPs function
as additives and co-binders, while a higher level of PNPs is
utilized when the PNPs function as principal binders or sole
binders.
[0049] Certain embodiments of the aqueous polymeric compositions of
the present invention further contain second particles that are not
PNPs, and are second polymer particles, such as emulsion polymer
particles, having a mean particle diameter of greater than 50 nm,
or are pigment particles.
[0050] In one embodiment, the second polymer particles are prepared
in the presence of the PNPs. In this embodiment, the PNPs are
present in the aqueous polymeric composition at a level of from 1
to 99 weight %, preferably from 5 to 90 weight %, more preferably
from 10 to 60 weight %, and most preferably from 20 to 60 weight %,
based on the total weight of polymer in the aqueous polymeric
composition.
[0051] The glass transition temperatures of the second polymer
particles are typically in the range of from -60.degree. C. to
120.degree. C., depending upon the intended application of the
aqueous polymeric composition containing the second polymer
particles. Further, the second polymer particles typically have a
mean diameter in the range of from greater than 50 nm up to 2
microns, preferably in the range of from 80 nm to 500 nm, and more
preferably, in the range of from 100 nm to 350 nm. The second
polymer particles are commonly supplied as aqueous dispersions.
[0052] Examples of second polymer particles include polymer
particles prepared by emulsion polymerization and include
crosslinked and uncrosslinked polymer particles, polymer particles
containing two or more polymer phases such as core-shell polymer
particles, and polymer particles having one or more voids and
vesiculated polymer particles as disclosed in U.S. Pat. No.
4,427,835; U.S. Pat. No. 4,920,160; U.S. Pat. No. 4,594,363; U.S.
Pat. No. 4,469,825; U.S. Pat. No. 4,468,498; U.S. Pat. No.
4,880,842; U.S. Pat. No. 4,985,064; U.S. Pat. No. 5,157,084; U.S.
Pat. No. 5,041,464; U.S. Pat. No. 5,036,109; U.S. Pat. No.
5,409,776; and U.S. Pat. No. 5,510,422.
[0053] Specific examples of second polymer particles are acrylic
copolymers, vinyl acetate copolymers, vinyl/acrylic copolymers,
styrene/acrylic copolymers, polyurethanes, polyvinyl chlorides,
ethylene/vinyl acetate copolymers, styrene/butadiene polymers, and
mixtures thereof.
[0054] Alternatively, the second particles are pigment particles.
As used herein, pigment particles include inorganic particles such
as pigments, extenders, or fillers; and organic colored pigments.
Examples of pigment particles include zinc oxide, antimony oxide,
zirconium oxide, chromium oxide, iron oxide, lead oxide, zinc
sulfide, lithopone, titanium dioxide including anatase and rutile
titanium dioxide, calcium carbonate, calcium sulfate, barium
sulfate, mica, clay including delaminated clay, calcined clay,
feldspar, nepheline syenite, bismuth vanadate; titanium nickel
antimony oxide, cobalt oxides, wollastonite, diatomaceous earth,
alumina silicates, carbon black, aluminum oxide, silica, talc, and
mixtures thereof. The mean diameter of the pigment particles is
typically in the range of from 5 nm to greater than 100 microns,
preferably in the range of from 20 nm to 20 microns, and more
preferably, in the range of from 50 nm to 10 microns.
[0055] The aqueous polymeric composition containing PNPs according
to the present invention is useful for treating porous materials
including wood substrates. Wood substrates are characterized as
having a surface containing pores as well as an internal porous
structure. The PNPs enter into the wood pores and penetrate into
the wood substrate. A method of treating the wood substrate
includes the steps of applying the aqueous polymeric composition of
this invention, which contains PNPs, onto a wood substrate;
allowing the aqueous polymeric composition to penetrate or to be
absorbed into the wood substrate; and drying or allowing to dry the
applied aqueous polymeric composition. According to certain
embodiments of the method, pressure is also applied to increase the
penetration of the PNPs into the wood substrate. Treatment of the
wood substrate with the aqueous polymeric composition provides
increased protection against weathering caused by conditions such
as exposure to moisture or sunlight. Treatment of the wood
substrate with the aqueous polymeric composition also improves the
aesthetic appearance of the wood substrate. Wood substrates which
are capable of being so treated include timber such as, for
example, cedar, pine, spruce, fir, redwood, hemlock, teak, oak,
cherry, poplar, maple, and walnut; and processed timber, such as
including, but not limited to, medium density fiber board, chip
board, and laminates such as plywood.
[0056] According to certain embodiments, the aqueous polymeric
composition useful for treating wood substrates is provided as a
blend further containing second polymer particles. Without wishing
to be limited to a particular theory, the larger second polymer
particles are believed to remain at or near the surface of the wood
substrate, and to provide protection to the wood substrate surface.
Preferably, these second polymer particles have a mean particle
diameter in the range of from greater than 50 nm to 500 nm; and
they have a glass transition temperature in the range of from
0.degree. C. to 50.degree. C.
[0057] A volatile organic compound ("VOC") is defined herein as a
carbon containing compound that has a boiling point below
280.degree. C. at atmospheric pressure. Compounds such as water and
ammonia are excluded from the definition of VOC. The VOC level of a
composition is the total amount of one or more volatile organic
compounds contained in the composition.
[0058] Frequently a VOC is deliberately added to a paint or a
coating composition to improve film formation of the resulting
coating or to aid in the application properties of the composition
employed to prepare the coating. Examples of VOCs are glycol
ethers, organic esters, aromatic compounds, ethylene and propylene
glycols, and aliphatic hydrocarbons. Additionally, methods of paint
or coating composition preparation frequently introduce
adventitious VOCs from various ingredients such as the aqueous
dispersion containing the PNPs, and from an optional component such
as the aqueous dispersion containing second particles, biocides,
soaps, dispersants, and thickeners. These typically account for
less than 20 grams (g) VOC per liter of the aqueous polymeric
composition. Steam stripping and choice of low VOC containing
additives for those additives such as biocides, defoamers, soaps,
dispersants, and thickeners, are some alternative methods commonly
used to further reduce VOC content of the aqueous polymeric
composition to less than 5 g VOC per liter of the aqueous polymeric
composition.
[0059] Preferably, the aqueous polymeric composition of this
invention is a low VOC composition having a VOC level of less than
150 grams per liter (g/liter) of the aqueous polymeric composition;
more preferably the aqueous polymeric composition has a VOC level
of less than 100 g/liter of the aqueous polymeric composition; and
even more preferably the aqueous polymeric composition has a VOC
level of less than 50 g/liter of the aqueous polymeric
composition.
[0060] In certain embodiments, the aqueous polymeric composition
contains hard PNPs having a glass transition temperature of at
least 50.degree. C. and soft second polymer particles having a
glass transition temperature in the range of from -40.degree. C. to
70.degree. C. In dried coatings prepared from the aqueous polymeric
composition of such embodiments, the hard PNPs provide one or more
improved film properties, such as increased resistance to wear,
improved block resistance, improved tint retention, increased
elongation of the coating, improved impact resistance, improved
adhesion, improved corrosion resistance, improved gloss retention
and improved dirt pickup resistance, as compared to a comparative
dried coating without the hard PNPs. In this embodiment, the ratio
of the weight of the hard PNPs to the weight of the soft second
polymer particles is in the range of from 1:99 to 1:1, preferably
in the range of from 1:50 to 1:3, and most preferably in the range
of from 1:20 to 1:4. Certain embodiments of the aqueous polymeric
composition containing the hard PNPs and the soft second polymer
particles are provided as a low VOC composition. Preferably, in
such low VOC embodiments of the hard PNP-containing composition,
the ratio of the weight of the PNPs to the weight of the second
polymer particles is in the range of from 1:20 to 1:3 and more
preferably in the range of from 1:9 to 1:5. Further, it is
preferred that the hard PNPs have a glass transition temperature in
the range of 50.degree. C. to 100.degree. C., and preferably in the
range of from 60.degree. C. to 80.degree. C. A preferred range for
the glass transition temperature of soft second polymer particle in
the low VOC, hard PNP-containing compositions is from 0.degree. C.
to 15.degree. C.
[0061] In certain embodiments, the aqueous polymeric composition
contains PNPs having first reactive groups. In such embodiments,
the first reactive groups are self reactive to form chemical bonds.
An example of PNPs having self reactive groups is PNPs containing,
as polymerized units, methylol acrylamide.
[0062] In certain other embodiments, the aqueous polymeric
composition contains second polymer particles having second
reactive groups. In this embodiment, the second reactive groups are
self reactive to form chemical bonds. An example of second polymer
particles having self reactive groups is second polymer particles
containing, as polymerized units, methylol (meth)acrylamide.
[0063] In still certain other embodiments, the aqueous polymeric
composition contains PNPs having first reactive groups and second
polymer particles having second reactive groups, wherein the first
reactive groups and the second reactive groups are co-reactive to
form chemical bonds. In this embodiment, the aqueous polymeric
composition is applied onto a substrate; dried or allowed to dry;
and the first reactive groups and the second reactive groups are
reacted or allowed to react to form a dried crosslinked coating.
Examples of complementary pairs of first and second reactive groups
include, for example, isocyanates and isothiocyanates, which react
with reactive groups selected from alcohols, amines, ureas,
anhydrides, and mixtures thereof; aldehyde groups, which react with
reactive groups selected from acetoacetoxy groups, amine groups,
and mixtures thereof; acetoacetoxy groups, which react with
reactive groups selected from aldehyde groups, amine groups, and
mixtures thereof; epoxides, thioranes, and aziridines, all three of
which react with reactive groups selected from alcohol groups,
carboxylic acid groups, anhydride groups, amine groups, mercaptan
groups, and mixtures thereof; carbodiimides, which react with
reactive groups selected from carboxylic acid groups, phosphorus
acid groups, alcohol groups, amine groups, mercaptan groups, and
mixtures thereof; haloalkane and halomethylphenyl groups, both of
which react with reactive groups selected from amine groups,
carboxylic acid groups, and mixtures thereof; amines and thiols,
both of which react with reactive groups selected from epoxide
groups, aziridine groups, thiorane groups, acetoacetoxy groups,
isocyanate groups, isothiocyanate groups, carbodiimide groupd, and
mixtures thereof; and carboxylic acids, which react with reactive
groups selected from epoxide groups, aziridine groups, thiorane
groups, carbodiimide groups, and mixtures thereof. Alternatively,
the first reactive groups and the second reactive groups are the
same reactive functionality and are self reactive. Examples of
suitable chemical bonds between the PNPs and the second polymer
particles include the following types of linkages: esters, amides,
ethers, urethanes, thiol ethers, amines, and ureidos. In certain
embodiments, the reaction between the first reactive group and the
second reactive group occurs during the drying step. Alternatively,
in other embodiments, drying occurs any time prior to film
formation, provided that the extent of reaction does not materially
impair film formation. According to certain embodiments, the
reaction of the first reactive group and the second reactive group
is conducted in the presence of one or more catalysts.
Alternatively, no catalyst is used. Techniques to determine the
extent of reaction of the first reactive group and the second
reactive group include infrared spectroscopy, nuclear magnetic
resonance spectroscopy, and ultraviolet-visible spectroscopy.
[0064] One method to prepare the PNP containing the first reactive
group is an addition polymerization process that includes
polymerization of at least one monomer containing a select reactive
group, wherein the select reactive group is the first reactive
group. Examples of monomers containing a select reactive group
include ionic monomers, and isocyanate monomers, such as isocyanato
ethyl methacrylate, dimethyl meta-isopropenyl benzyl isocyanate;
acetoacetoxy monomers, such as acetoacetoxy ethyl(meth)acrylate;
aldehyde monomers, such as acrolein and methacrolein; amine
monomers, such as t-butyl aminoethyl(meth)acrylate, dimethyl
aminoethyl(meth)acrylate, aminobutyl(meth)acrylate,
aminoethyl(meth)acrylate; aminopropyl(meth)acrylate; and
oxazolidinoethyl(meth)acrylate; epoxy monomers, such as
glycidyl(meth)acrylate; carboxylic acid monomers, such as
(meth)acrylic acid, itaconic acid, fumaric acid, maleic acid,
.alpha.-acryloxypropionic acid, ethacrylic acid,
.alpha.-chloroacrylic acid, .alpha.-vinylacrylic acid, crotonic
acid, .alpha.-phenylacrylic acid, cinnamic acid, chlorocinnamic
acid, and .beta.-styrylacrylic acid; hydroxy containing monomers,
such as hydroxyalkyl(meth)acrylates including
2-hydroxyethyl(meth)acrylate and 3-hydroxypropyl(meth)acrylate;
halogenated monomers, such as bromopropyl(meth)acrylate; and
halomethyl-styrene. A suitable process to prepare the second
polymer particles having at least one second reactive group is
addition polymerization of at least one monomer having a select
reactive group, wherein the select reactive group is the second
reactive group. Alternatively, either the first reactive group or
the second reactive group is generated by functionalization of a
precursor group after polymerization of the PNPs or the second
polymer particle, respectively. Second polymer particles suitable
for use in the present embodiment include particles having a single
polymer phase and particles having two or more polymer phases, such
as core-shell particles, acorn particles having an outer polymer
phase partially encapsulating a core polymer phase, and particles
having one polymer phase forming multiple domains on or within a
second polymer phase.
[0065] In yet other embodiments, the aqueous polymeric composition
contains PNPs having first reactive groups and second polymer
particles having second reactive groups, wherein the PNPs have a
lower glass transition temperature than the second polymer
particles. While not wanting to be bound by a particular theory, it
is believed that the low T.sub.g PNPs aid in the film formation of
the second polymer particles and allow the aqueous polymeric
composition to form a film with a lower amount of coalescent than a
film formed from the second polymer particles in the absence of the
PNPs. After film formation, the first and second reactive groups
react to form crosslinks to provide the film with improved
properties than a film absent the crosslinks. Preferably, the PNPs
have a T.sub.g in the range of from -10.degree. C. to 15.degree.
C., and more preferably in the range of from 0.degree. C. to
5.degree. C. Preferably, the second polymer particles having second
reactive groups have a T.sub.g in the range of from 5.degree. C. to
35.degree. C., and more preferably in the range of from 15.degree.
C. to 25.degree. C. The ratio of the weight of PNPs having first
reactive group to the weight of second polymer particles having
second reactive groups is in the range of from 1:100 to 1:3,
preferably in the range of from 1:25 to 1:4; and more preferably,
in the range of from 1:20 to 1:5. Certain embodiments of such
aqueous polymeric compositions containing PNPs having first
reactive groups and second polymer particles having second reactive
groups, wherein the PNPs have a lower glass transition temperature
than the second polymer particles, are provided as low VOC
compositions.
[0066] In yet still other certain embodiments of the present
invention, the aqueous polymeric composition contains a ternary
mixture of polymer particles having select particle sizes. The
ternary mixture includes: a small mode of PNPs having a mean
particle diameter in the range of from 10 nm to 20 nm; a medium
mode of polymer particles having a mean particle diameter in the
range of from 30 nm to 70 nm; and a large mode of second polymer
particles having a mean particle diameter in the range of from 100
nm to 200 nm. Suitable medium mode polymer particles are PNPs
having a mean diameter in the range of from 30 nm to 50 nm, second
polymer particles having a mean diameter in the range of greater
than 50 nm to 70 nm, and mixtures thereof. Preferably, the ternary
mixture has a small mode of PNPs with a T.sub.g in the range of
from -10.degree. C. to 5.degree. C., and more preferably in the
range of from -5.degree. C. to 0.degree. C. Preferably the ternary
mixture has a medium mode of PNPs with a T.sub.g in the range of
from 0.degree. C. to 15.degree. C., and more preferably in the
range of from 5.degree. C. to 12.degree. C. Preferably the ternary
mixture has a large mode of second polymer particles with a T.sub.g
in the range of from 5.degree. C. to 20.degree. C., and more
preferably in the range of from 10.degree. C. to 15.degree. C. The
aqueous polymeric composition containing the ternary mixture of
polymer particles is useful for preparing coatings having a balance
of good film formation and acceptable film properties such as
hardness, dirt pickup resistance, scrub resistance, block
resistance, or gloss. Certain embodiments of aqueous polymeric
compositions contains a ternary mixture of polymer particles having
select particle sizes are provided as a low VOC composition.
[0067] The total amount of pigment and second polymer particles
having a T.sub.g of at least 50.degree. C. in the aqueous polymeric
composition is defined according to the volume concentration of
these components in the dried coating formed from the aqueous
polymeric composition or equivalently, by the volume concentration
of these components based on the total volume of solids in the
aqueous polymeric composition. The percent total volume
concentration of the pigment and second polymer particles having a
T.sub.g of at least 50.degree. C., referred to herein as the
"pigment volume concentration" or "PVC" is calculated by the
following formula: PVC(%)=100.times.[V.sub.1+V.sub.2]/V.sub.T
wherein V.sub.1 is the volume of the pigment(s), V.sub.2 is the
volume of second polymer particles with a T.sub.g of at least
50.degree. C., and V.sub.T is the volume solids of the aqueous
polymeric composition. The aqueous polymeric composition of this
invention includes compositions having pigment volume
concentrations in the range of from 0 to 95% and thereby
encompasses coating compositions sometimes described in the art as
clear coatings, stains, flat coatings, satin coatings, semi-gloss
coatings, gloss coatings, primers, textured coatings, paper
coatings, and the like.
[0068] One method to prepare the aqueous polymeric composition of
this invention, which contains pigment particles, is by admixing
the aqueous polymeric composition containing the PNPs and an
aqueous slurry containing dispersed pigment particles. Mixing is
typically employed to minimize localized concentrations of either
the PNPs or the pigment particles. Alternatively, the pigmented
aqueous polymeric composition of this invention is prepared by
admixing dry pigment particles into the aqueous polymeric
composition containing PNPs to disperse the pigment particles into
the aqueous medium. Typically, high shear mixing is employed to
disperse the dried pigment particles. In certain embodiments,
dispersants are added to aid in dispersing or stabilizing the
pigment particles in the aqueous medium of the aqueous polymeric
composition.
[0069] In certain other embodiments, the aqueous polymeric
composition of this invention further contains one of pigment
particles, second polymer particles having a T.sub.g of at least
50.degree. C., and mixtures thereof. This aqueous polymeric
composition has a PVC of at least 70%, preferably of at least 75%,
and more preferably at least 80%. The aqueous polymeric composition
of this embodiment is useful as a coating composition suitable for
preparing opaque dried coatings, such as a dried flat paint or a
dried paper coating. The PNPs contained in this aqueous polymeric
composition have a T.sub.g in the range of from -20.degree. C. to
40.degree. C., preferably in the range of from -10.degree. C. to
30.degree. C., and more preferably in the range of from -5.degree.
C. to 25.degree. C. The aqueous polymeric composition of this
embodiment, which is suitable as a paint or a paper coating
composition, typically contains one or more of titanium dioxide,
calcium carbonate, and clay, as the pigment particle. Certain other
embodiments also still further contain solid bead polymer particles
or polymer particles having one or more voids, as the second
polymer particles, with a T.sub.g of at least 50.degree. C.
[0070] In yet still certain other embodiments, the aqueous
polymeric composition contains PNPs and second polymer particles,
wherein the second polymer particles are prepared in the presence
of the PNPs. In this embodiment, the PNPs are present in the
aqueous polymeric composition at a level of from 1 to 99 weight %,
preferably from 5 to 90 weight %, more preferably from 10 to 60
weight %, and most preferably from 20 to 60 weight %, based on the
total weight of polymer in the aqueous polymeric composition.
Preferably, the second polymer particles are polymerized by aqueous
emulsion polymerization. In this process, the PNPs are added to an
aqueous reaction medium prior to or during the polymerization of
the second polymer particles. The PNPs of the present embodiment
are believed to act as stabilizers (i.e., dispersants) in the
aqueous emulsion polymerization process, such as according to
methods which use "high acid" polymeric stabilizers (often referred
to as "resin supported emulsion polymerization", see for example
U.S. Pat. No. 4,845,149 and U.S. Pat. No. 6,020,061). Among
suitable emulsion polymer compositions, any emulsion polymer,
copolymer, multi-stage copolymer, interpolymer, core-shell polymer,
and the like can be stabilized using the PNPs of the present
invention. Preferred second polymer particles include, as
polymerized units, at least one (meth)acrylic ester monomer.
[0071] According to certain embodiments, the emulsion
polymerization process performed in the presence of the PNPs,
further includes synthesis adjuvants, such as surfactants,
initiators, and buffers. The resulting aqueous polymeric
composition prepared by this process contains PNPs on the second
polymer particle surface as well as PNPs dispersed in the aqueous
phase. The aqueous polymeric composition of this embodiment is
useful for preparing coatings having improved properties, such as,
gloss. Also, the aqueous polymeric composition containing such PNP
stabilized second polymer particles, displays enhanced colloidal
stability relative to analogous blends of PNPs and second polymer
particles that are prepared in the absence of PNPs.
[0072] One aspect of the present invention is directed towards a
method of preparing a coating from the aqueous polymeric
composition containing the PNPs. The method includes the steps of
applying the aqueous polymeric composition onto a substrate; and
drying or allowing to dry the applied aqueous polymeric composition
to provide the coating. The aqueous polymeric composition is
typically applied onto a substrate to prepare a dry coating.
Suitable techniques for applying the aqueous polymeric composition
onto a substrate include brushing, rolling, drawdown, dipping, with
a knife or trowel, curtain coating, and spraying methods such as,
for example, air-atomized spray, air-assisted spray, airless spray,
high volume low pressure spray, and air-assisted airless spray. The
wet coating thickness of the applied aqueous polymeric composition
is commonly in the range of 1 micron to 5 millimeters. The aqueous
polymeric composition is applied onto a substrate as a single coat
and alternatively multiple coats. The applied aqueous polymeric
composition is typically allowed to dry at ambient conditions and
alternatively dried by the application of heat to provide a dry
coating. Drying is typically allowed to proceed under ambient
conditions such as, for example, at 0.degree. C. to 35.degree. C.
The method is useful for providing coatings that have at least one
improved property compared to a comparative coating prepared in the
absence of the PNPs. Examples of improved properties include block
resistance, print resistance, mar resistance, scrub resistance,
abrasion resistance, burnish resistance, dirt pickup resistance,
adhesion, gloss, flexibility, toughness, impact resistance, reduced
coalescent demand, water resistance, chemical resistance,
biological fouling resistance, and stain resistance.
[0073] In a pigmented coating, pigment particles are dispersed
within a polymeric film to provide opacity or hiding. The opacity
of the pigmented coating arises from the scattering of light, which
results from differences in the refractive indices of the polymeric
film and the pigment particles contained within. The pigment
particles typically have a refractive index of 1.8 or greater.
Refractive indices for polymers are typically in the range of 1.4
to 1.6. In one embodiment, the improved coating is a pigmented
coating that is prepared from an aqueous polymeric composition
containing PNPs, second polymer particles, and pigment particles.
The improved pigmented coating has a polymeric film that is formed
from the second polymer particles and the PNPs. The polymeric film
of the improved pigmented coating has a lower refractive index than
a film formed absent the PNPs and thus has a greater difference in
the refractive indices of the polymeric film and the pigment
contained within. The improved pigmented coating provides increased
hiding compared to a pigmented coating absent the PNPs. The polymer
film of the improved pigmented coating typically contains from 2 to
30 weight % PNPs, based on the total weight of the polymeric
film.
[0074] Yet still other certain embodiments of the aqueous polymeric
composition include one or more other components, such as, without
limitation, other polymers, surfactants, other pigments, other
extenders, dyes, pearlescents, adhesion promoters, crosslinkers,
dispersants, defoamers, leveling agents, optical brighteners,
ultraviolet stabilizers, absorbing pigments, coalescents, rheology
modifiers, preservatives, biocides, and antioxidants.
[0075] The following examples are presented to illustrate the
composition and the process of the invention. These examples are
intended to aid those skilled in the art in understanding the
present invention. The present invention is, however, in no way
limited thereby.
EXAMPLE 1
Aqueous Polymeric Composition Containing PNPs and Second Polymer
Particles
[0076] An aqueous polymeric composition is prepared by admixing an
aqueous dispersion containing PNPs with an aqueous dispersion
containing second polymer particles. The PNPs contain, as
polymerized units, 60 weight % methyl methacrylate, 30 weight %
acrylic acid, and 10 weight % trimethylolpropane triacrylate. The
PNPs have a T.sub.g above 50.degree. C. and a mean particle
diameter of 12 nm. The aqueous dispersion containing the PNPs is
provided at pH=8 with ammonia. The second polymer particles are
acrylic copolymer particles having a T.sub.g of 3.degree. C. and a
mean particle diameter of 155 nm. The aqueous polymeric
composition, Example 1.1, contains 15 weight % PNPs and 85 weight %
second polymer particles, and has a total polymer solids content of
33 weight %.
[0077] A pigmented aqueous polymeric composition and a comparative
composition are prepared by combining the ingredients in Table 2.1
in the order listed. TABLE-US-00002 Ingredient Example 1.2
Comparative A titanium dioxide dispersion 344.07 g 344.07 g (77
weight %) Water 20.00 g 20.00 g propylene glycol 16.50 g 16.50 g
Example 1.1 (33 weight % 537.65 g -- solids) Aqueous dispersion of
second -- 537.65 g polymer particles (33 weight % solids)
surfactant 1.00 g 1.00 g ammonia (28%) 0.70 g 0.70 g Acrysol .TM.
RM-2020 NPR 29.00 g 29.00 g rheology modifier (Rohm and Haas Co.)
Acrysol .TM. RM-8W rheology 5.60 g 5.60 g modifier (Rohm and Haas
Co.) Water 104.2 g 113.62 g VOC (weight %) <2.25 <2.25
[0078] Dry coating samples are prepared from the pigmented aqueous
polymeric composition, Example 1.2, and the comparative
composition, Comparative A, and are evaluated according to the
procedure for the scrub resistance test. The two compositions are
applied in such a way that the two compositions are placed side by
side and drawn together by a single drawing with a 0.0762 mm (3
mil) film applicator 152.4 mm (6 inch) in width. Each composition
forms a 7.5 cm (3 inch) wide coating on a single vinyl chart, and
the two compositions have the same coating thickness. The samples
are allowed to dry at 23.degree. C. and 50% relative humidity for 7
days. Abrasive scrub resistance is measured with a scrub machine
using 10 g scrub medium and 5 ml water. A piece of 0.0254 mm (1
mil) thick and 76.2 mm wide vinyl shim is placed underneath the
sample vinyl chart. The two side edges of the shim are in the
center of each coating. The number of cycles required to completely
cut through each coating is recorded.
[0079] The coating prepared from the pigmented aqueous polymeric
composition of Example 1.2 requires 750 cycles to cut through the
coating. In contrast, the coating prepared from the pigment
comparative composition of Comparative A requires 360 cycles to cut
through the coating. The results show that the aqueous polymeric
composition of this invention is useful for preparing coatings with
improved scrub resistance.
EXAMPLE 2
Preparation of PNPs
EXAMPLE 2.1
[0080] PNPs are prepared containing, as polymerized units, 35
weight % methyl methacrylate, 35 weight % butyl acrylate, 20 weight
% acrylic acid, and 10 weight % trimethylolpropane triacrylate. The
PNPs are prepared according to the following process: A 5-liter
reactor is fitted with a thermocouple, a temperature controller, a
purge gas inlet, a water-cooled reflux condenser with purge gas
outlet, a stirrer, and a monomer feed line. To a first additional
vessel, 450.0 g of a monomer mixture (A) is prepared by admixing
157.5 g methyl methacrylate, 157.5 g butyl acrylate, 90.0 g acrylic
acid, and 45.0 g trimethylolpropane triacrylate. To a second
additional vessel, an initiator mix (B) is prepared by admixing
18.00 g of a 75% solution of t-amyl peroxypivalate in mineral
spirits and 112.50 g isopropyl alcohol. A charge of 2325 g
isopropyl alcohol is added to the reactor. Nitrogen gas is flowed
through the reactor for approximately 30 minutes. Next, the
contents of the reactor are heated to 79.degree. C. while
maintaining the flow of nitrogen gas. Next, a dual feed of the
monomer mixture (A) and the initiator mix (B) are added to the
reactor. The two mixtures are feed uniformly using feed pumps over
an addition period of 120 minutes. At the end of the monomer and
initiator feeds, the contents of the reactor are maintained at
79.degree. C. for 30 minutes. Next, the first of three additional
initiator charges, each containing 9.00 g of a 75% solution of
t-amyl peroxypivalate in mineral spirits, and 22.50 g isopropyl
alcohol, is added. A second initiator charge is added 30 minutes
after the first initiator charge addition. Similarly, the final
initiator charge is added 30 minutes after the second initiator
charge addition. The contents of the reactor are then held at a
temperature of 79.degree. C. for a period of 150 minutes. Next,
contents of the reactor are neutralized with a mixture of 42.5 g of
aqueous ammonia (28% active) and 450.0 g water. Solvent is removed
from the contents of the reactor by using a roto-evaporator at
35.degree. C. and at reduced pressure. Next, water is added to
dilute the concentration of the resulting PNPs to 25.6 weight %.
The resulting aqueous polymeric composition, Example 2.1, contains
PNPs with a mean particle diameter of 5 nm and has a pH of 8.5.
EXAMPLE 2.2
[0081] PNPs containing, as polymerized units, 35 weight % methyl
methacrylate, 35 weight % butyl acrylate, 20 weight % acrylic acid,
and 10 weight % trimethylolpropane triacrylate are prepared
according to the general procedure for preparing Example 2.1. The
resulting aqueous polymeric composition contains PNPs having a mean
particle diameter of 5 nm and has a solids level of 25 weight
%.
EXAMPLE 3
[0082] Preparation of Second Polymer Particles in the Presence of
PNPs Second polymer particles are prepared by emulsion
polymerization in the presence of PNPs. The reaction vessel is a
2-liter, 4 neck round bottom flask equipped with a side arm,
condenser, stirrer, and thermocouple.
EXAMPLE 3.1
[0083] To the flask, 342 g of the aqueous polymeric composition of
Example 2.1 is added. The contents of the flask is heated to
85.degree. C. under a nitrogen atmosphere. Next, a monomer mixture
containing 175.0 g butyl acrylate and 175.0 g methyl methacrylate
is added over a 1.5 hour period, while coadding a separate solution
of 2.63 g ammonium persulfate in 100.0 g deionized water and 0.22 g
of 28% ammonium hydroxide over a 2 hour time period. After the
addition of the monomer mixture is complete, the persulfate
containing cofeed is continued for 30 minutes. Next, the contents
of the flask is maintained at a temperature of 85.degree. C. for 60
minutes. The contents of the flask is allowed to cool to 25.degree.
C. and is filtered through a 100/325 mesh set of stacked screens,
yielding a negligible quantity of coagulated polymer. The resulting
filtered emulsion polymerization product, an aqueous polymeric
composition containing PNPs and second polymer particles, has a
total polymer solids content of 55.04%, a pH of 7.5, second polymer
particles with a mean diameter of 128 nm, and a viscosity of 1.09
pascal second. The aqueous polymeric composition of Example 3.1
contains 20 weight % PNP and 80 weight % second polymer particles,
based on the total weight of polymer.
EXAMPLE 3.2
[0084] Second polymer particles are prepared in the presence of
PNPs according to the general procedure for Example 3.1. The
resulting aqueous polymeric composition of Example 3.2 contains 50
weight % PNPs of Example 3.1 and 50 weight % second polymer
particles containing, as polymerized units, 65 weight % butyl
acrylate and 35 weight % methacrylic acid, based on the total
weight of polymer.
* * * * *