U.S. patent application number 11/009424 was filed with the patent office on 2005-06-02 for copolymers comprising low surface tension (meth) acrylates.
Invention is credited to Coca, Simion, O'Dwyer, James B., Olson, Kurt G., Smith, Joanne H..
Application Number | 20050119409 11/009424 |
Document ID | / |
Family ID | 26930596 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050119409 |
Kind Code |
A1 |
Olson, Kurt G. ; et
al. |
June 2, 2005 |
Copolymers comprising low surface tension (meth) acrylates
Abstract
The present invention is directed to a copolymer that includes a
first radically polymerizable low surface tension (meth)acrylate
monomer and one or more other radically polymerizable ethylenically
unsaturated monomers. The copolymer has a polydispersity index of
less than 2.5. The present invention further includes a controlled
radical polymerization method to make the above described low
surface tension containing copolymers. The method includes the
steps of adding a first radically polymerizable low surface tension
(meth)acrylate monomer and one or more other radically
polymerizable ethylenically unsaturated monomers to a solution
containing a suitable atom transfer radical polymerization (ATRP)
initiator.
Inventors: |
Olson, Kurt G.; (Gibsonia,
PA) ; Coca, Simion; (Pittsburgh, PA) ;
O'Dwyer, James B.; (Valencia, PA) ; Smith, Joanne
H.; (Allison Park, PA) |
Correspondence
Address: |
PPG INDUSTRIES, INC.
Intellectual Property Department
One PPG Place
Pittsburgh
PA
15272
US
|
Family ID: |
26930596 |
Appl. No.: |
11/009424 |
Filed: |
December 10, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11009424 |
Dec 10, 2004 |
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10237357 |
Sep 9, 2002 |
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6841641 |
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60325242 |
Sep 27, 2001 |
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Current U.S.
Class: |
525/92F |
Current CPC
Class: |
C08F 220/10
20130101 |
Class at
Publication: |
525/092.00F |
International
Class: |
C08L 053/00 |
Claims
1-52. (canceled)
53. A thermosetting composition comprising: (a) a non-gelled
polymer comprising functional monomers with a functional group; (b)
a crosslinking agent having at least two functional groups that are
reactive with the functional groups of the non-gelled polymer in
(a); and (c) a copolymer flow control agent comprising a radically
polymerizable low surface tension (meth)acrylate monomer and at
least one other radically polymerizable ethylenically unsaturated
monomer, wherein the radically polymerizable low surface tension
(meth)acrylate monomer is selected from at least one low surface
tension (meth)acrylate monomer represented by the general formulas:
11wherein R.sub.1 is selected independently for each general
formula from hydrogen, methyl and ethyl, R.sub.2 is selected
independently for each general formula from the group consisting of
linear, branched, cyclic, aryl and arylalkyl fluorinated
hydrocarbon groups containing from 4-20 carbon, a siloxane, a
polysiloxane, an alkyl siloxane, an ethoxylated trimethylsilyl
siloxane and a propoxylated trimethylsilyl siloxane; Y is a
divalent linking group containing from 1 to 20 carbon atoms, m is
an integer from 1 to 4, and R.sub.3 is a C.sub.1-C.sub.4 alkyl
group.
54. The thermosetting composition of claim 53 wherein m is 2.
55. The thermosetting composition of claim 53 wherein said
copolymer flow additive is prepared by controlled radical
polymerization.
56-59. (canceled)
60. The thermosetting composition of claim 53 wherein said
radically polymerizable low surface tension (meth)acrylate monomer
is present in an amount of from 0.01 percent by weight to 5.0
percent by weight, based on the total weight of said copolymer flow
additive; and said at least one other radically polymerizable
ethylenically unsaturated monomer is present in an amount of from
95 percent by weight to 99.99 percent by weight, based on the total
weight of said copolymer flow additive.
61. The thermosetting composition of claim 53 wherein said at least
one other radically polymerizable ethylenically unsaturated monomer
is selected from vinyl monomers, allylic monomers, olefins and
mixtures thereof.
62. (canceled)
63. The thermosetting composition of claim 53 wherein said
copolymer flow additive has a number average molecular weight of
from 500 to 100,000.
64. The thermosetting composition of claim 53 wherein R.sub.1 is
hydrogen or methyl, Y is --(CH.sub.2).sub.n--, and n is an integer
from 1 to 11.
65. The thermosetting composition of claim 53 wherein said
copolymer flow additive is present in an amount of from 0.01
percent by weight to 5 percent by weight, based on the total resin
solids weight of said coating composition.
66. (canceled)
67. The thermosetting composition of claim 53, wherein the
functional groups of the non-gelled polymer (a) are selected from
the group consisting of epoxy, oxirane, carboxylic acid, hydroxy,
amide, oxazoline, aceto acetate, isocyanate, and carbamate; and the
functional groups of crosslinking agent (b) are different than
those in the non-gelled polymer (a), are reactable with those in
the non-gelled polymer (a), and are selected from the group
consisting of epoxy, oxirane, carboxylic acid, hydroxy, polyol,
isocyanate, capped isocyanate, amine, aminoplast and
beta-hydroxyalkylamide.
68-73. (canceled)
74. The thermosetting composition of claim 53 further comprising a
third monomer wherein the copolymer flow control agent is a
gradient copolymer defined by the
structure:.phi.--{[--(M).sub.s-a--(E).sub.a--. . .
--(M).sub.s-na--(E).sub.na--]--[L].sub.m--T}.sub.zwherein s is an
integer from 1 to 300; a is an integer from 1 to 200; n is an
integer from 1 to 299 such that s, n and a satisfy the relationship
s-na>0; M represents the other radically polymerizable
ethylenically unsaturated monomers; L represents the radically
polymerizable low surface tension (meth)acrylate monomer; .phi. is
or is derived from the residue of the initiator free of radically
transferable groups; T is or is derived from the radically
transferable group of the initiator; and z is at least 1; E is a
third polymerizable ethylenically unsaturated monomer; and m is an
integer from 1 to 50.
75. The thermosetting composition of claim 53 wherein the copolymer
flow control agent is defined by the
structure:.phi.--[--(M).sub.s-a--(L).sub.-
a--(M).sub.s-2a--(L).sub.2a--(M).sub.s-3a--(L).sub.3a--. . .
--(M).sub.s-na--(L).sub.na--T].sub.zwherein s is an integer from 1
to 300, a is an integer from 1 to 10, n is an integer from 1 to 299
such that s, n and a satisfy the relationship s-na>0, F
represents a radically polymerizable low surface tension
(meth)acrylate monomer, M represents at least one other radically
polymerizable ethylenically unsaturated monomer, .phi. is or is
derived from the residue of an atom transfer polymerization
initiator free of radically transferable groups; T is or is derived
from the radically transferable group of the initiator; z is at
least 1 and the low surface tension (meth)acrylate monomer is one
or more selected from the group consisting of those represented by
the following general formulas, 12wherein R.sub.1 is selected
independently for each general formula from hydrogen, methyl and
ethyl, R.sub.2 is selected independently for each general formula
from the group consisting of linear, branched, cyclic, aryl and
arylalkyl fluorinated hydrocarbon groups containing from 4-20
carbon, a siloxane, a polysiloxane, an alkyl siloxane, an
ethoxylated trimethylsilyl siloxane and a propoxylated
trimethylsilyl siloxane; Y is a divalent linking group containing
from 1 to 20 carbon atoms, m is an integer from 1 to 4, and R.sub.3
is a C.sub.1-C.sub.4 alkyl group.
76-79. (canceled)
80. The thermosetting composition claim 75 wherein z is 1.
81-100. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn. 119
to Provisional Application Ser. No. 60/325,242, filed Sep. 27,
2001.
FIELD OF THE INVENTION
[0002] The present invention relates to novel (co)polymer
compositions that contain low surface tension (meth)acrylates
prepared by a controlled radical (co)polymerization process and
thermosetting compositions containing the novel (co)polymers.
BACKGROUND OF THE INVENTION
[0003] Fluorocarbon-containing copolymers have been used as binding
agents, wetting-agents, surfactants and coating additives in a
variety of applications. Fluorocarbon-containing copolymers made by
conventional free radical polymerization methods have inevitable
shortcomings as it is difficult to control their molecular weight
distribution and composition in order to optimize their desired
physical properties. For example, the common problem of poor
control of molecular weight distribution can result in a high
molecular weight "tail" which can give poor flow properties due to
the high viscosity that results. Conversely, poor binding
properties can result when too much of a low molecular weight
"tail" is present.
[0004] U.S. Pat. Nos. 5,397,669 and 5,283,148 disclose an
electrostatic liquid toner imaging process that uses a liquid toner
comprised of a perfluorinated solvent and a polymer containing
highly fluorinated units. The polymer was prepared using
traditional free radical polymerization techniques and was
characterized as having a polydispersity of 4.
[0005] U.S. Pat. No. 3,407,247 discloses fluoro olefin block
copolymers prepared by traditional free radical polymerization of a
(meth)acrylic monomer to form a prepolymer which is subsequently
reacted with a fluoro olefin. While block copolymers were formed to
some extent, the resulting block copolymers inherently vary widely
in block length and molecular weight leading to a wide
compositional variation and distribution as well as a large
polydispersity.
[0006] U.S. Pat. No. 5,026,621 discloses a toner for
electrophotography which includes a block copolymer binder resin
comprised of a fluoroalkyl acryl ester block and a fluorine-free
vinyl or olefin monomer block. The block copolymers were made using
a unique peroxypolyether initiator, which is then used to initiate
a first free radical polymerization, forming a peroxypolymer, which
initiates a second free radical polymerization. While block
copolymers are formed, the resulting block copolymers inherently
vary widely in block length and molecular weight, as well as having
a wide compositional variation, wide polymer composition
distribution and a large polydispersity.
[0007] U.S. Pat. No. 5,478,886 discloses alkyl
.alpha.-fluoroacrylate ester block copolymers prepared by group
transfer polymerization techniques. The block copolymers have a
polydispersity of less than 2 and do not contain any initiator
residue. The disclosure is limited to fluoroacrylate monomers as
the fluorocarbon monomer. These types of block copolymers are used
primarily in the electronics industry as photoresists. The block
copolymers are particularly subject to photodegradation.
[0008] U.S. Pat. Nos. 5,629,372; 5,705,276; and 5,914,384 disclose
coating compositions comprising an alkyl (meth)acrylate/fluoroalkyl
methacrylate random copolymer and a crosslinking agent. The
materials disclosed were suggested for use as clear coating
compositions for application over a pigmented base coat.
[0009] The use of conventional, i.e., non-living or free-radical
(co)polymerization methods to synthesize (co)polymers provides
little control over molecular weight, molecular weight distribution
and, in particular, (co)polymer chain structure. In the example of
fluoroalkyl methacrylate random copolymer described above, the
potential surface tension effect of the fluoroalkyl methacrylate is
muted as it is randomly dispersed along the polymer backbone.
[0010] U.S. Pat. Nos. 5,807,937, 5,789,487 and 5,763,548, and
International Patent Publication Nos. WO 98/40415, WO 98/01480, WO
97/18247 and WO 96/30421 describe a radical polymerization process
referred to as atom transfer radical polymerization. (ATRP). The
ATRP process is described as being a living radical polymerization
that results in the formation of polymers having predictable
molecular weight and molecular weight distribution. The ATRP
process also is described as providing highly uniform products
having controlled structure (i.e., controllable topology,
composition, etc.). The '937 and '548 patents also describe
(co)polymers prepared by ATRP, which are useful in a wide variety
of applications including, for example, dispersants and
surfactants.
[0011] A number of initiators and macroinitiator systems are known
to support ATRP polymerization. These initiators are described, for
example, in U.S. Pat. Nos. 5,807,937 and 5,986,015. U.S. Pat. No.
5,807,937 discloses a number of initiators, including halide groups
attached to a primary carbon. Halides attached to primary carbons
are known as efficient initiators in ATRP processes. U.S. Pat. No.
5,986,015 discloses polymer macroinitiators prepared from vinyl
chloride and another monomer, and their use in preparing graft
(co)polymers with low polydispersity.
[0012] It also is desirable to have multiple initiation sites on an
initiator in order to create unique branched (co)polymer
structures, such as star (co)polymers. Such (co)polymers have a
variety of practical applications, including as a resin component
of a film-forming coating composition. These unique (co)polymers
also will find use in the health care or cosmetics industries, for
instance, as materials for bioengineering. (Co)polymers of low
polydispersity (Mn/Mw) are also desirable not only for their
structural regularity and related usefulness in producing defined
block and gradient (co)polymer structures, but also for their
unique physical characteristics. For instance, a star (co)polymer
having low polydispersity is a high molecular weight material
having low viscosity in solution.
[0013] There remains a need for copolymers that have reliable
compositions and predictable molecular weight, polydispersity and
surface tension lowering effect. Such copolymers can overcome the
deficiencies of the copolymers of the prior art.
SUMMARY OF THE INVENTION
[0014] In accordance with the present invention, there is provided
a copolymer that includes a low surface tension monomer and one or
more other radically polymerizable ethylenically unsaturated
monomers. The copolymer preferably has a polydispersity index of
less than 2.5.
[0015] The present invention is also directed to a thermosetting
composition which includes:
[0016] a non-gelled polymer which has functional monomers
containing a functional group;
[0017] a crosslinking agent having at least two functional groups
that-are reactive with the functional groups of the non-gelled
polymer; and
[0018] a flow control agent which includes a copolymer, generally
having a polydispersity index of less than 2.5, containing monomers
that include one or more radically polymerizable low surface
tension (meth)acrylate monomers and one or more other radically
polymerizable ethylenically unsaturated monomers, where the low
surface tension (meth)acrylate monomers are represented by the
following formulas: 1
[0019] where R.sub.1 is selected independently for each general
formula from hydrogen, methyl and ethyl, R.sub.2 is selected
independently for each general formula from a fluorinated
hydrocarbon group, a siloxane, a polysiloxane, an alkyl siloxane,
an ethoxylated trimethylsilyl siloxane and a propoxylated
trimethylsilyl siloxane. R.sub.2 may contain from 4-20 carbon
atoms, which can be linear, branched, cyclic, aryl or arylalkyl; Y
is a divalent linking group containing from 1 to 20 carbon atoms
and can be linear, branched, cyclic or aryl; m is an integer from 1
to 4; and R.sub.3 is a C.sub.1-C.sub.4 alkyl.
[0020] The present invention is also directed to a method of
coating a substrate, which includes the steps of:
[0021] applying the thermosetting composition of the present
invention to a substrate;
[0022] coalescing the thermosetting composition over the substrate
in the form of a substantially continuous film; and
[0023] curing the thermosetting composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Other than in the operating examples, or where otherwise
indicated, all numbers or expressions referring to quantities of
ingredients, reaction conditions, etc., used in the specification
and claims are to be understood as modified in all instances by the
term "about".
[0025] The terms (meth)acrylic and (meth)acrylate are meant-to
include both acrylic and methacrylic acid derivatives, such as the
corresponding alkyl esters often referred to as acrylates and
(meth)acrylates, which the term (meth)acrylate is meant to
encompass.
[0026] The present invention is directed to a copolymer that
includes a radically polymerizable low surface tension
(meth)acrylate monomer and one or more other radically
polymerizable ethylenically unsaturated monomers that are free of
hydroxyl groups and amine group residues.
[0027] Any type of copolymer can be used in the present invention.
Examples of copolymer architectures that can be used in the present
invention include, but are not limited to random, block (including
diblock, triblock and other multiblock architectures), alternating
and gradient copolymers. The structure of the copolymers can
generally be described by formulas I and II:
--[--(O).sub.p--(L).sub.q--].sub.x-- (I)
--[(O).sub.p(L).sub.q]-- (II)
[0028] Where formula I represents a copolymer of controlled
architecture, such as alternating, block or gradient and formula II
represents a random copolymer. In formulas I and II, O represents
one or more other radically polymerizable ethylenically unsaturated
monomers that are free of hydroxyl groups and amine group residues;
L represents a low surface tension (meth)acrylate monomer; p and q
represent average numbers of monomer residues; and x represents the
number of block sequences in a block copolymer. In general, p and q
are integers representing the respective average number of monomer
residues in a copolymer. The number of other monomers, p, can be
from 1 to 1,000, preferably from 2 to 500 and most preferably from
3 to 250. The number of low surface tension (meth)acrylate
monomers, q, can be from 1 to 200, preferably from 1 to 100 and
most preferably from 1 to 50. The number of block sequences, x, can
be from 1 to 1,000, preferably from 1 to 500 and most preferably
from 1 to 100.
[0029] A preferred class of copolymers useful in the present
invention are gradient copolymers. Gradient copolymers are
copolymers that include one or more sequences of different classes
of monomer residues that change gradually in a systematic and
predictable manner along the polymer backbone. At an end of the
polymer referred to as a tail, the gradient copolymer will contain
predominantly the other radically polymerizable ethylenically
unsaturated monomer(s) and another end, the head, will contain
predominantly the radically polymerizable fluorocarbon
(meth)acrylate monomer. The portions of the polymer backbone
between the head and the tail will contain continuously changing
proportions of the two classes of monomers. By way of illustration,
the gradient copolymer of the present invention may have a
structure as depicted in general structure III:
-O-O-O-O-L-O-O-O--L-L-O-O-L-L-L-O-L-L-L-L- (III)
[0030] Tail End Head End
[0031] where O represents one or more of the other radically
polymerizable ethylenically unsaturated monomers and L represents a
radically polymerizable low surface tension (meth)acrylate
monomer.
[0032] By low surface tension (meth)acrylate monomer, what is meant
is (meth)acrylate monomers that have highly surface active groups
contained within the ester portion of the molecule. Examples of
highly surface active groups include, but are not limited to,
fluorides, silanes, siloxanes, (mono, di and tri) alkyl siloxanes
and the like.
[0033] Any polymerizable low surface tension (meth)acrylate monomer
can be used in the gradient copolymer of the present invention.
Preferred low surface tension (meth)acrylate monomers are
represented by formulas IV and V, 2
[0034] wherein R.sub.1 is selected independently for each general
formula from hydrogen, methyl and ethyl, R.sub.2 is selected
independently for each general formula from a fluorinated
hydrocarbon group, a siloxane, a polysiloxane, an alkyl siloxane,
an ethoxylated trimethylsilyl siloxane and a propoxylated
trimethylsilyl siloxane. R.sub.2 may contain from 4-20 carbon
atoms, which can be linear, branched, cyclic, aryl or arylalkyl; Y
is a divalent linking group containing from 1 to 20 carbon atoms
and can be linear, branched, cyclic or aryl; m is an integer from 1
to 4, preferably 1 to 3, and in an embodiment of the present
invention m is 2; and R.sub.3 is a C.sub.1-C.sub.4 alkyl.
[0035] When the group R.sub.2 is a fluorinated alkyl group, it can
be linear, branched or cyclic. The fluorinated hydrocarbon group
R.sub.2 can be described by general structure VI: 3
[0036] where R.sub.34, R.sub.35, R.sub.36, R.sub.37 and R.sub.38
can each independently be H, F, and Cl to C.sub.6 alkyl, as long as
at least one occurrence of R.sub.34, R.sub.35, R.sub.36, R.sub.37
or R.sub.38 is F; and d is an integer-from 3 to 19.
[0037] When R.sub.2 is a C.sub.1-C.sub.20 linear or branched alkyl
group, one or more of the hydrogens are replaced with fluorine
atoms. A non limiting example would be if R.sub.2 were a propyl
group, in which case it may be 3-fluoropropyl, 3, 3-difluoropropyl,
3, 3, 3-trifluoropropyl, 1,2,3-trifluoropropyl, etc. When R.sub.2
is a C.sub.1-C.sub.20 linear or branched cyclic group, one or more
of the hydrogens are replaced with fluorine atoms. A non limiting
example would be if R.sub.2 were a cyclohexyl group, in which case
it may be 3-fluorocyclohexyl, 3, 3-difluorocyclohexyl, 1, 2,
3-trifluorocyclohexyl, 2, 3, 4, 5-tetrafluorocyclohexyl, etc. When
R.sub.2 is a C.sub.1-C.sub.20 linear or branched aryl or arylalkyl
group, one or more of the hydrogens are replaced with fluorine
atoms. Non limiting examples of fluoroaryl and fluoroarylalkyl
groups which can be part of the present gradient copolymer include
those described by general structures VII-X: 4
[0038] where R.sub.4 is C.sub.1-C.sub.4 alkyl or alkynol, X is
hydrogen or fluorine and n is an integer from 1 to 10.
[0039] Typically, useful perfluoroalkyl containing monomers are
perfluoro methyl ethyl methacrylate, perfluoro ethyl ethyl
methacrylate, perfluoro butyl ethyl methacrylate, perfluoro pentyl
ethyl methacrylate, perfluoro hexyl ethyl methacrylate, perfluoro
octyl ethyl methacrylate, perfluoro decyl ethyl methacrylate,
perfluoro lauryl ethyl methacrylate, perfluoro stearyl ethyl
methacrylate, perfluoro methyl ethyl acrylate, perfluoro ethyl
ethyl acrylate, perfluoro butyl ethyl acrylate, perfluoro pentyl
ethyl acrylate, perfluoro hexyl ethyl acrylate, perfluoro octyl
ethyl acrylate, perfluoro decyl ethyl acrylate, perfluoro lauryl
ethyl acrylate, perfluoro stearyl ethyl acrylate, trifluoromethyl
benzyl acrylate, trifluoromethyl benzyl methacrylate,
1,1,1-trifluoropropyl benzyl acrylate methacrylate,
1,1,1-trifluoropropyl benzyl methacrylate ethyleneglycol
perfluorophenyl ether acrylate, ethyleneglycol perfluorophenyl
ether methacrylate, 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-hex-
adecafluorodecyl benzyl ether acrylate,
1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-- hexadecafluorodecyl benzyl
ether methacrylate, and the like. Preferred are perfluoro alkyl
ethyl methacrylates wherein the fluoroalkyl group contains 4-20
carbon atoms and benzyl ether acrylates and methacrylates of
Zonyl.RTM. FTS fluorotelomer intermediate, Zonyl.RTM. FTS is a
commercially available C.sub.9-C.sub.10 partially fluorinated
alcohol from DuPont.
[0040] When R.sub.2 includes a siloxane, it may be described by the
following general structure XI: 5
[0041] where R.sub.31 is a linear, branched or cyclic
C.sub.2-C.sub.18 alkyl or a polyether as in general formula XII:
6
[0042] where R.sub.33 is a hydrogen, a halide or methyl and y is
from 1 to 100, preferably from 1 to 50 and most preferably from 1
to 25 and R.sub.32 is hydrogen, a linear, branched or cyclic
C.sub.2-C.sub.18 alkyl or a trimethylsiloxane as in general
structure XIII: 7
[0043] and w is from 0 to 500, preferably from 1 to 100 and most
preferably from 1 to 50.
[0044] Typically, useful siloxane containing low surface tension
(meth)acrylates include, but are not limited to,
(meth)acryloxyalkyl terminated polydimethylsiloxanes, such as those
available as MCR-M11 and MCR-M17 from Gelest, Inc., Tullytown, Pa.
and X-22-174DX and X-22-2426 available as X-22-174DX from Shin-Etsu
Chemical Co., Ltd., Tokyo, Japan; (meth)acryloxyalkyl
tris(trimethylsiloxy silane), such as that available as X-22-174DX
from Shin-Etsu Chemical Co.; and (meth)acryloxyalkyl
trimethylsiloxy terminated polyethylene oxide such as that
available as SIM0479.0 from Gelest, Inc.
[0045] In the copolymer of the present invention, the copolymer
will contain the low surface tension (meth)acrylate monomer in an
amount up to 5 wt. %, preferably from 0.01 wt. % to 5 wt. %, more
preferably from 0.1 wt. % to 5 wt. % and most preferably from 1 wt.
% to 3 wt. % based on the total weight of the copolymer. The
ethylenically unsaturated monomers are present in an amount of at
least 95 wt. %, preferably from 95 wt. % to 99.99 wt. %, more
preferably from 95 wt. % to 99.9 wt. % and most preferably from 97
wt. % to 99 wt. % based on the total weight of the copolymer.
[0046] A third monomer may also be included in the copolymer. In
the case of a gradient copolymer, the portions of the polymer
backbone between the head and the tail will contain continuously
changing proportions of the three monomers. By way of illustration,
a gradient copolymer containing three different monomer
compositions may have a structure as depicted in general structure
XIV:
-O-O-O-H-H-H-L-O-O-H-H--L-L-O-H-L-L-L-O-L-L-L-L- (XIV)
[0047] Tail End Head End
[0048] where O represents one or more of the other radically
polymerizable ethylenically unsaturated monomers, H represents the
third monomer or monomer composition and L represents a radically
polymerizable low surface tension (meth)acrylate monomer.
[0049] The third monomer can be present in an amount of from 0 wt.
% to 75 wt. %, preferably from 20 wt. % to 75 wt. % and most
preferably from 35 wt. % to 65 wt. % based on the total weight of
the copolymer. When the third monomer is present, the amount of
each block will be from 0.01 to 5 wt. %, more preferably from 0.1
wt. % to 5 wt. % based and most preferably from 1 to 3 wt. % of the
first low surface tension (meth)acrylate monomer, from 25 wt. % to
75 wt. %, more preferably from 30 wt. % to 70 wt. % and most
preferably from 35 wt. % to 65 wt. % of the other radically
polymerizable ethylenically unsaturated monomers, and from 20 wt. %
to 74.99 wt. %, more preferably from 25 wt. % to 69.9 wt. % and
most preferably from 32 wt. % to 64 wt. % of the third monomer
based on the total weight of the copolymer.
[0050] Optionally, the other ethylenically unsaturated monomer and
third monomer may include a hydroxyl functional monomer. The
hydroxy functional monomer can be present in at least one of the
other polymerizable ethylenically unsaturated monomer or third
monomer in an amount of from 0.01 wt. % to 5 wt. %, preferably from
0.05 wt. % to 4 wt. % and most preferably from 0.1 wt. % to 3 wt. %
based on the total weight of the copolymer.
[0051] The other radically polymerizable ethylenically unsaturated
monomer and third monomer can be any radically polymerizable
alkylene containing a polar group. The preferred monomers are
ethylenically unsaturated monomers and include monomers having
general structure XV: 8
[0052] where R.sub.5, and R.sub.6 are independently selected from
the group consisting of H, halogen, CN, straight or branched alkyl
of 1 to 20 carbon atoms (preferably from 1 to 6 carbon atoms, more
preferably from 1 to 4 carbon atoms), aryl, unsaturated straight or
branched alkenyl or alkynyl of 2 to 10 carbon atoms (preferably
from 2 to 6 carbon atoms, more preferably from 2 to 4 carbon
atoms), unsaturated straight or branched alkenyl of 2 to 6 carbon
atoms (preferably vinyl) substituted (preferably at the
.alpha.-position) with a halogen (preferably chlorine),
C.sub.3-C.sub.8 cycloalkyl, heterocyclyl, phenyl which may
optionally have from 1-5 substituents on the phenyl ring,
C(.dbd.Y)R.sub.9, C(.dbd.Y)NR.sub.10R.sub.11, YCR.sub.10 R.sub.11
R.sub.12 and YC(.dbd.Y)R.sub.12, where Y may be NR.sub.13 or O
(preferably O), R.sub.9 is alkyl of from 1 to 20 carbon atoms,
alkoxy of from 1 to 20 carbon atoms, aryloxy or heterocyclyloxy,
R.sub.10 and R.sub.11 are independently H or alkyl of from 1 to 20
carbon atoms, or R.sub.10 and R.sub.11 may be joined together to
form an alkylene group of from 2 to 5 carbon atoms, thus forming a
3- to 6-membered ring, and R.sub.12 is H, straight or branched
C.sub.1-C.sub.20; alkyl and aryl; and R.sub.7 is selected from the
group consisting of H, halogen (preferably fluorine or chlorine),
C.sub.1-C.sub.6 (preferably C.sub.1) alkyl, CN, COOR.sub.14 (where
R.sub.14 is H, an alkali metal, or a C.sub.1-C.sub.6 alkyl group)
or aryl; or R.sub.5 and R.sub.7 may be joined to form a group of
the formula (CH.sub.2).sub.n, (which may be substituted with from 1
to 2n' halogen atoms or C.sub.1-C.sub.4 alkyl groups) or
C(.dbd.O)--Y--C(.dbd.O), where n' is from 2 to 6 (preferably 3 or
4) and Y is as defined above; and R.sub.8 is the same as R.sub.5 or
R.sub.6 or optionally R.sub.8 is a CN group; at least two of
R.sub.5, R.sub.6, and R.sub.7 are H or halogen.
[0053] Specific examples of ethylenically unsaturated monomers that
the copolymer of the present invention may contain include
ethylenically unsaturated monomers, allylic monomers, olefins
(meth)acrylic acid, (meth)acrylates, (meth)acrylamide, N- and
N,N-di-substituted (meth)acrylamides, vinyl aromatic monomers,
vinyl halides, vinyl esters of carboxylic acids and mixtures
thereof. More specific examples of suitable monomers include,
without limitation, C.sub.1-C.sub.20 alkyl (meth)acrylates
(including linear or branched alkyls and cycloalkyls) which
include, but are not limited to, methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate,
n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl
(meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate,
isobornyl (meth)acrylate, cyclohexyl (meth)acrylate,
3,3,5-trimethylcyclohexyl (meth)acrylate and isooctane
(meth)acrylate; oxirane functional (meth)acrylates which include,
but are not limited to, glycidyl (meth)acrylate,
3,4-epoxycyclohexylmethyl(meth)acrylate, and
2-(3,4-epoxycyclohexyl) ethyl(meth)acrylate; hydroxy alkyl
(meth)acrylates having from 2 to 4 carbon atoms in the alkyl group
which include, but are not limited to, hydroxyethyl (meth)acrylate,
hydroxypropyl (meth)acrylate and hydroxybutyl (meth)acrylate. The
residues may each independently be residues of monomers having more
than one (meth)acryloyl group, such as (meth)acrylic anhydride,
diethyleneglycol bis(meth)acrylate, 4,4'-isopropylidenediphenol
bis(meth)acrylate (Bisphenol A di(meth)acrylate), alkoxylated
4,4'-isopropylidenediphenol bis(meth)acrylate, trimethylolpropane
tris(meth)acrylate and alkoxylated trimethylolpropane
tris(meth)acrylate.
[0054] In the context of the present application, the terms
"alkyl", "alkenyl" and "alkynyl" refer to straight-chain or
branched groups. Furthermore, in the present application, "aryl"
refers to phenyl, naphthyl, phenanthryl, phenalenyl, anthracenyl,
triphenylenyl, fluoranthenyl, pyrenyl, pentacenyl, chrysenyl,
naphthacenyl, hexaphenyl, picenyl and perylenyl (preferably phenyl
and naphthyl), in which each hydrogen atom may be replaced with
alkyl of from 1 to 20 carbon atoms (preferably from 1 to 6 carbon
atoms and more preferably methyl), alkyl of from 1 to 20 carbon
atoms (preferably from 1 to 6 carbon atoms and more preferably
methyl) in which each of the hydrogen atoms is independently
replaced by a halide (preferably a fluoride or a chloride), alkenyl
of from 2 to 20 carbon atoms, alkynyl of from 1 to 20 carbon atoms,
alkoxy of from 1 to 6 carbon atoms, alkylthio of from 1 to 6 carbon
atoms, C.sub.3-C.sub.8 cycloalkyl, phenyl, halogen, NH.sub.2,
C.sub.1-C.sub.6-alkylamino, C.sub.1-C.sub.6-dialkylamino, and
phenyl which may be substituted with from 1 to 5 halogen atoms
and/or C.sub.1-C.sub.4 alkyl groups. (This definition of "aryl"
also applies to the aryl groups in "aryloxy" and "aralkyl.") Thus,
phenyl may be substituted from 1 to 5 times and naphthyl may be
substituted from 1 to 7 times (preferably, any aryl group, if
substituted, is substituted from 1 to 3 times) with one of the
above substituents. More preferably, "aryl" refers to phenyl,
naphthyl, phenyl substituted from 1 to 5 times with fluorine or
chlorine, and phenyl substituted from 1 to 3 times with a
substituent selected from the group consisting of alkyl of from 1
to 6 carbon atoms, alkoxy of from 1 to 4 carbon atoms and phenyl.
Most preferably, "aryl" refers to phenyl and tolyl.
[0055] Specific examples of vinyl aromatic monomers that may be
used to prepare the (co)polymer include, but are not limited to,
styrene, p-chloromethyl styrene, divinyl benzene, vinyl naphthalene
and divinyl naphthalene. Vinyl halides that may be used to prepare
the graft co(co)polymer include, but are not limited to, vinyl
chloride, p-chloromethylstyrene, vinyl chloroacetate and vinylidene
fluoride. Vinyl esters of carboxylic acids that may be used to
prepare the (co)polymer include, but are not limited to, vinyl
acetate, vinyl butyrate, vinyl 3,4-dimethoxybenzoate and vinyl
benzoate.
[0056] In the context of the present invention, "heterocyclyl"
refers to pyridyl, furyl, pyrrolyl, thienyl, imidazolyl, pyrazolyl,
pyrazinyl, pyrimidinyl, pyridazinyl, pyranyl, indolyl, isoindolyl,
indazolyl, benzofuryl, isobenzofuryl, benzothienyl,
isobenzothienyl, chromenyl, xanthenyl, purinyl, pteridinyl,
quinolyl, isoquinolyl, phthalazinyl, quinazolinyl, quinoxalinyl,
naphthyridinyl, phenoxathiinyl, carbazolyl, cinnolinyl,
phenanthridinyl, acridinyl, 1,10-phenanthrolinyl, phenazinyl,
phenoxazinyl, phenothiazinyl, oxazolyl, thiazolyl, isoxazolyl,
isothiazolyl, and hydrogenated forms thereof known to those in the
art. Preferred heterocyclyl groups include pyridyl, furyl,
pyrrolyl, thienyl, imidazolyl, pyrazolyl, pyrazinyl, pyrimidinyl,
pyridazinyl, pyranyl and indolyl, the most preferred heterocyclyl
group being pyridyl. Accordingly, suitable vinyl heterocycles to be
used as a monomer in the present invention include 2-vinyl
pyridine, 4-vinyl pyridine, 2-vinyl pyrrole, 3-vinyl pyrrole,
2-vinyl oxazole, 4-vinyl oxazole, 5-vinyl oxazole, 2-vinyl
thiazole, 4-vinyl thiazole, 5-vinyl thiazole, 2-vinyl imidazole,
4-vinyl imidazole, 3-vinyl pyrazole, 4-vinyl pyrazole, 3-vinyl
pyridazine, 4-vinyl pyridazine, 3-vinyl isoxazole, 3-vinyl
isothiazoles, 2-vinyl pyrimidine, 4-vinyl pyrimidine, 5-vinyl
pyrimidine, and any vinyl pyrazine, the most preferred being
2-vinyl pyridine. The vinyl heterocycles mentioned above may bear
one or more (preferably 1 or 2) C.sub.1-C.sub.6 alkyl or alkoxy
groups, cyano groups, ester groups or halogen atoms, either on the
vinyl group or the heterocyclyl group, but preferably on the
heterocyclyl group. Further, when the above-mentioned vinyl
heterocycles are unsubstituted, they may contain an N--H group
which may be protected at that position with a conventional
blocking or protecting group, such as a C.sub.1-C.sub.6 alkyl
group, a tris-C.sub.1-C.sub.6 alkylsilyl group, an acyl group of
the formula R.sub.15 CO (where R.sub.15 is alkyl of from 1 to 20
carbon atoms, in which each of the hydrogen atoms may be
independently replaced by halide, preferably fluoride or chloride),
alkenyl of from 2 to 20 carbon atoms (preferably vinyl), alkynyl of
from 2 to 10 carbon atoms (preferably acetylenyl), phenyl which may
be substituted with from 1 to 5 halogen atoms or alkyl groups of
from 1 to 4 carbon atoms, or aralkyl (aryl-substituted alkyl, in
which the aryl group is phenyl or substituted phenyl and the alkyl
group is from 1 to 6 carbon atoms), etc. (This definition of
"heterocyclyl" also applies to the heterocyclyl groups in
"heterocyclyloxy" and "heterocyclic ring.")
[0057] More specifically, preferred monomers include, but are not
limited to, styrene, p-chloromethylstyrene, vinyl chloroacetate,
acrylate and methacrylate esters of C.sub.1-C.sub.20 alcohols,
isobutene, 2-(2-bromopropionoxy) ethyl acrylate, acrylonitrile, and
methacrylonitrile.
[0058] As used herein and in the claims, by "allylic monomer(s)" is
meant monomers containing substituted and/or unsubstituted allylic
functionality, i.e., one or more radicals represented by the
following general formula XVI,
H.sub.2C.dbd.C(R.sub.16)--CH.sub.2-- (XVI)
[0059] where R.sub.16 is hydrogen, halogen or a C.sub.1 to C.sub.4
alkyl group. Most commonly, R.sub.16 is hydrogen or methyl and
consequently general formula XVI represents the unsubstituted
(meth)allyl radical. Examples of allylic monomers may each
independently be residues of, but are not limited to, (meth)allyl
ethers, such as methyl (meth)allyl ether and (meth)allyl glycidyl
ether; allyl esters of carboxylic acids, such as (meth)allyl
acetate, (meth)allyl butyrate, (meth)allyl 3,4-dimethoxybenzoate
and (meth)allyl benzoate.
[0060] Other ethylenically unsaturated radically polymerizable
monomers that may be used to prepare the copolymer include, but are
not limited to: cyclic anhydrides, e.g., maleic anhydride,
1-cyclopentene-1,2-dicarbo- xylic anhydride and itaconic anhydride;
esters of acids that are unsaturated but do not have
.alpha.,.beta.-ethylenic unsaturation, e.g., methyl ester of
undecylenic acid; diesters of ethylenically unsaturated dibasic
acids, e.g., di(C.sub.1-C.sub.4 alkyl) ethyl maleates; maleimide
and N-substituted maleimides.
[0061] In an embodiment of the present invention, the ethylenically
unsaturated monomers include a hydrophobic residue of a monomer
selected from oxirane functional monomer reacted with a carboxylic
acid selected from the group consisting of aromatic carboxylic
acids, polycyclic aromatic carboxylic acids, aliphatic carboxylic
acids having from 6 to 20 carbon atoms and mixtures thereof:
C.sub.6-C.sub.20 alkyl (meth)acrylates, e.g., including those as
previously recited herein; aromatic (meth)acrylates, e.g., phenyl
(meth)acrylate, p-nitrophenyl (meth)acrylate and benzyl
(meth)acrylate; polycyclicaromatic (meth)acrylates, e.g.,
2-naphthyl (meth)acrylate; vinyl esters of carboxylic acids, e.g.,
hexanoic acid vinyl ester and decanoic acid vinyl ester;
N,N-di(C.sub.1-C.sub.8 alkyl) (meth)acrylamides; maleimide;
N-(C.sub.1-C.sub.20 alkyl) maleimides; N-(C.sub.3-C.sub.8
cycloalkyl) maleimides; N-(aryl) maleimides; and mixtures thereof.
Examples of N-substituted maleimides include, but are not limited
to, N-(C.sub.1-C.sub.20 linear or branched alkyl).maleimides, e.g.,
N-methyl maleimide, N-tertiary-butyl maleimide, N-octyl maleimide
and N-icosane maleimide; N- (C.sub.3-C.sub.8 cycloalkyl)
maleimides, e.g., N-cyclohexyl maleimide; and N-(aryl) maleimides,
e.g., N-phenyl maleimide, N-(C.sub.1-C.sub.9 linear or branched
alkyl substituted phenyl) maleimide, N-benzyl maleimide and
N-(C.sub.1-C.sub.9 linear or branched alkyl substituted benzyl)
maleimide.
[0062] The oxirane functional monomer or its residue that is
reacted with a carboxylic acid, may be selected from, for example,
glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate,
2-(3,4-epoxycyclohexyl)ethyl (meth)acrylate, allyl glycidyl ether
and mixtures thereof. Examples of carboxylic acids that may be
reacted with the oxirane functional monomer or its residue include,
but are not limited to, para-nitrobenzoic acid, hexanoic acid,
2-ethyl hexanoic acid, decanoic acid, undecanoic acid and mixtures
thereof.
[0063] The monomer containing at least one polar group may be
present in an amount up to 5 wt % by weight based on the total
amount of monomers. A preferred amount of the monomer containing at
least one polar group is 0.01 to 5 wt %; the most preferred amount
is 0.1 to 3 wt % based on the total amount of monomers.
[0064] The copolymer of the present invention may be prepared by
any technique known in the art. For example, the copolymer may be
prepared by conventional free radical polymerization methods using
thermal initiators such as peroxides or diazzonium or "azo"
containing compounds. Conventional free radical polymerizations may
also be accomplished by art recognized methods of using
oxidation-reduction reactions of, for example persulfate with
bisulfite or various transition metals.
[0065] A preferred method of preparing the copolymer of the present
invention is by controlled radical polymerization. As used herein
and in the claims, the term "controlled radical polymerization,"
and related terms, e.g., "living radical. polymerization," refer to
those methods of radical polymerization that provide control over
the molecular weight, molecular weight distribution, polydispersity
and polymer chain architecture. A controlled or living radical
polymerization is also described as a chain-growth polymerization
that propagates with essentially no chain transfer and essentially
no chain termination. The number of living polymer chains formed
during a controlled radical polymerization is often nearly equal to
the number of initiators present at the beginning of the reaction.
Each living polymer chain typically contains a residue of the
initiator at what is commonly referred to as its tail, and a
residue of the radically transferable group at what is commonly
referred to as its head.
[0066] In an embodiment of the present invention, the copolymer is
prepared by atom transfer radical polymerization (ATRP). The ATRP
process comprises: (co)polymerizing one or more ethylenically
unsaturated polymerizable monomers in the presence of a specific
initiation system; forming a (co)polymer; and isolating the formed
(co)polymer.
[0067] In preparing the copolymer of the present invention by ATRP,
the initiator may be selected from linear or branched aliphatic
compounds, cycloaliphatic compounds, aromatic compounds, polycyclic
aromatic compounds, heterocyclic compounds, sulfonyl compounds,
sulfenyl compounds, esters of carboxylic acids, polymeric compounds
and mixtures thereof, each having at least one radically
transferable group, which is typically a halo group. The initiator
may also be substituted with functional groups such as oxyranyl
groups, which include glycidyl groups. Additional useful initiators
and the various radically transferable groups that may be
associated with them (cyano, cyanato, thiocyanato, and azide
groups, for example) are described in U.S. Pat. No. 5,807,937 at
column 17, line 4 through column 18, line 28.
[0068] Polymeric compounds (including oligomeric compounds) having
radically transferable groups may be used as ATRP initiators, and
are herein referred to as "macroinitiators". Examples of
macroinitiators include, but are not limited to, polystyrene
prepared by cationic polymerization and having a terminal halide
(chloride, for example), and a polymer of 2-(2-bromopropionoxy)
ethyl acrylate and one or more alkyl (meth)acrylates (butyl
acrylate, for example) prepared by conventional non-living radical
polymerization. Macroinitiators can be used in the ATRP process to
prepare graft polymers, such as grafted copolymers and comb
copolymers. A further discussion of macroinitiators is found in
U.S. Pat. No. 5,789,487 at column 13, line 27 through column 18,
line 58.
[0069] Preferably, the ATRP initiator may be selected from
halomethane, methylenedihalide, haloform, carbon tetrahalide
(carbon tetrachloride, for example), 1-halo-2,3-epoxypropane,
methanesulfonyl halide, p-toluenesulfonyl halide, methanesulfenyl
halide, p-toluenesulfenyl halide, 1-phenylethyl halide,
C.sub.1-C.sub.6-alkyl ester of 2-halo-C.sub.1-C.sub.6-carboxylic
acid, p-halomethylstyrene, monohexakis
(.alpha.-halo-C.sub.1-C.sub.6-alkyl) benzene,
diethyl-2-halo-2-methyl malonate and mixtures thereof. Particularly
preferred ATRP initiators are diethyl-2-bromo-2-methyl malonate and
p-toluenesulfonyl chloride.
[0070] Although the prior art teaches the specific use of
halogenated hydrocarbons as preferred initiators for ATRP
processes, it has been found as part of the present invention that
when fluorocarbon ester (meth)acrylates are used, the C--F bond is
too strong and the fluorine atoms, although halogens, do not
participate as radically transferable groups in the ATRP process.
These monomers are further distinguished from other halogenated
monomers in their resistance to photodegradation.
[0071] Catalysts that may be used in the ATRP preparation of the
copolymer of the present invention include any transition metal
compound that can participate in a redox cycle with the initiator
and the growing polymer chain. It is preferred that the transition
metal compound not form direct carbon-metal bonds with the polymer
chain. Transition metal catalysts useful in the present invention
may be represented by the following formula XVII:
TM.sup.n+X.sub.n (XVII)
[0072] where TM is the transition metal, n is the formal charge on
the transition metal having a value of from 0 to 7, and X is a
counterion or covalently bonded component. Examples of the
transition metal include, but are not limited to, Cu, Fe, Au, Ag,
Hg, Pd, Pt, Co, Mn, Ru, Mo, Nb and Zn. Examples of X include, but
are not limited to, halide, hydroxy, oxygen,
C.sub.1-C.sub.6-alkoxy, cyano, cyanato, thiocyanato and azido. A
preferred transition metal is Cu(I) and X is preferably halide,
e.g., chloride. Accordingly, a preferred class of transition metal
catalysts are the copper halides, e.g., Cu(I)Cl. It is also
preferred that the transition metal catalyst contain a small
amount, e.g., 1 mole percent, of a redox conjugate, for example,
Cu(II)Cl.sub.2 when Cu(I)Cl is used. Additional catalysts useful in
preparing the copolymer are described in U.S. Pat. No. 5,807,937 at
column 18, lines 29 through 56. Redox conjugates are described in
further detail in U.S. Pat. No. 5,807,937 at column 11, line 1
through column 13, line 38.
[0073] Ligands that may be used in the ATRP preparation of the
copolymer include, but are not limited to, compounds having one or
more nitrogen, oxygen, phosphorus and/or sulfur atoms, which can
coordinate to the transition metal catalyst compound, e.g., through
sigma and/or pi bonds. Classes of useful ligands include, but are
not limited to, unsubstituted and substituted pyridines and
bipyridines; porphyrins; cryptands; crown ethers; e.g., 18-crown-6;
polyamines, e.g., ethylenediamine; glycols, e.g., alkylene glycols,
such as ethylene glycol; carbon monoxide; and coordinating
monomers, e.g.,. styrene, acrylonitrile and hydroxyalkyl
(meth)acrylates. As used herein and in the claims, the term
"(meth)acrylate" and similar terms refer to acrylates,
methacrylates, and mixtures of acrylates and methacrylates. A
preferred class of ligands is the substituted bipyridines, e.g.,
4,4'-dialkyl-bipyridyls. Additional ligands that may be used in
preparing the (co)polymer are described in U.S. Pat. No. 5,807,937
at column 18, line 57 through column 21, line 43.
[0074] The initiator includes one or more halide-containing
initiation sites that are primarily connected by aliphatic carbons.
The connecting aliphatic carbons may include aromatic residues.
However, to avoid susceptibility to UV degradation, aromatic
moieties are generally avoided. The avoidance of aromatic moieties
also isolates each. Typically, the connecting carbons are aliphatic
(free from aromatic moieties). The initiator sites are also
preferably "symmetrical". By "symmetrical" it is meant that the
K.sub.i (initiation constant) for each initiation site and
typically the K.sub.p (propagation constant) are substantially the
same. By "isolated" it is meant that the K.sub.i and K.sub.p for
each initiation site are not affected substantially by the
initiation and propagation of polymerization on a second initiation
site on the same initiator.
[0075] In preparing the copolymer by ATRP methods, the molar ratio
of transition metal compound to initiator is typically in the range
of 10.sup.-4:1 to 10:1, for example, 0.1:1 to 5:1. The molar ratio
of ligand to transition metal compound is typically within the
range of 0.1:1 to 100:1, for example, 0.2:1 to 10:1.
[0076] The copolymer may be prepared in the absence of solvent,
i.e., by means of a bulk polymerization process. Generally, the
copolymer is prepared in the presence of a solvent, typically an
organic solvent. Classes of useful organic solvents include, but
are not limited to, esters of carboxylic acids, ethers, cyclic
ethers, C.sub.5-C.sub.10 alkanes, C.sub.5-C.sub.8 cycloalkanes,
aromatic hydrocarbon solvents, amides, nitrites, sulfoxides,
sulfones and mixtures thereof. Supercritical solvents, such as
CO.sub.2, C.sub.1-C.sub.4 alkanes and fluorocarbons, may also be
employed. A preferred class of solvents is the aromatic hydrocarbon
solvents, particularly preferred examples of which are xylene,
toluene, and mixed aromatic solvents such as those commercially
available from Exxon Chemical America under the trademark SOLVESSO.
Additional solvents are described in further detail in U.S. Pat.
No. 5,807,937 at column 21, line 44 through column 22, line 54.
[0077] The ATRP preparation of the copolymer is typically conducted
at a reaction temperature within the range of 25.degree. C. to
140.degree. C., preferably from 50.degree. C. to 100.degree. C.,
and a pressure within the range of 1 to 100 atmospheres, usually at
ambient pressure. The atom transfer radical polymerization is
typically completed in less than 24 hours, preferably between 1 and
8 hours.
[0078] The ATRP transition metal catalyst and its associated ligand
are typically separated or removed from the copolymer product prior
to its use. Removal of the ATRP catalyst may be achieved using
known methods, including, for example, adding a catalyst binding
agent to the mixture of the copolymer, solvent and catalyst,
followed by filtering. Examples of suitable catalyst binding agents
include, for example, alumina, silica, clay or a combination
thereof. A mixture of the copolymer, solvent and ATRP catalyst may
be passed through a bed of catalyst binding agent. Alternatively,
the ATRP catalyst may be oxidized in situ, the oxidized residue of
the catalyst being retained in the copolymer.
[0079] The copolymers of the present invention include a variety of
structures, depending upon the structure of the initiator, the
monomers used in propagating the copolymer, the reaction conditions
and the method of termination of the polymerization process. The
copolymers of the present invention may have star-like structures
when the copolymers are produced by propagating a polymer chain on
the above-described poly-functional initiator (three or more
initiation sites). Linear copolymers can be prepared through the
use of-mono- or di-functional initiators.
[0080] The initiators may include active hydrogen-containing groups
to permit crosslinking of the initiator by known crosslinking
methods. The initiator may include other functionality, such as an
ionic group or a group that can be converted into an ionic group,
such as a quaternary amine group or a sulfonium group. An ionic
group-containing copolymer prepared in such a manner can be useful
as a component of an electrodepositable film-forming composition
for use in preparing a coating layer on an electroconductive
substrate. The initiator may further contain an active group that
permits grafting of other groups to the copolymer, such as polymer
chains that cannot be prepared by a controlled radical
polymerization process. An example of such a chain is a
polyoxyalkylene chain, which may be useful in solubilizing the
copolymer, depending upon the intended use for the copolymer.
[0081] The choice of monomers used in preparing the copolymer also
is an important factor in determining the structure of the
copolymer. Gradient polymers can be produced by chain propagation
with a sequence of different monomers. The use of hydrophilic
monomers (i.e., a poly(alkylene glycol) (meth)acrylate or
hydrophobic monomers, i.e., an alkyl (meth)acrylate) will dictate
the hydrophobicity and hydrophilicity of defined portions of the
copolymer structure. The use of active hydrogen-containing
monomers, i.e., a hydroxyalkyl (meth)acrylate or a
(meth)acrylamide, will dictate the reactivity of portions of the
(co)polymer to crosslinkers and/or other co-reactive
group-containing materials.
[0082] As described above, the copolymer may have nonionic
moieties, ionic moieties and combinations thereof. In an embodiment
of the present invention, the ethylenically unsaturated monomers
can be selected from, for example, poly(alkylene glycol)
(meth)acrylates; C.sub.1-C.sub.4 alkoxy poly(alkylene glycol)
(meth)acrylates; hydroxyalkyl (meth)acrylates having from 2 to 4
carbon atoms in the alkyl group; N-(hydroxy-C.sub.1-C.sub.4 alkyl)
(meth)acrylamides; e.g., N-hydroxymethyl (meth)acrylamide and
N-(2-hydroxyethyl) (meth)acrylamide; N,N-di-(hydroxy
C.sub.1-C.sub.4 alkyl) (meth)acrylamides (e.g.,
N,N-di(2-hydroxyethyl) (meth)acrylamide); carboxylic acid
functional monomers; salts of carboxylic acid functional monomers;
amine functional monomers; salts of amine functional monomers; and
mixtures thereof.
[0083] Poly(alkylene glycol) (meth)acrylates and C.sub.1-C.sub.4
alkoxy poly(alkylene glycol) (meth)acrylates are prepared by known
methods. For example, (meth)acrylic acid or hydroxyalkyl
(meth)acrylate, e.g., 2-hydroxyethyl (meth)acrylate, may be reacted
with one or more alkylene oxides, e.g., ethylene oxide, propylene
oxide and butylene oxide. Alternatively, an alkyl (meth)acrylate
may be transesterified with a C.sub.1-C.sub.4 alkoxy poly(alkylene
glycol), e.g., methoxy poly(ethylene glycol). Examples of
poly(alkylene glycol) (meth)acrylates and C.sub.1-C.sub.4 alkoxy
poly(alkylene glycol) (meth)acrylates include poly(ethylene glycol)
(meth)acrylate and methoxy poly(ethylene glycol) (meth)acrylate,
the poly(ethylene glycol) moiety of each having a molecular weight
of from 100 to 800. An example of a commercially available
C.sub.1-C.sub.4 alkoxy poly(alkylene glycol) (meth)acrylate is
methoxy poly(ethylene glycol) 550 methacrylate monomer from
Sartomer Company, Inc. Preferred hydroxy functional monomer are
hydroxyalkyl (meth)acrylates having from 2 to 20 carbon atoms in
the alkyl group; epoxide functional ethylenically unsaturated
radically polymerizable monomers, which are hydrolyzed;
hydroxyalkyl (meth)acrylates having from 2 to 20 carbon atoms in
the alkyl group, which are reacted with a lactone; beta-hydroxy
ester functional (meth)acrylates, which are the reaction product of
(i) (meth)acrylic acid and a glycidyl ester of a saturated
monocarboxylic acid having from 4 to 26 carbon atoms, or (ii)
glycidyl (meth)acrylate and a saturated monocarboxylic-acid having
from 4 to 26 carbon atoms; and mixtures thereof. Examples of
carboxylic acid functional ethylenically unsaturated monomers
include, but are not limited to, (meth)acrylic acid, maleic acid,
and fumaric acid. The monomer may be a residue of a precursor of a
carboxylic acid functional monomer that is converted to a
carboxylic acid residue after completion of the controlled radical
(co)polymerization, e.g., maleic anhydride, di(C.sub.1-C.sub.4
alkyl) maleates and C.sub.1-C.sub.4 alkyl (meth)acrylates. For
example, residues of maleic anhydride can be converted to diacid
residues, ester/acid residues or amide/acid residues by
art-recognized methods. Residues of C.sub.1-C.sub.4 alkyl
(meth)acrylates, such as t-butyl methacrylate, can be converted to
(meth)acrylic acid residues by art-recognized methods. Salts of
carboxylic acid functional monomers include, for example, salts of
(meth)acrylic acid and primary, secondary or tertiary amines, such
as, butyl amine, dimethyl amine and triethyl amine.
[0084] Amine functional monomers include, for example,
amino(C.sub.2-C.sub.4 alkyl) (meth)acrylates, e.g., 2-aminoethyl
(meth)acrylate, 3-aminopropyl (meth)acrylate and 4-aminobutyl
(meth)acrylate; N-(C.sub.1-C.sub.4 alkyl)amino(C.sub.2-C.sub.4
alkyl) (meth)acrylates, e.g., N-methyl-2-aminoethyl (meth)acrylate;
N,N-di(C.sub.1-C.sub.4 alkyl)amino(C.sub.2-C.sub.4 alkyl)
(meth)acrylates, e.g., N,N-dimethyl-2-aminoethyl (meth)acrylate;
and N,N-di(C.sub.1-C.sub.4 alkyl)aminoethyl (meth)acrylates. The
monomer may also comprise residues of salts of amine-functional
monomers, e.g., salts of those amine functional monomers as recited
previously herein. Salts of the amine functional monomer residues
may be formed by mixing a carboxylic acid, e.g., lactic acid, with
the (co)polymer after completion of controlled radical
(co)polymerization.
[0085] In an embodiment of the present invention, the copolymer can
contain a segment that includes carboxylic acid functional monomers
selected from (meth)acrylic acid, maleic anhydride, maleic acid,
di(C.sub.1-C.sub.4 alkyl) maleates, and mixtures thereof. In a
still further embodiment of the present invention, the (co)polymer
segment is a residue of amine functional monomers selected from
amino(C.sub.2-C.sub.4 alkyl) (meth)acrylates, N-(C.sub.1-C.sub.4
alkyl)amino(C.sub.2-C.sub.4 alkyl) (meth)acrylates,
N,N-di(C.sub.1-C.sub.4 alkyl)amino(C.sub.2-C.sub.- 4 alkyl)
(meth)acrylates and mixtures thereof.
[0086] The copolymer also may contain a segment that contains
cationic moieties selected from ammonium, sulphonium and
phosphonium. Ammonium, sulphonium and phosphonium moieties may be
introduced into the copolymer by means known to the skilled
artisan. For example, when the copolymer contains a residue of
N,N-dimethyl-2-aminoethyl (meth)acrylate, the N,N-dimethylamino
moieties may be converted to ammonium moieties by mixing an acid,
e.g., lactic acid, with the polymer.
[0087] When the segment of the copolymer contains residues of
oxirane functional monomers, such as glycidyl (meth)acrylate, the
oxirane groups may be used to introduce sulphonium or phosphonium
moieties into the polymer. Sulphonium moieties may be introduced
into the polymer by reaction of the oxirane groups with
thiodiethanol in the presence of an acid, such as lactic acid.
Reaction of the oxirane groups with a phosphine, e.g., triphenyl
phosphine or tributyl phosphine, in the presence of an acid, such
as lactic acid, results in the introduction of phosphonium moieties
into the graft (co)polymer.
[0088] The preferred architecture of the present invention is a
gradient architecture. Gradient architecture refers to a sequence
of different monomer residues that changes gradually in a
systematic and predictable manner along the polymer backbone as
shown in structure XVIII.
(XVIII) Gradient Architecture
[0089] --(MMA-MMA-MMA-FMA-MMA-MMA-FMA-FMA-MMA-FMA-FMA-FMA)--
[0090] where MMA represents methylmethacrylate and FMA represents a
fluoroalkyl methacrylate.
[0091] The order in which monomer residues occur along the backbone
of the copolymer typically is determined by the order in which the
corresponding monomers are fed into the vessel in which the
controlled radical polymerization is conducted. For example, the
monomers that are incorporated as residues at the tail end of the
copolymer are generally fed into the reaction vessel prior to those
monomers that are incorporated at the head end.
[0092] During formation of the gradient polymer, if more than one
monomer is fed into the reaction vessel at a time, the relative
reactivities of the monomers typically determine the order in which
they are incorporated into the living polymer chain.
[0093] One manner in which a gradient copolymer of the present
invention can be prepared is to add the other polymerizable
ethylenically unsaturated monomer(s) to a reaction vessel
containing an ATRP initiator system as described above. The low
surface tension (meth)acrylate monomer is then fed to the reaction
vessel over a period of time. As the other polymerizable
ethylenically unsaturated monomer(s) are consumed, the relative
concentration of the low surface tension (meth)acrylate monomer
will increase. The composition and architecture along the copolymer
will reflect the changing relative concentrations of the monomers
present over time, i.e., the head end will be rich in the other
polymerizable ethylenically unsaturated monomer(s) and the tail end
of the copolymer will be rich in the low surface tension
(meth)acrylate monomer.
[0094] In another embodiment, the relative reactivities, or
reactivity ratios, of the other polymerizable ethylenically
unsaturated monomer(s) and the low surface tension (meth)acrylate
monomer can be used to control the gradient copolymer composition.
In this method, all of the monomers are added or fed over time to a
reaction vessel containing an ATRP initiator system as described
above. The copolymer architecture will be determined by relative
monomer reactivities. The more reactive monomers will predominate
initially and as the relative concentration of less reactive
monomers increases with the depletion of the more reactive
monomers, they will incorporate more readily into the living ATRP
copolymer. The net effect of this approach is to create a tail end
rich in reactive monomer(s) and a head end rich in less reactive
monomer(s).
[0095] The copolymer typically has a number average molecular
weight (Mn) of from 500 to 1,000,000, preferably from 1,000 to
100,000 and most preferably from 1,500 to 50,000, as determined by
gel permeation chromatography using polystyrene standards. The
polydispersity index, i.e., weight average molecular weight (Mw)
divided by the number average molecular. weight (Mn) of the
copolymer-typically are less-than 2.5, preferably less than 2.0 and
most preferably less than 1.5.
[0096] When the copolymer is a gradient copolymer made using
controlled radical polymerization, a residue of the initiator used
in the preparation of the gradient copolymer, free of the radically
transferable group of the initiator, is part of the gradient
copolymer as shown in structure XIX:
.phi.-O-O-O-H-H-H-L-O-O-H-H-L-L-O-H-L-L-L-O-L-L-L-L-T (XIX)
[0097] Tail End Head End
[0098] where .phi. represents the initiator residue, O represents
the other polymerizable ethylenically unsaturated monomer, H
represents a third monomer, L represents a low surface tension
(meth)acrylate monomer and T represents the radically transferable
group.
[0099] The copolymer made using ATRP may also have other
architectures such as a block copolymer, represented by formula XX
or a random copolymer, represented by formula XXI:
--[--(O).sub.p--(L).sub.q--].sub.x--T (XX)
--[(O).sub.p(L).sub.q]--T (XXI)
[0100] where .phi., O, L and T are as described above, p and q
represent average numbers of monomer residues occurring in a random
copolymer as in formula XX or in a block of monomer residues in a
block copolymer as in formula XXI. The number of block sequences in
a block copolymer is defined by x. In general, p and q are integers
representing the respective average number of monomer residues in a
copolymer. The number of other monomers, p, can be from 1 to 1,000,
preferably from 2 to 500 and most preferably from 3 to 250. The
number of low surface tension (meth)acrylate monomers, L, can be
from 1 to 200, preferably from 1 to 100 and most preferably from 1
to 50.
[0101] In a preferred embodiment, the controlled radical
polymerization method is ATRP using an initiator with a radically
transferable group. The radically transferable group is typically a
halide group, preferably a bromide group. The halide residue may be
(a) left on the copolymer, (b) removed or (c) chemically converted
to another moiety. The radically transferable group may be removed
by substitution with a nucleophilic compound, e.g., an alkali metal
alkoxylate. Graft-group-terminal halogens can be removed from the
copolymer by means of a mild dehalogenation reaction. The reaction
is typically performed as a post-reaction after the graft
(co)polymer has been formed, and in the presence of at least an
ATRP catalyst. Preferably, the dehalogenation post-reaction is
performed in the presence of both an ATRP catalyst and its
associated ligand.
[0102] The copolymers of the present invention can be used as,
without limitation, film-forming compositions, rheology modifiers,
pigment or ink dispersants, gel matrices and molding resins. The
fields of use of the copolymers are varied and include, without
limitation, articles and industrial uses, such as in the automotive
industry, medical uses, such as in the production of novel films
and matrices for use in bioengineering and tissue engineering,
pharmaceutical uses, such as in the production of drug delivery
matrices and chemical industry uses, such as in the preparation of
gels for product separation and purification, and in chemical and
biological research, such as in tailored gel matrices for reagent
purification.
[0103] When the copolymer of the present invention is a gradient
copolymer made using ATRP, it will contain a residue from the
initiator, .phi.. Depending on the number of radically transferable
groups on the initiator, the location of initiator residue .phi.
will vary. When one radically transferable group is present in the
initiator, structure XXII may result. When two radically
transferable groups are present in the initiator, structure XXIII
may result.
.phi.-O-O-O-H-H-H-L-O-O-H-H-L-L-O-H--L-L-L-O-L-L-L-L-T (XXII)
[0104] Tail End Head End
T-L-L-L-O-L-L-O-O-L-O-O-O-.phi.O-O-O-L--O-O-L-L-O-L-L-L-T
(XXIII)
[0105] Tail End Head End
[0106] in which O, L and H are as defined above, .phi. is or is
derived from the residue of the initiator free of radically
transferable groups and T is or is derived from the radically
transferable group of the initiator.
[0107] When the copolymer of the present invention is a gradient
copolymer, it may be additionally generally described by the
following representative polymer chain structure XXIV:
--(M).sub.s-a--(L).sub.a--(M).sub.s-2a(L).sub.2a--(M).sub.s-3a--(L).sub.3a-
--. . . --(M).sub.s-na--(L).sub.na-- (XXIV)
[0108] where s is an integer from 1 to 300, a is an integer from 1
to 10, n is an integer from 1 to 299 such that the relationship
s-na is greater than or equal to zero, M is an other radically
polymerizable ethylenically unsaturated monomer and L is a
radically polymerizable low surface tension (meth)acrylate monomer.
M may represent a group of one or more radically polymerizable
ethylenically unsaturated monomers.
[0109] When the gradient copolymer of the present invention is
prepared by ATRP in the presence of an initiator having a radically
transferable group, the gradient copolymer may be further described
as having the following structure XXV:
.phi.--[--(M).sub.s-a--(L).sub.a--(M).sub.s-2a--(L).sub.2a--(M).sub.s-3a---
(L).sub.3a--. . . --(M).sub.s-na--(L).sub.na--T].sub.z (XX)
[0110] in which s is an integer from 1 to 300, preferably from 1 to
200, more preferably from 1 to 100 and most preferably from 1 to
50; a is an integer from 1 to 50, preferably from 1 to 40, more
preferably from 1 to 25 and most preferably from 1 to 10; n is an
integer from 1 to 299, preferably from 1 to 199, more preferably
from 1 to 99, and most preferably from 1 to 49; such that the
relationship s-na is greater than or equal to zero; M represents an
other radically polymerizable ethylenically unsaturated monomer; L
represents a radically polymerizable low surface tension
(meth)acrylate monomer; .phi. is or is derived from the residue of
the initiator free of radically transferable groups; T is or is
derived from the radically transferable group of the initiator; z
is at least equal to the number of radically transferable groups of
the initiator and is independently for each structure at least 1,
for example from 1 to 100, preferably from 1 to 50, more preferably
from 1 to 10 and most preferably from.1 to 5.
[0111] With reference to polymer chain structures XXIV and XXV, M
may optionally include residues having a minor amount of at least
one hydroxy functional ethylenically unsaturated radically
polymerizable monomer, such as hydroxypropyl (meth)acrylate, in
which s and p are each independently from 1 to 100 and q is
independently from 0 to 100. The hydroxy functional ethylenically
unsaturated radically polymerizable monomer is as described
previously herein.
[0112] In a further embodiment of the gradient copolymer example,
the gradient copolymer can be a gradient block copolymer, wherein
it includes a gradient block and a block that includes the low
surface tension (meth)acrylate monomer as described by general
formula XXVI:
.phi.--{[--(M).sub.s-a--(E).sub.a--. . .
--(M).sub.s-na--(E).sub.na--]--[L- ].sub.m--T}.sub.z (XXVI)
[0113] where .phi., M, L, T, s, n and z are as defined above; a is
an integer from 1 to 200, preferably from 1 to 100, more preferably
from 1 to 50 and most preferably from 1 to 25; E is a third
polymerizable ethylenically unsaturated monomer and m is an integer
from 1 to 50, preferably from 1 to 40, more preferably from 1 to 25
and most preferably from 1 to 10.
[0114] In a preferred embodiment, monomer composition E has a
moderate surface tension effect. Any monomer that has mild surface
tension altering properties can be used in monomer composition E.
Preferred moderate surface tension monomers include, but are not
limited to, branched alkyl (meth)acrylates such as 2-ethylhexyl
(meth)acrylate, ethoxylated (meth)acrylates and propoxylated
(meth)acrylates. In addition to the gradient copolymer including
moderate surface tension monomer E described above, such monomers
can be used in the present invention in random and block copolymers
as described in formulas XXVII and XXVIII:
--[--(O).sub.p--(E).sub.s--(L).sub.q--].sub.x-- (XXVII)
--[(O).sub.p--(E).sub.s(L).sub.q]-- (XXVIII)
[0115] where O, E, L, p, q and x areas previously defined and s is
an integer describing the number residues of moderate surface
tension monomer E in a random copolymer or in a block of residues
in a block copolymer and can be from 1 to 1,000, preferably from 1
to 500 and most preferably from 1 to 100.
[0116] Symbol T of general formulas XIX, XX, XXI, XXII, XXIII, XXV
and XXVI is or is derived from the radically transferable group of
the initiator. For example, when the gradient copolymer is prepared
in the presence of diethyl-2-bromo-2-methyl malonate, T may be the
radically transferable bromo group.
[0117] The radically transferable group may optionally be (a)
removed or (b) chemically converted to another moiety. In either of
(a) or (b), the symbol T is considered herein to be derived from
the radically transferable group of the initiator. The radically
transferable group may be removed by substitution with a
nucleophilic compound, such as an alkali metal alkoxylate. However,
in the present invention, it is desirable that the method by which
the radically transferable group is either removed or chemically
converted also be relatively mild.
[0118] In an embodiment of the present invention, when the
radically transferable group is a halogen, the halogen can be
removed by means of a mild dehalogenation reaction. The reaction is
typically performed as a post-reaction after the polymer has been
formed, and in the presence of at least an ATRP catalyst.
Preferably, the dehalogenation post-reaction is performed in the
presence of both an ATRP catalyst and its associated ligand.
[0119] The mild dehalogenation reaction is performed by contacting
the halogen terminated copolymer of the present invention with one
or more ethylenically unsaturated compounds, which are not readily
radically polymerizable under at least a portion of the spectrum of
conditions under which ATRP polymerizations are performed,
hereinafter referred to as "limited radically polymerizable
ethylenically unsaturated monomers" (LRPEU compound). As used
herein, by "halogen terminated" and similar terms is meant to be
inclusive also of pendant halogens, such as those that would be
present in branched, comb and star polymers.
[0120] Not intending to be bound by any theory, it is believed,
based on the evidence at hand, that the reaction between the
halogen terminated copolymer and one or more LRPEU compounds
results in (1) removal of the terminal halogen group, and (2) the
addition of at least one carbon-carbon double bond where the
terminal carbon-halogen bond is broken.
[0121] The dehalogenation reaction is typically conducted at a
temperature of from 0.degree. C. to 200.degree. C., preferably from
0.degree. C. to 160.degree. C. at a pressure in the range of 0.1 to
100 atmospheres, preferably from 0.1 to 50 atmospheres. The
reaction is also typically performed in less than 24 hours,
preferably between 1 and 8 hours. While the LRPEU compound may be
added in less than a stoichiometric amount, it is preferably added
in at least a stoichiometric amount relative to the number of moles
of terminal halogen present in the copolymer. When added in excess
of a stoichiometric amount, the LRPEU compound is typically present
in an amount of no greater than 5 mole percent, preferably 1 to 3
mole percent in excess of the total moles of terminal halogen.
[0122] Limited radically polymerizable ethylenically unsaturated
compounds useful for dehalogenating the copolymer of the
composition of the present invention under mild conditions include
those represented by the general formula XXIX: 9
[0123] In general formula XXIX, R.sub.17 and R.sub.18 can be the
same or different organic groups such as alkyl groups having from 1
to 4 carbon atoms; aryl groups; alkoxy groups; ester groups; alkyl
sulfur groups; acyloxy groups; and nitrogen-containing alkyl groups
where at least one of the R.sub.17 and R.sub.18 groups is an organo
group while the other can be an organo group or hydrogen. For
instance, when one of R.sub.17 and R.sub.18 is an alkyl group, the
other can be an alkyl, aryl, acyloxy, alkoxy, arenes,
sulfur-containing alkyl group, or nitrogen-containing alkyl and/or
nitrogen-containing aryl groups. The R.sub.19 groups can be the
same or different groups selected from hydrogen or lower alkyl
selected such that the reaction between the terminal halogen or the
copolymer and the LRPEU compound is not prevented. Also an R.sub.19
group can be joined to the R.sub.17 and/or the R.sub.18 groups to
form a cyclic compound.
[0124] It is preferred that the LPREU compound be free of halogen
groups. Examples of suitable LRPEU compounds include, but are not
limited to, 1,1-dimethylethylene, 1,1-diphenylethylene, isopropenyl
acetate, alpha-methyl styrene, 1,1-dialkoxy olefin and mixtures
thereof. Additional examples include dimethyl itaconate and
diisobutene (2,4,4-trimethyl-1-pentene).
[0125] For purposes of illustration, the reaction between halogen
terminated copolymer and LRPEU compound, such as alpha-methyl
styrene, is summarized in the following general scheme 1. 10
[0126] In general scheme 1, P--X represents the halogen terminated
copolymer.
[0127] The copolymers of the present invention are unique in that
they contain the low surface tension (meth)acrylate monomer. This
property can be very useful, for example, when the present
copolymers are used in coating applications. Not wishing to be
bound to a single theory, it is believed that the surface tension
reducing effect of the fluoroalkyl (meth)acrylate blocks of the
copolymer of the present invention provide superior flow control
properties, crater prevention and coating physical properties to
all types of coating compositions. In the case of a gradient
copolymer, it is believed that the head end of the gradient
copolymer, which contains a proportionally higher content of the
low surface tension (meth)acrylate monomers orient at the
coating/air interface, effectively reducing the surface tension of
the coating, thus minimizing surface defects such as waviness and
cratering. The tail end of the gradient copolymer which is
predominantly low surface tension (meth)acrylate monomer deficient
extends into the coating adding strength to the coating and
improving adhesion to the coated substrate. The orientation of the
low surface tension (meth)acrylate rich head end of the gradient
copolymer as described above is not possible with random
copolymers. In a random copolymer, if the fluoroalkyl
(meth)acrylate monomer is present at high enough concentration, the
entire polymer will orient at the coating/air interface. At lower
fluoroalkyl (meth)acrylate monomer concentration, the random
copolymer will simply remain in the coating. Therefore, the dual
properties of coating property improvement and improved adhesion to
the substrate cannot be realized with a random copolymer containing
fluoroalkyl (meth)acrylate monomer.
[0128] Referring to formulas IV and V, when the divalent linking
group Y of formula IV is of sufficient length or the
--(CH.sub.2).sub.m-- group of formula V is of sufficient length,
the copolymer may take on a quasi-comb polymer architecture. In
this situation, the low surface tension functional group (fluorine
or siloxane containing group for example) may be sufficiently
extended from the backbone of the polymer to independently orient
at the coating/air interface, regardless of its position along the
polymer chain, effectively reducing the surface tension of the
coating and minimizing surface defects such as waviness and
cratering. In the quasi-comb copolymer situation, the distance of
extension of the surface tension lowering group away from the
polymer backbone may override polymer architecture considerations
and most copolymer architectures (random, block, gradient, etc.)
may be effective at coating property improvement and improved
coating adhesion to a substrate.
[0129] In the gradient copolymer situation, the gradient copolymer
may be superior to similarly constructed block copolymers, as the
gradient approach provides a gradual rather than an abrupt
copolymer architecture and composition change. The gradual
composition and architecture change in the gradient copolymer
minimizes problems such as phase separation and copolymer
incompatibility.
[0130] In an embodiment of the present invention, the copolymer of
the present invention may be used as a flow control agent in a
thermosetting composition. The thermosetting composition of the
present invention further comprises a non-gelled polymer with
functional groups and a crosslinking agent having at least two
functional groups that are reactive with the functional groups of
the polymer.
[0131] Not wishing to be limited to any one set of functional
groups, there are several examples of co-reactive functional groups
that can be used in the present invention. The functional groups of
the polymer can be, but are not limited to epoxy or oxirane;
carboxylic acid; hydroxy; amide; oxazoline; aceto acetate;
isocyanate; or carbamate. The crosslinking agent has at least two
functional groups that are different than those contained in the
polymer and is co-reactive toward the functional groups of the
polymer and can be, but is not limited to epoxy or oxirane;
carboxylic acid;. hydroxy; polyol; isocyanate; capped isocyanate;
amine; aminoplast and beta-hydroxyalkylamide.
[0132] When the polymer has hydroxyl functionality, examples of
suitable crosslinking agents include aminoplasts containing
methylol and/or methylol ether groups and polyisocyanates.
[0133] Aminoplasts are obtained from the reaction of formaldehyde
with an amine or amide. The most common amines or amides are
melamine, urea, or benzoguanamine, and are preferred. However,
condensates with other amines or amides can be used; for example,
aldehyde condensates of glycoluril, which give a high melting
crystalline product which is useful in powder coatings. While the
aldehyde used is most often formaldehyde, other aldehydes such as
acetaldehyde, crotonaldehyde, and benzaldehyde may be used.
[0134] The aminoplast contains methylol groups and, preferably, at
least a portion of these groups are etherified with an alcohol to
modify the cure response. Any monohydric alcohol may be employed
for this purpose including methanol, ethanol, butanol, isobutanol,
and hexanol.
[0135] Preferably, the aminoplasts which are used are melamine-,
urea-, or benzoguanamine-formaldehyde condensates etherified with
an alcohol containing from one to four carbon atoms.
[0136] Other suitable crosslinking agents for hydroxy functional
polymers include polyisocyanates. The polyisocyanate crosslinking
agent may be a fully capped polyisocyanate with substantially no
free isocyanate groups, or it may contain free isocyanate
functionality. Free isocyanate groups allow for curing of the
composition at temperatures as low as ambient. When the
crosslinking agent contains free isocyanate groups, the
film-forming composition is preferably a two-package composition
(one package comprising the crosslinking agent and the other
comprising the hydroxyl functional polymer) in order to maintain
storage stability.
[0137] The polyisocyanate can be an aliphatic or an aromatic
polyisocyanate or a mixture of the two. Diisocyanates are
preferred, although higher polyisocyanates can be used in place of
or in combination with diisocyanates.
[0138] Examples of suitable aliphatic diisocyanates are straight
chain aliphatic diisocyanates such as 1,4-tetramethylene
diisocyanate and 1,6-hexamethylene diisocyanate. Also,
cycloaliphatic diisocyanates can be employed. Examples include
isophorone diisocyanate and 4,4'-methylene-bis-(cyclohexyl
isocyanate). Examples of suitable aromatic diisocyanates are
p-phenylene diisocyanate, diphenylmethane-4,4'-diisocya- nate and
2,4- or 2,6-toluene diisocyanate. Examples of suitable higher
polyisocyanates are triphenylmethane-4,4',4"-triisocyanate,
1,2,4-benzene triisocyanate and polymethylene polyphenyl
isocyanate. Biurets and isocyanurates of diisocyanates, including
mixtures thereof, such as the isocyanurate of hexamethylene
diisocyanate, the biuret of hexamethylene diisocyanate and the
isocyanurate of isophorone diisocyanate are also suitable.
[0139] Isocyanate prepolymers, for example, reaction products of
polyisocyanates with polyols such as neopentyl glycol and
trimethylol propane or with polymeric polyols such as
polycaprolactone diols and triols (NCO/OH equivalent ratio greater
than one) can also be used.
[0140] Any suitable aliphatic, cycloaliphatic, or aromatic alkyl
monoalcohol or phenolic compound may be used as a capping agent for
the capped polyisocyanate crosslinking agent in the composition of
the present invention including, for example, lower aliphatic
alcohols such as methanol, ethanol, and n-butanol; cycloaliphatic
alcohols such as cyclohexanol; aromatic-alkyl alcohols such as
phenyl carbinol and methylphenyl carbinol; and phenolic compounds
such as phenol itself and substituted phenols wherein the
substituents do not affect coating operations, such as cresol and
nitrophenol. Glycol ethers may also be used as capping agents.
Suitable glycol ethers include ethylene glycol butyl ether,
diethylene glycol butyl ether, ethylene glycol methyl ether and
propylene glycol methyl ether.
[0141] Other suitable capping agents include oximes such as methyl
ethyl ketoxime, acetone oxime and cyclohexanone oxime, lactams such
as epsilon-caprolactam, and amines such as dibutyl amine.
[0142] When the functionality of the polymer is an oxirane or epoxy
group, the crosslinking agent has at least two functional groups
that are reactive with epoxides. The at least two functional groups
are intended to include mixtures of functional groups. The
functional groups that are reactive with epoxides include, but are
not limited to, polyamines, polyamides, polycarboxylic acids,
polyanhydrides, aminoplasts, and polyphenolic compounds.
[0143] Suitable polyamines include, but are not limited to, amine
and amide functional addition polymers and oligomers typically used
in film-forming compositions such as acrylic and vinyl
polymers.
[0144] Suitable polycarboxylic acids include, but are not limited
to dodecanedioic acid, azelaic acid, adipic acid, 1,6-hexanedioic
acid, succinic acid, sebacic acid, maleic acid, citric acid,
itaconic acid, pimelic acid, aconitic acid, carboxylic-acid
terminated polyesters, half-esters formed from reacting an
anhydride with a polyol, carboxylic acid containing polymers such
as acrylic acid and methacrylic acid containing polymers,
polyesters and polyurethanes, fatty diacids and mixtures
thereof.
[0145] Suitable polyanhydrides include addition polymers and
oligomers typically used in film-forming compositions such as
acrylic and vinyl polymers. Examples include, but are not limited
to those described in U.S. Pat. Nos. 4,798,746 and 4,732,790.
[0146] When the polymer has carboxylic acid functionality, the
crosslinking agent is a beta-hydroxyalkylamide, as described
above.
[0147] The crosslinking agent is typically present in the
thermosetting compositions of the present invention in an amount of
at least 10 percent by weight, preferably at least 25 percent by
weight, based on the total resin solids weight of the composition.
The crosslinking agent is also typically present in the composition
in an amount of less than 90 percent by weight, preferably less
than 75 percent by weight, based on the total resin solids weight
of the composition. The amount of crosslinking agent present in the
thermosetting composition of the present invention may range
between any combination of these values, inclusive of the recited
values.
[0148] The equivalent ratio of functional groups in the polymer to
reactive functional groups in the crosslinking agent is typically
within the range of 1:0.5 to 1:1.5, preferably 1:0.8 to 1:1.2.
[0149] Usually, the thermosetting composition will also preferably
contain catalysts to accelerate the cure of the crosslinking agent
with reactive groups on the polymer(s).
[0150] Suitable catalysts for aminoplast cure include acids such as
acid-phosphates and sulfonic acid or a substituted sulfonic acid.
Examples include dodecylbenzene sulfonic acid, paratoluene sulfonic
acid, phenyl acid phosphate, ethylhexyl acid phosphate, and the
like. Suitable catalysts for isocyanate cure include organotin
compounds such as dibutyltin oxide, dioctyltin oxide, dibutyltin
dilaurate, and the like. The catalyst is usually present in an
amount of about 0.05 to about 5.0 percent by weight, preferably
about 0.25 to about 2.0 percent by weight, based on the total
weight of resin solids in the thermosetting composition.
[0151] The thermosetting composition of the present invention is
preferably used as a film-forming (coating) composition, and may
contain adjunct ingredients conventionally used in such
compositions. Optional ingredients such as, for example,
plasticizers, surfactants, thixotropic agents, anti-gassing agents,
organic cosolvents, flow controllers, anti-oxidants, UV light
absorbers and similar additives conventional in the art may be
included in the composition. These ingredients are typically
present at up to about 40% by weight based on the total weight of
resin solids.
[0152] The thermosetting composition of the present invention is
typically a liquid and may be waterborne, but is usually
solventborne. Suitable solvent carriers include the various esters,
ethers, and aromatic solvents, including mixtures thereof, that are
known in the art of coating formulation. The composition typically
has a total solids content of about 40 to about 80 percent by
weight.
[0153] The thermosetting composition of the present invention may
contain color pigments conventionally used in surface coatings and
may be used as a monocoat; that is, a pigmented coating. Suitable
color pigments include, for example, inorganic pigments such as
titanium dioxide, iron oxides, chromium oxide, lead chromate, and
carbon black, and organic pigments such as phthalocyanine blue and
phthalocyanine green. Mixtures of the above-mentioned pigments may
also be used. Suitable metallic pigments include, in particular,
aluminum flake, copper bronze flake and metal oxide coated mica,
nickel flakes, tin flakes, and mixtures thereof.
[0154] In general, the pigment is incorporated into the coating
composition in amounts up to about 80 percent by weight, based on
the total weight of coating solids. The metallic pigment is
employed in amounts of about 0.5 to about 25 percent by weight
based on the total weight of coating solids.
[0155] As stated above, the thermosetting compositions of the
present invention may be used in a method of coating a substrate
comprising applying a thermosetting composition to the substrate,
coalescing the thermosetting composition over the substrate in the
form of a substantially continuous film, and curing the
thermosetting composition.
[0156] The compositions can be applied to various substrates to
which they adhere including wood, metals, glass, and plastic. The
compositions can be applied by conventional means including
brushing, dipping, flow coating, spraying and the like, but they
are most often applied by spraying. The usual spray techniques and
equipment for air spraying and electrostatic spraying and either
manual or automatic methods can be used.
[0157] After application of the composition to the substrate, the
composition is allowed to coalesce to form a substantially
continuous film on the substrate. Typically, the film thickness
will be about 0.01 to about 5 mils (about 0.254 to about 127
microns), preferably about 0.1 to about 2 mils (about 2.54 to about
50.8 microns) in thickness. The film is formed on the surface of
the substrate by driving solvent, i.e., organic solvent and/or
water, out of the film by heating or by an air drying period.
Preferably, the heating will only be for a short period of time,
sufficient to ensure that any subsequently applied coatings can be
applied to the film without dissolving the composition. Suitable
drying conditions will depend on the particular composition, but,
in general, a drying time of from about 1 to 5 minutes at a
temperature of about 68-250.degree. F. (20-121.degree. C.) will be
adequate. More than one coat of the composition may be applied to
develop the optimum appearance. Between coats the previously
applied coat may be flashed; that is, exposed to ambient conditions
for about 1 to 20 minutes.
[0158] The film-forming composition of the present invention is
preferably used as the clear coat layer in a multi-component
composite coating composition such as a "color-plus-clear", coating
system, which includes at least one pigmented or colored base coat
and at least one clear topcoat. In this embodiment, the clear
film-forming composition may include the thermosetting composition
of the present invention.
[0159] The film-forming composition of the-base coat in the
color-plus-clear system can be any of the compositions useful in
coatings applications, particularly automotive applications. The
film-forming composition of the base coat comprises a resinous
binder and a pigment to act as the colorant. Particularly useful
resinous binders are acrylic polymers, polyesters, including
alkyds, and polyurethanes. Polymers prepared using atom transfer
radical polymerization may also be used as resinous binders in the
base coat.
[0160] The base coat compositions may be solventborne or
waterborne. Waterborne base coats in color-plus-clear compositions
are disclosed in U.S. Pat. No. 4,403,003,and the resinous
compositions used in preparing these base coats can be used in the
practice of this invention. Also, waterborne polyurethanes such as
those prepared in accordance with U.S. Pat. No. 4,147,679 can be
used as the resinous binder in the base coat. Further, waterborne
coatings such as those described in U.S. Pat. No. 5,071,904 can be
used as the base coat.
[0161] The base coat contains pigments to give it color. Suitable
pigments include those discussed above. In general, the pigment is
incorporated into the coating composition in amounts of about 1 to
80 percent by weight based on weight of coating solids. Metallic
pigment is employed in amounts of about 0.5 to 25 percent by weight
based on weight of coating solids.
[0162] If desired, the base coat composition may contain additional
materials well known in the art of formulated surface coatings,
including those discussed above. These materials can constitute up
to 40 percent by weight of the total weight of the coating
composition.
[0163] The base coating compositions can be applied to various
substrates to which they adhere by conventional means, but they are
most often applied by spraying. The usual spray techniques and
equipment for air spraying and electrostatic spraying and either
manual or automatic methods can be used.
[0164] During application of the base coat composition to the
substrate, a film of the base coat is formed on the substrate.
Typically, the base coat thickness will be about 0.01 to 5 mils
(0.254 to 127 microns), preferably 0.1 to 2 mils (2.54 to 50.8
microns) in thickness.
[0165] After application of the base coat to the substrate, a film
is formed on the surface of the substrate by driving solvent out of
the base coat film by heating or by an air drying period,
sufficient to ensure that the clear coat can be applied to the base
coat without the former dissolving the base coat composition, yet
insufficient to fully cure the base coat. More than one base coat
and multiple clear coats may be applied to develop the optimum
appearance. Usually between coats, the previously applied coat is
flashed.
[0166] The clear topcoat composition may be applied to the base
coated substrate by any conventional coating technique such as
brushing, spraying, dipping or flowing, but spray applications are
preferred because of superior gloss. Any of the known spraying
techniques may be employed such as compressed air spraying,
electrostatic spraying and either manual or automatic methods.
[0167] After application of the clear coat composition to the base
coat, the coated substrate may be heated to cure the coating
layer(s). In the curing operation, solvents are driven off and the
film-forming materials in the composition are crosslinked. The
heating or curing operation is usually carried out at a temperature
in the range of from at least ambient (in the case of free
polyisocyanate crosslinking agents) to 350.degree. F. (ambient to
177.degree. C.) but, if needed, lower or higher temperatures may be
used as necessary to activate crosslinking mechanisms.
EXAMPLES
Example 1
Synthesis of Gradient Copolymer MMA-gradient-2-EHMA-b-Zonyl.TM.
[0168] The gradient copolymer MMA-gradient-EHMA-b-Zonyl.TM. was
prepared by polymerization the ingredients in Table 1 in Aromatic
100 solvent:
1 TABLE 1 Parts by weight Ingredients (grams) Charge 1 Aromatic 100
300 Copper 0.89 Tris(2-aminoethyl) amine/6BA 8.96
Ethyl-2-bromoisobutyrate 27.30 MMA 196 Charge 2 2-EHMA 777.38
Aromatic 100 100 Charge 3 Aromatic 100 60.90 ZONYL TM fluoromonomer
74.76 2-(perfluoroalkyl)ethyl methacrylate (DuPont)
[0169] Charge 1 was heated in a reaction vessel with agitation at
80.degree. C. and the reaction mixture was held at this temperature
for 1.5 hours. After partial homopolymerization of MMA, charge 2
was continuously added to the reaction vessel for 3 hrs to form a
compositional gradient along the polymer chain. The compositional
gradient was controlled through the use of controlled 2-EHMA
addition based on its reactivity ratio found in the literature
(r.sub.1 MMA=0.86, r.sub.2 EHMA=0.69: Journal of Thermal Analysis,
Vol. 36, pp. 617-628 (1990)). The reaction mixture was held at
80.degree. C. for 3 hours. Charge 3 was added over a period of 15
minutes and the reaction mixture was held at 80.degree. C. for 3
hours. The reaction mixture was cooled and filtered.
[0170] The resultant gradient copolymer had a total solid content
of 70 percent determined at 110.degree. C. for one hour. The
copolymer had a number average molecular weight, Mn=8040 and
polydispersity, Mw/Mn=1.32 (determined by gel permeation
chromatography using polystyrene standards), with a theoretical
Mn=7680.
Example 2
Resistance of Paint to Contamination
[0171] A commercial, solvent-borne, thermosetting clear coat,
DCT5555 (available from PPG;Industries, Inc., Pittsburgh, Pa.) was
deliberately contaminated with a commercial caustic wash solution
typically used in cleaning transport containers for coatings and
known to induce cratering. The polymer of example 1 was added to a
portion of this clearcoat at a level of 0.1% by weight and
thoroughly mixed by stirring.
[0172] The clear coat treated (with the polymer of example 1). and
an untreated clear coat were applied to sixteen 12".times.18"
commercially available electrocoated steel panels using an ESTA
bell. The clear coat was applied in two coats with a 90 second
flash between coats, flashed for 10 minutes at ambient conditions,
and then baked for 10 minutes at 345.degree. F. The final film
thicknesses were 1.8 to 2.0 mils. The total number of craters in
the untreated, cured panels was 33. The total number of craters on
the treated, cured panels was 22. Appearance of the two films was
equivalent.
Example 3
Resistance to Surface Contamination
[0173] A commercial, solvent-borne, thermoset clearcoat (FDCT 8000,
available from PPG Industries, Inc.) was treated, as described in
example 2, at 0.05% and 0.1% with the polymer of example 1.
[0174] Commercially available electrocoated 4".times.12" steel
panels were spot contaminated with 0.1 to 0.2 microgram quantities
of a series of polymers with varying surface tension. The two
treated and one untreated clear coats were spray applied onto
identically spot contaminated test panels. The clearcoat was
applied in two coats with a sixty second flash in between coats,
flashed for 10 minutes at ambient conditions and baked for 30
minutes at 285.degree. F. Dry film thicknesses were 1.6-1.8
mils.
[0175] The ability of each clear coat to cover each of the
contaminant polymers without leaving a visible defect has been
correlated to its crater resistance. Each contaminant spot was
rated against a set of arbitrarily defined standards. Typical
ratings for each clear coat, with 80 as a perfect score, are as
follows:
2 Rating FDCT 8000 untreated 51 FDCT 8000 + 0.05% additive 59 FDCT
8000 + 0.1% additive 61
[0176] Recoat adhesion and appearance were about equal for the
treated and untreated clear coats.
[0177] The present invention has been described with reference to
specific details of particular embodiments thereof. It is not
intended that such details be regarded as limitations upon the
scope of the invention except insofar as and to the extent that
they are included in the accompanying claims.
* * * * *