U.S. patent application number 13/439278 was filed with the patent office on 2012-08-02 for adhesion to plastic with block copolymers obtained using raft.
This patent application is currently assigned to DSM IP Assets B.V.. Invention is credited to John Geurts, Tijs Nabuurs, Gerardus Cornelis Overbeek, Michael Arnoldus Jacobus SCHELLEKENS.
Application Number | 20120196143 13/439278 |
Document ID | / |
Family ID | 39357780 |
Filed Date | 2012-08-02 |
United States Patent
Application |
20120196143 |
Kind Code |
A1 |
SCHELLEKENS; Michael Arnoldus
Jacobus ; et al. |
August 2, 2012 |
ADHESION TO PLASTIC WITH BLOCK COPOLYMERS OBTAINED USING RAFT
Abstract
An aqueous coating composition (which optionally can coat
plastic substrates) the composition comprising a block copolymer
and a polymer P; where the block copolymer comprises at least
blocks [A].sub.x[B].sub.y; where at least block [A] is obtained by
a controlled radical polymerisation of at least one ethylenically
unsaturated monomer via a reversible addition-fragmentation chain
transfer (RAFT) mechanism (optionally in solution in the presence
of a control agent and a source of free radicals); and wherein
block [A] comprises 20 to 100 mol % of ethylenically unsaturated
monomer units bearing water-dispersing functional groups; wherein
block [B] comprises 20 to 100 mol % of ethylenically unsaturated
monomer units bearing plastic adhesion promoting functional groups;
and wherein polymer P is prepared in the presence of blocks
[A].sub.x[B].sub.y. The compositions may be used to coat plastic
substrates, foam; surfaces having low surface energy, hydrophobic
substrates and/or polyolefins.
Inventors: |
SCHELLEKENS; Michael Arnoldus
Jacobus; (Waalwijk, NL) ; Overbeek; Gerardus
Cornelis; (Waalwijk, NL) ; Nabuurs; Tijs;
(Waalwijk, NL) ; Geurts; John; (Waalwijk,
NL) |
Assignee: |
DSM IP Assets B.V.
Heerlen
NL
|
Family ID: |
39357780 |
Appl. No.: |
13/439278 |
Filed: |
April 4, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12935991 |
Dec 20, 2010 |
|
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PCT/EP2009/053891 |
Apr 1, 2009 |
|
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13439278 |
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Current U.S.
Class: |
428/522 ;
427/2.1; 427/385.5; 427/393.5; 427/58; 524/460 |
Current CPC
Class: |
Y10T 428/31935 20150401;
C09D 153/00 20130101; C08F 2/24 20130101; C08F 287/00 20130101;
C08L 53/00 20130101; C09D 153/00 20130101; C08F 293/005 20130101;
C08L 53/005 20130101; C08L 2666/02 20130101; C08L 2666/02 20130101;
C08L 53/00 20130101; C08L 2666/02 20130101; Y10T 428/31938
20150401; C08L 53/005 20130101 |
Class at
Publication: |
428/522 ;
427/385.5; 427/393.5; 427/58; 427/2.1; 524/460 |
International
Class: |
C09D 153/00 20060101
C09D153/00; B05D 7/02 20060101 B05D007/02; B32B 27/30 20060101
B32B027/30; B05D 5/00 20060101 B05D005/00; C08F 2/22 20060101
C08F002/22; B05D 3/00 20060101 B05D003/00; B05D 7/24 20060101
B05D007/24 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 2008 |
EP |
08103288.0 |
Claims
1. A process for preparing an aqueous coating composition
comprising a block copolymer and a polymer P; wherein the block
copolymer comprises at least blocks [A].sub.x[B].sub.y, where at
least block [A] is obtained by a controlled radical polymerisation
of at least one ethylenically unsaturated monomer via a reversible
addition-fragmentation chain transfer (RAFT) mechanism; where block
[A] comprises: i) 0 to 50 mol % of ethylenically unsaturated
monomer units bearing crosslinking functional groups; ii) 20 to 100
mol % of ethylenically unsaturated monomer units bearing
water-dispersing functional groups; iii) 0 to 50 mol % of
ethylenically unsaturated monomers units selected from linear or
branched C.sub.1 to C.sub.8 alkyl(meth)acrylate monomers; iv) 0 to
5 mol % of ethylenically unsaturated monomer units bearing plastic
adhesion promoting functional groups; and v) 0 to 10 mol % of
ethylenically unsaturated monomers units different from those from
i), ii), iii)+iv); where i), ii), iii), iv)+v) add up to 100%;
block [A] has an average degree of polymerisation x, where x is an
integer from 3 to 80; where block [B] comprises: i) 0 to 5 mol % of
ethylenically unsaturated monomer units bearing crosslinking
functional groups; ii) 0 to 15 mol % of ethylenically unsaturated
monomer units bearing water-dispersing functional groups; iii) 0 to
50 mol % of ethylenically unsaturated monomers units selected from
linear or branched C.sub.1 to C.sub.8 alkyl(meth)acrylate monomers;
iv) 20 to 100 mol % of ethylenically unsaturated monomer units
bearing plastic adhesion promoting functional groups; and v) 0 to
10 mol % of ethylenically unsaturated monomers units different from
those from i), ii), iii)+iv); where i), ii), iii), iv)+v) add up to
100%; block [B] has an average degree of polymerisation y, where y
is an integer >10, where y>x; and where polymer P is obtained
in the presence of the block copolymer by an emulsion
polymerisation process, and comprises: i) 0 to 20 wt % of
ethylenically unsaturated monomer units bearing crosslinking
functional groups; ii) 0 to 15 wt % of ethylenically unsaturated
monomer units bearing water-dispersing functional groups; iii) 50
to 100 wt % of ethylenically unsaturated monomers units selected
from linear or branched C.sub.1 to C.sub.8 alkyl(meth)acrylate
monomers; iv) 0 to 50 wt % of ethylenically unsaturated monomer
units bearing plastic adhesion promoting functional groups; and v)
0 to 10 mol % of ethylenically unsaturated monomers units different
from those from i), ii), iii)+iv); where i), ii), iii), iv)+v) add
up to 100%.
2. A process according to claim 1, where block [A] is obtained
and/or obtainable by a controlled radical polymerisation of at
least one ethylenically unsaturated monomer via a reversible
addition-fragmentation chain transfer mechanism in solution in the
presence of a control agent and a source of free radicals.
3. A process according to claim 2, in which the aqueous coating
composition is capable of being applied to plastic substrates to
form a coating thereon.
4. A process according to claim 1, where block [B] is obtained
and/or obtainable by a controlled radical polymerisation of at
least one ethylenically unsaturated monomer via a reversible
addition-fragmentation chain transfer mechanism in solution in the
presence of a control agent and a source of free radicals.
5. A process according to claim 1, wherein the ethylenically
unsaturated monomer units bearing plastic adhesion promoting
functional groups are selected from the group consisting of C.sub.6
to C.sub.20 (preferably C.sub.6 to C.sub.15) optionally substituted
alkyl, cyclo alkyl and or aryl(meth)acrylate monomers, styrenic
monomers, C.sub.6 to C.sub.20 (preferably C.sub.6 to C.sub.15)
optionally substituted alkyl(meth)acrylamide monomers, vinylic
monomers and mixtures thereof.
6. A process according to claim 1, where, when the substrate is
polyolefinic, then component iv) of Block [B] comprises at least 50
mol % of isobornyl(meth)acrylate.
7. A process according to claim 1, wherein the control agent is
selected from the group consisting of dithioesters,
thioethers-thiones, trithiocarbonates, dithiocarbamates, xanthates
and mixtures thereof.
8. A process according to claim 1 where polymer P is at least
partially grafted to blocks [A][B].
9. An aqueous coating composition obtained and/or obtainable by a
process as claimed in claim 1.
10. An aqueous coating composition as claimed in claim 9, which is
capable of being applied to plastic substrates to form a coating
thereon.
11. A mixture of i) block copolymer comprising at least blocks
[A].sub.x[B].sub.y, and ii) polymer P; where said mixture is
obtained and/or obtainable by a process as claimed in claim 1.
12. A block copolymer-polymer comprising as components thereof i)
block copolymer comprising at least blocks [A].sub.x[B].sub.y and
ii) polymer P, where said blockcopolymer-polymer is obtained and/or
obtainable by a process as claimed in claim 1.
13. A coating obtained and/or obtainable from a coating composition
as claimed in claim 9 and/or block copolymer-polymer.
14. A substrate and/or article coated with a coating as claimed in
claim 13.
15. A coated substrate and/or coated article as claimed in claim
14, where the substrate and/or article comprises hydrophobic
plastic.
16. A method of coating a substrate and/or article comprising the
steps of i) applying a coating composition as claimed in claim 9
and/or block copolymer-polymer to the substrate and/or article; and
ii) drying the substrate and/or article to form a coating
thereon.
17. A method as claimed in claim 16, where the substrate and/or
article comprises hydrophobic plastic.
18. A coated substrate and/or coated article obtained and/or
obtainable by a method as claimed in claim 16.
19. Use of a coating composition as claimed in claim 9 and/or block
copolymer-polymer to coat a substrate and/or article.
20. Use of a coating composition as claimed in claim 9 and/or a
substrate and/or article to provide coatings on at least one
material selected from the group consisting of: plastic substrates
foams; surfaces having low surface energy; hydrophobic substrates;
polyolefins; any combinations thereof; and any mixtures
thereof.
21. A use as claimed in claim 20, where the coating is applied to
at least one article selected from the group consisting of:
vehicles; consumer electronic articles; furniture; household
articles, biomedical articles, any combinations thereof and any
mixtures thereof.
22. A method of manufacture of a coating composition as claimed in
claim 9 and/or a substrate and/or article for the purpose of being
used in at least one of the applications.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 12/935,991 filed on 20 Dec. 2010, which is the U.S. national
phase of International Application No. PCT/EP2009/053891, filed 1
Apr. 2009, which designated the U.S. and claims priority to
European Application No. 08103288.0, filed 1 Apr. 2008, the entire
contents of each of which are hereby incorporated by reference.
[0002] This invention relates to a process for obtaining an aqueous
coating composition comprising a block copolymer and polymer where
the composition is preferably suitable for application to a plastic
substrate more preferably a hydrophobic plastic substrate. It is
well recognised that adhesion to plastic substrates and in
particular hydrophobic plastic substrates is generally hard to
achieve. For adhesion to polyolefins, especially to polyolefins
such as polypropylene, a hydrophobic polymer would be desirable. A
problem with the sole use of such hydrophobic polymers is that they
tend to lack other properties, like good mechanical properties such
as flexibility and furthermore they may be difficult to pigment.
Pigment wetting often requires the presence of hydrophilic groups
which will be less favourable for wetting of hydrophobic
substrates.
[0003] Coatings for plastic substrates need to take into account
the low surface energy of plastic parts and the chemical similarity
between the coating materials and the plastic substrate. Coatings
for plastic substrates must adhere well to the plastic part for the
life of the component and the following criteria are often used to
measure the performance: adhesion, chemical resistance, impact
performance and scratch resistance.
[0004] The adhesion of the coating to the plastic substrate is
mainly determined by surface tension characteristics of the coating
and the substrate and interdiffusion of the coating into the
substrate.
[0005] Surface tension will directly influence a coating's ability
to wet out, to penetrate, and to adhere to the porous structure of
a surface. It is generally seen that the lower the surface tension,
the more problematic it is to get good adhesion of the coating on
the substrate.
[0006] The surface tension of the coating should be lower than the
surface tension of the substrate to enable wetting of the coating
on the surface of the substrate. Efficient wetting will maximize
the adhesion. Surface roughness may also be an important parameter
in certain cases as "mechanical interlocking" is another way to
improve adhesion.
[0007] Interdiffusion is the main adhesion mechanism for amorphous
plastics, especially in the case of solvent based coating systems.
The solvent is used to diffuse the polymer in the coating into the
plastic substrate to provide for molecular interlocking. Ideally,
this solvent should be selected from those that are good solvents
for the polymers of the coating composition, and for the polymer
constituting that of the plastic substrate.
[0008] From an environmental point of view there is however an
increasing need to reduce the amount of organic solvents in such
coating compositions. In this respect waterborne binders are
clearly preferred over conventional solventborne binders. The use
of waterborne binders in coating compositions for application to
hydrophobic plastic substrates may however give issues regarding
wetting and or polymer interdiffusion.
[0009] A common method to enhance the coating adhesion to
hydrophobic plastics with a relatively low surface tension like
polyolefins and fluorocarbons is to employ surface pretreating
processes. Surface treatments include chemical and physical methods
such as chemical etching and corona discharge, and typically result
in the formation of polar groups on the surface such as pendant
hydroxyl, chloro, amino and carboxyl groups. The introduction of
polar groups on the plastic substrate surface can provide improved
wetting (as the surface tension is increased) and potential
chemical interaction with the applied coating composition, which
can result in improved adhesion. Such surface pretreating methods
however are often costly and time-consuming, and tend to negatively
affect the plastic surface physical properties.
[0010] Clearly a need exists for water-based binders that provide
the desired combination of good adhesion to (hydrophobic) plastic
substrates and good mechanical properties and chemical or stain
resistances.
[0011] There is an increased scope of polymerisation methods
available for adaptation to polymerisations to make waterborne
polymers. In the design of such waterborne polymers for plastic
coating applications it would be very advantageous to be able to
control the polymer binder composition in terms of polymer chain
composition and chain architecture. For example, for obtaining good
adhesion to hydrophobic plastics it is desirable to use hydrophobic
polymers that are preferably of the same chemical composition as
the plastic polymer chains to maximise the degree of polymer chain
interdiffusion. For waterborne polymers however the degree of chain
interdiffusion is limited by the significant amount of hydrophilic
comonomers that typically need to be incorporated randomly in the
hydrophobic polymer backbone to make the polymer water-dispersable.
In addition, crosslinking of the binder composition can provide
improved coating performance in terms of for example chemical
resistances, but will often have a negative effect on adhesion. It
would therefore be desirable to separate out water-dispersing and
or crosslinking functionality from adhesive functionality within
the polymer binder.
[0012] In particular controlled radical polymerisation techniques
such as nitroxide mediated polymerisation (NMP), atom transfer
radical polymerisation (ATRP), and degenerative transfer techniques
such as reversible addition-fragmentation chain transfer (RAFT)
polymerisation have been investigated as means to control polymer
chain composition and architecture.
[0013] EP020125, EP381029, EP381030, EP468644, EP517379 and
EP560508 disclose monomers suitable for use in polymers to give
improved adhesion of the polymers to plastic substrates. However,
none of prior art examples discloses the advantageous use of an
adhesion promoting block copolymer that provides the desired
adhesion of the coating composition to plastic substrates.
[0014] US2004/0071871 (and US2004/0082494) discloses the use of an
amphiphilic block copolymer prepared using RAFT polymerization as
an additive for film forming compositions to promote adhesion on a
low energy surface such as a plastic or thermoplastic polymer
surface. The amphiphilic block copolymer provides improved wetting
of the film forming binder composition, but does not provide
(significant) improved adhesion of the binder composition to
(hydrophobic) plastic substrates.
[0015] US2002/0198347 describes a surface active block copolymer
comprising at least one hydrophilic block and at least one
hydrophobic block, prepared by living radical polymerisation. The
M.sub.n of the block copolymer is between 1,000 and 50,000 D, the
Tg of the hydrophobic block between -100 and +30.degree. C. and
having a specific surface tension. US2002/0198347 does not teach
the advantageous use of a block copolymer--binder composition for
obtaining the desired combination of good adhesion to hydrophobic
plastic substrates and good mechanical properties and good chemical
or stain resistances. Furthermore, the block copolymers as
disclosed in the prior art may provide adhesion to plastic
substrates through improved wetting of the coatings, however, the
overall level of adhesion is limited as the block copolymers do not
provide improved interdiffusion between the plastic substrate and
the coating composition.
[0016] WO 02/090392 discloses an acrylic acid (AA)/butyl acrylate
(BA) block copolymer. Although the copolymer contains the
hydrophobic monomer BA it is not present in an amount which could
be considered to aid adhesion to plastic.
[0017] EP560508 discloses a coating composition for polyolefins
including polypropylene comprising an aqueous emulsion of a polymer
system comprising a polymer which imparts polyolefin
adherability.
[0018] WO08/00622 relates to a method for coating substrates of
polyolefins by treatment with an aqueous dispersion containing a
copolymer, a copolymer of a C.sub.3-10 olefin and at least one
amphiphilic block copolymer.
[0019] We have now surprisingly found that according to the present
invention the reversible addition-fragmentation chain transfer
(RAFT) polymerisation process provides a useful route for preparing
a waterborne polymer composition that provides improved adhesion to
plastic substrates and in particular hydrophobic plastic substrates
in combination with good general coating properties, such as good
mechanical properties, pigment wetting and chemical resistances.
This advantageous combination of properties may be achieved with
block copolymers comprising one block having a specific
concentration of plastic adhesion promoting monomers and one block
having a hydrophilic character. Furthermore the reversible
addition-fragmentation chain transfer (RAFT) polymerisation process
may be used to provide a useful route for making water-based (or
water-dispersable) block copolymers that contain a plastic adhesion
promoting block next to at least a hydrophilic block.
[0020] When a suitable polymer is prepared in the presence of such
a block copolymer it means that waterborne coatings with an
advantageous combination of coating properties can be obtained that
is difficult to achieve otherwise.
[0021] RAFT polymerisation in for example a solution can avoid the
undesirable homopolymerisation of monomers with a high water
solubility and provides the possibility to fully control the
polymer chain composition and the chain architecture of water-based
polymers. By making an [A][B] type of block copolymer, followed by
preparing a polymer P, the above problems may be mediated, and
waterborne polymer compositions can be obtained that have the
desired combination of properties such as good film formation, good
mechanical properties, chemical coating properties and/or good
adhesion to plastic substrates (for example hydrophobic plastic
substrate).
[0022] An aspect of the present invention relates to aqueous
compositions that are capable of being applied to a plastic
substrate to form a coating thereon and a process for obtaining
such compositions (which are also referred to herein as aqueous
plastic coating compositions).
[0023] It is an object of the present invention to address some or
all of the problems described herein.
[0024] According to the invention there is provided a process for
preparing a aqueous coating composition comprising a block
copolymer and a polymer P; wherein the block copolymer comprises at
least blocks [A].sub.x[B].sub.y, where at least block [A] is
obtained by a controlled radical polymerisation of at least one
ethylenically unsaturated monomer via a reversible
addition-fragmentation chain transfer (RAFT) mechanism; where block
[A] comprises: [0025] i) 0 to 50 mol % of ethylenically unsaturated
monomer units bearing crosslinking functional groups; [0026] ii) 20
to 100 mol % of ethylenically unsaturated monomer units bearing
water-dispersing functional groups; [0027] iii) 0 to 50 mol % of
ethylenically unsaturated monomers units selected from linear or
branched C.sub.1 to C.sub.8 alkyl(meth)acrylate monomers; [0028]
iv) 0 to 5 mol % of ethylenically unsaturated monomer units bearing
plastic adhesion promoting functional groups; and [0029] v) 0 to 10
mol % of ethylenically unsaturated monomers units different from
those from i), ii), iii)+iv); [0030] where i), ii), iii), iv)+v)
add up to 100%; [0031] block [A] has an average degree of
polymerisation x, where x is an integer from 3 to 80; [0032] where
block [B] comprises: [0033] i) 0 to 5 mol % of ethylenically
unsaturated monomer units bearing crosslinking functional groups;
[0034] ii) 0 to 15 mol % of ethylenically unsaturated monomer units
bearing water-dispersing functional groups; [0035] iii) 0 to 50 mol
% of ethylenically unsaturated monomers units selected from linear
or branched C.sub.1 to C.sub.8 alkyl(meth)acrylate monomers; [0036]
iv) 20 to 100 mol % of ethylenically unsaturated monomer units
bearing plastic adhesion promoting functional groups; and [0037] v)
0 to 10 mol % of ethylenically unsaturated monomers units different
from those from i), ii), iii)+iv); [0038] where i), ii), iii),
iv)+v) add up to 100%; [0039] block [B] has an average degree of
polymerisation y, where y is an integer .gtoreq.10, where y>x;
and [0040] where polymer P is obtained in the presence of the block
copolymer by an emulsion polymerisation process, and comprises:
[0041] i) 0 to 20 wt % of ethylenically unsaturated monomer units
bearing crosslinking functional groups; [0042] ii) 0 to 15 wt % of
ethylenically unsaturated monomer units bearing water-dispersing
functional groups; [0043] iii) 50 to 100 wt % of ethylenically
unsaturated monomers units selected from linear or branched C.sub.1
to C.sub.8 alkyl(meth)acrylate monomers; [0044] iv) 0 to 50 wt % of
ethylenically unsaturated monomer units bearing plastic adhesion
promoting functional groups; and [0045] v) 0 to 10 mol % of
ethylenically unsaturated monomers units different from those from
i), ii), iii)+iv); [0046] where i), ii), iii), iv)+v) add up to
100%.
[0047] Preferably block [A] is obtained and/or obtainable by a
controlled radical polymerisation of at least one ethylenically
unsaturated monomer via a reversible addition-fragmentation chain
transfer mechanism in solution in the presence of a control agent
and a source of free radicals.
[0048] It is preferred that the compositions of the invention are
coating compositions capable of being applied to plastic substrates
to from a coating thereon.
[0049] The average degree of polymerisation x (or y) is determined
by the total molar amount of monomers in block [A] (or [B]) divided
by the total molar amount of control (RAFT) agent.
[0050] Preferably integer x is in the range of from 4 to 70 and
more preferably 5 to 60.
[0051] Preferably integer y is the range of from 10 to 500, more
preferably 20 to 300 and most preferably 25 to 200.
[0052] Preferably the block copolymer obtained by the process of
the invention comprises in the range of from 2 to 50 wt %, more
preferably 4 to 40 wt % and especially 5 to 35 wt % of block [A]
based on the weight of blocks [A] and [B].
[0053] Preferably the composition obtained by the process of the
invention comprises in the range of from 0.5 to 65 wt %, more
preferably 2 to 50 wt % and most preferably 3 to 40 wt % of blocks
[A][B] together, based on the weight of blocks [A][B] and polymer
P.
[0054] The term "comprising" as used herein means that the list
that immediately follows is non exhaustive and may or may not
include any other additional suitable items, for example one or
more further feature(s), component(s), ingredient(s) and/or
substituent(s) as appropriate. "Substantially comprising" as used
herein means a component or list of component(s) is present in a
given material in an amount greater than or equal to about 90%,
preferably .gtoreq.95%, more preferably .gtoreq.98% by weight of
the total amount of the given material. The term "consisting of" as
used herein mean that the list that follows is exhaustive and does
not include additional items.
[0055] For all upper and lower boundaries of any parameters given
herein, the boundary value is included in each range for each
parameter. All combinations of minimum and maximum values of the
parameters described herein may be used to define the parameter
ranges for various embodiments and preferences of the
invention.
[0056] It will be understood that the total sum of any quantities
expressed herein as percentages cannot (allowing for rounding
errors) exceed 100%. For example the sum of all components of which
the composition of the invention (or part(s) thereof) comprises
may, when expressed as a weight (or other) percentage of the
composition (or the same part(s) thereof), total 100% allowing for
rounding errors. However where a list of components is
non-exhaustive the sum of the percentage for each of such
components may be less than 100% to allow a certain percentage for
additional amount(s) of any additional component(s) that may not be
explicitly described herein.
[0057] Unless the context clearly indicates otherwise, as used
herein plural forms of the terms herein (for example monomer,
polymer, control agent, initiator and/or block) are to be construed
as including the singular form and vice versa.
[0058] As used herein chemical terms (other than IUPAC names for
specifically identified compounds) which comprise features which
are given in parentheses--such as (alkyl)acrylate, (meth)acrylate
and/or (co)polymer--denote that that part in parentheses is
optional as the context dictates, so for example the term
(meth)acrylate denotes both methacrylate and acrylate.
[0059] The substituents on the repeating unit of the polymer and/or
block copolymer may be selected to improve the compatibility of the
materials with the polymers and/or resins in which they may be
formulated and/or incorporated for the uses described herein. Thus
the size and length of the substituents may be selected to optimise
the physical entanglement or interlocation with the resin or they
may or may not comprise other reactive entities capable of
chemically reacting and/or crosslinking with such other resins as
appropriate.
[0060] A block copolymer is understood to be a copolymer comprising
at least two successive sections of blocks of monomer units of
different chemical constitutions. The block copolymers of the
invention can therefore be diblock, triblock or multiblock
copolymers. Block copolymers may be linear, branched, star or comb
like, and have structures such as [A][B], [A][B][A], [A][B][C],
[A][B][A][B], [A][B][C][B] etc. Preferably the block copolymer is a
linear diblock copolymer of structure [A][B], or a linear triblock
copolymer of structure [A][B][A]. Block copolymers may have
multiple blocks [A], [B] and optionally [C] in which case the block
copolymer is represented as for example [A].sub.x[B].sub.y or
[A].sub.x[B].sub.y[C].sub.z, where x, y and z are the degrees of
polymerisation (DP) of the corresponding blocks [A], [B] or
[C].
[0061] Furthermore any of the blocks in the block copolymer could
be either a homopolymer, meaning only one type of monomer, or a
copolymer, meaning more than one type of monomer. In case of a
copolymer type of block the composition could be either random or
gradient like, depending on the processing conditions used. A block
with a gradient composition is understood to be a block having a
continuously changing monomer composition along the block.
[0062] The block copolymer may be oligomeric comprising only a few
repeat units (such as up to 10) where typically any change in the
number of repeat units may significantly effect the overall
properties of the oligomer. Alternatively the block copolymer may
be a polymer with many more repeat units in which typically a small
change in the number of repeat units in the polymer has little or
no effect on the polymer's properties.
[0063] The term "controlled radical polymerisation" is to be
understood as a specific radical polymerisation process, also
denoted by the term of "living radical polymerisation", in which
use is made of control agents, such that the block copolymer chains
being formed are functionalised by end groups capable of being
reactivated in the form of free radicals by virtue of reversible
transfer or reversible termination reactions.
[0064] Controlled radical polymerisation processes in which
reversible deactivation of radicals proceeds by reversible transfer
reactions include for example the process for radical
polymerisation controlled by control agents, such as reversible
transfer agents of the dithioester (R--S--C(.dbd.S)--R') type as
described in WO98/01478 and WO99/35178, the process for radical
polymerisation controlled by reversible transfer agents of
trithiocarbonate (R--S--C(.dbd.S)--S--R') type as described in for
example WO98/58974, the process for radical polymerisation
controlled by reversible transfer agents of xanthate
(R--S--C(.dbd.S)--OR') type as described in WO98/58974, WO00/75207
and WO01/42312, and the process for radical polymerisation
controlled by reversible transfer agents of dithiocarbamate
(R--S--C(.dbd.S)--NR.sub.1R.sub.2) type as described for example in
WO99/31144 and WO99/35177.
[0065] Such controlled radical polymerisations are known in the art
as reversible addition-fragmentation chain transfer (RAFT)
polymerisation (WO98/01478; Macromolecules 1998 31, 5559-5562) or
macromolecular design via interchange of xanthates (MADIX)
polymerisation (WO98/58974; Macromolecular Symposia 2000 150,
23-32).
[0066] "Addition-fragmentation" is a two-step chain transfer
mechanism wherein a radical addition is followed by fragmentation
to generate a new radical species.
[0067] When preparing for example a block copolymer in the presence
of the control agent, the end of the growing block is provided with
a specific functionality that controls the growth of the block by
means of reversible free radical deactivation. The functionality at
the end of the block is of such a nature that it can reactivate the
growth of the block in a second and/or third stage of the
polymerisation process with other ethylenically unsaturated
monomers providing a covalent bond between for example a first and
second block [A] and [B] and with any further optional blocks.
[0068] Optionally the chain end functionality of block copolymer
[A].sub.x[B].sub.y is retained to assist with the covalent bond
formation between block copolymer [A].sub.x[B].sub.y and any
further optional blocks and or polymer P.
[0069] Preferably the block copolymer is obtained from a controlled
radical polymerisation process employing as a control agent, a
reversible transfer agent. Reversible transfer agents may be one or
more compounds selected from the group consisting of dithioesters,
thioethers-thiones, trithiocarbonates, dithiocarbamates, xanthates
and mixtures thereof.
[0070] Reversible transfer agents also include symmetrical transfer
agents. An example is a dibenzyltrithiocarbonate such as.
C.sub.6H.sub.5CH.sub.2--S--C(.dbd.S)--S--CH.sub.2C.sub.6H.sub.5.
[0071] Control agents of the xanthate type have low transfer
constants in the polymerization of styrenes and in particular
methacrylate type monomers which may result in a higher
polydispersity and/or poor chain growth control of the resultant
polymers and may be considered as less effective RAFT control
agents, although the actual mechanism involved is similar to the
reversible-addition fragmentation chain transfer (RAFT) mechanism
described in WO98/01478. Reversible transfer agents of the
dithioester type like for example benzyl dithiobenzoate derivatives
are generally considered as having a high transfer constant and
being more effective RAFT control agents.
[0072] Transfer constants are descibed in WO98/01478. "Chain
transfer constant" (C.sub.tr) means the ratio of the rate constant
for chain transfer (k.sub.tr) to the rate constant for propagation
(k.sub.p) at zero conversion of monomer and CTA. If chain transfer
occurs by addition-fragmentation, the rate constant for chain
transfer (k.sub.tr) is defined as follows:
k.sub.tr=k.sub.add.times.[k.sub..beta./(k.sub.-add+k.sub..beta.)]
where k.sub.add is the rate constant for addition to the CTA and
k.sub.-add and k.sub..beta. are the rate constants for
fragmentation in reverse and forward directions respectively.
[0073] In an embodiment of the invention the control agent
preferably has a transfer constant
C.sub.tr=(k.sub.add/k.sub.p)[k.sub..beta./(k.sub.-add+k.sub..beta.)]
of less than 50, more preferably less than 20 and most preferably
below 10.
[0074] Preferably the block copolymer is obtained from a controlled
radical polymerisation process employing a control agent having a
group with formula
--S--C(.dbd.S)--.
[0075] Preferably the block copolymer is obtained from a controlled
radical polymerisation process employing xanthates and/or
dibenzyltrithiocarbonate.
[0076] Preferably the block copolymer is obtained from a controlled
radical polymerisation process employing a xanthate such as
O-ethyl-S-(1-methoxycarbonyl)ethyl dithiocarbonate
[RSC(.dbd.S)--OC.sub.2H.sub.5 where
R.dbd.--CH(CH.sub.3)--C(.dbd.O)--OCH.sub.3].
[0077] For clarity, control agents for use in RAFT do not include
diphenylethylene, which although it is a control agent can not be
used as a RAFT control agent, i.e. for a RAFT polymerisation
mechanism.
Component I)
[0078] Conveniently component i) may comprise ethylenically
unsaturated monomer units (usually C.sub.1-12alkyl(meth)acrylates)
bearing crosslinking functional groups such as reactive double
bonds [for example allyl(meth)acrylate], epoxy [for example
glycidyl(meth)acrylate], hydroxy [for example
hydroxyalkyl(meth)acrylates such as hydroxyethyl(meth)acrylate,
2-hydroxypropyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate and
their modified analogues like Tone M-100 (available commerically
from Union Carbide Corporation under this trade name)], anhydride
(for example maleic anhydride), amine [for example
dimethylaminoethyl(meth)acrylate], acetoacetoxy [such as
acetoacetoxyethyl(meth)acrylate, for example for crosslinking with
amines], keto or aldehyde [such as (meth)acrolein or diacetone
acrylamide, for example for crosslinking with additive crosslinkers
including dihydrazides (such as adipic acid dihydrazide) or silane
functional groups], combinations thereof on the same monomer and/or
mixtures thereof. Preferred monomers suitable for crosslinking
include for example hydroxyalkyl(meth)acrylates,
glycidyl(meth)acrylates and diacetone acrylamide.
[0079] Monomers which may also provide some water-dispersing
properties, such as hydroxyalkyl(meth)acrylates like for example
hydroxyethyl(meth)acrylate (HE(M)A), are considered herein as
ethylenically unsaturated monomers providing crosslinking
functional groups.
[0080] Preferably block [A] comprises 0 to 35 mol %, more
preferably 0 to 25 mol % and most preferably 2 to 25 mol % of
component i).
[0081] Preferably block [B] comprises 0 to 3 mol %, more preferably
0 mol % of component i).
[0082] Preferably polymer P comprises 0 to 15 wt % of component
i).
Component II)
[0083] Conveniently component ii) may comprise ethylenically
unsaturated monomer units (preferably having at least 3 carbon
atoms e.g. from 3 to 20 carbon atoms) bearing non-ionic, ionic or
potentially ionic water-dispersing functional groups. Preferably
the water-dispersing functional groups bearing ionic or potentially
ionic functional groups need to be in their dissociated (i.e. salt)
form to effect their water-dispersing action. If they are not
dissociated they are considered as potential ionic groups which
become ionic upon dissociation. The ionic water-dispersing groups
are preferably fully or partially in the form of a salt in the
final composition of the invention. Ionic or potentially ionic
water-dispersing groups include cationic water-dispersing groups
such as basic amine groups, quaternary ammonium groups, and anionic
water-dispersing groups such as acid groups, for example phosphoric
acid groups, sulphonic acid groups, and carboxylic acid groups.
[0084] There are also potentially ionic functional monomers that
may become cationic upon addition of acid, such as dimethylamino
ethyl(meth)acrylate, dimethylamino propyl(meth)acrylate, and
dimethylamino propyl(meth)acrylamide. Such potentially ionic
functional monomers may contribute to improved adhesion and may
also improve stability or appearance on specific substrates such as
wood.
[0085] Preferably any ionic water-dispersing groups are anionic
water dispersing groups.
[0086] Preferred ethylenically unsaturated monomer units bearing
ionic or potentially ionic water-dispersing functional groups
include (meth)acrylic acid, itaconic acid, maleic acid,
.beta.-carboxyethyl acrylate, monoalkyl maleates (for example
monomethyl maleate and monoethyl maleate), citraconic acid,
styrenesulphonic acid, sodium styrenesulphonate,
vinylbenzylsulphonic acid, vinylsulphonic acid, sodium
vinylsulphonate, acryloyloxyalkyl sulphonic acids (for example
acryloyloxymethyl sulphonic acid), 2-acrylamido-2-alkylalkane
sulphonic acids (for example 2-acrylamido-2-methylethanesulphonic
acid), 2-methacrylamido-2-alkylalkane sulphonic acids (for example
2-methacrylamido-2-methylethanesulphonic acid),
mono(acryloyloxyalkyl)phosphates (for example,
mono(acryloyloxyethyl)phosphate and
mono(3-acryloyloxypropyl)phosphates) and
mono(methacryloyloxyalkyl)phosphates, and/or mixtures thereof.
[0087] Ethylenically unsaturated monomer units bearing
water-dispersing functional groups may also include ethylenically
unsaturated monomer units bearing non-ionic water dispersing groups
such as pendant polyoxyalkylene groups, more preferably
polyoxyethylene groups such as
methoxy(polyethyleneoxide(meth)acrylate), hydroxy polyethylene
glycol(meth)acrylates, alkoxy polyproplene glycol(meth)acrylates
and hydroxy polypropylene glycol(meth)acrylates, preferably having
a number average molecular weight of from 350 to 3,000 g/mol.
Examples of such ethylenically unsaturated monomers which are
commercially available include w-methoxypolyethylene
glycol(meth)acrylate. Other vinyl monomers providing non-ionic
water dispersible groups include (meth)acrylamidemono(methacryloyl
oxethyl)phosphate and acrylamide.
[0088] Preferably ethylenically unsaturated monomer units bearing
water-dispersing functional groups are selected from the group
consisting of ionic water-dispersing or potentially ionic
water-dispersing functional groups with a pKa<4.5, non-ionic
water-dispersing groups and mixtures thereof.
[0089] Monomers which may also provide some crosslinking properties
such as (meth)acrylic acid, are considered herein as monomers
providing water-dispersing functional groups.
[0090] Preferably 0 to 16 mol % of ethylenically unsaturated
monomer units bearing non-ionic water-dispersing groups is used,
more preferably 0 to 10 mol % and most preferred 0 to 7 mol % based
on the block copolymer.
[0091] Preferably block [A] comprises 0 to 35 mol %, more
preferably 0 to 25 mol % and most preferably 2 to 20 mol % of
ethylenically unsaturated monomer units bearing non-ionic water
dispersing groups.
[0092] Preferably block [B] comprises 0 to 16 mol %, more
preferably 0 to 12 mol % and most preferably 2 to 7 mol % of
ethylenically unsaturated monomer units bearing non-ionic water
dispersing groups.
[0093] Preferably block [A] comprises 50 to 100 mol %, more
preferably 75 to 100 mol % of component ii).
[0094] Preferably block [B] comprises 0 to 10 mol %, more
preferably 0 to 5 mol % and especially 1 to 10 mol % of component
ii).
[0095] Preferably polymer P comprises 0 to 10 wt % and more
preferably 0 to 5 wt % of component ii).
Component III)
[0096] Conveniently component iii) may comprise linear or branched
acyclic esters of acrylic acid and methacrylic acid of formula
1
CH.sub.2.dbd.CR.sup.5--COOR.sup.4 Formula 1
wherein R.sup.5 is H or methyl and R.sup.4 is optionally
substituted C.sub.1 to C.sub.8 alkyl, aryl or (alkyl)aryl which are
also known as acrylic or methacrylic monomers, examples of which
are methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate
(all isomers), butyl(meth)acrylate (all isomers) and
2-ethylhexyl(meth)acrylate.
[0097] Preferably block [A] comprises 0 to 35 mol %, more
preferably 0 to 25 mol % of component iii)
[0098] Preferably block [B] comprises 0 to 35 mol %, more
preferably 0 to 25 mol % of component iii).
[0099] Preferably polymer P comprises 60 to 100 wt % and more
preferably 70 to 100 wt % of component iii).
Component IV)
[0100] Conveniently component iv) may comprise monomers selected
from the group consisting of styrenic monomers such as styrene,
a-methylstyrene, t-butyl styrene, chloromethyl styrene, C.sub.6 to
C.sub.20 optionally substituted alkyl, cyclo alkyl and or
aryl(meth)acrylate monomers such as isobornyl(meth)acrylate,
isodecyl(meth)acrylate, lauryl(meth)acrylate,
tridecyl(meth)acrylate, tetradecyl(meth)acrylate,
hexadecyl(meth)acrylate, octadecyl(meth)acrylate
(=stearyl(meth)acrylate), dicyclopentenyloxymethyl(meth)acrylate,
benzyl(meth)acrylate, 2-phenoxyethyl(meth)acrylate,
3,3,5-trimethyl-cyclohexyl(meth)acrylate,
p-methylphenyl(meth)acrylate, 1-naphtyl(meth)acrylate,
3-phenyl-n-propyl(meth)acrylate and
2-phenyl-aminoethyl(meth)acrylate, C.sub.6 to C.sub.20 optionally
substituted alkyl(meth)acrylamide monomers such as
t-octyl(meth)acrylamide and n-decyl(meth)acrylamide, vinylic
monomers such as vinyl toluene, vinyl esters of versatic acid like
VEOVA.RTM. 9 or VEOVA.RTM. 10, vinyl chloride and vinylidene
chloride, and mixtures thereof.
[0101] Preferably the ethylenically unsaturated monomer units
bearing plastic adhesion promoting functional groups are selected
from the group consisting of C.sub.6 to C.sub.20 (preferably
C.sub.6 to C.sub.15) optionally substituted alkyl, cyclo alkyl and
or aryl(meth)acrylate monomers, styrenic monomers, C.sub.6 to
C.sub.20 (preferably C.sub.6 to C.sub.15) optionally substituted
alkyl(meth)acrylamide monomers, vinylic monomers and mixtures
thereof.
[0102] More preferably the ethylenically unsaturated monomer units
bearing plastic adhesion promoting functional groups are selected
from the group consisting of C.sub.6 to C.sub.20 (preferably
C.sub.6 to C.sub.15) optionally substituted alkyl, cyclo alkyl and
or aryl(meth)acrylate monomers and mixtures thereof.
[0103] Preferably block [A] comprises 0 to 2 mol %, more preferably
0 mol % of component iv).
[0104] Preferably block [B] comprises 50 to 100 mol %, more
preferably 75 to 100 mol % of component iv).
[0105] When the plastic substrate is polyolefinic, particularly
polypropylene or a copolymer of propylene and another olefin like
ethylene, then preferably component iv) of block [B] comprises at
least 50 mol %, and more preferably at least 70 mol % and
especially at least 90 mol % of isobornyl(meth)acrylate.
[0106] Preferably polymer P comprises 5 to 50 wt %, more preferably
4 to 40 wt % and especially 10 to 40 wt % of component iv). When
the plastic substrate is a polyolefin, particularly polypropylene
or a copolymer of propylene and another olefin like ethylene, then
preferably component iv) of polymer P comprises at least 50 wt %,
and more preferably at least 70 wt % and especially at least 90 wt
% of isobornyl (meth)acrylate.
Component V)
[0107] Conveniently component v) may comprise dienes such as
1,3-butadiene and isoprene; vinyl monomers such as acrylonitrile,
methacrylonitrile; vinyl halides such as vinyl chloride; vinylidene
halides such as vinylidene chloride; vinyl esters such as vinyl
acetate, vinyl propionate, vinyl laurate; heterocyclic vinyl
compounds; alkyl esters of mono-olefinically unsaturated
dicarboxylic acids such as di-n-butyl maleate and di-n-butyl
fumarate; amides of unsaturated carboxylic acids such as
(meth)acrylamide, N-methylol(meth)acrylamide and
N-alkyl(meth)acrylamides.
[0108] The Tg of a polymer herein stands for the glass transition
temperature and is well known to be the temperature at which a
polymer changes from a glassy, brittle state to a rubbery state. Tg
values of polymers may be determined experimentally using
techniques such as Differential Scanning calorimetry (DSC) or
calculated theoretically using the well-known Fox equation where
the Tg (in Kelvin) of a copolymer having "n" copolymerised
comonomers is given by the weight fractions "W" and the Tg values
of the respective homopolymers (in Kelvin) of each comonomer type
according to the equation "1/Tg=W.sub.1/Tg.sub.1+W.sub.2/Tg.sub.2+
. . . W.sub.n/Tg.sub.n". The calculated Tg in Kelvin may be readily
converted to .degree. C.
[0109] Preferably the calculated Tg of block [A] is in the range of
from 0.degree. C. to 150.degree. C.
[0110] Preferably the calculated Tg of block [A] is
.gtoreq.10.degree. C., most preferably .gtoreq.20.degree. C. and
especially .gtoreq.30.degree. C.
[0111] Preferably the calculated Tg of block [A] is
.ltoreq.130.degree. C. and most preferably .ltoreq.120.degree.
C.
[0112] Preferably the calculated Tg of polymer P is
.gtoreq.-10.degree. C., more preferably in the range of from -5 to
100.degree. C., most preferably -5 to 70.degree. C. and especially
-5 to 50.degree. C.
[0113] The weight average molecular weights (Mw) or number average
molecular weights (Mn) of the block copolymer may be determined by
using gel permeation chromatography (GPC) with THF as a solvent and
polystyrene standards.
[0114] Preferably block [A] has a number average molecular weight
in the range of from 300 to 10,000 g/mol and more preferably 500 to
5,000 g/mol.
[0115] Preferably block [B] has a number average molecular weight
in the range of from 1,000 to 75,000 g/mol and more preferably
2,000 to 50,000 g/mol.
[0116] Preferably block copolymer [A].sub.x[B].sub.y has a weight
average molecular weight.ltoreq.100,000 g/mol, more preferably
.ltoreq.75,000 g/mol and especially .ltoreq.50,000 g/mol.
[0117] Preferably the composition (block copolymer
[A].sub.x[B].sub.y and polymer P) has a weight average molecular
weight in the range of from 2,000 to 750,000 g/mol, more preferably
10,000 to 500,000 and especially 20,000 to 400,000 g/mol.
[0118] Preferably block [B] and polymer P are more hydrophobic than
block [A]. The hydrophobicity of a polymer may be determined by the
Hansch parameter. The Hansch parameter for a polymer is calculated
using a group contribution method. The monomer units forming a
polymer are assigned a hydrophobicity contribution and the
hydrophobicity of the polymer, the Hansch parameter, is calculated
based on the weight average of the monomers in the polymer as
disclosed in for example C. Hansch, P. Maloney, T. Fujita, and R.
Muir, Nature, 194. 178-180 (1962). Values of the hydrophobicity
contributions for several monomers are for example: styrene 4.29,
.alpha.-methylstyrene 4.7, methyl methacrylate 1.89, butyl acrylate
3.19, and acrylic acid -2.52. Therefore a polymer made up of STY
(20) .alpha.MS (20) MMA (20) BA (10) AA (30) has a Hansch value of
1.74.
[0119] Preferably the Hansch parameter for block [A] is lower than
that for block [B] and lower than that for polymer P.
[0120] Block [A] may have a Hansch parameter less than or equal to
1.7, preferably .ltoreq.1.5, more preferably .ltoreq.1.2, still
more preferably .ltoreq.1.0, most preferably .ltoreq.0.8,
especially .ltoreq.0.6 and for example .ltoreq.0.5.
[0121] Block [B] may have a Hansch parameter greater than or equal
to 1.0, preferably .gtoreq.1.5, more preferably .gtoreq.1.7, most
preferably .gtoreq.2.0 and especially .gtoreq.2.2.
[0122] Preferably polymer P has a Hansch parameter greater than or
equal to 1.7, more preferably .gtoreq.2.0 and most preferably
.gtoreq.2.5.
[0123] When in the form of an aqueous dispersion, the block
copolymer [A].sub.x[B].sub.y preferably has an acid value from 5 to
150 mgKOH/g and more preferably 20 to 100 mgKOH/g of block
copolymer [A].sub.x[B].sub.y,
[0124] When in the form of an aqueous dispersion the polymer P has
an acid value.ltoreq.50, more preferably .ltoreq.15 and especially
.ltoreq.10 mgKOH/g of polymer P.
[0125] The aqueous composition of the invention preferably has an
acid value.ltoreq.100, more preferably .ltoreq.70 and especially
.ltoreq.50 mgKOH/g of total polymer in the composition.
[0126] The RAFT polymerisation process for obtaining block [A]
and/or block [B] may be carried out in bulk, in solution, in
emulsion, in dispersion or in suspension. Preferably the RAFT
polymerisation process for obtaining block [A] may be performed in
solution. Preferably the RAFT polymerisation process for obtaining
block [B] may be performed in solution or by emulsion
polymerisation, more preferably in solution. Solution
polymerisation is a polymerisation process in which all the
reaction components including the monomer(s), initiator and control
agent are dissolved in a non-monomeric liquid solvent at the start
of the reaction. By non-monomeric is meant a solvent that does not
comprise monomers, in other words that won't react as part of the
polymerisation. Usually the solvent is also able to dissolve the
polymer or copolymer that is being formed. By a solvent is meant
water, organic solvents or mixtures thereof.
[0127] Preferably the block copolymer is prepared according a
solution dispersion polymerization process, which comprises the
preparation of the block copolymer in solution using a RAFT radical
polymerisation process and the dispersion of the obtained block
copolymer in water. Dispersion of the block copolymer in water can
be performed by adding water to the block copolymer solution or by
adding the block copolymer solution to water. Optionally suitable
surfactants can be used to aid in the dispersion process. The block
copolymer preferably comprises acid-functional groups that can be
transformed into anionic functional water-dispersing groups by
addition of a suitable organic or inorganic base such as for
example ammonia, triethylamine or sodium hydroxide. Preferred bases
are volatile amines, such as ammonia, or neutralising agents which
decompose without leaving inorganic residues which are sensitive to
water in the final dried coating. After the block copolymer is
dispersed in water the remaining solvent can optionally be removed
for example under reduced pressure.
[0128] Preferred organic solvents include alcohols (such as
ethanol, isopropanol, n-butanol, n-propanol, cyclohexanol), esters
(such as ethyl acetate, propyl acetate, isopropyl acetate, butyl
acetate), ketone solvents (such as acetone, methyl ethyl ketone,
methyl isobutyl ketone), and glycols (such as butyl glycol). More
preferred organic solvents include solvents selected from the group
consisting of acetone, ethanol, methyl ethyl ketone, iso-propanol,
ethyl acetate, butyl glycol and mixtures thereof. Preferably the
solvent is a mixture of water and a suitable organic solvent like
an alcohol. Preferably the solvent applied for the block copolymer
preparation using the solution dispersion polymerisation process
comprises an organic solvent with a low boiling point and or a high
evaporation rate to allow fast removal of the organic solvent after
the dispersion step under reduced pressure. Examples of such
solvents include acetone, ethanol, isopropanol, methyl ethyl ketone
and ethyl acetate.
[0129] A process for preparing a block having a gradient
composition comprises continually introducing a first monomer feed
to a reactor, where the first monomer feed continually varies in
its compositional feed content during the continuous introduction
by the addition of a different second monomer feed to the first
monomer feed and polymerising the monomers introduced into the
reactor.
[0130] The addition of the second monomer feed to the first monomer
feed may be in parallel to the introduction of the first monomer
feed to the polymerisation (i.e. both feeds start and end at the
same time). Alternatively the start of monomer feed one to the
reactor may precede the start of the addition of the second monomer
feed to the first monomer feed, or both monomer feeds may be
started simultaneously but the time taken for the addition of the
second monomer feed to the first monomer feed may exceed the time
taken for the introduction of the first monomer feed to the
reactor.
[0131] A block having a gradient composition may also be obtained
by the simultaneous introduction of a first and a second monomer
feed into the reactor where the rate of the introduction of the
first monomer feeds varies with respect to the rate of the
introduction of the second monomer feed.
[0132] The at least two monomer feeds used to prepare the block
having a gradient composition usually differ in composition. The
difference between the at least two monomer feeds may be for
example a difference in monomer composition, a difference in glass
transition temperature (Tg), or simply a variation in the
concentration of the respective monomers in each monomer feed.
[0133] Block [A] and [B] can be prepared in any order.
[0134] Polymer P is prepared using a radical emulsion
polymerisation process in the presence of the block copolymer
[A].sub.x[B].sub.y, where optionally the control agent functional
group located at one of the chain ends of the prepared block
copolymer [A].sub.x[B].sub.y can be deactivated or removed prior to
the preparation of polymer P. General methods for preparing aqueous
vinyl polymers are reviewed in the Journal of Coating Technology,
volume 66, number 839, pages 89 to 105 (1995). The control agent
may optionally be removed before or after dispersion of the block
copolymer and before or after the polymer preparation. When a RAFT
agent is used as control agent the RAFT group can be deactivated or
removed via for example oxidation reactions, radical induced
reactions, hydrolysis, or aminolysis. In the case that the control
agent functional group is not removed or only partially removed
prior to the preparation of polymer P at least part of the polymer
P chains will grow onto or become covalently attached to at least
part of the block copolymer chains.
[0135] Preferably the chain end functionality of the block
copolymer [A].sub.x[B].sub.y is retained to assist with the
covalent bond formation between the block copolymer and polymer P.
The chain end functionality of the block copolymer may be a RAFT
group (--S--C(.dbd.S)--) or a thiol (--SH) group or any other group
derived from the RAFT control agent that can provide covalent bond
formation between the block copolymer and polymer P.
[0136] Preferably at least 20 wt % of polymer P is covalently
bonded to the block copolymer.
[0137] In an embodiment of the invention there is provided an
aqueous composition comprising a block copolymer and a polymer
obtained according to the process of the invention. The aqueous
composition may contain free block copolymer [A].sub.x[B].sub.y and
free polymer P. Preferably, the block copolymer [A].sub.x[B].sub.y
and polymer P are partially grafted by means of covalent bond(s)
between the block copolymer [A].sub.x[B].sub.y and polymer P.
[0138] In another embodiment of the invention there is provided a
process for preparing a composition according to the invention
wherein said method comprises the following steps: [0139] 1.
synthesis in a solvent by means of a RAFT radical polymerisation
process of a first block [A] followed by the polymerisation of at
least a second block [B]. The order of preparation of [A] and [B]
can also be reversed; [0140] 2. optional removal of the control
agent before, during or after dispersing the block copolymer
[A].sub.x[B].sub.y in water; [0141] 3. optional removal of the
solvent from block copolymer [A].sub.x[B].sub.y; [0142] 4.
dispersion of the block copolymer [A].sub.x[B].sub.y in water
optionally containing monomers, by adding either water to the block
copolymer [A].sub.x[B].sub.y or adding the block copolymer
[A].sub.x[B].sub.y to water, optionally using surfactants,
preferably by addition of a base; [0143] 5. optional removal of
solvent from the block copolymer [A].sub.x[B].sub.y dispersion (if
solvent is still present from step 4.); [0144] 6. performing an
emulsion polymerisation process of monomers in the presence of the
block copolymer [A].sub.x[B].sub.y dispersion prepared in step 4
and or step 5 to obtain polymer P.
[0145] Alternatively after step 1 the solvent is removed by a
suitable method to get a solid, which solid can be afterwards
dispersed into water.
[0146] Furthermore the polymerisation process to make the block
copolymer or the polymer may be carried out as either a batch,
semi-batch or a continuous process. When the polymerisation process
for the block copolymer is carried out in the batch mode, the
reactor is typically charged with control agent and monomer. To the
mixture is then added the desired amount of initiator. The mixture
is then heated for the required reaction time. In a batch process,
the reaction may be run under pressure to avoid monomer reflux.
[0147] Semi-batch operation typically involves the continuous or
step-wise addition of monomer(s) (and/or other ingredients) during
polymerisation, and is often applied in copolymerisations to
minimize copolymer composition drift in case monomer reactivities
are very different. If the polymerisation process for the block
copolymer is to be carried out as a semi-batch process, the
reaction is typically carried out as follows: the reactor is
charged with a polymerisation medium, typically an organic solvent,
the control agent, and optionally (part of) the initiator. Into a
separate vessel are placed the monomer(s) and optionally
polymerisation medium and initiator. For safety reasons the
initiator can also be added via another separate vessel. The
polymerisation medium in the reactor is heated and stirred while
the monomer(s) and initiator are step-wise or gradually introduced.
The rate of monomer and/or initiator addition is determined largely
by the quantity of solution and/or the rate of polymerisation. When
the additions are completed, heating may be continued for an
additional period of time with or without additional initiator to
reduce unreacted monomer levels.
[0148] Furthermore after preparation of a first block, the prepared
block can be purified from residual monomers and subsequently used
for the polymerisation of a second monomer composition as a second
block or the second monomer composition can be polymerised directly
after the preparation of first block is completed. In this case at
least 80 wt %, preferably at least 90 wt %, most preferred at least
95 wt % of the first block monomer composition is reacted before
the second monomer composition is reacted. The second block can
contain up to 20 wt % (preferably 10 wt % or less) of the first
monomer composition.
[0149] A free-radical polymerisation of ethylenically unsaturated
monomers to make either the block copolymer and or the polymer will
require the use of a source of free radicals (i.e. an initiator) to
initiate the polymerisation. Suitable free-radical-yielding
initiators include inorganic peroxides such as K, Na or ammonium
persulphate, hydrogen peroxide, or percarbonates; organic
peroxides, such as acyl peroxides including for example benzoyl
peroxide, alkyl hydroperoxides such as t-butyl hydroperoxide and
cumene hydroperoxide; dialkyl peroxides such as di-t-butyl
peroxide; peroxy esters such as t-butyl perbenzoate; mixtures may
also be used. The peroxy compounds are in some cases advantageously
used in combination with suitable reducing agents (redox systems)
such as iso-ascorbic acid. Metal compounds such as Fe.EDTA
(ethylene diamine tetracetic acid) may also be usefully employed as
part of the redox initiator system. Azo functional initiators such
as 2,2'-azobis(isobutyronitrile) (AIBN),
2,2'-azobis(2-methyl-butyronitrile) (AMBN) and
4,4'-azobis(4-cyanovaleric acid) may also be used. The amount of
initiator or initiator system to use is conventional. For the
preparation of the block copolymer preferably the molar amount of
initiator does not exceed the molar amount of control agent that is
applied. A further amount of initiator may optionally be added at
the end of the polymerisation process to assist the removal of any
residual ethylenically unsaturated monomers.
[0150] A chain transfer agent may be added to control the molecular
weight of the polymer. Suitable chain transfer agents include
mercaptans such as n-dodecylmercaptan, n-octylmercaptan,
t-dodecylmercaptan, mercaptoethanol, iso-octyl thioglycolate,
C.sub.2 to C.sub.8 mercapto carboxylic acids and esters thereof
such as 3-mercaptopropionic acid and 2-mercaptopropionic acid; and
halogenated hydrocarbons such as carbon tetrabromide and
bromotrichloromethane. Preferably no chain transfer agent is added
during the preparation of the block copolymer.
[0151] Surfactants can be utilised in order to assist in the
dispersion of the block copolymer or polymer, and or in the
emulsification of the monomers in water (even if self-dispersible).
Suitable surfactants include but are not limited to conventional
anionic, cationic and/or nonionic surfactants and mixtures thereof
such as Na, K and NH.sub.4 salts of dialkylsulphosuccinates, Na, K
and NH.sub.4 salts of alkyl sulphonic acids, Na, K and NH.sub.4
alkyl sulphates, ethoxylated fatty acids and/or fatty amides, and
Na, K and NH.sub.4 salts of fatty acids such as Na stearate and Na
oleate. Other anionic surfactants include alkyl or (alk)aryl groups
linked to sulphonic acid groups, sulphuric acid half ester groups
(linked in turn to polyglycol ether groups), phosphonic acid groups
or carboxylic acid groups. Cationic surfactants include alkyl or
(alk)aryl groups linked to quaternary ammonium salt groups.
Nonionic surfactants include polyglycol ether compounds and
preferably polyethylene oxide compounds as disclosed in "Nonionic
surfactants--Physical chemistry" edited by M. J. Schick, M. Decker
1987.
[0152] If monomers bearing crosslinking functional groups are
present, then crosslinking may be introduced by combining the block
copolymer obtained by the process of the invention with a separate
crosslinker to provide either a self-crosslinking system (with a
long potlife, triggered by for instance a change in temperature or
pH or the evaporation of one of the ingredients in the overall
system, like a solvent or water), or a two pack system.
[0153] A separate crosslinking agent is preferably selected from
group consisting of polyhydrazides (including dihydrazides such as
adipic acid dihydrazide), polyisocyanates, carbodiimides,
polyaziridines, epoxies, melamine resins and mixtures thereof.
[0154] The composition obtained by the process of the invention can
be in the form of a solid, a solution or as an aqueous dispersion.
Most preferably the composition is used in an aqueous
composition.
[0155] Furthermore the composition obtained by the process of the
invention is particularly suitable for use in coating applications
in which it may provide a key part of coating compositions or
formulations. The composition may be used in compositions suitable
for applications such as adhesives, coatings, films, cosmetics,
inks. Such coating compositions can be pigmented or unpigmented.
Such coating compositions may be applied to a variety of plastic
substrates by any conventional method including brushing, dipping,
flow coating, spraying, flexo printing, gravure printing any other
graphic arts application methods and the like. The aqueous carrier
medium is removed by natural drying or accelerated drying (by
applying heat) to form a coating.
[0156] The coating composition can be applied to a broad variety of
plastic substrates, including for example polyolefins such as
polypropylene (PP) (treated and untreated) and polyethylene (PE),
polyamide, polycarbonate (PC), polyethyleneterepthalate (PET),
polymethyl methacrylate (PMMA), polystyrene (PS),
acrylonitrile/butadiene/styrene copolymer (ABS),
polytetrafluoroethylene (PTFE)) and polyvinyl chloride (PVC).
[0157] The polyolefins comprise in particular olefin polymers,
especially polymers of olefins containing 2 to 8, and preferably 2
to 5 and most preferably 3 carbon atoms. The polyolefins include,
without being limited thereto, polyethylene, polypropylene,
polybutenes, polypentenes, and copolymers of these with small
amounts of other monomers with which they are copolymerizable.
Included are such copolymers containing at least 85% by weight of
olefin units.
[0158] Of greatest importance is the group of polyolefins known as
"untreated polyolefins" and particularly "untreated polypropylene".
Untreated polyolefin surfaces are difficult to bond as well as to
wet. The difficulty is often ascribed to the non-polar and
hydrophobic nature of the purely hydrocarbon surface present on
these materials. Polypropylene has been singled out as being
especially difficult and it has been suggested that the reason for
the particular difficulty in bonding to untreated polypropylene is
that the surface consists essentially of methyl groups. Although
treatment of polyolefin substrates such as corona treatment of
polypropylene films or flame treatment of polypropylene articles is
commonly applied to improve wetting and coating adhesion, it is
often found that these treatments are insufficient or incomplete
and therefore do not give the desired adhesion performance.
Furthermore, treated polypropylene films for example show a
decrease in surface tension over time upon storage, and may
therefore require an additional treatment step shortly before
application of the coating to prevent serious issues in wetting and
coating adhesion. The coating composition of the invention however
provides good adhesion to both treated and untreated polypropylene,
and can therefore advantageously be applied to both untreated
polypropylene substrates and to treated or partly treated
polypropylene substrates. It may also be applied to treated or
untreated substrates made from blends of polypropylene with other
polymers such as poly(ethylene/propylene/diene), polyphenylene
sulphide, polyphenylene oxide etc. The substrate may be in the form
of a moulded or extruded article or film. Polypropylene films
include oriented polypropylene (OPP) and biaxially oriented
polypropylene (BOPP) films, which may be treated or untreated.
[0159] Polyolefins like PE and PP and fluorocarbons (like
polytetrafluoroethylene (PTFE)) are considered as very hydrophobic
plastic substrates. Adhesion to such very hydrophobic plastics
typically requires the use of blocks (preferably long blocks) of
hydrophobic monomers that can mix and/or entangle and/or
co-crystallise with the polymer chains from the plastic substrate
surface (often in combination with a co-solvent and/or elevated
drying temperature to mobilise the chains). Preferably the monomers
used in the block copolymer are compatible with the monomers
present in the plastic. For example if a polypropylene substrate is
used it is advantageous to use an isobornyl(meth)acrylate rich
block to improve adhesion to the substrate.
[0160] Preferably the plastic substrate is a hydrophobic plastic.
Examples of hydrophobic plastic substrates include (non-modified or
untreated) polypropylene (PP), polyethylene (PE),
polytetrafluoroethylene (PTFE) and polystyrene (PS). Most
preferably the substrate is untreated PP.
[0161] In a preferred embodiment the aqueous coating composition of
the invention is suitable for coating polyolefins, more preferably
propylene, most preferably untreated polypropylene.
[0162] Optionally in one embodiment of the invention the
composition obtained or obtainable by the process of the invention
may comprise one or more solventborne or waterborne adhesion
promoting resins such as chlorinated polyolefin (CPO) or
chlorine-free modified polyolefin resins. Such resins may
advantageously be used in amounts ranging from 1 to 40 wt %
preferably 3 to 25 wt % based on total binder solids for further
increasing the overall level of coating adhesion to very
hydrophobic plastics such as polypropylene. Preferred examples of
polyolefin adhesion promoters comprise waterborne chlorinated
polyolefins (such as those available commercially from Nippon Paper
Chemicals under the trade designations Superchlon E-723, E-673,
and/or E-503),and the environmentally more preferred waterborne
non-chlorinated (acrylic modified) polyolefins (such as that
available commerically from Eastman under the trade name Advantis
510W and/or those available commercially from Nippon Paper
Chemicals under the trade designations Auroren AE-201 and/or
AE-301).
[0163] For plastic adhesion a co-solvent may be needed to swell the
surface of the plastic to allow a certain degree of chain
interdiffusion.
[0164] Suitable organic co-solvents which may be added during the
process or after the process during formulation steps are well
known in the art and include xylene, toluene, methyl ethyl ketone,
acetone, ethanol, isopropanol, ethyl acetate, butyl acetate,
diethylene glycol, ethylene diglycol, butyl glycol, butyl diglycol,
dipropylene glycol methyl ether, propylene glycol n-butyl ether,
dipropylene glycol n-butyl ether, and 1-methyl-2-pyrrolidinone.
[0165] Preferably the aqueous composition comprises .ltoreq.50 wt
%, more preferably from .ltoreq.40 wt % and most preferably from
.ltoreq.35 wt % of organic co-solvent by weight of total
polymer.
[0166] Preferably only a low concentration of aromatic solvent is
added. Preferably less than 10 wt %, more preferably less than 5 wt
% and most preferred less than 2 wt % of aromatic solvent by weight
of total polymer is added.
[0167] The solids content of the aqueous composition is preferably
from 20 to 60 wt %, and most preferably from 30 to 50 wt %.
[0168] If desired the composition obtained by the process of the
invention can be used in combination with other polymer
compositions which are not according to the invention.
[0169] In another embodiment there is provided an aqueous emulsion
according to the invention additionally comprising a polymer Q,
wherein the solids content of the blockcopolymer--polymer P
together is .gtoreq.1 wt % and .ltoreq.35 wt % based on total
solids content of blockcopolymer--polymer P and polymer Q together.
Preferably polymer Q is an acrylic, urethane, urethane-acrylic,
alkyd, alkyd-acrylic or another type of polymer.
[0170] In a preferred embodiment there is provided a blend of an
aqueous polymer Q dispersion comprising an acrylic, urethane,
urethane-acrylic, alkyd, alkyd-acrylic or another type of polymer Q
with the aqueous emulsion of the invention. The advantage of such
blending is that the overall performance properties of the aqueous
polymer dispersion (coating) are retained, and additionally the
aqueous emulsion of the invention provides improved adhesion of the
coating to plastic substrates, and in particular hydrophobic
plastic substrates such as polypropylene.
[0171] Preferably the solids content of the aqueous emulsion
prepared by the process of the invention added to the aqueous
polymer Q dispersion amounts .ltoreq.35 wt % on total solids
content of the blend and more preferably .ltoreq.25 wt %.
Preferably the solids content of the aqueous emulsion prepared by
the process of the invention added to the aqueous polymer Q
dispersion amounts .gtoreq.1 wt % on total solids content of the
blend and more preferably .gtoreq.5 wt %.
[0172] Preferably the polymer Q dispersion that is added to the
aqueous emulsion prepared by the process of the invention is an
aqueous acrylic polymer dispersion.
[0173] Preferably the particle size of the polymer Q dispersion
that is blended with the aqueous emulsion prepared by the process
of the invention of the invention is in the range of from 50 to 400
nm, preferably .gtoreq.100 nm. Preferably the particle size of the
aqueous emulsion according to the invention is .ltoreq.100 nm.
[0174] In addition to the block copolymers and other ingredients
already described herein, a coating composition of the invention
may also contain further conventional ingredients such as: carrier
medium, pigments, dyes, emulsifiers, surfactants, plasticisers,
thickeners, heat stabilisers, levelling agents, anti-cratering
agents, fillers, sedimentation inhibitors, UV absorbers,
antioxidants, dispersants, reactive diluents, waxes, neutralising
agents, adhesion promoters, defoamers, co-solvents, wetting agents,
fire retardants and the like, any combinations thereof and/or any
mixtures thereof. The ingredients may be introduced at any stage of
the production process or subsequently.
[0175] The coating composition of the invention may be applied to a
variety of plastic substrates by any conventional method including
brushing, dipping, flow coating, spraying, and the like. A carrier
medium if present may removed by natural drying or accelerated
drying (e.g. by applying heat) to form a coating.
[0176] An aspect of the invention provides a coating composition
and/or polymer obtained and/or obtainable by a process of the
invention
[0177] An aspect of the invention provides a coating composition
obtained and/or obtainable by a process of the invention
[0178] Another aspect of the invention provides a mixture of i)
block copolymer comprising at least blocks [A].sub.x[B].sub.y, and
ii) polymer P; where said mixture is obtained and/or obtainable by
a process of the invention
[0179] Yet another aspect of the invention provides a
blockcopolymer-polymer comprising as components thereof i) block
copolymer comprising at least blocks [A].sub.x[B].sub.y and ii)
polymer P; said blockcopolymer-polymer obtained and/or obtainable
by a process of the invention.
[0180] A further aspect of the invention provides a coating
obtained and/or obtainable from a coating composition, mixture
and/or block copolymer-polymer of the invention.
[0181] Another aspect of the invention provides a substrate and/or
article coated with a coating of the invention.
[0182] A still other aspect of the invention provides a method of
coating a substrate and/or article comprising the steps of i)
applying a coating composition, mixture and/or block
copolymer-polymer of the invention to the substrate and/or article;
ii) drying the substrate and/or article to form a coating
thereon.
[0183] A further aspect of the invention provides use of a coating
composition, mixture, block copolymer-polymer, substrate and/or
article of the invention to coat a substrate and/or article.
[0184] A yet other aspect of the invention provides for a coated
substrate and/or article obtained and/or obtainable by the method
of coating of the invention.
[0185] A further aspect of the invention provides use of a coating
composition, mixture, block copolymer-polymer, substrate and/or
article of the invention in at least one of the applications
descibed herein.
[0186] A still yet other aspect of the invention provides a method
of manufacture of a coating composition, mixture, block
copolymer-polymer, substrate and/or article of the invention for
the purpose being used in at least one of the applications descibed
herein.
[0187] The terms `effective`, `acceptable` `active` and/or
`suitable` (for example with reference to any process, use, method,
application, preparation, product, material, formulation, compound,
monomer, block copolymer, polymer precursor, and/or polymers of the
present invention and/or described herein as appropriate) will be
understood to refer to those features of the invention which if
used in the correct manner provide the required properties to that
which they are added and/or incorporated to be of utility as
described herein. Such utility may be direct for example where a
material has the required properties for the aforementioned uses
and/or indirect for example where a material has use as a synthetic
intermediate and/or diagnostic tool in preparing other materials of
direct utility. As used herein these terms also denote that a
functional group is compatible with producing effective,
acceptable, active and/or suitable end products.
[0188] Preferably the utility, end use and/or applications for the
polymers, compostions, substrates and/or articles of the present
invention may be selected from at least one of the following
non-limiting list, any combinations and/or mixtures thereof (some
of which may overlap): [0189] coatings for plastic substrates
and/or foams; [0190] coatings for surfaces having low surface
energy; [0191] coatings for hydrophobic substrates such as for
example polyolefins; [0192] coatings for polyolefins, such as
polypropylene (PP), for example PP articles and oriented PP (OPP)
and/or biaxial OPP (BOPP) films, either treated or preferably
untreated; [0193] coatings for vehicles such as interior and/or
exterior automotive coatings; [0194] coatings for consumer
electronic articles, preferably the plastic parts thereof; [0195]
coatings for furniture and/or household articles, preferably the
plastic parts thereof; [0196] coatings for biomedical articles,
preferably the plastic parts thereof such as catheters.
[0197] Many other variations embodiments of the invention will be
apparent to those skilled in the art and such variations are
contemplated within the broad scope of the present invention.
[0198] Further aspects of the invention and preferred features
thereof are given in the claims herein.
EXAMPLES
[0199] The present invention is now illustrated by reference to the
following non-limiting examples. Unless otherwise specified, all
parts, percentages and ratios are on a weight basis. Molecular
weights were determined by GPC using polystyrene standards and THF
as eluent.
[0200] The prefixes Comp or C before an example denotes that it is
comparative. The term "working" means that the example is according
to the invention. The term "non-working" means that it is not
according to the invention (i.e. comparative).
[0201] Various registered trademarks, other designations and/or
abbreviations are used herein to denote some of ingredients used to
prepare polymers and compositions of the invention. These are
identified below by chemical name and/or trade-name and optionally
their manufacturer or supplier from whom they are available
commercially. However where a chemical name and/or supplier of a
material described herein is not given it may easily be found for
example in reference literature well known to those skilled in the
art: such as: `McCutcheon's Emulsifiers and Detergents`, Rock Road,
Glen Rock, N.J. 07452-1700, USA, 1997 and/or Hawley's Condensed
Chemical Dictionary (14th Edition) by Lewis, Richard J., Sr.; John
Wiley & Sons. In the examples, the following abbreviations and
terms are specified: [0202] DP=average degree of polymerization
[0203] AA=acrylic acid [0204] BA=butyl acrylate [0205] MMA=methyl
methacrylate [0206] BMA=butyl methacrylate [0207] iBOA=isobornyl
acrylate [0208] xanthate1=O-ethyl-S-(1-methoxycarbonyl)ethyl
dithiocarbonate (Rhodixan A1, provided by Rhodia Chimie) [0209]
MEK=methyl ethyl ketone [0210] SLS=sodium lauryl sulfate [0211]
APS=ammonium persulfate
[0212] Molecular weights were determined by GPC relative to
polystyrene standards.
[0213] An overview of the Examples and the Comparative Examples is
given in Table 1.
TABLE-US-00001 TABLE 1 Block copolymer (BC) [DP]/ BC/RC wt %
Experiment Random copolymer (RC) [DP] Polymer P (Tg .degree. C.) on
total solids Example 1 BC1 = AA-iBOA [20-50] BMA/BA (0.degree. C.)
26% Example 2 BC1 = AA-iBOA [20-50] BMA/BA (0.degree. C.) 16%
Example 3 BC1 = AA-iBOA [20-50] BMA/BA (10.degree. C.) 26% Example
4 BC2 = AA-iBOA [50-100] BMA/BA (0.degree. C.) 33% Comparative RC1
= AA/iBOA [20/50]; BMA/BA (0.degree. C.) 16% Example 1a 12 wt % AA
Comparative RC2 = AA/iBOA [33/46]; BMA/BA (0.degree. C.) 16%
Example 1b 20 wt % AA Comparative RC3 = AA/iBOA [49/40]; BMA/BA
(0.degree. C.) 16% Example 1c 30 wt % AA Comparative BC3 = AA-BA
[20-50] BMA/BA (10.degree. C.) 16% Example 2 Comparative None
MMA/BA/iBOA/AA -- Example 3 (21.degree. C.) Comparative None
BMA/BA/iBOA/AA -- Example 4 (12.degree. C.) Comparative None
BMA/BA/iBOA/AA -- Example 5 (25.degree. C.)
Block Copolymer 1
[0214] Synthesis of a [A].sub.x-[B].sub.y Block Copolymer where
Block [A] is Based on AA and x=20 and Block [B] is Based on iBOA
with y=50
[0215] Block [A]:
[0216] 170 gram of ethanol and 28 gram (0.14 mol) of xanthate 1
were added to a 1 L three-necked glass flask equipped with
condenser cooler, temperature measuring probe and mechanical
stirring device. The reaction mixture was degassed by purging with
nitrogen at room temperature for 15 minutes while stirring. The
temperature was raised to 75.degree. C. and 10wt % of a monomer
feed mixture of 197 gram (2.74 mol) of AA and 228 gram of ethanol
was added to the reaction mixture. Then a mixture of 2.3 gram
(approximately 6 mmol) of 4,4'-azobis(4-cyanovaleric acid)
(Aldrich, 75+%) and 25 gram of ethanol was added. After 15 minutes
at 70.degree. C. the gradual addition was started of the remaining
90wt % of the AA/ethanol mixture. The addition lasted 4 hours under
a weak nitrogen stream and at a controlled temperature of
70.degree. C., after which the mixture was kept for 7 hours at
70.degree. C. The reaction mixture was then cooled to 20.degree. C.
and a sample was withdrawn for further analysis. The conversion of
AA as determined with gas chromatography was found to be 96% and
the solids level was experimentally determined at 37.5%. GPC
analysis of the final product resulted in the following values:
Mn=1905 g/mol, PDI (=Mw/Mn)=1.30.
[0217] Block [B]:
[0218] 237 gram of the block [A] reaction mixture, corresponding to
approximately 54 mmol of precursor block [A] based on a solids
level of 37.5% and a theoretical molecular weight of 1650 g/mol,
and 60 gram of MEK were added to a 2 L three-necked glass flask
equipped with condenser cooler, temperature measuring probe and
mechanical stirring device. The reaction mixture was degassed by
purging with nitrogen at room temperature for 15 minutes while
stirring. The temperature was raised to 70.degree. C. and 10 wt %
of a monomer feed mixture of 562 gram (2.70 mol) of iBOA and 425
gram of MEK was added to the reaction mixture. Then a mixture of
3.0 gram (approximately 8 mmol) of 4,4'-azobis(4-cyanovaleric acid)
(Aldrich, 75+%) and 20 gram of MEK was added to the reaction
mixture. After 15 minutes at 70.degree. C. the gradual addition was
started of the remaining 90 wt % of the iBOA/MEK mixture. The
addition lasted 4 hours under a weak nitrogen stream and at a
controlled temperature of 70.degree. C., after which the mixture
was kept for about 10 hours at 70.degree. C. The reaction mixture
was then cooled to 20.degree. C. and a sample was withdrawn for
further analysis. The conversion of iBOA as determined with gas
chromatography was found to be 97%. Theoretical solids level was
50%. GPC analysis of the final [A]-[B] block copolymer product
resulted in the following values: Mn=4870 g/mol, PDI
(=Mw/Mn)=2.25.
Block Copolymer 2
[0219] Synthesis of a [A].sub.x-[B].sub.y Block Copolymer where
Block [A] is Based on AA and x=50 and Block [B] is Based on iBOA
with y=100
[0220] Block [A]:
[0221] 189 gram of ethanol and 10.6 gram (51 mmol) of xanthate 1
were added to a 1 L three-necked glass flask equipped with
condenser cooler, temperature measuring probe and mechanical
stirring device. The reaction mixture was degassed by purging with
nitrogen at room temperature for 15 minutes while stirring. The
temperature was raised to 75.degree. C. and 5 wt % of a monomer
feed mixture of 184 gram (2.55 mol) of AA and 241 gram of ethanol
was added to the reaction mixture. Then a mixture of 0.8 gram
(approximately 2.2 mmol) of 4,4'-azobis(4-cyanovaleric acid)
(Aldrich, 75+%) and 25 gram of ethanol was added. After 15 minutes
at 70.degree. C. the gradual addition was started of the remaining
95 wt % of the AA/ethanol mixture. The addition lasted 4 hours
under a weak nitrogen stream and at a controlled temperature of
70.degree. C., after which the mixture was kept for 7 hours at
70.degree. C. The reaction mixture was then cooled to 20.degree. C.
and a sample was withdrawn for further analysis. The conversion of
AA as determined with gas chromatography was found to be 94% and
the solids level was experimentally determined at 33.1%. GPC
analysis of the final product resulted in the following values:
Mn=3040 g/mol, PDI (=Mw/Mn)=1.47.
[0222] Block [B]:
[0223] 298 gram of the block [A] reaction mixture, corresponding to
approximately 26 mmol of precursor block [A] based on a solids
level of 33.1% and a theoretical molecular weight of 3810 g/mol,
was added to a 2 L three-necked glass flask equipped with condenser
cooler, temperature measuring probe and mechanical stirring device.
The reaction mixture was degassed by purging with nitrogen at room
temperature for 15 minutes while stirring. The temperature was
raised to 70.degree. C. and 10 wt % of a monomer feed mixture of
540 gram (2.60 mol) of iBOA and 500 gram of MEK was added to the
reaction mixture. Then a mixture of 1.8 gram (approximately 5 mmol)
of 4,4'-azobis(4-cyanovaleric acid) (Aldrich, 75+%) and 20 gram of
MEK was added to the reaction mixture. After 15 minutes at
70.degree. C. the gradual addition was started of the remaining 90
wt % of the iBOA/MEK mixture. The addition lasted 4 hours under a
weak nitrogen stream and at a controlled temperature of 70.degree.
C., after which the mixture was kept for about 10 hours at
70.degree. C. The reaction mixture was then cooled to 20.degree.
C., and 140 gram MEK was added to reduce the viscosity of the
mixture. The conversion of iBOA as determined with gas
chromatography was found to be 95%. Theoretical solids level was
45%. GPC analysis of the final [A]-[B] block copolymer product
resulted in the following values: Mn=5890 g/mol, PDI
(=Mw/Mn)=2.66.
Block Copolymer 3
[0224] Synthesis of a [A].sub.x-[B].sub.y Block Copolymer where
Block [A] is Based on AA and x=20 and Block [B] is Based on BA with
y=50
[0225] The block [A] reaction mixture for block copolymer 3 was
prepared according a similar recipe and procedure as described for
block copolymer 1 (data for block [A] from GPC analysis: Mn=2190
g/mol, PDI (=Mw/Mn)=1.25). For the preparation of block [B] of
block copolymer 3, 164.7 gram of the block [A] reaction mixture,
corresponding to approximately 40 mmol of precursor block [A] based
on a solids level of 40.1% and a theoretical molecular weight of
1650 g/mol, and 14 gram of MEK were added to a 1 L three-necked
glass flask equipped with stirrer, condenser cooler and temperature
measuring probe. The reaction mixture was degassed by purging with
nitrogen at room temperature for 15 minutes while stirring. The
temperature was raised to 75.degree. C. and 10 wt % of a monomer
feed mixture of 256.8 gram (2.0 mol) of BA and 202.4 gram of MEK
was added to the reaction mixture. Then a mixture of 2.24 gram
(approximately 6 mmol) of 4,4'-azobis(4-cyanovaleric acid)
(Aldrich, 75+%) and 10 gram of MEK was added. After 15 minutes at
70.degree. C. the gradual addition was started of the remaining 90
wt % of the BA/MEK mixture. The addition lasted 4 hours under a
weak nitrogen stream and at a controlled temperature of 70.degree.
C., after which the mixture was kept for 6 hours at 70.degree. C.
The reaction mixture was then cooled to 20.degree. C. and a sample
was withdrawn for further analysis. The conversion of BA as
determined with gas chromatography was found to be 96% and the
solids level was experimentally determined at 49.8%. GPC analysis
of the final [A]-[B] block copolymer product resulted in the
following values: Mn=6610 g/mol, PDI (=Mw/Mn)=1.59.
Random Copolymers of AA and iBOA (RC1; RC2; RC3) Synthesis of
Random Copolymer RC1 of AA and iBOA with the Same Overall
Composition as Block Copolymer 1 (wt % AA=12%; DP AA=20 and DP
iBOA=50)
[0226] 130 gram of MEK and 6.0 gram (29 mmol) of xanthate 1 were
added to a 1 L three-necked glass flask equipped with condenser
cooler, temperature measuring probe and mechanical stirring device.
The reaction mixture was degassed by purging with nitrogen at room
temperature for 15 minutes while stirring. The temperature was
raised to 75.degree. C. and 10 wt % of a monomer feed mixture of
41.8 gram (0.58 mol) of AA, 302.0 gram (1.45 mol) of iBOA, and 200
gram MEK was added to the reaction mixture. Then a mixture of 2.20
gram (approximately 6 mmol) of 4,4'-azobis(4-cyanovaleric acid)
(Aldrich, 75+%) and 23 gram of ethanol was added. After 15 minutes
at 70.degree. C. the gradual addition was started of the remaining
90wt % of the AA/iBOA/MEK mixture. The addition lasted 5 hours
under a weak nitrogen stream and at a controlled temperature of
70.degree. C., after which the mixture was kept for 5 hours at
70.degree. C. The reaction mixture was then cooled to 20.degree. C.
and a sample was withdrawn for further analysis.
[0227] The synthesis of random copolymer RC2 (20 wt % AA; DP AA=33
and DP iBOA=46) and random copolymer RC3 (30 wt % AA; DP AA=49 and
DP iBOA=40) was performed according the same recipe and procedure
as described above, where the ratio of AA and iBOA in the monomer
feed mixture was adjusted to obtain the desired degree of
polymerization.
[0228] The theoretical solids level of RC1, RC2 and RC3 was 50%.
GPC analysis of the final random copolymers resulted in the
following values: RC1 Mn=5655 g/mol and PDI=2.03; RC2 Mn=6515 g/mol
and PDI=2.01; RC3 Mn=6120 g/mol and PDI=2.14.
Preparation of an Aqueous Dispersion of Block Copolymer 1
[0229] 53.3 gram of triethylamine was added to 660 gram of block
copolymer 1 at 20.degree. C. whilst stirring. To the obtained
mixture an amount of 1320 gram demineralized water was slowly added
under stirring, resulting in the formation of a stable aqueous
dispersion. After removal of residual MEK from the dispersion under
reduced pressure the pH was measured at 8.1 and the final solids
level was experimentally determined at 24.3%. The particle size of
the dispersion as determined with light scattering was 40 nm.
Preparation of an Aqueous Dispersion of Block Copolymer 2
[0230] 38.7 gram of triethylamine was added to 460 gram of block
copolymer 2 at 20.degree. C. whilst stirring. To the obtained
mixture an amount of 828 gram demineralized water was slowly added
under stirring, resulting in the formation of a stable aqueous
dispersion. After removal of residual MEK from the dispersion under
reduced pressure the pH was measured at 7.8 and the final solids
level was experimentally determined at 22.6%. The particle size of
the dispersion as determined with light scattering was 117 nm.
Preparation of an Aqueous Dispersion of Block Copolymer 3
[0231] 35.8 gram of triethylamine was added to 401 gram of block
copolymer 3 at 20.degree. C. whilst stirring. To the obtained
mixture an amount of 800 gram demineralized water was slowly added
under stirring, resulting in the formation of a stable aqueous
dispersion. After removal of residual MEK from the dispersion under
reduced pressure the pH was measured at 7.0 and the final solids
level was experimentally determined at 22.9%. The particle size of
the dispersion as determined with light scattering was 32 nm.
Preparation of an Aqueous Dispersion of Random Copolymers RC1, RC2
and RC3
[0232] The preparation of an aqueous dispersion of random copolymer
RC1 was performed according a similar recipe and procedure as
applied for block copolymer 1. For RC2 and RC3 the amount of
triethylamine was adjusted to equal molar ratio to the number of
carboxylic acid groups. After removal of residual MEK from the
dispersion under reduced pressure the pH for RC1, RC2 and RC3 was
measured at 8.5, 8.3 and 7.7, respectively. The final solids level
for RC1, RC2 and RC3 was experimentally determined at 22.4%, 21.9%
and 25.7%, respectively. The dispersions of RC1 and RC2 were of
relatively poor quality; analysis with light scattering resulted in
a very broad particle size distribution (polydispersity>0.95),
with an average particle size of about 200 and 600 nm,
respectively. The dispersion of RC3 was a stable clear aqueous
solution (no measurable particle size).
Example 1
Synthesis of a BMA/BA Emulsion Polymer in the Presence of Block
Copolymer 1
[0233] 75 gram of demineralized water and 185.6 gram of the aqueous
dispersion of block copolymer 1 prepared above (24.3% in water)
were added to a 1 L three-necked glass flask equipped with stirrer,
condenser cooler and temperature measuring probe. The reaction
mixture was heated while stirring to 65.degree. C. under nitrogen
atmosphere. Then a mixture of 35.3 gram BMA and 9.8 gram BA was
added. After 20 minutes mixing at 65.degree. C. an initiator
mixture of 0.2 gram APS and 20 gram demineralized water, set at
pH=8 with triethylamine, was added. The reaction mixture was then
heated to 85.degree. C. After 10 minutes at 85.degree. C. the
gradual addition was started of an initiator feed mixture of 0.2
gram APS and 18 gram demineralized water (set at pH=8 with
triethylamine), and a pre-emulsified monomer feed mixture of 55
gram demineralized water, 0.2 gram SLS (30wt % in water), 65.6 gram
BMA and 18.2 gram BA. Both mixtures were added as parallel feeds to
the reaction mixture over a time period of 2.5 hours. During the
reaction the pH of the reaction mixture was kept above 7.0. At the
end of the monomer and initiator feed the reaction mixture was kept
for 30 minutes at 85.degree. C. A post reaction with tert-butyl
hydroperoxide and isoascorbic acid was performed to react any
residual monomer. The resultant emulsion was then cooled to room
temperature and the pH was adjusted with triethylamine to 8.0.
[0234] Examples 2 and 3 were prepared using a similar recipe and
procedure as applied for Example 1, but now either the amount of
block copolymer was varied (Example 2) or the Tg of the emulsion
polymer was varied by changing the BMA/BA wt ratio (Example 3).
[0235] Example 4 was prepared using a similar recipe and procedure
as applied for Example 1, but now the dispersion of block copolymer
2 was applied at a level of 33 wt % on total solids.
Comparative Examples 1a, 1b and 1c
Synthesis of a BMA/BA Emulsion Polymer in the Presence of Random
Copolymer RC1, RC2, or RC3
[0236] The preparation of the comparative examples 1a, 1b and 1c
based on RC1, RC2 and RC3, respectively, was performed using the
same recipe and procedure as applied for Example 2, but now the
aqueous dispersions of either random copolymer RC1, RC2 or RC3 was
applied, each at a level of 16 wt % on total solids.
[0237] It was found that Comparative Examples 1a and 1b could not
be prepared as the synthesis of the emulsion polymers based on RC1
and RC2 resulted in excessive amounts of fouling and sediment
formation. These results demonstrate that the random copolymers RC1
(12 wt % AA) and RC2 (20 wt % AA) exhibit very poor stabilization
properties, especially when compared to the respective block
copolymers. The synthesis of the emulsion polymer based on RC3 (30
wt % AA), Comparative Example 1c, gave relatively low fouling and
sediment formation and resulted in a stable latex that was found to
be acceptable for further testing.
Comparative Example 2
Synthesis of a BMA/BA Emulsion Polymer in the Presence of Block
Copolymer 3
[0238] Comparative Example 2 was prepared using a similar recipe
and procedure as applied for Example 3, but now the dispersion of
block copolymer 3 was applied at a level of 16 wt % on total
solids.
Comparative Example 3
Synthesis of a MMA/BA/iBOA/AA Emulsion Polymer
[0239] 310 gram of demineralized water and 10.9 gram of SLS (30wt %
in water) were added to a 2 L three-necked glass flask equipped
with stirrer, condenser cooler and temperature measuring probe. The
reaction mixture was heated while stirring to 75.degree. C. under
nitrogen atmosphere. Then 10 wt % was added of a pre-emulsified
monomer mixture consisting of in total 165 gram demineralized
water, 5.5 gram SLS (30 wt % in water), 176.6 gram MMA, 151.8 gram
BA, 56.4 gram iBOA, and 7.7 gram AA. The reaction mixture was
further heated to 75.degree. C. and then a mixture of 0.3 gram APS
and 5.3 gram demineralized water was added. The reaction mixture
was then heated to 85.degree. C. and kept at this temperature for
15 minutes. An initiator feed mixture of 0.69 gram APS and 68.3
gram demineralized water and the remaining 90 wt % of the
pre-emulsified monomer feed were then gradually added as parallel
feeds to the reaction mixture over a time period of 3 hours. The
reaction mixture was then kept for 30 minutes at 85.degree. C. A
post reaction with tert-butyl hydroperoxide and isoascorbic acid
was performed to react any residual monomer. The resultant emulsion
was then cooled to room temperature. The pH of the latex was
adjusted to 8.0 by addition of ammonia.
Comparative Example 4
Synthesis of a BMA/BA/iBOA/AA Emulsion Polymer
[0240] 606 gram of demineralized water and 17.1 gram of SLS (30 wt
% in water) were added to a 2 L three-necked glass flask equipped
with stirrer, condenser cooler and temperature measuring probe. The
reaction mixture was heated while stirring to 80.degree. C. under
nitrogen atmosphere. Then 10 wt % was added of a pre-emulsified
monomer mixture consisting of in total 179 gram demineralized
water, 8.6 gram SLS (30 wt % in water), 336.1 gram BMA, 93.0 gram
BA, 76.3 gram iBOA, and 7.9 gram AA. The reaction mixture was
further heated to 78.degree. C. and then a mixture of 0.5 gram APS
and 4.2 gram demineralized water was added. The reaction mixture
was then heated to 85.degree. C. and kept at this temperature for
10 minutes. An initiator feed mixture of 1.1 gram APS and 107 gram
demineralized water and the remaining 90 wt % of the pre-emulsified
monomer feed were then gradually added as parallel feeds to the
reaction mixture over a time period of 2 hours. The reaction
mixture was then kept for 30 minutes at 85.degree. C. A post
reaction with tert-butyl hydroperoxide and isoascorbic acid was
performed to react any residual monomer. The resultant emulsion was
then cooled to room temperature. The pH of the latex was adjusted
to 8.0 by addition of ammonia.
[0241] Comparative Example 5 was prepared using a similar recipe
and procedure as applied for Comparative Example 4, but now the
monomer feed mixture consisted of in total 132 gram demineralized
water, 8.6 gram SLS (30 wt % in water), 270.2 gram BMA, 74.8 gram
BA, 152.6 gram iBOA, and 15.7 gram AA.
[0242] The properties of the final prepared acrylic dispersions are
given in Table 2. All latices, except those of Comparative Examples
1a and 1b, were processed with little or no fouling and/or sediment
formation. Final free monomer levels were all well below 500
ppm.
TABLE-US-00002 TABLE 2 Viscosity Particle (Brook- size Mn Mw Exper-
Solids.sup.1) pH field) (DLS) (GPC) (GPC) iment [%] [--] [mPa s]
[nm] [kg/mol] [kg/mol] Example 1 31.8 8.0 60 66 15.5 154 Example 2
35.1 8.2 98 68 23.5 173 Example 3 33.0 7.8 50 67 17.9 200 Example 4
28.8 7.5 45 118 20.5 246 Comp 34.0 7.9 23 428 18.6 118 Ex 1c Comp
29.8 7.9 155 71 33.4 174 Ex 2 Comp 39.6 8.0 21 99 17.2 250 Ex 3
Comp 34.6 7.4 10 92 36.6 410 Ex 4 Comp 34.9 7.8 10 471 30.1 226 Ex
5 .sup.1)gravimetrically determined
Examination of Dry and Wet Adhesion Level to ABS, PVC, Polystyrene
(PS), Polycarbonate (PC) and Untreated Polypropylene (Untreated
PP)
[0243] The level of dry and wet adhesion to various plastic
substrates was determined using a Gitterschnitt test (see test
descriptions). Prior to testing all Examples and Comparative
Examples were adjusted to a solids level of about 30% with
demineralized water and formulated with 10 wt % butyl glycol and 1
wt % Byk 346, based on total acrylic dispersion. The formulations
were allowed to stand overnight prior to use.
[0244] Plastic test panels of ABS (Vikureen ABS white, Vink), PVC
(PVC XT light grey, Vink), PS (Vikureen PS XT white, Vink), PC
(Lexan 9030 Exell D transparent, GE Plastics) and PP (Simona PP XT
naturel, Vink) of about 12 cm.times.20 cm.times.0.2 cm were cleaned
with ethanol and coated with the formulated acrylic dispersions at
a 50 .mu.m layer thickness using a wirerod. The coated panels were
left to dry for at least 1 hour at approximately 20.degree. C., and
then dried in an oven at 50.degree. C. for a period of 16 hours to
make sure that all water and residual solvent was removed from the
film. After this drying period the coated plastic plates were left
for at least one hour at 20.degree. C. The obtained dry films were
then examined for dry and wet adhesion (Gitterschnitt, Gt).
Results Adhesion to Untreated Polypropylene Plates
[0245] For all Examples and Comparative Examples the level of dry
and wet adhesion to untreated polypropylene plates was determined.
Results are given in Table 3.
TABLE-US-00003 TABLE 3 Dry adhesion to untreated PP plate Wet
adhesion to (Gt; 0 = excellent untreated PP plate Experiment and 5
= poor) (Gt; 0 = excellent and 5 = poor) Example 1 2 2 Example 2
0-1 0-1 Example 3 2-3 2 Example 4 2 2 Comp Ex 1c 5 5 Comp Ex 2 5 5
Comp Ex 3 5 5 Comp Ex 4 5 5 Comp Ex 5 5 5
[0246] The results given in Table 3 show that the Examples have
much better adhesion to untreated polypropylene than the
Comparative Examples.
Results Adhesion to Oriented Polypropylene Foil
[0247] For Example 1 and Comparative Example 3 the level of dry
adhesion to oriented polypropylene substrate (OPP foil) was
determined using a tape test. Prior to testing the acrylic
dispersions of Example 1 and Comparative Example 3 were formulated
with 10 wt % on total dispersion of butyl glycol (added as 80 wt %
in water). Only in case of adhesion testing to the very hydrophobic
untreated polypropylene substrate an additional amount of 0.25 wt %
on total dispersion of Surfynol PSA-336 (available from Air
Products) was added together with the butyl glycol. The pH of the
butyl glycol/water premix was adjusted to about 8 by ammonia before
addition. The formulations were tinted with Microlith blue to allow
visual assessment of the adhesion test results.
[0248] Films of the tinted formulated dispersions were applied by a
wire rod at 6 microns wet onto the treated and untreated side of an
oriented polypropylene substrate foil (50MB-210 available from
Exxon Mobil). The casted films were dried for 1 minute in an oven
at 80.degree. C. The obtained dry films were left for at least 2
hours at 20.degree. C. and then examined for adhesion properties by
performing a tape test. Prior to application the surface tension of
the treated and untreated side of the oriented polypropylene
substrate surface was measured as defined in DIN ISO 8296 in
accordance with ASTM D 2578-04a by using test inks available from
Softal Electronic (Germany).
[0249] The test results obtained for Example 1 and Comparative
Example 3 are given in Table 4.
TABLE-US-00004 TABLE 4 Wetting Tape test Experiment (0-5; 5 = good)
(% coating removed) Locus of failure treated oriented polypropylene
foil (surface tension 34-36 Dynes/cm) Example 1 4 0% no failure
Comp Ex 3 3-4 100% adhesive untreated oriented polypropylene foil
(surface tension <<34 Dynes/cm) Example 1 5 <10% cohesive
Comp Ex 3 5 100% adhesive
[0250] The results given in Table 4 show that Example 1 provides
very good adhesion to both the treated and untreated side of the
OPP foil, whereas Comparative Example 3 gives no adhesion at
all.
Dry and Wet Adhesion to ABS, Polystyrene (PS), Polyvinyl Chloride
(PVC) and Polycarbonate (PC)
[0251] For Examples 1 to 5 and Comparative Example 1c the level of
dry and wet adhesion to ABS, PS, PVC and PC was determined using
the Gitterschnitt test, where 0=excellent adhesion and 5=very poor
adhesion. Results are given in Table 5.
TABLE-US-00005 TABLE 5 ABS PS PVC PC Experiment dry/wet (Gt)
dry/wet (Gt) dry/wet (Gt) dry/wet (Gt) Example 1 0/1 0-1/1 0-1/0-1
0-1/1 Example 2 0/0-1 0/0 0/0 0/0-1 Example 3 0/1 0/0 0/0 1/1-2
Example 4 1/1 0/1 0/1 0-1/1 Comp Ex 1c 0/2 0/1 0-1/5 1/4
[0252] The results given in Table 5 show that the Examples have
better overall wet adhesion than Comparative Example 1c.
Test Descriptions
Dry and Wet Adhesion to Plastic Substrate Plates
[0253] The level of dry adhesion to untreated plastic substrates
(ABS, PVC, polystyrene, polycarbonate, and untreated polypropylene)
was determined using a cross-cut test ("Gitterschnitt" (Gt) test in
accordance with ASTM D 3002/D 3359 and DIN EN ISO 2409). A
cross-cut was made onto the dried coated plastic plates using a
cross-cut knife (Byk-5120). A self adhesive tape (Sellotape.TM. 25
mm from Henkel Consumer Adhesives) was applied under uniform
pressure onto the coated substrate, covering the cross-cut, where
after the tape was torn off in a single movement. This tape test
was then repeated with the tape placed over the cross-cut in a
perpendicular direction to the first test. The degree of dry
adhesion of the coating onto the plastic substrate was then
classified with a scale from 0 to 5 (according ISO Class 0-5 (Gt))
by determining the amount of coating that is detached or flaked
partly or wholly along the edges of the cuts, where 0 means that
the cross-cut area is not affected (excellent adhesion); 1 means
that the affected cross-cut area is not significantly greater than
5%; 2 means that the affected cross-cut area is significantly
greater than 5%, but not significantly greater than 15%; 3 means
that the affected cross-cut area is significantly greater than 15%,
but not significantly greater than 35%; 4 means that the affected
cross-cut area is significantly greater than 35%, but not
significantly greater than 65%; 5 means any degree of flaking that
cannot even be classified by classification 4 (very poor
adhesion).
[0254] To determine the level of wet adhesion a piece of cotton
wool soaked with demineralized water was placed on an area of the
coated substrate. After 4 hours at 20 (.+-.3.degree. C.) the wet
cotton wool was removed and the coating was carefully dried with a
tissue. The level of wet adhesion was then determined according the
cross-cut test method used for determining the dry adhesion, where
the cross-cut was made onto the coated area that was exposed to the
water.
Adhesion to Oriented Polypropylene Foil
[0255] A self adhesive tape (Sellotape.TM. 25 mm from Henkel
Consumer Adhesives) was applied under uniform pressure onto a dry
coating layer applied onto both the treated and untreated side of
the oriented polypropylene substrate, where after the tape is torn
off with a non-continuous movement. The adhesion properties of the
coating onto the polypropylene substrate were investigated by
assessing the amount of coating that is adhered to the tape after
removing the tape from the coating. Optimal adhesion is obtained at
"0% coating removed". In addition the main locus of failure was
visually determined as being cohesive, i.e. failure within the
coating, or adhesive, i.e. between the coating-substrate interface.
Cohesive failure typically indicates a strong interaction between
the coating and the substrate, whereas adhesive failure means a
weak interaction between the coating and the substrate.
Wetting
[0256] The wetting behavior of the coating onto both the treated
and untreated side of the oriented polypropylene substrate surface
was visually assessed and classified from a scale of 0 to 5, where
0 means very poor wetting and 5 means excellent wetting.
* * * * *