U.S. patent application number 10/118143 was filed with the patent office on 2003-03-06 for carboxylic acid functional polyurethane polymers and blends thereof used in magnetic recording media.
This patent application is currently assigned to Minnesota Mining and Manufacturing company. Invention is credited to Carlson, James G., Kumar, Ramesh C..
Application Number | 20030045630 10/118143 |
Document ID | / |
Family ID | 24305195 |
Filed Date | 2003-03-06 |
United States Patent
Application |
20030045630 |
Kind Code |
A1 |
Carlson, James G. ; et
al. |
March 6, 2003 |
Carboxylic acid functional polyurethane polymers and blends thereof
used in magnetic recording media
Abstract
The invention provides novel macromonomer and carboxyl
functional polyurethanes having a high carboxyl content. The
invention further provides dispersions, coatings and magnetic
recording media comprising these polyurethanes, or blends or
copolymers of these polyurethanes with quaternary ammonium
compounds. The invention further provides novel dispersions,
coatings and magnetic recording media comprising combinations of
carboxyl functional polyurethanes having a high carboxyl content
with quaternary ammonium polymers.
Inventors: |
Carlson, James G.; (Lake
Elmo, MN) ; Kumar, Ramesh C.; (Maplewood,
MN) |
Correspondence
Address: |
Office of Intellectual Property Counsel
3M Innovative Properties Company
PO Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
Minnesota Mining and Manufacturing
company
|
Family ID: |
24305195 |
Appl. No.: |
10/118143 |
Filed: |
April 8, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10118143 |
Apr 8, 2002 |
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09636535 |
Aug 10, 2000 |
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09636535 |
Aug 10, 2000 |
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09131520 |
Aug 10, 1998 |
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6139966 |
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09131520 |
Aug 10, 1998 |
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08924046 |
Aug 28, 1997 |
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5874502 |
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08924046 |
Aug 28, 1997 |
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08576616 |
Dec 21, 1995 |
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5759666 |
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Current U.S.
Class: |
524/589 ; 528/44;
G9B/5.246; G9B/5.25; G9B/5.285 |
Current CPC
Class: |
C08G 18/62 20130101;
G11B 5/7027 20130101; C08G 18/348 20130101; C08G 18/6659 20130101;
C08G 18/2875 20130101; C08G 18/6283 20130101; G11B 5/7022 20130101;
C08G 18/0823 20130101; C08G 18/6541 20130101; C08G 18/0833
20130101; C08G 18/6212 20130101; C08G 18/0814 20130101; C08G
18/6229 20130101; C08G 18/4277 20130101; Y10T 428/31855 20150401;
Y10T 428/31928 20150401; C08G 18/6245 20130101; Y10T 428/24207
20150115; G11B 5/735 20130101; C08G 18/44 20130101; Y10T 428/31551
20150401; C08G 18/284 20130101; Y10T 428/31609 20150401 |
Class at
Publication: |
524/589 ;
528/44 |
International
Class: |
C08K 003/00; C08L
075/00 |
Claims
1. A carboxylic acid functional graft carboxyl polyurethane polymer
comprising the reaction product of a mixture comprising: (a) one or
more polyisocyanates; (b) a macromonomer(s) having a number average
molecular weight greater than about 500 and one to two
isocyanate-reactive groups selected from the group consisting of
hydroxyl, primary amino, secondary amino and mercapto groups; and
wherein if two isocyanate-reactive groups are present, they are
separated by no more than about 10 atoms within the macromonomer
molecule; (c) a carboxylic acid functional polyol; (d) optionally
one or more quaternary ammonium polyols; (e) optionally one or more
polyols, wherein the polyols(s) of element (e) are defined to
exclude components of elements (b), (c), and (d); wherein the
number of isocyanate-reactive groups present in the mixture prior
to reaction exceeds the number of isocyanate groups; and wherein
the macromonomer (b) content comprises from about 5% to about 95%
by weight based on the weight of the graft carboxyl poiyurethane
polymer; and wherein at least about 0.2 meq of carboxylic acid
groups are present on the graft carboxyl polyurethane polymer per
gram of graft carboxyl polyurethane polymer.
2. The graft carboxyl polyurethane polymer of claim 1 wherein the
macromonomer (b) content comprises from about 20% to about 80% by
weight based on the weight of the graft carboxyl polyurethane
polymer.
3. The graft carboxyl polyurethane polymer of claim 1 wherein at
least about 0.4 meq of carboxylic acid group are present on the
graft carboxyl polyurethane polymer per gram of polymer.
4. The graft carboxyl polyurethane polymer of claim 1 wherein the
carboxylic acid functional polyol is
2,2-bis(hydroxymethyl)propionic acid.
5. A dispersion comprising: (a) one or more of the graft carboxyl
polyurethane polymers of claim 1; (b) optionally a quaternary
ammonium compound(s); (c) one or more pigments selected from the
group consisting of magnetic pigments, non-magnetic pigments, and
mixtures thereof; (d) an organic solvent; and (e) optionally a
polyisocyanate curative.
6. The dispersion of claim 5 wherein about 0.3 to about 30
millimoles of quaternary ammonium group are present in the
dispersion per kilogram of pigment.
7. The dispersion of claim 5 wherein a quaternary ammonium compound
is present and the quaternary ammonium compound is a quaternary
ammonium polyurethane.
8. The dispersion of claim 5 wherein a quaternary ammonium compound
is present and the quaternary ammonium compound is a quaternary
ammonium functional nonhalogenated vinyl copolymer.
9. A coating comprising the dispersion of claim 5 dried of
solvent.
10. A coating comprising the coating of claim 6 dried of
solvent.
11. A coating comprising the coating of claim 7 dried of
solvent.
12. The coating of claim 9 wherein about 20 to about 60 percent by
weight of the polyisocyanate curative 5(e) is present based upon
the total weight of the coating exclusive of pigment, and said
polyisocyanate curative is the reaction product of a mixture
comprising: (i) one or more diisocyanates; and (ii) one or more
polyols; wherein at least one of the polyols of (ii) is an
oligomeric polyol of number average molecular weight between about
500 and 5000 having a glass transition temperature less than about
0.degree. C. and wherein said oligomeric polyol comprises between
about 10 and about 80% by weight of the curative and wherein the
overall ratio of hydroxyl to isocyanate functionality in the
mixture comprising (I) and (ii) prior to reaction is less than
1.
13. A magnetic recording medium comprising the coating of claim 9
on at least one side of a substrate.
14. A magnetic recording medium comprising the coating of claim 10
on at least one side of a substrate.
15. A magnetic recording medium comprising the coating of claim 11
on at least one side of a substrate.
16. A magnetic recording medium comprising the coating of claim 12
on at least one side of a substrate.
17. A magnetic recording medium comprising the coating of claim 9
on one side of a substrate wherein one or more non-magnetic
pigments are present.
18. A dispersion comprising: (a) one or more of carboxyl
polyurethane polymers comprising the reaction product of a mixture
comprising: (i) one or more polyisocyanates; (ii) a carboxylic acid
functional polyol(s); (iii) optionally one or more polyols, wherein
the polyols(s) of element (iii) are defined to exclude components
of element(s) (a)(ii); wherein the number of isocyanate-reactive
groups present in the mixture prior to reaction exceeds the number
of isocyanate groups and wherein at least about 0.2 meq of
carboxylic acid group are present on the carboxyl polyurethane
polymer per gram of carboxyl polyurethane polymer; (b) a polymeric
quaternary ammonium compound(s) having a number average molecular
weight of at least about 500; (c) one or more pigments selected
from the group consisting of magnetic pigments, non-magnetic
pigments, and mixtures thereof; and (d) an organic solvent; and (e)
optionally a polyisocyanate curative
19. The dispersion of claim 18 wherein about 0.3 to about 30
millimoles of quaternary ammonium group are present in the
dispersion per kilogram of pigment.
20. The dispersion of claim 18 wherein the quaternary ammonium
compound is a quaternary ammonium polyurethane.
21. The dispersion of claim 18 wherein the quaternary ammonium
compound is a quaternary ammonium functional non-halogenated vinyl
copolymer.
22. The dispersion of claim 18 wherein at least about 1.0 meq of
carboxylic acid group are present on the carboxyl polyurethane
polymer per gram of carboxyl polyurethane polymer.
23. A coating comprising the dispersion of claim 18 dried of
solvent
24. A coating comprising the dispersion of claim 19 dried of
solvent
25. A coating comprising the dispersion of claim 20 dried of
solvent
26. A coating comprising the dispersion of claim 21 dried of
solvent.
27. A coating comprising the dispersion of claim 22 dried of
solvent
28. The coating of claim 23 wherein about 20 to about 60 percent by
weight of the polyisocyanate curative 18(e) is present based upon
the total weight of the coating exclusive of pigment, and said
polyisocyanate curative is the reaction product of a mixture
comprising: (i) one or more diisocyanates; and (ii) one or more
polyols; wherein at least one of the polyols of (ii) is an
oligomeric polyol of number average molecular weight between about
500 and 5000 having a glass transition temperature less than about
0.degree. C. and wherein said oligomeric polyol comprises between
about 10 and about 80% by weight of the curative and wherein the
overall ratio of hydroxyl to isocyanate functionality in the
mixture comprising (1) and (ii) prior to reaction is less than
1.
29. A magnetic recording medium comprising the coating of claim 23
on at least one side of a substrate.
30. A magnetic recording medium comprising the coating of claim 24
on at least one side of a substrate
31. A magnetic recording medium comprising the coating of claim 25
on at least one side of a substrate.
32. A magnetic recording medium comprising the coating of claim 26
on at least one side of a substrate.
33. A magnetic recording medium comprising the coating of claim 27
on at least one side of a substrate
34. A magnetic recording medium comprising the coating of claim 28
on at least one side of a substrate.
35. A magnetic recording medium comprising the coating of claim 29
on at least one side of a substrate wherein one or more
non-magnetic pigments are present.
36. A coating comprising the dispersion of claim 8 dried of
solvent.
37. A magnetic recording medium comprising the coating of claim 36
on at least one side of a substrate.
Description
FIELD OF THE INVENTION
[0001] This invention relates to novel polyurethane polymers with a
graft architecture having a backbone with carboxylic acid
functionality. These will hereafter be designated as "graft
carboxyl polyurethanes". The invention further relates to novel
dispersions, coatings, and magnetic recording media containing
these graft carboxyl polyurethane polymers as dispersants and
binders for magnetic and/or non-magnetic pigments. The invention
further relates to dispersions, coatings and magnetic recording
media comprising graft carboxyl polyurethanes in combination with
quaternary ammonium compounds.
[0002] The invention further relates to the use of a toughened
polyisocyanate curative in combination with the novel graft
carboxyl polyurethanes in dispersions, coatings, and magnetic
recording media.
[0003] The invention further relates to the use of carboxylic acid
functional polyurethanes not having a graft structure but having a
carboxylic acid content of greater than 0.2 milliequivalents of
carboxyl group per gram of polymer (hereafter designated as
"carboxyl polyurethanes") in combination with a quaternary ammonium
polymer and, optionally, a toughened polyisocyanate curative in
dispersions, coatings, and magnetic recording media.
[0004] The invention further relates to graft carboxyl
polyurethanes which are prepared from a reaction mixture containing
a quaternary ammonium functional polyol, as well as a carboxylic
acid functional polyol and other components. The invention further
relates to the use of these quaternary ammonium graft carboxyl
polyurethanes in dispersions, coatings, and magnetic recording
media.
BACKGROUND OF THE INVENTION
[0005] Magnetic recording media generally include a binder
dispersion layer comprising a binder and one or more pigments
overlying a substrate, wherein the pigments are dispersed within
the binder. Typically, the pigments are magnetizable pigments
comprising small, magnetizable particles. In some instances, the
medium may be in the form of a composite having both back-coat and
front-coat binder dispersion layers, although the pigment in the
back-coat may or may not be a magnetizable pigment.
[0006] It has become desirable to have as high a loading of
magnetizable pigment in the magnetic recording media as is
reasonably possible. It is often preferred to have a binder
dispersion comprising from about 70% to 85% by weight magnetizable
pigment relative to the binder with as many magnetizable particles
per unit area or unit volume as possible. It is also preferred to
have a binder dispersion in which the magnetizable pigment
comprises a plurality of small particles having a relatively high
specific surface area. Higher pigment loading has the potential to
provide high density magnetic recording media capable of storing
more information.
[0007] Problems, however, remain in the art concerning magnetic
recording media having a relatively high loading of very high
surface area magnetizable pigment. To begin with, magnetizable
pigments tend to agglomerate, and they are difficult to properly
and fully disperse within the binder. Wetting agents, or
dispersants, are often employed to facilitate such dispersion. For
higher pigment loading, that is, the use of greater amounts by
weight and number of magnetizable particles, greater amounts of
such dispersants are required, which is not always desirable.
[0008] There are a number of reasons for using as little dispersant
as possible. Dispersants tend to soften binder systems, decrease
their toughness, and adversely affect their cure. Binders without
dispersants can be more readily and reproducibly prepared. Further,
excess dispersant may bloom from a cured binder system over time,
leading to contamination of a recording head or the like, causing a
change in the physical or chemical characteristics of the
media.
[0009] To help alleviate these problems with added dispersants,
polymeric dispersant binder compositions having chemically bound
dispersants have been developed. Such compositions comprise
polymers with polar functional moieties pendant from the polymer
backbone that help disperse pigments. As a result of using these
compositions, less dispersant or, in some instances, no dispersant
is needed for dispersion of magnetic pigment in the binder.
Commercially available polymeric dispersants for magnetic recording
media applications typically contain a relatively low quantity of
polar functional moieties, which are usually carboxyl or sulfonate
groups present at levels less than about 0.1 milliequivalents of
carboxyl or sulfonate group per gram of polymer. A higher degree of
pigment-polymer interaction is often desired for purposes of
dispersion and coatings stability, particularly in the case of
pigments exhibiting small particle size, such as iron metal
particles and barium ferrite.
[0010] Polyurethanes containing high levels of carboxylic acid
functionality are known. U.S. Pat. No. 4,983,491 and U.S. Pat. No.
4,898,803 to Fuji describe polyurethanes said to be useful in a
photolithographic application which are the reaction product of a
diol having a carboxyl group with a diisocyanate. These materials
have a carboxylic acid content of greater than 1.0 meq/g. Their use
of these polyurethanes is unrelated to dispersion formation or
magnetic recording. Graft carboxyl polyurethanes are not
taught.
[0011] U.S. Pat. No. 4,571,364 (to Fuji Photo Film Co.) discloses
polyurethane resins for magnetic binders in which polar groups
including carboxyl, may be incorporated into the polymer. The
claimed polar group content is greater than 0.1 meq/q. The sole
example of a polyurethane containing carboxyl groups is Example 3.
Example 3 is described in a referenced Japanese Patent Publication
(No. 38760/78) to contain a water based polyurethane which is said
to have 0.5 meq/g carboxyl groups. U.S. Pat. No. 4,788,103 to Fuji
Photo Film Co. describes polyurethanes used as magnetic pigment
binders having 0.03 to 2 weight percent carboxyl group (0.007 to
0.4 meq/g). Neither combinations with quaternary ammonium compounds
nor graft side chains are taught.
[0012] U.S. Pat. Nos. 4,529,661 and 4,613,545 to Sony Corp.
describe binders, including polyurethane binders, having polar
groups, including carboxyl groups, at levels of from 200 to 50,000
grams of polymer per mole of polar group (0.02 to 5 meq/g). There
are no examples of carboxyl containing polyurethanes in these
patents.
[0013] U.S. Pat. No. 5,165,999 to Fuji Photo Film describes
polyurethanes prepared from amino carboxylic acid diols used in
magnetic recording media. Blending with a vinyl chloride type resin
containing a polar group including quaternary ammonium polar group
is also described. The claims are expressed in terms such that a
carboxyl content range cannot be calculated. The level of
carboxylic acid functionality in the examples is about 0.07 meq/g
(about 14,000 grams polymer per mole of carboxyl group).
[0014] Copending U.S. patent application Ser. No. 08/054,511 and
U.S. patent application Ser. No. 08/054,312, assigned to the
assignee of the present invention, describes the use of
polyurethanes with chelating carboxyl groups pendant from their
backbone as magnetic recording media binders. These carboxyl groups
are not formed from the copolymerization of carboxylic acid
functional polyols but rather are formed from the reaction of an
anhydride with a hydroxyl functional polyurethane. It is difficult
to prepare a polyurethane with high carboxyl content, high
macromonomer content and high molecular weight by this method
because a precursor polyurethane must be prepared having a high
level of free hydroxyl groups. The claimed range of such carboxyl
groups is 1000 to 100,000g/eq (0.01 to 1.0 meq/g) and in some cases
they can also incorporate a vinyl polymerized macromonomer and be
blended with polymers having quaternary ammonium salts.
[0015] U.S. Pat. No. 5,244,739 assigned to the assignee of the
present invention, describes the use of vinyl polymeric
macromonomer diols in polyurethane polymers useful in magnetic
recording media. A sulfonate polar group was incorporated into some
of these polymers at levels of 5000 to 30,000 g/eq (0.03 to 0.2
meq/g). Carboxyl polar groups are not taught.
[0016] Quaternary ammonium functional polymers are known to the
magnetic recording media art. Examples of quaternary ammonium
functional polymers include vinyl chloride copolymers,
non-halogenated styrene copolymers, polyurethanes and
polyethers.
[0017] Examples of quaternary ammonium functional polyurethane
magnetic binders include those disclosed in U.S. Pat. No. 4,286,022
(to 3M Co.), Japanese Patent Publication No. 03/188178, 04/307420,
Japanese Patent Publication No. 06/80528 and Japanese Patent
Publication No. 95/19355.
[0018] Quaternary ammonium functional vinyl chloride copolymer
magnetic binders are known and commercially available. Examples are
described in U.S. Pat. No. 4,784,913 (to Nippon Zeon Co., Ltd.),
and U.S. Pat. No. 4,861,683 (to Sekisui Chemical Company,
Ltd.).
[0019] Quaternary ammonium functional nonhalogenated vinyl
copolymers are described in copending U.S. patent application Ser.
No. 08/054,312, assigned to the assignee of the present invention,
which describes their use as magnetic binders.
[0020] Isocyanate functional polyurethane prepolymers containing
oligomeric polyol segments used in magnetic recording media
formulations are described in U.S. Pat. Nos. 3,150,005; 3,490,945
and 5,221,582.
SUMMARY OF THE INVENTION
[0021] A need exists for a binder composition which is capable of
very strong binding of pigment particles yet which produces smooth,
high loading dispersions with fluid rheology. For magnetic
recording media applications, there is a need to obtain pigmented
coatings with excellent magnetic and mechanical properties, as well
as backside coatings which are smooth and durable.
[0022] We have discovered such a binder, magnetic media produced
therefrom and from other binders, and magnetic and non-magnetic
pigmented coatings produced therefrom. We have found that
polyurethanes containing high levels of carboxyl functionality and
graft side chains (termed "graft carboxyl polyurethanes") can
produce fluid dispersions from many different pigments, including
difficult to disperse magnetic pigments, at high ratios of pigment
to binder.
[0023] Without wishing to be bound by any particular theory, it is
speculated that the graft side chains of the novel graft carboxyl
polyurethanes of the invention act as polymeric barriers between
particles in a dispersion, preventing flocculation (i.e., steric
stabilization). We have found that the novel graft carboxyl
polyurethanes of this invention are more effective at providing
stabilization to magnetic particle dispersions than any other
polyurethanes of which we are aware.
[0024] We have found that the combination of graft carboxyl
polyurethanes with a quaternary ammonium compound, or the
incorporation of a quaternary ammonium polyol into the graft
carboxyl polyurethane, can produce even more fluid dispersions
which show improved gloss and, when magnetic particles are used,
magnetic orientation. Though the carboxyl polyurethanes of the
invention interact strongly with pigments, this surprisingly does
not interfere with the dispersion stabilization action of the
quaternary ammonium compound when present. It is speculated that
the two components operate by independent mechanisms to provide
dispersion stabilization.
[0025] We have found that, since the graft carboxyl polyurethanes
of the invention are such efficient dispersants, it is possible to
add high levels of very tough polyisocyanate curatives to
dispersions prepared from them, without sacrificing dispersion
quality. Such curative containing dispersions can be coated, dried
and cured to produce coatings of distinctly superior properties. In
particular these properties include high toughness, good
durability, good slit edge quality and high magnetic recording
output.
[0026] While graft side chains provide excellent improvements in
dispersion stability, they do not always contribute strongly to
polymer mechanical properties. We have found that combinations of
non-grafted but highly carboxylated polyurethanes, which we term
"carboxyl polyurethanes", with quaternary ammonium polymers can
produce acceptable dispersions. This binder combination has a
similar level of carboxyl functionality and thus a similar level of
pigment polymer interaction to that of the graft carboxyl
polyurethanes. Toughened polyisocyanate curatives can optionally be
added to these dispersions to yield, when coated, coatings with
highly desirable properties of toughness and environmental
stability.
[0027] One aspect of the invention relates to a novel carboxylic
acid functional graft carboxyl polyurethane polymer comprising the
reaction product of a mixture comprising:
[0028] (a) one or more polyisocyanates;
[0029] (b) a macromonomer(s) having a number average molecular
weight greater than about 500 and one to two isocyanate-reactive
groups (groups which are reactive with isocyanate) selected from
the group consisting of hydroxyl, primary amino, secondary amino
and mercapto groups; and wherein if two isocyanate-reactive groups
are present, they are separated by no more than about 10 atoms
within the macromonomer molecule;
[0030] (c) a carboxylic acid functional polyol;
[0031] (d) optionally one or more quaternary ammonium polyols;
[0032] (e) optionally one or more polyols, wherein the polyols(s)
of element (e) are defined to exclude components of element(s) (b),
(c), and (d);
[0033] wherein the number of isocyanate-reactive groups present in
the mixture prior to reaction exceeds the number of isocyanate
groups; and wherein the macromonomer (b) content comprises from
about 5% to about 95% by weight based on the weight of the graft
carboxyl polyurethane polymer; and wherein at least about 0.2 meq
of carboxylic acid groups are present on the graft carboxyl
polyurethane polymer per gram of graft carboxyl polyurethane
polymer. Preferably the macromonomer content comprises from about
20% to about 80% by weight based on the weight of the polymer.
Preferably at least about 0.4 meq of carboxylic acid group are
present on the polymer per gram of polymer.
[0034] The reactants can be added to the reaction mixture in a
various ways to produce the polyurethanes of the present invention.
For example, (a), (b) and (c) may be allowed to react to completion
followed by addition of (d) and/or (e) or, alternatively, (a), (b),
(c),(d), and (e) may be added together and allowed to react until
all isocyanate groups are consumed. Alternatively (a), (b), (c),
and (d) may be combined and allowed to react followed by the
addition of and reaction with (e). As another example (a), (b),
(c), and (e) may be combined to react until all isocyanate groups
are consumed. Typically a solvent is used and the product is
solvent soluble. The product has a backbone rich in acid groups and
has a graft structure whose pendant (graft) side chains are the
result of the reaction of the macromonomer into the polyurethane. A
non-limiting example of such a polymerization is shown below as
Reaction I: 1
[0035] Another aspect of the invention relates to a dispersion
comprising:
[0036] (a) one or more of the graft carboxyl polyurethane polymers
described above;
[0037] (b) optionally a quaternary ammonium compound(s);
[0038] (c) one or more pigments selected from the group consisting
of magnetic pigments, non-magnetic pigments, and mixtures
thereof;
[0039] (d) an organic solvent; and
[0040] (e) optionally a polyisocyanate curative.
[0041] Preferably about 0.3 to about 30 millimoles of quaternary
ammonium group are present in the dispersion per kilogram of
pigment.
[0042] Preferably about 20 to about 60 weight percent of the
polyisocyanate curative (e) is present in the coating based upon
the total weight of the coating exclusive of pigment, wherein the
curative (e) is the reaction product of a mixture comprising:
[0043] (i) one or more diisocyanates; and
[0044] (ii) one or more polyols;
[0045] wherein at least one of the polyols of (ii) is an oligomeric
polyol of number average molecular weight between about 500 and
5000 having a glass transition temperature less than about
0.degree. C. and wherein said oligomeric polyol comprises between
about 10 and about 80% by weight of the curative and wherein the
overall ratio of hydroxyl to isocyanate functionality in the
mixture of element (e) prior to reaction is less than 1.
[0046] Another aspect of the invention relates to a coating
comprising this dispersion dried of solvent.
[0047] Another aspect of the invention relates to a magnetic
recording medium comprising the above coating on at least one side
of a substrate.
[0048] Another aspect of the invention relates to a dispersion
comprising:
[0049] (a) one or more of carboxyl polyurethane polymers comprising
the reaction product of a mixture comprising:
[0050] (i) one or more polyisocyanates;
[0051] (ii) a carboxylic acid functional polyol(s);
[0052] (iii) optionally one or more polyols, wherein the polyols(s)
of element (iii) are defined to exclude components of element(s)
(a)(ii);
[0053] wherein the number of isocyanate-reactive groups present in
the mixture prior to reaction exceeds the number of isocyanate
groups and wherein at least about 0.2 meq of carboxylic acid group
are present on the carboxyl polyurethane polymer per gram of
carboxyl polyurethane polymer;
[0054] (b) a polymeric quaternary ammonium compound(s) having a
number average molecular weight of at least about 500;
[0055] (c) one or more pigments selected from the group consisting
of magnetic pigments, non-magnetic pigments, and mixtures thereof;
and
[0056] (d) an organic solvent; and
[0057] (e) optionally a polyisocyanate curative.
[0058] Preferably about 20 to about 60 weight percent of the
polyisocyanate curative (e) is present in the coating based upon
the total weight of the coating exclusive of pigment, wherein the
curative (e) is the reaction product of a mixture comprising:
[0059] (i) one or more diisocyanates; and
[0060] (ii) one or more polyols;
[0061] wherein at least one of the polyols of (ii) is an oligomeric
polyol of number average molecular weight between about 500 and
5000 having a glass transition temperature less than about
0.degree. C. and wherein said oligomeric polyol comprises between
about 10% and about 80% by weight of the curative and wherein the
overall ratio of hydroxyl to isocyanate functionality in the
mixture of element (e) prior to reaction is less than 1.
[0062] Another aspect of the invention relates to a coating
comprising this dispersion dried of solvent.
[0063] Another aspect of the invention relates to a magnetic
recording medium comprising the above coating on at least one side
of a substrate.
[0064] The use of the above mentioned polyisocyanate curatives in
the dispersions and coatings of the invention is particularly
effective. The use of relatively high levels of these tough
curatives provides a large increase in the toughness of the
finished coatings when the dispersions are dried. Up to about 60%
by weight of the binder materials in the coatings of this invention
can be curative.
DETAILED DESCRIPTION OF THE INVENTION
[0065] The present invention provides novel graft carboxyl
polyurethane polymers and magnetic media dispersions and coatings
comprising said polymers. The invention further provides novel
magnetic recording media comprising non-grafted carboxyl
polyurethane polymers in combination with polymeric quaternary
ammonium compounds.
[0066] I. Graft Carboxyl Polyurethane Polymers and Carboxyl
Polyurethane Polymers
[0067] The polymers useful in the present invention may be prepared
by the reaction of the desired components in the presence or
absence of a solvent. Preferably, the polymerization is carried out
in the presence of an organic solvent selected from the group
consisting of methylethyl ketone, tetrahydrofuran, methylisobutyl
ketone, cyclohexanone, toluene and mixtures thereof. Most
preferably, the solvent is selected from the group consisting of
methylethyl ketone and tetrahydrofuran.
[0068] A catalyst may be added to promote the reaction, i.e., a tin
catalyst such as dibutyltin dilaurate. The reaction components may
be introduced into the reaction medium individually in stepwise
fashion in order to decrease the random nature of the copolymer.
Alternatively, all of the constituent ingredients may be added to
the reaction medium prior to initiating the reaction, in a batch
polymerization process, which produces an essentially random
polyurethane copolymer. The order of addition of ingredients may
have an effect on the viscosity of the resultant polyurethane, and
a skilled practitioner would be able to determine which order will
produce a desired viscosity.
[0069] Typically, to prepare the novel graft carboxyl polyurethane
of the invention, a reaction mixture of a carboxylic acid
functional polyol, a macromonomer having isocyanate-reactive
groups, an optional polyol, a polyisocyanate, an optional catalyst
and solvent is charged to a vessel such that the ratio of
isocyanate groups to isocyanate-reactive groups is less than one.
The reaction is typically heated to about 80.degree. C. with
stirring under anhydrous conditions until the reaction is complete.
The polymer product contains side chains which comprise about 5% to
about 95%, preferably about 20 to about 80%, of the polymer's total
weight, which are derived from the macromonomer. When the
macromonomer has only one isocyanate-reactive group, it is
preferred to use at least an equimolar amount of a triol in order
for the polymerization to achieve a high molecular weight. The
number average molecular weight of the product is typically about
2000 to about 50,000, preferably about 5000 to about 30,000.
[0070] Typically, to prepare a carboxyl polyurethane without a
graft structure, the synthetic procedure is the same as for the
graft carboxyl polyurethane except that no macromonomer is included
in the reaction.
[0071] I(a). Polyol
[0072] The term "polyol" as used herein refers to polyhydric
alcohols containing an average of one or more hydroxyl groups and
includes, for example, monohydric alcohols, diols, triols, tetrols,
etc.
[0073] I(a)(i). Diols
[0074] A preferred class of polyols is diols. A variety of diols
may be utilized according to the invention including both low
molecular weight and oligomeric diols. Also, mixtures of diols can
be used.
[0075] I(a)(i)(1) Low Molecular Weight Diols
[0076] Low molecular weight (less than about 500 number average
molecular weight) diols may be used to provide preferred hardness
characteristics to the polymer and the magnetic media prepared
therefrom. Some representative examples of these are ethylene
glycol; propylene glycol; 1,3-propane diol; 1,4-butane diol;
1,5-pentane diol; 1,6-hexane diol; neopentyl glycol; diethylene
glycol; dipropylene glycol; 2,2,4-trimethyl-1,3-pentane diol;
1,4-cyclohexanedimethanol; ethylene oxide and/or propylene oxide
adduct of bisphenol A; and ethylene oxide and/or propylene oxide
adduct of hydrogenated bisphenol A. Examples of other diols which
may be useful include diols having polar functional groups, diols
bearing ethylenic unsaturation, such as 3-allyloxy-1,2-propanediol,
1-glyceryl (meth)acrylate, 2-glyceryl (meth)acrylate,
2-methylene-1,3-propane diol, pentaerythritol di(meth)acrylate,
trimethylolpropane monoallyl ether,
2-acrylamido-2-hydroxyethyl-1,3-propanediol,
N,N-diallyltartardiamide and N-allyl-2,2'-iminodiethanol, and
fluorinated diols such as
C.sub.8F.sub.17SO.sub.2N[(CH.sub.2).sub.2OH].sub.2. It is further
noted that for any of the reactants mentioned, mixtures of
materials can be utilized.
[0077] I(a)(i)(2) Oligomeric Diols
[0078] A preferred class of polyols is oligomeric polyols defined
as polyols having a number average molecular weight between about
500 and about 5000. Preferred members of this class are polyester
diols, polyether diols and polycarbonate diols having a hydroxyl
equivalent weight of from about 250 to about 3,000 (g/eq). Such
materials include polyester (polycaprolactone) diols such as
TONE.TM. 0210, available from Union Carbide Company, having a
hydroxyl equivalent weight of about 415. Another such material is
Ravecarb.TM. 106, a polycarbonate diol from Enichem America, Inc.
having a number average molecular weight of about 2000
(polyhexanediol carbonate).
[0079] Other useful oligomeric polyols include but are not limited
to those selected from the group consisting of: polyether diols
such as polytetramethylene glycols and polypropylene glycols;
polyester diols such as a polyester diol that is the reaction
product of a mixture of adipic and isophthalic acids and hexane
diol; polyether triols; and polyester triols. It is further noted
that for any of the reactants mentioned, mixtures of materials can
be utilized.
[0080] I(a)(ii). Macromonomers
[0081] A variety of macromonomers can be used according to the
present invention. In order to be used in this invention, a
macromonomer must have a number average molecular weight of at
least about 500 (preferably between about 500 and about 10,000) and
it must have either one or two groups pendant from the backbone of
the polymeric material which are reactive towards isocyanate
(isocyanate-reactive groups). It is further required that, when two
isocyanate-reactive groups are present, they are separated from
each other by less than about 10 atoms. This ensures the formation
of a graft or comb structure when the macromonomers are
incorporated into the polyurethanes of the invention. For purposes
of this invention, isocyanate-reactive groups are the following:
hydroxyl, mercapto, primary amino, and secondary arnino. Typically
the one or two isocyanate reactive groups pendant from the backbone
of the macromonomer are located at one end of the macromonomer
molecule and the rest of the molecule is soluble in solvents used
to prepare the polymers and dispersions of the invention. Some
general structures of typical macromonomers are shown below: 2
[0082] where X is an isocyanate-reactive group and R is a polymeric
group (preferably an organic polymeric group) of number average
molecular weight greater than about 500 having no
isocyanate-reactive groups.
[0083] When copolymerized into a polyurethane polymer,
macromonomers become the source of pendant polymeric segments (i.e.
the "R" polymeric groups). The graft-carboxyl polyurethane backbone
typically possesses on average about 0.5 to about 5 pendant
polymeric segments. The weight ratio of the polyurethane backbone
to the pendant polymeric segment(s) ranges typically from about
95:5 to about 5:95, preferably about 80:20 to about 20:80. The
number average molecular weight of each pendant polymeric segment,
and the macromonomer used in forming it, typically ranges from
about 1000 to about 20,000, preferably about 3000 to about 10,000.
The glass transition temperature of the pendant polymeric
segment(s) typically range from about -60.degree. C. to about
150.degree. C. For magnetic binder use, a preferred mode is to
prepare a polyurethane using a high glass transition temperature
macromonomer, typically above about 50.degree. C., preferably about
80.degree. C. to 110.degree. C. in order to obtain high hardness,
stiffness and dimensional stability. It is also preferred to
prepare polyurethanes that are tougher but not as hard, using lower
Tg macromonomers such as hydroxyl functional polylactone
macromonomers.
[0084] Macromonomers useful in the current invention can be
prepared by polymerization methods known to those skilled in the
art including, for example, radical polymerization, anionic
polymerization, cationic polymerization, condensation
polymerization, and ring opening polymerizations. Some preferred
materials described below are vinyl polymeric macromonomer diols
prepared by polymerization of vinyl monomers and polylactone
macromonomer alcohols obtained by ring opening polymerization.
[0085] I(a)(ii)(1) Hydroxyl Functional Vinyl Polymeric
Macromonomers
[0086] A hydroxyl functional vinyl polymeric macromonomer is, for
purposes of this invention, a diol or monohydric alcohol containing
a vinyl polymeric segment which contains no additional
isocyanate-reactive groups. It provides a method of incorporating
vinyl polymeric segments into polyurethane polymers. These hydroxyl
functional vinyl polymeric macromonomers can be prepared by
conventional methods known to those skilled in the art, such as
those described in Chuyo et al., Polymer Bulletin, 8, 239 (1982).
That reference teaches that vinyl monomers may be free radically
polymerized in the presence of mercaptopropanediol to give a vinyl
polymeric segment terminated by a moiety containing two hydroxyl
groups. This gives a diol of the following general structure: 3
[0087] Hydroxyl functional vinyl polymeric macromonomers may also
be prepared by anionic, cationic, and group transfer polymerization
methods.
[0088] Some hydroxyl functional vinyl polymeric macromonomers are
available commercially. Examples of useful hydroxyl functional
vinyl polymeric macromonomers include but are not limited to those
available from Toagosei Chemical Industry Co., Ltd. that have a
number average molecular weight of about 6000 and possess diol
functionality at one end. The hydroxyl functional vinyl polymeric
macromonomer can comprise methylmethacrylate monomer, (available
under the trade designation HA-6 from Toagosei), styrene monomer
(available under the trade designation HS-6 from Toagosei), and a
combination of styrene and acrylonitrile monomer (available under
the trade designation HN-6 from Toagosei).
[0089] Other polymerizable monomers can be used in preparing useful
hydroxyl functional vinyl polymeric macromonomers. Examples of
monomers which are useful in preparing hydroxyl functional vinyl
polymeric macromonomers which are useful in preparing the
copolymers of the present invention include but are not limited to
those selected from the group consisting of styrene, halogenated
styrenes, alkylated styrenes, methoxystyrenes, acrylonitrile,
acrylamide, methacrylamide, methylmethacrylate, methyl acrylate,
ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl
acrylate, isobornyl acrylate, glycidyl acrylate, vinyl chloride,
vinylidene chloride, vinyl acetate, vinylidene fluoride,
N-ethylperfluorooctanesulfonamidoethyl acrylate,
N-ethylperfluorooctanesulfonamidoethyl methacrylate,
N-butylperfluorooctanesulfonamidoethyl acrylate,
N-butylperfluorooctanesu- lfonamidoethyl methacrylate,
N-methylperfluorooctanesulfonamidoethyl acrylate,
N-methylperfluorooctanesulfonamidoethyl methacrylate, other acrylic
acid esters and amides, other methacrylic acid esters and amides,
and mixtures thereof. Preferably, the monomer is selected from the
group consisting of styrene, methylmethacrylate, and a mixture of
styrene and acrylonitrile.
[0090] I(a)(ii)(2) Hydroxyl Functional Polylactone
Macromonomers
[0091] Hydroxyl functional polylactone macromonomers can also be
used to produce the novel graft-polyurethanes of the invention.
These hydroxyl functional polylactone macromonomers can be prepared
by the ring opening polymerization of lactones which is initiated
by a monohydric primary alcohol in the presence of heat and
catalysts. An example, where the lactone is caprolactone and the
product is a hydroxyl functional polycaprolactone macromonomer is
shown in Reaction II below: 4
[0092] We have found that such monohydric alcohol macromonomers can
be used effectively to produce the dispersing polyurethanes of the
invention. It is preferred that an equimolar or greater amount of a
triol be incorporated into the polyurethane polymerization reaction
mixture along with the macromonomer. The triol compensates for the
monofunctionality of the polylactone macromonomer and allows the
polyurethane polymerization reaction to achieve high molecular
weights if desired.
[0093] Graft carboxyl polyurethanes prepared from caprolactone
alcohols are very effective in wetting and dispersing pigments and
the polycaprolactone chains contribute a desirable level of
toughness.
[0094] A variety of lactones can be used in place of caprolactone
including, but not limited to: propiolactone, butyrolactone, and
pivalolactone.
[0095] Many monohydric primary alcohols can be used to initiate
lactone polymerization to prepare hydroxyl functional polylactone
macromonomers. Examples include: short chain alcohols such as
butanol or octanol, long chain alcohols such as stearyl alcohol,
fluorochemical alcohols and others.
[0096] The molecular weight of the hydroxyl functional polylactone
macromonomer is regulated by the amount of monohydric primary
alcohol initiator present. Number average molecular weights of from
500 to 10,000 are typical. The preferred number average molecular
weight range of the polycaprolactone macromonomer alcohols is from
about 1000 to about 5,000.
[0097] I(b) Carboxylic Acid Functional Polyols
[0098] Examples of useful carboxylic acid functional polyols
include but are not limited to those selected from the group
consisting of diols of the formula: 5
CARBOXYLIC ACID FUNCTIONAL POLYOL
[0099] where R.sub.1 is an alkyl group of 5 carbons or less and
where R.sub.2 and R.sub.3 are independently selected from the group
consisting of alkyl groups; aryl groups; aralkyl groups; polyester
segments; polyether segments; and polycarbonate segments. Preferred
carboxylic acid polyols are 2,2-bis-hydroxymethylpropionic acid and
carboxylic acid functional polyester polyols (where R.sub.2 and
R.sub.3 are independently selected from the group consisting of
polyester segments) which are prepared by the polyesterification
reaction of 2,2-bis-hydroxymethylpropi- onic acid with diacids and
diols. The reaction can be run such that the product is hydroxyl
terminated and contains free carboxyl groups from the
2,2-bis-hydroxymethylpropionic acid. Examples of this procedure and
suitable carboxylic acid functional polyester polyols are given in
Japanese Patent application No. 53/38760. A preferred commercially
available material of this type is sold under the trade designation
"Lexorez.TM. 1405-65" from Inolex Corporation which has a hydroxyl
content of about 850 grams polyol per mole of hydroxyl group and a
carboxyl content of about 1100 grams polyol per mole of carboxyl
group. Combinations of carboxylic acid functional polyols can be
used to obtain preferred properties of hardness and toughness.
[0100] I(c). Polyisocyanates
[0101] A wide variety of polyisocyanates may be utilized according
to the present invention. "Polyisocyanates" means any organic
compound that has two or more reactive isocyanate (i.e., --NCO)
groups in a single molecule that can be aliphatic, alicyclic,
aromatic or a combination thereof. This definition includes
diisocyanates, triisocyanates, tetraisocyanates, etc., and mixtures
thereof. Preferably, diisocyanates are used. Useful diisocyanates
include but are not limited to those selected from the group
consisting of diphenylmethane diisocyanate, isophorone
diisocyanate, toluene diisocyanate, hexamethylene diisocyanate,
tetramethylxylene diisocyanate, and p-phenylene diisocyanate. It is
noted that mixtures of diisocyanates can also be used.
[0102] II. Quaternary Ammonium Compounds
[0103] A variety of quaternary ammonium compounds are useful in the
present invention. These materials may be, for example, either low
molecular weight or polymeric materials such as those defined by
the formula: 6
[0104] where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are each
independently selected from the group consisting of alkyl groups,
aryl groups, aralkyl groups, polyether segments, polyester
segments, and other polymeric segments; and X.sup.-is an anion
selected from the group consisting of chloride, bromide, sulfate,
methosulfate, sulfonate, phosphate, phosphonate, and carboxylate.
The anion is preferably chloride. Preferably one to two of the
groups selected from the group consisting of R.sub.1, R.sub.2,
R.sub.3, R.sub.4 are polymeric segments, most preferably one group.
By polymeric segments it is meant that a group has a number average
molecular weight of at least about 500.
[0105] It is preferred that the quaternary ammonium compounds be
soluble in the dispersion solvent. "Soluble" quaternary ammonium
compounds are defined here as those capable of dissolving
completely when made into a 1% by weight solution in the dispersion
solvent. The levels of soluble quaternary ammonium compound
necessary to the working of the invention vary with the pigments
and solvent employed. Typically from about 0.3 to about 30
millimoles of quaternary ammonium group is present per kilogram of
pigment. The preferred range for magnetic pigment and nonmagnetic
particle dispersions is about 0.5 to about 10 millimoles quaternary
ammonium group per kilogram of pigment. Most preferred is about 0.6
to about 3 millimoles quaternary ammonium group per kilogram of
pigment.
[0106] For many applications it is preferred that the quaternary
ammonium compound be polymeric, of number average molecular weight
greater than about 500, preferably greater than about 5000, so that
it contributes to the mechanical integrity of the coatings of the
invention. Low molecular weight quaternary ammonium compounds can
be also used to provide acceptable dispersion quality only when
used with graft carboxyl polyurethanes. It is required that
polymeric quaternary ammonium compounds be used with non-grafted
carboxyl polyurethanes, for reasons of dispersion quality.
[0107] II(a) Low Molecular Weight Quaternary Ammonium Compounds
[0108] Low molecular weight quaternary ammonium compounds have
quaternary ammonium functionality and number average molecular
weights less than about 500. They give acceptable dispersion
rheology when used with the graft carboxyl polyurethanes according
to the present invention but are not preferred because they do not
contribute positively to finished coatings' properties. For
example, tetrabutylammonium chloride can be used.
[0109] II(b) Polymeric Quaternary Ammonium Compounds
[0110] Polymeric quaternary ammonium compounds have molecular
weights of greater than about 500 and are preferred over low
molecular weight quaternary ammonium compounds for use with the
graft carboxyl polymers of the invention and required for use with
non-grafted carboxyl polymers in the invention. Preferred polymeric
quaternary ammonium compounds include quaternary ammonium polyols,
quaternary ammonium polyurethanes, quaternary ammonium vinyl
chloride copolymers and quaternary ammonium non-halogenated vinyl
copolymers, and mixtures thereof.
[0111] II(b)(1) Quaternary Ammonium Polyethers
[0112] Quaternary ammonium polyethers have a polyether chain with
pendant quaternary ammonium functionality. Preferred materials
include the commercially available Emcol.TM. CC-9, Emcol.TM. CC-36,
and Emcol.TM. CC-42, available from Witco Chemical Co. They are
composed of polypropylene oxide chains of number average molecular
weight 600, 1600 and 2500, respectively, with one quaternary
ammonium chloride group per molecule. Other useful quaternary
ammonium polyethers are also available from Witco Chemical and
other vendors.
[0113] II(b)(2) Quaternary Ammonium Polyurethanes
[0114] Quaternary ammonium polyurethanes are a preferred class of
quaternary ammonium compound because they interact with carboxyl
polyurethanes and graft carboxyl polyurethanes to provide excellent
dispersion quality while acting as tough co-binders in the magnetic
recording media of the invention.
[0115] Quaternary ammonium polyurethanes have at least one
quaternary ammonium group pendant from a polyurethane chain of
molecular weight greater than about 500. They are formed from the
reaction of polyisocyanates and polyols wherein at least one of the
polyols is a quaternary ammonium polyol (further described in
section II(c)). A macromonomer as defined in section I(a)(ii) may
optionally be included in the reaction which forms the quaternary
ammonium polyurethane. It is preferred to provide a quaternary
ammonium group content in the quaternary ammonium polyurethanes of
between 5,000 and 50,000 grams polymer per mole of quaternary
ammonium group. The most preferred range of quaternary ammonium
group content is 10,000 to 30,000 grams/mole. It is preferred that
the quaternary ammonium polyurethanes have a number average
molecular weight of approximately 5,000 to 50,000.
[0116] A particularly useful type of quaternary ammonium
polyurethane can be obtained by reacting a mixture of the
quaternary ammonium polyol Emcol.TM. CC-36 with diols, triols, and
a diisocyanate such that the number of moles of triol are greater
than or equal to the number of moles of Emcol.TM. CC-36 and the
number of moles of hydroxyl groups in the mixture is greater than
the number of moles of isocyanate groups in the mixture. It is to
be expected that other quaternary polyurethanes would also work
well in the invention.
[0117] II(b)(3) Quaternary Ammonium Vinyl Copolymers
[0118] Useful quaternary ammonium vinyl copolymers have at least
one quaternary ammonium group pendant from a polymer chain formed
from polymerized vinyl monomers and have a number average molecular
weight of greater than about 500. Polymerization can be carried out
by various methods including radical, anionic or cationic, and
group transfer polymerization techniques. Quaternary ammonium
functional groups can be introduced into the quaternary ammonium
vinyl copolymer either through the use of vinyl monomers having
quaternary ammonium groups, or by polymer reactions. Vinyl monomers
having quaternary ammonium groups include but are not limited to
those selected from the group consisting of (meth)acryloyloxyethyl
trimethylammonium chloride, (meth)acrylamidopropyl
trimethylammonium chloride, (meth)acryloyloxypropyl
dimethylbenzylammonium chloride, vinylbenzyl trimethylammonium
chloride, N-(3-sulfopropyl)-N-(meth)acryloyloxyethyl-N,-
N-dimethylammonium betaine, 2-[(meth)acryloyloxy]ethyl
trimethylammonium methosulfate,
N-(3-sulfopropyl)-N-(meth)acrylamidopropyl-N, N-dimethylammonium
betaine, vinylbenzyl trimethylammonium chloride,
2-hydroxy-3-allyloxypropyl trimethylammonium chloride, and mixtures
thereof.
[0119] An example of a polymer reaction to produce quaternary
ammonium vinyl copolymers is the reaction of tertiary amines with
epoxy groups pendant from a vinyl copolymer. In order to provide a
vinyl copolymer having pendant epoxy groups for this reaction,
epoxy functional vinyl monomers may be incorporated into the vinyl
copolymer. Such monomers include, for example, glycidyl ether of an
unsaturated alcohol such as allyl glycidyl ether, a glycidyl ester
such as glycidyl (meth)acrylate, and the like.
[0120] We have found that quaternary ammonium vinyl copolymers can
be prepared which function effectively in the invention to provide
desirable properties of hardness and toughness. In general, it is
desired to provide the same level of quaternary ammonium
functionality in these polymers as in the quaternary ammonium
functional polyurethanes described above.
[0121] II(b)(3)(i) Quaternary Ammonium Vinyl Chloride
Copolymers
[0122] Quaternary ammonium vinyl chloride copolymers can be
prepared by various polymerization methods, such as emulsion
polymerization, solution polymerization, suspension polymerization,
and bulk polymerization. In any of such polymerization methods,
incremental or continuous addition of a molecular weight control
agent, a polymerization initiator, and the monomers for
copolymerization may be used when necessary.
[0123] Other types of monomers amenable to copolymerization with
vinyl chloride include but are not limited to those selected from
the group consisting of various kinds of vinyl esters such as vinyl
acetate, vinylidene chloride, acrylonitrile, methacrylonitrile,
styrene, acrylate and methacrylate esters such as methyl acrylate,
ethyl acrylate, butyl acrylate, and butyl methacrylate and other
unsaturated monomers such as vinyl ethers, acrylamide,
methacrylamide, maleic anhydride, and mixtures thereof.
[0124] Some preferred vinyl chloride copolymer resins are described
in U.S. Pat. No. 4,816,683, (assigned to Sekisui Chemical),
incorporated by reference herein. These are copolymers of vinyl
chloride, hydroxypropyl acrylate, methacryloxyethyl
trimethylammonium chloride, and methyacryloxyethyl phosphate. These
are thought to be similar to or the same as the commercially
available "S-LEC E-C" resins (E-C130 and E-C110) made by Sekisui
Chemical Co. According to information supplied by the vendor, these
are approximately 84% vinyl chloride, 16% hydroxy acrylic monomer
(by weight) and contain a fraction of a percentage of other
monomers, including a quaternary ammonium monomer.
[0125] II(b)(3)(ii). Quaternary Ammonium Functional Non-Halogenated
Vinyl Copolymers
[0126] Quaternary ammonium functional polymers prepared by vinyl
polymerization which do not employ vinyl chloride or other
halogenated vinyl monomers will be termed "quaternary ammonium
functional non-halogenated vinyl copolymers" and are useful in the
present invention. Of particular utility are the quaternary
ammonium functional non-halogenated vinyl copolymers comprising a
plurality of pendant nitrile groups, a plurality of pendant
hydroxyl groups, and at least one pendant quaternary ammonium salt
group, said copolymers having been described in copending U.S.
patent application Ser. No. 08/054,312, (assigned to the assignee
of the present invention), incorporated by reference herein.
Preferred quaternary ammonium functional non-halogenated vinyl
copolymers are copolymers of monomers comprising
(meth)acrylonitrile; a non-halogenated hydroxyl functional vinyl
monomer; a non-halogenated vinyl monomer bearing a quaternary
ammonium group; and one or more other non-halogenated vinyl
monomers. Representative examples of suitable nonhalogenated
hydroxyl functional vinyl monomers include an ester of an
(.alpha.,.beta.-unsaturated carboxylic acid with a diol, e.g.,
2-hydroxyethyl (meth)acrylate, or 2-hydroxypropyl (meth)acrylate;
1,3-dihydroxypropyl-2-(meth)acrylate;
2,3-dihydroxypropyl-1-(meth)acrylat- e; an adduct of an
.alpha.,.beta.-unsaturated carboxylic acid with caprolactone; an
alkanol vinyl ether such as 2-hydroxyethyl vinyl ether;
4-vinylbenzyl alcohol; allyl alcohol; p-methylol styrene; and the
like. Preferably, the nonhalogenated, hydroxyl functional, vinyl
monomer is selected from 2-hydroxyethyl (meth)acrylate,
2-hydroxypropyl (meth)acrylate, and mixtures thereof.
Alternatively, quaternary ammonium functional vinyl copolymers with
pendant hydroxyl groups can also be prepared by incorporating vinyl
acetate into the vinyl copolymer and then partially or fully
hydrolyzing the acetate moieties to produce hydroxyl groups.
[0127] Preferred other non-halogenated vinyl monomers include
styrene, alkyl-substituted styrenes, alkyl (meth)acrylates wherein
the alkyl group contains 1 to 4 carbon atoms, and mixtures thereof.
Most preferably, the non-halogenated vinyl monomer is selected from
the group consisting of styrene, methyl methacrylate, ethyl
methacrylate, and mixtures thereof.
[0128] One particularly preferred quaternary ammonium functional
non-halogenated vinyl copolymer useful according to the present
invention is a copolymer of monomers comprising about 5 to about 40
weight percent of (meth)acrylonitrile; about 30 to about 80 weight
percent of a nonhalogenated vinyl monomer; about 1 to about 30
percent by weight of a hydroxy functional vinyl monomer; and about
0.25 to about 10, percent by weight of a nonhalogenated vinyl
monomer bearing a quaternary ammonium moiety, based on the total
weight of the vinyl copolymer.
[0129] II(c) Quaternary Ammonium Polyols
[0130] Quaternary ammonium polyols have at least one hydroxyl group
and at least one quaternary ammonium group pendant from a polymer
chain of number average molecular weight from about 500 to about
5000. Preferred materials include commercially available materials
sold by Witco Chemical Co. under the trade designations Emcol.TM.
CC-9, Emcol.TM. CC-36, and Emcol.TM. CC-42. These are composed of
polypropylene oxide chains of number average molecular weight 600,
1600 and 2500, respectively, and they have one hydroxyl group and
one quaternary ammonium chloride group per molecule. Other
quaternary ammonium polyols which have hydroxyl groups and acetate
or phosphate counterions are also available from Witco Chemical
under the Emcol.TM. tradename and are expected to give similar
results. An example of a useful quaternary ammonium diol is
methyl-bis(2-hydroxyethyl)-octadecylammonium chloride.
[0131] III. Quaternary Ammonium Graft Carboxyl Polyurethanes
[0132] It is also preferred in some cases to incorporate a
quaternary anmnonium group into a graft carboxyl polyurethane. When
a quaternary ammonium group is incorporated into a graft carboxyl
polyurethane, blending with an additional quaternary ammonium
compound becomes optional.
[0133] One way that quaternary ammonium graft carboxyl
polyurethanes can be prepared is by combining a macromonomer diol,
a quaternary ammonium polyol (such as Emcol.TM. CC-36), a
carboxylic acid diol, and optionally other polyols with a
diisocyanate at an isocyanate/hydroxyl ratio of 1:1 or less and
causing them to react so that all of the isocyanate is consumed.
This effectively replaces some or all of the hydroxyl termini of
the graft carboxyl polyurethane or the carboxyl polyurethane with
quaternary ammonium termini. The quaternary ammonium group
equivalent weight is preferably 2,000-100,000; it is most
preferably 10,000 to 50,000.
[0134] IV. Additional Polymers
[0135] The dispersions and coatings of the invention may optionally
further comprise additional polymers (different from those present
in the dispersions and coatings) which are preferably soluble in
the dispersion solvent.
[0136] Examples of useful additional polymers include but are not
limited to those selected from the group consisting of
polyurethanes, polyesters, vinyl copolymers, and vinyl chloride
copolymers.
[0137] V. Curatives
[0138] Curatives may be added to the dispersions of the invention
in order to provide crosslinking of the coatings fonned when the
dispersions are coated and dried. This improves such properties as
debris generation and durability in magnetic recording media
coatings. It also imparts solvent resistance.
[0139] Useful curative types include polyisocyanate curatives,
toughened polyisocyanate curatives, and radiation curatives.
Exceptional properties result from the use of preferred toughened
polyisocyanate curatives in the dispersion and coatings of the
invention. Curatives are typically added to dispersions after
milling of the dispersion and just before coating.
[0140] V(a). Polyisocyanate Curatives
[0141] Typical polyisocyanate curatives known to the magnetic
recording media art cure to a glass transition temperature of
greater than about 100.degree. C. and may be used according to this
invention to produce coatings of high glass transition temperature
and hardness. A preferred type is the reaction product of an excess
of a diisocyanate with low number average molecular weight (under
about 200) diols and triols. A typical and widely used curative
comprises, for example the adduct of toluene diisocyanate with a
mixture of trimethylol propane and a diol such as butane diol or
diethylene glycol. A preferred material of this type is available
under the trade designation MONDUR.TM. CB-55N from Bayer
Corporation. Other useful high Tg curatives are available under the
trade designations MONDUR.TM. CB-601, MONDUR.TM. CB-701, MONDUR.TM.
MRS, and DESMODUR.TM. L (all available from Bayer Corporation and
CORONATE L (available from Nippon Polyurethane). Additional
isocyanate curing agents are described in U.S. Pat. No. 4,731,292,
incorporated by reference herein.
[0142] V(b) Toughened Polyisocyanate Curatives
[0143] As noted previously, it is possible to incorporate high
levels of curative (greater than about 20% based on the total
weight of the formulation solids exclusive of pigment) into the
dispersions and coatings of the invention in order to increase
their performance. However, commonly used isocyanate curatives are
of the type described in V(a), which contain no toughening segments
and may create a brittle coating when used at high levels.
[0144] It is preferable to provide a toughened polyisocyanate
curing agent which cures to a tough and flexible, rather than a
brittle, film. Useful toughened polyisocyanate curatives are
obtained as the reaction product of an excess of a polyisocyanate
with polyols, including 10-80% by weight of an oligomeric polyol
which acts as a toughening segment. The oligomeric polyols useful
in making toughened polyisocyanate curatives have a number average
molecular weight of about 500 to about 5000 and a glass transition
temperature of lower than about 0.degree. C., preferably lower than
about minus 20.degree. C. The oligomeric polyols are preferably
selected from the group consisting of a polyester diols, polyester
triols, polyether diols, polyether triols, polycarbonate diols,
polycarbonate triols, and mixtures thereof.
[0145] One of the preferred toughened polyisocyanate curatives is
made from the reaction product of CB-55N (described above), with 45
weight percent of a polycaprolactone diol of 1300 number average
molecular weight. This modification of CB-55N provides a faster
cure and a tougher coating. It is preferred in formulations in the
dispersions and coatings of the invention to use between about 20
and about 60 weight percent, most preferably about 30 to about 50
weight percent of the toughened polyisocyanate curative based upon
the weight of formulation solids exclusive of pigments.
[0146] V(c) Radiation Curing
[0147] Optionally, ethylenically-unsaturated compounds which are
crosslinkable when subjected to ionizing radiation may be present
in the dispersions and coatings of the invention. Examples of such
materials include pentaerythritol tetra(meth)acrylate,
trimethylolpropane tri(meth)acrylate, urethane (meth)acrylates, and
the like.
[0148] When ionizing radiation is used as a curing method, it is
preferred that ethylenically-unsaturated groups also be pendant
from the backbone of the graft carboxyl polyurethane and/or the
carboxyl polyurethane and/or the quaternary ammonium compound (if
present). Such pendant ethylenically-unsaturated groups may be
obtained by the introduction of one or more ethylenically
unsaturated diols into polyurethane polymerization reaction mixture
(for example as "optional polyols" in the graft carboxyl
polyurethane) or by chemical reaction of at least one unsaturated
compound which further contains a functional group which is
reactive with one or more hydroxyl groups pendant from the
polyurethane backbone.
[0149] Copolymerizable ethylenically unsaturated diols include
3-allyloxy-1,2-propanediol, 3-methacryloxy-1,2-propanediol,
pentaerythritol diacrylate, and the like. Useful hydroxyl-reactive
functional groups include, for example, isocyanate groups, acid
chloride groups, and anhydride groups. Useful functional-group
containing unsaturated compounds include but are not limited to
those selected from the group consisting of isocyanatoethyl
methacrylate, allyl isocyanate, alpha, alpha-dimethyl-m-isopropenyl
benzylisocyanate, (meth)acryloyl chloride, itaconic anhydride,
toluene diisocyanate-hydroxyalkyl (meth)acrylate adducts, and
mixtures thereof. The backbone may have one or more pendant
ethylenically unsaturated groups, typically a plurality
thereof.
[0150] VI Curing Adjuvants
[0151] Various adjuvants can be used with polyisocyanate curatives
to give a faster or more complete cure. These include catalysts
such as tertiary amines or organometallic compounds. They also
include cure enhancers which release highly reactive species upon
exposure to moisture such as ketimines, aldimines and
oxazolidines.
[0152] A useful class of compounds for this purpose is the
ketimines. Useful ketimines are the reaction (dehydration) products
of diamines with ketones. These protected amino compounds show good
pot life in anhydrous conditions in the presence of isocyanates but
hydrolyze quickly with water to regenerate diamines, which are
highly reactive towards isocyanates. Specific ketimines and
formulas are described in copending U.S. patent application Ser.
No. 08/495,942, filed Jun. 28, 1995, assigned to the assignee of
the present invention, and incorporated by reference herein. A
preferred method is to combine a modified polyisocyanate as
described in section V(b) with a ketimine which is prepared by
dehydration of a reaction mixture of Ethacure.TM. 100 (available
from Ethyl Corporation), cyclohexanone and catalyst.
[0153] VII. Dispersions
[0154] The materials described herein can be used to prepare
magnetic media such as tapes, e.g., video tapes, computer tape and
data cartridge tape, and diskettes, both single-sided and
double-sided.
[0155] Magnetizable and/or non-magnetic pigments can be readily
dispersed using the technology of the invention. The preparation of
a pigment dispersion using the technology of the present invention
is relatively straight-forward; for example, well known mixing and
milling methods such as ball milling or sand milling can be
employed.
[0156] A variety of pigments can be used including but not limited
to those selected from the group consisting of magnetizable
pigments, carbon black, titanium dioxide, and alumina. A variety of
magnetizable pigments may be used in preparing magnetic recording
media, including but not limited to those selected from the group
consisting of ferric oxides; gamma ferric oxide; cobalt doped gamma
ferric oxides; chromium dioxide; iron; iron-cobalt; cobalt; nickel;
cobalt-nickel; cobalt-phosphorus; barium ferrite; and mixtures
thereof. Mixtures of magnetic and non-magnetic pigment are also
useful in preparing magnetic recording media.
[0157] It is foreseen that a variety of loadings, densities,
solvent systems, adjuvants, etc., may be utilized.
[0158] The coated and dried dispersion of the present invention can
be readily cured using one or more of the curatives described
previously. A curative is typically added after the other
components in the dispersion are combined and milled together. The
curative is preferably added in a proportion of about 1 to 60
weight percent based upon the binder weight, preferably 10 to 50
weight percent, based upon the weight of formulation solids
exclusive of pigment.
[0159] The resulting dispersion can be readily applied to a support
such as a polyethylene terephthalate (PET) film using any of a
number of coating techniques including knife coating and gravure
coating. Examples of supports on which the magnetic coating
material can be applied include but are not limited to those
selected from the group consisting of polyesters such as
polyethylene terephthalate and polyethylene-2,6-naphth- alate;
polyolefins such as polyethylene and polypropylene; derivatives of
cellulose such as cellulose triacetate, cellulose acetate butyrate,
cellulose acetate propionate; polycarbonate; polyvinyl chloride;
polyimides; polyamides; metals such as aluminum and copper; and
paper. Immediately after coating and while the solvent is still
present and the binder is substantially uncured, the coated
substrate typically is subject to a magnetic field to orient the
magnetic particles. After coating and orienting, the coated
material is dried of solvent and then optionally calendered. The
drying and curing retains the pigment in the oriented manner.
Curing can take place either at room temperature or at elevated
temperatures (50-60.degree. C.).
[0160] Another method of cure involves irradiation of a polymeric
binder containing radiation-curable moieties such as
ethylenically-unsaturated groups. Irradiation of the coated and
dried dispersion may be achieved using any type of ionizing
radiation, e.g., electron beam radiation or ultraviolet radiation,
in accordance with practices known in the art. Preferably, curing
is achieved with an amount of electron beam radiation in the range
of from about 1 to about 20 Mrads, preferably from about 4 to about
12 Mrads, and more preferably from about 5 to about 10 Mrads of
electron beam radiation having an energy level in the range of from
about 100 to about 400 keV, preferably from about 200 to about 250
keV. Although electron beam irradiation can occur under ambient
conditions or in an inert atmosphere, it is preferred to use an
inert atmosphere as a safety measure in order to keep ozone levels
to a minimum and to increase the efficiency of curing. "Inert
atmosphere" means an atmosphere comprising flue gas, nitrogen, or a
noble gas and having an oxygen content of less than 500 parts per
million (ppm). A preferred inert atmosphere is a nitrogen
atmosphere having an oxygen content of less than about 75 ppm.
[0161] A variety of additives known to those skilled in the art can
be incorporated into the dispersions and coatings of the invention.
The dispersions and coatings can further comprise additives
including but not limited to those selected from the group
consisting of head-cleaning agents, lubricants, carbon black,
dispersants, and wetting agents. It is envisioned that lubricants
such as those disclosed in U.S. Pat. Nos. 4,731,292 and 4,784,907,
both incorporated by reference herein, could be added to obtain
desired frictional and processing characteristics. Examples of
useful lubricants include but are not limited to those selected
from the group consisting of C.sub.10 to C.sub.22 fatty acids,
C.sub.1 to C.sub.18 alkyl esters of fatty acids, and mixtures
thereof. Other examples of useful lubricants include those selected
from the group consisting of silicone compounds such as silicone
oils, fluorochemical lubricants, fluorosilicones, and particulate
lubricants such as powders of inorganic or plastic materials.
Preferred lubricants include those selected from the group
consisting of myristic acid, stearic acid, palmitic acid, and butyl
and amyl esters thereof. Typically mixtures of lubricants are used,
especially mixtures of fatty acids and fatty esters.
[0162] The dispersion may further comprise about 1 to about 10
weight percent of a wetting agent based upon the weight of the
pigment. Suitable wetting agents include but are not limited to
those selected from the group consisting of phosphoric acid esters
such as mono-phosphorylated propylene oxide adducts of glycerol,
e.g., the reaction product of 1 mole of phosphorous oxychloride
with the reaction product of 10-11 moles of propylene oxide and 1
mole of glycerine.
[0163] Examples of useful head cleaning agents include but are not
limited to those disclosed in U.S. Pat. Nos. 4,784,914 and
4,731,292, both incorporated by reference herein. Examples of such
head cleaning agents include but are not limited to those selected
from the group consisting of alumina, chromium dioxide, alpha iron
oxide, and titanium dioxide particles of a size less than about 2
microns which have a Mohs hardness of greater than about 5 and
which are added in an amount ranging from about 0.2 to about 20
parts per hundred parts of magnetic pigment.
[0164] If the binder described herein is used as a back-coat for
magnetic media, the back-coat can optionally further comprise
non-magnetizable pigments, such as, for example, those selected
from the group consisting of carbon black, graphite, aluminum
oxide, titanium dioxide, zinc oxide, silica gel, calcium carbonate,
barium sulfate, and mixtures thereof.
[0165] In the following examples, the following agents were
used:
[0166] TONE.TM. 0230 - a polycaprolactone diol from Union Carbide,
molecular weight about 1300.
[0167] TONE.TM. 0210 - a polycaprolactone diol from Union Carbide,
molecular weight about 850.
[0168] TONE .TM. 0301 - a polycaprolactone triol from Union
Carbide, molecular weight about 297.
[0169] TONE .TM. 0305 - a polycaprolactone triol from Union
Carbide, molecular weight about 540.
[0170] DBTDL - dibutytin dilaurate.
[0171] DMPA - dimethanol propionic acid,
2,2-bis(hydroxymethyl)propionic acid.
[0172] MDI - diphenylmethane diisocyanate
[0173] MEK - methylethyl ketone
[0174] HN-6 - a styrene/acrylonitrile macromonomer diol having a
molecular weight of about 6000 from Toagosei Chemical Co., LTD.
[0175] Emcol.TM. CC-36 - a quaternary ammonium polyether of the
formula
H-(OCHCH.sub.3CH.sub.2-).sub.nN.sup.+R.sub.1R.sub.2R.sub.3X.sup.-
wherein R.sub.1, R.sub.2, are ethyl, R.sub.3 is methyl and X.sup.-
is Cl.sup.- and n=25. from Witco Chemical Co.
[0176] Dowa HM-77 - an iron metal magnetic particle from Dowa
Mining Co., Ltd.
[0177] Toda B3 - an iron metal magnetic particle from Toda Kogyo
Corporation.
[0178] Toda D1- an iron metal magnetic particle from Toda Kogyo
Corporation.
[0179] Ravecarb.TM. 106 - a polycarbonate diol, molecular weight
about 2000, from Enichem America, Inc.
[0180] Estane.TM. 5703 - a polyurethane from BFGoodrich Co.
[0181] Lexorez.TM. 1405-65 - a polyester polyol produced by Inolex
Chemical Company. The typical properties of Lexorez.TM. 1405-65
include: hydroxyl equivalent weight 850, acid equivalent weight
1100.
[0182] UR8300 - a sulfonate functional polyurethane from Toyobo
Chemical Co., Ltd.
[0183] T17503 - a carboxyl functional polyurethane from Sanyo
Chemical Co., Ltd.
[0184] MR113 - a sulfonate functional vinyl chloride copolymer from
Nippon Zeon Co., Ltd.
[0185] E-C 130 - a quaternary ammonium functional vinyl chloride
copolymer from Sekisui Chemical Co., Ltd.
Definition of Terms
[0186] Equivalent Weight
[0187] The term equivalent weight, as used herein with respect to a
functionality or moiety, refers to the mass of polymer per mole, or
equivalent, of functionality.
[0188] Inherent Viscosity
[0189] The inherent viscosity of each composition was measured to
provide a comparison of the molecular weight of each composition.
The inherent viscosity was measured by conventional means using a
Wescan #50 viscometer in a water bath controlled at 25.degree. C.
to measure the flow time of 10 milliliters of a polymer solution
(0.8 grams per deciliter of polymer in tetrahydrofuran solvent) and
the flow time of the solvent. In each experiment, inherent
viscosity is reported in deciliters per gram.
[0190] Rodenstock
[0191] Rodenstock value is a measure of smoothness of a coating and
was measured using a RODENSTOCK RM-400 surface finish analyzer
commercially available from Rodenstock Co. Generally, a lower
Rodenstock value corresponds to a smoother surface.
[0192] Gloss
[0193] Gloss refers to the percentage of light incoming at
45.degree. measured via a Pacific Scientific Glossgard II
45.degree. glossometer
[0194] Gn
[0195] Gn is a dimensionless measure of coercivity distribution
measured by an MH meter or a VSM meter and given by the
expression:
Gn=(Hc)/(DHc)
[0196] where DHc is the width of the coercivity range at 1/2 peak
height. Gn is the reciprocal of the switching field
distribution.
[0197] Pigment Loading
[0198] Pigment loading is the ratio of pigment weight to the total
weight of a dried coating.
[0199] Rheology
[0200] Rheology refers to a qualitative description as to the
fluidity of a dispersion.
EXAMPLES
[0201] The detailed description includes exemplary preparations of
the polymer and polymer dispersions and coatings in accordance with
the invention and magnetic recording media prepared therefrom. All
parts, percentages, ratios, etc., throughout the Specification,
including the Examples, are by weight unless otherwise
indicated.
[0202] I. Macromonomer and Polymer Preparation
[0203] (Examples 1-20 and Comparative Examples 1-2))
[0204] Example 1 - Preparation of a Graft Carboxyl Polyurethane
Having 25% Graft Segments In a 500 ml flask, 25 g (0.01 equivalent)
of HN-6 macromonomer and 26.6 grams (0.397 equivalents) of
2,2-bis(hydroxymethyl)propionic acid were dissolved in 200 g MEK
solvent. The solution was then dried via azeotropic distillation of
50 g of MEK. To this solution, 48.4 g of MDI and 2 drops (.about.50
mg) of DBTDL catalyst were added. The solution was then heated 8
hours at reflux whereupon the reaction was complete according to
infrared analysis. This polymer contains 25% HN-6 by weight and has
a calculated carboxyl content of 2 meq/g.
[0205] Example 2 - Preparation of a Graft Carboxyl Polyurethane
Having 50% Graft Segments
[0206] In a 5 liter reaction vessel, 802.3 g (0.32 equivalents) of
HN-6 macromonomer and 276.4 g (4.12 equivalents) DMPA were
dissolved in 2396 g MEK solvent. The solution was then dried by
azeotropic distillation of 650 g of MEK. To this solution, 525.95 g
(4.21 equivalents) of MDI and 3 drops (.about.90 mg) of DBTDL
catalyst were then added. The solution was then heated 8 hours at
reflux whereupon the amount of unreacted isocyanate was not
detectable by infrared analysis. This polymer contains 50% HN-6 by
weight and has a calculated carboxyl content of 1.3 meq/g.
[0207] Example 3 - Preparation of a Graft Carboxyl Polyurethane
Having 75% Graft Segments
[0208] In a 5 liter reaction vessel, 900 g (0.36 equivalents) of
HN-6 macromonomer and 92.79 g (1.38 equivalents) DMPA were
dissolved in 2400 g MEK solvent. The solution was then dried by an
azeotrope distillation; 600 g of MEK were removed by distillation,
followed by addition of 600 g of dry MEK. Then another 600 g of MEK
was removed by distillation. To this dried solution, 207.21 g (1.65
equivalents) of MDI and 4 drops (.about.120 mg) of DBTDL catalyst
were added. The solution was heated at reflux for 24 hours until
the amount of unreacted isocyanate was not detectable by infrared
analysis. This polymer contains 75% HN-6 by weight and has a
calculated carboxyl content of 0.6 meq/g.
[0209] Example 4 - Preparation of a Graft Carboxyl Polyurethane
Having 70% Graft Segments
[0210] In a 5 liter reaction vessel was placed a 50.9% solution of
HN-6 macromonomer in MEK solvent (1500 g),
2,2-bis(hydroxymethyl)propionic acid (64.56 g), TONE.TM. 0305
(87.26 g), and MEK solvent (1400 g). The solution was dried by an
azeotrope distillation; 500 g of MEK were removed by distillation,
followed by addition of 500 g of dry MEK. Then another 500 g of MEK
was removed by distillation. After the azeotrope distillation,
175.4 g of MDI and 3 drops of dibutyltin dilaurate catalyst were
added. The solution was heated at about 75.degree. C. until the
isocyanate peak was not detectable in the IR spectrum. About 24
hours of heating was sufficient time to complete the reaction.
[0211] Example 5 - Preparation of a Carboxyl Polyurethane
[0212] In a 5 liter reaction vessel, 432.84 g (6.46 equivalents)
DMPA, 767.16 g (6.14 equivalents) MDI and 4 drops (.about.120 mg)
DBTDL catalyst were dissolved in 1800 g MEK. The solution was
heated at reflux for about 5 hours until no unreacted isocyanate
was detectable by infrared analysis. The acid content of this
polymer was calculated to be 2.7 meq/g.
[0213] Example 6 - Preparation of a Carboxyl Polyurethane
[0214] In a 5 liter reaction vessel, 201.9 g (3.01
equivalents)DMPA, 458.1 g (3.66 equivalents) MDI, 540.0 g (3.00
equivalents) of TONE.TM. 230 and 3 drops (.about.90 mg) DBTDL
catalyst were dissolved in 1800 g MEK. The solution was heated at
reflux for 10 hours whereupon no unreacted isocyanate was
detectable by infrared analysis. The acid content of this polymer
was calculated to be 1.3 meq/g.
[0215] Example 7 - Preparation of a Graft Carboxyl Polyurethane
Containing a Polylactone Macromonomer
[0216] The following materials were charged to a 250 milliliter
three neck round bottom flask: 2,2-Bis(hydroxymethyl)propionic acid
(6.6 g; 0.099 equivalents), Example # 9, (39.3 g; 0.013
equivalents), TONE.TM. 0305 (9.5 g; 0.053 equivalents) and 117 g
methylethyl ketone. Diphenylmethane diisocyanate (140.63 g; 1.125
equivalents) and 4 drops of dibutyltin dilaurate were added to the
reaction mixture. The reaction was heated under reflux (18 hours)
until there was no free isocyanate observed in the infrared
spectrum. The material had an inherent viscosity of 0.37 dl/g when
measured in tetrahydrofuran. The calculated acid content is 0.66
meq/g for this product.
[0217] Example 8 - Preparation of a Graft Carboxyl Polyurethane
Containing Two Types of Macromonomer Segments
[0218] The following materials were charged to a two liter three
neck round bottom flask: HN-6 macromonomer (137.5 g; 0.055
equivalents), 2,2-bis(hydroxymethyl)propionic acid (51.7 g; 0.772
equivalents), polylactone macromonomer from Example #9 (163.1 g;
0.054 equivalents), TONE.TM. 0305 (57.1 g; 0.317 equivalents), and
1156.7 g methylethyl ketone. A total of 568.8 g methylethyl ketone
was distilled to achieve a water content of <500 ppm.
Diphenylmethane diisocyanate (140.63 g; 1.125 equivalents), 236.84
g dry methylethyl ketone and 4 drops of dibutyl tin dilaurate were
added to the reaction mixture. The reaction was heated under reflux
(18 hours) until there was no free isocyanate observed in the
infrared spectrum. The material had an inherent viscosity of 0.35
dl/g when measured in tetrahydrofuran. The calculated acid content
was 0.7 meq/g.
[0219] Example 9 - Preparation of a Polylactone Macromonomer
[0220] .epsilon.-Caprolactone (3242.74 g; 28.445 equivalents) from
Aldrich Chemical Co. and n-octanol (147.26 g;1.130 equivalents)
were added to a five liter resin flask and degassed using vacuum
and nitrogen. Tetrabutyl titanate (0.20%; 6.78 g) was added and the
reaction was heated at 160.degree. C. for two hours. The reaction
was cooled to 145.degree. C. while pulling vacuum down to 1-5 mm
Hg. The reaction was held at 150-155.degree. C. for one hour.
Nitrogen was used to break vacuum and the material was transferred
to a sample container. 3384.8 g (99.85% yield) of a product was
obtained which had a hydroxyl equivalent weight of 3000 g/eq.
[0221] Example 10 - Preparation of a Quaternary Ammonium
Polyurethane
[0222] Ravecarb.TM. 106 (1009.4 g,1.009 equivalents),
1,4-cyclohexanedimethanol (625.9 g, 8.129 equivalents), Emcol.TM.
CC-36 (288.0 grams, 0.180 equivalents) and methylethyl ketone (3300
g) were charged to the 12 liter reaction vessel. Methylethyl ketone
(1155 g) was distilled to achieve a water content of <500 ppm.
Isophorone diisocyanate (1294.33 g 11.648 equivalents) and 0.02%
dibutyltin dilaurate were charged to the reaction vessel. The
reaction was maintained under reflux for 18-24 hours. The reaction
was determined to be complete when no hydroxyl was observed in the
infrared spectrum. Theoretical isocyanate equivalent weight at this
point was 1381.
[0223] TONE.TM. 0301 (322.56 g, 3.584 equivalents) and methylethyl
ketone (215 g) were charged to the prepolymer solution and the
reaction was maintained under reflux. After 90 minutes, additional
methylethyl ketone (2950 g) was added and the reaction was
maintained under reflux until there was no free isocyanate observed
in the infrared spectrum (36-48 hours). The product had an inherent
viscosity of 0.33 dl/g in tetrahydrofuran. The calculated
quaternary ammonium content was 0.05 meq/g.
[0224] Example 11 - Preparation of a Non-halogenated Quaternary
Ammonium Vinyl Copolymer
[0225] Styrene (161.25g), acrylonitrile (50.0g), hydroxypropyl
acrylate (37.5g), methyacryloyloxyethyl trimethylammonium chloride
(1.25g), 3-mercapto-1,2-propanediol (0.5g), methylethyl ketone
(375g) and azobisisobutyronitrile (1.25g) were charged into a liter
amber reaction bottle. The resultant admixture, which contained
some undissolved methacryloyl-oxyethyl trimethyl ammonium chloride,
was purged with N.sub.2 for 7 minutes at 1 liter per minute, after
which the bottle was sealed. The sealed bottle and its contents
were tumbled in a constant temperature bath, at 65.degree. C. to
70.degree. C. for 80 hours. The product was a clear, homogeneous
solution. The inherent viscosity in methylethyl ketone was 0.30
dl/g.
[0226] Example 12 - Preparation of a Non-halogenated Quaternary
Ammonium Vinyl Copolymer
[0227] 3.0 grams of methacryloyloxyethyl trimethyl ammonium
chloride (QMA) was predissolved in 7.5 grams of hydroxypropyl
acrylate (HPA) in a 100 ml wide mouth jar by rolling the jar
containing the two components on a rubber roller.
[0228] In a one-liter amber reaction bottle were charged the above
premix of QMA and HPA, 217 g styrene (St), 72.3 g acrylonitrile
(AN), 0.6 g mercaptopropane diol (MPD), 1.8 g
2,2'-azobisisobutyronitrile and 338 g methylethyl ketone (MEK). The
resulting clear solution was purged with nitrogen for 5 minutes at
1 LPM (liter per minute) after that the bottle was sealed and
tumbled in a constant temperature bath at 65.degree. C. for 48 hrs.
The product obtained was a clear homogeneous solution with inherent
viscosity of 0.31 dl/g and 950 cps Brookfield viscosity.
[0229] Example 13 - Preparation of a Polyisocyanate Curative
[0230] To a 12 liter flask was added 2440 grams (3.813 equivalents)
TONE.TM. 0230 caprolactone diol from Union Carbide Corporation,
5053 grams (11.44 equivalents) of CB55N from Bayer, 0.2 grams of
dibutyltin dilaurate catalyst and 2945 grams MEK. The reaction was
held at 75.degree. C. for 2 hours until no hydroxyl groups were
detectable by infrared spectroscopy. The material had a calculated
isocyanate equivalent weight of 685, a calculated molecular weight
of 2740 and a calculated functionality of 4.0. The percent solids
were 50% in MEK.
[0231] Example 14 - Preparation of a Graft Carboxyl Polyurethane
from a Carboxylic Acid Functional Polyester Polyol
[0232] HN-6 macromonomer (140.0 g; 0.056 equivalents) diluted with
444.3 g methylethyl ketone was added to a one liter 3 neck round
bottom flask containing Lexorez.TM. 1405-65 (116.5 g; 0.147
equivalents). An additional 132 g methylethyl ketone was added to
the flask. A total of 482.6 g methylethyl ketone was distilled and
replaced with 330.8 g dry methylethyl ketone to achieve a water
content of <500 ppm. Diphenylmethane diisocyanate (23.85 g;
0.191 equivalents) and 3 drops of dibutyltin dilaurate were added
and the reaction was heated to reflux. The reaction was maintained
at reflux (18-24 hours) until no free isocyanate was observed in
the infrared spectrum. The product had an inherent viscosity of
0.19 dl/g in tetrahydrofuran. An additional 1.33 g diphenylmethane
diisocyanate (0.0106 equivalents) was added and reacted to
completion. The final product had an inherent viscosity of 0.22
dl/g when measured in tetrahydrofuran. The calculated acid content
of this material was 0.33 meq/g. The T.sub.g of this polymer was
determined to be .+-.3.5.degree. C. by differential scanning
calorimetry.
[0233] Example 15 - Preparation of a Graft Carboxyl Polyurethane
Having Quaternary Ammonium Functionality.
[0234] HN-6 macromonomer (55.0 g; 0.022 equivalents), Emcol.TM.
CC-36 (17.6 g; 0.11 equivalents), n-butanol (0.8 g; 0.11
equivalents), and 252.7 g methylethyl ketone were charged to a 500
ml three neck round bottom flask which had been inerted with
nitrogen. A total of 127 g methylethyl ketone was distilled and
replaced with 32.3 g dry methylethyl ketone to achieve a water
content of <500 ppm. The reaction was cooled and the following
materials were added: 2,2-bis(hydroxymethyl)propionic acid (7.4 g;
0.110 equivalents), diphenylmethane diisocyanate (19.2 g; 0.154
equivalents) and 3 drops of dibutyltin dilaurate. The reaction was
maintained under reflux until there was no free isocyanate observed
in the infrared spectrum. The acid content was calculated to be
0.055 meq/g. The quaternary ammonium group content was calculated
to be 0.10 meq/g.
[0235] Example 16 - Preparation of a Graft Carboxyl Polyurethane
Having Quaternary Ammonium Functionality
[0236] HN-6 macromonomer (60.0 g; 0.024 equivalents), Emcol.TM.
CC-36 (9.6 g; 0.006 equivalents), n-butanol (1.3 g; 0.018
equivalents), and 253 g methylethyl ketone were charged to a 500
milliliter three neck round bottom flask which had been inerted
with nitrogen. A total of 92 g methylethyl ketone was distilled to
achieve a water content of <500 ppm. The reaction was cooled and
the following materials were added: 2,2-bis(hydroxymethyl)propionic
acid (8.0 g; 0.120 equivalents), diphenylmethane diisocyanate (21.0
g; 0.168 equivalents), and 3 drops of dibutyltin dilaurate. The
reaction was heated under reflux (16 hours) and judged complete
when there was no free isocyanate observed in the infrared
spectrum. The acid content is calculated to be 0.055 meq/g. The
quaternary ammonium group content was calculated to be 0.06
meq/g.
[0237] Example 17 - Preparation of a Carboxyl Polyurethane from a
Carboxylic Acid Functional Polyester Polyol
[0238] Lexorez.TM. 1405-65 (306.38 g; 0.388 equivalents) and 528.6
g methylethyl ketone were charged to a one liter three neck round
bottom flask which had been inerted with nitrogen. Methylethyl
ketone, (490 g) was distilled and 462 g dry methylethyl ketone was
added to achieve a water content of <500 ppm. Diphenylmethane
diisocyanate (43.62 g; 0.349 equivalents) and 3 drops of dibutyltin
dilaurate were added to the flask. The reaction was heated under
reflux 14-18 hours until no free isocyanate was observed in the
infrared spectrum. An additional 4.33 g of diphenylmethane
diisocyanate was added and reacted to completion. The final product
had an inherent viscosity of 0.32 dl/g. The calculated acid content
of this material was 0.7 meq/g.
[0239] Example 18 - Preparation of a Quaternary Ammnonium
Polyurethane Having Graft Segments
[0240] Ravecarb.TM. 106 (1084.5 g; 1.085 equivalents), HN-6
macromonomer (900.0 g; 0.360 equivalents),
1,4-cyclohexanedimethanol (268.1 g; 3.482 equivalents), Emcol.TM.
CC-36 (288.0 grams; 0.180 equivalents) and methylethyl ketone (3400
g) were charged a the 12 liter reaction vessel. Methylethyl ketone
(1196 g) was distilled to achieve a water content of <500 ppm.
Isophorone diisocyanate (766.05 g; 6.894 equivalents) and 0.02%
dibutyltin dilaurate were charged to the reaction vessel. The
reaction was maintained under reflux for 12-18 hours. The reaction
was determined to be complete when no hydroxyl was observed in the
infrared spectrum. Theoretical isocyanate equivalent weight was
1850 g/eq.
[0241] TONE.TM. 0301 (247.47 g, 2.750 equivalents) and 166 g
methylethyl ketone were added to this prepolymer solution. The
reaction was maintained under reflux for 90 minutes then diluted
with 2950 g methylethyl ketone. The reaction was maintained under
reflux until there was no free isocyanate observed in the infrared
spectrum (36-48 hours). The product had an inherent viscosity of
0.30 dl/g in tetrahydrofuran. An additional 6.35 g isophorone
diisocyanate was added along with 1.88 g
1,4-diazobicyclo[2.2.2]-octane from Aldrich Chemical Company and
reacted to completion. The final product had an inherent viscosity
of 0.42 in tetrahydrofuran. The calculated ammonium salt content
was 0.05 meq/g.
[0242] Example 19 - Large Scale Preparation of a Graft Carboxyl
Polyurethane Having 70% Graft Segments
[0243] In 300 liter reaction vessel, 12.7 kg (5.08 equivalents) of
HN-6 macromonomer, 1.45 kg (8.06 equivalents) of TONE.TM. 305 triol
and 1.08 kg 16.12 equivalents) of DMPA were dissolved in 600 g MEK
solvent. The solution was dried via an azeotropic distillation,
whereupon 2.92 kg 23.36 equivalents) of MDI and 7 g of DBTDL
catalyst were added. The solution was then heated 8 hours at reflux
until the amount of unreacted isocyanate was not detectable by
infrared analysis. This polymer contained 70% HN-6 by weight and
had a calculated carboxyl content of 0.4 meq/g.
[0244] Example 20 - Large Scale Preparation of a Quaternary
Ammonium Polyurethane
[0245] Ravecarb.TM. 106 (19.07 kg; 19.07 equivalents),
1,4-cyclohexanedimethanol (11.85 kg; 153.9 equivalents), Emcol.TM.
CC-36 (5.45 kg; 3.4 equivalents) and methylethyl ketone (52 kg)
were charged to the 200 liter kettle. Methylethyl ketone (11.4 kg)
was distilled to achieve a water content of <500 ppm. Isophorone
diisocyanate (24.5 kg; 220.9 equivalents) and dibutyltin dilaurate
(250 g) were charged to the reaction vessel. The reaction was
heated to 100.degree. C. for 3 hours. The reaction was determined
to be complete when no hydroxyl was observed in the infrared
spectrum. TONE 0301 (6.1 kg; 67.6 equivalents) and methylethyl
ketone (4.0 kg) was added to the prepolymer and heated to
100.degree. C. and held for 90 minutes. Additional methylethyl
ketone (55.8 kg) was added to the batch after the 90 minute hold.
The reaction was sampled at 3 hour increments until there was no
isocyanate peak in the infrared spectrum.
[0246] Comparative Example 1 - Preparation of a Mercaptosuccinic
Acid Functional Polyurethane Having a Carboxyl Content of 0.05
meq/g.
[0247] To a 100 liter kettle were added 7.5 kg TONE.TM. 0210
(17.7eq) polycaprolactone diol from Union Carbide Corporation, 1.9
kg neopentyl glycol (36.7 eq), and 27 kg MEK. Then 10.2 g
dibutyltin dilaurate, and 8.9 kg MDI (71.2 eq) were added. The
mixture was heated at 80 degrees Celsius for 2 hours. Then 195.8 g
mercaptosuccinic acid (1.5 eq), 6.6 kg TONE.TM. 0305
polycaprolactone triol (36.7 eq), and 9 kg MEK were added. The
reaction mixture was heated at reflux for 3 hours. An additional
charge of 590 g MDI (4.72 eq), was added and held at reflux for 3
hours. Final inherent viscosity in tetrahydrofuran was 0.28 dl/g.
Calculated mercaptosuccinic acid content was 0.05 meq/g.
[0248] Comparative Example 2 - Preparation of a Mercaptosuccinic
Acid Functional Polyurethane Having a Carboxyl Content of 0.05
meq/g and Graft Segments.
[0249] To a 2 liter reactor were added 129 g (0.3 equivalents)
TONE.TM. 0210, 29.3 g (0.65 equivalents) neopentyl glycol, 150 g
(0.06 equivalents) HN-6 macromonomer, 2 drops dibutyltin dilaurate,
and 710 g MEK. The mixture was dried by azeotropic distillation
until the water content was less than about 500 ppm. After 160.5 g
(1.28 equivalents) MDI was added, the mixture was heated at reflux
for 1 hour, whereupon 4.5 g (0.03 equivalents) mercaptosuccinic
acid was added. Then, 118 g (0.65 equivalents) TONE 0305
polycaprolactone triol and an additional 178 g MEK were added.
Heating at reflux was resumed for an additional 2 hours, after
which infrared spectroscopic analysis showed that all of the
anhydride and all of the isocyanate had been consumed. An
additional 23.3 g (0.19 equivalents) MDI was added and the mixture
was heated at reflux for an additional hour. The product showed an
inherent viscosity in tetrahydrofuran of 0.28 dl/g. The
mercaptosuccinic acid (carboxylic acid) content of the resulting
polyurethane was calculated to be 0.05 meq/g.
1TABLE I Summary of Polymers Acid % Example Type (meq/g)
Macromonomer Ex. 1 Graft carboxyl polyurethane 2 25 Ex. 2 Graft
carboxyl polyurethane 1.3 50 Ex. 3 Graft carboxyl polyurethane 0.6
75 Ex. 4 Graft carboxyl polyurethane 0.4 70 Ex. 5 Non-grafted
carboxyl polyurethane 2.7 0 Ex. 6 Non-grafted carboxyl polyurethane
1.2 0 Ex. 7 Graft carboxyl polyurethane 0.7 65 Ex. 8 Graft carboxyl
polyurethane 0.7 65 Ex. 9 Polylactone macromonomer 0 100 Ex. 10
Quaternary ammonium polyurethane 0 0 Ex. 11 Quaternary ammonium
vinyl copolymer 0 0 Ex. 12 Quaternary ammonium vinyl copolymer 0 0
Ex. 13 Curative 0 0 Ex. 14 Graft carboxyl polyurethane 0.3 50 Ex.
15 Quaternary ammonium graft carboxyl 0.5 55 polyurethane Ex. 16
Quaternary ammonium graft carboxyl 0.6 60 polyurethane Ex. 17
Non-grafted carboxyl polyurethane 0.7 0 Ex. 18 Quaternary ammonium
polyurethane 0 25 Ex. 19 Graft carboxyl polyurethane 0.4 70 Ex. 20
Quaternary ammonium polyurethane 0 0 Comp. 1 Low carboxyl content
polyurethane 0.05 0 Comp. 2 Low carboxyl content grafted
polyurethane 0.05 25
[0250] II. Preparation of Dispersions and Coatings
[0251] (Examples 21-47 and Comparative Examples 3-10)
[0252] To a steel milling container, 10 to 15 g of metal pigment, a
quantity of polymer solids based upon the pigment loading and
polymer ratios shown in Tables II and III, and enough solvent
(MEK/tolulene at an 80/20 weight ratio) to bring the overall amount
of solids to 40% were added. Approximately 190 grams of steel
milling media was added and the mix was milled for 2 hours on a Red
Devil Shaker. After 2 hours of milling, enough solvent (80/20
MEK/toluene) was added to reduce the percent solids to 30%. Milling
was then continued for another 30 minutes.
[0253] The dispersion was then allowed to cool and its fluidity was
noted. It was then coated on to a polyester film substrate using a
simple knife coating apparatus. The coating was allowed to dry at
ambient conditions. The coated surface was analyzed with a Pacific
Scientific 45.degree. glossmeter and a Rodenstock RM400 Surface
Finish Analyzer. The bulk magnetic properties of the coating were
measured with a 3000 Oe MH Meter.
[0254] The pigment loading in these experiments makes provision for
the addition of a high level of curative and other additives, but
they were not added in the experiments outlined on Tables II and
III.
2TABLE II Dispersions made with Dowa HM-77 Pigment at 88% Loading
Binder Acid Quaternary Quaternary COOH Content, Ammonium Magnetic
Example Binder Ex. # Binder Ex. # Ratio meq/g Content, meg/Kg
Rheology Gloss Rodenstock Performance, Gn Graft Carboxyl
Polyurethane Dispersions 21 -- 15 100 0.55 18 flows 99 5.0 1.25 22
-- 16 100 0.6 9.8 flows 97 4.8 1.22 23 10 3 50/50 0.6 4.1 flows 99
4.8 1.16 24 10 4 60/40 0.4 4.9 flows 95 5.4 1.12 25 10 3 60/40 0.6
4.9 flows 96 5.0 1.11 26 11 2 50/50 1.3 2 flows 82 4.9 1.08 27 10 2
50/50 1.3 4.1 flows 68 5.8 0.98 28 10 1 50/50 2.0 4.1 flows 42 7.7
0.86 29 -- 3 100 0.6 0 flows 98 6.1 1.00 30 -- 2 100 1.3 0 flows
(thick) 49 9.4 0.79 Carboxyl Polyurethane Dispersions 31 11 6 50/50
1.2 2 flows 26 22.8 0.93 32 10 5 50/50 2.7 4.9 flows 38 13.2 0.92
33 11 5 50/50 2.7 2 flows (thick) 35 8.4 0.79 Comparative Examples
Comp. 3 11 Comp. 1 50/50 0.05 2 gel 83 9.7 0.98 Comp. 4 Estane .TM.
3 50/50 0.6 0 gel 27 35.3 0.91 5703 Comp. 5 UR8300 3 50/50 0.6 0
gel 78 6.0 .97 Comp. 6 T17503 3 50/50 0.6 0 gel 56 12.4 .89 Comp. 7
UR8300 MR113 50/50 0 0 gel 62 14.5 1.07 Comp. 8 E-C130 T17503 50/50
0.05 2-4 (estimate) gel 77 9.1 1.09 (estimate) Comp. 9 -- 5 100 2.7
0 gel * * *
[0255]
3TABLE III Dispersions Made with Toda B3 Pigment Binder Quaternary
Quaternary COOH Pigment Acid Ammonium Magnetic Binder Binder
Loading, Content, Content, Performance, Example Ex. # Ex. # Ratio %
meq/g meq/Kg Rheology Gloss Rodenstock Gn Graft Carboxyl
Polyurethane Dispersions 34 10 3 50/50 83 0.6 5.1 flows 78 6.1 1.6
35 10 3 60/40 83 0.6 6.1 flows 74 6.1 1.52 36 10 3 70/30 83 0.6 7.2
flows 67 7.2 1.43 37 10 3 80/20 83 0.6 8.2 flows 46 21.1 1.38 38 12
8 50/50 85 0.7 7.8 flows 51 10.5 1.33 39 10 8 50/50 85 0.7 7.8
flows 52 10.6 1.15 40 18 4 50/50 88 0.4 5.9 flows 66 7.3 1.15 41 10
14 50/50 88 0.3 5.9 flows 68 10.4 1.13 42 10 2 50/50 88 1.3 5.9
flows 53 6.7 1.12 43 10 1 50/50 88 2.0 5.9 flows (thick) 27 10.1
1.06 44* Emcol .TM. 7/4 4/48/48 89 0.7/0.4 3.1 flows 89 6.3 1.13
CC-36 Carboxyl Polyurethane Dispersions 45 12 6 50/50 85 1.2 5.9
flows 32 14.8 1.29 46 10 17 50/50 88 0.7 5.9 flows 57 9.7 1.11 47
10 6 50/50 88 1.2 5.9 light gel 23 18.0 1.05 Comparative
Dispersions Comp. 10 10 Comp. 2 50/50 88 0.05 5.9 flows, but 23 42
1.07 very rough *Example 44 uses Toda D1 pigment instead of Toda B3
pigment
[0256] These dispersion and coating examples demonstrate for two
difficult to disperse magnetic pigments that the polymers and
dispersions of the invention provide fluid rheology where
alternative materials generally do not. While the graft carboxyl
polyurethanes have the highest smoothness and best magnetics of
all, the carboxyl polyurethane dispersions of the invention have a
fluid rheology which is a valuable advantage in processing.
Furthermore, these are test milling experiments. We have found that
with more aggressive milling conditions, the carboxyl polyurethanes
maintain a fluid rheology but develop much better magnetics,
smoothness and gloss.
[0257] The examples further illustrate that quaternary ammonium
polymers are effective in enhancing dispersion quality. In
particular quaternary ammonium polyurethanes and quaternary
ammonium functional non-halogenated vinyl copolymers are effective.
It is also very effective to incorporate a quaternary ammonium
polyol into the graft carboxyl polyurethanes.
[0258] III. Effect of low MW quaternary ammonium compound on
dispersions and coatings.
[0259] (Examples 48-53)
[0260] Low molecular weight and oligomeric quaternary ammonium
compounds can be used with the graft carboxyl polurethanes of the
invention to produce dispersions of good quality. Using the same
milling procedure described above, dispersions containing the
magnetic particle Toda B3 with a mixture of the binders Estane.TM.
5703 and example 4 in the binder ratios noted were prepared, and
their properties are shown in Table IV below.
4TABLE IV Effect of Low Molecular Weight and Oligomeric Quaternary
Ammonium Compounds Quaternary Quaternary Ammonium Magnetic Ex-
Binder ammonium Content, Roden- Performance, ample Ratio compound
meg/Kg Rheology Gloss stock Gn 48 40/60 None 0 gel 26 37.1 1.37 49
33/67 TBAC* 3.1 fluid 58 6.0 1.20 50 33/67 TBAC 9.4 fluid 72 5.8
1.42 51 33/67 Emcol .TM. CC-36 3.1 fluid 86 5.4 1.43 52 40/60 Emcol
.TM. CC-36 6.2 fluid 47 9.1 1.58 53 40/60 Emcol .TM. CC-36 12.4
fluid 52 7.8 1.50 *TBAC is tetrabutylammonium chloride
[0261] IV. Preparation of a Magnetic Recording Tape
[0262] (Example 54)
[0263] Preparation of the Dispersion:
[0264] A combination of 2.4 kg methylethyl ketone and 0.8 kg of a
40.4% solution of the resin from example 4 in methylethyl ketone
was mixed for 5 minutes. The mixing apparatus was then purged with
N.sub.2 gas.
[0265] To this mixture, 5.0 kg of iron metal particle and 0.7 kg of
methylethyl ketone were added and the resulting mixture was
transferred to a high shear double planetary mixer where it was
mixed for 2 hours under a nitrogen atmosphere.
[0266] Next, 50 g of carbon black, 0.6 kg of alumina, 0.8 kg of a
40.7% solution of the resin from example 10 in methylethyl ketone
were added, and mixing was continued for an additional hour.
[0267] The mixture was transfered to a 19 liter pail, whereupon 1.1
kg of methylethyl ketone and 2.0 kg toluene were added. The
resulting mixture was mixed for 1 hour. Finally, 4.6 kg of
methylethyl ketone and 0.5 kg toluene were added mixing was
continued for 15 minutes.
[0268] The dispersion was milled in a sandmill (eight passes) until
it was smooth. Just prior to coating, myristic acid (100 g), butyl
stearate (100 g) and curative from example 13 (431 g) were added.
The resulting dispersion was high shear mixed.
[0269] Coating the Dispersion:
[0270] The magnetic dispersion described above was coated onto a 26
gauge polyester film substrate having a carbon black backside
coating. The coated substrate was passed through an orienting
magnetic field and then through an oven set at 55.degree. C.
followed by another oven set at 82.degree. C. The coated substrate
was then calendered and rolled onto a core. The coated substrate
was then slit to 1/4 inch (6.35 mm), loaded into data cartridges,
and tested for magnetic performance and durability.
[0271] The resulting magnetic recording medium showed a gloss of
119 and a Gn value of 2.09. It showed good edge quality and low
error rates.
[0272] Data cartridges containing this media were cycled for 20,000
passes in a 41.degree. F./10% RH environment as well as an
88.degree. F./80% RH environment. Media errors were measured after
every 5,000 passes. The media showed good durability in this
test.
[0273] V. Preparation of non-magnetic backcoating
[0274] (Examples 55-56)
[0275] Dispersions were prepared by mixing the polymers noted in
Table V below with methylethyl ketone and toluene solvents so that
a 70/30 solvent ratio was obtained. The pigments were added and the
premix was stirred for three hours using a Shar.TM. mixer. The
premix was then sandmilled in a horizontal mill with a 1.0 mm
ceramic media. Dispersion smoothness required several mill passes
with a shaft speed of 1500 revolutions per minute at a flow rate of
0.25 gallons per minute. The smooth conductive dispersion required
a second solvent charge and is filtered through a 0.5 micron
filter. The controlled texture dispersion was not thinned with
additional solvent or filtered.
[0276] At the time of coating, the smooth dispersion, textured
dipsersion and crosslinking agent (CB752 from Miles, Inc.) are
Shar.TM. mixed together. The 20% solids mixture was passed through
a 1.0 micron filter, gravure coated and calendered (1000-2000 psi
at 100.degree.-140.degree. C.) for a final dry coating caliper of
25-55 microinches. The dispersions were coated onto a 26 gauge
polyester film substrate.
[0277] The phosphonated polyurethane used in these examples was
prepared as follows. To a 1-liter flask were added 67.9 g.
Ravecarb.TM. 106 polycarbonate diol, 20.8 g neopentyl glycol (0.400
eq.), 11.8 g Fyrol.TM. 6 diol available from Akzo Chemical (0.093
eq.) and 127 g MEK. Then 84.5 g diphenylmethane diisocyanate (0.676
eq.) and 0.1 g. dibutyltin dilaurate were added. The mixture was
heated at 80.degree. C. for 2 hours. Then 46.6 g TONE.TM. 0305 and
69.5 g MEK were added. The mixture was heated at reflux for 1 hour.
The inherent viscosity of the resultant polyurethane polymer in
tetrahydrofuran was 0.302 dl/g. The cured coated samples were
tested using a Wyko Laser interferometer and an 8 mm data tape
drive. Wyko RMS values of 16-20 nm showed that smooth backside
coatings were made with both examples 55 and 56. The data tape
drive was used to measure backside durability, tape drag and amound
of debris. The tape path had a pair of stationary metal guides
which the backside slid across during the forward and reverse
cycling. A sample length of 15 meters was cycled at 2 meters/second
in an 22.degree. C./52% relative humidity environment. Test results
showed that after 8000 cycles, both backside samples had excellent
durability with minimal debris and stable tape drag of 0.1-0.2
Newtons.
5TABLE V Backside Coating Formulation Parts by weight solids
Example Example Ingredients 55 56 Smooth Example 2 19.8 Conductive
(47.9% solids in MEK**) Dispersion Example 4 19.4 (37.1% solids in
MEK**) Example 10 19.8 19.4 (39.8% in MEK**) Black Pearls 2000
carbon black from Cabot Corp., 14.1 13.8 Kokomo, IN P25 titanium
dioxide from Degussa Corp., Teterboro, 28.1 27.5 NJ Ceralox APA 0.4
alumina from Ceralox Corp., 4.6 4.6 Tucson, AZ MEK (methylethyl
ketone) (29.2)* (26.5)* MIBK (methyl isobutyl ketone) (22.9)*
(19.9)* Toluene (14.4)* (16.6)* Controlled Thermax N991 carbon
black from Cancarb Ltd., 5.6 5.7 Texture Medicine Hat, Alberta,
Canada Dispersion Example 11 2.7 2.7 (44.0% solids in MEK**)
Phosphonated polyurethane resin (40.0% solids in 2.7 2.7 MEK**) MEK
(methylethyl ketone) (2.0)* (2.0)* Toluene (1.5)* (1.5)*
Crosslinking CB752 (75% solids in MEK**) from Miles, Inc., 2.6 4.2
Agent New Martinsville, WV *Denotes a 100% solvent component added
to the dispersion (numbers indicate weight percentages of solvents
used based on the total composition weight). **Although the
reagents listed in this table are often listed as being in a
solvent, the parts by weight are by weight of the dry coating
weight.
[0278] While this invention has been described in terms of specific
embodiments it should be understood that it is capable of further
modification. The claims herein are intended to cover those
variations one skilled in the art would recognize as the equivalent
of what has been done.
* * * * *