Magnetic recording medium whose magnetic layer incorporates nonhalogenated vinyl copolymer and specified polyurethane polymer

Magnetic recording medium, comprising a magnetic layer provided on a nonmagnetizable substrate, wherein the magnetic layer comprises a magnetic pigment dispersed in a polymeric binder. The polymeric binder comprises a nonhalogenated vinyl copolymer, wherein the vinyl copolymer comprises a plurality of pendant nitrile groups, a plurality of pendant hydroxyl groups, and at least one pendant dispersing group. Preferably, the binder also includes a secondary polymer component.

FIELD OF THE INVENTION 
The present invention relates to magnetic recording media, and more 
particularly to magnetic recording media whose magnetic layers contain a 
nonhalogenated vinyl copolymer with pendant nitrile groups, pendant 
hydroxyl groups, and a pendant dispersing group. The present invention 
also relates to such a vinyl copolymer itself. 
BACKGROUND OF THE INVENTION 
Magnetic recording media generally comprise a magnetic layer coated onto at 
least one side of a nonmagnetizable substrate. For particulate magnetic 
recording media, the magnetic layer comprises a magnetic pigment dispersed 
in a polymeric binder. The magnetic layer may also include other 
components such as lubricants, abrasives, thermal stabilizers, catalysts, 
crosslinkers, antioxidants, dispersants, wetting agents, fungicides, 
bactericides, surfactants, antistatic agents, nonmagnetic pigments, 
coating aids, and the like. 
Some forms of magnetic recording media, such as magnetic recording tape, 
may also have a backside coating applied to the other side of the 
nonmagnetizable substrate in order to improve the durability, 
conductivity, and tracking characteristics of the media. The backside 
coating also includes a polymeric binder and other components such as 
lubricants, abrasives, thermal stabilizers, catalysts, crosslinkers, 
antioxidants, dispersants, wetting agents, fungicides, bactericides, 
surfactants, antistatic agents, nonmagnetic pigments, coating aids, and 
the like. 
The polymeric binders of the magnetic layer and the backside coating are 
commonly derived from polymers which require curing in order to provide 
magnetic recording media with appropriate physical and electromagnetic 
properties. To prepare such media, the components of the magnetic layer or 
the backside coating, as appropriate, are combined with a suitable solvent 
and thoroughly mixed to form a homogeneous dispersion. The resulting 
dispersion is then coated onto the nonmagnetizable substrate, after which 
the coating is dried, calendered if desired, and then cured. 
The polymeric binders of magnetic recording media are most commonly 
prepared from polymer blends comprising a hard component, i.e., a polymer 
with relatively high glass transition temperature and modulus, and a soft 
component, i.e. a polymer with relatively low glass transition temperature 
and modulus. In the past, polyurethane polymers have been widely used as 
the soft component. 
Copolymers based on vinyl chloride or vinylidene chloride have been widely 
used as the hard component of choice for use with polyurethanes, due to 
their miscibility and compatibility with polyurethanes and their 
relatively high glass transition temperatures, modulii, and hardness. For 
example, Japanese Publication No. JP61-26132 describes the use of vinyl 
chloride/vinyl acetate/vinyl alcohol copolymers as a polymeric binder 
component in magnetic recording media. 
Magnetic pigments tend to agglomerate and can be difficult to initially 
disperse in the polymeric binder or be difficult to keep dispersed in the 
polymeric binder over time. Low molecular weight wetting agents, or 
dispersants, are often employed to facilitate such dispersion. For higher 
pigment loadings, i.e., the use of greater amounts by weight of magnetic 
pigment, greater amounts of wetting agent or dispersant may be required. 
This is not always desirable. Dispersants tend to plasticize binder 
systems and decrease their modulus. Further, excess dispersant may exude 
from a cured binder system over time, leading to changes in the properties 
of the media as well as to contamination of a recording head or the like. 
To help alleviate the problems associated with added low molecular weight 
dispersants or wetting agents, polymeric binders formed from 
"self-wetting" polymers have been developed. "Self-wetting" polymers have 
dispersing groups pendant from the polymer backbone that help disperse the 
magnetic pigment. Representative examples of dispersing groups include 
quaternary ammonium, amine, heterocyclic moieties, salts or acids based on 
sulfate, salts or acids based on sulfonate, salts or acids based on 
phosphate, salts or acids based on phosphonate, salts or acids based on 
carboxyl, mixtures thereof, and the like. As a result of using 
self-wetting polymers, less low molecular weight dispersant or wetting 
agent, or even no low molecular weight dispersant or wetting agent, may be 
needed to disperse the magnetic and nonmagnetic (if any) pigments in the 
polymeric binder. Self-wetting vinyl chloride copolymers have been 
described. See, e.g., U.S. Pat. Nos. 5,139,892; 5,126,202; 5,098,783; 
5,064,730; 5,028,676; 5,008,357; 4,861,683; 4,784,913; 4,770,941; and 
4,244,987. 
Vinyl chloride or vinylidene chloride copolymers, however, tend to degrade 
over time, releasing gaseous HCl which can change the properties of the 
media as well as corrode the recording head or the like. Accordingly, some 
investigators have described vinyl copolymers used in magnetic recording 
media, wherein the use of vinyl chloride and vinylidene chloride has been 
avoided. See, e.g., U.S. Pat. Nos. 5,098,783; 4,876,149; and 4,837,082; 
and Japanese Publication Nos. SHO 62-0162; SHO 54-84708; SHO 54-46519; and 
SHO 54-46518. 
What is still needed in the art, however, is a hard component for use in 
magnetic recording media which imparts high modulus and high resilience to 
magnetic recording media, but which does not contain any vinyl chloride or 
vinylidene chloride components. 
SUMMARY OF THE INVENTION 
We have now developed a magnetic recording medium whose polymeric binder 
system contains a polyurethane-compatible hard component having no vinyl 
chloride or vinylidene chloride constituents. In one aspect, the present 
invention concerns a nonhalogenated vinyl copolymer, wherein the vinyl 
copolymer comprises a plurality of pendant nitrile groups, a plurality of 
pendant hydroxyl groups, and at least one pendant dispersing group. 
In another aspect, the present invention concerns a magnetic recording 
medium. The magnetic recording medium comprises a magnetic layer provided 
on a nonmagnetizable substrate. The magnetic layer comprises a magnetic 
pigment dispersed in a polymeric binder. The polymeric binder comprises a 
nonhalogenated, vinyl copolymer as described above and a secondary polymer 
component. 
In one preferred embodiment of the present invention, the secondary polymer 
component is a polyurethane polymer, wherein the polyurethane polymer 
comprises a pendant dispersing moiety of the formula 
##STR1## 
wherein R.sup.1 R.sup.2 R.sup.3 and R.sup.4 are independently selected 
from the group consisting of --H, --OH, --COOM, --SO.sub.3 M, --SH, 
--CH.sub.2 COOM, --SCH.sub.2 COOM, --P(.dbd.O)(OM).sub.2, 
--OP(.dbd.O)(OM).sub.2, and --Y, wherein at least one of R.sup.1, R.sup.2, 
R.sup.3, and R.sup.4 comprises a moiety other than --H or --Y; 
Y is selected from the group consisting of linear alkyl groups comprising 
from about 1 to about 10 carbon atoms, branched alkyl groups comprising 
from about 1 to about 10 carbon atoms, and aryl groups comprising from 
about 6 to about 10 carbon atoms; 
M is a cation selected from the group consisting of alkali metal cations, 
H.sup.+ and ammonium cations; 
R.sup.1 and R.sup.2 together or R.sup.3 and R.sup.4 together can be cis or 
trans .dbd.CHCOOH; 
X is a divalent moiety independently selected from the group consisting of 
--CR.sup.5 R.sup.6 and --NR.sup.7 ; 
n represents an integer selected from the group consisting of 0 and 1; 
R.sup.5 and R.sup.6 are independently selected from the group consisting of 
--H, --OH, --COOM, --SO.sub.3 M, --SH, --CH.sub.2 COOM, --SCH.sub.2 COOM, 
--P(.dbd.O)(OM).sub.2, --OP(.dbd.O)(OM).sub.2, and --Y, wherein M and Y 
are as defined above; 
R.sup.7 is a monovalent moiety independently selected from the group 
consisting of --CH.sub.2 COOH, --CH.sub.2 CH.sub.2 COOH, --CH.sub.2 
CH.sub.2 N(CH.sub.2 COOH).sub.2, --(CH.sub.2).sub.6 N(CH.sub.2 
COOH).sub.2, --(CH.sub.2 CH.sub.2 O).sub.2 CH.sub.2 CH.sub.2 N(CH.sub.2 
COOH).sub.2, and --CH.sub.2 CH.sub.2 N(CH.sub.2 COOH)CH.sub.2 CH.sub.2 OH. 
In another preferred embodiment, the secondary polymer component is a 
polyurethane polymer having at least one pendant nonhalogenated vinyl 
copolymeric moiety, said vinyl copolymeric moiety of the polyurethane 
polymer comprising a plurality of pendant nitrile groups. 
As used throughout this specification, the term "nonhalogenated" means that 
the copolymer contains no covalently bound halogen atoms. Thus, the term 
"nonhalogenated" excludes vinyl halide monomers such as vinyl chloride or 
vinylidene chloride as monomeric components of the copolymer, but the term 
"nonhalogenated" does not exclude monomeric components such as 
(meth)acryloyloxyethyl trimethylammonium chloride in which chlorine is 
present as a chloride anion. 
The term "vinyl" with respect to a polymeric material means that the 
material comprises repeating units derived from vinyl monomers. As used 
with respect to a vinyl monomer, the term "vinyl" means that the monomer 
contains a moiety having a free-radically polymerizable carbon-carbon 
double bond. Monomers having such moieties are capable of copolymerization 
with each other via the carbon-carbon double bonds. 
The term "immiscible" with respect to two polymers means that a blend of 
just the two materials shows two glass transition temperatures ("T.sub.g 
's") using differential scanning calorimetry ("DSC") techniques when the 
blend is substantially free of solvent. The term "miscible", on the other 
hand, means that a blend of the two materials shows a single T.sub.g using 
DSC techniques when substantially free of solvent. 
Throughout this specification, the prefix "(meth)acryl-" means "methacryl-" 
or "acryl-". 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Magnetic recording media of the present invention comprise a magnetic layer 
provided on a nonmagnetizable substrate. The particular nonmagnetizable 
substrate of the present invention may be formed from any suitable 
substrate material known in the art. Examples of suitable substrate 
materials include, for example, polymers such as polyethylene 
terephthalate ("PET"), polyimide, and polyethylene naphthalene ("PEN"); 
metals such as aluminum, or copper; paper; or any other suitable material. 
The components of the magnetic layer comprise a magnetic pigment dispersed 
in a polymeric binder. Typically, the magnetic layer may contain 100 parts 
by weight of the magnetic pigment and 5 to 40 parts by weight of the 
polymeric binder. The type of magnetic pigment used in the present 
invention may include any suitable magnetic pigment known in the art 
including .gamma.-Fe.sub.2 O.sub.3, cobalt-doped .gamma.-Fe.sub.2 O.sub.3, 
Fe.sub.3 O.sub.4, CrO.sub.2, barium ferrite, barium ferrite derivatives, 
metal particles, and the like. 
The polymeric binder of the present invention includes a nonhalogenated 
vinyl copolymer having a plurality of pendant nitrile groups. Without 
wishing to be bound by theory, we believe that the nitrile groups may 
enhance the ability of the vinyl copolymer to interact strongly with the 
magnetic pigment, thereby facilitating dispersion of the magnetic pigment 
in the polymeric binder. We also believe that the nitrile group may 
promote the compatibility of these vinyl copolymers with polyurethanes. In 
order to provide a vinyl copolymer having pendant nitrile groups, one or 
more nitrile functional, nonhalogenated vinyl monomers may be incorporated 
into the vinyl copolymer. Representative examples of such monomers include 
(meth)acrylonitrile, .beta.-cyanoethyl-(meth)acrylate, 2-cyanoethoxyethyl 
(meth)acrylate, p-cyanostyrene, p-(cyanomethyl)styrene, and the like. 
Preferably, the nitrile functional, nonhalogenated vinyl monomer is 
(meth)acrylonitrile, and more preferably acrylonitrile. 
The vinyl copolymer of the present invention also contains pendant hydroxyl 
groups and at least one pendant dispersing group. The pendant hydroxyl 
groups of the vinyl copolymer not only facilitate dispersion of the 
magnetic pigment in the polymeric binder, but also promote solubility, 
cure, and compatibility with other polymers. The hydroxyl groups may be 
primary, secondary, or tertiary, although primary and secondary hydroxyl 
groups are preferred. Generally, preferred vinyl copolymers of the present 
invention have a hydroxyl equivalent weight in the range from about 300 to 
about 10,000, preferably 500 to 5000, more preferably 800 to 1500. 
In order to provide a vinyl copolymer having a plurality of pendant 
hydroxyl groups, one or more nonhalogenated, hydroxyl functional, vinyl 
monomers may be incorporated into the vinyl copolymer. 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)acrylate; 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; or the like. Preferably, the 
nonhalogenated, hydroxyl functional, vinyl monomer is selected from 
2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 
mixtures thereof. Alternatively, 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. 
The dispersing group, if any, of the vinyl copolymer facilitates dispersion 
of the magnetic pigment in the polymeric binder. In those instances 
wherein the vinyl copolymer includes more than one dispersing group, the 
dispersing groups may be the same, or they may be different. It is 
desirable that the vinyl copolymer have a dispersing group equivalent 
weight in the range from about 2000 to about 100,000, preferably about 
5000 to about 50,000. 
As used throughout this specification, the term "dispersing group" means 
that a group is capable of wetting the magnetic pigment. Preferably, the 
term "dispersing group" means a group that is ionized or ionizable at a pH 
in the range from 2 to 10. Representative examples of suitable dispersing 
groups include quaternary ammonium moieties (e.g., 
--N(CH.sub.3).sub.3.sup.+ Cl.sup.- as one example), amines (e.g., 
--N(CH.sub.3).sub.2 as one example), heterocyclic moieties as described in 
U.S. Pat. No. 5,081,213, sulfobetaines (e.g., --N.sup.+ (CH.sub.3).sub.2 
(CH.sub.2 CH.sub.2 CH.sub.2 SO.sub.3.sup.-)), salts or acids based on 
sulfate (e.g., --OSO.sub.3 Na as one example), salts or acids based on 
sulfonate (e.g., --SO.sub.3 Na as one example), salts or acids based on 
phosphate (e.g., --OPO(OH).sub.2 as one example), salts or acids based on 
phosphonate (e.g., --PO(OH).sub.2 as one example), salts or acids based on 
carboxyl (e.g., --COONa as one example), mixtures thereof, and the like. 
One or more dispersing groups can be introduced into the vinyl copolymer in 
a variety of ways. As one approach, dispersing initiators may be used. 
Dispersing initiators initiate copolymerization of vinyl monomers to 
provide vinyl copolymers with terminal dispersing groups. Examples of 
suitable dispersing initiators include 4,4'-azobis (cyanovaleric acid), 
succinic acid peroxide, potassium persulfate, and sodium perphosphate. 
Another approach for introducing the dispersing group into the vinyl 
copolymer is to use a functional chain transfer agent such as 
mercaptosuccinic acid during copolymerization of the vinyl monomers. 
The dispersing group may also be introduced into the vinyl copolymer 
through the use of a nonhalogenated, vinyl monomer bearing a dispersing 
group. Representative examples of suitable nonhalogenated, vinyl monomers 
bearing a dispersing group include (meth)acryloyloxyethyl trimethyl 
ammonium chloride, (meth)acryloyloxyethyl acid phosphate, 
(meth)acrylamidopropyl trimethylammonium chloride, (meth)acryloyloxypropyl 
dimethylbenzylammonium chloride, vinylbenzyl trimethylammonium chloride, 
2-hydroxy-3-allyloxypropyl trimethylammonium chloride, 
(meth)acrylamidopropyl sodium sulfonate, sodium styrene sulfonate, styrene 
sulfonic acid, (meth)acrylic acid, maleic acid, fumaric acid, maleic 
anhydride, vinyl sulfonic acid, 
2-(meth)acrylamide-2-methyl-1-propanesulfonic acid, dimethylaminoethyl 
(meth)acrylate, maleic anhydride, 
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, mixtures thereof, and the like. 
A dispersing group may also be introduced into the vinyl copolymer using 
suitable polymer reactions. Examples of suitable polymer reactions to 
provide the dispersing group include: (1) reaction of succinic anhydride 
with a portion of the hydroxyl groups on a vinyl copolymer to produce a 
vinyl copolymer with pendant acid functionality; and (2) reaction of a 
tertiary amine with the epoxy groups on a vinyl copolymer to produce a 
vinyl copolymer with pendant quaternary ammonium groups. In order to 
provide a vinyl copolymer having a pendant epoxy groups for this reaction, 
nonhalogenated, 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. 
Preferred vinyl copolymers of the present invention are copolymers of 
monomers comprising (meth)acrylonitrile; a nonhalogenated, hydroxyl 
functional, vinyl monomer as described above; a nonhalogenated, vinyl 
monomer bearing a dispersing group as described above; and one or more 
nonhalogenated, nondispersing, vinyl monomers. The term "nondispersing" 
means that the monomer bears no dispersing group and no hydroxyl group. 
Representative examples of suitable copolymerizable, nonhalogenated, 
nondispersing, vinyl monomers include styrene; alkylated styrenes; alkoxy 
styrenes; vinyl naphthalene; alkylated vinyl naphthalenes; alkoxy vinyl 
naphthalenes; (meth)acrylamides; N-vinyl pyrolidone; linear, branched, or 
alicyclic alkyl esters of (meth)acrylic acid wherein the alkyl groups 
contain from 1 to 20, preferably 1-8, carbon atoms, such as methyl 
(meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, ethyl 
(meth)acrylate, isopropyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; 
vinyl esters of alkanoic acids wherein the alkyl moiety of the alkanoic 
acids contain 2 to 20, preferably 2 to 4, carbon atoms and may be linear, 
branched, or alicyclic; isobornyl (meth)acrylate; glycidyl (meth)acrylate 
vinyl acetate; allyl (meth)acrylate, and the like. Preferred 
nonhalogenated, nondispersing, 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 
nonhalogenated, nondispersing, vinyl monomer is selected from styrene, 
methyl methacrylate, ethyl methacrylate, and mixtures thereof. 
One particularly preferred nonhalogenated vinyl copolymer of the present 
invention (hereinafter referred to as the "Preferred Vinyl Copolymer") is 
a nonhalogenated vinyl copolymer of monomers comprising 5 to 40, 
preferably 15 to 40, parts by weight of (meth)acrylonitrile; 30 to 80 
parts by weight of one or more nonhalogenated, nondispersing, vinyl 
monomers; 5 to 30 parts by weight of a nonhalogenated, hydroxyl 
functional, vinyl monomer; and 0.25 to 10, preferably 0.25 to 5, most 
preferably 0.5 to 2 parts by weight of a nonhalogenated, vinyl monomer 
bearing a dispersing group. 
For the Preferred Vinyl Copolymer, the dispersing group is preferably 
selected from quaternary ammonium, acid or salt of carboxyl, acid or salt 
of phosphate or phosphonate, acid or salt of sulfate or sulfonate, and 
mixtures thereof. More preferably, the dispersing group is quaternary 
ammonium. When the dispersing group is quaternary ammonium, it is 
preferred that the vinyl monomer bearing a dispersing group is 
(meth)acryloyloxyethyl trimethylammonium chloride. 
Preferably, the nonhalogenated, nondispersing, vinyl monomer of the 
Preferred Vinyl Copolymer is selected from styrene; an alkyl ester of 
(meth)acrylic acid wherein the alkyl group of the alkyl ester has 1 to 20 
carbon atoms; and a blend comprising styrene and such an alkyl ester 
wherein the weight ratio of styrene to the alkyl ester is in the range 
from 10:90 to 90:10. For Preferred Vinyl Copolymers containing such an 
alkyl ester, the alkyl ester is preferably methyl (meth)acrylate, more 
preferably methyl methacrylate. 
Nonhalogenated vinyl copolymers of the present invention may be prepared by 
free-radical polymerization methods known in the art, including but not 
limited to bulk, solution, emulsion and suspension polymerization methods. 
For example, according to the solution polymerization method, copolymers 
of the present invention are prepared by dissolving the desired monomers 
in an appropriate solvent, adding a chain-transfer agent, a free-radical 
polymerization initiator, and other additives known in the art, sealing 
the solution in an inert atmosphere such as nitrogen or argon, and then 
agitating the mixture at a temperature sufficient to activate the 
initiator. 
Solvents useful in such polymerizations can vary according to solubility of 
the monomers and additives. Typical solvents include ketones such as 
acetone, methyl ethyl ketone, 3-pentanone, methyl isobutyl ketone, 
diisobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, 
propanol, n-butanol, isopropanol, isobutanol, cyclohexanol and methyl 
cyclohexanol; esters such as ethyl acetate, butyl acetate, isobutyl 
acetate, isopropyl acetate, and the like; aromatic hydrocarbons such as 
benzene, toluene, xylenes, cresol, and the like; ethers such as 
diisopropyl ether, diisobutyl ether, tetrahydrofuran, tetrahydropyran, and 
dioxane; and aprotic solvents such as dimethylformamide, dimethylsulfoxide 
and the like, and mixtures thereof. The preferred solvent for preparation 
of the vinyl copolymers of the present invention is methyl ethyl ketone 
(MEK) because it is also the preferred medium in which the magnetic 
dispersions, described below, are prepared due to the ready solubility 
therein of polyurethane-vinyl copolymer blends. 
Chain transfer agents suitable for solution polymerization include but are 
not limited to alcohols, mercaptans, certain halogenated small molecules, 
and mixtures thereof. Preferably, the chain transfer agent is chosen from 
the group consisting of carbon tetrabromide, isooctylthioglycolate, 
mercaptosuccinic acid, mercaptopropane diol, dodecyl mercaptan, ethanol 
and carbon tetrachloride. Most preferably, the chain transfer agent is 
mercaptopropane diol. 
Free-radical polymerization initiators suitable for solution polymerization 
include those that are soluble in the reaction solvent and that are 
thermally activated, including but not limited to azo compounds, 
peroxides, and mixtures thereof. Useful peroxide initiators include those 
chosen from the group consisting of benzoyl peroxide, lauroyl peroxide, 
di-t-butyl peroxide and the like, and mixtures thereof. Useful azo 
compound initiators include those chosen from the group consisting of 
2,2,-azobis(2-methylbutyronitrile); 2,2,'-azobis(isobutyronitrile); and 
2,2'-azobis(2,4-dimethylpentanenitrile); each of which is commercially 
available as VAZO 67, VAZO 64, and VAZO 52, respectively, from E. I. Du 
Pont de Nemours and Co. The preferred thermal polymerization initiator is 
the VAZO 64 brand initiator because of its ease of use and its half-life 
characteristics (e.g., at 64.degree. C., half-life is 10 hours). 
Nonhalogenated vinyl copolymers of the present invention may also be 
prepared by emulsion polymerization methods. Typically, an emulsion 
comprising vinyl monomers, a chain-transfer agent and a water-soluble 
redox-type initiator system is prepared in an inert atmosphere, then 
heated carefully until a reaction exotherm occurs. The reaction mixture is 
stirred and cooled and the resulting latex is collected. Optionally, an 
ionic or nonionic surfactant may be added to the reaction mixture. 
Oxidation--reduction ("Redox") free-radical initiators useful in the 
invention include but are not limited to those chosen from the group 
consisting of tertiary amines with organic peroxides (exemplified by the 
N, N-diethylaniline--benzoyl peroxide pair); organic halides with 
transition metal complexes (exemplified by the carbon 
tetrachloride--molybdenum hexacarbonyl pair); inorganic 
oxidation--reduction systems (exemplified by the potassium 
persulfate--sodium metabisulfite pair); and organic--inorganic systems 
(exemplified by the 2-mercaptoethanol--Fe.sup.+3 pair). Inorganic redox 
initiators are preferred for the copolymers of the invention because of 
their ease of handling and useful reaction temperature range. 
In addition to the nonhalogenated vinyl copolymer, the polymeric binder of 
the present invention may also include a secondary polymer component. The 
secondary polymer component of the present invention may be any polymer, 
or combination of polymers, known in the art to be suitable as a binder 
material for magnetic recording media. Examples of polymers suitable for 
use as the secondary polymer component include thermoplastic or 
thermosetting polyurethanes, polyureas, nitrocellulose polymers, phenoxy 
resins, combinations of such polymers, and the like. Preferably, the 
weight ratio of the nonhalogenated vinyl copolymer to the secondary 
polymer component is in the range from about 1:19 to 19:1, preferably 1:5 
to 5:1, and more preferably 4:6 to 6:4. 
In preferred embodiments, the secondary polymer component is a polyurethane 
polymer. Representative examples of suitable polyurethane polymers include 
polyester polyurethanes, polyether polyurethanes, polyether polyester 
polyurethanes, polycarbonate polyurethanes, polyester polycarbonate 
polyurethanes, polycaprolactone polyurethanes, mixtures thereof, and the 
like. 
Generally, except for the polyurethanes having a pendant nonhalogenated, 
vinyl copolymeric moiety as described below, the nonhalogenated vinyl 
copolymers of the present invention and polyurethanes tend to be 
immiscible inasmuch as blends of these materials generally show two 
distinct glass transition temperatures using differential scanning 
calorimetry techniques. Notwithstanding their immiscibility, blends of 
polyurethanes with the nonhalogenated vinyl copolymers of the present 
invention provide magnetic layers with good mechanical and electromagnetic 
performance. Indeed, our experiments have shown that the durability and 
modulus characteristics of magnetic layers of the present invention are as 
good as, if not better than, the performance offered by vinyl chloride 
copolymer/polyurethane systems of the prior art. The mechanical and 
electromagnetic properties of magnetic layers of the present invention are 
also extremely stable over time. Moreover, our experiments have shown that 
magnetic layers of the present invention shed substantially less 
undesirable adherent, or "sticky", debris than similar systems 
incorporating vinyl chloride copolymers such as EC-130.TM. vinyl chloride 
copolymer or VAGH.TM. vinyl chloride copolymer. 
For example, all magnetic recording media tend to produce debris to some 
extent. Vinyl chloride copolymers of the prior art result in coatings 
which produce sticky debris. Such debris can stick to the heads or drive 
components or can transfer back onto the tape. In contrast, vinyl 
copolymers of the present invention produce nonsticky debris which tends 
to be loose and dry. Such debris is not problematic because it does not 
stick to anything or transfer back onto the media. 
As another advantage, in embodiments of the present invention incorporating 
two-phase vinyl copolymer/polyurethane systems, the glass transition 
temperature of the vinyl copolymer is not reduced by the presence of the 
polyurethane. As a result, the vinyl copolymer maintains higher modulus 
and higher thermal stability at elevated temperatures than if the vinyl 
copolymer were to be miscible with the polyurethane. 
As an option, the polyurethane polymer, or any other polymer of the 
secondary polymer component, may contain one or more pendant functional 
groups to enhance the performance of the magnetic recording medium. For 
example, the polyurethane polymer or other polymers of the secondary 
polymer component may contain carbon-carbon double bonds and/or hydroxy 
groups to facilitate crosslinking of the secondary polymer component if 
desired. As other examples of pendant functional groups, the polyurethane 
or other polymers of the secondary polymer component may contain pendant 
dispersing groups in order to facilitate dispersion of the magnetic 
pigment in the polymeric binder. In one preferred embodiment, the 
polyurethane polymer bears pendant hydroxyl groups and at least one 
pendant dispersing group. In another preferred embodiment, the 
polyurethane polymer bears pendant hydroxyl groups, at least one pendant 
dispersing group, and at least one pendant radiation curable moiety. 
Preferred polyurethane polymers of the present invention are generally 
polymers of one or more polyisocyanates and one or more polyols, Wherein 
the hydroxyl groups of the polyol(s) are in excess relative to the NCO 
moieties of the polyisocyanate(s). As used throughout this specification, 
the term "polyisocyanate" means one or more organic compounds that have 
two or more pendant NCO moieties on a single molecule. In the practice of 
the present invention, a polyisocyanate may be linear or branched 
aliphatic, alicyclic, aromatic, or the like. This definition of 
polyisocyanate includes diisocyanates, triisocyanates, tetraisocyanates, 
and mixtures thereof. Preferably, the polyisocyanate is one or more 
diisocyanates. Examples of suitable diisocyanates include diphenylmethane 
diisocyanate, isophorone diisocyanate, toluene diisocyanate, hexamethylene 
diisocyanate, tetramethylxylene diisocyanate, p-phenylene diisocyanate, 
mixtures thereof, and the like. 
As used throughout this specification, the term "polyol" means one or more 
alcohols containing two or more hydroxyl groups per molecule, including 
diols, triols, tetrols, mixtures thereof, and the like. Various kinds of 
specific polyols can be incorporated into the polyurethane in order to 
improve the polyurethane's compatibility with the vinyl copolymer. For 
example, short chain diols, i.e., diols having a molecular weight up to 
about 300, may be used to increase the hardness and urethane content of 
the resulting polyurethane. We have found that increasing the urethane 
content of a polyurethane improves its compatibility with the vinyl 
copolymer. Representative examples of short chain diols include 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-cyclohexane dimethanol, 
ethylene oxide and/or propylene oxide adduct of bisphenol A, ethylene 
oxide and/or propylene oxide adduct of hydrogenated bisphenol A, mixtures, 
and the like. 
As another example of using specific polyols to improve the compatibility 
of the polyurethane with the vinyl copolymer, diols or triols 
incorporating caprolactone may also be incorporated into the polyurethane. 
Such polycaprolactone polyols are unique because such materials have both 
polar and nonpolar characteristics. Representative examples of specific 
polycaprolactone diols and triols include TONE 0210.TM. polycaprolactone 
diol (OH equivalent weight of about 415) and TONE 0305.TM. 
polycaprolactone triol (OH equivalent weight of about 180) commercially 
available from Union Carbide Corp. 
One example of a particularly preferred polyurethane (hereinafter referred 
to as the "Half-ester Polyurethane") for use in the practice of the 
present invention is a polyurethane comprising a pendant dispersing moiety 
of the formula 
##STR2## 
wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently selected 
from the group consisting of --H, --OH, --COOM, --SO.sub.3 M, --SH, 
--CH.sub.2 COOM, --SCH.sub.2 COOM, --P(.dbd.O)(OM).sub.2, 
--OP(.dbd.O)(OM).sub.2, and --Y, wherein at least one of R.sup.1, R.sup.2, 
R.sup.3, and R.sup.4 comprises a moiety other than --H or --Y; 
Y is selected from the group consisting of linear alkyl groups comprising 
from about 1 to about 10 carbon atoms, branched alkyl groups comprising 
from about 1 to about 10 carbon atoms, and aryl groups comprising from 
about 6 to about 10 carbon atoms; 
M is a cation selected from the group consisting of alkali metal cations, 
H.sup.+ and ammonium cations; 
R.sup.1 and R.sup.2 together or R.sup.3 and R.sup.4 together can be cis or 
trans .dbd.CHCOOH; 
X is a divalent moiety independently selected from the group consisting of 
--CR.sup.5 R.sup.6 and --NR.sup.7; 
n represents an integer selected from the group consisting of 0 and 1; 
R.sup.5 and R.sup.6 are independently selected from the group consisting of 
--H, --OH, --COOM, --SO.sub.3 M, --SH, --CH.sub.2 COOM, --SCH.sub.2 COOM, 
--P(.dbd.O)(OM).sub.2, --OP(.dbd.O)(OM).sub.2, and --Y, wherein M and Y 
are as defined above; 
R.sup.7 is a monovalent moiety independently selected from the group 
consisting of --CH.sub.2 COOH, --CH.sub.2 CH.sub.2 COOH, --CH.sub.2 
CH.sub.2 N(CH.sub.2 COOH).sub.2, --(CH.sub.2).sub.6 N(CH.sub.2 
COOH).sub.2, --(CH.sub.2 CH.sub.2 O).sub.2 CH.sub.2 CH.sub.2 N(CH.sub.2 
COOH).sub.2, and --CH.sub.2 CH.sub.2 N(CH.sub.2 COOH)CH.sub.2 CH.sub.2 OH. 
Preferably R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are 
independently selected from the group consisting of --H, --OH, --COOM, 
--SO.sub.3 M, --SH, --CH.sub.2 COOM, --SCH.sub.2 COOM, and --Y, wherein M 
and Y are as defined. 
We have now discovered that blends of the nonhalogenated vinyl copolymer 
and the Half-ester Polyurethane unexpectedly provide magnetic coatings 
with a combination of both higher modulus and higher resilience as 
compared to similar blends in which a vinyl chloride copolymer such as 
EC-130.TM. vinyl chloride copolymer is used as the vinyl copolymer. 
Preferably, the Half-ester Polyurethane has a carboxyl equivalent weight in 
the range from 2000 to 30,000. In preferred embodiments, the Half-ester 
Polyurethane may also comprise a plurality of pendant hydroxyl and/or 
radiation curable moieties to facilitate curing of the polymer. If 
hydroxyl and/or radiation curable moieties are present, the Half-ester 
Polyurethane preferably has an equivalent weight based on such moieties in 
the range from 500 to 50,000, more preferably 1000 to 5000. 
The Half-ester Polyurethane can be prepared according to a three-step 
reaction scheme. In the first step, excess polyisocyanate is reacted with 
polyol to form an NCO-capped precursor. The reaction occurs in a suitable 
solvent under anhydrous conditions in the presence of a suitable catalyst 
at a temperature in the range from 60.degree. C. to 80.degree. C. In a 
second step, a 1,4- or 1,5-dicarboxylic acid is added and heating 
continues. During this second step, the dicarboxylic acid rapidly reacts 
with some of the available NCO moieties to form the corresponding cyclic 
anhydride in situ. Preferably, the dicarboxylic acid is a 1,4- or 
1,5-dicarboxylic acid containing at least one additional dispersing group 
other than the two acid groups. Such dicarboxylic acids form cyclic 
anhydrides easily under dehydrating conditions, whereby the resulting 
cyclic anhydride is a five-membered ring or a six-membered ring, 
respectively, having a pendant dispersing group. More preferably, the 
dicarboxylic acid is selected from citric acid, mercaptosuccinic acid, 
dimercaptosuccinic acid, and mixtures thereof. The reaction occurring 
during the second step is exemplified by the following reaction scheme in 
which citric acid is the dicarboxylic acid and R--NCO represents a 
compound with an available NCO moiety: 
##STR3## 
In a third step, heating continues as excess triol is added to the 
reaction mixture. The NCO precursor and the cyclic anhydride then react 
with available hydroxyl groups from the triol, and the resultant product 
is a polyurethane polymer with pendant hydroxyl groups, some or all of 
which may be esterified with the anhydride. The reaction of the anhydride 
with the pendant hydroxyl is exemplified by the following scheme in which 
citric acid anhydride is used: 
##STR4## 
When NCO and anhydride can no longer be detected by infrared analysis, the 
reaction is deemed to be complete. 
Another preferred polyurethane (hereinafter "Graft Polyurethane") is a 
polyurethane comprising a pendant nonhalogenated, copolymeric vinyl 
moiety, wherein the nonhalogenated, copolymeric vinyl moiety bears a 
plurality of nitrile groups. Preferably, the nonhalogenated, copolymeric 
vinyl moiety is a copolymeric moiety of monomers comprising 
(meth)acrylonitrile and optionally one or more of styrene or an alkyl 
ester of (meth)acrylic acid, wherein the alkyl group of the alkyl ester 
has 1 to 20, preferably 1 to 4, carbon atoms. In those embodiments of the 
present invention in which the nonhalogenated, copolymeric vinyl moiety 
comprises an alkyl ester of (meth)acrylic acid, the alkyl ester is 
preferably methyl (meth)acrylate. Graft polyurethanes and their 
preparation have been described in Assignee's copending application U.S. 
Ser. No. 07/852,937, Attorney's Docket No. 45034USA2B, filed Mar. 13, 
1992, which is a continuation of Assignee's application Ser. No. 
07/543,343, Attorney's Docket No. 45034USA1A, filed Jun. 25, 1990, now 
abandoned. The vinyl copolymeric moiety of such polyurethanes greatly 
enhances the compatibility of such polyurethanes with the nonhalogenated 
vinyl copolymer, particularly when the polyurethane also incorporates 
polycaprolactone polyols. 
In addition to the nonhalogenated vinyl copolymer, the secondary polymer 
component if any, and the magnetic pigment, the magnetic layer of the 
present invention may also comprise one or more conventional additives 
such as lubricants; abrasives; crosslinking agents; head cleaning agents; 
thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic 
agents; fungicides; bactericides; surfactants; coating aids; nonmagnetic 
pigments; and the like in accordance with practices known in the art. 
As one example of a process for preparing a magnetic recording medium, the 
components of the magnetic layer are combined and mixed with a suitable 
solvent to form a substantially homogeneous dispersion. The dispersion is 
then coated onto a nonmagnetizable substrate, which may be primed or 
unprimed. The dispersion may be applied to the substrate using any 
conventional coating technique, such as gravure or knife coating 
techniques. The coated substrate may then be passed through a magnetic 
field to orient the magnetic pigment after which the coating is dried, 
calendered if desired, and then allowed to cure. 
Curing can be accomplished in a variety of ways. As one approach, an 
isocyanate crosslinking agent can be added to the dispersion just before 
the dispersion is coated onto the substrate. As soon as the isocyanate 
crosslinking agent is added to the dispersion, the NCO groups of the 
isocyanate crosslinking agent will begin to react with the hydroxyl groups 
of the polymeric binder. Preferably, a catalyst, e.g., dibutyltin 
dilaurate, may also be added in suitable catalytic amounts in order to 
facilitate this crosslinking reaction. Generally, using from 0.02 to 0.2 
parts by weight of catalyst per 100 parts by weight of magnetic pigment 
has been found to be suitable in the practice of the present invention. 
The isocyanate crosslinking agent, if any, is a polyfunctional isocyanate 
having an average functionality of at least 2 isocyanate groups per 
molecule. Examples of specific polyfunctional isocyanate useful as the 
isocyanate crosslinking agent in the practice of the present invention 
include materials commercially available as MONDUR CB-601, CB-75, CB-701, 
MONDUR-MRS from Miles, Inc.; DESMODUR L available Bayer A.G.; CORONATE L 
from Nippon Polyurethane Ind., Ltd.; and PAPI from Union Carbide Corp. 
The isocyanate crosslinking agent is preferably used in an amount such that 
the molar ratio of NCO groups from the isocyanate crosslinking agent to 
the total number of hydroxy groups from the hydroxy functional polymer is 
greater than 0. Preferably, the molar ratio of the NCO groups from the 
isocyanate crosslinking agent to the total number of hydroxy groups from 
the hydroxy functional polymer is in the range from 0.3 to 5, more 
preferably 0.5 to 1.5. 
As another approach, when one or more components of the polymeric binder 
contain radiation curable moieties, the dried coating may be irradiated to 
achieve curing of the radiation curable materials. Irradiation 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, radiation curing is achieved with an amount of 
electron beam radiation in the range from 1 to 20 Mrads, preferably 4 to 
12 Mrads, and more preferably 5 to 9 Mrads of electron beam radiation 
having an energy in the range from 100 to 400 kev, preferably 200 to 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 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 75 parts per 
million. 
The use of radiation curing techniques may offer some advantages over 
isocyanate curing techniques. Whereas isocyanate curing of magnetic media 
is chemically unselective and highly dependent on such variables as 
temperature and humidity, however, radiation curing techniques are less 
sensitive to temperature and humidity. Moreover, radiation curing 
techniques allow one to control, to a certain extent, which polymers 
become crosslinked and which polymers do not become crosslinked. For 
instance, for a polymeric binder containing a polyurethane polymer and a 
nonhalogenated vinyl copolymer wherein only the polyurethane has a pendant 
radiation curable moiety, the `soft` polyurethane may be cured by electron 
beam induced crosslinking of the radiation curable moiety on the 
polyurethane polymer. The `hard` vinyl copolymer, having no radiation 
curable moieties, is not formally cured (Experiments have shown, however, 
that the vinyl copolymer does undergo some crosslinking upon exposure to 
E-beam irradiation, e.g., it is known in the literature that 
styrene-acrylonitrile copolymers undergo crosslinking during E-beam 
exposure.). The rationale for this strategy is that the `hard` resin phase 
(i.e. the vinyl copolymer) already has a high T.sub.g and a high modulus 
without the addition of any chemical crosslinks. Hence, one can 
hypothesize that there is no need to crosslink this `glass-like` phase. 
However, crosslinking (or `cure`) is needed in the `soft` polyurethane 
phase, because crosslinking of the polyurethane results in an increase in 
the molecular weight of this material which gives improved physical 
properties. 
Traditionally, radiation curable formulations have most commonly relied 
upon the reactivity of acrylates, methacrylates, and the like to achieve 
radiation-induced crosslinking. Unfortunately, however, magnetic 
dispersions prepared from such materials tend to undergo unwanted 
crosslinking reactions under ambient conditions to form gels, particularly 
when the magnetic pigment is a metal particle pigment. These dispersions 
are especially prone to suffer from undesirable crosslinking during 
dispersion milling. 
However, because radiation curable polymers having dispersing groups are 
capable of wetting/dispersing the magnetic pigment, it would be desirable 
to include at least some of such polymers in the milling step. In order to 
accomplish this, radiation curable (meth)acrylate groups may be replaced 
by allyloxy groups (--O--CH.sub.2 --CH.dbd.CH.sub.2), or .alpha.-methyl 
styrene moieties of the formula 
##STR5## 
Allyloxy groups and o-methyl styrene moieties are more stable to the 
milling process than (meth)acrylate groups.

The present invention will now be further described with reference to the 
following examples. 
As used throughout the Examples, the following abbreviations are used: 
"AIBN" means 2,2'-azobisisobutyronitrile. 
"AN" means acrylonitrile. 
"HEA" means hydroxyethylacrylate. 
"HEMA" means hydroxyethylmethacrylate. 
"HPA" means hydroxypropylacrylate, 
"IEM" means isocyanatoethyl methacrylate. 
"MA" means methyl acrylate. 
"MAA" means methacrylic acid. 
"MEK" means methyl ethyl ketone. 
"MMA" means methyl methacrylate. 
"MOTAC" means methacryloyloxyethyl trimethyl ammonium chloride. 
"MPD" means mercaptopropane diol. 
"MSA" means mercaptosuccinic acid. 
"PET" means polyethylene terephthalate, 
"S" means styrene. 
"SDS" means sodium dodecylbenzene sulfonate. 
"Meta-TMI" means a compound of the formula 
##STR6## 
EXAMPLE 
Preparation of nonhalogenated vinyl copolymers 
Samples of nonhalogenated vinyl copolymers of the present invention were 
prepared from the following ingredients: 
__________________________________________________________________________ 
Sample No. 
Ingredient 
1A 1B 1C 1D 1E 1F 1G 1H 1I 1J 1K 
__________________________________________________________________________ 
parts by 161.25 
161.88 
157.5 
107.8 
-- 161.25 
161.25 
161.25 
80.6 
-- 161.25 
weight S 
parts by -- -- -- -- 161.25 
-- -- -- 80.6 
211.2 
-- 
weight MMA 
parts by 50.0 
50.0 
50.0 
73.5 
50.0 
50.0 
50.0 
50.0 
50.0 
-- 50.0 
weight AN 
parts by 37.5 
37.5 
37.5 
63.7 
37.5 
-- -- 37.5 
37.5 
37.5 
-- 
weight HPA 
parts by -- -- -- -- -- 37.5 
37.5 
-- -- -- -- 
weight HEA 
parts by 1.25 
0.625 
5.0 4.9 1.25 
1.25 
1.25 
1.25 
1.25 
1.25 
1.25 
weight MOTAC 
parts by -- -- -- -- -- 0.5 1.25 
-- -- -- -- 
weight MSA 
parts by 0.5 0.5 0.5 0.5 0.5 0.5 0.5 -- 0.5 0.5 0.5 
weight MPD 
parts by 375 375 375 375 375 375 375 375 375 375 375 
weight MEK 
parts by 1.25 
1.25 
1.25 
1.25 
1.25 
1.25 
1.25 
1.25 
1.25 
1.35 
1.25 
weight AIBN 
parts by -- -- -- -- -- -- -- -- -- -- 37.5 
weight HEMA 
__________________________________________________________________________ 
For each sample, the ingredients were charged into a 32 oz. amber reaction 
bottle. The resultant admixture, which contained some undissolved 
methacryloyloxyethyl 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. or 70.degree. C. for 80 hours. The product was a 
clear, homogeneous solution containing a nonhalogenated vinyl copolymer of 
the present invention. 
The inherent viscosity of some of the samples in MEK was measured according 
to the procedure described in F. Rodriguez, "Principles of Polymer 
Systems," Chemical Engineering Series, 2nd Edition (McGraw-Hill), pages 
181-185. For some samples, Tg was also measured. The results are shown in 
the following table: 
__________________________________________________________________________ 
Sample No. 
1A 1B 1C 1D 1E 1F 1G 1H 1I 1J 1K 
__________________________________________________________________________ 
Inherent 
.3054 
.3198 
.2955 
.3285 
.2896 
.2661 
.2482 
.3777 
.2914 
.2177 
-- 
Viscosity 
to 
.3313 
Tg 79.degree. C. 
80.degree. C. 
78.degree. C. 
-- -- -- -- -- -- -- 
__________________________________________________________________________ 
EXAMPLE 2 
Preparation of nonhalogenated vinyl copolymers 
Samples of nonhalogenated vinyl copolymers of the present invention were 
prepared from the following ingredients: 
______________________________________ 
Sample No. 
Ingredient 2A 2B 
______________________________________ 
parts by weight S 103.2 103.2 
parts by weight AN 32 32 
parts by weight HPA 24 24 
parts by weight MOTAC 
0.8 0.8 
parts by weight 640 640 
deionized water 
parts by weight SDS 3.2 3.2 
parts by weight carbon 
0.48 0.96 
tetrabromide 
parts by weight 0.36 0.26 
potassium persulfate 
parts by weight sodium 
0.12 0.12 
metabisulfite 
______________________________________ 
For each sample, all the ingredients, except the potassium persulfate and 
the sodium metabisulfite, were placed in a blender cup and purged with 
N.sub.2 at 1 liter per minute for 5 minutes. The contents of the blender 
cup were then homogenized for 1 minute, after which initiator (potassium 
persulfate and sodium metabisulfite) was added. The resultant mixture was 
transferred to a 1-liter 3-neck split flask equipped with a mechanical 
stirrer, nitrogen inlet, and a device to observe exotherm. The solution 
was heated to 35.degree. C. After about 1 hour, the solution exothermed to 
56.degree. C. After the exotherm subsided, the mixture was stirred for 
another 2 hours as it cooled down to room temperature. After this, the 
mixture was drained into a quart jar. Sample 2A showed an inherent 
viscosity in MEK and DMF of 1.7454 and 2.233, respectively. Sample 2B 
showed an inherent viscosity in MEK of 1.1560. 
EXAMPLE 3 
Samples of nonhalogenated vinyl copolymers of the present invention were 
prepared from the following ingredients: 
______________________________________ 
Sample No. 
Ingredient 3A 3B 3C 3D 
______________________________________ 
parts by weight S 
30 30 -- -- 
parts by weight MMA 
-- -- 30 30 
parts by weight AN 
10 12.5 10 12.5 
parts by weight MAA 
5 2.5 5 2.5 
parts by weight HEMA 
5 5 5 5 
parts by weight MEK 
75 75 75 75 
parts by weight AIBN 
0.15 0.15 0.15 0.15 
______________________________________ 
For each sample, the ingredients were charged into an 8 oz. amber reaction 
bottle. The resulting mixture was purged with N.sub.2 for 3 minutes at 1 
liter per minute, after which the bottle was sealed. The sealed bottle 
containing a clear solution was tumbled in a constant temperature bath for 
48 hours at 65.degree. C. The product in each case was a slightly viscous, 
clear solution. 
EXAMPLE 4 
Using the procedure of Example 1, samples of nonhalogenated vinyl 
copolymers of the present invention were prepared from the following 
ingredients: 
__________________________________________________________________________ 
Sample No. 
Ingredient 
4A 4B 4C 4D 4E 4F 4G 
__________________________________________________________________________ 
parts by 108.7 
167.5 
132.5 
-- 147.5 
135.0 
150.0 
weight S 
parts by -- -- -- 160.0 
-- -- -- 
weight MMA 
parts by 75 56.3 
91.25 
51.25 
43.8 
89.4 
103.5 
weight AN 
parts by 65 25 25 37.5 
37.5 
25.0 
45.0 
weight HPA 
parts by 1.25 
1.25 
1.25 
1.25 
1.25 
0.62 
1.5 
weight MOTAC 
parts by 0.5 0.5 0.5 0.5 0.5 0.5 0.6 
weight MPD 
parts by 375 375 375 375 375 375 338 
weight MEK 
parts by 1.25 
1.25 
1.25 
1.25 
1.25 
1.25 
1.8 
weight AIBN 
parts by -- -- -- -- 20.0 
-- -- 
weight MA 
__________________________________________________________________________ 
EXAMPLE 5 
Preparation of polyurethane with mercapto succinic acid wetting groups 
(Sample "5A") 
To a 20 gallon reactor were added 7.5 kg TONE 0210.TM. polycaprolactone 
diol (17.7 eq), 1.9 kg neopentyl glycol (36.7 eq), 10.2 g dibutyltin 
dilaurate, and 27 kg MEK. 8.9 kg diphenylmethane-4,4'-diisocyanate ("MDI") 
(71.2 eq) was then added. The resultant mixture was heated at reflux for 1 
hour, after which 195.8 g mercaptosuccinic acid (1.5 eq) were added. Then, 
6.6 kg TONE.TM. 0305 polycaprolactone triol (36.7 eq), and an additional 9 
kg MEK were added. Heating at reflux continued 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 590 g 
MDI (4.72 eq) was added and the mixture was heated at reflux for an 
additional hour. The mixture showed an inherent viscosity in 
tetrohydrofuran of 0.28 dl/g. The mercaptosuccinic acid equivalent weight 
of the resultant polyurethane was calculated to be 19,600, and the 
hydroxyl equivalent weight was calculated to be 1425. 
EXAMPLE 6 
Preparation of polyurethane with mercaptosuccinic acid wetting groups and 
pendant radiation curable (methacrylate) moieties (Sample "6A") 
27.0 g of isocyanatoethyl methacrylate and a few drops of dibutyltin 
dilaurate were added to 600 g (0.17 mole OH) of a 43.6% solution of 
polyurethane Sample 5A in MEK. The solution was sealed and heated at 
55.degree. C. overnight. The next day, the infrared analysis showed that 
substantially all of the isocyanate had been consumed, and the reaction 
was deemed to be complete. 
EXAMPLE 7 
Preparation of polyurethane with mercaptosuccinic acid wetting groups and 
pendant radiation curable (allyloxy) moieties (Sample "7A") 
To a 2-liter flask were added 214 g TONE 0210.TM. polycaprolactone diol 
available from Union Carbide Corp. (OH eq. weight=425; 0.503 eq), 30.1 g 
neopentyl glycol (0.579 eq), 30 g of 3-allyloxy-1,2-propanediol available 
from Aldrich Chemical Co. (0.454 eq), and 862 g MEK. 75 g MEK were 
distilled off to dry the mixture. 229.4 g diphenylmethane diisocyanate 
(1.835 eq) were then added followed by 0.2 g dibutyltin dilaurate. The 
mixture was heated at reflux for 2 hours, then cooled to 50.degree. C. 4.5 
g mercaptosuccinic acid (0.03 moles) were then added followed by 86.2 g 
TONE 0305.TM. polycaprolactone triol available from Union Carbide 
Corporation (OH eq. weight=180; 0.479 eq) and 129 g MEK. The reaction 
mixture was heated at reflux for 1 hour. An additional 3 g diphenylmethane 
diisocyanate was then added, and the reaction mixture was heated at reflux 
for 2 more hours. The inherent viscosity of the resultant polyurethane 
polymer in tetrohydrofuran was 0.30 dl/g. The polymer was calculated to 
have a hydroxyl equivalent weight of 3000, an allyloxy equivalent weight 
of 2600, and a mercaptosuccinic acid equivalent weight of 20,000. 
EXAMPLE 8 
a. Polyurethane polymers were prepared using the following ingredients in 
the following amounts in accordance with the procedure of Example 5 except 
that (1) when the "other polyol" was used, it was charged to the reactor 
immediately following the neopentyl glycol and (2) for Sample 8E, RUCOFLEX 
S-1019-35.TM. polyester diol was substituted for both the TONE 0210.TM. 
diol and the TONE 0305.TM. triol. 
______________________________________ 
Sample No. 
Ingredient 8A 8B 8C 8D 8E 
______________________________________ 
parts by weight 
179.2 129.0 151.4 428.9 20.7* 
TONE 0210 diol 
parts by weight 
6.3 29.3 36.3 112.5 6.6 
neopentyl glycol 
parts by weight 
-- 150** 75** -- 2.0*** 
other polyol 
parts by weight 
0.1 0.1 0.1 0.1 0.1 
dibutyltin dilaurate 
parts by weight 
393 710 680 1583 90 
MEK 
parts by weight 
76.6 160.5 185.9 515.6 30.5 
MDI 
parts by weight 
2.1 4.5 4.5 -- -- 
mercapto-succinic 
acid 
parts by weight 
16.8 118.49 137.3 380.7 139.3* 
TONE 0305 triol 
parts by weight 
25 178 206 571 209 
additional MEK 
parts by weight 
-- 23.3 19.5 32.4 -- 
additional MDI 
______________________________________ 
The resultant polyruethane polymers had the following characteristics: 
______________________________________ 
Sample No. 
Ingredient 8A 8B 8C 8D 8E 
______________________________________ 
dispersing group 
20,000 20,000 20,000 
-- -- 
equivalent weight 
OH equivalent weight 
5000 2254 1915 1700 10,000 
inherent viscosity 
0.47 0.288 0.292 0.29 0.74 
in tetrohydrofuran 
______________________________________ 
*RUCOFLEX S1019-35 .TM. polyester diol (molecular weight about 3000 used 
in place of TONE 0210 .TM. diol and TONE 0305 .TM. triol). 
**"Other polyol" was HN6 .TM. diol commercially available from Toagosei 
Chemical Industry. This diol is a styrene/acrylonitrile macromonomer diol 
having a molecular weight of about 6000 and a styrene:acrylonitrile ratio 
of about 3:1. 
***"Other polyol" was trimethylolpropane. 
Preparation of polyurethane sample 8F: To a reactor were added 560 g (1.098 
equivalents) "RUCOFLEX S-1014-110" polyester polyol (Ruco Polymer 
Corporation), 191.3 g (3.68 equivalents) neopentyl glycol, 15.4 g (0.345 
equivalents) trimethylol propane, 14 g (0.093 equivalents) 
mercaptosuccinic acid and 2100 g MEK. After stirring to dissolve all 
ingredients, 619 g MDI (4.9 equivalents) were added followed by 0.2 g 
dibutyltin dilaurate. After 3 hours reaction time a product was obtained 
which had an inherent viscosity in tetrahydrofuran of 0.31 g/dl. Its 
hydroxyl equivalent weight is calculated to be 5000 g/eq and its MSA 
equivalent weight is calculated at 15,000 g/eq. 
c. Preparation of polyurethane sample 8G: To 2500 (0.50 mole OH) of a 39.7% 
solution of polyurethane Sample 8B in methyl ethyl ketone was added 76.9 g 
(0.50 mole) of isocyanatoethyl methacrylate (IEM) and a few drops of 
dibutyl tin dilaurate (DBTDL). The solution was sealed in a gallon jar and 
heated at 45.degree. C. until IR analysis showed that the IEM had been 
completely consumed in the reaction (overnight heating is usually 
adequate). The resulting material was used without any further 
purification. 
d. Preparation of polyurethane sample 8H: To a 5-liter flask were added 283 
g TONE 0210.TM. polycaprolactone diol available from Union Carbide Corp. 
(OH eq weight=425; 0.666 eq), 34.4 g of neopentyl glycol (0.662 eq), 325 g 
HN6.TM. diol (0.130 eq) and 1930 g MEK. 380 g of MEK were distilled off to 
dry the mixture. 34.4 g of 3-allyloxy-1,2-propane diol available from 
Aldrich Chemical Co. (0,520 eq) was added followed by 342 g 
diphenylmethane diisocyanate (2,741 eq) and 0.5 g dibutyltin dilaurate. 
The mixture was heated at 80.degree. C. for 2 hours. 9.8 g 
mercaptosuccinic acid (0.07 moles) were then added followed by 253 g TONE 
0305.TM. polycaprolactone triol available from Union Carbide Corporation 
(OH eq. weight=180; 1.406 eq) and 380 g MEK. The reaction mixture was 
heated at reflux for 3 hours. An additional 52 g of diphenylmethane 
diisocyanate was then added, and the reaction mixture was heated at reflux 
for 3 more hours. The inherent viscosity of the resultant polyurethane 
polymer in tetrahydrofuran was 0.32 dl/g. The polymer was calculated to 
have a hydroxyl equivalent weight of s300, and allyloxy equivalent weight 
of 5000, and a mercaptosuccinic acid equivalent weight of 20,000. 
EXAMPLE 9 
Preparation of magnetic dispersions 
a. Three magnetic dispersions were prepared using the following 
ingredients: 
______________________________________ 
Dispersion Sample 
No. 
Ingredient 9A 9B 9C 
______________________________________ 
parts by weight magnetic pigment 
25.0 25.0 25.0 
(SMO III .TM. cobalt-doped Fe.sub.2 O.sub.3) 
parts by weight Carbon black 
1.50 1.50 1.50 
(KETJAN .TM.) 
parts by weight Sample 1A 
9.2 -- -- 
copolymer solution* 
parts by weight Sample 1B 
-- 9.2 -- 
copolymer solution* 
parts by weight Sample 1F 
-- -- 9.2 
copolymer solution* 
parts by weight Sample 5A 
3.9 3.9 3.9 
polyurethane solution** 
parts by weight MEK 43.7 43.7 43.7 
______________________________________ 
*Each of these was a solution of 39% solids in MEK. 
**This was a solution of 40% solids in MEK. 
The ingredients for each sample were combined with 200 g of 1.0-1.3 mm 
yttrium-stabilized ceramic milling media in three 6 oz. quickie mills, 
respectively, and simultaneously milled for 7 hours on a Red Devil.TM. 
paint shaker. 
Each dispersion was evaluated by microscopic examination, at 
200.times.magnification, of a thin smear of the dispersion on a glass 
microscope slide. All three resulting dispersions were smooth and creamy. 
Each dispersion provided a uniform background on the slides, although the 
Sample 9A dispersion prepared from the Sample 1A copolymer provided the 
dispersion with the most workable texture. All three dispersions showed 
only minimal solvent separation, even after being stored for 7 days. 
b. A magnetic dispersion (Sample 9D) was prepared from the following 
ingredients: 
______________________________________ 
Ingredient Parts by Weight 
______________________________________ 
magnetic pigment (SMO III .TM. 
25.0 
cobalt-doped Fe.sub.2 O.sub.3) 
Carbon black (Ketjan .TM.) 
1.50 
Sample 5A polyurethane solution* 
3.25 
Sample 1K copolymer solution** 
9.92 
MEK 39.7 
______________________________________ 
*This solution was 40% solids in MEK. 
**This solution was 36.3% solids in MEK. 
The above ingredients were directly added to a "Quickie Mill". The contents 
of the mill were then manually mixed with a spatula for 1 minute before 
adding 50 ml of 1-1.3 mm yttrium-stabilized ceramic milling media. After 
milling for 6 hours, a glass slide of the resulting dispersion was taken 
and determined to be smooth by microscopic examination at 
400.times.magnification using transmitted light. "Smooth" means that the 
sample showed a uniform texture and color with substantially no opaque, 
agglomerated particles. The dispersion was then drawn from the mill into a 
4 oz. jar. The finished dispersion was monitored over time to monitor 
changes in viscosity and reagglomeration. 
For example, the sample showed an initial high-shear viscosity (10.sup.4 
sec.sup.-2) of 20 cps and a low, low-shear viscosity by visual 
examination. The initial dispersion was also deemed to be smooth based on 
the absence of pigment agglomerates. After 4 days of standing, the sample 
was subjected to 15 sec of high speed mixing before sampling for viscosity 
and smoothness. Both the high and low-shear viscosity and smoothness were 
unchanged compared to the initial results. 
EXAMPLE 10 
Preparation of magnetic recording media 
Five magnetic recording media samples were prepared from the following 
ingredients in the following amounts: 
______________________________________ 
INGREDIENTS IN TS BY 
Sample No. 
WEIGHT 10A 10B 10C 10D 10E 
______________________________________ 
SHO I .TM. cobalt doped 
29.6 29.6 30.3 29.9 30.1 
iron oxide 
dispereant (1:1 Emcol 
2.1 2.1 2.1 2.1 2.1 
Phosphate/phosphorylated 
polyoxyalkyl polyol; See U.S. 
Pat. No. 5,028,483 at col. 5) 
Polyurethane polymer solution 
8.9 10.6 9.1 7.4 5.8 
(30% solids in MEK) 
Sample 1A copolymer solution 
-- 1.9 2.5 3.0 3.6 
(36.2% solids in MEK) 
VAGH .TM. copolymer solution 
2.9 -- -- -- -- 
(31.6% solids in MEK) 
CB-601 .TM. Curing Agent 
2.2 1.7 2.3 2.7 3.2 
solution (60% solids in PM 
acetate) 
Alumina 2.5 2.5 2.6 2.6 2.6 
Lubricant (1:2.2 Myristic 
1.5 1.5 1.5 1.5 1.5 
Acid/Butyl Myristate) 
MEK 21.6 21.6 21.0 21.8 22.1 
Toluene 17.3 17.2 17.6 17.5 17.6 
Cyclohexanone 12.1 12.0 11.8 12.2 12.3 
______________________________________ 
The ingredients for each magnetic recording medium sample were charged into 
five separate Igarashi mills, respectively. The resulting mixtures were 
simultaneously milled for about 6 hours using 0.8 to 1.0 mm Zirconia 
SEPR.TM. beads as the milling media. The mills were cooled using cold 
water jackets during milling. Bulk magnetic properties of the resulting 
dispersions were determined and the results are shown in the following 
table: 
______________________________________ 
Roden- 
Dispersion 
Coercivity 
Square- stock ICI 
Sample No. 
(Oe) ness 45.degree. Gloss 
Value Viscosity 
______________________________________ 
10A 739 0.83 41.8 19.2 16 
10B 723 0.77 47.3 12.4 27 
10C 715 0.74 55.6 9.2 26 
10D 719 0.74 58.1 9.0 29 
10E 713 0.75 44.3 9.1 23 
______________________________________ 
*As used throughout this specification, "Rodenstock value" is a measure o 
smoothness of a coating and was measured using a RODENSTOCK RM400 surface 
finish analyzer commercially available from Rodenstock Co. Generally, a 
higher Rodenstock value corresponds to a smoother surface. 
EXAMPLE 11 
Magnetic dispersions were prepared using the Sample 1D, 1C, 1A, and 4A 
copolymers in combination with the Sample 5A polyurethane. For comparison 
purposes, a magnetic dispersion was also prepared using EC-130.TM. vinyl 
chloride copolymer in combination with the Sample 5A polyurethane. The 
dispersions were prepared from the following ingredients in the following 
amounts: 
__________________________________________________________________________ 
Sample No. 
Ingredient 11A 11B 11C 11D 11E 11F 
__________________________________________________________________________ 
parts by weight 1D 
94.8 
-- -- -- -- -- 
solution 
(40% solids in MEK) 
parts by weight 1C 
-- 97.7 
-- -- -- -- 
solution (39% solids in 
MEK) 
parts by weight 1A 
-- -- 97.7 
-- -- -- 
solution 
(39% solids in MEK) 
parts by weight 4A 
-- -- -- 97.6 
-- -- 
solution 
(39% solids in MEK) 
par by weight EC- 
-- -- -- -- 172 183 
130 .TM. vinyl chloride 
copolymer 
parts by weight 5A 
59.4 
59.4 
59.6 
59.4 
57.7 
60.6 
solution (about 42% 
solids in MEK) 
parts by weight metal 
168 168 168 168 160 168 
particle magnetic 
pigment 
(TODA .TM.) 
parts by weight alumina 
8.42 
8.48 
8.44 
8.39 
8.31 
8.53 
(CERALOX .TM. 0.4x) 
parts by weight MEK 
271 268 273 268 53.6 
18 
parts by weight xylene 
-- -- -- -- 153 -- 
__________________________________________________________________________ 
To prepare each dispersion, the vinyl copolymer solution, the polyurethane 
solution, and the MEK and/or xylene were added to a glass jar and 
thoroughly mixed. Next, the magnetic pigment was added under N.sub.2. 
Next, the jar was removed from the N.sub.2 and the alumina was added. 
Next, the mixture was high shear mixed for several minutes. The mixture 
was then charged to an Igarashi mill containing ceramic media and milled 
for 8-10 hours at 1500 rpm. 
Two coatings were prepared from each dispersion. The first coating was a 
handspread coated onto a PET substrate using a knife coater (2 mils wet 
coating thickness) with an orienting field. Except for Sample 11E, the 
second coating was prepared by first thinning the dispersions with a 
sufficient amount of MEK and xylene to achieve about 25% solids and a 
90/10 MEK/xylene solvent blend. Sample lie was first thinned to obtain 
about 25% solids and a 80/20 MEK/xylene solvent blend. Next, for each 
sample, the dispersion was cast (40 mils wet coating thickness) onto a 
fluorinated ethylene propylene ("FEP") coated surface (a surface that will 
later release the magnetic coating) covering the coating to slow the 
drying rate, and allowing the coatings to dry overnight. The air-dried 
coatings were then removed from the FEP surface and annealed at 45.degree. 
C. for 16 hours. Bulk magnetic and coating properties of the handspreads 
are given below: 
______________________________________ 
Rodenstock E' E' 
Sample 
Binder Value Squareness 
20.degree. C. 
80.degree. C. 
______________________________________ 
11A 1D/5A 8.4 0.73 3.6 2.1 
11B 1C/5A 9.3 0.73 4.1 2.8 
11C 1A/5A 9.9 0.76 4.0 2.4 
11D 4A/5A 8.1 0.75 4.0 2.3 
11E EC130/5A 8.6 0.71 2.9 1.1 
11F EC130/5A 8.3 0.74 -- -- 
______________________________________ 
*Throughout this specification, the storage moduli (E') in GPa were 
determined with a Dupont 982 Dynamic Mechanical Analysis instrument. 
The coatings prepared with the vinyl copolymer were tougher and much more 
flexible than would be expected considering the Tg's of the polymers used 
to prepare the coatings. The coatings also had moduli which are 
significantly higher than analogous coatings prepared with EC-130.TM. 
vinyl chloride copolymer. Further, the high temperature phase transition 
of Samples 11A, 11B, 11C, and 11D occurred at a significantly higher 
temperature than it did for Samples 11E and 11F. 
EXAMPLE 12 
The procedure used to prepare the Sample 11C (1A/5A binder) dispersion was 
used to prepare another magnetic dispersion (Sample 12A) using 97.9 g of 
1A copolymer solution (39.2% solids in MEK), 62.9 g of 8D polyurethane 
solution (39.2% solids in MEK), 267 g MEK, 168 g Toda.TM. metal particle 
magnetic pigment, and 8.40 g Ceralox alumina. Sample 12A differs from 
Sample 11C in that the Sample 8D polyurethane was substituted for the 
Sample 5A polyurethane. The 8D polyurethane is substantially identical to 
the Sample 5A polyurethane except that the 8D polyurethane does not 
contain any MSA wetting groups. A handspread and coating was prepared 
using the same procedures used in preparing the handspread and coating 
from Sample 11C. The bulk magnetic and coating properties of the resultant 
handspread are compared to the results for Sample 11C: 
______________________________________ 
Rodenstock E' E' 
Sample 
Binder Value Squareness 
20.degree. C. 
80.degree. C. 
______________________________________ 
11C 1A/5A 9.9 0.76 4.0 2.4 
12A 1A/8D 7.2 0.73 severely 
cracked 
______________________________________ 
Whereas Sample 11C gave a tough, high modulus coating, Sample 12A resulted 
in a severely cracked coating. This demonstrates the influence of the 
polyurethane on the mechanical properties of the magnetic coating. 
EXAMPLE 13 
The procedure used to prepare Sample 11C (1A/5A binder) dispersion was used 
to prepare another magnetic dispersion (Sample 13A) using 97.5 g of Sample 
4D copolymer solution (39.5% solids in MEK), 60.4 g of Sample 5A 
polyurethane solution (42.5% solids in MEK), 267 g MEK, 168 g TODA.TM. 
metal particle magnetic pigment, and 8.47 g Ceralox alumina. Sample 13A 
differs from Sample 11C in that Sample 4D copolymer was substituted for 
the 1A copolymer. The sample 4D copolymer is identical to the Sample 1A 
copolymer, except that the Sample 4D copolymer was prepared using methyl 
methacrylate in place of styrene. A handspread and coating was prepared 
using the same procedures used in preparing the handspread and coating 
from Sample 11C. The bulk magnetic and coating properties of the resultant 
handspread are compared to the results for Sample 11C: 
______________________________________ 
Rodenstock E' E' 
Sample 
Binder Value Squareness 
20.degree. C. 
80.degree. C. 
______________________________________ 
11C 1A/5A 9.9 0.76 4.0 2.4 
13A 4D/5A 6.9 0.73 3.5 1.7 
______________________________________ 
Sample 13A had a slightly lower moduli than Sample 11C. 
EXAMPLE 14 
The procedure used to prepare Sample 11C (1A/5A binder) dispersion was used 
to prepare another magnetic dispersion (Sample 14A) using 97.8 g of Sample 
4E copolymer solution (39.2% solids in MEK), 60.2 g of Sample 5A 
polyurethane solution (42.5% solids in MEK), 269 g MEK, 168 g Toda.TM. 
metal particle magnetic pigment and 8.40 g Ceralox alumina. Sample 14A 
differs from Sample 11C in that the 4E copolymer was substituted for the 
1A copolymer. The sample 4E copolymer is identical to the Sample 1A 
copolymer, except that some of the styrene and acrylonitrile used to 
prepare the 1A copolymer was replaced with methyl acrylate (MA). A 
handspread and coating was prepared using the same procedures used in 
preparing the handspread and coating from Sample 11C. The bulk magnetic 
and coating properties of the resultant handspread are compared to the 
results for Sample 11C: 
______________________________________ 
Rodenstock E' E' 
Sample 
Binder Value Squareness 
20.degree. C. 
80.degree. C. 
______________________________________ 
11C 1A/5A 9.9 0.76 4.0 2.4 
14A 4E/5A 6.8 0.75 4.1 2.3 
______________________________________ 
Although its surface was rougher, Sample 14A showed tensile and magnetic 
properties which were much like those of Sample 11C. 
EXAMPLE 15 
The procedure used to prepare Sample 11D (4A/5A binder) dispersion was used 
to prepare three magnetic dispersions: 
Sample 15A: 97.4 g of Sample 4A copolymer solution (39.1% solids in MEK), 
87.3 g of Sample 8E polyurethane solution (29.2% solids in MEK), 239 g 
MEK, 168 g DOWA.TM. metal particle magnetic pigment, and 8.49 g CERALOX 
alumina. 
Sample 15B: 97.7 g of Sample 4A copolymer solution (39.1% solids in MEK), 
73.4 g of Sample 8A polyurethane solution (29.2% solids in MEK), 253 g 
MEK, 168 g DOWA.TM. metal particle magnetic pigment, and 8.41 g CERALOX 
alumina. 
Sample 15C: 97.6 g of Sample 4A copolymer solution (39.1% solids in MEK), 
60.6 g of Sample 8F polyurethane solution (42.1% solids in MEK), 266 g 
MEK, 168 g DOWA.TM. metal particle magnetic pigment, and 8.40 g CERALOX 
alumina. 
A handspread and coating was prepared from Samples 15A, 15B, and 15C using 
the same procedures used in preparing the handspread and coating from 
Sample 11D. The bulk magnetic and coating properties of the resultant 
handspreads are compared below: 
______________________________________ 
Rodenstock E' E' 
Sample 
Binder Value Squareness 
20.degree. C. 
80.degree. C. 
______________________________________ 
15A 4A/8E 29 0.70 heavily 
cracked 
15B 4A/8A 9.5 0.72 3.1 1.5 
15C 4A/8F 6.5 0.72 3.3 2.4 
______________________________________ 
The very high Rodenstock value of the Sample 15A dispersion illustrates the 
influence of the polyurethane's wetting group on the quality of the 
dispersions. The coating from Sample 15A was heavily cracked, whereas the 
coatings from 15B and 15C were relatively crack-free. The 15B coating was 
amazingly flexible. It was so resilient it could be folded like a piece of 
paper. The 15C coating was considerably less resilient than 15B, but still 
somewhat flexible. The extreme resilience of 15B comes with the price of a 
lower high temperature modulus. The mechanical properties of the coatings 
can obviously be tailored by varying the properties of the polyurethane. 
EXAMPLE 16 
The procedure used to prepare Sample 11D (4A/5A binder) dispersion was used 
to prepare four magnetic dispersions: 
Sample 16A: 93.9 g of Sample 4G copolymer solution (40.7% solids in MEK), 
59.9 g of Sample 5A polyurethane solution (42.5% solids in MEK), 271 g 
MEK, 168 g DOWA.TM. metal particle magnetic pigment, and 8.42 g CERALOX 
alumina. 
Sample 16B: 93.8 g of Sample 4G copolymer solution (40.7% solids in MEK), 
63.8 g of Sample 8B polyurethane solution (40.0% solids in MEK, 267 g MEK, 
168 g DOWA.TM. metal particle magnetic pigment, and 8.39 g CERALOX 
alumina. 
Sample 16C: 97.8 g of Sample 4A copolymer solution (39.1% solids in MEK), 
64.0 g of Sample 8B polyurethane solution (40.0% solids in MEK), 263 g 
MEK, 168 g DOWA.TM. metal particle magnetic pigment, and 8.40 g CERALOX 
alumina. 
Sample 16D: 97.9 g of Sample 4B copolymer solution (39.0% solids in MEK), 
63.9 g of Sample 8B polyurethane solution (40.0% solids in MEK), 263 g 
MEK, 168 g DOWA.TM. metal particle magnetic pigment, and 8.40 g CERALOX 
alumina. 
A handspread coating was prepared from Samples 16A, 16B, 16C, and 16D using 
the same procedures used in preparing the handspread and coating from 
Sample 11D. The bulk magnetic and coating properties of the resultant 
handspread are compared below: 
______________________________________ 
Rodenstock E' E' 
Sample 
Binder Value Squareness 
20.degree. C. 
80.degree. C. 
______________________________________ 
16A 4G/5A 5.4 0.71 4.1 2.7 
16B 4G/8B 5.5 0.73 4.5 3.2 
16C 4A/8B 6.5 0.69 3.4 2.1 
16D 4B/8B 5.6 0.70 too too 
brittle 
brittle 
______________________________________ 
Replacing Sample 5A with Sample 8B produced a higher modulus coating, 
illustrating the influence of the polyurethane on the coating's mechanical 
properties. Sample 4G combined with Sample 8B produced a much higher 
modulus than when Sample 4A was combined with Sample 8B. Also, Sample 4B 
combined with Sample 8B produced a much more brittle coating than when 
Sample 4G or Sample 4A was combined with Sample 8B. These results 
illustrate how the mechanical properties of the coating can be tailored by 
altering the type of copolymer and/or polyurethane. 
EXAMPLE 17 
4.64 lbs MEK, 4.65 lbs of Sample 4B copolymer solution (39% in MEK), and 
3.02 lbs of Sample 5A polyurethane solution (40% in MEK) were added to an 
enclosed, water-cooled, high shear mixing kettle. The mixture was mixed 
for 15 minutes while cooling and purging with N.sub.2 at a rate of 20-30 
CFH. When the O.sub.2 level reached 1.5%, the N.sub.2 flow was reduced to 
the minimum level required to maintain an P.sub.2 level of 1.0% 
Next, 11.02 lbs. of DOWA.TM. metal particle magnetic pigment was added. 
Mixing continued for one hour. Then 0.55 lbs of CERALOX 0.4 alumina was 
added and mixing was continued for two hours. The N.sub.2 purging and 
water cooling was then discontinued and the contents of the kettle were 
transferred to a five gallon pail. 12.60 lbs of MEK were added to the 
mixture and it was mixed under a high shear mixer for an additional hour. 
Next, the mixture was thinned with a sufficient amount of MEK and xylene to 
attain a dispersion at 30% solids at 90/10 MEK/xylene. This mixture was 
then charged to a Netzsch 4-liter horizontal sandmill containing 0.8-1.0 
mm ceramic media. The mixture was milled until smooth using pass to pass 
milling with a shaft speed of approximately 1850 RPM and a flow rate of 
approximately 0.05 GPM. After milling, the dispersion was filtered through 
a Nippon Roki HT50 filter (8 micron rating) followed by a Nippon Roki HT30 
filter (3.5 micron rating). 
A carbon black containing backside dispersion was coated onto a 56 gauge 
PET substrate and dried at 140.degree. F. Next, the other side of this 
substrate was coated with the above magnetic dispersion. Immediately prior 
to coating, 299 g of a 2:1 myristic acid:butyl stearate solution (15.7% 
solids. in MEK) and 135 g of CB-701.TM. (70% solids in THF) were added to 
31.2 lbs of this dispersion, and the dispersion was high shear mixed for 
approximately ten minutes. A reverse gravure coating method was used and 
the media was coated at 200 fpm. Three magnets were used to orient the 
metal particles. The first magnet (2000 G) was placed immediately after 
the coating head, the second magnet (4500 G) was placed approximately 8 
feet downline, and the last magnet (3400 G) was placed approximately 8 
feet downline from the second magnet. Two ovens were used to dry the 
magnetic coating, the first at 140.degree. F., and the second at 
180.degree. F. The media was then calendered at 110.degree. F. and 1200 
PLI. 
The resultant magnetic media had a squareness of 0.77, a coercivity of 1583 
Oe, a remanence of 1899 Ga, as measured with a vibrating sample 
magnetometer (10 kGa), and an average RMS surface roughness of 5.8 nm (as 
measured by a Wyko high resolution interferometer.) 
EXAMPLE 18 
6.10 lbs MEK, 0.44 lbs RHODAFAC BG-510.TM. solution (50% solids in MEK, 
Rhone-Poulenc Co.), 3.60 lbs of Sample 4G copolymer solution (41% in MEK), 
and 2.46 lbs of Sample 8B polyurethane solution (40% in MEK) were added to 
an enclosed, water-cooled, high shear mixing kettle. The mixture was mixed 
for 15 minutes while cooling and purging with N.sub.2 at a rate of 20-30 
CFH. When the O.sub.2 level reached 1.0%, the N.sub.2 flow was reduced to 
the minimum level required to maintain an O.sub.2 level of 1.0% 
Next, 11.02 lbs of DOWA.TM. metal particle magnetic pigment was added. 
Mixing was continued for two hours. Then, 0.55 lbs of CERALOX 0.4 alumina 
was added and mixing was continued for one hour. The N.sub.2 purging and 
water cooling was then discontinued and the contents of the kettle were 
transferred to a five gallon pail. 11.46 lbs of MEK were added to the 
mixture and it was mixed under a high shear mixer for one hour. 
Next, the mixture was thinned with a sufficient amount of MEK and xylene to 
attain a dispersion at 35% solids at 90/10 MEK/xylene. This mixture was 
then charged to a Netzsch 4-liter horizontal sandmill containing 0.8-1.0 
mm ceramic media. The mixture was milled until smooth using pass to pass 
milling with a shaft speed of approximately 1850 RPM and a flow rate of 
approximately 0.05 GPM. After milling, the dispersion was thinned to 26% 
solids with 90/10 MEK/xylene, filtered through a Nippon Roki HT50 filter 
(8 micron rating) followed by a Nippon Roki HT30 filter (3.5 micron 
rating). 
A carbon black containing backside dispersion was coated onto a 60 gauge 
PET substrate and dried at 140.degree. F. Next, the other side of this 
substrate was coated with the above magnetic dispersion. Immediately prior 
to coating, 321 g of a 2:1 myristic acid:butyl stearate solution (15.7% 
solids in MEK) and 59.7 g of CB-701.TM. cross-linking agent (70% solids in 
THF) were added to 18.7 lbs of this dispersion and the dispersion was high 
shear mixed for approximately ten minutes. A reverse gravure coating 
method was used and the media was coated at 200 fpm. Two magnets were used 
to orient the metal particles. The first magnet (3100 G) was placed 
immediately after the coating head and the second magnet (4500 G) was 
placed approximately 8 feet downline. Two ovens were used to dry the 
magnetic coating, the first at 140.degree. F. and the second at 
180.degree. F. The media was then calendered at 110.degree. F. and 1600 
PLI. 
The resultant magnetic media had a squareness of 0.69, a coercivity of 1519 
Oe, a remanence of 1699 Ga, as measured with a vibrating sample 
magnetometer (10 kGa), and an average RMS surface roughness of 8.2 nm (as 
measured by a Wyko high resolution interferometer). 
EXAMPLE 19 
All of the weights given in this Example are based on 11.02 lbs (5.00 kg) 
of metal particle pigment being present in the coating formulation. In 
practice, however, some dispersion may be lost during the various 
processing steps. If this happens, the weights of the ingredients given in 
this example must be adjusted in practice to account for the amount of 
lost metal particle pigment. 
This Example describes the use of radiation to selectively `cure` the soft 
polyurethane phase of a magnetic coating. The procedure described in this 
Example can be used to prepare magnetic coatings which have high modulus 
and high resilience. Both of these properties are important to the 
durability and runnability of magnetic media. 
6 g of propyl gallate, 6 g of Irgafos 168.TM., and 6.13 lbs (2.39 kg) of a 
39% solution of Sample 1A copolymer in methyl ethyl ketone were 
sequentially added to 5.3 lbs (2.4 kg) of methyl ethyl ketone. The 
resulting solution was mixed in an enclosed high shear mixer for 10 
minutes. The mixing apparatus was then purged with N.sub.2 gas. 
Next, while maintaining the N.sub.2 atmosphere, 11.0 lbs (5.0 kg) of Fe 
metal particle magnetic pigment (DOWA.TM.) followed by 0.55 lbs (250 g) of 
Ceralox 0.4x.TM. alumina were slowly added sequentially to the solution. 
The mixture was then mixed under the N.sub.2 atmosphere in the high shear 
mixer for an additional 2 hours. 
Next, 11.9 lbs (5.4 kg) of methyl ethyl ketone was added to the mixture. 
The mixture was then mixed with the high shear mixer for an additional 1 
hour. The dispersion was thinned down to 37% solids by addition of 2.80 
lbs (1.27 kg) of MEK. After this, the mixture was milled pass to pass in a 
sandmill until smooth using ceramic media. 
The magnetic dispersion was then coated onto one pre-primed side of a thin 
gauge, polyester terephthalate substrate bearing a carbon-black containing 
backside coating on its other side. Just prior to coating the magnetic 
dispersion onto the substrate, 2.29 lb (1.04 kg) of a 44.5% solution of 
Sample 6A polyurethane in methyl ethyl ketone was added to the dispersion. 
Then, 50 g butyl stearate was blended into the dispersion. Finally, 3.81 
lbs (1.73 kg) of MEK and 3.20 lbs (1.45 kg) of xylene were added to the 
dispersion. After coating the magnetic dispersion onto the substrate, the 
coated substrate was then immediately passed through three magnetic fields 
(2000, 4000 and 3400 gauss) to orient the magnetic pigment. The coated 
substrate was again dried at 140.degree. F., and then the magnetic and 
backside coating were calendered. The coated substrate was then irradiated 
with 4 megarads of electron beam radiation in a N.sub.2 atmosphere 
containing no more than 50 ppm O.sub.2. 
The resulting magnetic medium showed a squareness of 0.716 and a coercivity 
of 1549 and a remanence of 1683 gauss. All bulk magnetic measurements were 
made with a vibrating sample magnetometer ("VSM") at 12.3 KOe. 
EXAMPLE 20 
All of the weights given in this Example are based on 11.02 lbs (5.00 kg) 
of metal particle pigment being present in the coating formulation. In 
practice, however, some dispersion may be lost during the various 
processing steps. If this happens, the weights of the ingredients given in 
this example must be adjusted in practice to account for the amount of 
lost metal particle pigment. 
This example describes the use of a self-wetting polyurethane which has 
pendant allyloxy moieties to provide a polyurethane with radiation curing 
capabilities. 
To carry out this Example, 6 g of propyl gallate, 6 g of IRGAFOS 168.TM., 
5.19 lbs (2.35 kg) of 39% solution of Sample 1A copolymer in MEK, and 1.71 
lbs (0.80 kg) of 39.7% solution of Sample 7A polyurethane in MEK were 
sequentially added to 5.4 lbs of methylethyl ketone. The resulting 
solution was mixed in an enclosed high shear mixer for 10 minutes. The 
mixing apparatus was then purged with N.sub.2 gas. 
Next, while maintaining the N.sub.2 atmosphere, 11.0 lbs (5.0 kg) of Fe 
metal particle (DOWA.TM.) was added followed by 0.55 lbs (0.25 kg) of 
alumina (CERALOX 0.4X.TM.). The mixture was then mixed under the N.sub.2 
atmosphere in a high shear mixer for an additional 2 hours. 
Next, 11.95 lbs (5.42 kg) of methylethyl ketone was added to the mixture. 
The mixture was then mixed with a high shear mixer for an additional hour. 
The dispersion was thinned down to 39% solids by addition of 0.58 lbs 
(0.26 kg) of MEK. After this, the mixture was milled pass to pass in a 
sandmill until smooth using ceramic media. 
The magnetic dispersion was coated onto one side of a thin gauge, 
pre-primed polyester terephthalate substrate bearing a carbon 
black-containing backside coating on its other side. Just prior to coating 
the magnetic dispersion onto the substrate, 1.52 lbs (0.69 kg) of 44.7% 
solution of Sample 6A polyurethane in MEK was added followed by 0.11 lbs 
(50 g) of butyl stearate. Then, 6.49 lbs (3.15 kg) of methylethyl ketone 
and 3.21 lbs (1.46 kg) of xylene were added to the dispersion. 
After coating the magnetic dispersion onto the substrate, the coated 
substrate was then passed through 3 magnetic fields (2000, 4000, and 3400 
Gauss) to orient the magnetic pigment. After orientation, the coated 
substrate was again dried in two subsequent ovens at 140.degree. F. and 
180.degree. F. The magnetic and backside coatings were calendered followed 
by irradiation with electron beam radiation (8 megarads) in a N.sub.2 
atmosphere containing no more than 50 ppm O.sub.2. 
The resulting magnetic media showed a squareness of 0.717 and a coercivity 
of 1554 and a remanence of 1745 gauss. All bulk magnetic measurements were 
made with a vibrating sample magnetometer ("VSM") at 12.3 KOe. 
EXAMPLE 21 
All of the weights given in this Example are based on 11.02 lbs (5.00 kg) 
of metal particle pigment being present in the coating formulation. In 
practice, however, some dispersion may be lost during the various 
processing steps. If this happens, the weights of the ingredients given in 
this example must be adjusted in practice to account for the amount of 
lost metal particle pigment. 
6 g of propyl gallate, 6 g of IRGAFOS 168.TM., 0.44 lbs (0.20 kg) of 50% 
RHODAFAC BG-510 (Rhone-Poulenc Co.) in MEK, 3.41 lbs (1.55 kg) of 41% 
solution of Sample 4G copolymer in MEK, 1.13 lbs (0.51 kg) of 41.2% 
solution of Sample 8H polyurethane in MEK were sequentially added to 6.22 
lbs of methyl ethyl ketone. The resulting solution was mixed in an 
enclosed high shear mixer for 10 minutes. The mixing apparatus was then 
purged with N.sub.2 gas. 
Next, 11.02 lbs (5.0 kg) of Fe metal particle (TODA.sup.TM) followed by 
0.55 lbs (0.25 kg) of alumina (Ceralox 0.4x) were added sequentially to 
the dispersion. The dispersion was mixed under an N.sub.2 atmosphere in 
the high shear mixer for an additional 2 hours. 
Next, 9.36 lbs (4.24 kg) of methyl ethyl ketone and 2.05 lbs (0.93 kg) of 
xylene were added to the mixture. The mixture was then mixed with a high 
shear mixer for two hours. After mixing, the dispersion was thinned down 
to 35% solids by adding 4.88 lbs (2.21 kg) of methyl ethyl ketone. The 
mixture was then milled pass to pass in a sandmill until smooth using 
ceramic media. After milling, the dispersion was filtered through a Nippon 
Roki HT50 filter followed by a Nippon Roki HT30 filter. 
The magnetic dispersion was then coated onto one side of a polyester 
substrate bearing a carbon-black containing coating on its other side. 
Just prior to coating the magnetic dispersion onto the substrate, 1.13 lbs 
(0.51 kg) of 41.2% solution of Sample 8G polyurethane in MEK was added to 
the dispersion, followed by addition of a solution of 0.11 lbs (0.05 kg) 
butyl stearate and 0.22 lbs (0.10 kg) myristic acid in 1.68 lbs (0.764 kg) 
methyl ethyl ketone. After coating the magnetic dispersion onto the 
substrate, the coated substrate was then passed through 2 magnetic fields 
(1200 and 4600 gauss) to orient the magnetic pigment. The coated substrate 
was then dried in two subsequent ovens at 140.degree. .F and 180.degree. 
F., and the magnetic and backside coatings were then calendered. The 
coated substrate was then irradiated with 6.6 megarads of electron beam 
radiation in a N.sub.2 atmosphere containing no more than 50 ppm O.sub.2. 
The resulting magnetic media showed a squareness of 0.731 and a coercivity 
of 1503 Oe and a remanence of 2601 gauss. All bulk magnetic measurements 
were made with a vibrating sample magnetometer ("VSM") at 12.3 KOe. 
EXAMPLE 22 
Magnetic recording media samples were prepared from the following 
ingredients in the following amounts: 
______________________________________ 
INGREDIENTS IN Sample No. 
TS BY WEIGHT 22A 22B 22C 22D 
______________________________________ 
CHARGE I: 
MEK 25.8 25.8 27.9 27.9 
Toluene 13.6 13.8 12.1 12.3 
phosphorylated polyoxyalkyl 
0.8 -- 0.8 -- 
polyol solution (75% in 
Toluene) (See U.S. Pat. No. 
5,028,483 at col. 5) 
EMCOL Phosphate -- 0.6 -- 0.6 
BASF .TM. Chromium dioxide 
28.7 28.7 28.8 28.8 
Sample 1A copolymer solution 
4.5 4.5 5.6 5.6 
(39.0% in MEK) 
first polymer solution 
3.2 3.2 -- -- 
(40% in MEK) 
second polymer solution 
-- -- 2.6 2.6 
(41.6% in MEK) 
CHARGE II: 
first polymer solution 
3.2 3.2 -- -- 
(40% in MEK) 
second polymer solution 
-- -- 2.6 2.6 
(41.6% in MEK) 
Myristic Acid 0.4 0.4 0.4 0.4 
Butyl Stearate 0.6 0.6 0.6 0.6 
MEK 11.6 11.6 9.2 9.2 
Toluene 4.9 4.9 6.7 6.7 
CB-601 .TM. cross-linking agent 
2.7 2.7 2.7 2.7 
(60% in PM Acetate) 
______________________________________ 
In this table, the second polyurethane was prepared in accordance with 
Example 1 of U.S. Pat. No. 5,081,213. The first polyurethane was prepared 
as follows. To a 75 gallon kettle were added 108 kg methyl ethyl ketone, 
4.0 kg (0.077 equivalents) neopentyl glycol, 0.45 kg (0,008 equivalents) 
N-methyl diethanolamine, 0.002 kg phosphoric acid, 2,9 kg (0.064 
equivalents) trimethylol propane, 37.5 kg (0.090 equivalents) DURACARB 124 
(polycarbonate polyol, PPG Industries). After mixing for 15 minutes, 20.5 
kg (0.164 equivalents) diphenylmethane diisocyanate and 0.004 kg 
dibutyltin dilaurate were added. The reaction was heated at 60.degree. C. 
for one hour. 1 kg of additional diphenylmethane diisocyanate was added 
and the reaction was continued at 60.degree. C. for an hour. The final 
inherent viscosity in tetrahydrofuran was 0.3. The calculated equivalent 
weights were: 1400 hydroxyl, and 20,000 amino. 
To prepare each media sample, the ingredients of the first charge were 
added in the order listed into an enclosed Shar.TM. mixer (fitted with a 
water jacket for cooling) and slowly mixed for 2 hours. Next, the contents 
of the mixer were milled pass to pass until smooth in a horizontal 
sandmill using 0.8 to 1.0 mm ceramic media. Except for the crosslinking 
agent, the ingredients of the second charge were then slowly added in the 
order listed. Milling then continued until a smooth, homogeneous 
dispersion was obtained, typically 6-8 passes. The mill was cooled using a 
cold water jacket during milling. The resulting dispersion was filtered, 
and the crosslinking was added to the dispersion with mixing using the 
Shar.TM. mixer. The dispersion was then coated onto a polyethylene 
terephthalate film. The magnetic pigment was oriented in a magnetic film 
during coating. The coated film was dried and calendered. 
Electromagnetic properties of the samples were determined, and the results 
are shown in the following table: 
______________________________________ 
Sample No. 
Property 22A 22B 22C 22D 
______________________________________ 
Coercivity, H.sub.c in 
749 761 756 757 
oersted, Oe 
Squareness 0.8 0.84 0.81 0.84 
Remanence, B.sub.r in 
1349 1506 1408 1411 
gauss 
Roughness, in nm 
10.4 11.9 11.1 10.7 
Modulus, GPa @ 
7.042 10.54 9.342 14.07 
20.degree. F. 
Video Noise, db 
2.4 1.7 1.6 1.9 
Audio Noise, db 
0.2 0.1 -0.4 0.2 
Rf Output, db 
1.1 1.1 0.5 0.8 
Color Output, db 
-0.8 -0.4 -1.0 -0.8 
______________________________________ 
EXAMPLE 23 
a. Preparation of quaternary ammonium functional isocyanate: 
198 g isophorone diisocyanate and 85.5 g dimethyl ethanolamine were stirred 
into 160 g MEK contained in a flask equipped with a water-cooled 
condenser. In about 15 minutes, the temperature shot up to about 
70.degree. C. and stayed there for about one hour. The solution was 
allowed to react completely overnight. Next, a solution of 114 g methyl 
sulfate in 54 g MEK was slowly added with stirring and cooling, if 
necessary, to maintain the temperature below 60.degree. C. After all the 
methyl sulfate was added, the solution was allowed to stand overnight. 
b. Preparation of styrene/acrylonitrile/hydroxyethyl methacrylate 
copolymer. 
55 parts by weight styrene, 19 parts by weight acrylonitrile, and 26 parts 
by weight hydroxyethyl methacrylate were free radically polymerized in the 
presence of 1% mercaptopropanediol, 0.3 g VAZO-64.TM. initiator, and 
sufficient MEK to provide a copolymer solution of 39.9% solids. 
c. Functionalization of vinyl copolymer with quaternary ammonium and 
radiation curable moieties: 
The following amounts of the quaternary ammonium functional isocyanate, 
meta-TMI, and dibutytindilaurate were added to portions of the vinyl 
copolymer prepared in part (b): 
______________________________________ 
Sample No. 
Ingredient 23A 23B 23C 23D 
______________________________________ 
copolymer solution 
300 g 300 g 300 g 300 g 
(39.9% solids)* 
quaternary ammonium 
0 2.2 g 4.4 g 6.6 g 
functional isocyanate 
solution (65% solids)* 
meta-TMI 19.2 19.2 19.2 19.2 
dibutyltin dilaurate 
6 6 6 6 
drops drops drops drops 
______________________________________ 
*The solvent for each of these solutions was MEK. 
d. Preparation of dispersions: 
Each of Samples 23A, 23B, 23C and 23D were used to prepare dispersions 
containing 22 g of each sample diluted with MEK to 45% solids, 40 g SMO 
III.TM. magnetic pigment, and 50 g MEK. The ingredients were milled in a 
Quickie mill for 4 hours using steel media. 
EXAMPLE 24 
44 parts by weight styrene, 30 parts by weight acrylonitrile, and 26 parts 
by weight hydroxyethyl methacrylate were free radically polymerized in the 
presence of 0.3% mercaptopropane diol and sufficient MEK to provide a 
copolymer solution of 40.5% solids. 600 g of this solution were then 
reacted with 0.5 g dibutyltindilaurate, 12.5 g of a 65% solids solution of 
the quaternary ammonium functional isocyanate of Example 24 in MEK, and 13 
g MEK. reaction was complete in about 24 hours. 
Other embodiments of this invention will be apparent to those skilled in 
the art from a consideration of this specification or from practice of the 
invention disclosed herein. Various omissions, modifications, and changes 
to the principles described herein may be made by one skilled in the art 
without departing from the true scope and spirit of the invention which is 
indicated by the following claims.