U.S. patent application number 11/268491 was filed with the patent office on 2006-06-01 for electron beam curable urethane resin for magnetic recording medium, method of manufacturing the same and magnetic recording medium using the same.
This patent application is currently assigned to TDK CORPORATION. Invention is credited to Kenichi Kitamura, Hideki Sasaki, Kazushi Tanaka, Hiroyuki Yamada.
Application Number | 20060115687 11/268491 |
Document ID | / |
Family ID | 31700030 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060115687 |
Kind Code |
A1 |
Sasaki; Hideki ; et
al. |
June 1, 2006 |
Electron beam curable urethane resin for magnetic recording medium,
method of manufacturing the same and magnetic recording medium
using the same
Abstract
An electron-beam curable polyurethane resin for magnetic
recording media is produced by modifying a polyurethane resin
having active hydrogen in the molecule thereof with a compound
having at least two acrylic double bonds, wherein the modification
is performed on the active hydrogen so that the polyurethane resin
becomes electron-beam curable. By subjecting a known thermosetting
polyurethane resin to electron-beam sensitive modification, the
resulting resin is highly crosslinked and is thus capable of being
suitably used for magnetic recording media. Also, an electron-beam
curable polyurethane resin having excellent crosslinking
characteristics can easily be produced from the known thermosetting
polyurethane resin. Furthermore, by using the electron-beam curable
polyurethane resin, a high-performance magnetic recording medium
can be provided.
Inventors: |
Sasaki; Hideki; (Tokyo,
JP) ; Yamada; Hiroyuki; (Tokyo, JP) ;
Kitamura; Kenichi; (Tokyo, JP) ; Tanaka; Kazushi;
(Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TDK CORPORATION
Tokyo
JP
|
Family ID: |
31700030 |
Appl. No.: |
11/268491 |
Filed: |
November 8, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10397169 |
Mar 27, 2003 |
7026371 |
|
|
11268491 |
Nov 8, 2005 |
|
|
|
Current U.S.
Class: |
428/844.71 |
Current CPC
Class: |
Y10T 428/31551 20150401;
Y10S 428/90 20130101; C08G 18/8175 20130101; C09D 175/16
20130101 |
Class at
Publication: |
428/844.71 |
International
Class: |
G11B 5/706 20060101
G11B005/706 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2002 |
JP |
2002-097601 |
Claims
1-20. (canceled)
21. An electron-beam curable polyurethane resin for a magnetic
recording medium comprising an isocyanurate having two acrylic
double bonds.
22. The electron-beam curable polyurethane resin for a magnetic
recording medium of claim 21, wherein the isocyanurate is delivered
by a trimer of isophorone diisocyanate.
23. The electron-beam curable polyurethane resin for a magnetic
recording medium of claim 21, wherein the isocyanurate is delivered
by an alcohol having at least one acrylic double bond.
24. A magnetic recording medium comprising the electron-beam
curable polyurethane resin of claim 21.
25. The magnetic recording medium of claim 24, further comprising a
non-magnetic substrate provided with a layer containing the
electron-beam curable polyurethane resin.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electron-beam curable
polyurethane resin for magnetic recording media (hereinafter
referred to as an electron-beam curable resin in some cases), to a
method for producing the same, and to a magnetic recording medium
using the same. More specifically, the present invention relates to
an electron-beam curable polyurethane resin having excellent
crosslinking characteristics and which is suitably used for
magnetic recording media, to a method for producing the
electron-beam curable polyurethane resin having excellent
crosslinking characteristics by electron-beam sensitive
modification of a common thermosetting polyurethane resin, and to a
magnetic recording medium using the electron-beam curable
polyurethane resin.
[0003] 2. Description of the Related Art
[0004] Resins conventionally used for magnetic recording media
typically include thermosetting resins and electron-beam curable
resins. The thermosetting resins are cured by allowing active
hydrogen in the resins, which is typically the hydroxy group, to
react with an isocyanate compound to form crosslinks in the resins.
On the other hand, the electron-beam curable resins are cured by
introducing an electron-beam sensitive functional group, which is
typically the acrylic double bond, and exposing the resins to an
electron beam to form crosslinks.
[0005] In general, vinyl chloride resins and polyurethane resins
are used as the electron-beam curable resins for magnetic recording
media. For electron-beam sensitive modification of the vinyl
chloride resins, the hydroxy group of a thermosetting vinyl
chloride resin having a hydroxy group may be allowed to react with
a tolylene diisocyanate (TDI) adduct produced by a reaction between
TDI and 2-hydroxyethyl methacrylate (2-HEMA) (disclosed in Japanese
Examined Patent Application Publication No. 1-25141), allowed to
react with a cyclic anhydride and further react with an epoxy
monomer having an acrylic double bond (disclosed in Japanese Patent
No. 2514682), or allowed to react with
2-isocyanateethyl(meth)acrylate (MOI) (disclosed in Japanese
Unexamined Patent Application Publication NO. 4-67314).
[0006] On the other hand, in the case of using the polyurethane
resins, typically, a (meth)acrylate compound having a hydroxy group
in the molecule thereof may be used as part of the material for
synthesizing polyurethane to produce a radiation curable
polyurethane resin (disclosed in Japanese Patent No. 2610468), or a
polyurethane whose polymer end is a isocyanate group may be
prepared and subsequently allowed to react with an alcohol having
an acrylic double bond (disclosed in Japanese Examined Patent
Application Publication No. 3-1727).
[0007] As for the electron-beam curable polyurethane resins, if an
acrylic double bond can be introduced to the active hydrogen, which
is typically the hydroxy group, of a known thermosetting
polyurethane resin, in the same manner as in the vinyl chloride
resins, commercially available polyurethane resins can be modified
to be electron-beam sensitive.
[0008] The thermosetting polyurethane resin however has a smaller
amount of active hydrogen in the molecule thereof than that of
thermosetting vinyl chloride resins. Hence, when the modification
is performed by the same technique as in the vinyl chloride resins,
only a small number of acrylic double bonds can be introduced and,
consequently, crosslinking of the coating film cured by
electron-beam is disadvantageously insufficient.
SUMMARY OF THE INVENTION
[0009] Accordingly, an object of the present invention is to
provide an electron-beam curable polyurethane resin having
excellent crosslinking characteristics and which is suitably used
for magnetic recording media, by electron-beam sensitive
modification of a known thermosetting polyurethane resin, to
provide a method for easily producing the electron-beam curable
polyurethane resin having excellent crosslinking characteristics,
from a known thermosetting polyurethane resin, and to provide a
high-performance magnetic recording medium by using the
electron-beam curable polyurethane resin.
[0010] The inventors of the present invention have conducted
intensive research to overcome the above-described challenges.
Consequently, they have found that an electron-beam curable
polyurethane resin having excellent crosslinking characteristics
can be produced by using a known polyurethane resin as the raw
material and modifying it with a compound having at least two
acrylic double bonds, and thus, accomplished the present
invention.
[0011] Specifically, the electron-beam curable polyurethane resin
for magnetic recording media, a method for producing the same, and
a magnetic recording medium using the same are as follows.
[0012] (1) The electron-beam curable polyurethane resin for
magnetic media is produced by modifying a polyurethane resin having
recording active hydrogen in the molecule thereof with a compound
having at least two acrylic double bonds, wherein the modification
is performed on the active hydrogen so that the polyurethane resin
becomes electron-beam curable.
[0013] (2) To produce the electron-beam curable polyurethane resin
for magnetic recording media described in (1), in the method for
producing the electron-beam curable polyurethane resin for magnetic
recording media, the active hydrogen of a polyurethane resin having
active hydrogen in the molecule thereof is allowed to react with a
compound having at least two acrylic double bonds and an isocyanate
group in the molecule thereof, thereby being modified to be
electron-beam curable.
[0014] (3) In the method described in (2), the compound is prepared
by allowing an isocyanurate to react with an alcohol having at
least one acrylic double bond in the molecule thereof.
[0015] (4) The magnetic recording medium comprises a non-magnetic
substrate provided with a layer containing the electron-beam
curable polyurethane resin for magnetic recording media described
in (1).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] The embodiments of the present invention will now be
illustrated in detail.
[0017] The electron-beam curable polyurethane resin for magnetic
recording media of the present invention is produced by
electron-beam sensitive modification of a predetermined
polyurethane resin, used as the raw material, using a predetermined
compound (hereinafter referred to as a "modifying compound").
[0018] The raw material polyurethane resin used in the present
invention may be a known (general-purpose) polyurethane resin or a
newly developed polyurethane resin. However, the polyurethane resin
must have active hydrogen, such as the hydroxy group, primary
amine, or secondary amine, in the molecule thereof in order to
carry out reaction.
[0019] Such polyurethane resins are not particularly limited, but
include, for example, Estane 5776P, 5788P, and 5799P (produced by
BF Goodrich Co.); UR8200, UR8300, and UR8700 (produced by Toyobo
Co., Ltd); and N-2301, N-2304, N-3167, N-3301, N-4325, and TK501K
(produced by Nippon Polyurethane Industry Co., Ltd.).
[0020] As the modifying compound allowed to react with the active
hydrogen of these polyurethane resins in order to carry out
electron-beam sensitive modification, a compound is used which has
both at least two acrylic double bonds and an isocyanate group in
the molecule thereof. This modifying compound can be prepared by,
for example, allowing two of the three isocyanate groups in a
hexamethylene diisocyanate (HDI) trimer (isocyanurate) to react
with a compound having both a hydroxy group and an acrylic double
bond so as to have two acrylic double bonds and one isocyanate
group. The resulting modifying compound is allowed to react with,
for example, the hydroxy group of a polyurethane resin. Thus, two
acrylic double bonds can be introduced for one hydroxy group of the
polyurethane resin.
[0021] The isocyanurate is not particularly limited, and other
isocyanurates, such as of tolylene diisocyanate (TDI) and
isophorone diisocyanate (IPDI) may be used instead of HDI. The
compound allowed to react with the isocyanurate nurato, having both
a hydroxy group and at least one acrylic double bond, that is, an
alcohol having at least one acrylic double bond in the molecule
thereof, is not particularly limited, and exemplary compounds
include 2-hydroxyethyl acrylate (2-HEA), 2-hydroxyethyl
methacrylate (2-HEMA), 2-hydroxypropyl acrylate, hydroxydiethylene
glycol methacrylate, butoxyhydroxypropyl acrylate,
phenoxyhydroxypropyl acrylate, hydroxypropyl dimethacrylate,
glycerol dimethacrylate, and monohydroxypentaerythritol
triacrylate.
[0022] Synthesis of the electron-beam curable polyurethane resin is
performed as described above, through a reaction of urethane
formation between three compounds consisting of the isocyanurate,
the alcohol having at least one acrylic double bond in the molecule
thereof, and the polyurethane resin having active hydrogen. As for
the method for the synthesis, preferably, the isocyanurate and the
alcohol having at least one acrylic double bond in the molecule
thereof are precedently allowed to react with each other to prepare
the above-described modifying compound, and then the polyurethane
resin having active hydrogen is allowed to react.
[0023] In general, a catalyst for urethane formation, such as
dibutyltin dilaurate or tin octylate is preferably used in an
amount of 0.005 to 0.1 part by weight relative to 100 parts by
weight in total of reactants, In the synthesis. However, the
catalyst for urethane formation is not always necessary. The
synthesis reaction temperature is preferably 30 to 80.degree. C.,
and more preferably 50 to 70.degree. C.
[0024] The resulting electron-beam curable polyurethane resin can
be used as a binder of a resin undercoat layer, an undercoat layer
containing an inorganic pigment, a backcoat layer, and a magnetic
layer, in a magnetic recording medium. Hereinafter, these layers
are collectively referred to as "functional layers". The
electron-beam curable polyurethane resin may be used singly or in
combination with other resins such as vinyl chloride resins.
[0025] Crosslinking of the electron-beam curable polyurethane resin
is performed with an electron-beam preferably at an exposure dose
of 1 to 10 Mrad, and more preferably 3 to 7 Mrad. The exposure
energy (acceleration voltage) is preferably 100 kV or more.
[0026] In the present invention, by using the above-described
electron-beam curable polyurethane resin as a binder of the
functional layers, a high-performance magnetic recording medium can
be obtained which includes highly crosslinked, highly
solvent-resistant functional layers. The magnetic recording medium
of the present invention needs to have a layer containing the
electron-beam curable polyurethane resin of the present invention
on a non-magnetic substrate. However, the other construction
materials and additives are not particularly limited, and the
following materials may be used.
[0027] The material of the non-magnetic substrate may appropriately
be selected from known resin films, such as polyester, polyamide,
and aromatic polyamide, and laminates of these resin films. The
thickness of the substrate is in a known range, and is also not
particularly limited.
[0028] The ferromagnetic powder used for the magnetic layer is
acicular ferromagnetic metallic powder having a mean long-axis
length of preferably 0.15 .mu.m or less, and more preferably 0.05
to 0.10 .mu.m. If the mean long-axis length is more than 0.15
.mu.m, electromagnetic conversion characteristics (particularly S/N
and C/N ratios) required for magnetic recording media tend not to
be satisfied. Alternatively, a hexagonal iron oxide powder, such as
barium ferrite, may be used. The platy ratio of the hexagonal iron
oxide powder is preferably 2 to 7. Also, the mean primary plate
diameter is preferably 10 to 50 nm when observed by TEM. If it is
large, the surface of the magnetic layer tends to deteriorate.
[0029] It is sufficient that the magnetic layer composition
contains 70 to 90 percent by weight of such ferromagnetic powder.
An excessively high content of the ferromagnetic powder results in
a low content of the binder, and consequently the surface
smoothness by calendaring is liable to deteriorate. In contrast, an
excessively low content of the ferromagnetic powder tends not to
provide a high reproduction output.
[0030] Preferred binder resins for the magnetic layer include the
electron-beam curable polyurethane resin of the present invention,
known thermoplastic resins and thermosetting resins, other
radiation curable resins, and their mixtures, but are not
particularly limited to these. Also, a mixture of the electron-beam
curable polyurethane resin of the present invention and other
binder resins may be used.
[0031] The content of the binder resin used for the magnetic layer
is 5 to 40 parts by weight relative to 100 parts by weight of the
ferromagnetic powder, and a content of 10 to 30 parts by weight is
particularly preferable. An excessively low content of the binder
resin degrades the strength of the magnetic layer and consequently
the running durability tents to deteriorate. In contrast, an
excessively high content results in a reduced content of the
ferromagnetic metallic powder content, consequently degrading
electromagnetic conversion characteristics.
[0032] Cross-linkers for curing the binder resin include known
various types of polyisocyanate, and the cross-linker content is
preferably 10 to 30 parts by weight relative to 100 parts by weight
of the binder resin. The magnetic layer may also contain an
abrasive, a dispersant such as a surfactant, a higher fatty acid,
and other additives, if necessary.
[0033] A paint for magnetic layer formation is prepared by adding
an organic solvent to the above-described ingredients. The organic
solvent is not particularly limited, and may be at least one
appropriately selected from among various solvents including
ketones, such as methyl ethyl ketone (MEK), methyl isobutyl ketone,
and cyclohexanone, and aromatic solvents, such as toluene. The
organic solvent content is about 100 to 900 parts by weight
relative to 100 parts by weight in total of solids (the
ferromagnetic metallic powder, various types of inorganic grains,
and the like) and the binder resin.
[0034] The thickness of the magnetic layer, in the present
invention, is 0.50 .mu.m or less, preferably 0.01 to 0.50 .mu.m,
and more preferably 0.02 to 0.30 .mu.m. An excessively large
thickness leads to an increased self-demagnetization loss and
thickness loss.
[0035] A non-magnetic layer serving as the undercoat layer may be
disposed between the magnetic layer and the non-magnetic substrate,
thereby improving electromagnetic conversion characteristics of the
magnetic layer having a reduced thickness. Thus, reliability is
further increased.
[0036] Various types of inorganic powder can be used as the
non-magnetic powder for the non-magnetic layer, and preferred
inorganic powders include acicular nonmagnetic powders, such as
acicular non-magnetic iron oxide (.alpha.-Fe.sub.2O.sub.3). The
non-magnetic layer may further contain various types of
non-magnetic powder, such as calcium carbonate (CaCO.sub.3),
titanium oxide (TiO.sub.2), barium sulfate (BaSO4), and
.alpha.-alumina (.alpha.-Al.sub.2O.sub.3), if necessary.
Preferably, the nonmagnetic layer contains carbon black. The carbon
black may be furnace black for rubber, thermal black for rubber,
black for color, acetylene black, and the like.
[0037] The compounding ratio of the carbon black to the inorganic
powder is preferably 100:0 to 10:90 by weight. If the inorganic
powder ratio is more than 90, a problem of surface electric
resistance is liable to occur.
[0038] Exemplary binders for the nonmagnetic layer include the
electron-beam curable polyurethane of the present invention, known
thermoplastic resins and thermosetting resins, other radiation
curable resins, and their mixtures, as In the magnetic layer, and
the radiation curable resins are particularly suitable.
[0039] The non-magnetic layer may further contain a dispersant such
as a surfactant and other additives, if necessary. The paint for
the non-magnetic layer may be prepared by adding the same organic
solvent as in the above-described magnetic layer in a similar
amount.
[0040] The thickness of the non-magnetic layer is preferably 2.5
.mu.m or less, and more preferably 0.1 to 2.3 .mu.m. Even if the
thickness is increased to more than 2.5 .mu.m, performance is not
enhanced. On the contrary, strict conditions are required for
coating because the thickness of the coating is liable to become
nonuniform, and the surface smoothness is also liable to
deteriorate.
[0041] The backcoat layer is intended to enhance the running
stability and to prevent electrification of the magnetic layer, and
is provided if required. Preferably, the backcoat layer contains 30
to 80 percent by weight of carbon black. As the carbon black, any
type can be used as long as it is generally used, and the same
carbon black as in the above-described non-magnetic layer may be
used. In addition to the carbon black, the backcoat layer may
further contain various types of non-magnetic, inorganic powder
used for the magnetic layer, such as an abrasive; a dispersant such
as a surfactant; a higher fatty acid; a fatty ester; a lubricant,
such as silicone oil, and other various types of additives.
[0042] The thickness (after calendaring) of the backcoat layer is
0.1 to 1.0 .mu.m, and preferably 0.2 to 0.8 .mu.m. If the thickness
is more than 1.0 .mu.m, the friction between a medium-sliding path
and the medium becomes excessively large, and consequently the
running stability tends to deteriorate. In contrast, in the case of
a thickness of less than 0.1 .mu.m, the coating of the backcoat
layer is liable to be shaved off while the medium is running.
[0043] As described above, according to the present invention, an
electron beam curable polyurethane resin for magnetic recording
media can be produced using a known polyurethane resin having
active hydrogen as the raw material. The resulting electron-beam
curable polyurethane resin has excellent crosslinking
characteristics, and thus a high-performance recording magnetic
medium can be provided.
EXAMPLES
[0044] The present invention will further be described in detail
using examples. However, the examples do not limit the present
invention. In the following description, "part(s)" refers to
"part(s) by weight".
Synthesis Example 1
Polyurethane Acrylate Resin (1)
[0045] A one litter, three-neck flask was charged with 504 parts of
HDI nurate, 0.18 part of dibutyltin dilaurate, and 0.22 part of
2,6-tert-butyl-4-methylphenol (BHT), and 232 parts of
2-hydroxyethyl acrylate was dripped while temperature was
controlled to 60.degree. C. After dripping, the sample was stirred
at 60.degree. C. for 2 hours and taken out. Thus, HDI nurate-2-HEA
adduct (modifying compound) was obtained.
[0046] Next, 262 parts of Estane 5778P produced by BP Goodrich Co.,
700 parts of methyl ethyl ketone (MEK), 0.5 part of dibutyltin
dilaurate, and 0.05 part of 2,6-tert-butyl-4-methylphenol (BHT)
were compounded and stirred at 70.degree. C. for 3 hours. Then, 38
parts of the previously prepared HDI nurate-2-HEA adduct (modifying
compound) was added. After stirring at 70.degree. C. for 15 hours,
it was made sure that the isocyanate characteristic absorption peak
(2270 cm.sup.-1) had disappeared in the IR spectrum, and then the
sample was taken out. Thus, polyurethane acrylate resin (1) was
obtained.
Synthesis Example 2
Polyurethane Acrylate Resin (2)
[0047] A one litter, three-neck flask was charged with 504 parts of
HDI nurate, 0.18 part of dibutyltin dilaurate, and 0.22 part of
2,6-tert-butyl-4-methylphenol (BHT), and 260 parts of
2-hydroxyethyl methacrylate (2-HEMA) was dripped while temperature
was controlled to 60.degree. C. After dripping, the sample was
stirred at 60.degree. C. for 2 hours and taken out. Thus, HDI
nurate-2-HEMA adduct (modifying compound) was obtained.
[0048] Next, 262 parts of Estane 5778P produced by BF Goodrich Co.,
700 parts of MEK, 0.5 part of dibutyltin dilaurate, and 0.05 part
of 2,6-tert-butyl-4-methylphenol (BHT) were compounded and stirred
at 70.degree. C. for 3 hours. Then, 40 parts of the previously
prepared HDI nurate-2-HEMA adduct (modifying compound) was added.
After stirring at 70.degree. C. for 15 hours, it was made sure that
the isocyanate characteristic absorption peak (2270 cm.sup.-1) had
disappeared in the IR spectrum, and then the sample was taken out.
Thus,
Synthesis Example 3
Polyurethane Acrylate Resin (3)
[0049] A one litter, three-neck flask was charged with 504 parts of
HDI nurate, 0.18 part of dibutyltin dilaurate, and 0.22 part of
2,6-tert-butyl-4-methylphenol, and 496 parts of
monohydroxypentaerythritol triacrylate was dropped while
temperature was controlled to 60.degree. C. After dripping, the
sample was stirred at 60.degree. C. for 2 hours and taken out.
Thus, HDI nurate-monohydroxypentaerythritol triacrylate adduct
(modifying compound) was obtained.
[0050] Next, 230 parts of Estane 5778P produced by BF Goodrich Co.,
615 parts of MEK, 0.5 part of dibutyltin dilaurate, and 0.05 part
of 2,6-tert-butyl-4-methylphenol (BHT) were compounded and stirred
at 70.degree. C. for 3 hours. Then, 53 parts of the previously
prepared HDI nurate-monohydroxypentaerythritol triacrylate adduct
(modifying compound) was added. After stirring at 70.degree. C. for
15 hours, it was made sure that the isocyanate characteristic
absorption peak (2270 cm.sup.-1) had disappeared in the IR
spectrum, and then the sample was taken out. Thus, polyurethane
acrylate resin (3) was obtained.
Synthesis Example 4
Polyurethane Acrylate Resin (4)
[0051] A one litter, three-neck flask was charged with 333 parts of
IPDI nurate, 450 parts of MEK, 0.44 part of dibutyltin dilaurate,
and 0.27 part of 2,6-tert-butyl-4-methylphenol (BHT), and 116 parts
of 2-hydroxyethyl acrylate (2-HEA) was dripped while temperature
was controlled to 60.degree. C. After dripping, the sample was
stirred at 60.degree. C. for 5 hours and taken out. Thus, IPDI
nurate-2-HEA adduct (modifying compound) was obtained.
[0052] Next, 254 parts of Estane 5778P produced by BF Goodrich Co.,
654 parts of MEK, 0.5 part of dibutyltin dilaurate, and 0.05 part
of 2,6-tert-butyl-4-methylphenol (BHT) were compounded and stirred
at 70.degree. C. for 3 hours. Then, 92 parts of the previously
prepared TPDT nutrate-2-HEA adduct (modifying compound) was added.
After stirring at 70.degree. C. for 15 hours, it was made sure that
the isocyanate characteristic absorption peak (2270 cm.sup.-1) had
disappeared in the IR spectrum, and then the sample was taken out.
Thus, polyurethane acrylate resin (4) was obtained.
Synthesis Example 5
Polyurethane Acrylate Resin (5)
[0053] In a one litter, three-neck flask, 833 parts of Vylon UR8300
produced by Toyobo Co., Ltd., 0.5 part of dibutyltin dilaurate, and
0.05 part of 2,6-tert-butyl-4-methylphenol (BHT) were placed and
stirred at 70.degree. C. for 1 hours. Then, 13 parts of the
previously prepared HDI nurate-2-HEA adduct (modifying compound)
was added. After stirring at 70.degree. C. for 15 hours, it was
made sure that the isocyanate characteristic absorption peak (2270
cm.sup.-1) had disappeared in the IR spectrum, and then the sample
was taken out. Thus, polyurethane acrylate resin (5) was
obtained.
Synthesis Example 6
Polyurethane Acrylate Resin (6)
[0054] In a one litter, three-neck flask, 230 parts of Estane 5778P
produced by BF Goodrich Co., 520 parts of MEK, 0.5 part of
dibutyltin dilaurate, and 0.3 part of hydroquinone were placed and
stirred at 70.degree. C. for 3 hours. Then, 8 parts of
2-isocyanateethyl methacrylate was added. After stirring at
70.degree. C. for 15 hours, it was made sure that the isocyanate
characteristic absorption peak (2270 cm.sup.-1) had disappeared in
the IR spectrum, and then the sample was taken out. Thus,
polyurethane acrylate resin (6) was obtained.
Synthesis Example 7
Polyurethane Acrylate Resin (7)
[0055] A one litter, three-neck flask was charged with 348 parts of
tolylene diisocyanate (TDI) and heated to 80.degree. C. Then, 260
parts of 2-hydroxyethyl methacrylate (2-HEMA), 0.07 part of tin
octylate, and 0.05 part of hydroquinone were dripped while
temperature was controlled to 80.degree. C. After dripping, the
sample was stirred at 80.degree. C. for 3 hours and taken out.
Thus, TDI-2-HEMA adduct was obtained.
[0056] Next, 226 parts of Estane 5778P produced by BF Goodrich Co.,
560 parts of MEK, 0.5 part of dibutyltin dilaurate, and 0.05 part
of 2,6-tert-butyl-4-methylphenol (BHT) were compounded and stirred
at 80.degree. C. for 3 hours. Then, 14 parts of the previously
prepared TDI-2-HEMA adduct was added. After stirring at 80.degree.
C. for 15 hours, it was made sure that the isocyanate
characteristic absorption peak (2270 cm.sup.-1) had disappeared in
the IR spectrum, and then the sample was taken out. Thus,
polyurethane acrylate resin (7) was obtained.
Synthesis Example 8
Polyurethane Acrylate Resin (8)
[0057] In a one litter, three-neck flask, 200 parts of Estane 5778P
produced by BF Goodrich Co. and 525 parts of MEK were placed and
stirred at 80.degree. C. for 3 hours. Then, 6 parts of
1,2-cyclohexanedicarboxylic anhydride was added and allowed to
react at 80.degree. C. until the anhydride characteristic
absorption peaks (1790 cm.sup.-1 and 1870 cm.sup.-1) disappeared.
Furthermore, 12 parts of 1,2-cyclohexanedicarboxylic anhydride, 17
parts of glycidyl methacrylate, 0.02 part of hydroquinone, and 0.1
part of triethanolamine were slowly added and stirred at 80.degree.
C. for 20 hours. Then, it was made sure that the acid value was 4
or less, and the sample was taken out to obtain polyurethane
acrylate resin (8).
Example 1
Evaluation 1: Evaluation of Crosslinking Characteristics
[0058] A coating of polyurethane acrylate resin (1) was formed to a
thickness of 30 .mu.m on a separation film, and was then exposed to
an electron beam of 6 Mrad under the condition of an acceleration
voltage of 200 kV to be cured. Next, the polyurethane resin coating
film cured with electron beam was removed from the separation film,
and the gel fraction was measure under the following
conditions.
<Gel Fraction Measurement Conditions>
Solvent: methyl ethyl ketone (MEK)
Extraction condition: boiling in MEK
Extraction time: 5 hours
[0059] Extraction was performed under the conditions above. The
polyurethane resin coating film was weighed before and after the
extraction, and the gel fraction was calculated from the difference
between the obtained weights.
Evaluation 2: Evaluation of Crosslinking Characteristics of Coating
Films Containing Pigment or Magnetic Powder
[0060] For three types of coating, a magnetic metallic powder
(magnetic paint), an .alpha.-iron oxide/carbon black mixture
(non-magnetic paint), and a carbon black (carbon black paint) were
each dispersed in polyurethane acrylate resin (1), and crosslinks
were formed. Solvent resistances of these samples were evaluated to
estimate crosslinking characteristics.
(1) Evaluation of Magnetic Metallic Powder
[0061] Preparation of Magnetic Paint Sample TABLE-US-00001 Magnetic
metallic powder 100 parts by weight (Fe/Co/Al/Y = 100/10/5.2/2.0
(by weight): (Hc = 144.6 kA/m (1830 Oe), .sigma.s = 130
Am.sup.2/kg, BET = 57 m.sup.2/g, mean long-axis length = 0.10
.mu.m) Polyurethane acrylate resin (1): 70 parts by weight MEK: 70
parts by weight Toluene: 120 parts by weight Cyclohexanone: 70
parts by weight
[0062] After being mixed and kneaded, these ingredients were
dispersed with a sand grinder mill to prepare a magnetic paint.
[0063] Next, the resulting magnetic paint was applied on a
polyethylene terephthalate (PET) film having a thickness of 6.1
.mu.m so as to result in a dried thickness of 1.5 .mu.m. After
drying at a temperature of 100.degree. C. calendaring was performed
at a linear pressure of 2.9.times.10.sup.5 N/m and a temperature of
90.degree. C. and subsequently electron beam (EB) exposure (6 Mrad)
was performed. Thus, a cured magnetic coating film was
prepared.
(2) Evaluation of .alpha.-Iron Oxide/Carbon Black Pigment
Mixture
[0064] Preparation of Non-Magnetic Paint Sample TABLE-US-00002
Non-magnetic powder: acicular .alpha.-Fe.sub.2O.sub.3: 80 parts by
weight (mean short-axis diameter: 18 nm, aspect ratio: 6.1, pH:
8.9) Carbon black (#850B produced by Mitsubishi 20 parts by weight
Chemical Co.): (mean particle size: 16 nm, BET: 200 m.sup.2/g, DBP
oil absorption: 70 mL/100 g) Polyurethane acrylate resin (1): 70
parts by weight MEK: 120 parts by weight Toluene: 120 parts by
weight Cyclohexanone: 70 parts by weight
[0065] After being mixed and kneaded, these ingredients were
dispersed with a sand grinder mill to prepare a non-magnetic
paint.
[0066] Next, the resulting non-magnetic paint was applied on a PET
film having a thickness of 6.1 .mu.m so as to result in a dried
thickness of 1.5 .mu.m. After drying at a temperature of
100.degree. C., calendaring was performed at a linear pressure of
2.9.times.10.sup.5 N/m and a temperature of 90.degree. C. and
subsequently EB exposure (6 Mrad) was performed. Thus, a cured
non-magnetic coating film was prepared.
(3) Evaluation of Carbon Black Type
[0067] Preparation of Carbon Black Paint Sample TABLE-US-00003
Carbon black: 100 parts by weight (Conductex SC produced by
Columbian Carbon Co., mean particle size: 20 nm, BET: 220
m.sup.2/g) Carbon black: 1 part by weight (Sevacarb MT produced by
Columbian Carbon Co., mean particle size: 350 nm, BET: 8 m.sup.2/g)
Polyurethane acrylate resin (1): 330 parts by weight MEK: 350 parts
by weight Toluene: 350 parts by weight Cyclohexanone: 170 parts by
weight
[0068] After being mixed and kneaded, these ingredients were
dispersed with a sand grinder mill.
[0069] Next, the resulting carbon black paint was applied on a PET
film having a thickness of 6.1 .mu.m so as to result in a dried
thickness of 1.5 .mu.m. After drying at a temperature of
100.degree. C., calendaring was performed at a linear pressure of
2.9.times.10.sup.5 N/m and a temperature of 70.degree. C. and
subsequently EB exposure (6 Mrad) was performed. Thus, a cured
carbon black coating film was prepared.
[0070] The solvent resistances of the film samples prepared in the
above-described manner were evaluated according to the following
procedure and criteria.
1. A cotton swab impregnated with MEK was used.
2. The surfaces of the films were rubbed with the cotton swab.
3. It was counted how many times of rubbing were performed before
the film disappeared.
4. 10 times or more: good
[0071] 5 to 10 times: fair
[0072] 1 to 5 times: bad
Example 2
[0073] Coating film samples were prepared and the gel fractions and
solvent resistances were evaluated, in an identical manner to
Example 1 except that polyurethane acrylate resin (2) was used
instead of polyurethane acrylate resin (1) used in Example 1.
Example 3
[0074] Coating film samples were prepared and the gel fractions and
solvent resistances were evaluated, in an identical manner to
Example 1 except that polyurethane acrylate resin (3) was used
instead of polyurethane acrylate resin (1) used in Example 1.
Example 4
[0075] Coating film samples were prepared and the gel fractions and
solvent resistances were evaluated, in an identical manner to
Example 1 except that polyurethane acrylate resin (4) was used
instead of polyurethane acrylate resin (1) used in Example 1.
Example 5
[0076] Coating film samples were prepared and the gel fractions and
solvent resistances were evaluated, in an identical manner to
Example 1 except that polyurethane acrylate resin (5) was used
instead of polyurethane acrylate resin (1) used in Example 1.
Comparative Example 1
[0077] Coating film samples were prepared and the gel fractions and
solvent resistances were evaluated, in an identical manner to
Example 1 except that polyurethane acrylate resin (6) was used
instead of polyurethane acrylate resin (1) used in Example 1.
Comparative Example 2
[0078] Coating film samples were prepared and the gel fractions and
solvent resistances were evaluated, in an identical manner to
Example 1 except that polyurethane acrylate resin (7) was used
Instead of polyurethane acrylate resin (1) used in Example 1.
Comparative Example 3
[0079] Coating film samples were prepared and the gel fractions and
solvent resistances were evaluated, in an identical manner to
Example 1 except that polyurethane acrylate resin (8) was used
instead of polyurethane acrylate resin (1) used in Example 1.
Comparative Example 4
[0080] In 700 g of MEK, 300 g of Estane 5778P produced by BF
Goodrich Co. was dissolved to prepare a polyurethane resin
solution. Coating film samples were prepared and the gel fractions
and solvent resistances were evaluated, in an identical manner to
Example 1 except that this polyurethane resin solution was used
instead of polyurethane acrylate resin (1) used in Example 1.
TABLE-US-00004 TABLE 1 Solvent resistance Non- Carbon Gel Magnetic
magnetic black fraction coating coating coating Resin (%) film film
film Example 1 Polyurethane 96 Good Good Good acrylate resin (1)
Example 2 Polyurethane 95 Good Good Good acrylate resin (2) Example
3 Polyurethane 98 Good Good Good acrylate resin (3) Example 4
Polyurethane 96 Good Good Good acrylate resin (4) Example 5
Polyurethane 85 Good- Good- Good- acrylate resin Fair Fair Fair (5)
Comparative Polyurethane 20 Bad Bad Bad Example 1 acrylate resin
(6) Comparative Polyurethane 5 Bad Bad Bad Example 2 acrylate resin
(7) Comparative Polyurethane 5 Bad Bad Bad Example 3 acrylate resin
(8) Comparative Polyurethane 0 Bad Bad Bad Example 4 resin
solution
[0081] According to the results shown in Table 1 above it has been
shown that the polyurethane resins of the examples produced by
modifying a polyurethane resin having active hydrogen with a
compound having two or more of acrylic double bonds and an
isocyanate group in the molecule thereof have more excellent
crosslinking characteristics than those of the known polyurethane
resin used in the comparative examples and can result in cured
coating films having better solvent resistance to a magnetic paint,
a non-magnetic paint, and a black carbon paint.
* * * * *